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Biomedical subjects

J M Forbes

Publications and source records attributed to J M Forbes.

At least 37 records · Page 2Linked to original sources
PubMed1999

Macrophage and myofibroblast involvement in ischemic acute renal failure is attenuated by endothelin receptor antagonists.

BACKGROUND: Endothelin (ET) may be a mediator of injury following ischemia-induced acute renal failure (ARF). ET receptor (ETR) antagonists have been reported to increase survival rates and lower serum creatinines when administered postrenal ischemia-reperfusion injury in the rat. Renal cellular and extracellular matrix responses to this therapy have not been addressed. METHODS: We investigated the use of ETR antagonists, PD 156707 (ETA) and SB 209670 (ETA and ETB) in the treatment of sublethal postischemic ARF. The right kidney of female Sprague-Dawley rats weighing approximately 200 g was removed. After five days, the left renal pedicle was occluded for 45 minutes. Twenty-four hours after renal ischemia, one of two ETR antagonists, PD 156707 (N = 7) or SB 209670 (N = 8), was administered. Experimental animals were compared with an ischemic group receiving only saline (N = 9). Three nephrectomized groups that did not undergo ischemia but that received infusions of saline (N = 6), PD 156707 (N = 6), and SB 209670 (N = 6), respectively, were also studied. Animals were sacrificed one week postischemia. Quantitation of monocytes and macrophages (Mo/Mphi), alpha-smooth muscle actin-positive myofibroblasts, and collagens type III and IV was performed by immunohistochemical staining. Cell kinetics were examined by staining for apoptosis with terminal deoxyuridine triphosphate (dUTP) nick end labeling and for proliferation with proliferating cell nuclear antigen. RESULTS: All ischemic groups of rats initially developed raised serum creatinine levels; however, no significant difference was observed between the groups (Kruskal-Wallis). Creatinines returned to preischemic values in all groups by the time of sacrifice. No significant difference in kidney weights or body weights was found between groups. Histologically, infiltration of Mo/Mphi was significantly reduced in groups treated with ETR antagonists (P < 0.001). The presence of myofibroblasts was also significantly reduced in the antagonist-treated groups (P < 0. 001). This was also paralleled by reduced quantities of collagen IV in the treated rat groups (P < 0.001). The interstitial area was also significantly greater in the saline group (P < 0.001). The amount of collagen III did not significantly differ between rat groups. Apoptosis was reduced (P < 0.001) by treatment with ETR antagonists, whereas proliferation was enhanced (P < 0.005). All non-ischemic groups showed no variation in any parameter studied at this time point. CONCLUSIONS: Treatment of ischemic ARF in the rat with ETR antagonists PD 156707 and SB 209670 attenuated cellular infiltration and matrix accumulation. An advantage of one antagonist over the other could not be determined in this study. The marked discrepancy between function and pathology (former unchanged, latter markedly improved) may be due to the time frame of this experiment, and longer outcome measures need to be assessed.

Actins↗
PubMed1999

Performance and gastro-intestinal response of broiler chickens fed on cereal grain-based foods soaked in water.

