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Patel KB, Williams JV, Baxter EM, Chengot P, Parmar JD. Surgical management of advanced pleomorphic dermal sarcoma of the occipital scalp. Ann R Coll Surg Engl 2021; 104:e9-e11. [PMID: 34730407 DOI: 10.1308/rcsann.2021.0052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pleomorphic dermal sarcoma is a rare neoplasm of mesenchymal origin that most commonly affects the head. We describe the presentation of a 61-year-old man with a 10-week history of an exophytic lesion affecting the occipital scalp, demonstrating rapid growth. The final histopathology revealed a completely excised 9cm pleomorphic dermal sarcoma (pT2aN0M0, Stage 3), one of the largest such lesions reported in the literature to date. This patient's management involved a wide local subperiosteal excision onto the cranium, with a reconstruction with an Integra dermal regeneration template (Integra LifeSciences, Princeton, NJ, USA) and healing with secondary intention. This was mainly due to poorly defined clinical margins on primary excision, the potential for further excision of involved margins (later confirmed as not needed) and the patient's comorbidities, making a return to theatre for definitive reconstruction undesirable.
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Affiliation(s)
- K B Patel
- Leeds Teaching Hospitals NHS Trust, UK
| | | | | | - P Chengot
- Leeds Teaching Hospitals NHS Trust, UK
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Patel KB, Kononova O, Cai S, Barsegov V, Parmar VS, Kumar R, Singh BR. Botulinum neurotoxin inhibitor binding dynamics and kinetics relevant for drug design. Biochim Biophys Acta Gen Subj 2021; 1865:129933. [PMID: 34023445 DOI: 10.1016/j.bbagen.2021.129933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/05/2021] [Accepted: 05/17/2021] [Indexed: 02/06/2023]
Abstract
BACKGROUND A natural product analog, 3-(4-nitrophenyl)-7H-furo[3,2-g]chromen-7-one, which is a nitrophenyl psoralen (NPP) was found to be an effective inhibitor of botulinum neurotoxin type A (BoNT/A). METHODS In this work, we performed enzyme inhibition kinetics and employed biochemical techniques such as isothermal calorimetry (ITC) and fluorescence spectroscopy as well as molecular modeling to examine the kinetics and binding mechanism of NPP inhibitor with BoNT/A LC. RESULTS Studies of inhibition mechanism and binding dynamics of NPP to BoNT/A light chain (BoNT/A LC) showed that NPP is a mixed type inhibitor for the zinc endopeptidase activity, implying that at least part of the inhibitor-enzyme binding site may be different from the substrate-enzyme binding site. By using biochemical techniques, we demonstrated NPP forms a stable complex with BoNT/A LC. These observations were confirmed by Molecular Dynamics (MD) simulation, which demonstrates that NPP binds to the site near the active site. CONCLUSION The NPP binding interferes with BoNT/A LC binding to the SNAP-25, hence, inhibits its cleavage. Based on these results, we propose a modified strategy for designing a molecule to enhance the efficiency of the inhibition against the neurotoxic effect of BoNT. GENERAL SIGNIFICANCE Insights into the interactions of NPP with BoNT/A LC using biochemical and computational approaches will aid in the future development of effective countermeasures and better pharmacological strategies against botulism.
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Affiliation(s)
- Kruti B Patel
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA
| | - Olga Kononova
- Department of Chemistry and Biochemistry, University of Massachusetts Lowell, Lowell, MA, USA
| | - Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA
| | - Valeri Barsegov
- Department of Chemistry and Biochemistry, University of Massachusetts Lowell, Lowell, MA, USA
| | - Virinder S Parmar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi, India
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA; Prime Bio Inc., Dartmouth, MA, USA.
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Kumar R, Feltrup TM, Kukreja RV, Patel KB, Cai S, Singh BR. Evolutionary Features in the Structure and Function of Bacterial Toxins. Toxins (Basel) 2019; 11:toxins11010015. [PMID: 30609803 PMCID: PMC6356308 DOI: 10.3390/toxins11010015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 12/24/2018] [Accepted: 12/25/2018] [Indexed: 12/21/2022] Open
Abstract
Toxins can function both as a harmful and therapeutic molecule, depending on their concentrations. The diversity in their function allows us to ask some very pertinent questions related to their origin and roles: (a) What makes them such effective molecules? (b) Are there evolutionary features encoded within the structures of the toxins for their function? (c) Is structural hierarchy in the toxins important for maintaining their structure and function? (d) Do protein dynamics play a role in the function of toxins? and (e) Do the evolutionary connections to these unique features and functions provide the fundamental points in driving evolution? In light of the growing evidence in structural biology, it would be appropriate to suggest that protein dynamics and flexibility play a much bigger role in the function of the toxin than the structure itself. Discovery of IDPs (intrinsically disorder proteins), multifunctionality, and the concept of native aggregation are shaking the paradigm of the requirement of a fixed three-dimensional structure for the protein’s function. Growing evidence supporting the above concepts allow us to redesign the structure-function aspects of the protein molecules. An evolutionary model is necessary and needs to be developed to study these important aspects. The criteria for a well-defined model would be: (a) diversity in structure and function, (b) unique functionality, and (c) must belong to a family to define the evolutionary relationships. All these characteristics are largely fulfilled by bacterial toxins. Bacterial toxins are diverse and widely distributed in all three forms of life (Bacteria, Archaea and Eukaryotes). Some of the unique characteristics include structural folding, sequence and functional combination of domains, targeting a cellular process to execute their function, and most importantly their flexibility and dynamics. In this work, we summarize certain unique aspects of bacterial toxins, including role of structure in defining toxin function, uniqueness in their enzymatic function, and interaction with their substrates and other proteins. Finally, we have discussed the evolutionary aspects of toxins in detail, which will help us rethink the current evolutionary theories. A careful study, and appropriate interpretations, will provide answers to several questions related to the structure-function relationship of proteins, in general. Additionally, this will also allow us to refine the current evolution theories.
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Affiliation(s)
- Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
| | - Thomas M Feltrup
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
| | - Roshan V Kukreja
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
| | - Kruti B Patel
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
| | - Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, MA 02747, USA.
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
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Bhadarka HK, Patel NH, Patel NH, Patel M, Patel KB, Sodagar NR, Phatak AG, Patel JS. Impact of embryo co-culture with cumulus cells on pregnancy & implantation rate in patients undergoing in vitro fertilization using donor oocyte. Indian J Med Res 2018; 146:341-345. [PMID: 29355140 PMCID: PMC5793468 DOI: 10.4103/ijmr.ijmr_1702_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background & objectives: Cumulus cell co-culture of embryo had been found to be beneficial for achieving better pregnancy and implantation rate (IR). The present study was aimed to evaluate efficiency of cumulus co-culture technique over simple culture of embryo in terms of pregnancy rate (PR) and IR in patients undergoing treatment for infertility using donor oocytes fertilized by intracytoplasmic sperm injection. Methods: This was a quasi-experimental study between control and study groups. The primary endpoint was achievement of pregnancy. Control group included 508 women who underwent embryo development without cumulus cell co-culture and study group included 394 women who underwent embryo development with cumulus cell co-culture using donor's cumulus cells. Results: The present study demonstrated a significant increase in the IR (37.2 vs 24.2%, P<0.001) and in PR (45.7 vs 37.8%, P<0.05) in study group than in control group. The PR and IR were found to be higher in study group, among all groups of women, grouped on the basis of different indications for use of donor oocytes. Interpretation & conclusions: Cumulus cell co-culture technique was found to be more effective than simple culture technique for embryo development in women undergoing treatment for infertility using donor oocytes fertilized by intracytoplasmic sperm injection.
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Affiliation(s)
- Harsha K Bhadarka
- Department of Biochemistry, P.D. Patel Institute of Applied Sciences, Charotar University of Science & Technology, Changa; Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Nayana H Patel
- Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Niket H Patel
- Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Molina Patel
- Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Kruti B Patel
- Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Nilofar R Sodagar
- Department of IVF, Akanksha Hospital & Research Institute, A Unit of Sat Kaival Hospital Pvt. Ltd., Anand, India
| | - Ajay G Phatak
- Central Research Services, Charutar Arogya Mandal, Karamsad, India
| | - Jagdish S Patel
- Department of Biochemistry, P.D. Patel Institute of Applied Sciences, Charotar University of Science & Technology, Changa, India
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Patel KB, Desai KR, Patelk HS. Communication. HIGH PERFORM POLYM 2016. [DOI: 10.1088/0954-0083/9/4/009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Four various poly(urethane-urea)s (PUUs) were prepared by polycondensation of 3-aminophenol with various diisocyanates. The resultant poly(urethane-urea)s were characterized by elemental analyses, IR spectral studies, number average molecular weight ( Mn) estimated by non-aqueous conductometric titration and thermogravimetry. The electrical properties of these polymers have also been measured at room temperature.
