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Biomedical subjects

J F Watchko

Publications and source records attributed to J F Watchko.

At least 37 records · Page 2Linked to original sources
PubMed1997

Combined myofibrillar and mitochondrial creatine kinase deficiency impairs mouse diaphragm isotonic function.

Creatine kinase (CK) is an enzyme central to cellular high-energy phosphate metabolism in muscle. To characterize the physiological role of CK in respiratory muscle during dynamic contractions, we compared the force-velocity relationships, power, and work output characteristics of the diaphragm (Dia) from mice with combined myofibrillar and sarcomeric mitochondrial CK deficiency (CK[-/-]) with CK-sufficient controls (Ctl). Maximum velocity of shortening was significantly lower in CK[-/-] Dia (14.1 +/- 0.9 Lo/s, where Lo is optimal fiber length) compared with Ctl Dia (17.5 +/- 1.1 Lo/s) (P < 0.01). Maximum power was obtained at 0.4-0.5 tetanic force in both groups; absolute maximum power (2,293 +/- 138 W/m2) and work (201 +/- 9 J/m2) were lower in CK[-/-] Dia compared with Ctl Dia (2,744 +/- 146 W/m2 and 284 +/- 26 J/m2, respectively) (P < 0.05). The ability of CK[-/-] Dia to sustain shortening during repetitive isotonic activation (75 Hz, 330-ms duration repeated each second at 0.4 tetanic force load) was markedly impaired, with CK[-/-] Dia power and work declining to zero by 37 +/- 4 s, compared with 61 +/- 5 s in Ctl Dia. We conclude that combined myofibrillar and sarcomeric mitochondrial CK deficiency profoundly impairs Dia power and work output, underscoring the functional importance of CK during dynamic contractions in skeletal muscle.

Adenosine Triphosphatases↗
PubMed1997

Rat diaphragm oxidative capacity, antioxidant enzymes, and fatigue: newborn versus adult.

Little is known about the antioxidant capacity and oxidant-generating potential of newborn muscle, or how these properties compare with the adult and relate to fatigue resistance. We determined the 1) antioxidant enzyme activities [superoxide dismutase (SOD), catalase, glutathione peroxidase], 2) glutathione content, 3) oxidative capacity [indexed by succinic dehydrogenase activity], 4) extracellular cytochrome c reduction, and 5) efficacy of exogenously administered SOD in ameliorating fatigue in vitro of newborn and adult diaphragm (DIA). Newborn and adult DIA SOD activities were not different, whereas newborn catalase activity was greater, and newborn glutathione peroxidase activity and glutathione content less than adult DIA. Succinic dehydrogenase activity was approximately 2-fold greater in the adult compared with the neonate. Repetitive contractions led to a significant decline in newborn and adult DIA force; this decline was greater in the adult (78 +/- 4% decrement in force at 2 min) compared with newborn DIA (28 +/- 8% decrement in force at 2 min). Extracellular cytochrome c reduction was greater in adult as compared with newborn DIA during fatiguing contractions. Exogenous SOD attenuated fatigue in the adult, but had no effect on newborn DIA. We conclude that the oxidative capacity of the adult DIA is greater than that of the newborn and not matched by a concomitant increase in SOD activity. Our data suggest that the increased oxidative capacity relative to SOD activity in adult DIA may lead to oxidative stress and an enhanced susceptibility to fatigue.

Age Factors↗
PubMed1996

Developmental transitions in the myosin heavy chain phenotype of human respiratory muscle.

We studied the expression of myosin heavy chain (MHC) isoforms in the costal diaphragm (DIA) and the genioglossus (GG) muscles from 16 to 42 weeks gestation in the human using Western blotting techniques. Embryonic/neonatal MHC (MHCemb/neo) was the predominant isoform expressed in the DIA and GG at 16-24 weeks gestation. Subsequently, MHCemb/neo expression declined and the expression of MHCslow and MHC2A increased. At term, the DIA MHC phenotype was a composite of MHCemb/neo (15% of the total MHC complement), MHCslow (32%), MHC2A (47%), and MHC2B (6%); whereas, the GG was largely comprised of MHC2A (74%). We conclude that human DIA and GG demonstrate temporally dependent changes in MHC expression during gestation- and muscle-specific MHC phenotypes as they approach term.

