Photooxidation of acyclovir in aqueous solution

Photodegradation of an aqueous solution of acyclovir in phosphate buffer (pH 7) under aerobic conditions was studied with light of wavelength > 270 nm. Three major products were isolated and identified on the basis of IR, NMR and mass spectral studies. The products are: (2-hydroxyethoxy)methyl spiroiminodihydantoin (2), (2-hydroxyethoxy)methyl(amino)-2-imino-1,2-dihydroimidazole-5-one (3), and 2,2-diamino-4-[(2-hydroxyethoxy)methyl]amino)-5-[2H]-oxazolone (4). Furthermore the effects of D2O as reaction medium, addition of sodium azide and absence of oxygen on the photodegradation of acyclovir were examined, the observations indicating the involvement of singlet oxygen. The formation of the products is explained by the photooxidation of acyclovir.

The risk of venous thromboembolic disease in patients with monoclonal gammopathy of undetermined significance

BACKGROUND

Recent evidence indicates that patients with multiple myeloma receiving combination chemotherapy containing thalidomide are at a significantly high risk for venous thromboembolic disease (VTD). However, information on the occurrence of VTD in a related disorder, benign monoclonal gammopathy of undetermined significance (MGUS), is limited.

PATIENTS AND METHODS

We prospectively investigated patients with MGUS for the occurrence of VTD. The diagnosis of MGUS was based on well known criteria for the disorder. The variables examined were sex, age, race, presence of underlying conditions, level and type of immunoglobulin [serum monoclonal (M)-protein] platelet counts and level of fibrinogen.

RESULTS

Of a total of 310 patients with MGUS, 19 (6.1%) developed VTD after a median follow-up of 44 months (range 12-67 months). In a univariate analysis, age >/=65 years (P=0.01), M-protein >/=16 g/l (P=0.001) and progression to plasma cell or lymphoproliferative disorders (28 of 310 patients; P=0.001) were significant risk factors for VTD. In multivariate analysis, M-spike >/=16 g/l [risk ratio (RR)=6.3; 95% confidence interval (CI) 2.25-17.6; P=0.001] and future development of plasma cell or lymphoproliferative disorder (RR = 4.2; 95% CI 1.64-10.7; P=0.003) were variables strongly associated with the occurrence of VTD. A total of 46 patients (14.8%) died during the follow-up period of the study.

CONCLUSION

This study demonstrates that patients with MGUS are at increased risk for VTD. Although a clear reason for the pre-thrombotic state in these patients is not currently evident, few risk factors were identified in the group of patients examined.

Impact of diverticular disease on hospital costs and activity

BACKGROUND

Diverticulosis is very common in the UK and patients with clinically significant diverticular disease present regularly to departments of surgery as acute emergencies or chronic problems. There are no national data on the hospital prevalence, clinical implications or financial impact of diverticular disease hence the extent of the clinical problem is as yet not quantified.

AIM

To detect the prevalence, clinical implications and financial impact of diverticular disease over a one year period in a large district hospital.

METHODS

Retrospective review of all patients treated for diverticular disease during one financial year. Clinical and cost analysis of inpatient and outpatient investigations, treatment and hospitalization.

RESULTS

A total of 148 patients were treated of whom 83 were admitted for more than 1 day, 55 of those were emergency admissions. Five of 83 admitted patients died (in-patient mortality 6%, peri-operative mortality 26.3%). There was a total number of 982 hospitalization days of which 94 Intensive Care Unit days and 68 High Dependency Unit days. Nineteen operations were performed (16 sigmoid colectomies, 1 oversewing of perforated sigmoid, 2 reversal of colostomy). The investigations generated were 48 colonoscopies, 77 flexible sigmoidoscopies, 77 Barium enemas, 2 CT scans and 34 ultrasound scans. A total number of 410 clinic appointments were generated. One year after discharge 134/148 (90.5%) patients were alive. The total cost of this activity was pound 465263 or 5.3% of the total annual budget for General Surgery. Seventy percent of the cost was bed-days expenses with ICU hospitalization accounting for 25% of the total cost.

CONCLUSION

Diverticular disease is a major cause of morbidity in a large district hospital and a significant burden on resources. More research should be done on prevention of complications and management in the community. The current methods of management do not appear to be cost-effective and attempts should be made to produce protocols for evidence-based, cost-efficient management of the disease. A UK national audit should be undertaken.

