Search PubMed⌕ Search

Biomedical subjects

C L Davis

Publications and source records attributed to C L Davis.

At least 127 records · Page 7Linked to original sources
PubMed1987

Quin's oval and other microbiota in the rumens of molasses-fed sheep.

Two rumen-cannulated wether sheep were fed a diet containing 1 kg of a liquid-molasses mixture, 80 g of soybean oil meal, and 100 g of chopped wheat straw once a day. In 6 weeks and thereafter, the microbiota adapted such that Quin's oval, a very large bacterium, was present in huge numbers (11.3 X 10(10) and 1.3 X 10(10) ml-1 after 73 days). Direct microscopic counts were also done on small bacteria, moderate-sized Selenomonas spp., and small Entodinium spp., which were the only protozoa seen. After the necessary dilution of rumen contents to make the microbial cells visible, Quin's ovals were seen to be much smaller in sheep 1 than in sheep 2. Most-probable-number estimates indicated that Methanobrevibacter spp. were present at 10(7) ml-1, Methanosarcina spp. were present at 10(3) ml-1, and Eubacterium limosum-like bacteria were present at 10(5) to 10(6) ml-1. In the adapted sheep, the dry portion of the diet was rapidly consumed, but the molasses mixture was consumed over a 9- to 10-h period. Volatile fatty acids in the rumen were present in very low amounts just prior to feeding and were much higher during the consumption of the diet, with about a 1:1 molar ratio of propionate to acetate between 1 and 9 h after feeding. Data were obtained on hourly feed consumption, levels of volatile fatty acids, and pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1987

Effect of reduction in renal artery pressure on atrial natriuretic peptide-induced natriuresis.

Studies were undertaken in anesthetized male Sprague-Dawley rats to investigate the effects of lowering renal arterial pressure within the autoregulatory range (to 85-95 mmHg) on the renal response to atriopeptin II (AP II) and atrial extract (AE). The natriuresis and diuresis produced by bolus injections of AP II at three dose levels (250-1,000 ng) was abolished or substantially reduced at lowered arterial pressure (85 mmHg). When renal artery pressure was lowered at the same time as an AE infusion was begun it completely blocked the natriuresis and diuresis. When pressure was reduced after 45 min of AE infusion the natriuresis was blunted, but not fully abolished. The effect of prior reduction in renal arterial pressure on the response to AP II (100 ng/min) and furosemide was compared; the AP II natriuresis was prevented when arterial pressure was lowered to 90 mmHg, but the natriuretic effect of furosemide was only slightly diminished. There was no significant rise in glomerular filtration rate (GFR) with AP II and no correlation between GFR changes and the Na excretory response. Reducing renal arterial pressure prior to, at the same time as, or 45 min after beginning an infusion of atrial natriuretic peptide substantially blunts or completely abolishes the natriuresis. Reductions in renal arterial pressure may block the natriuretic and diuretic effects of these compounds by interfering with their hemodynamic actions or by causing sufficient enhancement of salt reabsorption to limit delivery to terminal nephron segments.

Animals↗
PubMed1987

Effect of atrial natriuretic peptides on renal medullary solute gradients.

Studies were performed to examine the effect of the atrial natriuretic peptides on the solute gradient of the renal medulla. Experiments were performed in anesthetized male Sprague-Dawley rats given an infusion of either a purified atrial extract (n = 13), atrial natriuretic peptide 8-33 (1 microgram prime followed by 100 ng/min) (n = 8), furosemide (75 micrograms prime and 7.5 micrograms/min, n = 3), or vehicle alone (n = 17). Kidneys were removed 5 min after beginning the infusion, except in four animals, which were infused with atrial extract for 15 min before kidney removal. Both synthetic atrial peptides and an atrial extract result in rapid dissipation of the medullary gradient for urea, sodium, and total solute. No additional loss of solute was apparent at 15 min compared with 5 min. Furosemide caused equally rapid dissipation of the solute gradient at an approximately equidiuretic dose. The fall in tissue concentrations of urea and sodium was attributable to a loss of solute rather than addition of water. Administration of all three agents was associated with an increase in urinary urea excretion, which peaked earlier than the natriuresis. Urinary losses appear to account for a substantial portion of the loss of medullary solute.

