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Heller RS, Stoffers DA, Hussain MA, Miller CP, Habener JF. Misexpression of the pancreatic homeodomain protein IDX-1 by the Hoxa-4 promoter associated with agenesis of the cecum. Gastroenterology 1998; 115:381-7. [PMID: 9679043 DOI: 10.1016/s0016-5085(98)70204-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS The endoderm-specific homeodomain transcription factor IDX-1 is critical for pancreas development and for the regulation of islet cell-specific genes. During development, IDX-1 is expressed in the epithelial cells of the endoderm in the pancreatic anlage of the foregut. The aim of this study was to determine whether IDX-1 may have potential properties of a master homeotic determinant of pancreas and/or gut development. METHODS Transgenic mice were generated in which the expression of IDX-1 was misdirected by a promoter of the mesoderm-specific homeodomain protein Hoxa-4 known to express in the stomach and hindgut during development. The expectation was the formation of ectopic pancreatic tissue or alterations of gut patterning or morphology. RESULTS Although no ectopic induction of pancreatic markers was found in these transgenic mice, they manifested an altered midgut-hindgut union and agenesis of the cecum. Further, IDX-1 binds to the gut-specific homeodomain protein Cdx-2 and inhibits transactivation of the sucrase-isomaltase promoter by Cdx-2. CONCLUSIONS These findings further support the emerging understanding that interactions among different classes of homeodomain proteins, expressed in a spatially and temporally restricted manner during development, determine the pattern of organogenesis. A possible mechanism for the dysmorphogenesis of the proximal colon may be an inhibition of Cdx-2 actions by IDX-1.
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Malaviya AN, Hussain MA, Abdeen S, Cherian S, Rashid W. Cytophagic histiocytic panniculitis: a rare catastrophic form of systemic panniculitis. BRITISH JOURNAL OF RHEUMATOLOGY 1998; 37:799-800. [PMID: 9714365 DOI: 10.1093/rheumatology/37.7.799] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Chang RK, Raghavan KS, Hussain MA. A study on gelatin capsule brittleness: moisture tranfer between the capsule shell and its content. J Pharm Sci 1998; 87:556-8. [PMID: 9572904 DOI: 10.1021/js9704238] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Variation in moisture content of the capsule shells either due to the change of storage conditions or the moisture transfer between the capsule shell and its contents may lead to undesired physical properties, such as capsule brittleness and stickiness. DMP 504, a developmental bile-acid sequestrant, is a strongly basic anion-exchange polymer which contains randomly distributed primary, secondary, tertiary, and quaternary amine groups in their hydrochoride salt form. The alkylammonium groups which comprise this polymer form a random network containing a high level of branching and a low level of cross-linking. DMP 504 is very hygroscopic and has a tendency to gain or lose moisture with ease. The transfer of moisture from the capsule shell to DMP 504 powder contained in a hard gelatin capsule can be expected, and if a low water content of the capsule shell is achieved, the capsules become brittle and fracture easily. The sorption isotherm for DMP 504 was generated by storing the drug substance under various relative humidity conditions. After equilibrium, the moisture contents for the samples of individual isotherm points were measured by thermogravimetric analyses. This report applies the sorption-desorption moisture transfer (SDMT) model to predict the equilibrium relative humidity in a system containing DMP 504 in hard gelatin capsules and to establish target loss on drying values for DMP 504 and the capsule shell. Application of this SDMT model resulted in finding a solution to the brittleness problem. The moisture levels of capsule shells and contents for two formulations in a 12-month stability program are also reported here. Results of this study further demonstrate that the SDMT model can be used as a tool to guide the formulator to select optimal initial moisture contents for the empty capsule shell and the formulation to avoid the incidence of brittle capsule problems.
