Search PubMed⌕ Search

Biomedical subjects

D Y Graham

Publications and source records attributed to D Y Graham.

At least 379 records · Page 21Linked to original sources
PubMed1992

Selection of the chimpanzee over the baboon as a model for Helicobacter pylori infection.

Baboons (Papio sp.) and chimpanzees (Pan troglodytes) were screened for the presence of Helicobacter pylori. The gastric mucosae of the baboons were colonized by large spiral bacteria. However, a group of adult chimpanzees were identified that were free of spiral gastric bacteria, with five animals being recruited into an H. pylori challenge study. These animals were inoculated orogastrically with one of four strains of H. pylori and followed for up to 26 weeks. H. pylori was established in one of these animals during a primary challenge and in two other animals on secondary challenge. It was shown that the chimpanzee can be infected with H. pylori and that the inflammatory response in these animals mimics that seen in humans. Infection was marked by an antibody response to H. pylori-specific antigens in two animals. It was observed that H. pylori antibody-negative chimpanzees had no apparent infection by H. pylori or related bacteria. Thus serological screening of chimpanzees can be used to identify candidate animals for further evaluation.

Animals↗
PubMed1992

Factors influencing the eradication of Helicobacter pylori with triple therapy.

Helicobacter pylori infection has been associated with gastritis, duodenal ulcer, gastric ulcer, and the epidemic form of gastric carcinoma. Eradication of H. pylori infection has proven to be difficult. Recently, combinations of antimicrobial drugs have been shown to eradicate greater than 50% of infections; however, the results have proven variable, and the factors influencing effectiveness of therapy are unclear. In the present study, the effectiveness of a triple therapy for eradication of H. pylori infection was evaluated. Triple therapy consisted of 2 g tetracycline, 750 mg metronidazole, and five or eight tablets of bismuth subsalicylate daily in 93 patients (70 with duodenal ulcer, 17 with gastric ulcer, and 6 with simple H. pylori gastritis). Combinations of a sensitive urea breath test, serology, culture, and histology were used to confirm the presence of infection, eradication, or relapse. Eradication was defined as inability to show H. pylori greater than or equal to 1 month after ending therapy. The overall eradication rate was 87%. The factors evaluated for their effect on predicting eradication included age, gender, type of disease, duration of therapy, amount of bismuth subsalicylate [five or eight Pepto-Bismol tablets daily (Procter & Gamble, Cincinnati, OH)], and compliance with the prescribed medications. Stepwise regression showed that compliance was the most important factor predicting success; the success rate was 96% for patients who took greater than 60% of the prescribed medications and 69% for patients who took less. For those taking greater than 60% of the prescribed therapy, the eradication rates were similar (a) for patients receiving therapy for 14 days or when tetracycline and bismuth subsalicylate were taken for an additional 14 days; (b) for patients with duodenal ulcer, gastric ulcer, and simple H. pylori gastritis; and (c) whether five or eight bismuth subsalicylate tablets were taken. It is concluded that triple therapy is effective for eradication of H. pylori and that future studies need to take compliance into account for comparisons between regimens.

Adult↗
PubMed1992

Relationship of Helicobacter pylori to serum pepsinogens in an asymptomatic Japanese population.

A seroepidemiologic study of the prevalence of Helicobacter pylori infection in Japan was performed, and the relationship between serum pepsinogen I and II levels (markers of gastritis and gastric atrophy) and H. pylori infection was investigated. Four hundred and eighteen asymptomatic children and adults were studied. The prevalence of anti-H. pylori immunoglobulin G antibody increased with age. For persons born after 1950, the frequency of H. pylori infection increased at approximately 1% per year; for those born before 1950 the prevalence was high (70%-80%) and relatively constant. Serum pepsinogen I and II levels were significantly higher in H. pylori-infected volunteers than in H. pylori-uninfected volunteers [51.6 +/- 3 vs. 42.9 +/- 2 ng/mL (P less than 0.05) for pepsinogen I; 16.0 +/- 1 vs. 7.5 +/- 0.8 ng/mL (P less than 0.001) for pepsinogen II]. The ratio of pepsinogen I to pepsinogen II was significantly lower in H. pylori-infected volunteers (3.5 +/- 0.2) than in uninfected volunteers (6.3 +/- 0.3; P less than 0.001). The apparent decrease in prevalence of H. pylori accompanying the Westernization of Japan may eventually be accompanied by a reduction in the frequency of atrophic gastritis, the precursor lesion of the epidemic form of gastric carcinoma, and ultimately result in a decrease in the incidence of gastric carcinoma in Japan.