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Affiliation(s)
- K B Patel
- Gujarat Narmada Valley Fertilizers Co. Ltd, Narmadanagar - 392 015, Dist. Bharuch, Gujarat, India
| | - K R Desai
- Department of Chemistry, South Gujarat University, Surat, Gujarat, India
| | - H S Patelk
- Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar, Guj, India
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Patel KB, Panchal HP, Karanwal AB, Parekh BB, Shah S, Prasad S. Sunitinib in metastatic renal cell carcinoma: Experience from single center study, efficacy and safety. Indian J Cancer 2016; 53:118-22. [DOI: 10.4103/0019-509x.180844] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Patel NH, Bhadarka HK, Patel KB, Vaniawala SN, Acharya A, Mukhopadhyaya PN, Sodagar NR. Embryo genome profiling by single-cell sequencing for successful preimplantation genetic diagnosis in a family harboring COL4A1 c.1537G>A; p.G513S mutation. J Hum Reprod Sci 2016; 9:200-206. [PMID: 27803589 PMCID: PMC5070403 DOI: 10.4103/0974-1208.192072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
CONTEXT Genetic profiling of embryos (also known as preimplantation genetic diagnosis) before implantation has dramatically enhanced the success quotient of in vitro fertilization (IVF) in recent times. The technology helps in avoiding selective pregnancy termination since the baby is likely to be free of the disease under consideration. AIM Screening of embryos free from c.1537G>A; p.G513S mutation within the COL4A1 gene for which the father was known in before be in heterozygous condition. SUBJECTS AND METHODS Processing of trophectoderm biopsies was done from twelve embryos for c.1537G>A; p.G513S mutation within the COL4A1 gene. DNA extracted from isolated cells were subjected to whole genome amplification using an isothermal amplification and strand displacement technology. Oligonucleotide primers bracketing the mutation were synthesized and used to amplify 162 base pairs (bp) polymerase chain reaction amplicons originating from each embryo which were subsequently sequenced to detect the presence or absence of the single base polymorphism. RESULTS Three out of 12 embryos interrogated in this study were found to be normal while 9 were found to harbor the mutation in heterozygous condition. Implantation of one of the normal embryos following by chorionic villus sampling at 11th week of pregnancy indicated that the baby was free from c.1537G>A; p.G513S mutation within the COL4A1 gene. CONCLUSIONS Single-cell sequencing is a helpful tool for preimplantation embryo profiling. This is the first report from India describing the birth of a normal child through IVF procedure where a potential pathogenic COL4A1 allele was avoided using this technology.
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Affiliation(s)
- Nayana H Patel
- Department of IVF, Akanksha Hospital and Research Institute, Near Shrushti English Medium School, Lambhvel-387310, Anand, Gujarat, India
| | - Harsha K Bhadarka
- Department of IVF, Akanksha Hospital and Research Institute, Near Shrushti English Medium School, Lambhvel-387310, Anand, Gujarat, India
| | - Kruti B Patel
- Department of IVF, Akanksha Hospital and Research Institute, Near Shrushti English Medium School, Lambhvel-387310, Anand, Gujarat, India
| | - Salil N Vaniawala
- SN Gene Lab, Floor, A, Above Kansaar Hotel, President Plaza, Ring Rd, Aveerbhav Society 1, Nanpura, Surat, Gujarat, India
| | - Arpan Acharya
- SN Gene Lab, Floor, A, Above Kansaar Hotel, President Plaza, Ring Rd, Aveerbhav Society 1, Nanpura, Surat, Gujarat, India
| | - Pratap N Mukhopadhyaya
- SN Gene Lab, Floor, A, Above Kansaar Hotel, President Plaza, Ring Rd, Aveerbhav Society 1, Nanpura, Surat, Gujarat, India
| | - Nilofar R Sodagar
- Department of IVF, Akanksha Hospital and Research Institute, Near Shrushti English Medium School, Lambhvel-387310, Anand, Gujarat, India
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Shrivastava G, Bajpai T, Bhatambare GS, Patel KB. Genital tuberculosis: Comparative study of the diagnostic modalities. J Hum Reprod Sci 2014; 7:30-3. [PMID: 24829528 PMCID: PMC4018795 DOI: 10.4103/0974-1208.130817] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 12/09/2013] [Accepted: 01/14/2014] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Genital tuberculosis (GTB) is one of the major causes for severe tubal disease leading to infertility. Unlike pulmonary tuberculosis (TB), the clinical diagnosis of GTB is difficult because in the majority of cases the disease is either asymptomatic or has varied clinical presentation. Routine laboratory tests are of little value in the diagnosis. The objective of this study was to compare the modalities of polymerase chain reaction (PCR) technique, acid fast bacilli (AFB) culture and AFB staining. MATERIALS AND METHODS The women visiting in vitro fertility center during December 2012 and May 2013 were included in this study. A total of 227 aseptically collected endometrial tissue samples were processed. AFB staining, AFB culture and PCR were carried out using standard procedures. RESULT Out of 227 patients suspected of GTB, 133 were found to be positive either by AFB smear microscopy, culture or PCR. Out of 133 samples, two samples (1.5%) were found to be positive by all three methods, i.e. microscopy, culture and PCR, 11 (4.8%) were found to be positive by both PCR and culture, whereas 126 (86%) samples were found to be positive only by PCR. The PCR has failed to detect seven cases that were positive by conventional culture method. CONCLUSION Our study showed that the conventional methods of diagnosis like microscopy and culture are less sensitive when compared with PCR. PCR also helped in early diagnosis of infection. However simultaneously, false negative results were an important limitation of this method. PCR negative samples were found to be positive by culture methods. Deoxyribose nucleic acid PCR is not reliable for TB due to false positive or negative result. Thus, we suggest both culture and PCR as important diagnostic methods for detection of GTB.
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Affiliation(s)
- Gunjan Shrivastava
- Department of Microbiology, Sri Aurobindo Institute of Medical Sciences and PG Institute, Indore, Madhya Pradesh, India
| | - T Bajpai
- Department of Microbiology, Sri Aurobindo Institute of Medical Sciences and PG Institute, Indore, Madhya Pradesh, India
| | - G S Bhatambare
- Department of Microbiology, Sri Aurobindo Institute of Medical Sciences and PG Institute, Indore, Madhya Pradesh, India
| | - K B Patel
- Department of Microbiology, Sri Aurobindo Institute of Medical Sciences and PG Institute, Indore, Madhya Pradesh, India
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Patel KB, Poplawski MM, Pawha PS, Naidich TP, Tanenbaum LN. Diffusion-weighted MRI "claw sign" improves differentiation of infectious from degenerative modic type 1 signal changes of the spine. AJNR Am J Neuroradiol 2014; 35:1647-52. [PMID: 24742801 DOI: 10.3174/ajnr.a3948] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Modic type 1 degenerative signal changes can mimic/suggest infection, leading to additional costly and sometimes invasive investigations. This retrospective study analyzes the utility and accuracy of a novel, diffusion-weighted "claw sign" for distinguishing symptomatic type 1 degeneration from vertebral diskitis/osteomyelitis. MATERIALS AND METHODS Seventy-three patients with imaging features resembling type 1 degeneration were classified clinically into 3 groups: true degenerative type 1 changes (n = 33), confirmed diskitis/osteomyelitis (n = 20), and radiologically suspected infection later disproved clinically (n = 20). A claw sign was defined on DWI as well-marginated, linear, regions of high signal situated within the adjacent vertebral bodies at the interface of normal with abnormal marrow. Two blinded neuroradiologists independently rated the presence of the claw sign, along with T2 disk signal and disk and endplate enhancement to determine the utility of each for identifying degeneration versus infection. RESULTS When the 2 neuroradiologists identified a definite claw, 38 of 39 patients (97%) and 29 of 29 patients (100%) proved to be infection-free. When the readers identified a probable claw, 14 of 14 patients (100%) and 16 of 19 patients (84%) proved to be infection-free. Conversely, when the readers identified the absence of claw sign (diffuse DWI pattern), there was proved infection in 17 of 17 cases (100%) and 13 of 14 cases (93%). CONCLUSIONS In patients with type 1 signal changes of the vertebral disk space, a claw sign is highly suggestive of degeneration and its absence strongly suggests diskitis/osteomyelitis.
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Affiliation(s)
- K B Patel
- From the Department of Neuroradiology, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - M M Poplawski
- From the Department of Neuroradiology, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - P S Pawha
- From the Department of Neuroradiology, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - T P Naidich
- From the Department of Neuroradiology, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - L N Tanenbaum
- From the Department of Neuroradiology, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York.
