Biomedical subjects

K Schwartz

Publications and source records attributed to K Schwartz.

318 records · Page 18Linked to original sources

PubMedDate not supplied

Cardiac myosin. Phylogenic and pathological changes.

Several proteins of the sarcomere differ from one muscle to the other, but it is also becoming evident that cardiac myosin, tropomyosin and troponin are species specific. Moreover, several properties of cardiac myosin could be modified under the influence of thyroxine, exercise, or overloading. These changes are closely related to the speed of shortening of the muscle and to the degree of stimulation of protein synthesis, but nobody is presently able to say if, in heart overloading, the modifications of myosin are a primary defect which is the origin of the failure or if they are only expressing a better adaptation of myocardial efficiency to the decrease of work.

Adenosine Triphosphatases↗

PubMedDate not supplied

Experimental systolic and diastolic overloading in rats: total proteins turnover rate. Enzymatic and structural properties of myosin.

The fractional turnover rate of the total cardiac proteins has been measured by using the continuous infusion technique with 3H lysine. It augments by a factor of 3 in systolic as well as in diastolic overloading, but in the former the peak was reached within the first week after operation and in the later the peak was not reached until the 14th day. The myosin structure and enzymatic properties have been studied in several huge hypertrophic hearts (around 100% hypertrophy). In this condition the burst size of myosin is normal, as well as its K+ ATPase, but there is a sharp decline in the Ca2+ ATPase activity. Moreover, antibodies against native or defolded heavy meromyosin exhibit, a vertical shift in microcomplement fixation when made to react with molecules extracted from hypertrophied hearts. The normal isozymic pattern of rat heart myosin, as shown in non dissociating electrophoresis, was reversed.

Adenosine Triphosphatases↗

PubMedDate not supplied

The relationship of counselor and peer alliance to drug use and HIV risk behaviors in a six-month methadone detoxification program.

The purpose of this study was to examine the relationship of treatment outcomes in opioid detoxification to levels of counselor and peer alliance. Forty-one subjects were recruited from a larger, 180-day study of psychosocial treatment. Beginning at day 90, subjects completed monthly measures of alliance. Outcome measures included treatment retention, drug use and self-reported HIV risk. Measures of alliance were found to be internally consistent and moderately stable over time. During the final 30 days of the methadone taper, higher levels of both types of alliance were associated with less use of illicit opioids. Alliance with counselor was associated with less frequent needle sharing. For subjects who could be located for 30-day follow-up, greater alliance with peers was associated with more frequent HIV (sexual) risk behaviors. Results suggest that treatment outcome may be improved through approaches that address a patient's alliance with both counselor and peers.

HIV Seropositivity↗

PubMedDate not supplied

Genetic heterogeneity of familial hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy (FHC) is characterized by an autosomal dominant transmission, a left ventricular hypertrophy and a myocardial disorganization. A first morbid gene coding for the beta-myosin heavy chain (beta-MHC) located on chromosome 14q11-q12 has been identified and genetic heterogeneity has been demonstrated. We performed linkage and haplotype analysis of 17 French families with microsatellite markers located to the beta-MHC locus and we searched for a new locus in a family for which the beta-MHC locus was excluded. Two novel missense mutations were identified in exon 13 of the beta-MHC resulting in the replacement of 403 arginine by a leucine or a tryptophan in two different families. In one other family, systematic screening of the genome with highly informative markers allowed us to find a new locus for FHC on chromosome 11.

Cardiomyopathy, Hypertrophic↗

PubMedDate not supplied

Heart contractile proteins.

That several proteins of the sarcomere differ from one muscle to the next is well documented, and it is becoming evident that homogeneous muscles, like the heart, are also species specific. 1) Clear-cut evidence is available concerning myosin, and, to date, several types of molecules have been described. a) The myosins of white skeletal, heart, and smooth muscle differ in the activity of their Ca2+ and K+ATPases, as also in the structure of their light subunits. b) The Ca2+ATPases of the various cardiac myosins have been shown to exhibit species differences and correlate with the speed of shortening of the muscle. 2) The structures of tropomyosin, some troponin components, and alpha actinin (but not actin) appear to be unlike in the different types of muscle. 3) These phylogenic modifications may be related to the changes characteristic of the particular muscles under pathological conditions, which are accompanied by substantial increase in protein synthesis.

Actins↗

PubMedDate not supplied

Heterozygous mutation in the pore of potassium channel gene KvLQT1 causes an apparently normal phenotype in long QT syndrome.

Mutations in KvLQT1, a gene encoding a potassium channel, cause both the recessive Jervell and Lange-Nielsen (JLN) syndrome and the dominant Romano-Ward (RW) syndrome. These diseases are characterised by a prolonged QT interval on the ECG, syncopes and sudden death due to cardiac arrhythmias. The JLN syndrome is also associated with a congenital bilateral deafness. We report here a novel missense mutation, W305S, in the pore region of KvLQT1 identified by PCR-SSCP analysis in two consanguineous JLN families. In contrast to several missense mutations found in the same region of KvLQT1 in RW patients which are associated with severe cardiac phenotypes, the W305S mutation is responsible for an apparently normal phenotype in heterozygous JLN carriers.

Consanguinity↗

PubMedDate not supplied

Cardiac myosin binding protein C gene is specifically expressed in heart during murine and human development.

Cardiac myosin binding protein C (MyBP-C) is a substantial component of the sarcomere, with both structural and regulatory roles. The gene encoding cardiac MyBP-C in humans is located on chromosome 11p11.2, and mutations that are most predicted to produce truncated proteins have been identified in this gene in unrelated families with familial hypertrophic cardiomyopathy (FHC). To understand better the pathophysiology of FHC and with a view to the development of animal models for this disease, we have investigated by in situ hybridization the pattern of expression of the cardiac MyBP-C gene during human and mouse development using species-specific oligonucleotide probes. From 4 weeks of human development, a strong labeling of cardiac MyBP-C mRNAs was unambiguously detected in all heart compartments, and no signal could be visualized in somites. In murine embryos, from embryonic day 9.5 until birth, a strong signal was detected exclusively in the heart. Our results showed that during both human and murine development, in contrast to chicken development, the cardiac MyBP-C gene is abundantly and specifically expressed in the heart.

Animals↗

PubMedDate not supplied