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Biomedical subjects

R H Davis

Publications and source records attributed to R H Davis.

At least 73 records · Page 4Linked to original sources
PubMed1990

Opportunistic developmental surveillance in general practice.

The importance of the developmental surveillance of children is generally accepted. One method which could be used in general practice is opportunistic surveillance, where the doctor makes use of contacts with children in the surgery to assess their development, and offer advice and health education to parents where appropriate. This study describes an audit of opportunistic developmental surveillance in one general practice. It was found that 95% of a cohort of 78 children had been assessed at least once by the time they were one year old. In addition, at two points in the study, after one and two years, it was found that 81% of children aged two years or less in the practice had had a recent assessment. This level of surveillance compares favourably with reported attendance rates in clinics.

Adolescent↗
PubMed1990

Treatment of peptic ulcer in general practice and in hospital: a comparison of omeprazole and cimetidine.

The aim of this study was to compare duodenal ulcer healing and symptom relief after two and four weeks treatment with omeprazole or cimetidine in groups of patients treated in general practice and as hospital out-patients. It was a randomised, double-blind, parallel group study with stratification for trial centre (hospital or GP). Endoscopy was performed at entry, after two weeks and, if unhealed at two weeks, after four weeks. All endoscopies were carried out in hospitals. In all, 189 patients were randomised (98 omeprazole, 91 cimetidine), 79 (42 per cent) of which by GPs, to either omeprazole 20 mg om (n = 41) or cimetidine 800 mg nocte (n = 38) for two to four weeks. After two weeks, ulcer healing occurred in 56 per cent (omeprazole) and 29 per cent (cimetidine) (p less than 0.05) of patients treated by GPs, and 67 per cent (omeprazole) and 36 per cent (cimetidine) (p less than 0.005) of those treated as hospital out-patients. Similar differences in healing rates were seen after four weeks. Omeprazole produces faster duodenal ulcer healing than cimetidine whether patients are treated as hospital out-patients or by GPs.

Adolescent↗
PubMed1989

Comparison of the effects of two lathyrogens on the reproductive system of the laying hen.

The effects of two lathyrogens (beta-aminopropionitrile and semicarbazide) on the reproductive system of the laying hen were compared by measuring the changes in the ovary and oviduct associated with a diminished egg production rate. The laying hens were fed diets containing either beta-aminopropionitrile, the toxic constituent of certain legume seeds in the genus Lathyrus or semicarbazide to induce lathyrogenic effects in which reduced egg production was one of the toxic effects. The gross examination of the reproductive system of the hens revealed that ovarian activity was greatly impaired. The reduced egg production after feeding beta-aminopropionitrile was due to the reduced growth rate of the ovary, and in the case of semicarbazide, to the atresia of large yolky follicles.

Aminopropionitrile↗
PubMed1989

The effect of gamma irradiation on injectable human amnion collagen.

The effect of gamma irradiation on the physicochemical properties of injectable human amnion collagen was investigated. Pepsin-extracted human amnion collagen was purified, reconstituted, and irradiated with varying doses of gamma irradiation (0.25 Mrads to 2.5 Mrads). Gamma irradiation had a significant impact on the physical characteristics of the collagen. The neutral solubility of collagen in PBS at 45 degrees C was decreased from 100% for the nonirradiated control sample to 16% for the 2.5 Mrads irradiated sample. SDS polyacrylamide gel electrophoresis also demonstrated the dose-dependent effect of gamma irradiation on collagen cross-links. Electron microscopic observation revealed that even at low irradiation dose (0.25 Mrads), collagen fibril diameter increased. The average diameter was 50 nm for nonirradiated control fibrils, while 4.4 percent of the irradiated collagen fibrils had a diameter greater than 100 nm. Irradiated collagen showed little evidence of damage. Well-preserved cross-striations were found in collagen fibrils at all doses of irradiation. Native amnion collagen irradiated with gamma rays demonstrated a slight increase in resistance to collagenase degradation compared with nonirradiated native collagen samples. Increased resistance to collagenase did not correlate with increasing irradiation dose. After 30 min of incubation at 37 degrees C, both irradiated and nonirradiated collagen was completely digested by collagenase. However, gamma-irradiated collagen did become more sensitive to hydrolysis by trypsin. The higher the irradiation doses used, the greater sensitivity to trypsin was observed. At 0.25 Mrads irradiation only a slight increase was found. No marked differences in amino acid composition were noted among the high dose irradiated, low dose irradiated and control amnion collagen.

Amino Acids↗
PubMed1989

Uptake, intracellular binding, and excretion of polyamines during growth of Neurospora crassa.

