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Biomedical subjects

N A Punchard

Publications and source records attributed to N A Punchard.

At least 19 recordsLinked to original sources
PubMed2000

Analysis of the intestinal absorption of essential fatty acids in vivo in the rat.

The absorption and competition kinetics of the essential fatty acids (EFAs), linoleic acid (LA), alpha-linolenic acid (alphaLnA) and arachidonic acid (AA) in vivo were studied in the perfused rat jejunum. Uptake of each EFA on its own followed saturable kinetics at low luminal concentrations, suggesting a facilitative transport process, the affinity of which increased with chain length and degree of unsaturation. Absorption of one EFA was enhanced by low, whilst competitively inhibited by high, concentrations of a second EFA. Whereas LA and alphaLnA each interfered with the absorption of one another, both had little effect on AA. There was a strong inverse correlation between the relative unsaturation of an EFA and the change in Km of its absorption observed upon inhibition with another EFA. Overall, the results indicated a specific absorptive mechanism, probably involving a transport protein, the affinity of which increased with the degree of unsaturation of the EFA.

Animals↗
PubMed2000

Lipopolysaccharide and silica-stimulated mononuclear cell prostaglandin production in ulcerative colitis.

Basal, lipopolysaccharide (LPS) and silica-stimulated prostaglandin (PG) production were compared between peripheral blood mononuclear cells (PBMNC) from UC patients and healthy subjects (HS). Basal and LPS-stimulated PBMNC PGI2, but not PGE2, production was greater in UC. LPS stimulated both PGE2 and PGI2 by PBMNC from HS and UC patients. Silica stimulated production of both PGs by cells from HS but only PGE2 by cells from UC patients. The differences in responses to silica and LPS may result from differences in activation of NFkappaB or, alternatively, prior sensitisation to one of these agents. That PBMNC PGE2 production is not increased in UC, as it is in Crohn's disease, suggests that there are differences in PBMNC behaviour between these two diseases.

Adult↗
PubMed1998

Activation of nuclear factor kappa B in Crohn's disease.

OBJECTIVES AND DESIGN: The location and degree of activation of nuclear factor kappa (NFkappaB), a primary transcription factor that plays a regulating role in immune and inflammatory responses, was determined in Crohn's disease using full thickness specimens of bowel collected at surgery. MATERIALS AND METHODS: Resected specimens of inflamed and non-inflamed bowel were collected from thirteen patients with Crohn's disease and non-inflamed bowel from eleven control subjects. Prepared frozen sections were immunostained using a monoclonal antibody to the activated form of the p65 subunit of NFkappaB and the number of positive staining cells counted using a Lennox graticule. RESULTS: The number of cells positive for activated NFkappaB was significantly increased (p = 0.001 ) in all layers of inflamed Crohn's disease bowel, compared to non-inflamed bowel from controls. There was also a significant increase ( p = 0.009) in the number of positive cells, when compared to non-inflamed bowel from control subjects, in the submucosa of non-inflamed areas of Crohn's disease bowel. Cells positive for activated NFkappaB were provisionally identified by morphological criteria as mostly macrophages with some lymphocytes. There was no activation in endothelia. CONCLUSION: NFkappaB is activated within large mononuclear cells in all layers of inflamed areas of the bowel in Crohn's disease and may represent key events in the inflammatory process. Increased activation in the submucosa of non-inflamed Crohn's disease bowel provides further evidence of early immunological activation in macroscopically and microscopically uninvolved areas and an underlying abnormal immune system in Crohn's disease.

Adolescent↗
PubMed1998

Proliferative T-cell responses to human papillomavirus type 16 E5 are decreased amongst women with high-grade neoplasia.

Proliferative responses to human papillomavirus type 16 (HPV-16) E5 peptides were determined for short-term cell lines derived from peripheral blood mononuclear cells of 75 women. Cell lines from 16 of the 75 women proliferated in response to stimulation with pooled E5 peptides; this was most common for patients with low-grade squamous cervical intraepithelial lesions (LSIL; 6 of 15 patients, 40%) and less frequent for asymptomatic women with no cervical lesions (4 of 20, 20%), those with high-grade squamous intraepithelial lesions(HSIL; 5 of 33, 15%) and others with cervical cancer (1 of 7, 14%, P = 0.027). Amongst these patients, proliferative responses were exclusive to those that were positive for HPV-16 DNA (12 of 41, 29%; c.f. none of 13 HPV-16 DNA-negative subjects exhibited a proliferative response; P= 0023) and were again most prevalent amongst HPV-16 DNA-positive LSIL (6 of 14, 43%), as compared with HPV-16 DNA-positive HSIL (5 of 23, 22%) or HPV-16 DNA-positive cervical cancer patients (1 of 4, 25%, P > 0.05). In contrast, for asymptomatic women, responsiveness was statistically independent of HPV-16 DNA status, i.e. responsiveness in HPV-16 DNA-positive and DNA-negative subjects was observed in 3 of 15 (20%) and 1 of 5 (20%) cases, respectively (P > 0.05). There were no associations between detection of HPV-16 mRNA and proliferative responses (P> 0.05). These data suggest that HPV-16 E5-specific T-helper activity is depressed amongst women with HSIL lesions.