Adolescent↗
PubMed1992

Adherence and internalization of Helicobacter pylori by HEp-2 cells.

Helicobacter pylori colonizes the mucous layer of the stomach and the surface of gastric mucous cells. Although H. pylori is not generally thought of as invasive, it has been observed in the lamina propria and within vacuoles in the cytoplasm of epithelial cells. The authors report that isolates of H. pylori can enter into the cytoplasm of tissue culture epithelial cell lines such as HEp-2 cells. Intracellular uptake of H. pylori by HEp-2 cells is rapid and appears to require both the N-acetylneuraminyllactose-binding adhesin and another factor present only in living bacteria. Uptake of H. pylori was inhibited by ammonium chloride and chloroquine at concentrations that did not effect either adherence or bacterial viability. Dansylcadaverine, an inhibitor of receptor clustering and internalization, also inhibited uptake but not adherence of H. pylori. Uptake was completely inhibited when H. pylori and HEp-2 cells were incubated at 4 degrees C under conditions that did not effect bacterial adherence. Cytochalasin B, an inhibitor of phagocytosis, did not inhibit uptake. It is concluded that H. pylori is internalized either by receptor-mediated endocytosis or by a closely related pathway.

Adrenal Glands↗
PubMed1992

Short report: cefprozil for the eradication of Helicobacter pylori infection.

Helicobacter pylori infection has proven to be extraordinarily difficult to eradicate. Antimicrobial monotherapies have been particularly disappointing, with most eradication rates in the range of 0 to 15%. We evaluated cefprozil (250 mg q.d.s. for 14 days) in 12 H. pylori-infected subjects. The 13C-urea breath test was used to evaluate effectiveness of therapy. Eradication was defined as a negative urea breath test 4 to 6 weeks after the end of treatment. Suppression of H. pylori was demonstrated in 4 of 12 (33%) by a negative urea breath test two days after start of treatment. H. pylori infection was not eradicated in any subject (0%). Adverse events were intermittent and mild. Cefprozil does not appear to offer promise as monotherapy for the eradication of H. pylori.

Adult↗
PubMed1992

Review article: urease, gastric ammonium/ammonia, and Helicobacter pylori--the past, the present, and recommendations for future research.

The presence of ammonium in gastric contents was described in 1852; urease activity in the stomach was identified 70 years later. The discovery of gastric urease resulted in intense research activity to discover its origin, function, and relation to the gastric levels of ammonium and urea. Interest in urease waned in the 1960s as most pertinent questions appeared to have been addressed and there was strong evidence that gastric urease was not a property of the stomach but was of microbial origin. Identification of Helicobacter pylori as the source of urease in the stomach in the last decade has resulted in a rebirth of interest in gastric urease and its products. There is little actual evidence to support a role for toxicity of ammonia in relation to H. pylori and the bulk of the evidence suggests that the products of urease activity are not toxic and may even be beneficial. The purpose of this review is to examine the older literature and to examine new findings in the perspective of what is already known and to suggest areas remaining to be examined. We ask, 'What is old, what is new, and what needs to be done?'

Ammonia↗
PubMed1992

Urease-associated heat shock protein of Helicobacter pylori.

