Biomedical subjects

J S Dixon

Publications and source records attributed to J S Dixon.

At least 19 recordsLinked to original sources

PubMed1996

Nitric oxide synthase and tyrosine hydroxylase are colocalized in nerves supplying the postnatal human male genitourinary organs.

PURPOSE: The objective of this study was to examine the distribution of nitric oxide synthase (NOS) and the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in nerve fibers supplying the human neonatal male genitourinary organs. MATERIALS AND METHODS: An indirect double label immunofluorescence technique was employed on specimens obtained from infants and children at postmortem examination. RESULTS: Many nerve fibers immunoreactive for both NOS and TH were observed in the muscle coat of the vas deferens and the seminal vesicle, within the fibromuscular stroma of the prostate gland and at the bladder neck, and also formed perivascular plexuses in each of these organs. Double-labeled nerves occurred less frequently in the intramural ureters and superficial trigone while similar nerves in the bladder body were relatively sparse. Numerous nerves immunoreactive for NOS but not TH were observed at the base of the epithelium of each organ examined. Four types of autonomic ganglion cell were observed in nearby pelvic ganglia: those which contained NOS and TH, those which contained NOS alone, those which contained TH alone and those which contained neither NOS nor TH. CONCLUSION: The results indicate that many of the noradrenergic nerves as well as non-noradrenergic nerves supplying the male genitourinary organs have the capacity to synthesize nitric oxide (NO) and that NO may play a significant role in the autonomic control of both the urinary and genital organs in the postnatal human male.

Cadaver↗

PubMed1995

Flexible ligand docking using a genetic algorithm.

Two computational techniques have been developed to explore the orientational and conformational space of a flexible ligand within an enzyme. Both methods use the Genetic Algorithm (GA) to generate conformationally flexible ligands in conjunction with algorithms from the DOCK suite of programs to characterize the receptor site. The methods are applied to three enzyme-ligand complexes: dihydrofolate reductase-methotrexate, thymidylate synthase-phenolpthalein and HIV protease-thioketal haloperidol. Conformations and orientations close to the crystallographically determined structures are obtained, as well as alternative structures with low energy. The potential for the GA method to screen a database of compounds is also examined. A collection of ligands is evaluated simultaneously, rather than docking the ligands individually into the enzyme.

Algorithms↗

PubMed1995

Development of nerves containing nitric oxide synthase in the human male urogenital organs.

OBJECTIVE: To determine the spatial and temporal distribution of nitric oxide synthase (NOS) in the urogenital organs of a series of human male fetuses, using an immunohistochemical technique. MATERIAL AND METHODS: Thirteen pre-natal specimens ranging in gestational age from 13 to 30 weeks were acquired following abortion or miscarriage. The distribution of NOS, which catalyses the production of nitric oxide (NO), was revealed using an indirect immunolabelling technique and compared with the overall innervation of each specimen visualized using the general nerve-marker protein gene product 9.5 (PGP). RESULTS: At 13 weeks of gestation the majority of nerves supplying the developing prostate gland expressed NOS while similar nerves formed a very minor proportion of the total innervation to the urinary bladder and intramural ureters. With increasing gestational age, NOS-containing nerves became more numerous in the lower urinary tract, the majority occurring at the bladder neck and around the prostatic urethra. In contrast, NOS-containing nerves were not detected in the muscle coat of the vas deferens and seminal vesicle until 23 weeks of gestation and at 30 weeks still only formed a small proportion of the intramuscular nerves. From 23 weeks onwards NOS-containing nerves were present occasionally in the dense subepithelial nerve plexuses which developed in the bladder, prostate, vas deferens and seminal vesicle. Also from 23 weeks onwards, many of the epithelial cells lining the vas deferens, seminal vesicle and ejaculatory ducts showed immunoreactivity to NOS but no immunoreactivity was observed in the epithelial lining of the urinary bladder and the intramural ureters. CONCLUSION: Based on the comparative density of NOS-containing nerves and the difference in their temporal development among the various urogenital organs it is apparent that NO plays an increasingly important role in the autonomic control of the lower urinary tract during fetal development but that its involvement in the functional control of the vas deferens and seminal vesicle is relatively minor before birth.

