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Biomedical subjects

R C Harris

Publications and source records attributed to R C Harris.

212 records · Page 12Linked to original sources
PubMedDate not supplied

Variation in the concentration of long chain free fatty acids in equine plasma over 24 hours.

The primary aim of this study was to examine the within-day variation in the concentration of total and individual long chain free fatty acids (C > 14) in normally fed horses. Plasma samples were collected over a 24 h period from 12 resting horses during three separate sessions (six horses in the first session and three in the second and third). Samples were analysed for individual long chain free fatty acids (FFA) and glucose. During normal feeding, the predominant FFA in plasma were palmitic (C16:0), linoleic (C18:2), oleic (C18:1), stearic (C18:0) and linolenic (C18:3). Together these acids constituted over 90% of the total concentration. Other FFA present were myristic (C14:0) and palmitoleic (C16:1) both of which constituted < 5% of the total concentration. Ten out of the 12 horses sampled exhibited an early morning increase in FFA (P < 0.001) localized around 0700 h and which was independent of feeding. The mean concentration of total FFA increased 4.5 fold (range 2.0-8.5) between 0400 and 1000 h. The predominant FFA showed the largest increase.

Analysis of Variance↗
PubMedDate not supplied

ATP loss with exercise in muscle fibres of the gluteus medius of the thoroughbred horse.

Muscle ATP loss with exercise has implications both to the causes of fatigue and muscle damage. To study this at the single muscle fibre level, five trained thoroughbred horses performed consecutive 90 second gallops on an inclined treadmill followed by a final gallop to fatigue. Biopsies of the m. gluteus medius were taken at rest, post-exercise and during 24 hour recovery. Blood lactate was 20.0 mmol litre-1 or more, and plasma NH3 300-800 mumol litre-1, following the final gallop. Minimal changes occurred in the plasma markers, CK and AST. ATP loss with exercise was 32.2 (SD 12.2) per cent. Following exercise single fibre ATP contents showed a much broader distribution than at rest, with contents in some close to zero. Following five and 24 hour recovery, however, frequency distribution curves were close to those seen at rest. There was no difference in the ATP contents of types I, IIa and IIb at rest of with exercise or recovery. The results pointed to marked heterogeneity between individual fibres in their biochemical response with exercise, independent of fibre type.

Adenosine Triphosphate↗
PubMedDate not supplied

Effect of allopurinol on the formation of reactive oxygen species during intense exercise in the horse.

Allopurinol was administered to six horses in a cross-over study to determine the relative contribution of xanthine oxidase (XO) activity to the formation of reactive oxygen species (ROS) in the horse during intense exercise. Exercise increased the mean (SEM) plasma lipid hydroperioxide concentration to a maximum of 492.7 (33.4) microM within one minute of exercise completion and maximum levels of both oxidised glutathione (GSSG) in haemolysates of red blood cells and the glutathione redox ratio (GRR) occurred 20 minutes after exercise (87.2 [12.2] microM and 8.9 [0.9] per cent, respectively). Allopurinol significantly reduced lipid hydroperoxides, GSSG and the GRR at the corresponding maximal times after exercise measured during control exercise (217.5 [32.1] microM. 63.8 [8.6] microM and 6.8 [0.7] per cent, respectively). Significantly higher levels of hypoxanthine and xanthine were measured after exercise in the plasma of horses that received allopurinol than in control horses, although uric acid levels remained constant. In control horses, plasma uric acid concentrations increased after exercise to a maximum 20 minutes after exercise of 28.1 (2.6) microM, significantly higher than in horses given allopurinol (9.6 [1.3] microM). The results show that the inhibition of XO by allopurinol leads to a decrease in the formation of ROS during exercise, and thus a reduction in oxidative stress.

Allopurinol↗
PubMedDate not supplied

The concentration of creatine in meat, offal and commercial dog food.

The concentrations of creatine (Cr), phosphorylcreatine (PCr) and creatinine (Cn) were determined in a variety of meats, before and after cooking by boiling, in a range of commercially available canned dog foods, in rendered and dried meat products and in commercially available dry dog foods. None of the samples contained PCr. Uncooked chicken, beef and rabbit meat contained approximately 30 mmol kg-1 of Cr. Ox-heart and ox-liver had Cr concentrations of 22.5 and 2.3 mmol kg-1, respectively. Canned dog foods had Cr concentrations of 0.5 to 2 mmol kg-1. Dried meat samples had Cr concentrations of 90 to 100 mmol kg-1 dry weight. In contrast, the Cr concentration of dried rendered meat meal was 3 mmol kg-1 dry weight or less. Dry dog foods contained 0.5 to 4 mmol kg-1 dry weight of Cr. The results indicate that in the canned dog foods, the dried meat samples and the dried rendered meat meal creatine had been degraded to variable extents to creatinine.

Animal Feed↗
PubMedDate not supplied

Carnosine, anserine and taurine contents in individual fibres from the middle gluteal muscle of the camel.