1. Two experiments were carried out to investigate the addition of 1 3 kg water per kg air-dry mash diets containing high proportions (600 to 700 g/kg) of ground cereal grains (wheat, barley or oats) on broiler performance and the structure and function of the gastro-intestinal tract. 2. Chicks at the age of 7 d were fed on the wheat-, barley- or oats-based diets in the dry or wet forms for 35 d. Food and water intakes were recorded daily while body weight was measured weekly. Two birds from each treatment were killed each week to measure gut size and the viscosity of gut contents. Tissue samples from various digestive segments were histo-morphologically examined to determine the thickness of tissue layers, size of tissue glands, villa heights, crypt depths and thickness of tunica muscularis. Crypt cell proliferation rate (CCPR) for each segment was also determined using a metaphase arrest technique. 3. The results from both experiments showed that wetting food significantly (P<0.05) increased food intake, total water intake and body weight gain of broiler chickens. The body weight gains of birds were proportional to their food intakes so that the efficiency of food utilisation was similar for all treatments. Dry matter retention of food tended to increase in birds given wet food from 7 to 21 d but not thereafter, compared to the dry-fed birds. Although water intake from the water bottle was significantly (P<0.05) reduced in birds given wet food, total water intakes from the water bottle plus that from food were significantly (P<0.05) higher in the wet-fed birds than in the dry-fed birds. The ratio of total water to dry food intake was, however, similar in both feeding regimens. 4. The fresh empty weight of the gut was increased by wet-feeding while its relative weight to body weight and the length of gut was not affected by dietary treatments. Significantly greater development of the tissue glands in the proventriculus and gizzard was observed in the birds given wet food; this was associated with the reduced thickness of the muscular layer of these segments. An increase in villus height was also observed in duodenum, small intestine, caeca and colon of birds given wet food, compared to those given dry food. CCPR was significantly (P<0.05) reduced by wet-feeding throughout the digestive tract. This was associated with a significant decrease in the mean viscosity of the gut contents and the concentration of volatile fatty acids (VFAs) in the caeca. 5. Wetting diets based on cereal grains caused a significant improvement in the performance of broiler chickens. The mechanism of the beneficial effects of wet feeding could be attributed to the decreased viscosity of gut contents; the greater development of the layer of villi in the digestive segments and the reduced CCPR in the crypts of the epithelium.

Aging↗
PubMed1996

Short-term effects of food protein content on subsequent diet selection by chickens and the consequences of alternate feeding of high- and low-protein foods.

1. Growing male chickens of broiler and layer strains were allowed to eat either a high-protein food (HP) or a low-protein food (LP) for 10 min after an overnight fast and then offered a choice between HP and LP. During the next hour they ate significantly more of the food other than the initial meal. Similar results were obtained when there was a gap of 45 min without food between the initial meal and the choice period. 2. When the initial meal was given by tube into the crop, followed by 45 min without food, there was no significant effect on subsequent diet selection. These results show that it is necessary for the birds to eat the food themselves for it to exert its effect on subsequent choice. 3. Birds with experience of eating two foods identical in nutrient composition but different in colour did not select either food in preference to the other following an initial meal of one alone. This is evidence against the possibility that neophagia accounts for the results of the first two experiments. When an initial meal of low protein food was followed by a choice of high and low protein foods, birds ate a greater proportion of the high protein when it was placed on the opposite side of the cage from that in which the initial meal was given. Thus they are not choosing a food simply by its position within the cage. 4. To see the extent to which broilers can extend their ability to compensate for protein content over several weeks, male broilers were given one of 4 treatments from 5 to 10 weeks of age: (A) HP and LP concurrently; (B) HP and LP on alternate days; (C) HP in the morning and LP in the afternoon, (D) LP in the morning and HP in the afternoon. There was no significant effect of treatment on food intake, body weight gain or carcase protein content but carcases were significantly less fat after treatment (B) than treatment (D). 5. It is concluded that growing broiler chicks can compensate well for periods of access to only a low-protein food, by subsequent intake of high-protein food, and vice versa, as long as they are able to gauge the sensory properties of the foods. Offering two complementary foods in alternating half-day periods is an effective method of choice-feeding, allowing birds to select a diet to meet the requirements for growth.

Aging↗
PubMed1996

Effects of food intake, soaking time, enzyme and cornflour addition on the digestibility of the diet and performance of broilers given wet food.