Autonomic Pathways↗

PubMed1995

Immunohistochemical localization of neuromarkers and neuropeptides in human fetal and neonatal urinary bladder.

OBJECTIVE: To use immunohistochemical techniques to determine the spatial and temporal distribution of a variety of neuropeptides in the human fetal and neonatal urinary bladder. MATERIALS AND METHODS: Thirteen pre-natal specimens ranging in gestational age from 17 to 35 weeks were acquired following abortion or miscarriage. In addition two post-natal specimens aged 8 and 12 weeks were obtained at post-mortem and were included in this study. The overall innervation of each specimen was visualized using the general nerve marker protein gene product 9.5 (PGP). Localization of dopamine-beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) revealed putative noradrenergic nerves. The neuropeptides studied included neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP). RESULTS: At 17 weeks a rich plexus of PGP and NPY-containing nerves was present throughout the detrusor muscle coat. As gestational age increased, VIP, SP and CGRP-containing nerves were observed with increasing frequency although SP and CGRP were mainly confined to perivascular nerve plexuses. TH- and DBH-containing nerves were first observed in the intramural ureters at 30 weeks and the detrusor muscle at 35 weeks and were relatively numerous in the intramural ureters and muscle of the superficial trigone in the two post-natal specimens. PGP-containing nerves were first observed beneath the bladder epithelium at 23 weeks and gradually became more numerous with increasing age. Occasional NPY, VIP, SP and CGRP-containing nerves were observed in the submucosa but TH- and DBH-immunostained nerves were especially numerous in the mucosa of the trigone in the two post-natal specimens, many such nerves being unrelated to the vascular supply. CONCLUSIONS: The bladder detrusor possesses a rich autonomic innervation by 17 weeks of gestation and this presumptive cholinergic innervation is associated with NPY immunoreactivity. Presumptive noradrenergic nerves appear relatively late in pre-natal development and mainly supply the intramural ureters and superficial trigone. A submucosal plexus of nerves has been demonstrated, the functional significance of which remains uncertain.

Calcitonin Gene-Related Peptide↗

PubMed1995

Development of peptide-containing nerves in the human fetal vas deferens and seminal vesicle.

OBJECTIVE: To use immunohistochemical methods to study the developing autonomic innervation of the human fetal vas deferens and seminal vesicle. MATERIAL AND METHODS: Thirteen pre-natal specimens ranging in gestational age from 13 to 30 weeks were acquired following abortion or miscarriage. The overall innervation of each specimen was visualized using protein gene product 9.5 (PGP), a general nerve marker, while the onset and development of specific neuropeptide-containing sub-populations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene related peptide (CGRP), bombesin (BOM), somatostatin (SOM), and met-enkephalin (ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH). RESULTS: At 13 weeks numerous PGP, D beta H, TH, NPY and ENK immunoreactive (-IR) nerve trunks were present in the adventitia of the vas deferens and seminal vesicle but at this stage nerve fibres were not present in the smooth muscle coat of either organ. By 17 weeks, fine PGP-, D beta H, and TH-IR nerve fibres had penetrated the outer aspect of the muscle coat of the seminal vesicle but not the vas deferens. At 20 weeks a branching network of PGP-, D beta H- and TH-IR nerve fibres occurred throughout the full thickness of the muscle coat of the seminal vesicle while similar nerves were present only in the outer half of the muscle coat of the vas deferens. At 23 weeks the full thickness of the muscle coat of the vas deferens was richly innervated by a branching plexus of PGP-IR nerves. Many of these adventitial and intramuscular nerves were immunoreactive for D beta H or TH while some were immunoreactive for either NPY or ENK. Occasional adventitial nerves were immunoreactive for SP or CGRP, these being first observed at 20 weeks. VIP-IR nerves were extremely rare in the muscle coat of either organ, being first observed at 17 weeks in the seminal vesicle and at 20 weeks in the vas deferens where they mainly formed perivascular plexuses. PGP-IR nerves were first observed in the submucosa of the seminal vesicle at 20 weeks and in the vas deferens at 21 weeks. Some of these nerves were perivascular in location while other formed a subepithelial plexus which increased in density with increasing gestational age. At 22 weeks of gestation some of the submucosal nerves were immunoreactive for SP or NPY, while at 30 weeks NPY-IR nerves formed the majority of subepithelial nerves. Occasional VIP-IR subepithelial nerves were first observed at 26 weeks but were extremely rare even at 30 weeks. Submucosal nerves immunoreactive for CGRP, D beta H, TH or ENK did not occur in any of the specimens examined. CONCLUSION: (i) From 13 weeks gestation autonomic nerves develop in the muscle coat of the fetal seminal vesicle and vas deferens, being denser in the seminal vesicle than the vas deferens up to 23 weeks gestation. (ii) The majority of the intramuscular nerves in either organ contain D beta H, TH, NPY and ENK and are presumably noradrenergic in type. (iii) A subepithelial nerve plexus develops around 20 weeks gestation and contains NPY but not VIP, unlike the adult organs. (iv) Scattered neuroendocrine cells immunoreactive for SOM are present in the mucosa of the seminal vesicle from 23 weeks of gestation.