In Neurospora crassa mycelia, the amounts of the main polyamines, putrescine and spermidine, are approximately 0.8 and 18 nmol/mg, dry weight. We wished to know what determines these pool sizes. In the growth medium, externally added polyamines enter cells largely by a nonsaturable, diffusional system. In a mutant unable to polyamines, internal and external spermidine appear to equilibrate across the cell membrane during growth. However, this was true only after an intracellular "sink," with a capacity equal to the amount of spermidine found in wild-type cells, had been saturated. We speculate that internal anionic binding sites, detectable in permeabilized cells, sequester virtually all of the spermidine normally found in exponentially growing N. crassa. Further evidence for this view was that in mature, stationary cultures, excess spermidine is excreted. Putrescine is also excreted if its concentration in the cell is abnormally high. The control of pool size by intracellular binding and excretion may be an advantage in this pathway, because feedback inhibition does not prevail, enzyme regulation is by comparison slow, and excessive polyamines are toxic.

Arginase↗
PubMed1989

Phorbol esters induce retrograde myoelectric activity in rabbit ileum in vivo.

We demonstrated a unique myoelectric response to phorbol esters and a diacylglycerol, 1-oleoyl-2-acetyl-snglycerol, in rabbit ileal loops. This retrograde activity, the orad migrating complex (OMC), was devoid of slow-wave distortion or alterations in slow-wave frequency. The OMC was not inhibited by the cyclooxygenase inhibitor indomethacin or enhanced by addition of the calcium ionophore A23187. The OMC occurred after 4 beta-phorbol 12-myristate 13-acetate, a phorbol ester known to activate protein kinase C, and after 4 alpha-phorbol 12,13-didecanoate, one that does not. Therefore, these studies provide initial evidence that the myoelectric activity induced by phorbol esters and a diacylglycerol is most likely in addition to the activation of protein kinase C.

Animals↗
PubMed1989

Aloe vera and gibberellin. Anti-inflammatory activity in diabetes.

Aloe vera inhibits inflammation and adjuvant-induced arthritis. The authors' laboratory has shown that A. vera improves wound healing, which suggests that it does not act like an adrenal steroid. Diabetic animals were used in this study because of their poor wound healing and anti-inflammatory capabilities. The anti-inflammatory activity of A. vera and gibberellin was measured in streptozotocin-induced diabetic mice by measuring the inhibition of polymorphonuclear leukocyte infiltration into a site of gelatin-induced inflammation over a dose range of 2 to 100 mg/kg. Both Aloe and gibberellin similarly inhibited inflammation in a dose-response manner. These data tend to suggest that gibberellin or a gibberellin-like substance is an active anti-inflammatory component in A. vera.

Aloe↗
PubMed1989

Wound healing. Oral and topical activity of Aloe vera.

The influence of Aloe vera, orally and topically, on wound healing was studied. Wounds were induced on both sides of the vertebral column of ICR mice using a biopsy punch. For the oral study, experimental animals received A. vera in their drinking water for 2 months, whereas the control animals received only water. In the topical study, experimental animals were given 25% A. vera in Eucerin cream topically. The control animals received cream only. A 62.5% reduction in wound diameter was noted in mice receiving 100 mg/kg/day oral A. vera and a 50.8% reduction was recorded in animals receiving topical 25% A. vera. These data suggest that A. vera is effective by both oral and topical routes of administration.

Administration, Oral↗
PubMed1989

Anti-inflammatory activity of Aloe vera against a spectrum of irritants.

The authors have evaluated the spectrum of anti-inflammatory activity of A. vera in a number of models of inflammation in the hind paw of the experimental rat induced by kaolin, carrageenan, albumin, dextran, gelatin, and mustard. Croton oil was used in a topical model of inflammation to determine the oral activity and time-dependent dosing of A. vera. The authors found that A. vera was active in all models of inflammation. Of the various irritants tested, A. vera was especially active against gelatin-induced and kaolin-induced edema and, in contrast, had minimal activity when tested against dextran-induced edema. Oral activity of A. vera was demonstrated to be dependent on the presence of anthraquinones. The various irritant-induced edema models provided a broad spectrum of anti-inflammatory activity for A. vera.

Aloe↗
PubMed1989

Processed Aloe vera administered topically inhibits inflammation.

Aloe vera preparations were evaluated for topical anti-inflammatory activity using the croton oil-induced edema assay. The results show that small amounts of A. vera given topically will inhibit inflammation induced by a moderate amount of irritant. In general, the decolorized Aloe was more effective than the colorized Aloe (with anthraquinone). A 47.1% inhibition of inflammation was obtained by 5% decolorized irradiated Aloe. These results may be used as a baseline to assess the biologic activity of A. vera in the treatment of inflammation by podiatric physicians.

Administration, Topical↗
PubMed1988

Lathyrism in laying hens and increases in egg weight.

The cause of the increased egg weight in hens with lathyrism was investigated by feeding laying birds with diets containing beta-aminopropionitrile, the toxic principle of certain legume seeds in the genus Lathyrus. There was a significant increase (P less than 0.01) in the amount of albumen in the egg owing to an increased formation of thin white. The water permeability of the shell membranes demonstrated an increased porosity and a loss of tensile strength which contributed not only to a high water uptake but also to abnormalities of the shape of eggs during 'plumping'. It was concluded that a defect in the shell membrane protein system alters the membrane's general properties and that the increased egg weight in lathyrism is a result of the defect.

Aminopropionitrile↗
PubMed1988

Putrescine and spermidine control degradation and synthesis of ornithine decarboxylase in Neurospora crassa.