Adolescent↗
PubMed1994

Lipid peroxidation in rats chronically fed ethanol.

Chronic alcohol consumption induces cytochrome P450IIE1, enabling habitual abusers to consume far greater quantities of alcohol than normal subjects. This pathway of metabolism leads to the production of free radical species, which cause tissue damage through peroxidation of cell membranes. Groups of Wistar rats of equal male: female ratio (n = 24) were fed alcohol by gavage twice daily to achieve a dosage of 15 g/kg body weight. Mean peak blood alcohol concentrations of 186 mg% were produced in males and 156 mg% in females. The animals were allowed free access to standard laboratory chow and water. Control animals were pair-fed to the alcoholic group and fed isocaloric glucose by gavage. Groups of animals were killed between 9 and 11 am on consecutive mornings, after nocturnal feeding, since it has previously been shown that fasting rapidly depletes hepatic glutathione concentrations. Hepatic glutathione was measured by a spectrophotometric enzymatic recycling procedure. As a marker of lipid peroxidation hepatic malonaldehyde (MDA) was measured by high performance liquid chromatography. Hepatic MDA was increased in the alcoholic group (p < 0.001), as was total hepatic glutathione (p < 0.0001). Plasma concentrations of alpha-tocopherol were increased in the alcoholic group, but ascorbic acid and superoxide dismutase values were not affected. No sex differences were detected. The increased MDA production in the alcohol group is strong evidence that lipid peroxidation is a mechanism of alcoholic tissue damage. The rise in hepatic glutathione may be an adaptive response to free radical production that protects the rat against tissue damage.

Animals↗
PubMed1994

Resistance of erythrocytes to lipid peroxidation in alcoholic patients.

The ability of erythrocytes to resist lipid peroxidation may be a useful marker of antioxidant status in alcoholic patients, in whom depletion of dietary antioxidants may combine with increased production of free radicals to produce liver damage. There are conflicting reports, however, on the resistance of erythrocytes from alcoholic patients to lipid peroxidation. This study examined the relation between the degree of alcohol induced liver disease and the resistance of erythrocytes to chemically induced lipid peroxidation, measuring lipid peroxidation as malondialdehyde production. Erythrocytes from alcoholic patients with Child's C cirrhosis had significantly increased resistance to lipid peroxidation compared with both controls (p < 0.001) and alcoholic patients with moderate liver disease (p < 0.001). There was no difference between alcoholic patients with moderate liver disease and controls. Increased resistance to free radical initiated lipid peroxidation in alcoholic patients is related to liver damage rather than to alcohol abuse alone. This could arise from changes in the lipid composition of the erythrocyte membranes resulting from abnormal liver function. Tests of antioxidant status based upon the resistance of erythrocytes to free radical stress in vitro may therefore be flawed when such changes in membrane lipid composition can occur.

Adult↗
PubMed1994

A trial of oral zinc supplementation in psoriasis.

A controlled double-blind study of oral zinc supplementation was performed in twenty-five patients with chronic plaque psoriasis over twelve weeks to assess changes in both psoriasis (using the psoriasis area and severity index) and neutrophil zinc content. There were no statistically significant differences in the psoriasis area and severity index during the trial between the placebo- and zinc-treated group, nor in the zinc levels. There was therefore no evidence of a benefit from zinc supplementation in patients with this disease.

Administration, Oral↗
PubMed1993

Effect of thyroidectomy and adrenalectomy on changes in liver glutathione and malonaldehyde levels after acute ethanol injection.

At low concentrations ethanol is metabolized largely by alcohol dehydrogenase to acetaldehyde, while at higher concentrations a microsomal ethanol oxidising system (MEOS) is involved, namely cytochrome P450 IIE1, which also probably generates free radical species. In hyperthyroidism hepatic glutathione stores are depleted and net superoxide anion production occurs. In contrast, in hypothyroidism hepatic glutathione may be increased and thus renders the liver less sensitive to alcohol generated free radical production. Steroid hormones inhibit lipid peroxidation. Sixty male Wistar rats either underwent thyroidectomy, adrenalectomy, or sham procedures. Twenty control animals were pair fed with thyroidectomized animals, whilst another twenty fed ad libitum. An intraperitoneal injection of alcohol (75 mmol/kg) was given 2.5 h prior to sacrifice to half the animals in each group, the remainder receiving saline. The total hepatic glutathione contents of the pair fed and the ad libitum groups were not different, but were significantly increased by thyroidectomy (p = < 0.001). This effect was significantly reduced by alcohol (p < 0.01). The sham procedures and dietary restrictions had no effect. The ethanol alone reduced total hepatic glutathione, but this only reached statistical significance in the thyroidectomized and sham-adrenalectomized groups. Hepatic malonaldehyde (MDA) levels were significantly reduced in the thyroidectomy group but alcohol had no effect on them. We conclude that hypothyroidism increased hepatic glutathione status, presumably by reducing radical production by enzyme systems, which would otherwise consume this important scavenger. Long term exposure to ethanol with induction of MEOS is probably required for it to generate toxic levels of free radical species.