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Ahmed HF, Hussain MA, Grant CE, Wadleigh RG. Closure of tracheoesophageal fistulas with chemotherapy and radiotherapy. Am J Clin Oncol 1998; 21:177-9. [PMID: 9537207 DOI: 10.1097/00000421-199804000-00017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In patients who have esophageal cancer with a tracheoesophageal fistula, chemotherapy and radiotherapy are usually contraindicated because it is thought to enlarge the fistula. The records of 50 patients who had esophageal cancer and received simultaneous chemotherapy and radiotherapy from January 1992 to January 1997 were evaluated in the Medical Oncology Section of the Veterans Administration Medical Center, Washington, D.C. All patients were staged radiographically and endoscopically. Four patients developed a tracheoesophageal fistula while receiving treatment. One patient developed a fistula before treatment and another patient developed a fistula after treatment. Closure of the tracheoesophageal fistulas was achieved in 4 of 5 patients who responded to therapy and in those who developed fistulas before or during therapy. One of the patients whose fistula did not close died during therapy, whereas the other who developed a fistula after therapy underwent stenting. This finding indicates that development of a tracheoesophageal fistula is not a contraindication to chemotherapy and radiotherapy, and patients who are responsive to therapy may have closure of their fistulas.
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Iqbal MP, Baig JA, Ali AA, Niazi SK, Mehboobali N, Hussain MA. The effects of non-steroidal anti-inflammatory drugs on the disposition of methotrexate in patients with rheumatoid arthritis. Biopharm Drug Dispos 1998; 19:163-7. [PMID: 9569999 DOI: 10.1002/(sici)1099-081x(199804)19:3<163::aid-bdd82>3.0.co;2-l] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We have studied the pharmacokinetics of methotrexate in patients with rheumatoid arthritis concurrently taking the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, diclofenac, naproxen, indomethacin, and ibuprofen. The area under the curve, the total systemic clearance, the distribution volume, and the half-life of methotrexate in patients receiving concurrent NSAID therapy did not change significantly (at p < 0.05). Concurrent treatment with NSAIDs resulted in increased inter-patient variability of methotrexate concentration, possibly as a result of biochemical interactions; however, it does not appear clinically relevant. The data suggest that the NSAIDs do not significantly affect the disposition of methotrexate, contrary to some of the earlier reports.
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Hussain MA, Murali CV, Willi P, Sharma CP, Bhuvneshwar GS, Sreekumar R. Comparative complement activation study of polypropylene hollow fibres of two different makes in static condition. J Biomater Appl 1998; 12:300-20. [PMID: 9615291 DOI: 10.1177/088532829801200403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The complement activation is one of the major problems encountered in the use of extracorporeal devices. The complement-activating potential of two polypropylene hollow fibres (used in membrane oxygenator) of different make and designated as F1 and F2 was tested with time (10, 30, and 180 minutes). The fibres were brought in contact with human blood under in vitro static condition for the comparison. A direct measurement of unadsorbed concentration of the complement protein, C3, present in the liquid phase of human blood before and after the contact with polymer was made using human C3 antisera. This gave a measure of C3 adsorption on the fibres with time and probably also gave an indirect measure of C3a in the blood. IgG was also estimated using antisera of human IgG. The total protein and albumin concentration were measured to obtain an overall adsorption profile of these protein on the fibre surfaces with respect to time. The results showed that C3 adsorption was taking place mainly through the alternative pathway over and above the classical one, being more in the case of F2 than F1. SEM studies revealed poor adhesion of platelets on both fibres, though some activated platelets were also seen with slight deformation at 10 minutes and a few with prominent pseudopodia formations at a later time period on the surface of both fibres. The total protein adsorption was faster, and the surface pores of the F1 were found masked at 10 minutes observation. Later, desorption occurred making the pores visible at 180 minutes. The F2 surface examination showed a continuous deposition of protein layers with time, thereby masking the pores at 180 minutes. The present experimental finding and assessment favoured the F1 as a marginally better candidate to be considered for oxygenator development.
