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R W Swick

Publications and source records attributed to R W Swick.

At least 19 recordsLinked to original sources
PubMed1994

Lysine-alpha-ketoglutarate reductase and saccharopine dehydrogenase are located only in the mitochondrial matrix in rat liver.

In rat liver, comparisons of marker enzyme activities (beta-hexosaminidase, lysosomes; catalase, peroxisomes; cytochrome oxidase, mitochondrial-inner membrane; monoamine oxidase, mitochondrial outer membrane; ornithine aminotransferase, mitochondrial matrix) show that lysine-alpha-ketoglutarate reductase and saccharopine dehydrogenase, the initial enzymes of saccharopine-dependent lysine degradation, are found only in the mitochondrial matrix. These results are consistent with obligatory uptake of lysine into the matrix for lysine catabolism and raise the possibility that lysine transport into the mitochondrion may control lysine degradation.

Animals↗
PubMed1991

Unmasking of GDP binding sites on hamster brown adipose tissue mitochondria and uncoupling protein.

1. A rapid unmasking of GDP binding sites on brown adipose tissue (BAT) mitochondria was observed when hamsters acclimatized to 28 degrees C were exposed to a temperature of 4 degrees C for 2 hr. 2. No rapid unmasking of GDP binding sites was observed when hamsters housed at 22 degrees C were briefly exposed to 4 degrees C. 3. The amount of GDP bound to BAT mitochondria from hamsters increased during 2 weeks of exposure to 4 degrees C, but did not change between 2 weeks and 30 days of cold exposure. 4. Incubation of mitochondria with 10 mM Mg2+ prior to the GDP binding assay increased the subsequent GDP binding to BAT mitochondria from hamsters housed at 28, 22 or 4 degrees C, albeit to different degrees. 5. The amount of GDP bound to uncoupling proteins isolated from untreated and Mg(2+)-treated mitochondria of hamsters and rats was measured. Scatchard analyses of the binding of GDP to purified uncoupling protein indicate that increases in the number of binding sites due to Mg2+ treatment of mitochondria do not change the affinity of the protein for GDP.

Adipose Tissue, Brown↗
PubMed1988

Changes in GDP binding to brown adipose tissue mitochondria and the uncoupling protein.

Incubation in vitro of brown adipose tissue (BAT) mitochondria with divalent cations, spermine, or alkaline phosphatase led to a marked increase in the binding of [3H]GDP. The effect of Mg2+ appeared to be the most specific and led to the largest increase in GDP binding. A simplified method was developed for measuring GDP binding to purified uncoupling protein from rat BAT mitochondria. Application of this method indicates that uncoupling protein from cold-acclimated rats binds twice as much GDP as uncoupling protein from cold-acclimated rats that were briefly returned to thermoneutrality, paralleling changes in GDP binding to the mitochondria. Incubation of BAT mitochondria with Mg2+ led to a smaller increase in GDP binding to the subsequently purified uncoupling protein, suggesting that divalent cations may somehow participate in the regulation of the activity of the uncoupling protein.

Acclimatization↗
PubMed1987

Immunochemical detection and quantitation of brown adipose tissue uncoupling protein.

A polyclonal antisera against rat brown adipose tissue mitochondrial uncoupling protein was used to examine mitochondrial samples from liver and white and brown adipose tissue from several mammalian species. A sodium dodecyl sulfate--polyacrylamide gel electrophoretic separation of proteins combined with an immunochemical method allowed for visualization of antigen--antibody complexes on nitrocellulose blots. Hamster, cavy, monkey, and mouse brown adipose tissue mitochondrial samples cross-reacted with the antisera. Mitochondria prepared from white fat obtained from young swine and sheep contained two closely migrating, antigenically active proteins. Hepatic mitochondria samples did not contain antigenically active protein. Reflectance densitometry was used for quantitation of the uncoupling protein in various mitochondrial samples. In rats fed diets low in protein, there appears to be a dissociation between the concentration of uncoupling protein and the number of nucleotide binding sites as given by the [3H]GDP binding assay. These results are indicative of a physiological activation of the uncoupling protein.

Adipose Tissue, Brown↗
PubMed1986

Evidence for unmasking of rat brown-adipose-tissue mitochondrial GDP-binding sites in response to acute cold exposure. Effects of washing with albumin on GDP binding.

