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Biomedical subjects

R B Young

Publications and source records attributed to R B Young.

At least 19 recordsLinked to original sources
PubMed1994

Growth and development of bovine fetuses and neonates representing three genotypes.

Growth was examined in bovine fetuses and neonates that typically differ in mature size and postnatal developmental pattern. Pregnancies were established from matings expected to produce early (E), late (L), and intermediate (I) maturing postnatal growth patterns. Tissues were collected at 100 and 200 d of gestation and 30 d postnatal. Muscle:body weight ratios were lower at 100 and 200 d for the E maturity type than for the L maturity type (P < .05). This differs from observations of muscle:body weight ratios made at 30 d postnatal, at which time ratios for E were either greater than (triceps brachii, P < .05) or similar to those for L. Few differences due to maturity type were observed at 100 d for bone weight:body weight ratios; however, at 200 d of gestation E bone weight:body weight ratios were generally lower (P < .05) than those for L. The genotypic relationship for bone weight:body weight ratio at 30 d postnatal was similar to that observed at 200 d of gestation. Observations of organ weight:body weight ratios revealed no clear patterns due to maturity type. The genotypic relationship for total muscle DNA content was similar to that observed for muscle weight. These results indicate that fetal muscle development differs in cattle that have different postnatal growth patterns by as early as 100 d of gestation and that differences in fetal muscle growth are related to differences in muscle hyperplasia.

Animals↗
PubMed1990

Protein metabolism in chicken muscle cell cultures treated with cimaterol.

Primary muscle cell cultures were prepared from the leg muscle of 12-d broiler chicken embryos. The partitioning agent cimaterol (10(-6) to 10(-10) M) was added on d 1 and each day thereafter, and cells were studied after 7 d in culture. Cimaterol had no effect at any level either on the percentage of nuclei within multinucleated myotubes or on the total number of nuclei within myotubes. At 10(-7) M cimaterol, the quantity of the myofibrillar protein fraction was increased by 25.1 +/- 8.0% (P less than .05) and the quantity of myosin heavy chain was increased by 30.9 +/- 4.5% (P less than .05). To understand the basis for the increase in myofibrillar protein, the incorporation rate of [3H]Leu was measured in pulse labeling experiments. The apparent synthesis rate of the soluble protein fraction and the crude myofibrillar fraction was not significantly increased by cimaterol; however, cimaterol levels greater than 10(-8) M caused a 10 to 12% increase (P less than .05) in the incorporation rate of [3H]Leu into myosin heavy chain. The effect of cimaterol on release of [3H]Leu from prelabeled protein also was assessed in pulse-chase experiments; the apparent rate of protein degradation was inhibited by 10 to 15% (P less than .05) at the higher levels of cimaterol. Dot blot analysis indicated that the quantity of myosin heavy chain mRNA was elevated in cimaterol-treated cultures. Thus, the increased quantity of myofibrillar proteins in embryonic broiler muscle cell cultures is the combined result of a stimulation in the rate of protein synthesis and an inhibition in the rate of protein degradation.

Adrenergic beta-Agonists↗
PubMed1987

Effect of insulin on phosphorus metabolism in red blood cells from patients with schizophrenia and psychotic depressions.

In an exploratory study of the metabolism of selected intermediates of glycolysis in rbc of patients with schizophrenia and with major depressive disorders, statistically significant decreases in the RSA of 2,3-DPG were found in the rbc of patients with psychotic disorders compared to normal subjects. No statistically significant differences were observed in the RSA of any of the other glycolytic intermediates studied comparing patients to normal subjects.

Adult↗
PubMed1987

Genomic clones encoding chicken myosin heavy-chain genes.

A chicken genomic library was screened with a cDNA probe containing the 3' coding and noncoding portions of quail fast-twitch skeletal muscle myosin heavy chain (MHC). This probe hybridized to seven to nine bands on Southern blots of chicken genomic DNA, and 17 clones that hybridized to this probe were obtained from the genomic library. Partial restriction maps were constructed and probable orientation of transcription was determined for each of the 17 clones. These maps indicate the presence of at least 14 unique MHC genes or pseudogenes. Dot-blot hybridization analysis using DNA complementary to RNA from a variety of chicken tissues demonstrated that these genes are all related to the gene for sarcomeric MHC, and permitted tentative assignment of the tissue of expression for several of the MHC isoforms. To substantiate further the dot-blot data, a subclone of one of the genes (4b1), which showed significant homology with adult breast muscle RNA but which also showed weaker hybridization to RNA from other tissues, was sequenced. The sequence data verified that the clone contains a portion of a MHC gene, that it contains both 3' coding and noncoding regions, and that its predicted amino acid sequence is identical (with 96% nucleotide homology) to that of the 75-bp quail fast MHC cDNA clone published by Hastings and Emerson (1982). Thus, clone 4b1 contains a portion of one of the genes that is expressed in adult chicken breast skeletal muscle tissue.