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Shrivastava G, Bhatambare GS, Patel KB. Evaluation of prevalence and antibiogram of multi drug resistant, extensively drug resistant and pan drug resistant Pseudomonas aeruginosa in patients visiting a tertiary care hospital in central India. CHRISMED J Health Res 2014. [DOI: 10.4103/2348-3334.138882] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Shrivastava G, Bhatambare GS, Patel KB. Seroprevalance of toxoplasma, rubella, CMV and HSV infection in pregnant women in central India. ACTA ACUST UNITED AC 2014. [DOI: 10.4103/2347-9019.142202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Patel KB, Belliveau PP, Nightingale CH, Nicolau DP, Quintiliani R. Absorption of ciprofloxacin in febrile and afebrile patients. Int J Antimicrob Agents 2010; 6:119-22. [PMID: 18611695 DOI: 10.1016/0924-8579(95)00030-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/1995] [Indexed: 11/18/2022]
Abstract
There are few studies evaluating the effect of fever on the bioavailability of oral antimicrobials. Owing to the growing interest in early conversion of febrile hospitalized patients from intravenous to oral therapy to reduce costs and avoid line sepsis, we evaluated the absorption of a single 500 mg dose of ciprofloxacin in 12 patients during an acute febrile episode and following defervescence. Patients able to take medication by mouth, oral temperature > or = 38.9 degrees C, and no known gastrointestinal disease were enrolled. Medications known to interact with the test agent were discontinued. Serum samples were obtained prior to and up until 12 h postdose. Pharmacokinetic parameters were obtained from the concentration-time profile using noncompartmental methods. The mean values for C(max) were 2.45 +/- 0.77 and 2.31 +/- 1.26 microg/ml, for T(max) 1.48 +/- 0.75 and 2.48 +/- 1.46 h, AUC(0-->infinity) 10.91 +/- 3.64 and 11.05 +/- 4.41 microg/ml h, and T (1 2 ) 4.05 +/- 0.65 and 4.08 +/- 0.76 h, respectively, for the febrile and afebrile periods. No statistically significant differences were observed between these parameters. We conclude that oral ciprofloxacin is well absorbed and is a suitable alternative to intravenous therapy in selected patients during an acute febrile illness.
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Affiliation(s)
- K B Patel
- Division of Pharmacy Practice, Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, NY 11201, USA
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Tekade AR, Patel KB, Shete SN, Belgamwar VS. Formulation design and optimization of taste-masked mouth-dissolving tablets of Tramadol hydrochloride. Asian J Pharm 2010. [DOI: 10.4103/0973-8398.72125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Deota PT, Upadhyay PR, Patel KB, Mehta KJ, Varshney AK, Mehta MH. Effect of some ultraviolet light absorbers on photo-stabilization of azadirachtin-A. Nat Prod Lett 2002; 16:329-34. [PMID: 12434988 DOI: 10.1080/10575630290031981] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The effect of photo-stabilization of Azadirachtin-A (Aza-A) was examined when exposed to sunlight and ultraviolet light in the presence of four structurally different ultraviolet stabilizers namely 4-aminobenzoic acid, 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone and phenyl salicylate. The percentages of Aza-A recovered at different time intervals from slides exposed to different light conditions with and without UV stabilizers as well as kinetic studies indicated that the addition of phenyl salicylate in methanolic solution of Aza-A (in 1:1 mole ratio) provides the best photo-stabilization of Aza-A molecule among the four UV stabilizers studied.
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Affiliation(s)
- P T Deota
- Department of Applied Chemistry, Faculty of Technology & Engineering, M.S. University of Baroda, Vadodara, India.
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Everett SA, Naylor MA, Patel KB, Stratford MR, Wardman P. Bioreductively-activated prodrugs for targeting hypoxic tissues: elimination of aspirin from 2-nitroimidazole derivatives. Bioorg Med Chem Lett 1999; 9:1267-72. [PMID: 10340612 DOI: 10.1016/s0960-894x(99)00171-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
2-Nitroimidazoles were synthesised substituted with aspirin or salicylic acid, as leaving groups linked through the (imidazol-5-yl)methyl position. Activation of aqueous solutions by CO2*- (a model one-electron reductant) resulted in release of aspirin or salicylate, probably via the 2-hydroxyaminoimidazole. The analogous 2-nitroimidazole with bromide as leaving group eliminated bromide in < 1 ms via the radical-anion.
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Affiliation(s)
- S A Everett
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK
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Jaffar M, Everett SA, Naylor MA, Moore SG, Ulhaq S, Patel KB, Stratford MR, Nolan J, Wardman P, Stratford IJ. Prodrugs for targeting hypoxic tissues: regiospecific elimination of aspirin from reduced indolequinones. Bioorg Med Chem Lett 1999; 9:113-8. [PMID: 9990467 DOI: 10.1016/s0960-894x(98)00695-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A series of regioisomeric derivatives of a 1-methylindole-4,7-dione were synthesised, substituted with a 2-acetoxybenzoate leaving group linked through the (indol-2-yl)methyl or (indol-3-yl)methyl (or propenyl) positions. Reductive elimination of the leaving group occurred from the (indol-3-yl)methyl derivatives but not the 2-substituted regioisomers, indicating that only the C-3 position may be utilised in bioreductively-activated drug delivery, which was demonstrated with an aspirin prodrug.
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Affiliation(s)
- M Jaffar
- School of Pharmacy, University of Manchester, UK
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Everett SA, Naylor MA, Nolan J, Patel KB, Wardman P. Indolequinone bioreductive drugs: kinetic factors which influence selectivity for hypoxia. Anticancer Drug Des 1998; 13:635-53. [PMID: 9755722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
The factors influencing the kinetics of the oxygen-sensitive reduction of indolequinones, including those bearing leaving groups in the (indol-3-yl)methyl position, have been studied. The hydroquinones derived from some representative indolequinones were found to autoxidize slowly in oxygenated solution at rates (effective rate constant with O2 approximately 40-300 M-1 s-1) that cannot compete with the reductive elimination of leaving groups. The rates of reaction between hydroquinone and O2 were even slower in the presence of approximately 4 microM superoxide dismutase (effective rate constant approximately 2-7 M-1 s-1), indicating the role of superoxide radicals in hydroquinone autoxidation. Since the release of the leaving groups from the hydroquinones is not significantly oxygen-sensitive, tumour selectivity requires specific reduction by enzymes that are overexpressed in some tumours. Conversely, the release of leaving groups from semiquinone radicals is inhibited by oxygen too efficiently unless the semiquinone reacts with targets on a timescale of milliseconds. Modification of redox properties has been explored with the aim of changing this oxygen sensitivity. The new 2-phenylindolequinones are approximately 60-100 mV higher in reduction potential than 2-alkyl derivatives but this is insufficient to decrease the rate of electron transfer from semiquinone to oxygen to a degree which might confer hypoxia-selective cytotoxicity. These results are discussed in the context of toxicity of EO9 and related compounds towards hypoxic rather than anoxic cells.
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Affiliation(s)
- S A Everett
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK. everett@:graylab.ac.uk
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18
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Klepser ME, Patel KB, Nicolau DP, Quintiliani R, Nightingale CH. Comparison of bactericidal activities of intermittent and continuous infusion dosing of vancomycin against methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. Pharmacotherapy 1998; 18:1069-74. [PMID: 9758317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
STUDY OBJECTIVE To describe the pharmacokinetic profiles of vancomycin administered by continuous infusion and intermittent dosing and compare the duration of activity of the regimens. DESIGN Randomized, open-label, crossover study. SETTING Clinical research center at an academic medical center. SUBJECTS Twelve healthy, nonpregnant volunteers age 27.6 +/- 2.3 years. INTERVENTION Subjects received the following intravenous vancomycin regimens: 1 g every 12 hours; 2 g continuous infusion over 24 hours; and 1 g continuous infusion over 24 hours. Dosages were administered with and without gentamicin 2 mg/kg. MEASUREMENTS AND MAIN RESULTS Serum samples were collected, drug concentrations determined, and bactericidal activity measured against two isolates each of methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. Subjects had poor tolerability for continuous infusions. Trough concentration for the intermittent regimen was 5.5 +/- 1.9 mg/ml, and steady-state concentrations were 8.8 +/- 1.6 and 16.9 +/- 1.9 mg/ml for 1 and 2 g continuous infusions, respectively. In general, all regimens provided bactericidal activity throughout the study interval. Against one isolate of E. faecalis, 2 g continuous infusion plus gentamicin provided cidal activity for a significantly greater percentage of the dosing interval (p<0.001). CONCLUSION Continuous infusion does not greatly improve the activity of vancomycin and should not be routinely administered. However, it may prove useful against isolates with reduced susceptibility to the agent.