Syntheses and reactions of some new 2-arylidene-4-(biphenyl-4-yl)-but-3-en-4-olides with a study of their biological activity

2-Arylidene-4-(biphenyl-4-yl)but-3-en-4-olides also known as 3-arylidene-5-(biphenyl-4-yl)-2(3H)-furanones were prepared from 3-(4-phenyl-benzoyl) propionic acid and aromatic aldehydes. Some of the selected butenolides were reacted with ammonia and benzylamine to give corresponding pyrrolones and N-benzylpyrrolones respectively, which were characterized on the basis of 1H NMR and MS data and elemental analysis results. These compounds were tested for anti-inflammatory and anti-microbial actions. A few compounds were found to have promising anti-inflammatory activity while a fair in number of compounds showed a good anti-fungal activity and a promising antibacterial activity against S. aureus and E. coli.

Changes in zinc ligation promote remodeling of the active site in the zinc hydrolase superfamily

The zinc hydrolase superfamily is a group of divergently related proteins that are predominantly enzymes with a zinc-based catalytic mechanism. The common structural scaffold of the superfamily consists of an eight-stranded beta-sheet flanked by six alpha-helices. Previous analyses, while acknowledging the likely divergent origins of leucine aminopeptidase, carboxypeptidase A and the co-catalytic enzymes of the metallopeptidase H clan based on their structural scaffolds, have failed to find any homology between the active sites in leucine aminopeptidase and the metallopeptidase H clan enzymes. Here we show that these two groups of co-catalytic enzymes have overlapping dizinc centers where one of the two zinc atoms is conserved in each group. Carboxypeptidase A and leucine aminopeptidase, on the other hand, no longer share any homologous zinc-binding sites. At least three catalytic zinc-binding sites have existed in the structural scaffold over the period of history defined by available structures. Comparison of enzyme-inhibitor complexes show that major remodeling of the substrate-binding site has occurred in association with each change in zinc ligation in the binding site. These changes involve re-registration and re-orientation of the substrate. Some residues important to the catalytic mechanism are not conserved amongst members. We discuss how molecules acting in trans may have facilitated the mutation of catalytically important residues in the active site in this group.

The relevance of tissue angiotensin-converting enzyme: manifestations in mechanistic and endpoint data

Angiotensin-converting enzyme (ACE) is primarily localized (>90%) in various tissues and organs, most notably on the endothelium but also within parenchyma and inflammatory cells. Tissue ACE is now recognized as a key factor in cardiovascular and renal diseases. Endothelial dysfunction, in response to a number of risk factors or injury such as hypertension, diabetes mellitus, hypercholesteremia, and cigarette smoking, disrupts the balance of vasodilation and vasoconstriction, vascular smooth muscle cell growth, the inflammatory and oxidative state of the vessel wall, and is associated with activation of tissue ACE. Pathologic activation of local ACE can have deleterious effects on the heart, vasculature, and the kidneys. The imbalance resulting from increased local formation of angiotensin II and increased bradykinin degradation favors cardiovascular disease. Indeed, ACE inhibitors effectively reduce high blood pressure and exert cardio- and renoprotective actions. Recent evidence suggests that a principal target of ACE inhibitor action is at the tissue sites. Pharmacokinetic properties of various ACE inhibitors indicate that there are differences in their binding characteristics for tissue ACE. Clinical studies comparing the effects of antihypertensives (especially ACE inhibitors) on endothelial function suggest differences. More comparative experimental and clinical studies should address the significance of these drug differences and their impact on clinical events.

Studies on 3-deoxy-D-manno-octulosonic acid 8-phosphate synthase using chorismate mutase inhibitors

The proposed cyclic mechanism of 3-deoxy-D-manno-octulosonic acid 8-phosphate synthase and the mechanism of chorismate mutase share certain structural and electronic similarities. In this report, we examine several inhibitors of chorismate mutase for their efficacy against KDO 8-P synthase.

A selective inhibitor of Escherichia coli prephenate dehydratase

To identify selective prephenate dehydratase (PDT) inhibitors, a series of substituted biphenic acid derivatives was synthesized using the Ullmann reaction. Screening experiments identified 18 as a promising new PDT inhibitor.

Arg(1098) is critical for the chloride dependence of human angiotensin I-converting enzyme C-domain catalytic activity