Amino Acid Sequence↗
PubMed1987

Screening of a bovine genomic library for myosin heavy-chain genes.

Restriction enzyme digests of bovine genomic DNA were hybridized against a .37-kilobase (kb) quail embryonic myosin heavy-chain (MHC) copy deoxyribonucleic acid (cDNA) probe; containing both translated and nontranslated regions surrounding the 3' end of the gene. These experiments revealed seven to eight different bands of hybridization, indicative of multiple genes of MHC in the bovine genome. Additionally, a bovine genomic recombinant DNA library was screened with the .37-kb probe. Of the 10(6) phage screened, 11 clones containing portions of the MHC genome were identified, and four were selected for further analyses. Characterization of these four clones was carried out by constructing partial restriction enzyme maps of the inserts using six restriction enzymes singly or in combination. Orientation of the inserts with respect to the arms of the vector and with respect to direction of transcription was determined by hybridizing the DNA fragments against either the .37-kb Pst 1 fragment of pcC128 or to the .23-kb Pst I fragment of pcC128. The .23-kb fragment is located upstream from the .37-kg fragment and contains only coding sequence. Therefore, the differential hybridization pattern of these two probes provided a means for determining the probable direction of transcription. These data provide evidence for a myosin multigene family in cattle, as well as illustrating that the organization of these genes around the 3' end is unique for each of the genes analyzed.

Animals↗
PubMed1986

Premature adrenarche. Clinical and diagnostic features.

Premature adrenarche (PA) or isolated growth of sexual hair in young children, is a benign condition that may initially be confused with true precocious puberty or pathologic virilizing disorders. The clinical findings, family history, and serum concentrations of dehydroepiandrosterone sulfate (DHEA-S) were compared in 24 children with PA (79% black females) seen in a 2-year period and in an age-matched control group of 17 black females. Twenty three of 24 patients, but none of the controls, had an adult-type axillary odor. There was a positive family history of PA in only three of 24 children with PA, and in one of 17 controls. The mean serum DHEA-S was significantly higher in the PA children than in the controls, but there was a broad range of concentrations (10-143 micrograms/dl), with values in 10 of 24 cases falling within the control range for age. We conclude that: (1) PA is a relatively common finding in black females between ages 3 and 8, (2) an axillary odor is almost always present in children with PA, and (3) determination of serum DHEA-S may be of some help in confirming the clinical impression of a modest increase in adrenal androgen secretion and in ruling out a more serious disorder. In most cases, however, the diagnosis of PA can be made on the basis of the history, physical examination, and lack of rapid progression over time; the use of laboratory tests to rule out a pathologic virilizing process may best be reserved for those children with very early onset, increased linear growth, or other signs of virilization.

Adrenal Glands↗
PubMed1986

Structural analysis of myosin genes using recombinant DNA techniques.

Myosin, the major protein of the myofibril, consists of two heavy chains with a molecular weight (MW) of 200,000, complexed with four light chains of MW 17,000 to 21,000. Both the heavy and light chains exhibit polymorphisms that are tissue-specific and developmental stage-specific. Myosin heavy chains and light chains appear to be represented in the genome as multigene families in various species, including chickens, cattle, humans, rats, rabbits and nematodes. Myosin heavy-chain proteins have a high amino acid sequence homology among isoforms, and the genes for each isoform likewise exhibit a high degree of nucleotide sequence conservation. The myosin heavy-chain genes have a complex structure and contain up to 65% intervening sequence composed of up to 20 or more individual introns. Partial sequence data, transcriptional orientation and tissue of expression have been determined for several myosin heavy-chain genes. The use of recombinant DNA and associated techniques will eventually yield definitive information on the control of expression of each individual gene, as well as factors that regulate expression of closely related isoforms.

Animals↗
PubMed1985

Calcium and phosphate metabolism in children with idiopathic hypoparathyroidism or pseudohypoparathyroidism: effects of 1,25-dihydroxyvitamin D3.