Diaphragm↗
PubMed1996

Creatine kinase activity in rat skeletal muscle relates to myosin phenotype during development.

Creatine kinase (CK) has been implicated in the maintenance of skeletal muscle intracellular energy supply via its ATP buffering capacity. We examined the postnatal expression of CK activity and isoform phenotype in four skeletal muscles [diaphragm (DIA), intercostal (IC), external abdominal oblique (EAO), and the soleus (SOL)] of the rat. Moreover, we correlated CK activity during development with postnatal changes in myosin heavy chain (MHC) phenotype, the latter an index of relative changes in the energetic demands of muscle contractile proteins. CK activity was lowest in the immediate newborn period and increased in all muscles during postnatal development; the highest levels of CK activity were observed in the adult IC and EAO. CK activity did relate to the MHC phenotype as indexed by the ratio of adult MHC isoform content (slow + IIa + IIx + IIb) to developmental MHC isoform content (slow + neonatal; r2 = 0.93, p < 0.001). Stepwise regression revealed that type IIb MHC expression alone accounted for 79% of the developmental variance in CK activity. We conclude that CK activity increases during postnatal development in a muscle specific fashion and relates to the energetic demands of the muscle contractile proteins as reflected by MHC isoform composition. We speculate that the role of CK as an energy buffer is greatest in muscles expressing the IIb MHC isoform.

Animals↗
PubMed1995

SDH and actomyosin ATPase activities of different fiber types in rat diaphragm muscle.

In the rat diaphragm muscle, the histochemical classification of type I, IIa, IIb, or IIx fibers was correlated with myosin heavy chain (MHC) immunoreactivity. Expression of MHC isoforms in single dissected fibers was also assessed electrophoretically. Most fibers (approximately 86%) expressed a single MHC isoform, and when present, coexpression of MHC-2X and MHC-2B isoforms was most prevalent. Type I and IIa fibers were the smallest, type IIb fibers were the largest, and type IIx fibers were intermediate. Succinate dehydrogenase (SDH) and calcium-activated myosin adenosinetriphosphatase (actomyosin ATPase) activities were measured with quantitative histochemical procedures. Type I and IIa fibers had the highest SDH activities, followed in rank order by type IIx and IIb fibers. Type I fibers had the lowest actomyosin ATPase activity, followed in rank order by type IIa, IIx, and IIb fibers. Across all fibers, there was an inverse relationship between fiber SDH activity and cross-sectional area and a positive correlation between fiber actomyosin ATPase activity and cross-sectional area. The SDH and actomyosin ATPase activities of muscle fibers were also inversely correlated. These phenotypic differences in SDH and ATPase activities may be important in determining the contractile and fatigue properties of different fiber types in the rat diaphragm muscle.

Animals↗
PubMed1994

Ventilatory pump failure in premature newborns.

OBJECTIVE: To determine the prevalence of ventilatory pump failure in premature (< 34 weeks gestation) infants. DESIGN: Prospective clinical evaluation of all neonatal intensive care unit (NICU) admissions over a 12 month period in a large, university affiliated hospital. SUBJECTS: A series of 421 consecutive inborn premature infant admissions to the NICU. METHODS: Infants were followed for signs and symptoms of respiratory distress and monitored closely for evidence of respiratory failure requiring intubation and assisted ventilation. The indications for intubation and assisted ventilation were reviewed, and three such indications were considered clear manifestations of ventilatory pump failure, that is, delivery room resuscitation with CXR negative for evidence of parenchymal lung disease [DR/CXR-], hypercapnia (PaCO2 > 55 torr) [increases CO2], and apnea. RESULTS: A total of 192 premature infants (47% of study sample) required intubation and assisted ventilation. Failure of the ventilatory pump to sustain ventilation (DR/CXR-, increases CO2, apnea) accounted for 70 of these 192 (36%) premature infants. CONCLUSIONS: Ventilatory pump failure is a common clinical phenomenon in premature infants. Intensified research on the mechanisms and treatment of ventilatory pump failure might benefit a significant number of such newborns.

