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Biomedical subjects

S Walker

Publications and source records attributed to S Walker.

At least 271 records · Page 15Linked to original sources
PubMed1992

Members of the USF family of helix-loop-helix proteins bind DNA as homo- as well as heterodimers.

We have isolated human cDNA clones for USF2, a new member of the upstream stimulatory factor (USF) family of transcription factors. Analysis of these clones revealed the existence of highly conserved elements in the C terminal region of all USF proteins. These include the basic region, helix-loop-helix (HLH) motif, and, in the case of the human proteins, the C-terminal leucine repeat (LR). In addition, a highly conserved USF-specific domain is located immediately upstream of the basic region. Using in vitro translated proteins, we found that all members of the USF family bound DNA as dimers. The N-terminal portion of USF, including the USF-specific domain, was entirely dispensable for dimer formation and DNA-binding. However, deletion mutants of USF2 lacking the LR were deficient in DNA-binding activity. Interestingly, each of the USF proteins could form functional heterodimers with the other family members, including the sea urchin USF, which does not have a LR motif. This indicates that the conserved LR in human USF is not required for dimer formation, and influences only indirectly DNA-binding.

Amino Acid Sequence↗
PubMed1992

Cefaclor as a prophylactic agent for recurrent urinary infections: a comparative trial with macrocrystalline nitrofurantoin.

Eighty women with recurrent urinary infections (a median of seven episodes per year) were randomized to twelve months prophylaxis with cefaclor 250 mg or macrocrystalline nitrofurantoin 50 mg, at night. Seventy-three patients (37 given cefaclor and 36 given macrocrystalline nitrofurantoin) were assessable for efficacy. The incidence of radiological abnormalities in the two treatment groups was 23% and 30% respectively. Ninety-five percent of the patients taking cefaclor were symptomatically improved during the twelve months of prophylaxis and 86% remained abacteriuric; corresponding figures in the group taking macrocrystalline nitrofurantoin were 86% and 85% respectively. There were 88 breakthrough infections in patients taking cefaclor (6 resistant strains), and 9 in those patients taking macrocrystalline nitrofurantoin (6 by resistant strains). The mean interval between symptomatic episodes on prophylactic therapy increased by 5.6-fold in patients taking cefaclor, and 4.3-fold in those taking macrocrystalline nitrofurantoin. Resistant coliforms were found in only 3 out of 37 patients studied after twelve months prophylaxis; these organisms did not proceed to cause infections. All 80 patients were assessable for adverse events: 5 out of 39 taking cefaclor (12.8%) reported an event "probably" associated with the antibiotic, and 3 (7.7%) stopped taking the drug for various reasons; corresponding figures for macrocrystalline nitrofurantoin were 17.1% and 9.8% respectively. Patients with a radiological abnormality responded well to long-term low-dose prophylaxis with either agent. Cefaclor seems to offer an alternative to macrocrystalline nitrofurantoin for the prophylaxis of recurrent urinary infections in women.

Adult↗
PubMed1992

The acute phase response in autologous bone marrow transplantation.

Due to the stress imposed by the process of bone marrow transplantation (BMT), we hypothesized that individuals receiving such a transplant underwent an acute phase response (APR). Circulating levels of C-reactive protein (CRP), haptoglobin (HAP), alpha-1 acid glycoprotein (AAG), ceruloplasmin (CER), zinc (Zn), copper (Cu), interleukin-6 (IL-6), albumin (ALB), and thyroxine-binding prealbumin (TBPA), were measured at baseline (Day -7), Day -4, Day 0 (Transplant Day), Day +2, +7, and weekly until day 28 in 14 adults receiving an autologous bone marrow transplant as Phase 1 treatment for various hematologic or solid tumor malignancies. Ten of 14 recipients survived, 9 of which had a significant increase in CRP (p = 0.012), HAP (p = 0.011), AAG (p = 0.002), and decrease in ALB (p = 0.002) and TBPA (p = 0.004) on Day +7, but not Day 0, after bone marrow reinfusion. These findings document the presence of an APR and suggest that the bone marrow transplant process (post reinfusion) initiates a stress response in the recipient.