Two children with congenital hypoparathyroidism and two children with pseudohypoparathyroidism were given maintenance doses of 15 to 45 ng/kg/day 1,25-dihydroxyvitamin D3 for a total of 255 months. The urinary calcium excretion showed an upward elevation after the first 2 years of treatment but was not significantly higher than that in 10 normal control subjects. The renal threshold for phosphate excretion stayed within the normal ranges compared with control values. Two hypercalcemic and two hypocalcemic episodes occurred during this period of treatment. Hypercalcemia was reversed within 1 week after withdrawal of 1,25-dihydroxyvitamin D3. Hypocalcemia was countered by increasing the dose of 1,25-dihydroxyvitamin D3. Renal functions were not adversely affected, as estimated by creatinine clearance and reciprocals of serum creatinine concentrations. The mean serum calcium concentration during 1,25-dihydroxyvitamin D3 treatment was significantly higher (P = 0.001) compared with that obtained during vitamin D2 treatment at a dose of 500 to 3000 IU/kg/day. These data provide additional support for the long-term use of 1,25-dihydroxyvitamin D3 in idiopathic hypoparathyroidism and pseudohypoparathyroidism.

Calcitriol↗
PubMed1984

Effect of creatine on contents of myosin heavy chain and myosin-heavy-chain mRNA in steady-state chicken muscle-cell cultures.

Embryonic-chick muscle cells reach a steady state with respect to protein metabolism after approx. 1 week in cell culture. To determine if this steady state could be altered by the administration of agents that have been reported to stimulate myosin heavy-chain synthesis, 7-day muscle-cell cultures were treated with 0-1 mM-creatine. Incorporation of [3H]leucine into myosin heavy chain was stimulated by 30-40% at the optimum creatine concentration (0.2 mM), but this stimulation was blocked when actinomycin D (10 micrograms/ml) was also present. However, the quantity of myosin-heavy-chain mRNA as measured by hybridization in vitro was only 15% higher in creatine-treated cultures, and was therefore not entirely responsible for the observed effect. It is important to note that creatine only exerted its action on myosin-heavy-chain synthesis rate in steady-state cultures; creatine was ineffective in altering this rate in rapidly differentiating 3-day muscle cultures. Finally, muscle-cell cultures that had been grown for the entire 7-day culture period in the presence of 0.2 mM-creatine were assayed for quantity of myosin heavy chain. Control and creatine-treated cultures contained 12.7 +/- 1.5 and 20.5 +/- 1.8 micrograms/dish respectively. In conclusion, creatine apparently enhances the quantity of myosin heavy chain in steady-state embryonic muscle-cell cultures, but it probably does not mediate regulation of myosin content in adult skeletal muscle.

Animals↗
PubMed1984

Leucine pools in normal and dystrophic chicken skeletal muscle cells in culture.

The specific radioactivity of [3H]Leu in the extracellular, intracellular, and Leu-tRNA pools of normal (white leghorn) and dystrophic (line 307) embryonic chick breast muscle cultures was analyzed as a function of equilibration time and extracellular Leu concentration (0.05-5 mM). The primary results were the following 1) [3H]Leu equilibrated to a constant specific radioactivity in the intracellular and Leu-tRNA pools within 2 min after addition to both normal and dystrophic cultures. 2) After equilibration, the extracellular [3H] Leu specific radioactivity in dystrophic cell culture medium was lower than that of medium exposed to normal cells (especially at low Leu concentrations), probably because of increased release of unlabeled Leu from the dystrophic cells as a result of faster protein breakdown. Accordingly, the specific radioactivities in the intracellular and the Leu-tRNA pools were also lower in dystrophic cells. 3) At 5 mM extracellular Leu, the specific radioactivity in the Leu-tRNA pool was approximately 40% lower than the specific radioactivity in the intracellular pool in both normal and dystrophic cells. Thus, high concentrations of extracellular Leu cannot be used to "flood out" reutilization of unlabeled Leu (released by protein degradation) during protein synthesis. 4) At 5.0 mM extracellular Leu, the specific radioactivity of [3H]Leu in the intracellular pool was comparable to that in the extracellular pool in normal and dystrophic cells; however, the specific radioactivity of Leu-tRNA (i.e. the immediate precursor to protein synthesis) was only 55-65% of the extracellular specific radioactivity in normal and dystrophic cells. In conclusion, reutilization of Leu from protein degradation is higher in dystrophic muscle cell cultures than in normal muscle cell cultures, and accurate rates of protein synthesis in cell cultures can only be obtained if specific radioactivity of amino acid in tRNA is measured.

Animals↗
PubMed1984

Elevated ammonia release from dystrophic chicken muscle cell and fibroblast cultures.