Humans↗
PubMed1994

Prevalence and lack of clinical significance of blood group incompatibility in mothers with blood type A or B.

PURPOSE: To examine the prevalence and clinical significance of blood group incompatibility in infants whose mothers have blood type A or B. METHODS: We prospectively analyzed cord blood samples from 4996 consecutive love-born infants for blood type, hematocrit, and results of direct antiglobulin (Coombs) test (DAT) and indirect Coombs test (ICT). OUTCOME MEASURES: Erythrocyte sensitization was determined by positive DAT or ICT results. Significant hyperbilirubinemia (> or = 224 mumol/L (12.8 mg/dl) and mean cord hematocrits were compared between mother-infant pairs with ABO incompatibility and positive DAT or ICT results and those with negative Coombs test results. RESULTS: Of all births, 6.9% (343/4996) were of infants who had ABO incompatibility and had been born to mothers with blood type B or A; 44 (13%) of 343 infants had a positive antiglobulin test result, of whom 43 had a positive ICT result only. Type A or B mothers were 5.5 times less likely to have sensitization than type O mothers; A-B, B-A, A-AB, and B-AB mother-infant pairs with a positive antiglobulin test result had mean cord hematocrits and rates of significant hyperbilirubinemia similar to those of corresponding pairs whose antiglobulin tests both showed negative results. Infants with a positive DAT result had lower mean cord hematocrits than infants with negative results on both antiglobulin tests or on a positive ICT result only. Significant hyperbilirubinemia was more frequent in infants with a positive DAT result than in infants with negative results on both antiglobulin tests or a positive ICT result only. CONCLUSION: Sensitization is much rare when the mother has blood type A or B than when she has blood type O, as demonstrated by the antiglobulin test. The incidence of significant hyperbilirubinemia and lower cord hematocrit is not increased by sensitization when the mother has type A or B.

ABO Blood-Group System↗
PubMed1994

Contractile properties of the developing diaphragm correlate with myosin heavy chain phenotype.

The objective of this study was to determine the relationship between developmental transitions in myosin heavy chain (MHC) composition and changes in maximum unloaded shortening velocity (Vo) and maximum specific force (Po) of the rat diaphragm muscle. The diaphragm was excised at postnatal days 0, 3, 7, 14, 21, and 28 and in adults. MHC isoform expression was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and laser densitometry. In muscle fiber bundles, Vo was determined at 15 degrees C by use of the "slack" test. Isometric Po was determined at 15 and 26 degrees C. Simple and stepwise regressions were used to evaluate the correlations between Vo, Po, and MHC phenotype transitions and the various developmental ages. The progressive increases in Vo and Po with age were found to be inversely correlated to MHC-neonatal isoform expression (r2 = -0.84 and -0.63, respectively) and positively correlated to MHC-2X (r2 = 0.78 and 0.57) and MHC-2B (r2 = 0.51 and 0.40) isoform expression (P < 0.001). Changes in MHC-neonatal isoform expression contributed to most of the developmental variance in Vo and Po, with changes in MHC-2X and MHC-2B expression also contributing significant increments to total variance. The postnatal increase in Vo most likely relates to differences in the actomyosin adenosinetriphosphatase activity between neonatal and adult fast MHC phenotypes. The increase in Po may reflect inherent differences in myofibrillar density, cross-bridge cycling kinetics, and/or the force produced per cross bridge among fibers composed of the different MHC isoforms.

Aging↗
PubMed1994

Age-related differences in diaphragm muscle injury after lengthening activations.

