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Biomedical subjects

B J Campbell

Publications and source records attributed to B J Campbell.

At least 19 recordsLinked to original sources
PubMed1995

Molecular characterization and physiological regulation of a TATA-less gene encoding chicken gastrin.

Avian gastrin is a gastric acid secretagogue, but is structurally more closely related to mammalian cholecystokinin, which is functionally distinct from gastrin. This apparently anomalous structure/activity relationship raises important issues for understanding the evolution of regulatory peptides and the mechanisms that control their expression. To clarify the possible mechanisms, we have determined the sequence of a 6.5-kb BamHI genomic DNA fragment that includes the entire avian gastrin transcriptional unit. The complete cDNA sequence, determined by anchored PCR, encoded a precursor of 105 amino acids. Conserved primary amino acid structures were limited to a decapeptide determining biological activity, and essential sites for post-translational processing. Significantly, however, the genomic regulatory regions, and introns, were unlike those of any previously reported gastrin/cholecystokinin gene. The avian gastrin gene contained no recognizable TATA-box motif, a feature unique to this gene family, but had a G+C-rich region immediately upstream of the transcription initiation site, and a Z-DNA purine-pyrimidine repeat sequence. Moreover, physiological regulation of the avian gastrin gene differed markedly from that observed in mammals, in that the important local paracrine downregulation by antral somatostatin was absent; instead, evidence for a hormonal regulation was demonstrated. The data indicate that genomic regulatory elements within regulatory peptide families such as the gastrin/cholecystokinin family, and mechanisms of physiological control, are not conserved during evolution, even though biologically important amino acid sequence information is retained.

Amino Acid Sequence↗
PubMed1995

Faecal mucinase activity assessed in inflammatory bowel disease using 14C threonine labelled mucin substrate.

Previous studies have shown the presence in faeces of sulphatases, sialidases, glycosidases, and proteases relevant to mucus degradation, but the relative role of these enzymes in the degradation of colonic mucus has been unclear. A total mucinase assay using 14C threonine biologically labelled human colonic mucin as substrate was therefore developed in this study. Faecal mucinase activity of a pooled normal faecal filtrate was capable of removing 80% of the 14C threonine label from mucin within eight hours incubation, but 20% remained intact despite prolonged incubation. The pH profile of mucinase activity is broad (pH 4.5-9.5) suggesting contribution from multiple enzymes. Mucinase activity was reduced by preincubation with 100 micrograms/ml chymostatin (82.8%), 0.5 mg/ml EDTA (91.6%), and 4 g/l bismuth subsalicylate (72.0%). All 55 faecal samples studied contained detectable mucinase activity, measured as dpm release/micrograms protein/hour, which was greater in samples from patients with ulcerative colitis (n = 17, median 52.7, interquartile range 32.9-66.9), than controls (n = 26, 34.4, 26.8-40.4, p < 0.02) or patients with Crohn's disease (n = 12, 35.5, 17.5-55.7, p < 0.05). There was, however, no significant difference in faecal mucinase activity between inactive and active ulcerative colitis. These results suggest that faecal mucinase activity is one factor contributing to the thin mucus layer in ulcerative colitis and represents a potential target for drug treatment.

Colitis, Ulcerative↗
PubMed1995

Direct demonstration of increased expression of Thomsen-Friedenreich (TF) antigen in colonic adenocarcinoma and ulcerative colitis mucin and its concealment in normal mucin.