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Hussain MA, Basahy AY. Nutrient composition and amino acid pattern of cowpea (Vigna unguiculata (L.) Walp, Fabaceae) grown in the Gizan area of Saudi Arabia. Int J Food Sci Nutr 1998; 49:117-24. [PMID: 9713582 DOI: 10.3109/09637489809089391] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The proximate composition, grain protein, minerals, amino acid and sugar profiles of Vigna unguiculata (L.) Walp were analyzed. The crude protein was 23%, fat 3.40% and ash 3.60%. Amino acid analysis indicated the presence of at least 17 amino acids including most of the essential ones. The essential amino acids valine, leucine, phenylalanine and lysine were slightly higher, but sulphur-containing amino acids were lower than recommended in the WHO/FAO requirement pattern. Qualitative phytochemical screening of seeds showed fructose, alpha-glucose, beta-glucose, glycerol, manitol, inositol and some oligosaccharides, e.g. raffinose, stachyose, and verbascose. The grain contained almost similar amount of phosphorus as compared with that of Lebanese and Pakistani cultivars. Calcium was found to be lower as compared to some Indian, Pakistani and Lebanese cultivars. In general the results indicated that the legume is nutritive as staple food, feed and/or fodder.
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Chang RK, Hussain MA. Improvement of nalbuphine bioavailability through rectal administration of a prodrug. Pharm Dev Technol 1998; 3:131-4. [PMID: 9532608 DOI: 10.3109/10837459809028487] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Ali AA, Iqbal MP, Hussain MA, Mehboobali N, Beg JA, Rahbar MH. Methotrexate in rheumatoid arthritis: a 2 year experience at a university hospital in Pakistan. J PAK MED ASSOC 1998; 48:3-6. [PMID: 9610077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this study we report our two years experience of methotrexate (MTX) in the management of rheumatoid arthritis (RA) at the Aga Khan University Hospital, Karachi. We studied the clinical course of 124 RA patients. The mean age was 44 +/- 11 years (range 19-72) and mean duration of RA was 5 +/- 4 years (range 0.3-25). Female to male ratio was 10:2.4 (100F:24M). All of them were diagnosed according to the criteria set by American Rheumatism Association. The mean value of ESR was 60 +/- 30 (Range 3-128). Fifty one percent had severe disease (> 10 joints involved and evidence of erosions and deformities). Twenty-one patients had extra-articular manifestations. None of them had received MTX previously. Their kidney and liver functions were assessed to be normal. Patients were divided into two groups. One group (n = 92) received MTX (7.5-10 mg/week) as initial treatment, while the other group (n = 32) was given other disease modifying anti-rheumatic drugs (penicillamine, salazopyrin, gold, or chloroquine) followed by MTX. Assessment of the treatment outcome and development of any adverse reactions was carried out at 3-month interval over an average period of 1 year. Assessment of the treatment outcome in the group which received MTX as initial drug revealed the response to be excellent in 13%, good in 70%, fair in 11% and variable in 4%. In the group which received MTX as second-line of therapy, 59% of the patients had the response from good to excellent, while 25% of the patients exhibited poor to fair response. Regarding side-effects of MTX treatment, 57% exhibited none, while 35% had nausea and vomiting. Alopecia was the next common toxicity in these patients. Two individuals had abnormal liver function tests (value twice more than normal), while one developed lung fibrosis. MTX despite its adverse effects in some of the patients is still an effective, well tolerated and inexpensive disease modifying drug in RA.