Animals↗
PubMed1987

Dynamic display of the temporomandibular joint meniscus by using "fast-scan" MR imaging.

In order to display temporomandibular joint (TMJ) images as a dynamic or motion study, a protocol was developed to obtain MR images of the TMJ in multiple phases of opening by using the "fast-scanning" capabilities of the GE Signa MR scanner. To facilitate this procedure a prototype device was also developed to passively open the patient's mouth from resting (closed) to fully open in user-defined increments (minimum 1 mm). MR imaging (surface coil) was carried out at each successive station using the GRASS, pulse-sequence data base of the GE Signa system operating at 1.5 T. Image-acquisition parameters were optimized in studies of cadavers and volunteers to obtain the clearest delineation of the TMJ meniscus and to determine any potential tradeoffs between total imaging time per slice (image quality), patient tolerance, and other practical considerations. For viewing, the images were sequentially placed in the video memory of the operating console and displayed in a back-and-forth-closed cine loop or "movie" mode at variable (operator-selectable) speeds. The dynamic sequences in four individuals were compared with static open- and closed-mouth views obtained with routine pulse sequences. Any single image from the dynamic display lacked the high resolution of the routine static images because of technical limitations of the pulse-sequence data base. However, in the movie mode the pertinent joint structures (such as meniscus and condyle) were clearly delineated, as were several of the important muscles of mastication. The anterior motion (translation) of the meniscus during jaw opening is particularly evident and suggests great potential for functional evaluation. These results show the feasibility of dynamic TMJ imaging with MR. The added information of the cine display potentially complements the routine static images and may prove extremely valuable in the assessment of TMJ dysfunction.

Cartilage, Articular↗
PubMed1987

Abomasal pH, nutrient digestibility, and growth of Holstein bull calves fed acidified milk replacer.

Our objective was to compare nutrient digestion and utilization, amount and pattern of intake, and pH profile over time of abomasal contents in calves offered acidified milk replacer ad libitum or regular (sweet) milk replacer twice daily at 10% of body weight per day. Ten Holstein bull calves were fed replacers reconstituted to 13% dry matter for 4 wk. Daily milk replacer and water consumption and weekly body weight were recorded. Other variables were measured during the 2nd and 4th wk. Calves offered acidified replacer consumed more dry matter and gained more body weight than did calves fed sweet replacer; however, there was no difference in feed conversion ratio. Apparent digestibility of dry matter, ether extract, nitrogen, and retention of absorbed nitrogen were not affected by treatment. Acidified milk replacer offered ad libitum lowered the pH of abomasal contents and feces compared to regular replacer offered at 10% of body weight per day. Feeding patterns of calves offered acidified replacer ad libitum were variable. No adverse effects of feeding acidified milk replacer were noted.

Abomasum↗
PubMed1986

Identification and characterization of a fatty acid binding protein in bovine mammary gland.

A fatty acid binding protein (FABP) was isolated from bovine mammary cytosol by gel filtration and ion exchange chromatography. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate indicated a mol. wt. of 12,000. Isoelectric focusing showed two bands at pH 5.6 and 5.8. FABP bound long chain fatty acids and their CoA thioesters, but not medium or short chain fatty acids. Affinity constant (Ka) for 18:1 was about 2 micromolar. Endogenously bound fatty acids included 16:0, 18:0 and 18:1, in both covalent and noncovalent association with FABP. Activities of microsomal phosphatidic acid phosphatase, fatty acid:CoA ligase or diacylglycerol acyltransferase were not affected by purified FABP in vitro.

Animals↗
PubMed1986

Effect of source of carbohydrate and frequency of feeding on rumen parameters in dairy steers.