Angiotensin (Ang) I-converting enzyme (ACE) is a Zn(2+) metalloprotease with two homologous catalytic domains. Both the N- and C-terminal domains are peptidyl dipeptidases. Hydrolysis by ACE of its decapeptide substrate Ang I is increased by Cl(-), but the molecular mechanism of this regulation is unclear. A search for single substitutions to Gln among all conserved basic residues (Lys/Arg) in human ACE C-domain identified R1098Q as the sole mutant that lacked Cl(-) dependence. Cl(-) dependence is also lost when the equivalent Arg in the N-domain, Arg(500), is substituted with Gln. The Arg(1098) to Lys substitution reduced Cl(-) binding affinity by approximately 100-fold. In the absence of Cl(-), substrate binding affinity (1/K(m)) of and catalytic efficiency (k(cat)/K(m)) for Ang I hydrolysis are increased 6.9- and 32-fold, respectively, by the Arg(1098) to Gln substitution, and are similar (<2-fold difference) to the respective wild-type C-domain catalytic constants in the presence of optimal [Cl(-)]. The Arg(1098) to Gln substitution also eliminates Cl(-) dependence for hydrolysis of tetrapeptide substrates, but activity toward these substrates is similar to that of the wild-type C-domain in the absence of Cl(-). These findings indicate that: 1) Arg(1098) is a critical residue of the C-domain Cl(-)-binding site and 2) a basic side chain is necessary for Cl(-) dependence. For tetrapeptide substrates, the inability of R1098Q to recreate the high affinity state generated by the Cl(-)-C-domain interaction suggests that substrate interactions with the enzyme-bound Cl(-) are much more important for the hydrolysis of short substrates than for Ang I. Since Cl(-) concentrations are saturating under physiological conditions and Arg(1098) is not critical for Ang I hydrolysis, we speculate that the evolutionary pressure for the maintenance of the Cl(-)-binding site is its ability to allow cleavage of short cognate peptide substrates at high catalytic efficiencies.

Oral tuberculosis

Although rare, doctors and dentists should be aware of the possible occurrence of oral lesions of tuberculosis and consider them in the differential diagnosis of suspicious oral ulcers.

Targeted inactivation of Gh/tissue transglutaminase II

The novel G-protein, G(h)/tissue transglutaminase (TGase II), has both guanosine triphosphatase and Ca(2+)-activated transglutaminase activity and has been implicated in a number of processes including signal transduction, apoptosis, bone ossification, wound healing, and cell adhesion and spreading. To determine the role of G(h) in vivo, the Cre/loxP site-specific recombinase system was used to develop a mouse line in which its expression was ubiquitously inactivated. Despite the absence of G(h) expression and a lack of intracellular TGase activity that was not compensated by other TGases, the Tgm2(-/-) mice were viable, phenotypically normal, and were born with the expected Mendelian frequency. Absence of G(h) coupling to alpha(1)-adrenergic receptor signaling in Tgm2(-/-) mice was demonstrated by the lack of agonist-stimulated [alpha-(32)P]GTP photolabeling of a 74-kDa protein in liver membranes. Annexin-V positivity observed with dexamethasone-induced apoptosis was not different in Tgm2(-/-) thymocytes compared with Tgm2(+/+) thymocytes. However, with this treatment there was a highly significant decrease in the viability (propidium iodide negativity) of Tgm2(-/-) thymocytes. Primary fibroblasts isolated from Tgm2(-/-) mice also showed decreased adherence with culture. These results indicate that G(h) may be importantly involved in stabilizing apoptotic cells before clearance, and in responses such as wound healing that require fibroblast adhesion mediated by extracellular matrix cross-linking.

Angiotensin I-converting enzyme transition state stabilization by HIS1089: evidence for a catalytic mechanism distinct from other gluzincin metalloproteinases

Angiotensin (Ang) I-converting enzyme (ACE) is a member of the gluzincin family of zinc metalloproteinases that contains two homologous catalytic domains. Both the N- and C-terminal domains are peptidyl-dipeptidases that catalyze Ang II formation and bradykinin degradation. Multiple sequence alignment was used to predict His(1089) as the catalytic residue in human ACE C-domain that, by analogy with the prototypical gluzincin, thermolysin, stabilizes the scissile carbonyl bond through a hydrogen bond during transition state binding. Site-directed mutagenesis was used to change His(1089) to Ala or Leu. At pH 7.5, with Ang I as substrate, k(cat)/K(m) values for these Ala and Leu mutants were 430 and 4,000-fold lower, respectively, compared with wild-type enzyme and were mainly due to a decrease in catalytic rate (k(cat)) with minor effects on ground state substrate binding (K(m)). A 120,000-fold decrease in the binding of lisinopril, a proposed transition state mimic, was also observed with the His(1089) --> Ala mutation. ACE C-domain-dependent cleavage of AcAFAA showed a pH optimum of 8.2. H1089A has a pH optimum of 5.5 with no pH dependence of its catalytic activity in the range 6.5-10.5, indicating that the His(1089) side chain allows ACE to function as an alkaline peptidyl-dipeptidase. Since transition state mutants of other gluzincins show pH optima shifts toward the alkaline, this effect of His(1089) on the ACE pH optimum and its ability to influence transition state binding of the sulfhydryl inhibitor captopril indicate that the catalytic mechanism of ACE is distinct from that of other gluzincins.