Autonomic Nervous System↗

PubMed1995

Development of peptide-containing nerves in the human fetal prostate gland.

Immunohistochemical methods were used to study the developing peptidergic innervation of the human fetal prostate gland in a series of specimens ranging in gestational age from 13 to 30 wk. The overall innervation of each specimen was visualised using protein gene product 9.5 (PGP), a general nerve marker. The onset and development of specific neuropeptide-containing subpopulations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), bombesin (BOM), somatostatin (SOM), leu-enkephalin (l-ENK) and met-enkephalin (m-ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH). At 13 wk numerous branching PGP-immunoreactive (-IR) nerves were observed in the capsule of the developing prostate gland and surrounding the preprostatic urethra but the remainder of the gland was devoid of nerves. The majority of nerves in the capsule contained D beta H and TH and were presumed to be noradrenergic in type while other nerves (in decreasing numbers) contained NPY, l-ENK, SP and CGRP. Nerves associated with the preprostatic urethra did not contain any of the neuropeptides under investigation. At 17 wk the density of nerves in the capsule had increased and occasional m-ENK-, VIP- and BOM-IR nerve fibres were also observed. In addition PGP, D beta H-, TH-, NPY- and l-ENK-IR nerves occurred in association with smooth muscle bundles which at 17 wk were present in the outer part of the gland. Occasional PGP-IR nerves were also present at the base of the epithelium forming some of the prostatic glands. At 23 wk some of the subepithelial nerves showed immunoreactivity for NPY, VIP or l-ENK. At 26 wk smooth muscle bundles occurred throughout the gland and were richly innervated by PGP, D beta H and TH-IR nerves while a less dense plexus was formed by NPY- and l-ENK-IR nerves together with a few m-ENK-IR nerves. Occasional smooth muscle-associated varicose nerve fibres showed immunoreactivity for SP, CGRP, VIP or BOM although the majority of these types of nerve formed perivascular plexuses. Also at 26 wk numerous varicose nerve fibres were observed in association with the prostatic acini, the majority of such nerves containing NPY with a few showing immunoreactivity to VIP, l-ENK, SP or CGRP.(ABSTRACT TRUNCATED AT 400 WORDS)

Bombesin↗

PubMed1995

Helicobacter pylori eradication: unravelling the facts.