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Affiliation(s)
- M E Klepser
- College of Pharmacy, University of Iowa, Iowa City 52242-1112, USA
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19
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Naylor MA, Swann E, Everett SA, Jaffar M, Nolan J, Robertson N, Lockyer SD, Patel KB, Dennis MF, Stratford MR, Wardman P, Adams GE, Moody CJ, Stratford IJ. Indolequinone antitumor agents: reductive activation and elimination from (5-methoxy-1-methyl-4,7-dioxoindol-3-yl)methyl derivatives and hypoxia-selective cytotoxicity in vitro. J Med Chem 1998; 41:2720-31. [PMID: 9667963 DOI: 10.1021/jm970744w] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A series of indolequinones bearing a variety of leaving groups at the (indol-3-yl)methyl position was synthesized by functionalization of the corresponding 3-(hydroxymethyl)indolequinone, and the resulting compounds were evaluated in vitro as bioreductively activated cytotoxins. The elimination of a range of functional groups-carboxylate, phenol, and thiol-was demonstrated upon reductive activation under both chemical and quantitative radiolytic conditions. Only those compounds which eliminated such groups under both sets of conditions exhibited significant hypoxia selectivity, with anoxic:oxic toxicity ratios in the range 10-200. With the exception of the 3-hydroxymethyl derivative, radiolytic generation of semiquinone radicals and HPLC analysis indicated that efficient elimination of the leaving group occurred following one-electron reduction of the parent compound. The active species in leaving group elimination was predominantly the hydroquinone rather than the semiquinone radical. The resulting iminium derivative acted as an alkylating agent and was efficiently trapped by added thiol following chemical reduction and by either water or 2-propanol following radiolytic reduction. A chain reaction in the radical-initiated reduction of these indolequinones (not seen in a simpler benzoquinone) in the presence of a hydrogen donor (2-propanol) was observed. Compounds that were unsubstituted at C-2 were found to be up to 300 times more potent as cytotoxins than their 2-alkyl-substituted analogues in V79-379A cells, but with lower hypoxic cytotoxicity ratios.
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Affiliation(s)
- M A Naylor
- Gray Laboratory Cancer Research Trust, P.O. Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, United Kingdom
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20
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Abstract
The oxidative denitrification of the antitumour agent hydroxyguanidine (HOG) has been investigated by radiolysis methods and EPR spectroscopy. The azide radical (N3.), a model one-electron oxidant, reacts with HOG with the rate constant 5.1 x 10(9) dm3 mol(-1) s(-1) to yield the guanidino carbon-centred radical (HOG.) which rapidly eliminates nitric oxide (k = 3.1 x 10[3] s[-1]) with the concomitant formation of urea. The HOG. undergoes conjugation with molecular oxygen to form a peroxyl radical (HOGOO.) with a rate constant 8.8 x 10(8) dm3 mol(-1) s(-1). The HOGOO. radical also eliminates nitric oxide but may act as a precursor to the peroxynitrite (ONOO-) ion. The oxidation of HOG by the dibromide radical (Br2.-) was found to release nitric oxide with a yield of 95% relative to Br2.- as determined from the combined yields of inorganic nitrite, nitrate and a HOG/nitric oxide-adduct. This study provides a possible mechanistic basis for the oxidative denitrification of HOG which may contribute to the observed toxicity of the drug both in vitro and in vivo and for the oxidation of nonphysiological hydroxyguanidines to NO. via nitric oxide synthase-independent pathways.
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Affiliation(s)
- S A Everett
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK
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21
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Hitt CM, Patel KB, Nicolau DP, Zhu Z, Nightingale CH. Influence of piperacillin-tazobactam on pharmacokinetics of gentamicin given once daily. Am J Health Syst Pharm 1997; 54:2704-8. [PMID: 9408514 DOI: 10.1093/ajhp/54.23.2704] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The effect of piperacillin-tazobactam on the pharmacokinetics of gentamicin given once daily was studied. Healthy adult volunteers each received four drug regimens in randomized order: gentamicin 7 mg/kg i.v. once daily (1) by itself, (2) with piperacillin 4 g and tazobactam 0.5 g (both as the sodium salt) every six hours i.v., (3) with piperacillin 4 g and tazobactam 0.5 g i.v. every eight hours, and (4) with piperacillin 8 g and tazobactam 1 g by continuous i.v. infusion over 24 hours. All the gentamicin doses were infused over 30 minutes two hours after piperacillin-tazobactam. Blood samples were drawn before and at the end of each gentamicin infusion and at intervals up to 12 hours after the start of each gentamicin infusion. Samples were assayed for gentamicin concentration by an enzyme-multiplied immunoassay technique and for piperacillin and tazobactam concentrations by high-performance liquid chromatography. Six women and four men completed all four drug regimens. For the gentamicin-alone regimen, the mean +/- S.D. area under the concentration-versus-time curve was 78.06 +/- 10.28 micrograms/mL.hr, the mean +/- S.D. peak concentration (30 minutes after the end of an infusion) was 20.28 +/- 2.54 micrograms/mL, and the mean +/- S.D. half-life was 2.41 +/- 0.24 hours. The values for gentamicin alone did not differ significantly from those for gentamicin in any of the combination regimens. Coadministration of once-daily gentamicin and piperacillin-tazobactam in various i.v. infusion regimens did not affect the pharmacokinetics of once-daily gentamicin.
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Affiliation(s)
- C M Hitt
- Hospital Pharmacy Services, Mayo Medical Center, Rochester, MN 55902, USA.
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22
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Naylor MA, Jaffar M, Nolan J, Stephens MA, Butler S, Patel KB, Everett SA, Adams GE, Stratford IJ. 2-Cyclopropylindoloquinones and their analogues as bioreductively activated antitumor agents: structure-activity in vitro and efficacy in vivo. J Med Chem 1997; 40:2335-46. [PMID: 9240349 DOI: 10.1021/jm9608422] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A series of 2-cycloalkyl- and 2-alkyl-3-(hydroxymethyl)-1-methylindoloquinones and corresponding carbamates have been synthesized and substituted in the 5-position with a variety of substituted and unsubstituted aziridines. Cytotoxicity against hypoxic cells in vitro was dependent upon the presence of a 5-aziridinyl or a substituted aziridinyl substituent for 3-hydroxymethyl analogues. The activity of 5-methoxy derivatives was dependent upon the presence of a 3-(carbamoyloxy)methyl substituent. Increasing the steric bulk at the 2-position reduced the compounds' effectiveness against hypoxic cells. A 2-cyclopropyl substituent was up to 2 orders of magnitude more effective than a 2-isopropyl substituent, suggesting possible radical ring-opening reactions contributing to toxicity. Nonfused 2-cyclopropylmitosenes were more effective than related fused cyclopropamitosenes reported previously. The reduction potentials of the quinone/semiquinone one-electron couples were in the range -286 to -380 mV. The semiquinone radicals reacted with oxygen with rate constants 2-8 x 10(8) dm3 mol-1 s-1. The involvement of the two-electron reduced hydroquinone in the mediation of cytotoxicity is implicated. The most effective compounds in vitro were the 2-cyclopropyl and 5-(2-methylaziridinyl) derivatives, and of these, 5-(aziridin-1-yl)-2-cyclopropyl-3-(hydroxymethyl)-1-methylindole-4 ,7-dione (21) and 3-(hydroxymethyl)-5-(2-methylaziridin-1-yl)-1,2-dimethylindole+ ++-4,7-dione (54) were evaluated in vivo. Both compounds showed antitumor activity both as single agents and in combination with radiation, with some substantial improvements over EO9 (3) at maximum tolerated doses and as single agents against the RIF-1 tumor model and comparable efficacy in the KHT tumor model.
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Affiliation(s)
- M A Naylor
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom
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23
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Owens RC, Patel KB, Banevicius MA, Quintiliani R, Nightingale CH, Nicolau DP. Oral bioavailability and pharmacokinetics of ciprofloxacin in patients with AIDS. Antimicrob Agents Chemother 1997; 41:1508-11. [PMID: 9210675 PMCID: PMC163949 DOI: 10.1128/aac.41.7.1508] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Few reports on the effects of AIDS on the absorption of orally (p.o.) administered agents exist. To help fill this informational gap, we administered ciprofloxacin to 12 patients with AIDS by two dosing regimens (400 mg given intravenously [i.v.] and 500 mg given p.o. every 12 h) in a randomized, crossover fashion. Pharmacokinetic parameters were determined by noncompartmental methods. Mean values (+/- standard deviations [SD]) for p.o. ciprofloxacin were as follows: peak concentration of drug in serum (Cmax), 2.94 +/- 0.51 microg/ml; time to Cmax, 1.38 +/- 0.43 h; area under the concentration-time curve from 0 to 12 h (AUC(0-12)), 12.13 +/- 3.21 microg x h/ml; and half-life (t(1/2)), 3.86 +/- 0.48 h. Mean values (+/- SD) for i.v. ciprofloxacin were as follows: Cmax, 3.61 +/- 0.82 microg/ml; time to Cmax, 1.0 h; AUC(0-12), 11.92 +/- 2.92 microg x h/ml; and t(1/2), 3.98 +/- 0.94 h. The mean percent absolute bioavailability for ciprofloxacin was calculated to be 82% +/- 13%, similar to the value for healthy volunteers. We conclude that ciprofloxacin when administered p.o. to patients with AIDS is well absorbed, as evidenced by excellent bioavailability and is not affected by gastrointestinal changes in the absence of infectious gastroenteritis and severe diarrhea.
