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Biomedical subjects

J G Morris

Publications and source records attributed to J G Morris.

At least 145 records · Page 8Linked to original sources
PubMed1995

Dietary soybean protein decreases plasma taurine in cats.

Commercial dry and canned diets fed to cats cause approximately two- and fourfold increase in the taurine requirement, respectively, as compared with that observed for purified diets. In two experiments, the effect of source and level of protein and fiber in the diet on the concentration of taurine in plasma and whole blood of cats was studied. All diets contained 1 g taurine/kg dry matter. When a casein-based diet containing either 25% or 50% protein was given to cats for 6 wk, no difference in plasma taurine concentration was observed; however, substituting soybean protein for casein resulted in a significant (P < 0.01) decrease in plasma taurine concentration of cats in the 50% soybean protein group, but not in the 25% soybean protein group. In Experiment 2, the food intake of cats was limited [26 g dry matter/(kg body weight.d)], and the protein was 30 or 60% of the diet. Cats fed 60% soybean protein or casein diets had significantly lower plasma taurine concentrations than cats fed a 30% casein diet, with the 60% soybean protein diet causing the greater decrease. There was no effect of either 2 or 4% soybean fiber on plasma taurine concentration as compared with the same diet without the added fiber. The taurine concentration in plasma was higher (P < 0.05) in male cats than in female cats. Protein source, amount in the diet and gender did not affect the whole blood taurine concentration. Cats given diets containing 60% casein or soybean protein diets excreted a greater amount of fecal total bile acid and total taurine than cats given a 30% casein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1995

Molecular genetics and the initiation of solventogenesis in Clostridium beijerinckii (formerly Clostridium acetobutylicum) NCIMB 8052.

A physical map of the Clostridium beijerinckii (formerly Clostridium acetobutylicum) NCIMB 8052 chromosome has been constructed, encompassing about 90 rare restriction sites. The 14 rrn operons together with about 40 genes have been assigned positions on the map. Genetic analysis and gene transfer have been developed in this organism to enable in vivo analysis of the roles of cloned genes using marker replacement technology. Experiments using the available genetic tools have shown that spo0A plays a cardinal role in controlling several aspects of the transition from exponential growth to stationary phase in C. beijerinckii. These include initiation of sporulation, accumulation of the storage polysaccharide, granulose, and production of acetone and butanol. Several C. beijerinckii and C. acetobutylicum genes concerned with fermentative metabolism, whose expression is modulated at the onset of solventogenesis, contain sequence motifs resembling 0A boxes in their 5' regulatory regions. This invites the speculation that they are under the direct control of Spo0A, and additional data are now required to test this prediction.

Base Sequence↗
PubMed1995

Age at onset: the major determinant of outcome in Parkinson's disease.

Factors at presentation which influenced the course of the disease and response to treatment were assessed in 125 de novo patients with Parkinson's disease. Ninety-eight patients were available for re-assessment at 5 years. Older patients presented earlier after the onset of symptoms, deteriorated more rapidly, and were significantly more likely to develop dementia and impairment of balance. Increasing age and symmetrical disease predicted the new appearance of imbalance. Age of onset did not predict dyskinesia or end of dose failure. A low tremor score at baseline and female gender were predictive of the early appearance of dyskinesia. Patients who experienced end of dose failure were taking a significantly higher dose of levodopa. Once dose and duration of treatment were corrected for, no baseline features were predictive of end of dose failure. The dose of levodopa at 5 years was positively correlated to baseline disease severity as measured by the Columbia score. We conclude that the age of onset of symptoms of Parkinson's disease is a major determinant of the course of the disease and response to treatment.

Adult↗
PubMed1995

Cholera.