BACKGROUND: Recommendations for the choice, doses or duration of eradication therapy are still lacking. The purpose of this review was therefore to assess what conclusions could be drawn about eradication therapy, subsequent reinfection with Helicobacter pylori and ulcer recurrence. METHODS: Data were extracted from published papers and abstracts and entered into a dedicated database for appropriate subset analyses. RESULTS: Despite problems of patient compliance and metronidazole resistance, triple therapy with either a bismuth salt or an antisecretory agent plus two antibiotics appears to provide the most effective eradication of H. pylori (< 80%). Dual therapies such as omeprazole plus amoxycillin are less effective (mean 59%, range 0-92%). Reinfection rates over one year vary between countries from 3% in Australia and the USA to 35% in Ireland. Reports of ulcer recurrence during the first year after successful eradication range from 0 to 27%. CONCLUSIONS: There are insufficient data for particular doses and durations of eradication therapy from well designed controlled studies.

Anti-Bacterial Agents↗

PubMed1994

A shape- and chemistry-based docking method and its use in the design of HIV-1 protease inhibitors.

The program DOCK [1,2] has been used successfully to identify molecules which will bind to a specified receptor [3]. The original method ranks molecules based on their shape complementarity to the receptor site and relies on the chemist to bring the appropriate electrostatic or hydrogen bond properties into the molecular skeletons obtained in the search. This is useful when screening a small database of compounds, where it is not likely that molecules with both the correct shape and electrostatic properties will be found. As large databases are more likely to have redundant molecular shapes with a variety of functionality (e.g., members of a congeneric series), it would be useful to have a method which identifies molecules with both the correct shape and functionality. To this end we have modified the DOCK 1.0 method to target user-specified atom types to selected positions in the receptor site. The target sites can be chosen based on structural evidence, calculation or inspection. Targeted-DOCK improves the ability of the DOCK method to find the crystallographically determined binding mode of a ligand. Additionally, targeted-DOCK searches a database of small molecules at 100-1000 times the rate of DOCK 1.0, allowing more molecules to be screened and more sophisticated scoring schemes to be employed. Targeted-DOCK has been used successfully in the design of a novel non-peptide inhibitor of HIV-1 protease.

Binding Sites↗

PubMed1994

The effect of renal function on the pharmacokinetics of ranitidine.

This open study evaluated the influence of renal function on the pharmacokinetics of ranitidine (50 mg i.v. infusion given over 6 min). Five groups, each of 8 subjects, 1 with normal renal function and 4 with different degrees of renal impairment were studied. Renal function was assessed in each patient by 51Cr-EDTA (glomerular filtration rate, GFR), creatinine clearance (GFR) and N-methylnicotinamide clearance (reflecting glomerular and tubular function). Sixteen blood samples (5 ml) taken up to 48 h post dose from each subject were analysed for plasma ranitidine concentrations by reversed phase HPLC. Patient groups with renal impairment had significantly increased AUC infinity and t1/2 with corresponding decreases in CLp and lambda z when compared with normal subjects. There was also a significant increase in tmax but not in Cmax. There was a high linear correlation between the degree of renal impairment and ranitidine clearance. In patients with GFR < or = 20 ml min-1, the AUC infinity mean ratio (compared with normal subjects) was up to 4.6 while for patients with GFR 20-50 ml min-1, the average AUC infinity ratio was 2.6. It is recommended that the dose of ranitidine is halved in patients with GFR < or = 20 ml min-1.

Adult↗

PubMed1994

Short report: long-term management of peptic ulcer disease with ranitidine in Germany.

One hundred and twenty-five patients with duodenal ulcer disease were given continuous ranitidine therapy after initial acute healing. Cumulative remission rates indicated that 95% of patients were ulcer-free after 1 year, 89% at 2 years, 81% at 3 years, 70% at 4 years and 60% at 5 and 6 years. Nine patients had a second recurrence after healing of the first. No patient developed an ulcer complication. These results support the view that long-term continuous ranitidine therapy prevents ulcer recurrence and complications.

Duodenal Ulcer↗

PubMed1994

An immunohistochemical study of the innervation of the ureterovesical junction in infancy and childhood.