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Affiliation(s)
- R C Owens
- Department of Clinical Pharmacy Services, Medical Center of Delaware, Newark 19718, USA
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24
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Patel KB, Nicolau DP, Nightingale CH, Quintiliani R. Comparative serum bactericidal activities of ceftizoxime and cefotaxime against intermediately penicillin-resistant Streptococcus pneumoniae. Antimicrob Agents Chemother 1996; 40:2805-8. [PMID: 9124845 PMCID: PMC163626 DOI: 10.1128/aac.40.12.2805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In a randomized crossover study involving 12 healthy volunteers, 1 g of ceftizoxime or cefotaxime was administered intravenously every 12 h for a total of three doses on two separate weekends. The duration of serum bactericidal titers (SBTs) greater than 1:2 and the time serum drug concentrations remained above the MIC (T > MIC) were determined against three clinical isolates of Streptococcus pneumoniae with intermediate resistance to penicillin. The duration of SBTs and T > MIC for both antimicrobial agents exceeded 50% of the dosing interval for all isolates. Ceftizoxime's T > MIC was statistically greater than that of cefotaxime, indicating that its longer half-life in serum (1.7 h) compared with that of cefotaxime (approximately 1 h) compensates for its slightly lower microbiologic activity against the penicillin-resistant pneumococci tested in this study.
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Affiliation(s)
- K B Patel
- Department of Pharmacy Practice, Arnold and Marie Schwartz College of Pharmacy, Long Island University, Brooklyn, New York 11201, USA
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25
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Patel KB, Xuan D, Tessier PR, Russomanno JH, Quintiliani R, Nightingale CH. Comparison of bronchopulmonary pharmacokinetics of clarithromycin and azithromycin. Antimicrob Agents Chemother 1996; 40:2375-9. [PMID: 8891147 PMCID: PMC163537 DOI: 10.1128/aac.40.10.2375] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The bronchopulmonary and plasma pharmacokinetics of clarithromycin (CLA; 500 mg given twice daily for nine doses) or azithromycin (AZ; 500 mg for the first dose and then 250 mg once daily for four doses) were assessed in 41 healthy nonsmokers. Bronchoalveolar lavage was performed at 4, 8, 12, or 24 h after administration of the last dose. The concentrations (mean +/- standard deviation) of CLA, 14-hydroxyclarithromycin, and AZ were measured in plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) cells by high-performance liquid chromatography assay. The concentrations of CLA achieved in ELF were 34.02 +/- 5.16 micrograms/ml at 4 h, 20.63 +/- 4.49 micrograms/ml at 8 h, 23.01 +/- 11.9 micrograms/ml at 12 h, and 4.17 +/- 0.29 microgram/ml at 24 h, whereas at the same time points AZ concentrations remained below the limit of assay sensitivity (0.01 microgram/ml) for all but two subjects. The concentrations of CLA in the AM cells were significantly higher than those of AZ at 8 h (703 +/- 235 and 388 +/- 53 micrograms/ml, respectively). However, the ratio of the concentration in AM cells/concentration in plasma was significantly higher for AZ than for CLA for all time points because of the lower concentration of AZ in plasma. These results indicate that while AZ has higher tissue concentration to plasma ratios, as shown by other investigators, the absolute concentrations of CLA in AM cells and ELF are higher for up to 8 and 12 h, respectively, after administration of the last dose.
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Affiliation(s)
- K B Patel
- Department of Pharmacy Practice, Arnold and Marie Schwartz College of Pharmacy, Long Island University, Brooklyn, New York 11201, USA
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26
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Everett SA, Smith KA, Patel KB, Dennis MF, Stratford MR, Wardman P. Nitric oxide involvement in the toxicity of hydroxyguanidine in leukaemia HL60 cells. Br J Cancer Suppl 1996; 27:S172-6. [PMID: 8763874 PMCID: PMC2150015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The free-radical intermediates and the stable products formed on one-electron oxidation of hydroxyguanidine (HOG) were investigated in order to suggest a mechanistic basis for HOG-induced cytotoxicity and cytostasis in leukaemia HL60 cells. The azide radical (generated radiolytically) reacted with HOG to produce a carbon-centred radical which in the absence of oxygen decays by a first-order process (k = 3.2 x 10(3) s-1) to yield nitric oxide (NO) and urea. Although the HOG radical reacts rapidly with oxygen (rate constant for O2 addition, k = 4.2 x 10(8) dm3 mol-1 s-1) this neither prevented the elimination of NO. nor generated alternative nitrogen oxides (e.g. peroxynitrite) capable of contributing to cellular oxidative stress. The detection of NO. in HL60 cells corroborated mechanistic studies that oxidative denitrification of HOG does not require catalysis by nitric oxide synthase. Quantitation of NO. by electron paramagnetic resonance (EPR) spectroscopy (utilising a NO. -selective probe) shows higher amounts of NO. under anoxic conditions, reflecting competition for NO. with molecular oxygen in oxic cells. Inhibition of cytochrome P450 and myeloperoxidase activity decreased NO. production thereby identifying these enzyme systems as capable of oxidizing HOG in vitro. A correlation exists between the intracellular levels of NO. with both the cytotoxic and cytostatic effects of HOG within HL60 cells. A higher toxicity was observed with hypoxic than with oxic cells. The lower levels of NO. associated with aerobic conditions caused a G1 --> S block in the cell cycle which under anoxia potentiated NO. -induced apoptotic cell death.
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Affiliation(s)
- S A Everett
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK
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27
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Everett SA, Dennis MF, Patel KB, Stratford MR, Wardman P. Oxidative denitrification of N omega-hydroxy-L-arginine by the superoxide radical anion. Biochem J 1996; 317 ( Pt 1):17-21. [PMID: 8694760 PMCID: PMC1217459 DOI: 10.1042/bj3170017] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The superoxide radical anion (O2-.) produced during the catalytic activity of nitric oxide synthase (NOS) and cytochrome P-450 has been implicated in the oxidative denitrification of hydroxyguanidines ( > C = NOH). The reactivity of the radiolytically generated O2-. radical with N omega-hydroxy-L-arginine (NHA) is pH dependent and appears to parallel the prototropic equilibrium of the hydroxyguanidino group ( > C = NOH reversible > C = NO(-)+H+; pK = 8). The N omega-hydroxyguanidino group is more reactive towards O2-. when deprotonated but exhibits negligible reactivity when protonated. Based on a model, the rate constant for the reaction of the O2-. with NHA was estimated as kappa (O2-.+ > C = NO-) approximately 200-500 M-1.s-1, which is probably too low to compete with O2-. reactions with NO- or superoxide dismutase, which occur many orders of magnitude faster. The oxidative elimination of NO from NHA by O2-. was not accompanied by the formation of L-citrulline. Since only 21% of NHA will exist in the deprotonated > C = NO- form at physiological pH, it is unlikely that oxidative denitrification of NHA by cytochrome P-450 or NOS-derived O2-. radicals will prove a major free-radical pathway to NO. and L-citrulline.
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Affiliation(s)
- S A Everett
- Gray Laboratory Cancer Research Trust, Mount Vermon Hospital, Northwood, Middlesex, U.K
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28
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Wardman P, Priyadarsini KI, Dennis MF, Everett SA, Naylor MA, Patel KB, Stratford IJ, Stratford MR, Tracy M. Chemical properties which control selectivity and efficacy of aromatic N-oxide bioreductive drugs. Br J Cancer Suppl 1996; 27:S70-4. [PMID: 8763850 PMCID: PMC2150009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Pulse radiolysis was used to generate radicals from one electron reduction of 1,2,4-benzotriazine-1,4-dioxides (derivatives of tirapazamine), and of imidazo [1,2-a]quinoxaline-4-oxides (analogues of RB90740), which have selective toxicity towards hypoxic cells. Radicals from the mono N-oxides (from the latter compounds) react with oxygen approximately 10-40 times faster than does the tirapazamine radical. Radicals from the tirapazamine analogues studied react with oxygen up to approximately 10 times slower than tirapazamine radicals. The quinoxaline N-oxide radicals are involved in prototropic equilibria with pK(a) values (5.5 to 7.4) spanning that reported for tirapazamine (6.0). Generation of radicals radiolytically in the presence of H donors (formate, 2-propanol, deoxyribose) indicate a chain reaction ascribed to H abstraction by the drug radical. The protonated drug radical is much more reactive than the radical anion (H abstraction rate constant approximately equal to 10(2) - 10(3) dm3 mol-1 s-1). Chain termination is ascribed to drug radical-radical reactions, i.e. radical stability in anoxia, with rate constants 2k approximately equal to 1 x 10(7) to 2 x 10(8) dm3 mol-1 s-1 at pH approximately 7.4. Estimates of the reduction potentials of the drug-radical couples in water at pH 7 for two of the mono-N-oxides were in the range-0.7 to 0.8 V vs NHE at pH 7.
