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Biomedical subjects

C E Allen

Publications and source records attributed to C E Allen.

At least 55 records · Page 3Linked to original sources
PubMed1980

Metabolic responsiveness of different size adipocytes to fasting and refeeding in the pig.

The effects of fasting (F) and fasting-refeeding (FR) on [U-14C]glucose and [1-14C]palmitate metabolism were examined in pig middle subcutaneous (MSQ) adipocytes fractionated into 20--63, 63--102 and 102--153 microns diameter ranges. Fasting caused a similar decrease in de novo glyceride fatty acid (GFA) and glyceride-glycerol (GG) synthesis from glucose among adipocytes of different size. After refeeding for 2 days, glucose metabolism significantly increased in all fractions, however, the increase did not reach non-fasting levels. There was a disparate increase in glucose metabolism among adipocyte fractions after refeeding. Adipocytes 102--153 microns in diameter had a larger increase in glucose metabolism than smaller adipocytes. Fasting suppressed palmitate esterification rates in 20--63 and 63--102 microns fractions. Esterification by adipocyted 102--153 microns in diameter was not diminished after fasting. An "overshoot" in esterification by adipocytes 63--102 and 102--153 microns in diameter relative to control adipocytes was observed after refeeding; no "overshoot" occurred in 20--63 microns adipocytes. These results indicate that adipocytes of different size have markedly different capacities for substrate utilization after F or FR as well as different metabolic adaptations to F or FR.

Adipose Tissue↗
PubMed1979

Elevated levels of a calcium-activated muscle protease in rapidly atrophying muscles from vitamin E-deficient rabbits.

A Ca2+-activated proteolytic enzyme that partially degrades myofibrils was isolated from hind limb muscles of normal rabbits and rabbits undergoing rapid muscle atrophy as a result of vitamin E deficiency. Extractable Ca2+-activated protease activity was 3.6 times higher in muscle tissue from vitamin E-deficient rabbits than from muscle tissue of control rabbits. Ultrastructural studies of muscle from vitamin E-deficient rabbits showed that the Z disk was the first myofibrillar structure to show degradative changes in atrophying muscle. Myofibrils prepared from muscles from vitamin E-deficient rabbits showed partial or complete loss of Z-disk density. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the amount of troponin-T (37 000 daltons) and alpha-actinin (96 000 daltons) was reduced in myofibrils from atrophying muscle as compared to myofibrils prepared from control muscle. In vitro treatment of purified myofibrils with purified Ca2+-activated proteolytic enzyme produced alterations in myofibrillar ultrastructure that were identical to the initial alterations occurring in myofibrils from atrophying muscle (i.e. weakening and subsequent removal of Z disks). Additonally the electrophoretic banding pattern of Ca2+-activated proteolytic enzyme-treated myofibrils is very similar to that of myofibrils prepared from muscles atrophying as a result of nutritional vitamin E deficiency. The possible role of Ca2+-activated proteolytic enzyme in disassembly and degradation of the myofibril is discussed.

Animals↗
PubMed1979

Sodium nitrite and sorbic acid effects on Clostridium botulinum spore germination and total microbial growth in chicken frankfurter emulsions during temperature abuse.

Samples of (i) a control or of (ii) sodium nitrite-containing or (iii) sorbic acid-containing, mechanically deboned chicken meat frankfurter-type emulsions inoculated with Clostridium botulinum spores, or a combination of ii and iii, were temperature abuse at 27 degrees C. Spore germination and total microbial growth were followed and examined at specified times and until toxic samples were detected. The spores germinated within 3 days in both control and nitrite (20, 40 and 156 micrograms/g) treatments. Sorbic acid (0.2%) alone or in combination with nitrite (20, 40, and 156 micrograms/g) significantly (P less than 0.05) inhibited spore germinations. No significant germination was recorded until toxic samples were detected. A much longer incubation period was necessary for toxin to be formed in nitrite-sorbic acid combination treatments as contrasted with controls or nitrite and sorbic acid used individually. Total growth was not affected by the presence of nitrite, whereas sorbic acid appeared to depress it. Possible mechanisms explaining the effects of nitrite and sorbic acid on spore germination and growth are postulated.