OBJECTIVE: To use histological and immunohistochemical methods to study the structure and innervation of the human ureterovesical junction (UVJ). MATERIALS AND METHODS: A series of 24 post-natal specimens taken from patients ranging in age from 1 month to 6 years were examined. Routine histological slides were stained with Masson's trichrome. In addition, an indirect immunohistochemical method was used to study the occurrence and distribution of nerves immunoreactive for the neuropeptides vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), substance P (SP) and calcitonin gene-related peptide (CGRP). Immunoreactivity to tyrosine hydroxylase (TH), dopamine-B-hydroxylase (DBH) and to protein gene product (PGP) 9.5, a general nerve marker, were also studied. RESULTS: The UVJ comprised a ureteric muscle component (the intramural ureter) and a detrusor component (the immediately adjacent region of the urinary bladder). In the majority of specimens a third or intermediate layer was also present. This additional component consisted of tightly-packed smooth muscle cells which formed an incomplete layer that partially surrounded the juxta-vesical and intramural parts of the ureter. Numerous PGP-, VIP-, NPY, DBH- and TH- like immunoreactive (-LIR) nerves were associated with the smooth muscle bundles which comprised the intramural ureter. Such nerves ran in the connective tissue separating ureteric smooth muscle bundles and rarely coursed amongst individual smooth muscle cell comprising each bundle. SP- and CGRP- containing nerves were rarely observed in association with the intramural ureter and none were detected in the ureteric submucosa. The intermediate muscle layer was richly innervated by PGP-, TH-, DBH- and NPY- containing nerves which ran amongst the smooth muscle cells comprising this layer. VIP-, SP- and CGRP-LIR nerves were not observed within the intermediate layer. The detrusor component of the UVJ was innervated by PGP-, NPY- and VIP-LIR nerves which frequently extended between the smooth muscle cells forming the detrusor muscle bundles. TH-, DBH-, SP- and CGRP-LIR nerve fibres were rarely encountered. CONCLUSION: These findings indicate that noradrenergic nerves play a major role in the control of the ureteric component of the UVJ. In addition, the present results form baseline morphological data with which to compare the results of future studies on the structure of the UVJ in cases of vesicoureteric reflux.

Child↗

PubMed1994

The intramural innervation of the human vas deferens and seminal vesicle in infants and children.

Immunohistochemical methods were used to study the autonomic innervation of the vas deferens and seminal vesicle in a series of human postnatal specimens ranging in age from 1 month to 3 years. The occurrence and distribution of nerves immunoreactive for the neuropeptides vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) substance P (SP) and calcitonin gene-related peptide (CGRP) were investigated. In addition immunoreactivity to tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and to protein gene product (PGP 9.5), a general nerve marker were also studied. A neurohistochemical method was used to localise acetylcholinesterase. The results obtained from either organ were similar. Regardless of age, a rich plexus of nerve fibres immunoreactive for PGP 9.5 was present both within the muscle coat and also beneath the epithelium of the vas deferens and seminal vesicle. Some acetylcholinesterase containing nerves occurred in the muscle coat but the majority were found under the epithelium in the connective tissue of the mucosa. TH and DBH-containing nerves (presumably noradrenergic in type) formed dense intramuscular plexuses but none occurred subepithelially. In contrast NPY-containing nerves formed a less dense intramuscular plexus and were also observed beneath the epithelium. Thus while NPY may occur in some of the intramuscular noradrenergic nerve fibres it is clearly not confined to this type of nerve in either the vas deferens or the seminal vesicle. SP- and CGRP-containing nerves were extremely infrequent and, when observed, were confined to the muscle coat.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic Nervous System↗

PubMed1993

Early evening dosing of ranitidine. Comparison with nighttime dosing of ranitidine or cimetidine in duodenal ulceration.