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Affiliation(s)
- P Wardman
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK
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29
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Everett SA, Dennis MF, Patel KB, Maddix S, Kundu SC, Willson RL. Scavenging of nitrogen dioxide, thiyl, and sulfonyl free radicals by the nutritional antioxidant beta-carotene. J Biol Chem 1996; 271:3988-94. [PMID: 8626730 DOI: 10.1074/jbc.271.8.3988] [Citation(s) in RCA: 161] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Mechanisms of free radical scavenging by the nutritional antioxidant beta-carotene have been investigated by pulse radiolysis. Free radicals, which can initiate the chain of lipid peroxidation, including nitrogen dioxide (NO2.), thiyl (RS.), and sulfonyl (RSO2.) radicals, are rapidly scavenged by beta-carotene. Absolute rate constant k[NO2. + beta-carotene] = (1.1 +/- 0.1) x 10(8) m-1 s-1 and for the glutathione thiyl radical k[GS. + beta-carotene] = (2.2 +/- 0.1) x 10(8) m-1 s-1 have been determined. The mechanisms however are mutually exclusive, the former involving electron transfer to generate the radical-cation [ beta-carotene]+. and the latter by radical-addition to generate an adduct-radical [RS... beta-carotene].. Rate constants for thiyl radical-addition reactions vary from 10(6) to 10(9) m-1 s-1 and correlate with the lipophilicity of the thiyl radical under study. Sulfonyl radicals undergo both electron abstraction, [ beta-carotene]+. and radical-addition, [RSO2... beta-carotene]. in an approximate 3:1 ratio. The beta-carotene radical-cation and adduct-radicals are highly resonance stabilized and undergo slow bimolecular decay to non-radical products. These carotenoid-derived radicals react differently with oxygen, a factor which is expected to influence the antioxidant activity of beta-carotene within tissues of varying oxygen tension in vivo.
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Affiliation(s)
- S A Everett
- Gray Laboratory, P. O. Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, United Kingdom
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Nicolau DP, Marangos MN, Nightingale CH, Patel KB, Cooper BW, Quintiliani R, Courvalin P, Quintiliani R. Efficacy of vancomycin and teicoplanin alone and in combination with streptomycin in experimental, low-level vancomycin-resistant, VanB-type Enterococcus faecalis endocarditis. Antimicrob Agents Chemother 1996; 40:55-60. [PMID: 8787879 PMCID: PMC163056 DOI: 10.1128/aac.40.1.55] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The efficacy of vancomycin (VM) and teicoplanin (TE), alone and in combination with streptomycin (SM), against enterococci that express low-level VanB-type VM resistance was investigated in experimental endocarditis using isogenic strains of Enterococcus faecalis susceptible to glycopeptides and aminoglycosides or inducibly resistant to low levels of VM (MIC = 16 micrograms/ml). VM was significantly less active against the resistant strain than against the susceptible strain, establishing that low-level VanB-type VM resistance can influence therapeutic efficacy. By contrast, TE had equally good activity against both strains. VM or TE combined with SM was synergistic and bactericidal against the resistant strain in vitro. While both combinations were efficient in reducing bacterial density in vivo, TE plus SM was significantly superior to VM plus SM if valve sterilization was considered. These data suggest that despite the presence of low-level VanB-type resistance, combination therapy with a glycopeptide and SM (and presumably other aminoglycosides to which there is not high-level resistance) will nevertheless provide effective bactericidal activity.
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Affiliation(s)
- D P Nicolau
- Division of Infectious Diseases, Hartford Hospital, Connecticut, USA
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31
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Abstract
Steady-state radiolysis, pulse radiolysis and epr studies, combined with enzyme activity measurements, were carried out on the mechanism by which radical attack, through one-electron oxidation, inactivates xanthine oxidase. Electron transfer to both the N3 and Br2- radical species was used to initiate oxidative damage on the enzyme. Inactivation was found to occur to a greater extent at low than at high pH and is associated with the initial formation of a tryptophanyl radical which converts by a known intramolecular pathway to a tyrosyl radical with a rate constant of 5 x 10(3) S-1. The tyrosyl radical in turn slowly loses around half of its absorbance at an intramolecular rate constant of 350S-1 and is consistent with the establishment of a radical equilibrium with cysteine residue(s). The sequence of reactions could be repeated several times on the same irradiated sample implying that restitution of the implied cysteinyl radical occurs leading to other damage in the protein. N3+Trp/N-->Trp/N-->Tyr/O<-->Cys/S-->?. Epr evidence implies that inactivation of the enzyme from the above sequence of reactions arises in part from alternations to Fe/S center I in the enzyme.
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Affiliation(s)
- R F Anderson
- Department of Chemistry, University of Auckland, New Zealand
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Wardman P, Dennis MF, Everett SA, Patel KB, Stratford MR, Tracy M. Radicals from one-electron reduction of nitro compounds, aromatic N-oxides and quinones: the kinetic basis for hypoxia-selective, bioreductive drugs. Biochem Soc Symp 1995; 61:171-94. [PMID: 8660394 DOI: 10.1042/bss0610171] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Drugs based on nitroarene, aromatic N-oxide or quinone structures are frequently reduced by cellular reductases to toxic products. Reduction often involves free radicals as intermediates which react rapidly with oxygen to form superoxide radicals, inhibiting drug reduction. The elevation of cellular oxidative stress accompanying oxygen inhibition of reduction is generally less damaging than drug reduction to toxic products, so the drugs offer selective toxicity to hypoxic cells. Since such cells are resistant to radiotherapy, these bioreductive drugs offer potential in tumour therapy. The basis for the selectivity of action entails kinetic competition involving the contesting reaction pathways. The reduction potential of the drug, radical pKa and nature of radical/radical decay kinetics all influence drug activity and selectivity, including the range of oxygen tensions over which the drug offers selective toxicity. These properties may be quantified using generation of radicals by pulse radiolysis, presenting a physicochemical basis for rational drug design.
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Affiliation(s)
- P Wardman
- Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, U.K
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33
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Klepser ME, Patel KB, Nicolau DP, Quintiliani R, Nightingale CH. Comparison of the bactericidal activities of ofloxacin and ciprofloxacin alone and in combination with ceftazidime and piperacillin against clinical strains of Pseudomonas aeruginosa. Antimicrob Agents Chemother 1995; 39:2503-10. [PMID: 8585734 PMCID: PMC162973 DOI: 10.1128/aac.39.11.2503] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
On the basis of MIC data, ciprofloxacin exhibits superior activity against Pseudomonas aeruginosa than the other currently available fluoroquinolones do. Despite the antipseudomonal advantage noted for ciprofloxacin monotherapy, it is unknown whether this advantage is maintained when the fluoroquinolones are used in combination with antipseudomonal beta-lactams such as ceftazidime and piperacillin. Twelve healthy volunteers were enrolled in this open-label, randomized, steady-state, six-way cross-over, comparative trial. All subjects received the following regimens: (i) 400 mg of ofloxacin given intravenously (i.v.) every 12 h (q12h), (ii) 400 mg of ciprofloxacin given i.v. q12h, (iii) 400 mg of ofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. every 8 h (q8h), (iv) 400 mg of ciprofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. q8h, (v) 400 mg of ofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h, and (vi) 400 mg of ciprofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h. Serum bactericidal titers with subsequent calculation of the area under the bactericidal curve were determined against three clinical isolates of P. aeruginosa. As monotherapy, ciprofloxacin demonstrated superior antipseudomonal activity than ofloxacin did; however, combination of these agents with ceftazidime yielded remarkably similar and statistically comparable activity profiles. In contrast, ciprofloxacin-piperacillin retained a bactericidal advantage over ofloxacin-piperacillin. Although ciprofloxacin exhibits superior antipseudomonal activity when used as monotherapy, combination of ofloxacin or ciprofloxacin with ceftazidime yielded equivalent activity profiles against susceptible strains of P. aeruginosa.