Acute-Phase Reaction↗
PubMed1992

A multicenter evaluation of lipid profiling with a compact analyzer (Miles Clinistat).

We evaluated the Clinistat Analyzer (Miles Inc., Diagnostics Division, Elkhart, IN) for measuring cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol at three medical centers. The system, based on multilayer film technology, uses precalibrated, dry film reagent disks. Ten microliters of serum is applied to the dry film reagent disk in the test procedure. For HDL-cholesterol measurement, serum is pretreated by precipitation with phosphotungstic acid and magnesium chloride. Total precision (CVs) of each of the three assays was less than or equal to 5%. The assay ranges were linear and satisfactory for clinical use. Patients' results compared well with established methods. No significant interferences were found with hemolysis, icterus, and lipemia.

Chemistry, Clinical↗
PubMed1991

Temperature-dependence of LDL binding and activation of human platelets.

The effect of low density lipoprotein (LDL) on intracellular free calcium ion concentration ([Ca2+]i), taken as an index of the degree of platelet activation, was investigated in normal volunteers. At 37 degrees C LDL, in a dose of 20 micrograms of protein/ml, increased [Ca2+]i in all subjects tested (basal 57 +/- 11 to 113 +/- 19 nM). In contrast, when measurements were performed at 20 degrees C, no effect on [Ca2+]i was seen following LDL. Thrombin (0.2 U/ml) increased [Ca2+]i to 455 +/- 98 nM. When platelets had been exposed to LDL before thrombin stimulation, this increase was less pronounced (to 301 +/- 43 nM). Our finding of a temperature dependence of LDL induced increase in platelet [Ca2+]i supports the concept of a platelet-LDL receptor mediated mechanism. Furthermore, the lower thrombin response following LDL exposure suggests a LDL-thrombin interaction, possibly at the thrombin receptor level and/or calcium recruitment from the same stores.

Adult↗
PubMed1991

[The localization of colorectal polyps and carcinomas in relation to their size and the histological findings].

Location, size and histological appearance of colorectal neoplasms were examined retrospectively. A total of 1,357 polyps (including small ones, diameter below 0.5 cm) were found in 1,022 of 3,057 coloscopies. The coloscopies were indicated by findings on preceding radiological or endoscopic examinations (48%), occult blood in stool (18%), during follow-up after polypectomy (21%), and after colorectal carcinoma (13%). A single polyp was found in 718 cases (70%), two to four in 221 (26%), more than five in 33 (4%), 1,106 polyps (61%) were found on high coloscopy; 380 of these (38%) were located proximal to the left flexure. Among the 1,230 polyps examined histologically 907 (74%) were adenomas (494 tubular [54%], 379 tubulovillous [42%], 34 villous [4%]). 251 (28%) of the adenomatous polyps and 49 (32%) of the 151 carcinomas were located proximal to the left flexure. The incidence of moderately severe to severe dysplasias increased with increasing diameter of the polyps: 55% of those smaller than 0.5 cm were adenomas. 70% of polyps with a diameter over 1.0 cm were tubulovillous or villous adenomas. The findings confirm that there is a high incidence of polyps proximal to the left flexure. A complete coloscopy should therefore be done as a matter of course.

Age Factors↗
PubMed1991

[Granular-cell tumor of the stomach and esophagus].

A 45-year-old man had for the past four years complained of postprandial feeling of fullness and of left-thoracic pressure sensation. Endoscopy revealed a spherical subcardial tumour, about 3.5 cm diameter, a yellow raised flat 7 x 4 mm tumour in the oesophagus about 44 cm from the upper teeth, and 29 cm from the upper teeth a 4 mm bulge. Forceps biopsy of the subcardial tumour and fine-needle biopsy of the rather larger oesophageal tumour indicated a granular cell tumour. Because of the risk of malignancy the gastric tumour was resected (local excision and fundal plication). The patient has remained without symptoms for 28 months. Follow-up endoscopies have demonstrated that the oesophageal tumours had not grown any further.