Increased binding of the lectin peanut agglutinin is a common feature in epithelial malignancy and hyperplasia. This may have considerable functional importance in the intestine by allowing interaction between the epithelium and mitogenic lectins of dietary or microbial origin. Peanut agglutinin binds the disaccharide Thomsen-Friedenreich (TF, T or core 1) blood group antigen, Gal beta (1-3) GalNAc alpha-, but is not totally specific for this site. Consequently, there has been controversy about the presence of this structure in colon cancer; studies with anti-TF monoclonal antibodies have failed to detect it. We have examined the presence of TF antigen in colonic mucus glycoprotein (mucin) using endo-alpha-N-acetylgalactosaminidase (O-Glycanase), which specifically catalyzes the hydrolysis of TF antigen from glycoconjugates. Samples of adenocarcinoma, inflammatory bowel disease (ulcerative colitis), and normal mucin were treated with O-glycanase, the liberated disaccharide was separated from the glycoprotein and analyzed using dual CarboPac PA-100 column high performance anion-exchange chromatography coupled with pulsed amperometric detection. O-Glycanase treatment released increased amounts of TF antigen from both colonic adenocarcinoma (8.0 +/- 3.9 ng/micrograms protein, n = 11; P < 0.0001 ANOVA) and ulcerative colitis mucin (3.3 +/- 0.3 ng/micrograms protein, n = 5; P = 0.04) compared with mucin samples from histologically normal mucosa distant from carcinoma (1.5 +/- 1.1 ng/micrograms protein, n = 9). However, after mild acid treatment to remove sialic acids and fucose, releasable TF antigen was increased in all nine of these histologically normal mucin samples (5.5 +/- 2.6 ng/micrograms protein, P < 0.0002). We conclude that TF antigen is an oncofetal antigen which is expressed in colon cancer, but is concealed by further glycosylation (sialylation and/or fucosylation) in the normal colonic mucosa.

Adenocarcinoma↗
PubMed1991

Inhibition of food intake by omeprazole in the chicken.

Chickens treated with the H+/K+ ATPase inhibitor omeprazole, to inhibit gastric acid secretion, failed to gain weight and showed decreased food intake compared with controls. The gastrin antagonist PD134308 reversed the action of omeprazole on food intake. Since exogenous gastrin decreased food intake, and since omeprazole increased plasma gastrin concentrations, the results suggest that elevated plasma gastrin in chicken exerts a satiety effect.

Animals↗
PubMed1991

Change in injuries associated with safety belt laws.

Statewide crash data bases from nine states were subjected to time series analyses to detect changes in injuries associated with onset of seat belt laws in the respective states. In each of 18 analyses involving drivers covered by the law observed casualties were below the number forecast on the basis of prior experience and assuming that no law had been enacted. In the case of others, not covered by the law, observed injuries were equally often above or below forecast. Relative to covered drivers not only were the numbers below forecast, but in 12 of the 18 instances there was a statistically significant indication of an abrupt decrease the month the law began.

Accidents, Traffic↗
PubMed1991

Effects of peer-mediated instruction on the acquisition and generalization of written capitalization skills.

This study investigated the effects of a peer teaching procedure, combined with student letter-writing activities, on the acquisition and generalization of capitalization skills. Three students, aged 9 years, obtained instruction from peer partners that included (a) an introduction and review of capitalization rules, (b) feedback on each participant's previous capitalization work, and (c) guided and independent practice on sentences that required capitalization. All three students demonstrated acquisition of the capitalization rules after participating in the teaching sessions with one or two peer partners. In addition, there were increases in capitalization accuracy in participants' letters to peers who did not serve as teaching partners, thus demonstrating a measure of across-peer (stimulus) generalization. Mixed results were obtained on a response generalization task (sentence writing). Finally, sentencing-writing activities also showed that two of the peer partners substantially improved their use of capitalization skills as a result of teaching the target students.

Child↗
PubMed1990

Isolation, sequence and biosynthetic significance of a novel fragment of gastrin-releasing peptide from chicken proventriculus.

The isolation of bombesin-related peptides in chicken proventriculus was monitored by radioimmunoassay using a C-terminal specific bombesin antibody. Two peptides were identified, one corresponded to the 27-residue, chicken gastrin-releasing peptide (GRP-27) previously identified; the other corresponded to its C-terminal hexapeptide. Chicken GRP-27 stimulated pancreatic and gastric acid secretion in anaesthetized turkeys, but the hexapeptide was inactive. No evidence could be found to suggest that the hexapeptide was an artifact of degradation generated during extraction or isolation. It is proposed that the hexapeptide is produced either by chymotryptic-like cleavage of GRP-27 or by trypsin-like cleavage followed by two cycles of dipeptidylaminopeptidase cleavage. This type of biosynthetic processing may be more common than formerly supposed.

