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Biomedical subjects

C D Moyes

Publications and source records attributed to C D Moyes.

At least 37 records · Page 2Linked to original sources
PubMed1998

Regulation of muscle mitochondrial design.

Mitochondria are responsible for the generation of ATP to fuel muscle contraction. Hypermetabolic stresses imposed upon muscles can lead to mitochondrial proliferation, but the resulting mitochondria greatly resemble their progenitors. During the mitochondrial biogenesis that accompanies phenotypic adaptation, the stoichiometric relationships between functional elements are preserved through shared sensitivities of respiratory genes to specific transcription factors. Although the properties of muscle mitochondria are generally thought to be highly conserved across species, there are many examples of mitochondrial differences between muscle types, species and developmental states and even within single cells. In this review, we discuss (1) the nature and regulation of gene families that allow coordinated expression of genes for mitochondrial products and (2) the regulatory mechanisms by which mitochondrial differences can arise over physiological and evolutionary time.

Animals↗
PubMed1997

Mitochondrial biogenesis during cellular differentiation.

Mitochondrial biogenesis was studied during differentiation of two immortalized cell lines (C2C12, 3T3) with enzyme measurements, Northern blots, and quantitative ultrastructure. Citrate synthase, isocitrate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase (nuclear encoded, mitochondrial matrix location) showed linear, four- to sixfold increases in enzymatic activity in C2C12 cells but increased exponentially in 3T3 cells. Cytochrome oxidase and NADH dehydrogenase (nuclear and mitochondrial encoded, cristae location) increased to a lesser extent and with a pattern dissimilar to the first group. Northern blots and activity of succinate dehydrogenase (cristae location but entirely nuclear encoded) suggested the groupings were based on location of the genes rather than the mature enzyme. However, quantitative electron microscopy and comparisons with adult tissue suggested that mitochondrial ultrastructure can influence the change in cristae enzymes. Cristae surface area per unit mitochondrial volume and per unit cell volume increased much less than did cristae enzymes. Available space on the inner membrane may become limiting and account for some aspects of the pattern of change in electron transport enzymes during differentiation.

3T3 Cells↗
PubMed1996

Hepatitis B infection in households of HBsAg positive New Zealand children.

AIMS: To determine, from data obtained in a school-based hepatitis B vaccination programme, the prevalence of hepatitis B virus (HBV) infection in household contacts of children found to be hepatitis B surface antigen (HBsAg) positive. METHODS: Children who were HBsAg positive were visited in their homes 6 months or more after their initial blood test. Blood was drawn to confirm HBsAg status, and to ascertain HBeAg status. Their household contacts were tested for HBV seromarkers. RESULTS: Visits were made to homes of 931 children initially found to be HBsAg positive. Nine hundred and seven of these children (97.4%) were still HBsAg positive and thus confirmed to be chronic HBsAg carriers. The testing of 2957 household contacts of HBsAg positive schoolchildren revealed that 719 (24.3%) were HBsAg positive, a rate many times higher than that in the schoolchildren initially tested. Total HBV seromarker rates were highest in Asian households, and lowest in Europeans where 57% had been infected and 12% were HBsAg positive. Ethnic differences were largely accounted for by variation in maternal HBsAg status, reflecting different rates of perinatal infection. CONCLUSIONS: All family and household contacts of individuals identified as presumptive HBsAg carriers should be tested for HBV seromarkers as a routine. It is particularly important to ensure full prophylaxis against perinatal infection.

Adolescent↗
PubMed1996

Cloning and expression of salmon cardiac troponin C: titration of the low-affinity Ca(2+)-binding site using a tryptophan mutant.