Biopsy↗
PubMed1991

Genomically imposed and somatically modified human thymocyte V beta gene repertoires.

The effect of thymic selection on the expressed human T-cell antigen receptor beta-chain variable region (V beta) gene repertoire was examined by using a multiprobe RNase protection assay. The relative abundance of transcripts for 22 V beta genes (encompassing 17 of the 20 human V beta gene subfamilies) within a thymus, and among 17 thymuses, was variable. On the basis of the presence of corresponding mRNAs, no genomic deletions were detected, but several coding region polymorphisms were identified. Analysis of mature T-cell subsets revealed the absence of complete "superantigen"-mediated V beta deletions, suggesting that this phenomenon, in contrast to mouse, is uncommon or absent in humans. However, several V beta genes were over- or underexpressed in one or both mature single-positive (CD4+8- or CD8+4-) thymocyte subsets compared to syngeneic total, mostly immature thymocytes. Whether these changes are induced by relatively weak superantigens or conventional antigens and whether the downshifts are caused by negative selection or lack of positive selection remains to be determined.

Child↗
PubMed1991

The effect of age on the pharmacokinetics of pentisomide.

The effects of age on the pharmacokinetics of pentisomide (CM7857), an orally effective antiarrhythmic agent, were studied in two groups of volunteers. Sixteen young volunteers (mean age 26.4 years) and 10 elderly volunteers (mean age 67.8 years) received a single 200 mg oral dose of pentisomide. Mean AUC was larger and terminal elimination half-life longer in the elderly subjects, due to a decrease in total plasma clearance of pentisomide in the elderly. This decrease was due to a reduction in renal clearance of the drug which was paralleled by a significantly lower creatinine clearance in the elderly subjects. Dosage reduction, or a reduced frequency of dosing of pentisomide would be necessary in the elderly or those with impaired renal function.

Administration, Oral↗
PubMed1991

The modified AFP score: an attempt to make the results of anti-reflux surgery comparable.

Comparison of different strategies in anti-reflux therapy is complicated by wide variations in patient selection and in the criteria employed to assess outcome. A modification of the classification system originally developed by Bancewicz et al. was used to grade a series of 57 patients before and after fundoplication (primary reflux group). An additional group of 39 patients with an unsatisfactory result after previous Nissen fundoplication (failed Nissen group) were assessed before and after reoperation. The classification system used comprises three elements: the A element depicts gastro-oesophageal anatomy based on the findings at endoscopy: the F element codes the amount of acid reflux by means of 24-h intra-oesophageal pH monitoring; and the P element describes mucosal abnormalities. The overall severity was quantified by means of a score on a scale from 0 to 10. The mean preoperative score in the primary reflux group was 5.45 and in the failed Nissen group 7.3. After fundoplication, this was reduced to 1.07 and 1.30, respectively. In general, there was good correlation between the results of the three elements under consideration, pointing to a potential pathophysiological inter-relationship. Marked individual variation did occasionally occur. The AFP system enabled a detailed description of the preoperative and postoperative condition of the patient, and proved easy to use in clinical practice. Its employment is recommended as an objective means of comparing the value of different treatment strategies.

Adolescent↗
PubMed1991

Neutral metalloendopeptidase associated with the smooth muscle cells of pregnant rat uterus.