High muscle carnosine und anserine contents contribute significantly to intra-cellular physico-chemical buffering. Our aim was to measure carnosine, anserine and taurine contents directly in individual type I, IIA and IIB fibres from the middle gluteus muscle of the camel. Mean carnosine contents in type I, IIA and IIB were 24.6 +/- 9.2, 39.4 +/- 11.4 and 42.8 +/- 18.8 mmol kg-1 dry weight (dw), respectively. Mean anserine contents in type I, IIA and IIB fibres were 30.0 +/- 8.4, 37.3 +/- 10.1 and 34.5 +/- 9.7 mmol kg-1 dw, respectively. Mean taurine contents in type I, IIA and IIB fibres were 42.4 +/- 15.9, 20.3 +/- 12.9 and 24.7 +/- 15.9 mmol kg-1 dw, respectively. Higher carnosine contents in type II fibres emphasise the importance of carnosine to intra-muscular acid-base regulation. A specific role for taurine in type I fibres in unclear.

Animals↗
PubMedDate not supplied

Mechanical stretch/relaxation stimulates a cellular renin-angiotensin system in cultured rat mesangial cells.

Angiotensin II (Ang II) may play a significant role mediating intraglomerular hypertension and glomerular sclerosis. Therefore, we investigated whether a model of pressure-induced stress, mechanical stretch/relaxation, affected the renin-angiotensin system (RAS) in cultured rat mesangial cells. Type 1 Ang II receptor (AT1R) expression was assessed by 125I-Ang II binding and quantitative reverse-transcription polymerase chain reaction. Stretch/relaxation increased steady-state AT1R mRNA levels as well as specific [125I]Ang II binding. Increased AT1R expression was associated with altered AT1R signaling. Ang II (100 nM) increased total phosphoinositide hydrolysis in control cells (186 +/- 25%, n = 6; p < 0.025 vs. no treatment). However, stretch/relaxation for 48 h further augmented AT1R-mediated PI hydrolysis (293 +/- 38%, n = 6; p < 0.025 vs. Ang II treatment alone). We examined other RAS components in mesangial cells subjected to stretch/relaxation. Angiotensinogen, determined by radioimmunoassay of Ang I generation in conditioned media, increased with stretch/relaxation, and reverse-transcription polymerase chain reaction demonstrated increased angiotensinogen gene expression in stretch/relaxation-treated cells. However, renin activity and angiotensin-converting-enzyme-like activity were unaffected by stretch/relaxation. Thus, mesangial cells maintain a local RAS similar to those described in other tissues, and AT1R expression and angiotensinogen production in this cellular RAS are increased by stretch/relaxation. It is likely that mesangial cells in vivo, exposed to variations in intraglomerular pressure, may regulate their responses via a local RAS.

Angiotensin II↗
PubMedDate not supplied

Review of selected bacterial enterotoxins and their role in gastroenteritis.

The study of enterotoxins began in earnest approximately 30 years ago with characterization of the cholera toxin. So far, more enterotoxins have been associated with Gram-negative rather than Gram-positive bacteria. These substances can be roughly divided into the cytotonic variety, which primarily interfere with intestinal cell metabolism, and those which are cytotoxic, responsible for cell destruction. Most cytotonic enterotoxins activate cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate (cGMP) producing watery diarrhea, resulting from fluid and electrolyte flux. This typically results after binding to a toxin-specific receptor site on the small intestinal epithelium. Cytotoxic enterotoxins may interfere with protein synthesis in cells of the colonic epithelium and cause bloody, sometimes fatal dysentery. As more enterotoxins are discovered, it is becoming apparent that such variables as anatomic site and mode of action may not, in fact, be definitive criteria for classifying these substances. As a result, no universally acceptable classification scheme has yet been devised. Moreover, the biochemical and physiological characteristics of many enterotoxins and their role in gastroenteritis and other disorders remain speculative.

Endotoxins↗
PubMedDate not supplied

Life quality in the era of bridging to cardiac transplantation. Bridge patients in an outpatient setting.

This study provides an empirical evaluation of quality of life in the first two heart transplant candidates with mechanical circulatory support who were transferred (with support in place) to an outpatient setting to await transplantation. Their life quality in physical, emotional, and social domains following transfer was compared to: 1) their previous life quality while hospitalized, 2) life quality among a case series of five other candidates awaiting transplantation during the same time period, and 3) life quality among recent samples of heart recipients from our center and elsewhere. The transferred patients improved markedly in physical and emotional well being, with smaller gains in social functioning after leaving the hospital. They not only improved over their own earlier status while hospitalized, but showed life quality advantages over other hospitalized transplant candidates. Overall, they came to more closely resemble transplant recipients, rather than candidates, of similar age and indication for transplant. Outpatient care for selected mechanically supported heart transplant candidates provides an important potential option for the increasing numbers of patients requiring such support for extended time periods. The study yields critical data as fully implantable mechanical circulatory support devices for permanent heart replacement become a possibility.

Adolescent↗