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Hussain MA, Lee J, Miller CP, Habener JF. POU domain transcription factor brain 4 confers pancreatic alpha-cell-specific expression of the proglucagon gene through interaction with a novel proximal promoter G1 element. Mol Cell Biol 1997; 17:7186-94. [PMID: 9372951 PMCID: PMC232576 DOI: 10.1128/mcb.17.12.7186] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The proglucagon gene is expressed in a highly restricted tissue-specific manner in the alpha cells of the pancreatic islet, the hypothalamus, and the small and large intestines. Proglucagon is processed to glucagon and glucagon-like peptides GLP-1 and -2. Glucagon is expressed in alpha cells and regulates glucose homeostasis. GLP-1 is implicated in the control of insulin secretion, food intake, and satiety signaling, and GLP-2 is implicated in regulating small-bowel growth. Cell-specific expression of the proglucagon gene is mediated by proteins that interact with the proximal G1 promoter element which contains several AT-rich domains with binding sites for homeodomain transcription factors. In an attempt to identify major homeodomain proteins involved in pancreatic alpha-cell-specific proglucagon expression, we found that the POU domain transcription factor brain 4 is abundantly expressed in proglucagon-producing islet cell lines and rat pancreatic islets. In the latter, brain 4 and glucagon immunoreactivity colocalize in the outer mantle of islets. Electrophoretic mobility shift assays with specific antisera identify brain 4 as a major constituent of nuclear proteins of glucagon-producing cells that bind to the G1 element of the proglucagon gene proximal promoter. Transcriptional transactivation experiments reveal that brain 4 is a major regulator of proglucagon gene expression by its interaction with the G1 element. The finding that a neuronal transcription factor is involved in glucagon gene transcription may explain the presence of proglucagon in certain areas of the brain as well as in pancreatic alpha cells. Further, this finding supports the idea that the neuronal properties of endodermis-derived endocrine pancreatic cells may find their basis in regulation of gene expression by neuronal transcription factors.
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Hussain MA, Aungst BJ, Kapil R, Mousa SA. Intranasal absorption of the platelet glycoprotein IIb/IIIa receptor antagonist, DMP 755, and the effect of anesthesia on nasal bioavailability. J Pharm Sci 1997; 86:1358-60. [PMID: 9423145 DOI: 10.1021/js970208r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Intranasal absorption and bioavailability of DMP 755, a peptidomimetic, platelet glycoprotein IIb/IIIa receptor antagonist, were examined in anesthetized and lightly sedated dogs. Nasal bioavailability was determined by measuring plasma concentrations relative to those after intravenous dosing. DMP 755 is an ester prodrug, and bioavailability reflects concentrations of the acid hydrolysis product. Nasal bioavailability in dogs anesthetized with pentobarbital was 85 +/- 4%, whereas in dogs anesthetized with the short-acting anesthetic propofol, bioavailability was 32 +/- 7%. Nasal bioavailability was greater than the reported oral bioavailability of DMP 755 in dogs, and was quite consistent. Because anesthesia affects nasal bioavailability, an effect that may depend on the absorption half-life of the test compound, a conscious or lightly sedated animal model is preferred.
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Mamun KZ, Tabassum S, Hussain MA, Shears P. Antimicrobial susceptibility of Shigella from a rural community in Bangladesh. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 1997; 91:643-7. [PMID: 9425367 DOI: 10.1080/00034989760743] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Of the 63 Shigella strains isolated from stool cultures from 200 patients who attended a district hospital in Bangladesh with bloody diarrhoea, 37 (59%) were S. dysenteriae type 1, 25 (39%) were S. flexneri and only one (2%) was S. sonnei. Over half (54%) of the Shigella isolates came from children aged < 10 years. Most (89%) of the isolates of S. dysenteriae type 1 were resistant to ampicillin, cotrimoxazole, nalidixic acid, tetracycline and chloramphenicol. Although many (60%) of the isolates of S. flexneri were resistant to ampicillin and cotrimoxazole, only 4% of them were resistant to nalidixic acid. However, all of the S. dysenteriae and S. flexneri were sensitive to ciprofloxacin. The need for periodic monitoring to determine the resistance pattern in remote areas is emphasised.