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Affiliation(s)
- M E Klepser
- Department of Pharmacy, Hartford Hospital, Connecticut 06102, USA
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34
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Patel KB, Nicolau DP, Nightingale CH, Quintiliani R. Continuous infusion of beta-lactam antibiotics: a rational dosing approach. Conn Med 1995; 59:471-4. [PMID: 7554900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- K B Patel
- Department of Pharmacy, Hartford Hospital, USA
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35
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Abstract
Several new cephalosporins have been developed in recent years. These agents include several oral and parenteral agents with extended activity against Gram-negative pathogens. The pharmacokinetic literature for these agents is quite extensive; therefore, we have summarised this information and presented it in tabular form for critical comparison. With a few exceptions, the newer cephalosporins share similar pharmacokinetic properties. Cefixime, cefetamet pivoxil and ceftibuten differ from the others in that they exhibit nonlinear pharmacokinetic properties. The nonlinear nature of these agents is reflected by decreasing maximal concentrations with escalating doses of cefixime and cefetamet pivoxil, decreasing area under the serum concentration-time curve with increasing doses for cefixime, and a reduced bioavailability with large doses of ceftibuten. Attention to such characteristics aid the clinician in selecting appropriate dosage regimens that will optimise drug absorption. The majority of agents are primarily renally eliminated; however, renal elimination accounts for only 20% of cefixime elimination. The pharmacokinetic parameters noted for the newer cephalosporins are not influenced by multiple-dose administration, suggesting lack of drug accumulation over time. The pharmacodynamics of antimicrobials should be considered when extrapolating pharmacokinetic information into the clinical arena. In the case of the beta-lactams, the time which drug concentrations remain above some critical threshold, such as the minimal inhibitory concentration, appears to have the greatest influence on bactericidal activity. Therefore, it is important to select dosage regimens that will optimise the time serum concentrations remain above this threshold. We present an evaluation of these agents with respect to their activity against a variety of pathogens in an effort to demonstrate a pharmacokinetically-based process of antimicrobial selection.
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Affiliation(s)
- M E Klepser
- Department of Pharmacy Research, Hartford Hospital, Connecticut, USA
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Abstract
Cefotaxime is a third-generation cephalosporin that has maintained good susceptibility pattern despite its extensive use. It is available for intravenous and intramuscular administration. Its pharmacokinetic property includes a small volume of distribution with low protein binding. Cefotaxime's half-life is approximately 1.1 h, and it is primarily eliminated by the kidney. It has an active metabolite desacetyl-cefotaxime that displays pharmacokinetic properties similar to cefotaxime. Desacetyl-cefotaxime has a half-life of 1.5 h and also is eliminated by the kidneys by both glomerular filtration and active secretion. The half-life of cefotaxime and its metabolite is altered in patients with severe renal dysfunction requiring dosage adjustment. Despite its relatively short half-life, cefotaxime may be dosed every 12 h based on its pharmacokinetic and pharmacodynamic properties.
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Affiliation(s)
- K B Patel
- Department of Pharmacy, Hartford Hospital, CT 06102, USA
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Nicolau DP, Patel KB, Quintiliani R, Nightingale CH. Cephalosporin-metronidazole combinations in the management of intra-abdominal infections. Diagn Microbiol Infect Dis 1995; 22:189-94. [PMID: 7587038 DOI: 10.1016/0732-8893(95)00079-p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
With our current understanding of antimicrobial pharmacokinetics and pharmacodynamics, optimal antimicrobial dosing strategies can be developed for a variety infectious processes. Herein, we discuss the clinical utility of a combination containing a third-generation cephalosporin plus metronidazole as compared to conventional single agents (cefoxitin and ampicillin-sulbactam) for the management intra-abdominal infections. At present, several studies have been performed that compare the bactericidal activity of such combinations to that of single agents for organisms commonly isolated from these intra-abdominal process. From these studies it appears that the use of a third-generation cephalosporin with strong activity against common aerobic organisms associated with intra-abdominal infections in combination with a potent anaerobic drug such as metronidazole provides improved antibacterial activity and optimizes the pharmacodynamic profile of the agents over the dosing interval compared to conventional single agents. As a result of the pharmacokinetic and pharmaco-dynamic superiority of the combination regimen, considerable pharmacoeconomic advantages may be realized with the clinical implementation of a third-generation cephalosporin plus metronidazole regimen. This approach should result in maximal clinical efficacy and is important not only for individual patient therapy, but also for formulary management decisions.
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Affiliation(s)
- D P Nicolau
- Department of Medicine, Hartford Hospital, CT 06102, USA
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Abstract
Acute non-lymphocytic leukaemia is a well recognised and increasingly reported complication of treated Hodgkin's disease. The prognosis is generally poor with a disappointing response to chemotherapy. A patient in whom myelodysplastic features appeared after treatment for Hodgkin's disease, to be followed shortly afterwards by acute promyelocytic leukaemia, is reported. Complete remission was achieved and sustained until Hodgkin's disease reappeared three years later when the patient was autografted with a marrow harvested four years earlier. The patient remains in good health with platelet support at the time of writing.
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Affiliation(s)
- N G Flanagan
- Department of Haematology, Victoria Hospital, Blackpool
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Candeias LP, Patel KB, Stratford MR, Wardman P. Free hydroxyl radicals are formed on reaction between the neutrophil-derived species superoxide anion and hypochlorous acid. FEBS Lett 1993; 333:151-3. [PMID: 8224156 DOI: 10.1016/0014-5793(93)80394-a] [Citation(s) in RCA: 167] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Superoxide anion reacts with hypochlorous acid to yield free hydroxyl radicals, as shown by the hydroxylation of benzoate. This reaction is analogous to the Haber-Weiss reaction but in the absence of metal ions is at least six orders of magnitude faster.
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Affiliation(s)
- L P Candeias
- Cancer Research Campaign Gray Laboratory, Northwood, Middlesex, UK
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Kettle AJ, Robertson IG, Palmer BD, Anderson RF, Patel KB, Winterbourn CC. Oxidative metabolism of amsacrine by the neutrophil enzyme myeloperoxidase. Biochem Pharmacol 1992; 44:1731-8. [PMID: 1333205 DOI: 10.1016/0006-2952(92)90066-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Oxidative metabolism of the anti-cancer drug amsacrine 4'-(9-acridinylamino) methane-sulphan-m-anisidide has been suggested to account for its cytotoxicity. However, enzymes capable of oxidizing it in non-hepatic tissue have yet to be identified. A potential candidate, that may be relevant to the metabolism of amsacrine in blood and its action in myeloid leukaemias and myelosuppression, is the haem enzyme myeloperoxidase. We have found that the purified human enzyme oxidizes amsacrine to its quinone diimine, either directly or through the production of hypochlorous acid. In comparison, the 4-methyl-5-methylcarboxamide derivative of amsacrine, CI-921 9-[[2-methoxy-4[(methylsulphonyl)-amino]phenyl]amino)-N, 5-dimethyl-4-acridine carboxamide, reacted poorly with myeloperoxidase, although it was oxidized by hypochlorous acid. Detailed studies of the mechanism by which myeloperoxidase oxidizes amsacrine revealed that the semiquinone imine free radical is a likely intermediate in this reaction. Oxidation of amsacrine analogues indicated that factors other than their reduction potential determine how readily they are metabolized by myeloperoxidase. Both amsacrine and CI-921 inhibited production of hypochlorous acid by myeloperoxidase. CI-921 acted by trapping the enzyme as the inactive redox intermediate compound II. Amsacrine inhibited by a different mechanism that may involve conversion of myeloperoxidase to compound III, which is also unable to oxidize Cl-. The susceptibility of amsacrine to oxidation by myeloperoxidase indicates that this reaction may contribute to the cytotoxicity of amsacrine toward neutrophils, monocytes and their precursors.
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Affiliation(s)
- A J Kettle
- Free Radical Research Unit, Christchurch School of Medicine, New Zealand
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Anderson RF, Patel KB, Vojnovic B. Absorption spectra of radical forms of 2,4-dihydroxybenzoic acid, a substrate for p-hydroxybenzoate hydroxylase. J Biol Chem 1991; 266:13086-90. [PMID: 1649177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Combined optical and conductimetric measurements in aqueous solution indicate that at high pH (greater than or equal to 10).OH radicals react with the phenoxide form of 2,4-dihydroxybenzoic acid to form transiently phenoxyl radicals and a small amount of hydroxyeyclohexadienyl (HCHD) radicals by 150 ns. The respective yields of 88 and 12% of the total.OH radical yield were deduced from conductance and optical changes as well as from studies using a low potential reductant. The HCHD radical possesses a pKa of 8.0 +/- 0.1 and the constructed spectrum of the deprotonated forms of HCHD has a lambda max at 420 nm with a minimum extinction coefficient of approximately 7250 M-1 cm-1. The red shift in lambda max and increase in extinction coefficient compared to the revised spectral properties of the protonated form of the HCHD radical (lambda max at 390 nm with extinction coefficient of approximately 4500 M-1 cm-1), together with the pKa of the HCHD radical, provide an explanation for the pH-dependent spectral changes of the so-called highly absorbing intermediate II species, observed in the functioning of the enzyme p-hydroxybenzoate hydroxylase. These results add further to the evidence in support of the proposal that intermediate II is composed of species which absorb similarly to the flavin 4(a)-hydroxide and a form of the substrate/product such as the HCHD radical (Anderson, R. F., Patel, K. B., and Stratford, M. R. L. (1987) J. Biol. Chem. 262, 17475-17479).