The role of laparoscopy in second-look evaluations for ovarian cancer

BACKGROUND

The aim of this study was to evaluate the accuracy and safety of laparoscopic second-look operations in patients with ovarian cancer.

METHODS

We retrospectively reviewed the medical records of all patients who have undergone laparoscopic second-look procedures for ovarian cancer at our institution.

RESULTS

From July 1993 to December 1998, 150 patients underwent laparoscopic second-look operations. The mean age of patients was 53 years (range, 25-78 years). The majority of patients (87%) had Stage III or IV disease at initial surgery; the remainder were Stage II or unstaged. Eighty-two patients (54%) had had optimal cytoreduction at the time of their initial surgery. All patients had completed primary chemotherapy and were clinically disease-free based on imaging studies and CA-125 levels at the time of second look. Sixty-nine patients (46%) were found to have pathologically negative second looks; thus, the rate of positive second-look evaluations was 54%. The rate of conversion to laparotomy was 18/150 (12%). In 3 cases this was secondary to bowel injury; one patient sustained a bladder injury; the remainder of conversions to laparotomy were for secondary cytoreduction. There was only 1 case where the patient was found to have extensive adhesions and laparoscopy was abandoned. The overall rate of major complications was 2.7%.

CONCLUSIONS

In our experience, laparoscopy is a safe and accurate method of second-look assessment in patients with ovarian cancer. The incidence of complications is low, particularly in this group of patients, all of whom have undergone prior abdominal surgery. The rate of negative evaluations and the rate of recurrences in patients with negative second looks are equivalent to those described in studies of second-look assessment by laparotomy.

Continent urinary diversion and low-rectal anastomosis in patients undergoing exenterative procedures for recurrent gynecologic malignancies

OBJECTIVE

The aim of this study was to review the complications associated with continent urinary diversion and associated procedures in patients with gynecologic malignancies.

METHODS

We retrospectively reviewed the medical records of all patients who underwent construction of a continent urinary conduit between October 1991 and October 1998 on the Gynecology Service at Memorial Sloan-Kettering Cancer Center.

RESULTS

Thirty-three patients were identified, of whom 22 underwent total pelvic exenteration, 8 underwent anterior exenteration, and 3 underwent urinary diversion procedures only. Complications associated with the urinary diversion procedure included ureteral strictures (2), pouch leakage (2), mild hydronephrosis, (6), pyelopnephritis (2), nocturnal incontinence (5), and difficulty with self-catheterization (2). Additional procedures performed concomitantly with continent urinary diversion and exenteration included pelvic reconstruction (18), low-rectal anastomosis (13), and intraoperative radiation therapy (9). The most significant morbidity was seen in patients undergoing concomitant low-rectal anastomosis, in whom the rate of anastomotic leaks was 54% (7 of 13 patients).

CONCLUSIONS

Continent urinary diversion can successfully be accomplished at the time of exenteration in patients with recurrent gynecologic malignancies. The rate of major complications related to the urinary diversion is small and most complications can be managed nonsurgically. The greater than 50% rate of anastomotic leaks in patients undergoing concomitant low-rectal anastamosis suggests that such anastomosis should not be undertaken in this group of patients.

Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis

AIMS

To describe the clinical and histopathological features of a rare variant of naevoid melanoma, small cell melanoma, and discuss the histological differential diagnoses.

METHODS

The clinical and histological features of cases of malignant melanoma with the histological features of small (non-Merkel like) melanoma were reviewed and documented. In addition, five cases had available material for immunohistochemistry and this was performed using antibodies to the S100 protein and melan-A, and the HMB-45 antibody.

RESULTS

There were 15 cases of small cell melanoma from 14 (10 female, four male) patients, aged between 30 and 77 (mean, 48.6) years. The trunk was the most common location. In more than half the cases, the provisional diagnosis was melanoma/borderline lesion. All shared similar histological appearances of an intraepidermal component of in situ melanoma and a dermal component of nests of cells with hyperchromatic nuclei and scanty cytoplasm, usually in tightly packed nests. All components (junctional and intradermal) of the lesions investigated by immunohistochemistry were positive both for S100 protein and melan-A. All junctional components were positive with HMB-45, but with variable staining of the dermal components with this antibody.

CONCLUSIONS

Small cell malignant melanoma is postulated to be a distinct histopathological entity and a rare variant of naevoid melanoma. Such lesions can be difficult to interpret and easily missed at scanning magnification because the cells of the dermal component mimic benign naevus cells.