Despite more than a century of study, cholera still presents challenges and surprises to us. Throughout most of the 20th century, cholera was caused by Vibrio cholerae of the O1 serogroup and the disease was largely confined to Asia and Africa. However, the last decade of the 20th century has witnessed two major developments in the history of this disease. In 1991, a massive outbreak of cholera started in South America, the one continent previously untouched by cholera in this century. In 1992, an apparently new pandemic caused by a previously unknown serogroup of V. cholerae (O139) began in India and Bangladesh. The O139 epidemic has been occurring in populations assumed to be largely immune to V. cholerae O1 and has rapidly spread to many countries including the United States. In this review, we discuss all aspects of cholera, including the clinical microbiology, epidemiology, pathogenesis, and clinical features of the disease. Special attention will be paid to the extraordinary advances that have been made in recent years in unravelling the molecular pathogenesis of this infection and in the development of new generations of vaccines to prevent it.

Antibody Formation↗
PubMed1995

The capsule and O antigen in Vibrio cholerae O139 Bengal are associated with a genetic region not present in Vibrio cholerae O1.

Vibrio cholerae O139 Bengal, although closely related to V. cholerae O1 El Tor, produces a polysaccharide capsule and has a distinct O antigen. We have identified a chromosomal region of at least 11 kb, as defined by three TnphoA mutations, that is required for the expression of both polysaccharides. Electron microscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis show that these TnphoA mutants have lost the abilities both to express capsule and to produce lipopolysaccharide beyond the core oligosaccharide. Reactivity with O139 typing serum and resistance to serum are also lost in the mutants. DNA probes for this region do not hybridize with O1 V. cholerae but do react with other vibrios, implying that the region was recently acquired.

Bacterial Capsules↗
PubMed1995

Identification and cloning of a novel plasmid-encoded enterotoxin of enteroinvasive Escherichia coli and Shigella strains.

We have employed a molecular genetic approach to characterize the nature of enteroinvasive Escherichia coli (EIEC) enterotoxic activity, as previously observed in Ussing chambers (A. Fasano, B.A. Kay, R.G. Russell, D.R. Maneval, Jr., and M.M. Levine, Infect. Immun. 58:3717-3723, 1990). The screening of TnphoA mutants of EIEC yielded a single insertion mutant which had significantly reduced levels of enterotoxic activity in the Ussing chamber assay. DNA flanking the insertion was used as a probe to screen for EIEC cosmid clones which conferred secretogenic activity. Such screening resulted in the identification of two overlapping cosmid clones which elicited significant changes in mucosal short-circuit current (Isc). Subcloning and nucleotide sequence analysis of a DNA fragment from one of the cosmid clones led to the identification of a single open reading frame which conferred this enterotoxic activity. By DNA hybridization, this gene (designated sen for shigella enterotoxin) was found in 75% of EIEC strains and 83% of Shigella strains and was localized to the inv plasmid of Shigella flexneri 2457T. By PCR, a sen gene with 99.7% nucleotide identity was cloned and sequenced from 2457T. A deletion in the EIEC sen gene was constructed by allelic exchange, resulting in significantly lower rises in Isc than were elicited by the wild-type parent; however, significant enterotoxic activity remained in the sen deletion mutant. To purify the Sen protein, the gene was cloned into the multiple cloning site of the expression vector pKK223-3. Purification of the sen gene product yielded a protein with a molecular mass of 63 kDa which elicited rises in Isc in the Ussing chamber. We believe that the sen gene product may constitute all or part of a novel enterotoxin in EIEC and Shigella spp.

Amino Acid Sequence↗
PubMed1995

Capsular polysaccharide-protein conjugate vaccines of carbotype 1 Vibrio vulnificus: construction, immunogenicity, and protective efficacy in a murine model.

Vibrio vulnificus causes septicemia and wound infections in immunocompromised humans. The capsular polysaccharide of Vibrio vulnificus (VvPS) is critical for virulence. We synthesized conjugate vaccines of carbotype 1 VvPS under conditions and in formulations suitable for human use. Purified VvPS was conjugated to tetanus toxoid (TT) or to inactivated V. vulnificus cytolysin or elastase by two different schemes. All conjugates elicited elevated anticapsular immunoglobulin G (IgG) and IgM and antiprotein IgG responses in mice compared with saline placebo. The conjugates prepared through caboxyl activation of VvPS (VvPS-TTa, VvPS-cytolysin, and VvPS-elastase) were more immunogenic than the one prepared through hydroxyl activation (VvPS-TTb). The protective efficacy of conjugated and unconjugated formulations of VvPS and that of protein carriers were evaluated in a mouse septicemia model. Eighty percent of mice actively immunized with VvPS-TTa vaccine survived challenge with carbotype 1 V. vulnificus, while VvPS-cytolysin and VvPS-elastase conjugates conferred 44 and 40% protection, respectively. Control mice immunized with VvPS, cytolysin, or elastase alone, or saline only, showed 70 to 100% mortality. VvPS-TTa vaccine is nontoxic, immunogenic, and protective in mice.