Helicobacter pylori urease is an extracellular, cell-bound enzyme with a molecular weight of approximately 600,000 (600K enzyme) comprising six 66K and six 31K subunits. A 62K protein is closely associated with the H. pylori urease, both in crude preparations and after gel filtration; this protein can be removed from the urease by ion-exchange chromatography without inactivating the enzyme. We purified this urease-associated protein and determined its N-terminal amino acid sequence. The sequence is 80% homologous (identical plus conserved amino acid residues) to the Escherichia coli GroEL heat shock protein (HSP), 75% homologous to the human homolog, and 84% homologous to the HSP homolog found in species of Chlamydia. Thus, the 62K urease-associated protein of H. pylori belongs to the HSP60 family of stress proteins known as chaperonins. Evidently this protein, HSP62, participates in the extracellular assembly and/or protection of the urease against inactivation in the hostile environment of the stomach.

Amino Acid Sequence↗
PubMed1992

Detection of Norwalk virus in stool by polymerase chain reaction.

A method of reverse transcription (RT) and polymerase chain reaction (PCR) for the detection of Norwalk virus in human stools was developed. A cationic detergent, cetyltrimethylammonium bromide, was found to effectively remove from stool extracts factors that inhibit the RT-PCR assay. The specificities of the tests were shown by hybridization of the amplified DNA with Norwalk virus-specific cDNA probes and a consistent correlation between virus detection in stools and infection of volunteers. RT-PCR detected virus in stool samples diluted 10(-4) and was about 100 times more sensitive than dot blot hybridization. In serial stool samples collected before and at different times after inoculation of 10 volunteers with Norwalk virus, 37 of 55 were positive by RT-PCR, but only 27 were positive by dot blot hybridization (chi 2 = 22.96; P less than 0.001). Further application of this method should allow detection of Norwalk virus in food or environmental samples such as shellfish and shellfish waters.

Adult↗
PubMed1992

Reverse transcription and polymerase chain reaction amplification of rRNA for detection of Helicobacter species.

Sequence data on Helicobacter pylori 16S rRNA were used to select two 22-base oligonucleotide primers for use in a polymerase chain reaction (PCR) for detection of H. pylori. H. pylori cells were treated with lysis buffer, boiled, and chloroform extracted. Reverse transcription of rRNA was followed by PCR amplification (RT-PCR) of the synthesized cDNA and 16S rRNA gene. The amplified PCR products were analyzed by agarose gel electrophoresis and Southern blotting. Using ethidium bromide-stained agarose gels, we were able to detect the expected 500-bp DNA fragment from as few as two H. pylori organisms per reaction. The specificity of the RT-PCR assay was tested with 27 clinical isolates and related reference strains; although the number of bacterial cells used per reaction was 10(5)-fold greater than the number of H. pylori organisms used, amplification was detected only with bacteria in the same genus, H. cinaedi and H. mustelae. Ten H. pylori organisms per biopsy specimen were detected on agarose gels when organisms were added to samples prepared from a processed colon biopsy sample. RT-PCR results were consistent with urea breath test and culture results in 14 of 15 gastric biopsy specimens; the specificity was 100%. RT-PCR of rRNA from H. pylori increased the sensitivity of pathogen detection at least 25- to 50-fold compared with that of previous PCR assays. This low level of detection by RT-PCR assay may prove to be well suited for verifying eradication following therapy.

Base Sequence↗
PubMed1992

Expression, self-assembly, and antigenicity of the Norwalk virus capsid protein.