Neurospora crassa mycelia, when starved for polyamines, have 50-70-fold more ornithine decarboxylase activity and enzyme protein than unstarved mycelia. Using isotopic labeling and immunoprecipitation, we determined the half-life and the synthetic rate of the enzyme in mycelia differing in the rates of synthesis of putrescine, the product of ornithine decarboxylase, and spermidine, the main end-product of the polyamine pathway. When the pathway was blocked between putrescine and spermidine, ornithine decarboxylase synthesis rose 4-5-fold, regardless of the accumulation of putrescine. This indicates that spermidine is a specific signal for the repression of enzyme synthesis. When both putrescine and spermidine synthesis were reduced, the half-life of the enzyme rapidly increased 10-fold. The presence of either putrescine or spermidine restored the normal enzyme half-life of 55 min. Tests for an ornithine decarboxylase inhibitory protein ("antizyme") were negative. The regulatory mechanisms activated by putrescine and spermidine account for most or all of the regulatory amplitude of this enzyme in N. crassa.

Cyclohexylamines↗
PubMed1988

Nutritional and biochemical factors influencing the biological effects of cyanide.

Investigation of the dietary interaction between cyanide and selenium in the chick, whereby cyanide alleviates selenium toxicity, suggests that cyanide alters metabolic reductive potential. Cyanide enhances the elimination of selenium as dimethyl selenide, the formation of which requires both reducing equivalents and methyl groups. Even when the methionine supply is adequate, meeting the need for the methyl groups, the interaction can be lost if there is a deficiency of certain micronutrients or an excess of vitamin K. Cyanide reduces liver glycogen, implying greater emphasis on anaerobic metabolism through inhibition of cytochrome oxidase. This may increase reductive potential but may also result in increased free radical production, processes that can be modified by levels of micronutrients. There is no evidence that an excess of sulphur amino acids can markedly enhance cyanide detoxification, although, for reasons that are not yet clear, cystine may be beneficial. However, the balance of dietary amino acids may be more critical than had been realized, because an excess of alanine appears to exacerbate cyanide toxicity.

Amino Acids, Sulfur↗
PubMed1988

Effects of domperidone in patients with chronic unexplained upper gastrointestinal symptoms: a double-blind, placebo-controlled study.

The effects of domperidone, a peripherally acting dopamine antagonist, were compared with those of placebo in a double-blind randomized study in 16 patients with idiopathic gastric stasis, chronic symptoms of "nonulcer dyspepsia" (including nausea, vomiting, and abdominal pain), and altered gastroduodenal motility. Patients received either domperidone or placebo orally (20 mg before meals and at bedtime) for six weeks. Symptoms were assessed by daily diaries kept by the patients for two weeks while receiving no medication for their gastrointestinal complaints (baseline), and throughout the six-week treatment phase. Studies of gastric emptying of a radiolabeled solid-phase meal were performed at baseline and six weeks after treatment. All patients had delayed gastric emptying at baseline, defined as a half-emptying time of more than mean + 1 SD (from studies of normal controls). An 18- to 24-hr recording of gastroduodenal motor function during fasting was also performed at baseline and after six weeks of either domperidone or placebo treatment. After six weeks of treatment, the symptom scores significantly improved in the domperidone group (P less than 0.05), but not in the placebo group. Gastroduodenal motor activity was unchanged from baseline recordings after six weeks. Solid-phase gastric emptying also showed no improvement in either the domperidone or placebo group of patients. Although domperidone therapy had no significant effect on motility, it appears to be an effective drug for the treatment of the symptoms of nonulcer dyspepsia.

Adult↗
PubMed1988

Gastric emptying in infants with gastroesophageal reflux. Measurement with a technetium-99m-labeled semisolid meal.

It is well established that liquid emptying occurs in the absence of motor activity of the stomach. In contrast, solid-phase emptying is controlled in part by antral peristalsis and is, therefore, a more precise indicator of gastric motility. We developed a semisolid, radionuclide gastric emptying test using rice cereal and technetium-99m-sulfur colloid to assess antral physiology in infants with vomiting. Computer-programmed mathematical models were used to determine the shape of a line that best fit our emptying data points. Linear, simple exponential [f = 2-(t/t1/2)], and power exponential [f = 2(t/t1/2)beta] patterns of emptying were calculated, where f is the fraction of the meal remaining in the stomach at time t, and t1/2 is the time when 50% of the meal has emptied and is a determinant of the shape of the curve. In infants with simple regurgitation (chalasia) and those with vomiting and failure to gain weight, we made statistical comparisons between gastric emptying patterns after analysis of the mean percentage of retained radionuclide at 120 min, calculated t1/2, and area under the curve. The coefficient of determination, R2, was calculated as an index of whether a curve provided goodness of fit to the data. Differences between groups of patients were statistically significant for all parameters of each mathematical model. However, higher coefficients of determination were noted in the power exponential model. The data suggest that the power exponential mathematical model provides the best analysis of the gastric emptying patterns for infants with chalasia and those with vomiting and failure to gain weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