Amino Acid Sequence↗
PubMed1990

Bioconversion of leukotriene D4 by lung dipeptidase.

Sheep lung dipeptidase was released from a lung membrane preparation by digestion with phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis. The total enzyme activity released into the supernatant was 4- to 5-fold greater than that measured in the intact membrane prior to solubilization. The release of the peptidase from the membrane by this treatment is typical of proteins anchored to the lipid bilayer by a covalent attachment of phosphatidylinositol via a C-terminal glycolipid extension. The solubilized lung peptidase was further purified by ammonium sulfate fractionation followed by affinity chromatography and high-pressure liquid chromatography. A linear relationship between log molecular weight and elution volume for proteins of known molecular weight was established using a Toya Soda TSK 3000 high-pressure liquid chromatography column, and the molecular weight of the lung dipeptidase was estimated at 105,000. The peptidase activity against glycyldehydrophenylalanine of the purified enzyme co-chromatographed in high-pressure liquid chromatography with the activity that converted leukotriene D4 to leukotriene E4. In kinetic studies using leukotriene D4 as substrate, the relationship between the rate of hydrolysis and enzyme concentration was shown to be linear over the range 20 ng to 98 ng enzyme. Values of Km and Vmax for the dipeptidase using leukotriene D4 as substrate were 43 +/- 6 microM and 11,200 +/- 400 nmol/min per mg, respectively. Inhibition of the conversion of leukotriene D4 to leukotriene E4 was observed with a series of inhibitory agents. Cilastatin, bestatin and chloracetyldehydrophenylalanine were all effective at the micromolar level with cilastatin proving to be the most effective inhibitor. Dithiothreitol was effective within the millimolar range.

Animals↗
PubMed1990

Evaluating the North Carolina safety belt wearing law.

The North Carolina Seat Belt Law required an evaluation of the effectiveness of the act with a report of the findings to the Legislature three years after the law went into effect. This paper addresses changes in statewide belt usage and in occupant injury associated with that law. Observational data collected bimonthly from a probability sample of 72 sites stratified by geographic region, rural/urban location, road type, and time of day show that belt use rose from a baseline rate of 25% to a warning ticket phase rate of 45%. Belt use then reached 78% upon enforcement and is now nearly 64%. Time series analysis showed that statistically significant reductions in percentages of moderate and serious injuries occurred at the beginning of both the warning ticket and the enforcement phases. Forecasts of injuries and deaths were also developed from the time series models and were compared with observed totals. Warning tickets brought about a modest 5.4% reduction in serious injuries; fatalities among occupants covered by the law showed no change. In contrast, the subsequent enforcement phase saw a reduction of 11.6% in fatalities and 14.6% in serious or worse injuries. This represents an estimated annual savings of 131 lives and over 2,300 serious injuries in North Carolina during the 18 months following onset of enforcement.

Accidents, Traffic↗
PubMed1988

Specificity and inhibition studies of human renal dipeptidase.

Purified human renal dipeptidase was shown to exhibit no detectable activity against substrates that are characteristic for other known mammalian peptidases. The enzymic activities that were assayed were: aminopeptidase A, aminopeptidase B, aminopeptidase M, aminopeptidase P, and tripeptidase. A quantitative assay for renal dipeptidase was developed which measures the rate of release of glycine from glycylpeptides by pre-column derivatization of the amino acid with phenylisothiocyanate followed by high-performance liquid chromatography. The ratio of Vmax/Km for a series of dipeptides was used as an index of the enzyme's preference for substrates. According to the data obtained, the enzyme prefers that a bulky, hydrophobic group of the dipeptide be located at the N-terminal position. This suggests that the substrate-binding site of the enzyme may provide a hydrophobic pocket to accommodate the hydrophobic moiety at the N-terminus of the dipeptide. The unsaturated dipeptide substrate, glycyldehydrophenylalanine, was employed in spectrophotometric assays to provide kinetic analyses of enzymic inhibition. The inhibitory effect of dithiothreitol was immediate, and the kinetic data indicated reversible, competitive inhibition. These results suggest that the inhibitor competes with substrate for a coordination site of zinc within the active site of the enzyme. The reaction of renal dipeptidase with the transition-state peptide analog, bestatin, was time dependent, and velocity measurements were made after the inhibitor had been incubated with the enzyme until constant rates were observed. These steady-state rate measurements, made following preincubation of enzyme with inhibitor, were employed to show that bestatin caused apparent non-competitive inhibition of the enzyme. The inhibitory effect of the beta-lactam inhibitor, cilastatin, upon the oligomeric dipeptidase was shown to be competitive. Graphical analysis of this inhibition indicated that the subunits of the enzyme react independently during enzymic catalysis and that the catalytic event is not influenced by cooperativity between sites on the subunits. The conversion of leukotriene D4 to leukotriene E4 in the presence of human renal dipeptidase was demonstrated by HPLC procedures. This bioconversion reaction was quantitated by derivatizing the glycine produced by cleavage of the cysteinylglycine bond and isolating this derivative as a function of time. The relationship between the purified enzyme concentration and enzyme activity against leukotriene D4 was shown to be linear over the enzyme concentration range of 1 ng through 69 ng in this assay.(ABSTRACT TRUNCATED AT 400 WORDS)