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Raghavan KS, Chang RK, Pang J, Figuly GD, Hussain MA. Physical and chemical properties of DMP 504, a polyalkylammonium-based bile acid sequestrant. Pharm Dev Technol 1997; 2:233-41. [PMID: 9552451 DOI: 10.3109/10837459709031443] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The purpose of this study was to characterize the physicochemical properties of DMP 504 and lay the foundation for formulation development. Thermal properties were characterized by DSC and TGA and moisture sorption and desorption by TGA. The association rate and equilibrium binding capacity of the polymer for a prototype bile acid was evaluated using cholic acid, and solid state stability was examined at 25 degrees C, 40 degrees C (with and without 5% added water), 60 degrees C, and 600 foot candles/25 degrees C. The solid state excipient compatibility of binary mixtures of DMP 504 and several commonly used pharmaceutical excipients was also evaluated. Thermal analysis of the polymer showed a glass transition temperature at approximately 95 degrees C and no melting point, indicating a highly amorphous macromolecular structure with thermal stability up to 250 degrees C. Moisture sorption and desorption isotherms at controlled humidity ranging from 11% to 97% RH did not display hysteresis. Cholic acid associated with DMP 504 extremely rapidly so that binding was essentially complete within 5 min. Scatchard analysis of the equilibrium binding of cholic acid to DMP 504 was unconventional, and indicated that the system was exhibiting positive cooperative behavior. Modeling the binding curve for a system exhibiting cooperative behavior indicated a maximum binding capacity of DMP 504 for cholic acid in phosphate buffered saline (pH 7.0) of 4.9 mumol/mg, and a cooperativity value, P, of 2.2 implying that binding of one molecule promotes the binding of additional molecules. DMP 504, a hygroscopic, amorphous cross-linked polymer with a tendency to gain or lose moisture with ease, is stable in the solid state, either drug substance alone or in presence of excipients, at normal storage temperatures and light, and under controlled conditions of humidity.
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Abstract
The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.
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Wascher TC, Graier WF, Dittrich P, Hussain MA, Bahadori B, Wallner S, Toplak H. Effects of low-dose L-arginine on insulin-mediated vasodilatation and insulin sensitivity. Eur J Clin Invest 1997; 27:690-5. [PMID: 9279534 DOI: 10.1046/j.1365-2362.1997.1730718.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present study was carried out to evaluate the effect of a low-dose intravenous supplementation of L-arginine on insulin-mediated vasodilatation and insulin sensitivity. The study was performed in healthy subjects (n = 7) and patients with obesity (n = 9) and non-insulin-dependent diabetes mellitus (NIDDM) (n = 9). Insulin-mediated vasodilatation was measured by venous occlusion plethysmography during the insulin suppression test, evaluating insulin sensitivity. Experiments were performed twice in each subject in the presence or absence of a concomitant infusion of L-arginine (0.52 mg kg-1 min-1). L-Arginine restored the imparied insulin-mediated vasodilatation observed in obesity (22.4 +/- 4.1%, P < 0.01 vs. without L-arginine) and NIDDM (20.3 +/- 3.2%, P < 0.01 vs. without L-arginine). In healthy subjects, no effect on insulin mediated-vasodilatation was observed (24.8 +/- 3.1% vs. 21.4 +/- 3.1%). Insulin sensitivity was improved significantly (P < 0.001) in all three groups by infusion of L-arginine. No effect of L-arginine was observed on insulin, insulin-like growth factor I (IGF-I), free fatty acids (FFAs) or C-peptide levels during the insulin suppression test. Our data indicate that defective insulin-mediated vasodilatation in obesity and NIDDM can be normalized by intravenous L-arginine. Furthermore, L-arginine improves insulin sensitivity in obese patients and NIDDM patients as well as in healthy subjects, indicating a possible mechanism that is different from the restoration of insulin-mediated vasodilatation.