Four rumen-fistulated, Holstein steers (358 kg) were fed two diets at two frequencies (2 and 8 times/d) in a 4 X 4 Latin square design with 28-d periods. The two diets consisted of corn silage and a concentrate mixture in a ratio of 40:60 on a dry matter basis. The two concentrate mixtures (control and dried whole whey) contained, as a percentage: ground shelled corn, 87.85, 19.05; soybean meal, 9.4, 5.9; dicalcium phosphate, 1.7, 0; trace mineralized salt, 1.0, 1.0; vitamin A and D premix, .05, .05; and dried whole whey, 0, 74.0, respectively. Rumen fluid samples were taken at hourly intervals for 24 h and analyzed for pH, volatile fatty acids, lactate, ammonia nitrogen, and protozoal numbers. Total concentration of volatile fatty acids in the rumen were not affected by treatments. Feeding the control diet resulted in significantly higher ruminal acetate and isovalerate but lower butyrate and valerate expressed as a molar percentage. Increasing the feeding frequency from 2 to 8 times/d resulted in an increase in the molar percentage of acetate and a decrease in the concentration of lactate in ruminal fluid. Numbers of protozoa varied considerably with time after feeding and tended to be higher on the whey diet.

Ammonia↗
PubMed1986

Effect of isolation temperature on the determination of bovine plasma very low density lipoprotein concentrations.

A split-plot design was used to determine effect of temperature on isolation of plasma very low density lipoproteins that were high in either saturated or polyunsaturated fatty acids. Four steers received abomasal infusion of 400 ml of water (control) or of corn oil, which served as the whole plot treatment, and the isolation of lipoproteins by ultra-centrifugation at 4, 20 and 37 degrees C were the subplot treatments. Measured concentrations of plasma very low density lipoproteins (less than 1.007 g/ml) in control steers was 59 and 19% of that at 37 degrees C when isolation occurred at 20 and 4 degrees C, respectively. Measured concentrations of lipoproteins with densities less than 1.024 g/ml were not affected by lowering the isolation temperature from 37 to 20 degrees C but were decreased approximately 50% at 4 degrees C. Abomasal infusion of corn oil for 48 h reduced plasma very low density lipoprotein concentration from 18.3 to 5.2 mg/dl (37 degrees C isolation). Triglycerides of lipoproteins isolated from animals during the abomasal corn oil infusion had less C18:2 (average 36.3 vs. 4.0%) fatty acids than during the control treatment. Reducing the temperature of isolation did not affect measured lipoprotein concentration in plasma obtained from animals during oil infusion. Reduction in isolation temperature has a greater effect on the recovery of very low density lipoproteins, which are relatively high in saturated fatty acids compared with those high in polyunsaturated fatty acids.

Abomasum↗
PubMed1986

Malt sprouts as a source of supplemental protein for ruminants.

Nitrogen solubility, ruminal degradation, and amino acid composition of pelleted malt sprouts, pelleted corn gluten feed, and soybean meal were studied. Four rumen-cannulated steers were fed diets containing 45% pelleted malt sprouts or 45% pelleted corn gluten feed in a 2 X 2 crossover design with 15-d periods. Ruminal degradation of dry matter and nitrogen from malt sprouts or corn gluten feed was estimated by disappearance of these components from polyester bags after 1, 2, 3, 4, 6, 8, 10, 12, 16, or 24 h of in situ fermentation. For comparison, degradation of soybean meal after 2, 4, 8, or 24 h was measured. Malt sprouts had less soluble nitrogen than corn gluten feed, but available crude protein contents were similar. Malt sprouts dry matter was degraded more slowly than was corn gluten feed dry matter. Nitrogen degradation rates of the two feeds, after correction for unavailable nitrogen, did not differ. Malt sprouts had higher concentrations of arginine, lysine, and aspartate than corn gluten feed; however, corn gluten feed had higher concentrations of the other amino acids measured. Malt sprouts would be expected to provide more amino acids of feed origin to the lower gut of ruminants, provided passage rates of the supplements are similar.

Animal Feed↗
PubMed1985

Maintenance of Different Mannitol Uptake Systems during Starvation in Oxidative and Fermentative Marine Bacteria.