Animals↗
PubMed1995

Preliminary structure determination of the capsular polysaccharide of Vibrio cholerae O139 Bengal Al1837.

Vibrio cholerae O139 Bengal has recently been identified as a cause of epidemic cholera in Asia. In contrast to V. cholerae O1, V. cholerae O139 Bengal has a polysaccharide capsule. As determined by high-performance anion-exchange chromatography and 1H nuclear magnetic resonance analysis, the capsular polysaccharide of V. cholerae O139 Bengal strain Al1837 has six residues in the repeating subunit; this includes one residue each of N-acetylglucosamine, N-acetylquinovosamine (QuiNAc), galacturonic acid (GalA), and galactose and two residues of 3,6-dideoxyxylohexose (Xylhex). The proposed structure is [formula: see text]

Bacterial Capsules↗
PubMed1995

'Atypical' tremor.

The tremor present in a small number of patients who present with features of both Parkinson's disease (PD) and essential tremor (ET) is ill-defined. We therefore studied 8 such patients with 'atypical' tremor and compared them clinically to 11 PD and 10 ET patients in a double-blind, cross-over, placebo-controlled trial. Tremor was assessed via accelerometry and surface EMG. Tremor frequency and the acute tremorlytic response to propranolol were not useful in discriminating between groups. Over 80% of atypical and PD patients showed alternating EMG, whereas 90% of ET patients had synchronous EMG activity. Tremor amplitude improved by > 90% in 38% of atypical, 27% of PD and none of the ET patients after single-dose L-dopa/benserazide (300/75 mg), a response which was significantly different between the ET and PD groups. Failure to differentiate electrophysiologically and pharmacologically between the atypical and other groups probably relates to clinical heterogeneity in the atypical group.

Benserazide↗
PubMed1995

Vibrio cholerae O139 Bengal: emergence of a new epidemic strain of cholera.

In October 1992, a new strain of cholera, subsequently designated Vibrio cholerae O139 Bengal, was detected in Madras, India. This strain spread rapidly through the Indian subcontinent and has now been reported in many parts of Asia, with additional cases identified in travelers to North American and the Middle East. Phylogenetically, V. cholerae O139 Bengal is very closely related to "standard" V. cholerae O1 El Tor strains; it produces cholera toxin and causes an illness identical that seen with V. cholerae O1. However, prior immunity to V. cholerae O1 El Tor does not appear to protect against illness caused by V. cholerae O139 Bengal. O139 Bengal strains have a short, "semi-rough" O side chain and are encapsulated, changes that are likely to have accounted for their ability to cause disease in persons with prior exposure to cholera. These changes in surface structures appear to have resulted from a limited number of genetic modifications. The appearance of V. cholerae O139 Bengal may well herald the beginning of the eighth pandemic of cholera--and underscores the tremendous potential within nature for creation of new strains of "old" pathogens.

Animals↗
PubMed1994

Obligately anaerobic bacteria in biotechnology.