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Sharma D, Krasnow SH, Davis EB, Lunzer S, Hussain MA, Wadleigh RG. Sequential chemotherapy and radiotherapy for squamous cell esophageal carcinoma. Am J Clin Oncol 1997; 20:151-3. [PMID: 9124189 DOI: 10.1097/00000421-199704000-00009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A Phase II study of sequential chemotherapy with 5-fluorouracil and cisplatin followed by radiotherapy was initiated to see whether the use of two therapies sequentially could have an effect on response rate. Thirteen patients with advanced squamous cell carcinoma of the esophagus were treated with 1,000 mg/m2/day 5-fluorouracil days 1-5 continuously and 100 mg/m2 cisplatin on day 1. An average of four cycles (range, one to nine) were given every 28 days; 11 patients received more than three cycles. The radiation consisted of 60 Gy over 6-8 weeks. There was only one (8%) complete response (CR) and 11 (85%) partial responses (PRs). Restaging after radiation revealed no conversion of PR to CR. Median survival was 39 weeks (range, 6-208+). Chemotherapy alone or its use sequentially with radiotherapy is inadequate, and newer approaches are needed to to improve survival.
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Hussain MA. Upstream of Randle. Eur J Endocrinol 1997; 136:273-4. [PMID: 9100551 DOI: 10.1530/eje.0.1360273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Pørksen N, Hussain MA, Bianda TL, Nyholm B, Christiansen JS, Butler PC, Veldhuis JD, Froesch ER, Schmitz O. IGF-I inhibits burst mass of pulsatile insulin secretion at supraphysiological and low IGF-I infusion rates. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:E352-8. [PMID: 9124538 DOI: 10.1152/ajpendo.1997.272.3.e352] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Insulin-like growth factor I (IGF-I) shares structural and functional features with insulin, affects carbohydrate metabolism, and inhibits insulin secretion. Insulin secretion is pulsatile, and it is regulated by changing frequency and/or mass of secretory bursts. To examine the mechanism of IGF-I's inhibition of insulin secretion, eight healthy volunteers were studied three times. During glucose infusion (2.5 mg x kg(-1) x min(-1)) blood was sampled minutely at time 75-200 min for triplicate insulin concentration measurements by enzyme-linked immunosorbent assay (ELISA; coefficient of variation 2.1%). Time 125 min infusion of saline, low-dose IGF-I (0.025 microg x kg(-1) x min(-1)) or high-dose IGF-I (0.15 microg x kg(-1) x min(-1)) was commenced and continued until 200 min. Data were compared before (75-125 min) vs. during infusion (150-200 min). Insulin concentration time series were deconvolved, using validated pulse-detection criteria, to assess insulin secretory burst mass and frequency. During saline infusion no time effect occurred. After IGF-I infusion, serum C-peptide decreased (582 +/- 85 vs. 481 +/- 82 pM, low-dose IGF-I, P < 0.05; 539 +/- 84 vs. 427 +/- 69 pM, high-dose IGF-I, P < 0.01). Total insulin secretion rates decreased by 17 and 21%, respectively, via specific inhibition of the insulin secretory burst mass (31 +/- 8 vs. 20 +/- 4 pmol/ml, low-dose IGF-I, P = 0.06; 22 +/- 4 vs. 17 +/- 3 pmol/ml, high-dose IGF-I, P < 0.05), whereas the frequency was not affected (10.5 +/- 1.3 vs. 10.7 +/- 1.3 pulses/h, low-dose IGF-I, P = 0.85; 8.7 +/- 1.0 vs. 11.1 +/- 1.2 min/pulse, high-dose IGF-I, P = 0.15). We conclude that IGF-I inhibits pulsatile insulin secretion by specific inhibition of mass but not frequency of secretory bursts.