Norwalk virus capsid protein was produced by expression of the second and third open reading frames of the Norwalk virus genome, using a cell-free translation system and baculovirus recombinants. Analysis of the expressed products showed that the second open reading frame encodes a protein with an apparent molecular weight of 58,000 (58K protein) and that this protein self-assembles to form empty viruslike particles similar to native capsids in size and appearance. The antigenicity of these particles was demonstrated by immunoprecipitation and enzyme-linked immunosorbent assays of paired serum samples from volunteers who developed illness following Norwalk virus challenge. These particles also induced high levels of Norwalk virus-specific serum antibody in laboratory animals following parenteral inoculation. A minor 34K protein was also found in infected insect cells. Amino acid sequence analysis of the N terminus of the 34K protein indicated that the 34K protein was a cleavage product of the 58K protein. The availability of large amounts of recombinant Norwalk virus particles will allow the development of rapid, sensitive, and reliable tests for the diagnosis of Norwalk virus infection as well as the implementation of structural studies.

Antibody Formation↗
PubMed1992

Polymerase chain reaction detection of Mycobacterium paratuberculosis and Mycobacterium avium subsp silvaticum in long term cultures from Crohn's disease and control tissues.

Thirty one cultures were established in MG3 medium from the intestinal tissues of 29 patients, including 18 with Crohn's disease, five with ulcerative colitis, and six non-inflammatory bowel disease controls. All cultures grew either acid fast bacilli or uncharacterized spheroplasts. Pellets from these cultures were coded and assayed blind for M paratuberculosis and M avium subsp silvaticum using IS900- and IS902-PCR (polymerase chain reaction) assays, respectively. IS900 and IS902 are multicopy DNA insertion elements specific for these two organisms. Six Crohn's disease cultures and a single non-inflammatory bowel disease control were positive for M paratuberculosis. A further six cultures were positive for M avium subsp silvaticum, of which two each were from Crohn's disease, ulcerative colitis, and non-inflammatory bowel disease controls. The intensity of the IS900-PCR signals indicated very low numbers of M paratuberculosis organisms and bore no relation to visible spheroplastic or bacillary mycobacterial growth. The results suggest that M paratuberculosis isolated from man exists in a form which hardly replicates if at all when cultured in MG3 medium in vitro, and are consistent with the involvement of this known animal enteric pathogen in a proportion of chronic enteritis in man.

Base Sequence↗
PubMed1992

Gastric adaptation to nonsteroidal anti-inflammatory drugs in man.

Adaptation describes the phenomenon in which visible gastric mucosal injury lessens or resolves completely despite continued administration of an injurious substance such as aspirin. Adaptation occurs in man although the mechanism remains unclear. Recent evidence suggests increased cell proliferation and correction of nonsteroidal anti-inflammatory drug induced reduction in gastric blood flow as possibly being important. Gastric erosions and ulcers in chronic nonsteroidal anti-inflammatory drug users represent failed adaptation. Gastric erosions and ulcers in chronic nonsteroidal anti-inflammatory drug users represent failed adaptation. The factors responsible for failure of adaptation are unknown but one clue is that there appears to be a dose-response effect relating anti-inflammatory dose and effectiveness of adaptation (i.e., adaptation is delayed, or less effective, when higher anti-inflammatory doses are administered). Gastric adaptation can be enhanced by co-therapy with synthetic prostaglandins but not with sucralfate or H2-receptor antagonists.

Adaptation, Physiological↗
PubMed1992

Helicobacter pylori infection in dental workers: a seroepidemiology study.

The finding of Helicobacter pylori in dental plaque suggested that dental workers may be at increased risk of acquiring H. pylori infection from occupational exposure. A cross-sectional survey of 239 dental workers from 37 Texas cities (including 89 dentists, 44 dental hygienists, 98 dental assistants, and eight dental students) was conducted. H. pylori infection was determined by the presence of IgG antibodies to H. pylori, using a specific and sensitive ELISA. Participants ranged in age from 19 to 72 yr (mean 34 yr) and the duration of dental practice ranged from 1 to 48 yr (mean 12 yr). Type of dental occupation, duration of practice, type of practice (public or private), instrument used for cleaning teeth (ultrasonic scaler or curette), and prevalence of upper gastrointestinal symptoms were determined by self-administered questionnaires and interviews. Eighty-two percent had no symptoms referable to the upper gastrointestinal tract. The overall prevalence of H. pylori infection was 24%: 17% in dentists, 18% in dental hygienists, 34% in dental assistants, and 25% in dental students. The prevalence increased significantly with age (p < 0.05). The prevalence of H. pylori infection was significantly higher in non-whites, 29 of 63 (46%), than whites, 29 of 176 (16%) (p < 0.001). Logistic regression analysis (dependent variable H. pylori) revealed no significant association between H. pylori infection and the type, duration, or volume of practice, or the type of cleaning instrument used. We conclude that dental workers are not at increased risk to H. pylori infection.