The activity of adenosine monophosphate (AMP)-aminohydrolase, the major NH3-producing enzyme in skeletal muscle, was approximately 35% lower in 7-day dystrophic muscle cell cultures than in normal muscle cell cultures. However, the release rate of NH3 from dystrophic muscle cells was 45% higher than that from normal muscle cells. The reasons for this apparent discrepancy are not clear. To determine indirectly if deamination of amino acids from protein degradation contributed to NH3 release, cells were incubated with 100 micrograms/ml of the protease inhibitor, leupeptin. Leupeptin reduced the rate of NH3 release by only 18.8% in normal muscle cells and 16% in dystrophic muscle cells. The release of NH3 was also higher from dystrophic chicken fibroblast cultures.

Adenosine Deaminase↗
PubMed1984

Myosin heavy chain concentration, synthesis rate and degradation rate in normal and dystrophic chicken muscle cells in culture.

Myosin heavy chain concentrations, synthesis rates and degradation rates were studied in muscle cell cultures prepared from the breast muscle of 13-day normal (white leghorn) and dystrophic (line 307) chicken embryos. Muscle cells were studied after 7 days in culture, at which time they had reached a steady state with respect to myofibrillar protein synthesis and degradation. The quantity of myosin heavy chain was 10.5 +/- 0.9 micrograms/culture (n = 32) in normal cells and 8.10 +/- 1.2 micrograms/culture (n = 31) in dystrophic cells. However, the myosin heavy chain synthesis rate was 23 500 molecules/min/nucleus in normal cells and 39 900 molecules/min/nucleus in dystrophic cells, as determined by pulse labeling with [3H]leucine and measurement of the specific radioactivity of tRNA precursor pools. Myosin heavy chain half-lives rates were calculated to be 30.6 h in normal cells and 15.6 h in dystrophic cells when corrections were made for reutilization of [3H]leucine. Thus, dystrophic muscle cultures accumulate less myosin heavy chain, despite their faster synthesis rate, because of faster degradation of myosin heavy chain.

Animals↗
PubMed1983

Control of respiratory pattern in conscious dog: effects of heat and CO2.

We measured tidal volume (VT) and inspiratory (TI) and expiratory (TE) durations in five conscious tracheostomized dogs breathing air or 5% CO2 in air either at normal (20 degrees C) or elevated (30 degrees C) ambient temperatures. Respiratory frequency ranged between 16 and 333/min due to changes in both TI and TE. During panting TI exceeded TE. During air inhalation instantaneous ventilation (V) spontaneously ranged from 100 to 1,600 ml . kg-1 . min-1. Hypercapnia, heat stress, or both, increased this range of V by increasing maximum V, primarily due to increases in mean inspiratory flow. Under these conditions, changes in TI accounted for more of the spontaneous changes in breath duration. During inhalation of air and 5% CO2, a positive correlation between VT and TI was obtained for TI between 0.13 and 1.05 s; above 1.05 s VT decreased. Heat stress increased VT at a given TI. We suggest that either the decay rate or position of the inspiratory off-switch threshold curve (Clark and von Euler, J. Physiol. London 222: 267, 1972) varies in conscious dogs. Shifts in either the reset (onset) value or decay rate of the curve yield a positive correlation between VT and TI. This modification to the Clark-von Euler model implies that the primary effect of anesthesia on respiratory control is fixation of the inspiratory off-switch threshold curve.

Animals↗
PubMed1982

Myocardial pH during regional ischemia: evaluation of a fiber-optic photometric probe.

The relationship between the decrease in intramyocardial extracellular pH and the degree of stenosis of the left anterior descending (LAD) coronary artery was studied in eight dogs pretreated with propranolol. Intramyocardial pH was measured with a miniature glass pH electrode and with a new photometric pH probe that uses fiber-optic filaments to measure the color change of an indicator substance in a small permeable chamber. The LAD was cannulated and perfused from the axillary artery. Cannula flow was measured with an electromagnetic flow probe, and regional myocardial blood flow (RMBF) was measured with radioactive microspheres before and at the end of a period of critical stenosis, 2/3 reduction of flow, or total occlusion of the LAD cannula. In the region of the glass electrode, the mean RMBF (+/-SE) decreased by 16.3 +/- 3.3, 52.7 +/- 7.3, and 84.8 +/- 6.5% during the three levels of stenosis, and the pH correspondingly decreased by 0.05 +/- 0.01, 0.29 +/- 0.10, and 0.94 +/- 0.17 units. In the region of the photometric probe, the RMBF decreased 19.1 +/- 1.3, 47.2 +/- 6.7, and 84.3 +/- 6.0%, and the pH decreased by 0.05 +/- 0.02, 0.14 +/- 0.04, and 0.76 +/- 0.18 units. There was no statistically significant difference between the two types of pH sensor.