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Bianda T, Hussain MA, Glatz Y, Bouillon R, Froesch ER, Schmid C. Effects of short-term insulin-like growth factor-I or growth hormone treatment on bone turnover, renal phosphate reabsorption and 1,25 dihydroxyvitamin D3 production in healthy man. J Intern Med 1997; 241:143-50. [PMID: 9077371 DOI: 10.1046/j.1365-2796.1997.94101000.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVES To find out whether insulin-like growth factor-I (IGF-I) mimics the stimulatory effects of growth hormone (GH) on bone turnover and renal tubular phosphate reabsorption. DESIGN Randomized, crossover study. SETTING University Hospital, Zürich, Switzerland. SUBJECTS Seven young healthy male subjects. INTERVENTIONS Each subject was studied three times at 2-week intervals, treated with saline 0.9% (S), IGF-I [8 micrograms kg-1 h-1] by a continuous subcutaneous infusion and finally with GH (6 U. twice daily s.c.) for 5 days. MAIN OUTCOME MEASURES 36 h after the start of treatment, IGF-I, biochemical markers of bone turnover, calcium, calcium regulating hormones, kidney function and phosphate reabsorption were measured in serum and in 2 h urine in fasting state. RESULTS Serum levels of IGF-I were 26.8 +/- 7.3 (S), 119.4 +/- 11.4 (IGF-I) (P < 0.02) and 58.4 +/- 12.9 nmol L-1 (GH) (P < 0.02), respectively. Serum osteocalcin and carboxyterminal propeptide of type I collagen (PICP) as well as the urinary deoxypyridinoline/creatinine and the calcium/ creatinine ratios were all significantly higher after IGF-I (P < 0.02) or GH (P < 0.02) than after saline treatment. PTH levels did not change in response to treatment. Total albumin-corrected calcium increased only after GH treatment (P < 0.05). The free calcitriol index rose from 2.2 +/- 0.5 x 10(-5) (S) to 2.81 +/- 0.25 x 10(-5) (IGF-I) (P < 0.03) and 2.45 +/- 0.25 x 10(-5) (GH), respectively. Serum phosphate and maximal tubular reabsorption divided by glomerular filtration rate (TmP/GFR) were significantly raised by GH (P < 0.03) but not by IGF-I as compared to saline 0.9%. CONCLUSIONS (i) Similar to GH, IGF-I rapidly activates bone turnover. (ii) IGF-I does not mimic the effect of GH on renal phosphate reabsorption in spite of comparable effects on renal blood flow and glomerular filtration rate. (iii) IGF-I increases free calcitriol index in face of unchanged serum levels of calcium, phosphate and PTH, consistent with a direct stimulatory effect on 25-OHD-1a-hydroxylase.
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Raghavan KS, Gray DB, Scholz TH, Nemeth GA, Hussain MA. Degradation kinetics of DMP 777, an elastase inhibitor. Pharm Res 1996; 13:1815-20. [PMID: 8987077 DOI: 10.1023/a:1016076907072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE The objective was to evaluate the degradation profile of the elastase inhibitor DMP 777 and lay the foundation for formulation development. METHODS The pKa was determined by potentiometric titration in mixed-aqueous solvents. The degradation kinetics were studied as a function of pH, buffer concentration, ionic strength, methanol concentration and temperature using a stability-indicating HPLC assay. The degradation products were identified by LC-MS, NMR, and by comparison with authentic samples. RESULTS The pKa for the protonated piperazine nitrogen was estimated to be 7.04. The pH-rate profile is described by specific acid-, water-, and specific base-catalyzed pathways. The pH of maximum stability is in the range of 4 to 4.5 where water is the principal catalyst in the reaction. Buffer catalysis, primary salt effects and medium effects were observed. The proposed mechanism for acid catalyzed degradation is the rarely observed AAL1 which involves alkyl-nitrogen heterolysis. The driving force for the reaction appears to lie in the stability of the benzylic carbocation. The proposed mechanism for base catalyzed degradation is BAC2 which involves beta-lactam ring opening. The beta-lactam ring of DMP 777, a monolactam, appears to be as reactive as that in benzylpenicillin in the KOH controlled region where a similar mechanism of hydrolysis should be operative. A contributing factor to this increased reactivity may lie in the reduced basicity of the beta-lactam nitrogen making it a good leaving group. CONCLUSIONS The degradation profile indicates that development of a solution dosage form of DMP 777 with adequate shelf-life stability at room temperature is feasible.
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