The mannitol uptake systems in marine Vibrio and Pseudomonas isolates from the kelp beds off the South African west coast were examined. The fermentative Vibrio isolate possessed a constitutive rapid mannitol uptake system and also a soluble mannitol-1-phosphate dehydrogenase, indicative of a mannitol phosphotransferase system. An inducible, relatively less active mannitol uptake system was detected in the oxidative Pseudomonas isolate, and this strain possessed a mannitol dehydrogenase. The maintenance of these systems during starvation survival was studied. The Vibrio isolate maintained its initial uptake system for approximately 5 weeks of starvation, after which time the uptake system was replaced by one with a higher affinity for mannitol. The mannitol transport system of the Pseudomonas isolate was depressed early in starvation (30 h) but could be readily induced by exogenous mannitol after 6 weeks of starvation. The relative proportions of mannitol which was incorporated and respired were determined in starved Vibrio and Pseudomonas strains.

Journal Article↗
PubMed1985

Response of dairy cows to sodium bicarbonate and limestone in early lactation.

A total of 108 dairy cows at three locations were fed a diet supplemented with sodium bicarbonate and limestone during the first 16 wk of lactation. Complete mixed diets were fed for ad libitum intake and consisted of concentrate and corn silage (60:40, dry matter). The four treatments were: 1) basal diet, 2) basal plus 1.2% sodium bicarbonate, 3) basal plus 1.4% limestone, and 4) basal plus 1.2% sodium bicarbonate plus 1.4% limestone. Dry matter intake was increased for 8 wk by sodium bicarbonate, then decreased from wk 9 to 16. Intake was decreased by limestone alone or in combination with sodium bicarbonate. Sodium bicarbonate increased milk production for 8 wk and 4% fat-corrected milk for 16 wk. Average dry matter intake, milk production, and 4% fat-corrected milk (kg/day) for the 16 wk were: 1) 20.2, 31.1, 27.3; 2) 19.8, 32.0, 28.7; 3) 18.9, 31.4, 27.9, and 4) 18.4, 29.7, 27.2 for diets 1 to 4. Ruminal pH was decreased, and volatile fatty acid concentration was increased by added sodium bicarbonate and appeared to result from increased feed intake. Digestibility of nutrients was unaffected by supplements. Sodium bicarbonate affected regulation of blood and urine pH and concentration of electrolytes more than limestone. Serum magnesium was reduced with sodium bicarbonate, although not beyond normal physiological reference range.

Animals↗
PubMed1984

Enumeration and presumptive identification of bacteria from the small intestine of sheep.

Microflora of the small intestine of sheep was examined. Samples of tissue and digesta were taken from four sites along the small intestine (3, 8, 13, and 18 m from the pylorus) and maintained under anaerobic conditions. The pH of the digesta taken at the 3rd, 8th, 13th, and 18th m sections were 5.44, 6.37, 7.24, and 6.79. Digesta and tissue samples were diluted serially and plated within the anaerobic glove box on complex medium containing rumen fluid. In addition, each sample was plated on the same medium and incubated aerobically. As determined by growth under anaerobic conditions, viable counts of the digesta ranged from 5 X 10(4) to 7 X 10(6) cells/g, whereas counts for the tissue ranged from 2 X 10(2) to 4 X 10(4) cells/g. Viable counts determined aerobically for the digesta ranged from 1 X 10(4) to 5 X 10(6) cells/g, whereas the counts for the tissue ranged from 5 X 10 to 6 X 10(4) cells/g. Tentative identification of 50 isolates from samples of tissue and digesta in the 13th m section revealed a predominance of streptococcal organisms and rod shaped organism morphologically similar to Propionibacterium. An indigenous population of acid-tolerant bacteria with the ability to ferment simple sugars and starch was in the small intestine.

Animals↗
PubMed1984

Effect of ruminal ammonia-nitrogen concentration on protein degradation in situ.

Two experiments were conducted to determine the effect of ruminal ammonia-nitrogen concentration on rate of ruminal protein degradation. In Experiment 1, four Holstein steers were fed a basal diet of corn grain and corn silage at hourly intervals. Continuous intraruminal infusions of solutions containing sodium bicarbonate and either sodium chloride or ammonium chloride resulted in ruminal ammonia-nitrogen concentrations that averaged 4.8 and 17.3 mg/dl. Ruminal fluid pH, fluid volume, and turnover rate of fluid and molar percentage of acetate, propionate, and butyrate were similar across treatments, reflecting steady state conditions. Rates of nitrogen and dry matter disappearance from polyester bags containing soybean protein supplements with 10.2 or 50.1% soluble nitrogen were not affected by increase of ruminal ammonia-nitrogen concentrations from 4.8 to 17.3 mg/dl. In Experiment 2, Holstein steers were fed twice daily a basal diet of urea-supplemented corn grain and corn silage. Polyester bags containing soybean protein supplements were placed in the rumen at -4, 0, or 4 h with reference to feeding and incubated from 1 to 12 h. Peak ruminal ammonia-nitrogen concentrations occurred during different periods of incubation for each treatment. Ruminal ammonia-nitrogen concentrations ranged from 3 mg/dl at 6 h postfeeding to 46 mg/dl at 1 h postfeeding. Nitrogen and dry matter disappearance rates during 0 to 1 and 1 to 12 h of incubation did not differ among treatments.