A double-blind multinational comparison of ranitidine 300 mg post evening meal (pem), ranitidine 300 mg nocte and cimetidine 800 mg nocte has been carried out in 1677 patients with endoscopically verified duodenal ulcer disease. Fifty-three percent of ulers healed by two weeks during treatment with ranitidine 300 mg pem and 88% by four weeks, while the results for ranitidine 300 mg nocte were 50% and 86%, respectively, and 44% and 84% for cimetidine. The difference between ranitidine 300 mg pem and cimetidine was significant at two weeks (P = 0.002, Mantel-Haenszel chi-squared test). The relative efficacy of the treatments was not dependent upon gender, smoking habit, alcohol intake, or ulcer frequency. However, the overall differences in healing between patients with small and large ulcers and patients with single and multiple ulcers were significantly different at weeks 2 and 4 (P < 0.001). Significantly more patients treated with ranitidine (60%) had complete relief of epigastric pain than those treated with cimetidine (54%) (P < 0.05). A meta-analysis of the four double-blind comparisons of ranitidine 300 mg pem (N = 841) and 300 mg nocte (N = 849), including the present study, failed to show the benefits of pem dosing, predicted from pharmacological studies.

Adult↗

PubMed1993

Association of age with the efficacy and safety of ranitidine and cimetidine in acute duodenal ulcer disease.

This multinational double-blind trial compared the efficacy and safety of ranitidine 300 mg nocte, 300 mg post-evening meal (pem) and cimetidine 800 mg nocte in patients with endoscopically verified duodenal ulcer disease aged < 60 years (n = 1318) and > or = 60 years (n = 354). The relative efficacy of the treatments was not dependent upon age after either 2 or 4 weeks of therapy. However, ulcer healing after 2 weeks of therapy was significantly higher in patients receiving ranitidine 300 mg pem than in those receiving cimetidine (p = 0.003) in the < 60-year group, but the difference was not significant in the > or = 60-year group. Fewer patients aged > or = 60 years on cimetidine (62%) became pain free compared with those on ranitidine (72% in both groups). Relief of epigastric pain and heartburn was related to pre-trial severity in both age groups. The incidence and type of adverse events were similar in the two age groups. It is concluded that ranitidine and cimetidine are as effective at healing duodenal ulcer and relieving ulcer symptoms in elderly as in younger patients.

Adolescent↗

PubMed1993

Optimizing the assessment of disease activity during treatment with anti-rheumatoid drugs.

Clinical trials in RA usually involve the use of several laboratory assessments of disease activity. Their use is not universal and the relative value of many novel assessments has not been determined in relation to existing clinical and laboratory methods. This study attempts to investigate the value of established and novel assessments of disease activity during treatment with accepted DMARDs. Over a 48-week study period, changes in cytidine deaminase (CD), beta 2-microglobulin, alpha 1-acid glycoprotein (alpha 1-AGP), serum antibodies to Clostridium perfringens alpha-toxin, pre-albumin and caeruloplasmin were compared to a group of established clinical and laboratory assessments including plasma viscosity, CRP haemoglobin and platelet count during treatment with the established second-line drugs, D-penicillamine (n = 20), sulphasalazine (n = 17), gold (n = 12) and hydroxychloroquine (n = 18). Overall, the assessments showing the greatest degree of change were plasma viscosity, articular index, summated change score, platelet count, CD, white cell count, alpha 1-AGP, CRP and pain score. The assessments showing the greatest degree of change were not homologous between the treatment groups and no single assessment was outstanding for a particular drug treatment.

Anti-Inflammatory Agents↗

PubMed1993

A placebo-controlled investigation of duodenal ulcer recurrence after withdrawal of long-term treatment with ranitidine.

Ninety-two patients with duodenal ulcer disease, who had received long-term continuous treatment with ranitidine for an average of 7.5 years, participated in a double-blind, placebo-controlled study to determine whether stopping ranitidine resulted in ulcer recurrence. Patients were randomized to continue with ranitidine (n = 46) or to receive placebo (n = 46) and were followed up for six months. Treatment failure was defined as the first symptomatic recurrence of ulcer. The occurrence of epigastric pain during the follow-up period was significantly less frequent in the ranitidine group (13%) than in the placebo group (43%) (P = 0.001). At six months, 9% of the ranitidine group had developed ulcer recurrence, compared with 48% in the placebo group (P < 0.001, logrank test). Multivariate analysis using the Cox proportional hazards model showed that younger age (P = 0.041) and a long history of ulcer disease (P = 0.025) were risk factors for ulcer recurrence but gender, smoking and duration or dose of previous ranitidine treatment were not predictive of relapse during treatment with placebo. In conclusion, withdrawal of ranitidine after more than five years of continuous treatment results in almost half of the patients developing symptomatic ulcer recurrence within six months. Thus, long-term continuous therapy does not alter the natural history of duodenal ulcer disease. Younger patients and those with a long history of ulcer disease appear to be at increased risk of developing ulcer recurrence if long-term treatment is withdrawn.