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Affiliation(s)
- R F Anderson
- Gray Laboratory of the Cancer Research Campaign, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom
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Anderson RF, Patel KB, Stratford MR. Absorption spectra of the hydroxycyclohexadienyl radicals of substrates for phenol hydroxylase. J Biol Chem 1990; 265:1952-7. [PMID: 2153671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The absorption spectra of the hydroxycyclohexadienyl radicals formed upon the addition of OH radicals to six substrates for phenol hydroxylase have been determined using pulse radiolysis. Combining the radical spectra of thiophenol (lambda max, 390 nm; epsilon, 10,500 M-1 cm-1) and resorcinol (lambda max, 340 nm; epsilon, 4,100 M-1 cm-1) with their respective published spectra of enzyme-bound reduced flavin that is substituted in the C(4a) position of the dihydroflavin ring gave composite spectra that closely match the spectra formed concomitantly with the introduction of an oxygen atom into the substrates, the so-called Intermediate II species. A similar procedure for the substrates hydroquinone, 3-aminophenol, 3-chlorophenol, and 3-methylphenol yielded spectra that are also consistent with the known characteristics of their Intermediate II species. These spectral results give further support to the proposed biradical mechanism (Anderson, R.F., Patel, K. B., and Stratford, M. R. L. (1987) J. Biol. Chem. 262, 17475-17479) for the functioning of this class of flavoprotein hydroxylases.
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Affiliation(s)
- R F Anderson
- Gray Laboratory of the Cancer Research Campaign, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom
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Anderson RF, Patel KB, Stratford MR. Absorption spectra of the hydroxycyclohexadienyl radicals of substrates for phenol hydroxylase. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39924-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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45
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Mehta BC, Patel KB, Mehta JB. Effect of iron deficiency on renal function. J Assoc Physicians India 1989; 37:685-6. [PMID: 2632528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Renal function was assessed by determining three hour creatinine clearance (THCC) values in 20 patients (13 males, seven females; age 16-55 years) of nutritional iron deficiency anaemia. Mean transferrin saturation was 4.6% (SD 2.3). Haemoglobin and THCC were determined twice at the interval of three days before therapy. All patients received total dose iron-dextran intravenously. Three days after therapy, haemoglobin and THCC were determined again. Paired 't' test was used to determine the significance of the difference. There was no significant difference between the two pretherapy mean haemoglobin values (6.1 +/- 3.5 g/dl and 5.6 +/- 4.5 g/dl; p greater than 0.2), and the two pretherapy mean THCC values (67.2 +/- 36.9 ml/min and 70.3 +/- 22.8 ml/min; p greater than 0.5). There was no significant difference (p greater than 0.5) between pre-and post-therapy mean haemoglobin levels (6.6 +/- 2.2 g/dl). The difference between the pre-therapy and post-therapy THCC (95.3 +/- 34.0 ml/min) was statistically significant (p less than 0.01). It is concluded on the basis of these results that renal function as measured by THCC is impaired in iron deficiency anaemia, and it improves significantly within three days of total dose intravenous iron-dextran therapy when there is no significant increase in haemoglobin value. This is likely to represent the effect of iron at the tissue level independent of the anaemia.
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Anderson RF, Patel KB, Reghebi K, Hill SA. Conversion of xanthine dehydrogenase to xanthine oxidase as a possible marker for hypoxia in tumours and normal tissues. Br J Cancer 1989; 60:193-7. [PMID: 2765364 PMCID: PMC2247042 DOI: 10.1038/bjc.1989.249] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The enzyme activities of endogenous xanthine dehydrogenase (XDH) and xanthine oxidase (XO) have been measured in 10 different types of mouse tumour and seven normal tissues. The conversion of XDH to XO has been observed in two tumour types upon the prolonged clamping off of the blood supply to the tumours. It is proposed that a similar conversion might also occur naturally in chronically hypoxic cells and that the ratio of the XO activity to the combined XO + XDH activities (%XO activity) could well serve as a marker for tissue hypoxia. A qualitative relationship exists between the %XO activity and literature values of the hypoxic fraction for some tumours measured by radiobiological assays. The influence of tumour size (about 0.2-1.8 g) on %XO activity is presented for all 10 tumours as well as %XO activity determinations for four of the normal tissues.
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Affiliation(s)
- R F Anderson
- Cancer Research Campaign Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex, UK
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Anderson RF, Patel KB, Stratford MR. Absorption spectra of radicals of substrates for p-hydroxybenzoate hydroxylase following electrophilic attack of the .OH radical in the 3 position. J Biol Chem 1987; 262:17475-9. [PMID: 2826422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The spectra of radicals formed upon the addition of .OH radicals to the 3 position of substrates for p-hydroxybenzoate hydroxylase (4-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, and 4-aminobenzoic acid) have been determined using pulse radiolysis combined with the results from high performance liquid chromatography measurements. The 3-hydroxy radical forms of the substrates absorb maximally in the 365-410 nm region with extinction coefficients in the range 3700-5250 M-1 cm-1. Upon combining these radical spectra with the known spectrum of enzyme-bound reduced flavin that is substituted in the C(4a) position of the isoalloxazine ring, spectra are found which closely resemble the species long thought to be formed concomitantly with the introduction of an oxygen atom into substrates. On the basis of these spectral results a new radical mechanism is proposed for the functioning of this class of flavoprotein hydroxylases.
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Affiliation(s)
- R F Anderson
- Gray Laboratory of the Cancer Research Campaign, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom
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Anderson RF, Patel KB, Stratford MR. Absorption spectra of radicals of substrates for p-hydroxybenzoate hydroxylase following electrophilic attack of the .OH radical in the 3 position. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45404-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Anderson RF, Patel KB, Evans MD. Changes in the survival curve shape of E. coli cells following irradiation in the presence of uncouplers of oxidative phosphorylation. Int J Radiat Biol Relat Stud Phys Chem Med 1985; 48:495-504. [PMID: 3899961 DOI: 10.1080/09553008514551561] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Four uncouplers of oxidative phosphorylation (UOP) (carbonyl cyanide m-chlorophenylhydrazone, 2,4-dinitrophenol, 4-hydroxybenzylidenemalonitrile and N-phenylanthranilic acid) have been found to alter the shape of the radiation survival curves of several cell lines of E. coli when present during irradiation in oxia. Incubation of cells with high concentrations of UOP for 30 min before irradiation induced an increase in extrapolation number (n) in cell lines AB 1157 (wild-type), AB 1886(uvrA-) and KMBL(polA-) but not GR 501(lig-)ts, AB 2463(recA-) and AB 2480(uvrA-recA-). In addition the UOP all effect a decrease in mean lethal dose (D0) even when tested at low concentrations or short contact times. Studies with wild-type cells correlate the increase in n with measured increased levels of ATP (above oxic control cells) produced upon incubation with UOP. The increased levels of ATP most likely arise from the UOP overstimulating glycolysis. The decrease in D0 cannot be associated with any of the repair pathways investigated and it is concluded that the highly lipophilic UOP directly or indirectly potentiate other target(s) to radiation damage as well as DNA under oxic conditions. Treatment of the cells with UOP did not result in the deleterious depletion of energy substrates, loss of non-protein thiols or the production of cytotoxins upon irradiation.
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Anderson RF, Patel KB, Stratford MR. The influence of thiols on the pre-irradiation incubation effect of nitroimidazoles in E. coli cells. Int J Radiat Biol Relat Stud Phys Chem Med 1985; 48:485-94. [PMID: 3899960 DOI: 10.1080/09553008514551551] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The increase in the degree of radiosensitization of Escherichia coli cells following prolonged pre-irradiation incubation with nitroimidazoles is not correlated with the loss of intracellular non-protein thiols (NPSH) alone. The rates of reduction of the nitro compounds and the NPSH removal do not show strong dependencies on the lipophilicities of the nitroimidazoles whereas the highly lipophilic compound RGW-609 effects an increase in radiosensitization in a much shorter incubation time than the other nitroimidazoles. Exogenous dithiothreitol (DTT) increased the rate of reduction of misonidazole in the cells but did not alter the fraction converted to the amine. Added DTT (0.15 mmol dm-3) completely protected against the pre-irradiation incubation effect of misonidazole (2.5 mmol dm-3) when added at the start of the incubation but only partially protected when added before irradiation. It is suggested that NPSH can intercept metabolite(s) (or their precursors) of nitroimidazoles which can potentiate cell killing by radiation.
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