Adult↗
PubMed1992

Treatment of intractable hiccup with baclofen: results of a double-blind randomized, controlled, cross-over study.

Four patients with intractable hiccup were treated in a double-blind, randomized, placebo, cross-over study with an analogue of gamma-aminobutyric acid, Baclofen. There was a consistent and statistically significant (p = 0.03) improvement in hiccup severity with Baclofen, both subjectively (p = 0.03) and by hiccup-free periods (p = 0.003). The actual frequency of hiccup was not significantly altered by the medication. We propose that the mechanical aspects of hiccup are reduced by Baclofen, leading to a perceptual blockage and a decrease in the reflex severity induced by the gamma-aminobutyric acid analogue. We conclude that this medication may be useful for the treatment of intractable hiccup.

Aged↗
PubMed1992

The role of Helicobacter pylori in recurrent, functional abdominal pain in children.

Recurrent abdominal pain in children usually is considered to be functional in nature. We hypothesized that Helicobacter pylori infection might be the etiology of abdominal pain symptoms in some children with presumed functional abdominal pain. Therefore, we studied 20 children with a previous diagnosis of functional abdominal pain, using a 13C-urea breath test and an enzyme-linked immunosorbent assay for antibody to the H. pylori high molecular weight, cell-associated antigens. Two children had evidence of H. pylori infection, and both had clinical histories that suggested an acute H. pylori infection, at the onset of their abdominal pain. Seven children who had abrupt onset of their chronic abdominal symptoms were then identified prospectively. None of these patients had evidence of active H. pylori infection. We conclude that H. pylori infections are not common among children with recurrent abdominal pain, and are not predictable in such children, based on symptom patterns.

Abdominal Pain↗
PubMed1992

Ulcer recurrence following duodenal ulcer healing with omeprazole, ranitidine, or placebo: a double-blind, multicenter, 6-month study. The Omeprazole Duodenal Ulcer Study Group.

The present study determined whether the rate of relapse of duodenal ulcer was reduced after ulcer healing with omeprazole compared with ranitidine or placebo. It was made up of a double-blind, randomized, controlled multiple-center trial set within the United States. Patients were candidates if their duodenal or pyloric channel ulcer successfully healed in one of two large multicenter U.S. trials; one compared omeprazole, 20 mg once daily, before breakfast with ranitidine, 150 mg twice daily, and the other compared the same dose of omeprazole with placebo. Two hundred forty (73.8%) of the 325 patients with complete ulcer healing within 4 weeks of starting therapy who were eligible to enter the follow-up study were enrolled. There was no intervention. Endoscopic assessment of ulcer status was performed at 2, 4, and 6 months and whenever patients had symptoms thought to represent return of an ulcer. The lifetable relapse rates for duodenal ulcer according to initial ulcer therapy with omeprazole, ranitidine, or placebo were 76.7% [95% confidence interval (CI), 64%-89.3%], 59.8% (95% CI, 47.8-71.7%), and 50.4% (95% CI, 15.7%-85.2%), respectively. These rates were not statistically significantly different. Seventeen percent of recurrent ulcers occurred at a site different from that of the original ulcer. It is concluded that despite the more rapid rate of duodenal ulcer healing with omeprazole therapy, the rate of ulcer relapse appears similar and independent of whether ulcer healing was accelerated with omeprazole or ranitidine.

Adult↗