Animals↗
PubMed1977

Cellularity of porcine adipose tissue: effects of growth and adiposity.

Adipose tissue, from two depots in pigs of three breeding groups with different propensities to fatten, was characterized in terms of weight of the adipose tissue organ, adipose cell number, and mean cell volume as determined by electronic counting of adipose cells fixed with osmium tetroxide. Perirenal and extramuscular adipose tissue growth was accompanied by progressive adipose cell enlargement along with an increase in cell number. By approximately 18-20 weeks of life, adipose tissue growth in both lean Hampshire x Yorkshire and fat Minnesota 3 x 1 pigs occurred exclusively by cellular hypertrophy. By 24 weeks of life (37 kg), hyperplasia was complete in Hormel Miniature pigs, which contained about one-third as many extramuscular adipose cells as the conventional pigs. Adiposity in the pig was due to cellular hypertrophy rather than cellular hyperplasia, since during growth, the leaner conventional pigs (30.6% extramuscular fat) contained more adipose cells than the fatter pigs (46.6% extramuscular fat). The number of adipose cells per animal or per adipose organ was directly related to the true body size (weight of fat-free carcass) of the animal. Fat Minnesota 3 x 1 pigs had fewer adipose cells than lean Hampshire x Yorkshire pigs at an equivalent live weight due to the smaller true body size of these animals. In young animals (28 and 54 kg), growth rate was positively correlated with adipose cell number. However, growth rate was unrelated to the total number of cells in the more mature animals (83 and 109 kg). Therefore a slow, normal growth rate may delay but not alter the final cell number.

Adipose Tissue↗
PubMed1977

Improved techniques for studies of adipocyte cellularity and metabolism.

Two methods are described for the study of adipose tissue cellularity and metabolism. In the first, 8 M urea was used to liberate osmium tetroxide-fixed adipocytes from the connective tissue matrix. In the smaller-sized cell ranges there was a significant reduction in apparent adipocyte number of rat, pig, and beef adipose tissue with 8 M urea treatment. This was attributed to solubilization of connective tissue debris that was counted as adipocytes in samples isolated without urea. There was no effect on the larger cell-size fractions with 8 M urea treatment. Eight molar urea had no effect on fixed adipocyte retention of radioactivity. The second method entailed the use of hydrogen peroxide to volatilize the black, osmium tetroxide-fatty acid complex of osmium tetroxide-fixed adipocytes, containing radioactivity, resulting in colorless lipid suitable for liquid scintillation counting. This latter technique permits incubation of unfixed adipose tissue slices with a radioactive substrate, followed by fixation with osmium tetroxide and subsequent separation of the adipocytes, by screening, into the desired size ranges. Adipocytes in various size fractions can then be counted, sized, and then decolorized with hydrogen peroxide in order to quantitate the amount of radioactivity within the adipocytes. There was no loss of radioactivity from the fixed cells with hydrogen peroxide treatment.

Adipose Tissue↗
PubMed1976

Cellularity of adipose tissue in meat animals.

Present information indicates that for meat animals adipocyte number is achieved most rapidly in the perirenal depot and least rapidly in the interfascicular of intramuscular depot. Adipocyte volume appears to be largest in the perirenal depot and smallest in the interfascicular and intermuscular depots. The best estimates available suggest that adipocyte hyperplasia is completed by 14 months of age in bovine animals and 5 months of age in porcine animals. However, because of certain technique limitations and the presence of many small adipocytes in very obese animals, these estimates must be considered very tentative. Studies in ovine and porcine animals indicate that early under-nutrition is not effective in reducing the number of subcutaneous and perirenal adipocytes later in life. However, the number of interfascicular adipocytes may be reduced. Several studies have demonstrated that the interfascicular adipocytes are very late developing and that adipocyte number is very important to the total quantity of intramuscular lipid.

Adipose Tissue↗