PubMed Health⌕ Search

Biomedical subjects

R Clarenburg

Publications and source records attributed to R Clarenburg.

15 recordsLinked to original sources
PubMed1997

The use of urea dilution for estimation of carcass composition of Holstein steers at 3, 6, 9, and 12 months of age.

Every 3 mo for a 2-yr period, two weaned Holstein steer calves (94.5 kg) were randomly assigned to each of four slaughter age groups (3, 6, 9, and 12 mo). Urea dilution was performed before slaughter, and urea space (US) was calculated as total volume and as a percentage of body weight (BW) and empty body weight (EBW). The relationships between US (kg, % EBW and % BW), BW, and EBW and carcass soft tissue composition (protein, fat, moisture, and ash) were studied. One- and two-pool models were fitted using the urea dilution data and the coefficients of those equations (zero time, A + B), and the intercepts of compartments A and B were used to estimate body volume. Body weight and EBW effectively predicted the amount of water, fat, and protein in the carcass soft tissue. Equations expressed in kilograms were more accurate than those expressed as percentages. Urea space overestimated body water, probably because of the fast rate of urea disappearance in plasma. Correlation coefficients between US and carcass soft tissue water (kg) based on the pooled data ranged from .74 at 6 min to .48 at 42 min after infusion. The biexponential models coefficients explained more of the variation of carcass soft tissue composition than US; correlation coefficients using volume B and the soft tissue composition (in kg) with pooled data were .78 (water), .68 (fat), .69 (ash), and .76 (protein). The relationships between A and soft tissue composition were weaker (water .59, fat .51, ash .58 and protein .59). The highest correlation coefficients were obtained when A + B was used for water, fat, ash, and protein (.83, .70, .74 and .81, respectively). Equations combining BW, EBW, and two-model coefficients (A, B, A + B) explained much of the variation of soft tissue composition. No significant benefit was found in using the urea space at various times after infusion over BW or EBW alone to estimate carcass soft tissue composition in Holstein steers.

Aging↗
PubMed1983

Asialoglycoprotein receptor is uninvolved in clearing intact glycoproteins from rat blood.

The hypothesis that the hepatic receptor for asialoglycoproteins would mediate turnover of glycoproteins in blood (after their desialylation by neuraminidase located on cell surfaces) was tested in rats by measuring clearance of intact 125I-labeled glycoproteins in the presence or absence of enough unlabeled asialoglycoproteins to saturate the asialoglycoprotein receptor. Via an indwelling venous catheter, a mixture of 125I-orosomucoid (obtained from rat serum) and a bolus of unlabeled asialofetuin (bovine) was injected, and infusion of an asialofetuin solution sustained. Total radioactivity and trichloroacetic acid-precipitable radioactivity were measured in blood samples taken at frequent intervals from an arterial catheter. Clearance was computer analyzed by using a two-component model. Nondestructiveness of radiolabeling and desialylation methods and interchangeability of rat and bovine (asialo)glycoproteins were demonstrated in control experiments. The infusion trials showed that independent clearance processes exist for intact and asialoglycoproteins. Apparently, the asialoglycoprotein receptor has no function in the turnover of intact plasma glycoproteins.

Animals↗
PubMed1975

A model for ultracentrifugal quantification of (35-S) bromosulphthalein-binding to plasma proteins in the presence of radioimpurities.

Sloutions of (35S)bromosulphthalein ((35S)BSP) in heparinized canine plasma, in the proportions established in vivo after injecting BSP intravenously to test liver function, were ultracentrifugated at 226,000 g for 24 hr at 5 degrees. Protein-free supernatant was replaced by Krebs-Ringer buffer (pH 7.40), the protein sediment resuspended, and the mixture recentrifugated. That process was repeated several times, and the radio-activity of each resulting supernatant was measured. Since (35-S)BSP could not be adequately purified, supernatant radioactivities reflected both (35-S)BSP and radioimpurity. Therfore, a model was derived that (i) interpreted the rapid decrease in supernatant radioactivities of initial centrifugations and the gradual fall therafter; and (ii) allowed us to determine picomoles of non-protein-bound (35-S)BSP. Results indicated that only 0.053% (SD .0013%) of BSP in our system was not protein-bound.

Animals↗
PubMed1966

Origin of milk cholesterol in the rat: dietary versus endogenous sources.

Slices of mammary gland from lactating rats, incubated with acetate-1-(14)C or mevalonate-2-(14)C, synthesized cholesterol-(14)C. Within 2 min of an intravenous injection of 1 ml of a suspension of chylomicrons containing cholesterol-4-(14)C, mammary glands of lactating rats removed as much as 29% of the labeled cholesterol; those of 2-day-postlactating rats removed none. Rats were fed a diet containing 0.05% cholesterol-4-(14)C from 7 days prepartum to 20 days postpartum. At isotopic equilibrium, the relative specific activities of milk and dietary cholesterol indicated a dietary origin for 11% of the milk cholesterol. The extent to which endogenous sources-liver and mammary gland-contributed cholesterol to milk proved entirely dependent on whether dietary cholesterol, in the form of chyle lipo-proteins, was first processed by liver or taken up directly by mammary gland. Lack of information regarding the extent to which chyle cholesterol is removed from blood under physiological conditions by mammary gland and other tissues precludes precise assessment of the endogenous contributions to milk cholesterol and, moreover, casts doubt on the quantitative interpretability of cholesterol-(14)C-feeding experiments reported in the literature.

Animals↗
PubMedDate not supplied

Pharmacokinetics of intravenously injected chloramphenicol in baby pigs.

A sensitive fluorometric assay procedure for chloramphenicol and its metabolites was used to measure distribution in tissues and elimination of the drug after injection of 22 mg/kg iv in baby pigs. Disappearance of chloramphenicol from plasma was biphasic; an initial component was rapid (half-life about 9 min) and a second component had a half-life of 55 min. The total chloramphenicol levels in tissues and body fluids had half-life periods of 1-1.5 hr and dropped below limits of detectability within 9 hr after injection. About 80% of the injected dose was recovered from urine collected over the first 6 hr, and none thereafter. Fecal elimination, if occurring, was negligible.

Animals↗