The susceptibility of postnatal day 15 and adult rat diaphragms (DIAs) to acute injury after repetitive isovelocity lengthening activations was examined in vitro. Forces were measured during two phases of each stimulation protocol: 1) isometric phase: during the first 300 ms of each 500-ms train, DIA length was not changed; and 2) isovelocity lengthening phase: during the remaining 200 ms of each stimulus train, DIA was lengthened at a constant velocity from 90 to 110% of optimal length. At maximal activation (75 Hz and a lengthening velocity of 1.0 optimal length per second), the maximum force measured during the isometric phase and that measured during the isovelocity lengthening phase were both greater in adult DIAs than in day 15 DIAs but both declined to a greater extent in adults with repetitive activation. Ultrastructural analysis showed that after lengthening activations muscle fiber injury was very evident in adult but much less prevalent in day 15 DIAs. This difference in susceptibility between the adult and day 15 DIAs did not depend on differences in peak force or absolute velocity of lengthening. We conclude that lengthening activations result in DIA injury and that the adult is more susceptible than its younger counterpart.

Aging↗
PubMed1994

Kernicterus in premature infants: current prevalence and relationship to NICHD Phototherapy Study exchange criteria.

OBJECTIVE: This study was undertaken to determine the current prevalence of kernicterus in premature neonates and to relate the occurrence of kernicterus to 1) the categorization of the infant as "at risk" by National Institute of Child Health and Human Development (NICHD) Phototherapy Study exchange transfusion criteria, and 2) the clinical management of the infant's hyperbilirubinemia. DESIGN: Retrospective review of postmortem and clinical records. SETTING: Magee-Womens Hospital, a University of Pittsburgh Medical Center affiliated hospital with approximately 10,000 deliveries per year and a Level III Neonatal Intensive Care Unit with about 1400 admissions annually. SUBJECTS: All neonates autopsied between January 1, 1984 and June 30, 1993 who were < 34 weeks gestation and who lived at least 48 hours; a total of 81 infants. RESULTS: Three infants had kernicterus resulting in a prevalence rate of 4%. These cases included: 1) a 33-week newborn with nonimmune hydrops and a peak bilirubin of 26 mg/dl; 2) a 25-week newborn with asphyxia, hyaline membrane disease, grade IV intraventricular hemorrhage, necrotizing enterocolitis, meconium peritonitis, sepsis, prolonged acidosis, and a peak bilirubin of 11.3 mg/dl; and 3) a 24-week newborn with asphyxia, hyaline membrane disease, grade III intraventricular hemorrhage, and a peak serum bilirubin of 18.5 mg/dl. Of the remaining 78 infants who did not have kernicterus, peak bilirubin ranged from 3.6 to 22.5 mg/dl and 56% had bilirubin levels greater than that suggested as a criterion for exchange transfusion by NICHD Phototherapy Study guidelines; yet all but three were managed with phototherapy alone. CONCLUSIONS: We conclude that kernicterus is currently an uncommon event in preterm infants, even when bilirubin levels are allowed to rise above those previously thought to place the premature infant at risk.

Bilirubin↗
PubMed1993

Postnatal expression of myosin isoforms in the genioglossus and diaphragm muscles.

We studied the expression of myosin heavy chain (MHC) and native myosin isoforms in the genioglossus (GG) and costal diaphragm (DIA) muscles of the rat during postnatal development using both denaturing and nondenaturing gel electrophoresis. Primary myotubes in both fast and slow muscles homogeneously express slow as well as embryonic myosin. Since the adult GG is comprised primarily of fast MHC isoforms, whereas the adult DIA is characterized by a mixture of MHC slow and fast isoforms, we hypothesized that the GG and DIA would be subject to different temporal patterns of MHC isoform expression during postnatal development. Native myosin and MHC gels demonstrated a persistence of neonatal MHC (MHC neo) on day 25 in the GG, whereas this isoform was not detected beyond day 21 in the DIA. The MHC phenotype in GG of the adult demonstrated a predominance of MHC 2X (35% +/- 8) and MHC 2B (45% +/- 10) with a smaller proportion of MHC 2A (19% +/- 5). In contrast, the MHC phenotype in adult DIA was characterized by approximately equal proportions of MHC slow (25% +/- 3), MHC 2A (34% +/- 10), and MHC 2X (31% +/- 12) with a small percentage of MHC 2B (9% +/- 7). These data suggest that postnatal regulation of MHC expression in the GG and DIA is muscle specific.