Cilastatin↗
PubMed1987

Safety belt injury reduction related to crash severity and front seated position.

This paper examines the effectiveness of seat belts in reducing injury among passenger car drivers and right front passengers. The analysis is based on more than 1.5 million occupants involved in North Carolina crashes during the years 1973-1981. Initial results show that seat belts reduce the risk of serious injury to the driver by 58% and fatal injury by 73%. For right front passengers, the comparable figures are 53% and 66%. When a measure of vehicle deformity reflecting the severity of the crash is introduced as a control variable, these effectiveness values decline somewhat. Depending on the specific approach taken, seat belts are shown to reduce the risk of serious injury to passenger car drivers by 51-52%, and the risk of fatal injury by 63-67%. For right front passengers, the effectiveness ranges are 43-44% for serious injury and 53-55% for fatal injury. While these adjusted estimates of belt effectiveness are lower than those based on the raw data, they nevertheless represent considerable benefit to car occupants using seat belts.

Accidents, Traffic↗
PubMed1986

The treatment of warts.

Warts are caused by the human papillomavirus and produce a variety of clinical manifestations, depending on the viral type and the site of the lesion. In this article, the pathophysiology of warts is reviewed briefly, and options for treatment, including liquid nitrogen, dinitrochlorobenzene, bleomycin, podophyllin, Duofilm, and surgical excision, are examined. Several case studies are also presented.

Adult↗
PubMed1985

Comparative toxinology of Loxosceles reclusa and Corynebacterium pseudotuberculosis.

In contrast to other kinds of phospholipases, phospholipases D that are toxic for humans and animals are not commonly encountered as constituents of venoms or as products of pathogenic microorganisms. Toxic phospholipases D are present, however, in the venom of the brown recluse spider (Loxosceles reclusa) and in supernatants or filtrates of cultures of Corynebacterium pseudotuberculosis. Although the two enzyme toxins are derived from phylogenetically disparate entities, they are similar in molecular weight, charge, substrate specificity, and in several biological activities. They are immunologically distinguishable.

Animals↗
PubMed1985

Aggregation of platelets by Fusobacterium necrophorum.

Broth cultures and washed cells of 13 of 24 bovine isolates of Fusobacterium necrophorum aggregated human platelets in platelet-rich plasma. The cell-free culture fluid was inactive. Bacteria stored at 4 degrees C in saline remained active for at least 3 months, but they did not release activity into the storage solution. Aggregation typically began within 1 min after the addition of 10(3) bacteria to 10(3) platelets was complete within 5.5 min. Assays for cytosolic lactic dehydrogenase revealed that platelet lysis did not occur. The release of [14C]serotonin from platelets preincubated with this amine accompanied aggregation, indicating that this was a typical aggregation-degranulation reaction. Platelet aggregation was inhibited by EDTA (88% at 2.0 mM), aspirin (75% inhibition at 1.0 mM), and quinacrine (80% inhibition at 0.25 mM). Thus the reaction was an ion-dependent, cyclooxygenase-sensitive event. Gel-filtered platelets were less sensitive to aggregation than were platelets in plasma, but this sensitivity was fully restored by the addition of plasma and partially restored with fibrinogen. Biotyping of the cultures revealed that none of the avirulent, B-type strains of F. necrophorum could aggregate platelets, whereas 13 of 16 virulent A type strains were positive. These results suggest that platelet aggregation by F. necrophorum is related to the virulence of this organism.