Rats, previously acclimated to 29 degrees C, were moved into the cold (4 degrees C) for 2 h. Scatchard analysis of GDP binding to the brown-adipose-tissue mitochondria of these animals showed a 2.3-fold increase in the number of high-affinity sites and a 1.5-fold increase in the number of low-affinity sites compared with binding in animals maintained at 29 degrees C. Immunochemical determination showed no increase in the amount of mitochondrial uncoupling protein during this period. This strongly suggests an unmasking of existing GDP-binding sites before a detectable increase in synthesis of uncoupling protein can occur. Washing with albumin increased the number of GDP-binding sites of brown-adipose-tissue mitochondria from both warm-housed and cold-exposed animals to the same extent. This indicates that the effects of washing with albumin and cold exposure are independent and additive.

Adipose Tissue, Brown↗
PubMed1986

Bone chemistry and prehistoric diet: strontium studies of laboratory rats.

Strontium analysis of prehistoric human bone for the reconstruction of past diets is a relatively new technique in anthropology. In order to evaluate certain assumptions of the method, diets with low and high levels of strontium were fed to male, virgin female, and pregnant female laboratory rats. Analysis of the femurs of these rats by inductively coupled plasma/atomic emission spectrometry indicates that dietary intake is directly reflected in levels of strontium in bone ash. When dietary strontium levels were low, the observed ratio for bone:diet in the laboratory rats averaged 0.26, a value similar to that observed by other investigators. Among the groups fed high levels of strontium, pregnant females accumulated the most and virgin females accumulated the least strontium in bone. Males were intermediate. Gender differences in bone strontium among prehistoric human populations are considered in these terms.

Animals↗
PubMed1986

Rapid changes in number of GDP binding sites on brown adipose tissue mitochondria.

GDP binding to brown adipose tissue (BAT) mitochondria increased more than twofold in 20 min when rats were moved from 27 to 4 degrees C. When animals housed at 4 degrees C for 2 h were returned to 27 degrees C, GDP binding decreased sharply in 20 min and returned to control levels in 2 h. These results are consistent with a rapid unmasking and remasking of GDP binding sites. GDP binding to mitochondria from warm and acutely cold treated rats was not modified by prior swelling, by freeze-thawing, nor by sonication of the mitochondria before assay. GDP-inhibitable proton conductance, as measured by passive swelling, was unaffected by this brief exposure to cold but more than doubled in rats kept at 4 degrees C for 10 days. We hypothesize that the rate of GDP-inhibitable swelling may be a reflection of uncoupling protein concentration in the BAT mitochondria, whereas physiological thermogenic activity is more appropriately indicated by GDP binding. The alterations in binding activity appear not to be due to changes in the mitochondrial membrane integrity.

Adipose Tissue, Brown↗
PubMed1986

Enhanced thermogenic response to a diet low but adequate in protein persists in older rats.

Feeding a 5% lactalbumin diet to rats for 3 wk compared with a 15% lactalbumin diet resulted in lower feed efficiency and stimulated brown adipose tissue activity as measured by GDP binding. This occurred in 4-mo-old rats as well as in 7-mo-old rats. Furthermore the effects persisted after 3.5 mo of dietary treatment. An investigation of pattern of food intake revealed that no obvious alteration in pattern was involved in the lower feed efficiency associated with rats fed a 5% lactalbumin diet.

Adipose Tissue, Brown↗
PubMed1986

Norepinephrine stimulates activity of brown adipose tissue in rhesus monkeys.

Brown adipose tissue biopsies were obtained from the axillary region of adult rhesus monkeys before and after a 30-min infusion of norepinephrine or vehicle. Binding of guanosine diphosphate (GDP) to brown adipose tissue mitochondria increased an average of 186 percent in response to norepinephrine, while vehicle infusion resulted in an average decrease of 35 percent. The results are consistent with unmasking and remasking of GDP binding sites and indicative of functional brown adipose tissue in adult primates.

Adipose Tissue, Brown↗
PubMed1985

Brown adipose tissue from fetal rhesus monkey (Macaca mulatta): morphological and biochemical aspects.