Analysis of Variance↗
PubMed1993

Regional distribution of myosin heavy chain isoforms in rib cage muscles as a function of postnatal development.

We studied the expression of myosin heavy chain (MHC) isoforms, utilizing electrophoretic methods, in rib cage (RC) muscles: the scalenus medius, the parasternal, cephalic, midthoracic, and caudal intercostal muscles; and in the diaphragm (DI) of rats during postnatal development and when mature. At day 1, all RC muscles and the DI expressed MHC neonatal/embryonic (69-92% of total MHC complement) with little MHC slow and 2A; the RC muscles alone expressed a small proportion of MHC 2B (2-4%). On day 4, MHC neonatal/embryonic expression still predominated (55-71%) but increased MHC 2A expression was observed in both the RC (11-21%) and DI (31%); MHC 2B (5-7%) was noted in the RC muscles but not the DI. By day 14, MHC neonatal/embryonic and 2A expression each comprised a third of the total MHC complement of the RC muscles, MHC 2X was first observed, and MHC 2B expression increased. The day 14 DI was comprised of equal proportions of MHC neonatal/embryonic, slow and 2A with little MHC 2X (11%). The adult and day 30 animals expressed comparable muscle-specific MHC phenotypes: the DI characterized by a proportional mixture of MHC slow, MHC 2A, and MHC 2X, with little MHC 2B, whereas the RC muscles expressed predominantly MHC 2B (40-62%). We conclude that the RC muscles and DI show comparable MHC phenotypes in the immediate newborn period but differ in their MHC expression during postnatal development and when mature. The RC muscles show only minor intermuscle variations in MHC phenotype during development, and when mature are characterized by fast MHC isoform expression, particularly MHC 2B.

Aging↗
PubMed1993

Effect of undernutrition on contractile and fatigue properties of rat diaphragm during development.

The present study was designed to assess the effects of combined pre- and postnatal undernutrition on the in vitro contractile and fatigue properties of the rat diaphragm during development. In vitro direct stimulation of costal diaphragm from control (CTL) and undernourished (UN) rats was done on postnatal days 1, 4, 14, 21, 30, 40, 50, and 60. Combined pre- and postnatal undernutrition resulted in stunted animal growth but did not alter the diaphragm-to-total body weight ratio. Twitch contraction time, half-relaxation time, and force-frequency relationships were not consistently affected by undernutrition. Specific twitch force and specific tetanic force were also unchanged in the UN group. Fatigue resistance was high and comparable in UN and CTL groups at days 1 and 4. At day 14 and thereafter, fatigue resistance declined but was consistently higher in the UN than in the CTL group. We conclude that combined pre- and postnatal undernutrition results in a significant increase in fatigue resistance of the diaphragm compared with CTL, whereas diaphragm muscle contractile properties are not appreciably affected by prolonged undernutrition.

Aging↗
PubMed1993

Respiratory muscle fatigue resistance relates to myosin phenotype and SDH activity during development.

We correlated the fatigue resistance (FR) of the costal diaphragm (DIA) and external abdominal oblique (EAO) of the rat during postnatal development with their respective 1) myosin heavy chain (MHC) phenotypes and 2) oxidative capacities [indexed by quantitative measurements of succinic dehydrogenase (SDH) enzyme activity]. FR was measured in vitro during isometric contractions with the use of the Burke fatigue test. FR of the DIA and EAO was high in newborns and declined during postnatal development. SDH activity was uniformly low in neonatal DIA and EAO and increased during early postnatal development before declining to adult levels. FR did not significantly correlate with SDH activity (r2 = 0.01) but did relate to the MHC phenotype as indexed by the ratio of adult MHC isoform content (slow + IIa + IIx + IIb) to developmental MHC isoform content (slow + neonatal; r2 = 0.88, P < 0.01). Stepwise regression revealed that neonatal MHC expression alone accounted for 60% of the developmental variance in FR. The correlation between FR and MHC phenotype was improved if SDH was also considered, i.e., the ratio of SDH to MHC phenotype (r2 = 0.99, P < 0.01). We conclude that FR of respiratory muscle during development relates to a balance between the energetic demands of the muscle contractile proteins as reflected by MHC isoform composition and its oxidative capacity with MHC phenotype alone exerting a strong predictive effect on FR.