Activation of cardiac actomyosin ATPase requires the occupation of the single low-affinity Ca(2+)-binding site of troponin C (cTnC). Previously, we demonstrated pronounced differences between mammals and cold-water salmonid fish in the Ca2+ sensitivity of cardiac preparations, particularly in relation to temperature [Churcotte, C., Moyes, C. D., Baldwin, K., Bressler, B., & Tibbits, G. F. (1994) Am. J. Physiol. 267, R62-R70]. In this study, we examine the extent to which cTnC structure could account for the observed differences in myofibrillar Ca2+ sensitivity. Salmonid (Oncorhynchus mykiss) cTnC was cloned, sequenced, and expressed in Escherichia coli as a maltose-binding protein fusion. The coding region has 87% homology with human cTnC cDNA and differs in 13 of 161 amino acid residues from the human/bovine/porcine isoform. The sequence corresponding to the single regulatory Ca(2+)-binding site II is completely homologous to that of mammals. The protein expressed exhibits optical properties similar (circular dichroism, intrinsic fluorescence) to those of cTnC purified from salmonid (Salmo salar) and bovine ventricle. A single tryptophan residue was introduced into the inactive Ca(2+)-binding site I (ScTnC-FW27) to facilitate Ca2+ titration. The Ca(2+)-binding constant (K1/2 = 5.33 pCa units) was within the range reported for the low-affinity sites of mammalian cTnC. Although differences in TnC primary structure are striking, Ca2+ affinity of intact cardiac myofibrils is likely influenced by interactions with other troponin proteins.

Amino Acid Sequence↗
PubMed1995

Respiratory symptoms and environmental factors in schoolchildren in the Bay of Plenty.

AIMS: To determine the prevalence of respiratory symptoms in children and to examine associations with environmental factors in the Bay of Plenty. METHODS: International Study of Asthma and Allergies in Childhood (ISAAC) questionnaires were distributed to 13-14 year old children and to care-givers of 6-7 year old children as part of the ISAAC study. RESULTS: Completed questionnaires were received for 2614 primary and 2752 secondary students. Analysis by district showed no consistent association with exposure to industrial emissions from paper mills, natural sulphur fumes, or climatic variation. All districts are subject to high levels of pollen. Symptom prevalence was close to the mean for New Zealand centres participating in the ISAAC survey. Night cough and nasal symptoms were more common in secondary pupils exposed to smoking in the home, but there was no consistent association between passive smoking and wheeze or diagnosed asthma. Children from larger households reported less wheezy symptoms and less diagnosed asthma. CONCLUSIONS: There was no consistent evidence of an effect on respiratory morbidity from natural fumes, industrial air pollution, or climate. The indoor environment is probably of greater importance in this population.

Adolescent↗
PubMed1994

Hypernatraemia: still seen as a problem in paediatric practice.

AIMS: To illustrate that hypernatraemia is still seen as a problem in paediatric practice and to discuss its management. METHODS: A collection of four patients with hypernatraemia from different causes are reported. Recommended treatment include initial plasma expanders, where necessary, followed by gradual rehydration to prevent cerebral oedema using fluid containing 75-80 mmol/L of sodium until adequate urine output is observed, followed by a maintenance rate of solution containing 35-40 mmol/L of sodium over 48 h. RESULTS: All four patients recovered completely and without complications. CONCLUSIONS: Hypernatraemia is still seen in practice as an important problem. Recommended treatment is gradual rehydration with appropriate concentrations of electrolyte and glucose mixture.

Humans↗
PubMed1994

Temperature and pH effects on Ca2+ sensitivity of cardiac myofibrils: a comparison of trout with mammals.

Active salmonids maintain myocardial contractility at temperatures that are cardioplegic for mammals. We postulated that myofibrillar Ca2+ sensitivity in the trout heart might 1) exhibit lower temperature dependence and/or 2) be greater over the range of physiological temperatures. Temperature-induced changes in intracellular pH may also play a role as alkalosis typically increases calcium affinity of myofibrillar adenosinetriphosphatase (ATPase). Ca2+ sensitivities of ventricular myofibrillar ATPase were determined in rats and in rainbow trout (Oncorhynchus mykiss) over a physiological range of pH and temperatures. Maximal myofibrillar ATPase activities of each species were similar and equally affected by temperature. Trout myofibrillar ATPase lost Ca2+ dependence at 37 degrees C. At constant pH, reduced temperature decreased calcium affinity more in trout (0.35 pCa/10 degrees C) than in rat (0.08-0.16 pCa/10 degrees C). Under alpha-stat conditions, the effects of temperature were reduced in both trout (0.2 pCa/10 degrees C) and rat (no significant effect). Over trout physiological temperatures, Ca2+ sensitivity was greater than rat at 37 degrees C. Qualitatively similar results were observed in studies measuring tension in skinned trout ventricular fibers. One mechanism by which the trout heart is able to maintain contractility at low temperatures is through the inherent higher Ca2+ sensitivity of the contractile element compared with mammalian species.

Adenosine Triphosphatases↗
PubMed1993

Liver function of hepatitis B carriers in childhood.