Animals↗
PubMed1982

Cell differentiation, protein synthesis rate and protein accumulation in muscle cell cultures isolated from embryos of layer and broiler chickens.

Muscle cell cultures were prepared from the leg muscle of 12-d layer and broiler chicken embryos. Cultures were then compared over a 10-d period from their capacity to differentiate into multinucleated myotubes and to synthesize and accumulate protein. Differentiation was qualitatively similar in the two cell types as evidenced by myoblast fusion that occurred rapidly during the first 2 d and remained essentially constant between d 3 and 10. However, several quantitative differences were observed. Even though the number of myotubes per culture was comparable between layers and broilers throughout development, layer muscle cultures usually exhibited a higher percentage fusion and more myonuclei per culture than broiler muscle cultures. Additionally, the nuclear density (i.e., the number of nuclei per myotube segment) was approximately 25% greater in layer cultures than in broilers between d 2 and 10 in culture. The rate of incorporation of 3H-leucine into total protein during pulse labeling experiments was comparable in muscle cultures of layers and broilers; however, broiler muscle cells accumulated approximately 40% more total protein per nucleus between d 6 and 10. Myosin heavy chain synthesis rate was higher in layer than in broiler muscle cultures, but broiler muscle cultures accumulated approximately 30% more myosin heavy chain than layers between d 6 and 10. The half-life of myosin heavy chain was 45 h in layer muscle cultures and 103 h in broiler muscle cultures. Thus, the capacity of broiler cells to accumulate more muscle protein was primarily due to a drastically slower protein breakdown rate.

Animals↗
PubMed1981

Metabolism of myosin heavy chain in steady-state chick skeletal muscle cultures.

Synthesis, accumulation and breakdown of the 200000-mol.wt. heavy subunit of myosin were analysed over an 11 day period in muscle cell cultures isolated from the leg muscle of 12-day chick embryos. Muscle cells accumulated myosin heavy chain rapidly from days 2 to 5 and maintained a maximum, constant myosin-heavy-chain concentration between days 7 and 11. Myosin-heavy-chain content and breakdown rate were compared in steady-state muscle cultures grown either in the presence of an optimum batch of horse serum (control) or in the presence of horse serum that had been pre-selected for its ability to inhibit several-fold the rate of synthesis of myosin heavy chain (inhibitory). The quantity of myosin heavy chain in the inhibited cultures was decreased in direct proportion to the decrease in the rate of synthesis of myosin heavy chain; however, the half-lives of myosin heavy chain (control, 17.7h; inhibitory, 17.0h) were virtually identical. In contrast, the absolute rate of breakdown of myosin heavy chain, expressed as molecules/min per nucleus, was approx. 5-fold lower in the inhibited cultures (4.3 X 10(3) molecules/min per nucleus) than in the control cultures (21.7 X 10(3) molecules/min per nucleus). Thus, inhibition of myosin-heavy-chain synthesis in this case was accompanied by diminished myosin-heavy-chain concentration and absolute breakdown rate at the altered steady state, but relative myosin-heavy-chain breakdown rates were unchanged.

Animals↗
PubMed1981

Stimulation of myosin heavy chain synthesis in steady-state muscle cultures by the ionophore, A23187, requires transcription of messenger RNA.

After approximately one week in culture, embryonic chick skeletal muscle cells are at a steady state with respect to myosin heavy chain (MHC) concentration and synthesis rate. Muscle cells normally synthesize MHC at a maximum rate of 2.3 X 10 4 MHC/min/nucleus and contain approximately 3 X 10 7 MHC/nucleus. These cells also contain approximately 3500 copies/nucleus of MHC mRNA associated with polysomes and 1600 copies/nucleus of MHC mRNA localized in the nonpolysomal fraction. To determine if nonpolysomal MHC mRNA in mature muscle cultures could be recruited into active translation complexes when MHC synthesis was stimulated, muscle cultures were treated with the Ca 2+ ionophore, A23187 (0-1 micro M). The MHC synthesis rate was stimulated by 25 to 50% relative to stimulation of the rate of total protein synthesis in the presence of A23187, but this stimulation was blocked when 10 microgram/ml actinomycin D was also present. These results suggest that even though 30% of MHC mRNA is not actively engaged in MHC synthesis in mature muscle cultures, stimulation of MHC synthesis by A23187 results from transcription of new MHC mRNA rather than from utilization of pre-existing mRNA.

Animals↗