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Biomedical subjects

R McCulloch

Publications and source records attributed to R McCulloch.

28 records · Page 2Linked to original sources
PubMed1991

The influence of branched chain amino acids on colonic atrophy and anastomotic strength in the rat.

Conventional solutions of parenteral nutrients fail to reverse the colonic atrophy caused by starvation. This may be due to the absence from these solutions of the amino acid glutamine--a fuel for rapidly dividing cells such as colonocytes and fibroblasts. Although glutamine is unstable in solution, the infusion of branched chain amino acids (BCAA) increases the rate of synthesis and release of glutamine from skeletal muscle. We evaluated the hypothesis that the infusion of BCAA into undernourished rats would reduce the extent of mucosal atrophy and enhance the healing of anastomoses in the colon. Undernourished rats were randomized to receive 6 days of either a normal diet (Chow), conventional parenteral nutrition (CPN), or CPN supplemented with 1.8% BCAA (BCAA). The BCAA group had a higher plasma glutamine concentration than the Chow group (P less than 0.05). Compared with the CPN group, the BCAA group had the greater colonic mucosal weight (P less than 0.05) and colonic mucosal protein content (P less than 0.05), but there were no significant differences between groups in the bursting wall tension of the colon or the hydroxyproline content of the anastomoses. Although the infusion of BCAA has a beneficial effect on colonic atrophy, this did not result in the more secure healing of colonic anastomoses in this experimental model.

Amino Acids↗
PubMed1991

Can changes in transcardiac impedance appropriately detect ventricular fibrillation?

Transcardiac impedance, as measured between two implanted defibrillator patches, has been shown to vary in peak-to-peak magnitude in response to the contractions of the ventricles. These variations in transcardiac impedance are known as delta Z. This study was aimed at determining if there was a significant change in the magnitude of delta Z between that during normal sinus rhythm, that during ventricular fibrillation (VF), and if this change could be used as a detector of the onset of VF. This study was performed acutely on 14 anesthetized dogs.

Animals↗
PubMed1991

Differences in the pathological changes in dogs' hearts after defibrillation with extrapericardial paddles and implanted defibrillator electrodes.

A comparison was made between the pathological changes in the myocardium of eight dogs, each receiving about 90 joules of energy in a series of defibrillation discharges, delivered either between paddles placed against the pericardium (3 dogs) or between implanted Telectronics 040-105 defibrillation patch electrodes (5 dogs). The changes in the myocardium were most pronounced where the paddles had been applied to the pericardium. There was transmural damage beneath the left and right paddle positions and in the surrounding tissues. Extensive subepicardial and subendocardial myocyte damage was obvious histologically in the right ventricle of one of the patch dogs and in all of the paddle dogs. The percentage of damaged myocardial mass, both right ventricular and total involvement, was higher in the three paddle dogs compared with the five patch dogs. There was septal damage in the heart of one paddle dog. Necrosis of the right ventricular wall was observed in three of the patch dogs and in all the three paddle dogs. Scattered necrotic myocytes and some patches of mild necrosis up to 1-mm deep were observed in the left ventricle of the patch dogs (severity score 1-3). The necrosis was more extensive in the paddle dogs, ranging from mild necrosis less than 1-mm deep to marked necrosis incorporating half-to-whole ventricular wall thickness (severity score 3-5).

Animals↗
PubMed1990

Influence of branched chain amino acid infusions on wound healing.

Branched chain amino acids (BCAA) may serve as a major oxidative fuel for skeletal muscle during periods of starvation. This study compared the ability of protein-undernourished rats to heal musculo-aponeurotic wounds of the abdominal wall when they were infused with solutions containing 45% BCAA or 8% BCAA (conventional TPN). Although the provision of 45% BCAA tended to result in better nourished animals and significantly increased plasma glutamine concentrations, this was not associated with improved healing.

Amino Acids, Branched-Chain↗
PubMed1987

Enzyme-linked immunosorbent assay for Campylobacter pyloridis: correlation with presence of C. pyloridis in the gastric mucosa.