Aspirin↗
PubMed1984

Beta-lactamase activity of purified and partially characterized human renal dipeptidase.

Human renal dipeptidase has been concentrated from kidneys by homogenization, 1-butanol solubilization, and (NH4)2SO4 fractionation. Final purification was achieved by high-pressure liquid chromatography followed by affinity chromatography. The enzyme appeared to be homogeneous by polyacrylamide gel electrophoresis, and its molecular weight was estimated to be 220,000 by analytical high-pressure liquid chromatography. The molecular weight of human urinary dipeptidase was estimated by agarose gel filtration to be 218,000. Dissociation of human renal dipeptidase in sodium dodecyl sulfate-polyacrylamide gel electrophoresis produced a single polypeptide (Mr 59,000). These results suggest that the native enzyme contains four subunits of Mr 59,000. Analysis of the peptidase for zinc content gave 3.9 g atoms of zinc/mol of enzyme which supports the suggestion of a 4-subunit structure. Carbohydrate analyses of the purified human dipeptidase demonstrated that it was not a glycoprotein, a characteristic that distinguishes it from porcine and rat renal dipeptidase. beta-Lactamase activity of the purified human enzyme was demonstrated by measuring its activity against the two beta-lactam antibiotics, imipenem and SCH 29482. Kinetic analyses indicated that both antibiotics undergo enzyme-catalyzed hydrolysis at rates which could produce inactivation of the antibiotics within the human kidney. The beta-lactamase inhibitor, cilastatin, demonstrated reversible competitive inhibition of the peptidase-catalyzed hydrolysis of both antibiotics with the same Ki of 0.7 microM.

Carbohydrates↗
PubMed1984

A community health education approach to occupant protection.

The goal of enhancing motor vehicle occupant protection is vital to the public's health. Controversies about passive versus active protection and voluntary versus mandatory measures continue. A program which employed a combination of positive reinforcements (incentives) and wide-scale community education succeeded in raising the community seat belt usage rate from 24 to 41% in 6 months. This rate was sustained at 36% at six-month follow-up. This article reviews the major features of the "Seat Belts Pay Off" campaign and its evaluation and considers both theoretical and pragmatic issues pertinent to replicating the program in other community settings.

Adult↗
PubMed1983

Association of renal dipeptidase with the Triton-insoluble fraction of kidney microvilli.

Renal dipeptidase, previously identified as a component of renal microvilli, has been investigated to determine its orientation within this organelle. Digestion of porcine renal microvilli with papain released essentially all of aminopeptidase M, an outer membrane marker enzyme from the microvilli within one hour; whereas less than 10% of renal dipeptidase was released under the same conditions. Antibody to purified renal dipeptidase produced 50% inhibition of the purified enzyme at an antibody/antigen molar ratio of 2:1. Inhibition by the renal dipeptidase-directed antibody was not observed when the enzyme was bound within the microvillar structure. Demembranation of the microvilli with Triton X-100 resulted in a distribution of 68% of renal dipeptidase in the insoluble pellet and 32% in the soluble supernatant. The same detergent treatment released 92% of animopeptidase M into the supernatant. These results indicate that renal dipeptidase is not located at the luminal surface of the microvillus membrane where it would be available for release of papain, inhibition by antibody, or solubilization by detergent. Fractionation of the Triton-insoluble pellet with 2 M NaCl resulted in the release of 64% of the peptidase into a pellicle fraction separated from insoluble pellet and soluble supernatant. Finally extraction of Triton-insoluble pellet with 0.05 mM ATP-0.10 mM MgCl2 X 6 H2O solubilized 57% of the renal dipeptidase.

Animals↗