Age Factors↗

PubMed1993

Ultrastructural observations on cystitis cystica in human bladder urothelium.

Cystitis cystica, a common urothelial pathology whose aetiology, morphology and clinical significance are poorly understood, affects the human urinary bladder and trigone in both sexes. We have studied the fine structure of urothelial cysts in 11 patients diagnosed cystoscopically as suffering from cystitis cystica. Several abnormal features were observed in the adjacent urothelium, including large intracellular vacuoles (4 patients), Brunn's nest (5), lymphocyte infiltration (10) and generally disorganised urothelial architecture (10). Squamous metaplasia was observed in one case. The wall of each cyst consisted of a 2-3 layered epithelium with either tall columnar or flattened cells lining the fluid-filled lumen. Both types of lining cell possessed short microvilli, while the columnar type also contained numerous membrane-bound, electron dense secretory granules in the apical cytoplasm. Rough endoplasmic reticulum, mitochondria and Golgi membranes were plentiful in the surface cells. Junctional complexes joined adjacent lining cells. The deeper cells contained relatively fewer organelles, while a basal lamina separated the cyst wall from the underlying connective tissue.

Aged↗

PubMed1992

Proteolysis of an active site peptide of lactate dehydrogenase by human immunodeficiency virus type 1 protease.

The muscle and heart lactate dehydrogenase (LDHs) of rabbit and pig are specifically cleaved at a single position by HIV-1 protease, resulting in the conversion of 36-kDa subunits of the oligomeric enzymes into 21- and 15-kDa protein bands as analyzed by SDS-PAGE. While the proteolysis was observed at neutral pH, it became more pronounced at pH 6.0 and 5.0. The time courses of the cleavage of the 36-kDa subunits were commensurate with the time-dependent loss of both quaternary structure and enzymatic activity. These results demonstrated that deoligomerization of rabbit muscle LDH at acidic pH rendered its subunits more susceptible to proteolysis, suggesting that a partially denatured form of the enzyme was the actual substrate. Proteolytic cleavage of the rabbit muscle enzyme occurred at a decapeptide sequence, His-Gly-Trp-Ile-Leu*Gly-Glu-His-Gly-Asp (scissile bond denoted throughout by an asterisk), which constitutes a "strand-loop" element in the muscle and heart LDH structures and contains the active site histidyl residue His-193. The kinetic parameters Km, Vmax/KmEt, and Vmax/Et for rabbit muscle LDH and the synthetic decapeptide Ac-His-Gly-Trp-Ile-Leu*Gly-Glu-His-Gly-Asp-NH2 were nearly identical, suggesting that the decapeptide within the protein substrate is conformationally mobile, as would be expected for the peptide substrate in solution. Insertion of part of this decapeptide sequence into bacterial galactokinase likewise rendered this protein susceptible to proteolysis by HIV-1 protease, and site-directed mutagenesis of this peptide in galactokinase revealed that the Glu residue at the P2' was important to binding to HIV-1 protease. Crystallographic analysis of HIV-1 protease complexed with a tight-binding peptide analogue inhibitor derived from this decapeptide sequence revealed that the "strand-loop" structure of the protein substrate must adopt a beta-sheet structure upon binding to the protease. The Glu residue in the P2' position of the inhibitor likely forms hydrogen-bonding interactions with both the alpha-amide and gamma-carboxylic groups of Asp-30 in the substrate binding site.

Amino Acid Sequence↗