Adrenal Glands↗
PubMed1993

A randomized controlled study of evening primrose oil and fish oil in ulcerative colitis.

In a placebo-controlled study, 43 patients with stable ulcerative colitis were randomized to receive either MaxEPA (n = 16), super evening primrose oil (n = 19), or olive oil as placebo (n = 8) for 6 months, in addition to their usual treatment. Treatment with MaxEPA increased red-cell membrane concentrations of eicosapentaenoic acid (EPA) at 3 months by three-fold and at 6 months by four-fold (both P < 0.01), and doubled docosahexaenoic acid (DHA) levels at 6 months (P < 0.05). Treatment with super evening primrose oil increased red-cell membrane concentrations of dihomogamma-linolenic acid (DGLA) by 40% at 6 months (P < 0.05), whilst treatment with placebo reduced levels of DGLA and DHA at 6 months (both P < 0.05). Clinical outcome was assessed by patient diary cards, sigmoidoscopy and histology of rectal biopsy specimens. Super evening primrose oil significantly improved stool consistency compared to MaxEPA and placebo at 6 months, and this difference was maintained 3 months after treatment was discontinued (P < 0.05). There was however, no difference in stool frequency, rectal bleeding, disease relapse, sigmoidoscopic appearance or rectal histology in the three treatment groups. Despite manipulation of cell-membrane fatty acids, fish oils do not exert a therapeutic effect in ulcerative colitis, while evening primrose oil may be of some benefit.

Aged↗
PubMed1993

Review article: the mode of action of the aminosalicylates in inflammatory bowel disease.

Sulphasalazine and other 5-aminosalicylic acid (5-ASA)-containing drugs are used in the treatment of acute inflammatory bowel disease and in the maintenance of clinical remission. Despite their use for over 50 years, the mechanism of action of this class of drugs remains uncertain, although a number of possibilities are discussed in this review. It seems likely that the aminosalicylates are important free radical scavengers, can reduce leukotriene production and can inhibit the cellular release of interleukin-1, all of which are likely to be important in reducing the acute inflammatory response in inflammatory bowel disease. The effects of these drugs on prostaglandin production are more contentious, but it appears that 10(-5) to 10(-4) M concentrations stimulate production of prostaglandins which may be cytoprotective, while higher doses of these drugs inhibit prostaglandin production. The aminosalicylates may maintain remission in inflammatory bowel disease by preventing leucocyte recruitment into the bowel wall. The drugs inhibit the chemotactic response to leukotriene B4, reduce the synthesis of platelet activating factor and also inhibit leucocyte adhesion molecule upregulation.

Aminosalicylic Acids↗
PubMed1993

Inhibition of leucocyte adhesion molecule upregulation by tumor necrosis factor alpha: a novel mechanism of action of sulphasalazine.

The effects of the cytokine tumour necrosis factor alpha and the calcium ionophore A23187 upon CD11a, CD11b, CD11c and CD18 leucocyte membrane expression was analysed in whole blood using monoclonal antibodies and flow cytometry. Both agents significantly increased the density of CD11b/CD18 membrane expression on monocytes and granulocytes, but had no effects on adhesion molecule expression on lymphocytes. The effects of sulphasalazine, 5-aminosalicylic acid (5-ASA) and sulphapyridine upon adhesion molecule upregulation were then examined; 10(-3) and 10(-4) M sulphasalazine and 5-ASA significantly reduced tumour necrosis factor alpha induced CD11b/CD18 upregulation on monocytes and granulocytes but had no effects upon A23187 mediated upregulation. Sulphapyridine was inactive. These results suggest that sulphasalazine and 5-ASA may interfere with mechanisms of leucocyte recruitment in inflammatory bowel disease.

Adult↗
PubMed1993

Automated spectrophotometric method for determining oxidized and reduced glutathione in liver.

An enzymatic recycling method has been applied to the measurement of total and oxidized glutathione with a centrifugal analyzer. When the reduced form of glutathione (GSH) was masked with 2-vinylpyridine to measure the oxidized glutathione (GSSG), the time to ensure full derivatization was three times longer than has been reported. The method is quick, simple, accurate, and precise (1.27% for GSH, 3.3% for GSSG intraassay CV; 2.15% for GSH, 5% for GSSG interassay CV), and the automation allows large numbers of samples to be conveniently assayed.

Autoanalysis↗