New obligately anaerobic bacteria are being discovered at an accelerating rate and it is becoming very evident that the diversity of anoxic biotransformations has been greatly underestimated. Furthermore, among contemporary anaerobes there are many that thrive in extreme environments including, for example, an impressive array of both archaebacterial and eubacterial hyperthermophiles. Free energy for growth and reproduction may be conserved not only via fermentations but also by anoxygenic photophosphorylation and other modes of creating transmembrane proton potential. Thus forms of anaerobic respiration in which various inorganic oxidants (or indeed carbon dioxide) serve as terminal electron acceptors have greatly extended the natural habitats in which such organisms may predominate. Anaerobic bacteria are, however, often found in nature as members of close microbial communities (consortia) that, although sustained by syntrophic and other relations between component species, are liable to alter their composition and character in response to environmental changes, e.g., availability of terminal oxidants. It follows that the biotechnological exploitation of obligately anaerobic bacteria must be informed by knowledge both of their biochemical capacities and of their normal environmental roles. It is against this background that illustrative examples of the activities of anaerobic bacteria are considered under three heads: 1. Biodegradation/Bioremediation, with special reference to the anaerobic breakdown of aromatic and/or halogenated organic substances; 2. Biosynthesis/Bioproduction, encompassing normal and modified fermentations; and 3. Biotransformations, accomplished by whole or semipermeabilized organisms or by enzymes derived therefrom, with particular interest attaching to the production of chiral compounds by a number of procedures, including electromicrobial reduction.

Bacteria, Anaerobic↗
PubMed1994

Helicobacter pylori: the missing link in perspective.

Helicobacter pylori, an organism responsible for a common human infection, may act as a cofactor to produce gastrointestinal disease in a significant minority. The exact mechanisms of transmission are still unclear, but likely involve direct person-to-person spread and fecal-oral or waterborne/environmental transmission. Infection is a necessary condition for the development of duodenal ulcers and chronic nonspecific gastritis. It also likely contributes to the development of gastric ulcers, and the intestinal-type gastric carcinoma, but further studies are needed to confirm these hypotheses. Multiple effective treatment regimens currently exists. We recommend using bismuth, metronidazole, and tetracycline as the initial regimen of choice. Unfortunately, the relative importance of bacterial virulence factors is still unclear when compared with host susceptibility factors, and much knowledge needs to be gained about pathogenesis before vaccine development can proceed.

Gastrointestinal Diseases↗
PubMed1994

Dietary cysteic acid serves as a precursor of taurine for cats.

The ability of cats to use dietary cysteic acid as a precursor for taurine was examined. For 39 wk, six groups of four specific-pathogen-free cats each were fed purified diets that provided either 1.25 g taurine or 0, 1.0, 2.0, 10 or 20 g cysteic acid/kg diet. Concentrations of taurine in plasma and whole blood were measured weekly for 13 wk and monthly until 39 wk. Muscle concentrations of taurine at 12 wk were measured on a biopsy sample of the semitendinosus muscle. Fecal and urinary excretions of taurine and cysteic acid at 17 wk were measured. Concentrations of taurine in plasma and whole blood were linearly and positively correlated with cysteic acid in the diet (r2 = 0.88). Urinary taurine, a major route of excess taurine excretion, was positively correlated with the cysteic acid concentration of the diet (r2 = 0.94). Muscle and whole-blood taurine concentrations were also positively correlated (r2 = 0.96) with dietary cysteic acid concentration. Gross and histopathological examinations were performed on cats fed diets containing 20 g cysteic acid/kg diet. No adverse gross clinical signs were observed in cats fed any diets containing cysteic acid; minor histopathologic changes of the pancreas and thyroid were found in three of four cats fed 20 g cysteic acid/kg diet. Results suggest that cats are able to use dietary cysteic acid as a precursor for taurine biosynthesis.

Administration, Oral↗
PubMed1994

Kittens choose a high leucine diet even when isoleucine and valine are the limiting amino acids.

This study was conducted to determine the effect of excess leucine on the dietary choice of kittens. The basal diets contained 16% (low nitrogen) or 24% (adequate nitrogen) amino acids and were limiting in isoleucine and valine. The addition of leucine to either of these basal diets has been shown to cause a transitory adverse effect on the growth and food intake of kittens. In separate experiments each basal diet was used to test three sets of choices: basal vs. basal + 10% leucine; basal + alanine vs. basal + leucine (isonitrogenous) and basal vs. basal + alanine. When offered basal vs. basal + excess leucine, the kittens chose significantly more of the excess leucine diet regardless of the level of nitrogen in the basal diet. When offered an isonitrogenous choice of excess alanine vs. excess leucine, the kittens selected somewhat more of the excess leucine diets over the excess alanine diets; this selection was sustained longer in kittens fed low nitrogen. In the third choice experiment (basal vs. basal + alanine), the group offered the low nitrogen diets exhibited no preferences, and the group offered adequate-nitrogen diets selected significantly more of the excess alanine diet. These results for kittens are opposite to those for rats, a species that will select a low protein basal or even a protein-free diet over a diet containing excess leucine.