Antibody to Campylobacter pyloridis was measured by ELISA in the sera of 160 patients from whom gastric biopsy specimens were also obtained. The antigen was an acid-glycine extract of C. pyloridis, and titers ranged from 80 to 22,000 ELISA units (EU). Of 117 patients in whom C. pyloridis was detected microbiologically or histologically, 87 (74%) had a titer greater than or equal to 300 EU, and only one had a titer less than 150 EU. Of 43 patients in whom C. pyloridis was not detected, only two (5%) had a titer greater than 300 EU. Thus, for a titer of 300 EU the ELISA test had a specificity of 97% and a sensitivity of 81%. At 150 EU the specificity was 78%, and the sensitivity was 99%. Histological diagnosis of active chronic gastritis was associated with a high median ELISA titer (485 E), chronic gastritis with a much lower titer (150 EU), and normal histology with a titer of 110 EU. Discriminating use of this serological test could be of assistance to detect C. pyloridis in the gastric mucosa.

Adult↗
PubMedDate not supplied

Influence of glutamine and branched chain amino acids on the jejunal atrophy associated with parenteral nutrition.

Infusions of conventional parenteral nutrients (CPN) are associated with gut atrophy. This may be due to the absence of glutamine in such solutions. Although glutamine is a preferred gut nutrient, it is excluded from CPN because it is unstable at room temperature. This problem may be circumvented either directly by the infusion of fresh solutions of glutamine, or indirectly by the infusion of branched chain amino acids (BCAA). We evaluated the effect of infusing either glutamine, BCAA, or glutamine plus BCAA-enriched CPN on the rat jejunum. Sixty male Wistar rats were randomized to receive 6 days of either conventional parenteral nutrition (CPN), CPN plus 1.5% glutamine (GLN), CPN plus 2% BCAA (BCAA), CPN plus 0.8% BCAA and 1.0% glutamine (GLN/BCAA), or a normal oral diet (Chow). Standardized segments of jejunum were then removed for assessment. Compared with the CPN group, both the GLN/BCAA and the BCAA groups had greater mucosal weights (P less than 0.05) and mucosal protein concentrations (P less than 0.05), the GLN/BCAA group had greater jejunal weights (P less than 0.05), and the GLN group had an increased jejunal weight (P less than 0.05) and a higher crypt cell production rate (P less than 0.05). We conclude that the infusion of glutamine or BCAA-enriched parenteral nutrition improves jejunal morphology compared with conventional parenteral nutrition.

Amino Acids, Branched-Chain↗
PubMedDate not supplied

Effects of glutamine infusion on colonic anastomotic strength in the rat.

Glutamine is one of the primary respiratory fuels of the colon. However, it is not included in commercial preparations of parenteral nutrients because of its short shelf life. It has been suggested that colonic atrophy induced by conventional parenteral nutrition can be reversed by the intravenous infusion of fresh solutions of glutamine. This study evaluated the hypothesis that glutamine-enriched parenteral nutrition would enhance the strength of a standard colonic anastomosis in undernourished rats. After surgery, the rats were randomized to receive 6 days of postoperative support with either rat chow, conventional parenteral nutrition, or parenteral nutrition containing 1.2% glutamine. Measurement of colonic bursting tension failed to demonstrate any significant differences between the groups under study. In conclusion, the administration of 1.2% glutamine-enriched parenteral nutrition failed to influence the healing of colonic anastomoses in undernourished rats.

Amino Acids↗
PubMedDate not supplied

The influence of parenteral glutamine and branched-chain amino acids on total parenteral nutrition-induced atrophy of the gut.

We tested the hypothesis that the provision of glutamine and branched-chain amino acids would reverse the gut atrophy that accompanies parenteral nutrition. Three hundred seventy-five rats were randomized into 15 groups to receive either conventional parenteral nutrition, rat food, glutamine-enriched parenteral nutrition (0.5% to 2.5%), branched-chain amino acid-enriched parenteral nutrition (0.8% to 2.0%), or glutamine plus branched-chain amino acid-enriched parenteral nutrition (0.5%/0.4% to 1.25%/1/0%). When compared with effects of conventional parenteral nutrition, the infusion of either glutamine or branched-chain amino acids partially reversed, in a dose-dependent manner, atrophy of the small bowel as assessed by gut weight (p < .05), mucosal weight (p < .05), villous height (p < .05), crypt cell production rate (p < .05), and mucosal protein concentration (p < .05). There was no effect on the large bowel. These results suggest that the parenteral infusion of either glutamine or branched-chain amino acids partially reverses the small-bowel atrophy that is associated with the infusion of solutions of conventional parenteral nutrients.

Amino Acids, Branched-Chain↗