Brown adipose tissue (BAT) from fetal rhesus monkeys microscopically resembled adult rodent BAT containing multiocular fat cells with numerous mitochondria. Mitochondrial carnitine palmitoyl transferase activity was lower than that in adult rodents and adenine nucleotide translocase activity was similar to that reported for rats. Rhesus monkey BAT mitochondria (BATM) possess an uncoupling protein that is characteristic of BAT as evidenced by the binding of [3H]GDP, the inhibition by GDP of the high Cl- permeability or rapid alpha-glycerol-3-phosphate oxidation. Electrophoretic analysis of BATM showed the presence of a 32,000 mol.wt protein which was enriched by procedures established for the isolation of BATM uncoupling protein.

Adipose Tissue, Brown↗
PubMed1985

Growth and protein turnover in the skeletal muscles of broiler chicks.

Growth and protein turnover were examined in the breast (pectoralis thoracica) and the leg (gastrocnemius-peroneus) muscles of broiler chicks at 1, 2, 4, and 6 weeks posthatching. The fractional rate of protein synthesis (ks) was measured by an isotope emulsion method. The fractional degradation rate (kd) was calculated from the difference in ks and fractional deposition rate (kg), which was estimated from regression equations of muscle size and protein content on body weights. The growth rate (%/day) of skeletal muscle exceeded that of the whole body. Muscle growth involved an increase in the total deoxyribonucleic acid (DNA) and the DNA-unit size and a subsequent decrease in the concentrations of nucleic acids without alteration in the ribonucleic acid (RNA):DNA ratio and RNA and DNA activity. The ks in breast muscle protein fell markedly from 48 to 16%/day between 1 and 6 weeks posthatching, whereas in leg muscle, ks underwent a more gradual decrease; from 36 to 17%/day during the same period. These changes resulted mainly from the reduction of DNA and RNA concentrations with age. The kd decreased only slightly between 1 and 2 weeks in the both muscle groups. The kg also showed a developmental fall from 33 to 4%/day and from 21 to 4%/day in the breast and leg muscles, respectively, during the 5-week period.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1985

Characteristics of growth and protein turnover in skeletal muscle of turkey poults.

Protein turnover and DNA and RNA levels were measured in the breast (pectoralis thoracica) and leg (gastrocnemius-peroneus) muscles of large white (Nicholas strain) turkey poults from 1 to 8 weeks of age to investigate their cellular growth and to evaluate the influence of protein turnover on muscle growth. Fractional rates of protein deposition (kg) were determined from regression equations of muscle size and protein content on body weights. Protein synthesis rates (ks) were measured by an isotope emulsion technique. Protein degradation rates (kd) were estimated by the difference between ks and kg. Muscle growth involved increases in total deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), an increase in the DNA-unit size, and decreases in concentrations of the nucleic acids without changes in the RNA:DNA ratio or RNA and DNA activity. The muscles showed developmental changes in ks from 56 to 10%/day and from 38 to 13%/day in breast and leg, respectively, over the 7-week period. The fractional degradation rate also fell from 22 to 7%/day in the breast muscle and from 21 to 10%/day in the leg muscle. The disproportionate decline of ks and kd resulted in an age-associated fall in kg from 34 to 4%/day and from 18 to 3%/day in the breast and the leg muscles, respectively. The efficiency of protein deposition decreased from 61 to 35% in breast muscle and 46 to 20% in leg muscle. The results were qualitatively similar to those obtained in a study with broiler chicks.

Aging↗
PubMed1984

Characteristics of growth and protein synthesis in skeletal muscles of normal and dystrophic chickens.

Several characteristics of cellular growth and protein synthesis were measured in vivo in the breast and leg muscles of normal (line 454) and hereditary muscular dystrophic (line 455) New Hampshire chickens at different ages. Fractional rates of protein synthesis (ks) were calculated from the rate of incorporation of labeled tyrosine administered continuously via a subcutaneous injection of an emulsion of L-[U-14C]tyrosine in sesame oil. Only the breast muscle showed signs of gross hypertrophy. The hypertrophy involved an abnormally rapid accumulation of protein, DNA and RNA. In dystrophic chickens, ks was at least 170% of the normal rates at 2, 5 and 52 weeks. The elevated ks was presumably a reflection of the higher DNA and RNA concentrations relative to those in normal birds. Because the RNA/DNA ratio and the activities of RNA and DNA were similar to values observed in normal birds, there may be no defect in the synthesis machinery per se.