1. Four experiments were carried out to investigate the effects on growth, food conversion efficiency (FCE) and apparent diet digestibility, of wetting food before offering it to individually caged growing chickens. 2. Female broiler chicks (8/treatment) were given grower food ad libitum from 28-49 d of age either in the dry form or wetted with 2.0 kg water/kg air dry food, or wet food restricted to the same daily amount of dry matter as eaten by the dry-fed birds. Ad libitum feeding of the wet food significantly increased food intake and body weight gain, compared to dry feeding, while weight gains of birds with restricted feeding of wet food were intermediate. 3. Experiments 2 and 3 studied the effects of the time interval between mixing the food with water and offering it to the birds. When pre-soaking times of 0, 12 and 24 h were compared with dry food for male broilers (8/treatment) from 25 to 40 d all wet treatments increased body weight gains significantly, the best results coming from the zero soaking time, when DM digestibility was increased significantly from 677 to 714 g/kg. When restricted amounts of food were offered hourly for 8 h on each of 4 d, DM digestibility was significantly increased from 634 for dry food to 659 for that freshly mixed with water and 664 g/kg for that soaked for 1 h between mixing and offering. 4. In a factorial experiment with wet and dry food, either in the standard form or with added enzyme or 400 g/kg cornflour, there were significant positive effects on growth and FCE of broilers (7/treatment) attributable to enzyme and wetting, while cornflour significantly reduced growth. However, wet cornflour-diluted food gave better growth than dry standard food. Wetting significantly increased the apparent digestibility of dry matter and protein while dilution with cornflour significantly reduced protein digestibility. 5. These results confirm those previously presented in terms of improved growth and FCE with wet feeding and demonstrate a large improvement in the proportion of the food absorbed from the digestive tract, of similar magnitude to the improvement in FCE. They also show that it is not necessary to pre-soak food in order to attain the maximum effect.

Animals↗
PubMed1996

Integration of regulatory signals controlling forage intake in ruminants.

Numerous factors have the potential to affect the amount of forage or pasture eaten by ruminant animals, including gut capacity, ability of tissues to metabolize nutrients, ruminal acidity, and osmolality. Much research into the control of food intake has tested one particular theory, often by applying greater degrees of stimulation than occur naturally, and is then unable to explain how physiological changes in that stimulus can be responsible for controlling intake. We have found that the effects of two or three stimuli (sodium acetate, sodium propionate, ruminal distension) applied together were additive. As to the site of this integration, receptors in the rumen wall are sensitive to both mechanical stimulation and acids, with transmission of impulses in vagal afferent fibers probably modulated by the osmolality of ruminal fluid. Thus, a certain degree of integration ("polymodal") is likely to have occurred at the level of the transceiving organ. A second level of integration is "polytopic." In this level stimulation of one visceral site modifies the effects of the same type of stimulus at another site. A third level of integration occurs in the central nervous system, whereby the effects of visceral stimulation might be balanced with signals from other stimuli (e.g., the special senses) to determine whether feeding should take place at any given moment. The thesis presented is that the central nervous system receives a nonspecific signal from the viscera; the animal might then learn to eat that amount of food that minimizes the competing discomforts of excessive abdominal visceral stimulation and shortage or imbalance of nutrients.

Animals↗
PubMed1995

Food intake and growth in chickens given food in the wet form with and without access to drinking water.

1. Individually caged growing chickens were offered a commercial grower food mixed with 1.5 to 2.25 times the weight of water and the effects, compared to giving the same food in air-dry form, on food intake, body weight gain and carcase composition were investigated. 2. Male broilers (24) were given either a grower food in the air-dry form with access to drinking water or the same food mixed with 2.0 parts of water (700 g water/kg of mixed food) with no drinking water from 28 to 49 d of age. From 49 to 63 d all birds were given dry food and drinking water and were then killed for carcase analysis. Food intake and weight gain were significantly increased during the wet-feeding period, as was carcase protein but not abdominal or carcase fat at the end of the experiment. 3. Five male broilers were given each of 5 dietary treatments containing 0 (control), 1.5, 1.75, 2.0 and 2.25 times added water (640, 673, 700 and 723 g water/kg) from 28 to 49 d. Food intakes, body weight gains and carcase weights were significantly increased for all water additions compared with dry food, but there were no significant differences between different water additions. 4. Female broiler chicks responded to wet feeding (700 g water/kg) in a similar manner to males and the dry matter approximate digestibility was increased from 0.65 for the dry food to 0.73 for the wet. 5. Cockerels of an egg-laying strain did not increase their intake of dietary dry matter when it was fed in the wet form (700 g water/kg), but there was a significant increase in body weight gain. 6. Male broilers were offered wet food (700 g water/kg) with or without access to drinking water. There was equal stimulation of food intake, growth and carcase weight with both wet-feeding treatments. 7. Providing food mixed with sufficient water to give a porridge-like consistency significantly increased weight gains in each of the five experiments and significantly improved food conversion efficiency in three of the five. It is not necessary to withhold drinking water in order to obtain this effect.

Animal Feed↗