Animals↗
PubMed1992

Contractile properties of the rat external abdominal oblique and diaphragm muscles during development.

We studied the in vitro contractile and fatigue properties of the rat external abdominal oblique (EAO) and costal diaphragm (DIA) muscles during postnatal development. Isometric twitch contraction (CT) and half-relaxation (RT1/2) times were longer in both the EAO and DIA muscles during the early postnatal period and decreased with age. In the first postnatal week, the CT and RT1/2 were longer in the EAO than the DIA muscle. At 14 days of age and thereafter, the CT and RT1/2 were shorter in the EAO than in the DIA muscle. Force-frequency relationships of the EAO and DIA muscles changed during postnatal development such that the relative force (percent maximum) generated at lower frequencies (less than 15 pulses/s) decreased with age. Moreover the relative force generated by the EAO muscle at lower frequencies was greater than that of the DIA muscle during the early postnatal period but less than that of the DIA muscle in adults. The specific force of both the EAO and DIA muscles increased progressively with age. There were no differences in specific force between the EAO and DIA muscles at any age. The fatigability of the EAO and DIA muscles was comparable during the early postnatal period and increased in both muscles with postnatal development. In adults the EAO muscle was more fatigable than the DIA muscle. We conclude that the contractile and fatigue properties of the EAO and DIA muscles undergo significantly different postnatal transitions, which may reflect their functional involvement in sustaining ventilation.

Animals↗
PubMed1992

Postnatal expression of myosin isoforms in an expiratory muscle--external abdominal oblique.

We studied the postnatal expression of heavy-chain (MHC) and native myosin isoforms in an expiratory abdominal muscle of the rat, the external abdominal oblique (EO). Moreover, we contrasted EO myosin expression with that of the costal diaphragm (DIA) to draw inspiratory vs. expiratory muscle comparisons during development. Examination of MHC gels demonstrated a mature phenotype of slow and adult fast myosin isoforms at an earlier age in the EO (day 60) than in the DIA [day > 115 (adult)]. The mature MHC phenotype of the EO was characterized by a preponderance of MHC 2B, whereas the DIA was characterized by approximately equal portions of MHC slow, MHC 2A, and MHC 2X. During early postnatal development, there was a delay in the expression of MHC 2A in the EO compared with the DIA. However, MHC 2B, expressed later in development in both muscles, was noted in the EO before the DIA. We conclude that 1) the EO mature myosin phenotype is characterized by a preponderance of fast myosin isoforms and 2) the EO and DIA muscles are subject to different temporal patterns of isoform expression during postnatal development.

Abdominal Muscles↗
PubMed1992

Control of genioglossal muscle activity in the anesthetized piglet: the role of vagal afferents.

We examined genioglossal muscle electromyogram activity during room air breathing and hyperoxic hypercapnia in 10 anesthetized (halothane) newborn piglets before and after bilateral midcervical vagotomy. With vagal afferents intact, genioglossal activity was absent during room air breathing in 10/10 study animals and was recruited in only 4/10 piglets during carbon dioxide breathing. After vagotomy, genioglossal activity remained absent in 9/10 study animals during room air breathing but was recruited in 10/10 piglets during the hypercapnic gas exposure at arterial CO2 tensions comparable to prevagotomy levels. We conclude that vagal afferent feedback modulates genioglossal activity in anesthetized newborn piglets and exerts an inhibitory influence on the activity of this muscle during hyperpnea induced by carbon dioxide breathing.

Anesthesia↗