Animals↗
PubMed1984

Protein degradation: an important consideration.

The growth rates of chicks can be varied by dietary manipulations. The rates of synthesis of protein in selected muscles can be measured by using radioactive amino acids. Measurements are made of expired air, plasma, and muscle tissues. Synthesis rates are most rapid in the young chick and turkey. As the bird ages, synthesis rates and degradation rates decrease; but these two parameters gradually come together so that the net gain in protein is zero. Synthesis rates remain fairly similar in chicks fed a complete diet or a diet lacking in lysine. This is true even if the growth rate is extremely low. However, the degradation rates are extremely high in the deficient birds so that the gain in protein deposition is very low. When the energy is restricted, growth is reduced dramatically, but synthesis rates are reduced only a small amount. Again, degradation rates are extremely high. Chickens with muscular dystrophy exhibit very high synthesis rates in breast muscle. The leg muscle changes compare with a normal bird. There are also high degradation rates in the breast muscle throughout so that the growth rate of the muscle was only greater during the early stages of growth. Additional work needs to be conducted to develop a reliable accurate chemical method for determining the degradation rates. It is apparent that the emphasis in research to increase the rapidity of growth should center on the degradation rates rather than on increasing synthesis rates.

Amino Acids↗
PubMed1983

The effect of dietary protein levels on diet-induced thermogenesis in the rat.

Relative to rats fed a 15% protein-diet, 300-g rats fed a 5% protein-diet for 5 weeks consumed 19% more food but gained only 28% as much weight, showed twice the thermic response when fed, had twice as much subscapular brown adipose tissue with almost twice the specific GDP-binding activity. There was no difference between these groups in skeletal growth nor, unexpectedly, in the proportion of carcass fat.

Adipose Tissue↗
PubMed1981

Protein degradation in primary monolayer cultures of adult rat hepatocytes. Further evidence for the regulation of protein degradation by amino acids.

Intracellular protein degradation was measured in primary monolayer cultures of adult rat hepatocytes by the loss of radioactivity from proteins pulse-labeled in culture with L-[U-14C]valine. The fractional rate of protein degradation of total protein measured over 18 h was similar to the rate in vivo. The fraction rate of protein breakdown was altered significantly by varying the composition of the chase medium from a balanced salts medium (high rate of protein degradation) to a more complete medium (lower rate of protein degradation). Whereas the vitamin component of the complete medium had some effect, the major portion of the inhibition of protein degradation was due to the essential amino acids in the medium. This inhibition was found to depend on the presence of methonine, phenylalanine, and tryptophan, the latter two of which appear to be primarily responsible. The observed rate of protein breakdown was a function of the level of amino acids in the medium when they were varied in the physiological range for rat plasma. Our results suggest that the regulation of protein degradation by essential amino acids may be physiologically important in maintaining intracellular amino acid pools when the exogenous supply of amino acids is diminished.

Amino Acids↗
PubMed1981

The effect of protein depletion and repletion on muscle-protein turnover in the chick.

Rates of growth and protein turnover in the breast muscle of young chicks were measured in order to assess the roles of protein synthesis and degradation in the regulation of muscle mass. Rates of protein synthesis were measured in vivo by injecting a massive dose of L-[1-14C]valine, and rates of protein degradation were estimated as the difference between the synthesis rate and the growth rate of muscle protein. In chicks fed on a control diet for up to 7 weeks of age, the fractional rate of synthesis decreased from 1 to 2 weeks of age and then changed insignificantly from 2 to 7 weeks of age, whereas DNA activity was constant for 1 to 7 weeks. When 4-week-old chicks were fed on a protein-free diet for 17 days, the total amount of breast-muscle protein synthesized and degraded per day and the amount of protein synthesized per unit of DNA decreased. Protein was lost owing to a greater decrease in the rate of protein synthesis, as a result of the loss of RNA and a lowered RNA activity. When depleted chicks were re-fed the control diet, rapid growth was achieved by a doubling of the fractional synthesis rate by 2 days. Initially, this was a result of increased RNA activity; by 5 days, the RNA/DNA ratio also increased. There was no evidence of a decrease in the fractional degradation rate during re-feeding. These results indicate that dietary-protein depletion and repletion cause changes in breast-muscle protein mass primarily through changes in the rate of protein synthesis.

Aging↗