Animals↗
PubMed1994

Nitrogen balance, plasma free amino acid concentrations and urinary orotic acid excretion during long-term fasting in cats.

The purpose of this study was to ascertain the changes in nitrogen balance, plasma free amino acid concentrations, urinary orotic acid excretion and body weight during long-term fasting in adult obese cats. Results from eight cats that fasted rather than eat an unpalatable diet are reported. After 5 to 6 wk of weight loss, six of the eight cats developed signs of hepatic lipidosis, and the livers of all cats were severely infiltrated with lipids. Cats lost (mean +/- SE) 33.2 +/- 1.4% of their pre-fasting body weight. Mean nitrogen balance (+/- SE) was -547 +/- 54 mg.d-1.kg-2/3 for the first week, and then the net nitrogen losses decreased to a plateau (-303 +/- 52 mg.d-1.kg-2/3) after 4 wk. Fasting was associated with a decrease in plasma concentration of essential amino acids. When plasma amino acid concentrations were considered individually, concentrations of alanine, methionine, taurine, citrulline, arginine and tryptophan decreased the most (> or = 50%), whereas concentrations of glutamine, glutamate and ornithine significantly increased. Orotic acid was not detected in the urine during the fast. After 1 wk of fasting, obese cats had reduced nitrogen excretion, but not to the same extent as has been shown in obese humans or obese rats. It is suggested that the availability of several amino acids may become limiting for liver protein synthesis during fasting and that these deficiencies may contribute to the development of hepatic lipidosis. Orotic acid was not linked to hepatic lipidosis caused by fasting in cats.

Amino Acids, Essential↗
PubMed1994

Assessment of the nutritional adequacy of pet foods through the life cycle.

Despite the lack of precise information on the requirements for many of the nutrients essential for cats and dogs and the paucity of information on the availability of nutrients in foods, many commercial diets support excellent growth, reproduction, and maintenance. However, these diets use empirical information that cannot be readily applied to the formulation of new diets. Progress in companion animal nutrition requires more precise information on requirements for various life stages (especially reproduction and maintenance), along with values for the bioavailability of nutrients in dietary ingredients. There is virtually no information on the bioavailability of nutrients for companion animals in many of the common dietary ingredients used in pet foods. These ingredients are generally byproducts of the meat, poultry and fishing industries, with the potential for wide variation in nutrient composition. Claims of nutritional adequacy of pet foods based on the current Association of American Feed Control Official (AAFCO) nutrient allowances ("profiles") do not give assurances of nutritional adequacy and will not until ingredients are analyzed and bioavailability values are incorporated. The AAFCO feeding test provides a superior method for assessing nutritional adequacy to the profile, although the current protocol has procedural and interpretative limitations.

Animal Feed↗
PubMed1994

Microbial degradation of taurine in fecal cultures from cats given commercial and purified diets.

Freshly passed feces were collected from cats (n = 5-7) given cooked and uncooked commercial canned-type diets, casein and soy protein containing purified diets and a commercial extruded diet. The feces were anaerobically cultured in medium containing either taurine, taurocholic acid or [2-3H]taurine for 24 h at 37 degrees C. Taurine degradation in cultures was greatest for cultures from cats receiving diets reputed to cause taurine depletion. Diaminopimelic acid in feces indicated that differences in taurine degradation rate among groups was associated with differences in bacterial numbers in feces. After 6 h of incubation, < 10% of taurocholate and > 60% of taurine remained. Nearly all the tritium on the labeled taurine was recovered as water. These results indicate that deconjugation and deamination are the initial steps in microbial catabolism of taurocholic acid and that enteric microbial growth may be a major determinant of dietary taurine requirement of cats.

Animal Feed↗