Ammonia↗
PubMed1984

Water dynamics of dairy cattle as affected by initiation of lactation and feed intake.

Effects of lactation and feed intake on sizes and half-lives of body water pools were investigated in four Holstein cows in a thermoneutral environment. Various markers were administered, on average, 24 days prepartum (Period 1, feed intake fixed to average of consumption after offered at a rate ensuring 10% refusal), 24 days postpartum (Period 2, restricted to intake in Period 1), and 42 days postpartum (Period 3, feed again offered at a rate ensuring 10% refusal). Total body water decreased from period 1 to 2; however, it did not change as a percent of body weight. Estimated body water half-lives and fluxes for the three periods were 7.5, 3.7, and 2.9 days; and 42, 66, and 87 liters/day. Increased water intake during lactation closely matched water secreted in milk. Empty body water, estimated by a two-compartment, four-parameter model, as a percent of body weight did not change across periods. Lactation and increased feed intake decreased half-life of body water. Plasma volume increased as a percent of body weight because of loss of body weight in early lactation; however, extracellular volume tended to decrease with body weight. Initiation of lactation and feed intake during lactation affect water dynamics of the dairy cow.

Animals↗
PubMed1984

Ruminal bypass of drinking water in lactating cows.

Drinking water that does not equilibrate with ruminal fluid, i.e., bypasses the rumen, was studied qualitatively and quantitatively in eight rumen-fistulated lactating Holstein cows. Decreased temperatures in the sulcus omasi and abomasum shortly after initiation of drinking indicated that water had bypassed the rumen. Recovery of a water-soluble marker, included in drinking water offered after water was withheld for 4.5 or 9 h following feeding, was used to estimate ruminal bypass. For respective treatments, 18 and 5% of drinking water was calculated to have bypassed the rumen. Ruminal bypass in lactating cows drinking relatively large amounts of water could affect comparisons of water intake with total ruminal fluid outflow as measured by dilution of a water-soluble marker. Drinking water should not be assumed to equilibrate with ruminal fluid.

Abomasum↗
PubMed1984

Plasma concentration and lipid composition of lipoproteins in lactating dairy cows fed control and high grain diets.

Six multiparous Holstein cows ranging from 7 to 19 wk postpartum were in a switchback design to determine effects of feeding high grain diets on lipoprotein concentration and composition in blood. Percents concentrate, alfalfa haylage, and corn silage of control and high grain diets were 50, 83; 25, 9; and 25, 8 dry matter. Milk yield (kg/day), milk fat percentage, and fat yield (g/day) averaged 27.7, 3.58, 997 and 30.2, 2.45, 729 for control and high grain treatments. Very low density, low density, and high density lipoproteins were isolated by gel filtration of total lipoproteins obtained by ultracentrifugation. Lipoprotein concentrations in blood plasma of cows fed the control or high grain diets were similar. Triglyceride, phospholipid, cholesterol, and cholesterol ester contents of each lipoprotein class were not altered by treatment. High grain feeding increased octadecadienoic fatty acid content of low density and high density lipoprotein cholesterol esters and decreased octadecenoic and octadecatrienoic acids. The trend was similar for the very low density lipoprotein fraction. Phospholipid octadecenoic acid decreased in all lipoprotein fractions but only significantly for high density lipoproteins. It is unlikely that differences in lipid composition of plasma lipoproteins caused alterations in lipoprotein metabolism leading to fat depression in this and other similar studies.

Animal Feed↗