The pregnant rat uterus contains a membrane-bound metalloendopeptidase that is biochemically and immunologically similar to kidney enkephalinase (E.C.3.4.24.11). The uterus enzyme readily cleaved specific neutral endopeptidase substrates and oxytocin as well as the synthetic elastase substrate, Suc(Ala)3-pNA, yet did not digest native elastin. Using specific inhibitors, the uterus endopeptidase was identified as a metallopeptidase and not a serine protease, having an absolute requirement for zinc and perhaps calcium for maximal activity. The uterus endopeptidase cross-reacted with polyclonal antiserum to kidney microvillar endopeptidase and a monoclonal antibody to common acute lymphocytic leukemia antigen. Immunohistochemical localization of the enzyme in a 17 day pregnant uterus indicated that the enzyme was localized on the smooth muscle bundles of the myometrium and the endometrial epithelium. Total enzyme activity was 25 times higher in the late-term pregnant uterus (17th day of pregnancy) than in the nonpregnant uterus. Enzyme levels dropped rapidly prior to parturition and within 4 days after delivery the enzyme activity had returned to control levels. Inhibition of NEP in uterine strips with phosphoramidon resulted in a marked potentiation of oxytocin-induced contractions. Our results suggest that the uterine endopeptidase may have an important role in regulating uterine smooth muscle cell contraction during the later stages of pregnancy through its action on oxytocin and perhaps other biologically active peptides.

Animals↗
PubMed1991

Oxygen content of the fixative is important in the interpretation of the ultrastructure of ischaemic myocardium.

Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37 degrees C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO2 620 mm Hg) or with 100% nitrogen (PO2 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO2 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible.

Animals↗
PubMed1991

High incidence of antibodies to hepatitis C virus in alcoholic cirrhosis: fact or fiction?

An enzyme immunoassay (Ortho-HCV ELISA) for antibodies against the hepatitis C virus was used to test serum samples from 39 patients with alcoholic cirrhosis and 34 patients with alcoholic hepatitis or fatty liver. The frequency of a positive result in the cirrhotics was significantly higher than in the alcoholics without cirrhosis (38.5% vs 8.8%, P less than 0.01). However, the positive results in the cirrhotics were associated with high gammaglobulin concentrations, and optical density values in the assay correlated closely with serum globulin (r = 0.73, P less than 0.01). The findings suggest that serum from patients with alcoholic cirrhosis may contain a component that give false-positive results in the assay.

Biopsy↗
PubMed1991

Tripotassium dicitrato bismuthate: absorption and urinary excretion of bismuth in patients with normal and impaired renal function.

We have investigated the absorption and urinary excretion of tripotassium dicitrato bismuthate during a treatment course of 4 weeks in 7 patients with normal renal function (creatinine clearance 115 +/- 29 ml/min; mean +/- S.D.), in 7 patients with impaired renal function (creatinine clearance = 34 +/- 19 ml/min) and in 4 dialysed patients. Following the first dose of tripotassium dicitrato bismuthate (216 mg bismuth b.d.), and after 2 and 4 weeks of treatment (dialysed patients received only 108 mg/b.d.), plasma and urine concentrations of bismuth were monitored for 2 and 24 h, respectively. After stopping therapy plasma and urine concentrations of bismuth were followed for 4 and 6 weeks, respectively. In all three groups of patients small amounts of bismuth (mean values 0.26 to 0.28% of dose) were rapidly (transient mean peak concentrations between 40 and 134 micrograms/L) reached within about 30 to 40 min, absorbed and plasma levels demonstrated a wide intra- and inter-individual variability. Absorption profiles were not altered during the treatment course; however, the trough plasma concentration of bismuth demonstrated an about 3- to 5-fold accumulation (correlated to creatinine clearance) from about 5 micrograms/L to 15 micrograms/L (normal renal function) or to 20-25 micrograms/L (impaired renal function). Pre-study bismuth levels could be detected within 2 to 4 weeks after stopping therapy in all subjects whereas urinary concentrations were still elevated 6 weeks after the course of treatment. Our results indicate that tripotassium dicitrato bismuthate is absorbed in very low amounts during standard therapy. However, dependent on renal function, accumulation to non-toxic levels does occur during a course of treatment. It appears prudent to halve tripotassium dicitrato bismuthate dosage in patients with severe renal insufficiency (creatinine clearance less than or equal to 20 ml/min) to avoid any possible toxic risks. In such patients monitoring of the plasma bismuth concentration might be helpful, especially if longer or repeated treatment is anticipated.

Absorption↗