This study followed 314 children who were carriers of hepatitis B virus for 2 to 4 years and compared them with noncarriers, matched for age and sex, from the same community. No confirmed carrier lost hepatitis B surface antigen. Hepatitis B e antigen (HBeAg) was lost at a rate of 10.6% per year; the rate of decay was not affected by age or gender. Liver enzymes were higher in HBeAg-positive than in HBeAg-negative carriers and loss of HBeAg was usually followed by return to values in the normal range. There was evidence, however, of persistent mild liver dysfunction in carriers even after development of antibody to HBeAg. Serum alanine aminotransferase concentrations above twice the upper limit of normal were observed in 7% of carriers on at least one occasion but persisted for more than 1 year in less than 1% and clinical manifestations were rare. The hepatitis B carrier state was uncomplicated during the course of this study. However, risks of subsequent serious disease in adult life may be significant and continued surveillance of carriers is important for individual protection and to determine adverse prognostic features.

Adolescent↗
PubMed1992

Immunisation status of children in the eastern Bay of Plenty.

AIM: To assess the status of immunisation of children in the eastern Bay of Plenty. METHOD: Survey of general practitioner records and case notes of all resident children born over a period of two years and aged from five to 29 months. Immunisation was considered up to date if received within a reasonable period of the expected time. RESULTS: One thousand five hundred and ninety-three children were studied (97% of those known to be resident). The six week immunisations were received by 91%, 88% received the three month, and 81% the five month vaccines. Delivery of second year immunisation was much less successful, only 72% receiving measles or MMR vaccine despite publicity about a current measles epidemic and 61% the eighteen month vaccines. CONCLUSION: Forty-three percent children of two years of age had not received the full recommended immunisation schedule. Some of the contributing factors were identified and measures that could improve immunisation uptake are discussed.

Child, Preschool↗
PubMed1992

Hepatitis B vaccination in children: five year booster study.

AIM: to demonstrate that appropriate doses of hepatitis B vaccines would be protective for at least five years in children. This would be shown by administering booster doses and measuring the response. METHODS: 2 micrograms intramuscular (IM) doses of Merck Sharp and Dohme (MSD) recombinant DNA vaccine (rDNAV) were given to 318 children who had received age appropriate doses of MSD plasma derived vaccine (PDV) five years earlier. Sera were tested for hepatitis B virus (HBV) seromarkers pre- and postbooster. RESULTS: all children who had responsed to primary immunisation demonstrated an anamnestic response. The geometric mean titre (GMT) of antibody to hepatitis B surface antigen (antiHBs) rose from 89 to 4777 IU/L. AntiHBs was detected in 94% of vaccinees just prior to the five year booster, and 96.5% a mean of 10 days later. CONCLUSION: when initial vaccine seroconversion is satisfactory, protection of responders persists for at least five years, assuming that the response to vaccine boosters mimics the response to wild virus. Therefore, for population control of hepatitis B in children in endemic areas, booster doses are not required for at least five years.

Antibodies, Viral↗
PubMed1992

Recovery metabolism of trout white muscle: role of mitochondria.

Recovery from burst exercise in fish is very slow. Lactate conversion to glycogen occurs primarily within white muscle and must be fueled by mitochondrially produced ATP. In a parallel study we characterized the changes in tissue metabolites associated with burst exercise and recovery in rainbow trout (Oncorhynchus mykiss) white muscle. The present study examines whether the mitochondrial capacity to produce ATP may limit the rate of recovery of trout white muscle. The cost (ATP.min-1.g-1) of glycogen resynthesis (0.05 mumol lactate converted.min-1.g tissue-1) was compared with the mitochondrial capacity to produce ATP. The cost of recovery can be met by only 3.5% of the maximal mitochondrial capacity. In fact, during recovery trout white muscle mitochondria operate at a small fraction of their in vitro maximum. This capacity is suppressed in vivo by highly inhibitory ATP/ADP and limiting phosphate. The primary signal for increased ATP synthesis associated with recovery is not a change in ATP/ADP but probably phosphate, elevated because of phosphocreatine hydrolysis and adenylate catabolism in the purine nucleotide cycle. At low ADP availability and suboptimal phosphate (less than 5 mM), acidosis enhances respiration. At high respiratory rates mitochondrial pyruvate oxidation is sensitive to pyruvate concentration over the physiological range (apparent Michaelis constant = 35-40 microM). This sensitivity is lost at the low rates that approximate in vivo respiration. Changes in lactate do not affect the kinetics of pyruvate oxidation. Fatty acid oxidation may spare pyruvate and lactate for use in glyconeogenesis, primarily through allosteric inhibition of pyruvate dehydrogenase rather than covalent modification.

Adenosine Diphosphate↗
PubMed1992

Integrating metabolic pathways in post-exercise recovery of white muscle.

Purine nucleotides (ATP, ADP, AMP, IMP), creatine, phosphocreatine, lactate, pyruvate and glycogen were measured in rainbow trout (Oncorhynchus mykiss) white muscle following exercise to exhaustion. Estimates of intracellular pH permitted calculation of free concentrations of nucleotides ([nucleotide]f) required for most models of control of energy metabolism. Creatine charge, [PCr]/([PCr]+[Cr]), fell from 0.49 +/- 0.05 (mean +/- S.E.M.) to 0.08 +/- 0.02 with exercise but recovered completely by the first sample (2 h). Although [ATP] declined to 24% of resting levels and recovered very slowly, RATP, [ATP]/([ATP]+[ADP]f+[AMP]f), and energy charge, EC, ([ATP]+0.5[ADP]f)/([ATP]+[ADP]f+[AMP]f), recovered as quickly as creatine charge. Changes in [IMP] mirrored those in [ATP], suggesting that AMP deaminase is responsible for maintaining RATP and EC. Recovery of carbon status was much slower than recovery of energy status. Lactate increased from 4 mumol g-1 at rest to 40 mumol g-1 at exhaustion and did not recover for more than 8 h. Glycogen depletion and resynthesis followed a similar time course. During the early stages of recovery, calculated [ADP]f declined by more than 10-fold relative to the resting values. The resulting high [ATP]/[ADP]f ratios may limit the rate at which white muscle mitochondria can produce ATP to fuel glycogenesis in situ. It is postulated that the high [ATP]/[ADP]f ratios are required to drive pyruvate kinase in the reverse direction for glyconeogenesis in recovery.

Adenine Nucleotides↗
PubMed1991

Peroxisomal beta-oxidation: insights from comparative biochemistry.

The activities of fatty acyl-CoA oxidase (FAO) and carnitine palmitoyl transferase (CPT), indices of the capacities of peroxisomal beta-oxidation and mitochondrial beta-oxidation, respectively, were determined in livers of several vertebrate species notable for differences in dietary fatty acid composition. In suckling rats FAO activities were half that in adult rats and CPT/FAO ratios twice that of adult rats. As their milk diet is dominated by medium chain fatty acids, this observation is consistent with current ideas about the role of peroxisomal beta-oxidation in rat liver in oxidation of long chain unsaturated fatty acids. In nectar-feeding hummingbirds (fatty acids synthesized de novo) FAO activities were 50% greater than adult rats and CPT/FAO ratios one-third less than adult rats, suggesting that peroxisomal beta-oxidation is relatively more important in this species, despite a fatty-acid-poor diet. In marine fish (herring, dogfish shark, hagfish) FAO activities were all less than 15% that of rats and undetectable in hagfish. CPT/FAO ratios were greater in herring (8.1) and hagfish (greater than 30) than adult rats (3.1), suggesting that peroxisomal beta-oxidation is relatively less important in these species despite a natural diet containing high levels of long chain polyunsaturated fatty acids. These data are discussed in relation to current ideas about the role of peroxisomes in beta-oxidation of fatty acids.

Acyl-CoA Oxidase↗
PubMed1990

Hepatitis B vaccine boosters: further studies in children.

Two groups of children were given reduced dose boosters with Merck Sharp and Dohme (MSD) recombinant DNa, yeast derived hepatitis B vaccine (YDV), 30 and 34 months respectively after primary immunisation with MSD plasma derived vaccine (PDV). In the first group of unselected children the geometric mean titre (GMT) rose from 387 to 8346 IU/L, with all children protected. The second group were selected as the poorest responders to their primary course of vaccine. The booster raised the GMT from 14.6 to 325 IU/L, with 95% having protective levels of anti-HBs (greater than 10 IU/L). This study confirms that the vaccine used by the New Zealand Department of Health for the hepatitis B immunisation programme in preschoolers, will provide protection for the great majority of children for at least three years.

Adolescent↗