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We have isolated cDNA clones from thyrotoxic (pMHCa) and normal (pMHC(8) adult rabbit hearts. Restriction map analysis and DNA sequence analyses show that, although there is strong homology between overlapping regions of the two clones, they are distinctly different. The two clones exhibited 78483% homology between the derived amino acid sequences and those determined by direct amino acid sequence analysis of rabbit fast skeletal muscle myosin heavy chains. The clones specify a segment of the myosin heavy chain corresponding to subfragment 2 and the COOH-terminal portions of subfragment 1. Nuclease S1 mapping was used to compare transcription of the two clones with expression of the a and (3 forms of myosin heavy chains in the ventricles of thyrotoxic, hypothyroid (propylthiouracil-treated), and normal rabbits. Thyrotoxic ventricles contained only pMHCa transcripts whereas hypothyroid ventricles contained exclusively pMHC(3 transcripts. These data correlate well with the presence of a-and (3-form myosin heavy chains. In the normal young adult rabbit, pMHC(3 transcripts predominate, agreeing with the known (3 form/a form ratio of 4: 1. We therefore conclude that pMHCa and pMHCP contain sequences of the a-and (-form myosin heavy chain genes, respectively.Myosin, a major contractile protein of skeletal and cardiac muscle, is composed of two 200,000-dalton heavy chains (HCs) and two sets oflow molecular weight light chains. The active center of myosin ATPase resides in the globular head of the heavy chain. This enzymatic activity is correlated with contractile velocity in skeletal muscle (1) and thus appears to be an important determinant of contractile function. Numerous polymorphic forms of myosin HC exist, not only in different types of muscle-e.g., fast and slow skeletal and cardiac-but also within each muscle type (2-12). Expression of these forms follows a developmental pattern (12-18) that may be altered by changes in the physiological (19-21) and hormonal (10-13) milieu ofthe cell.Cardiac ventricular muscle contains at least two formsreferred to as a and (3 (9)-of myosin HC. Electrophoresis of myosin under nondenaturing conditions reveals three bands; V1 and V3 are homodimers containing the a and 3 forms, respectively, whereas V2 is a heterodimer (9, 13). The ATPase activity of myosin with a-form HCs has been shown to be considerably higher than that of myosin with (-form .The expression of a-and (3form myosin HCs follows a defined developmental pattern that varies in different animal species. It has been shown that in rabbit the ( form/a form ratio is =3: 1 during the last halfofthe gestational period. After birth, the relative amount of the a form increases so that, during the first 2 wk postnatally, this ratio is 1: 1 (12, 14). Thereafter, the a form decreases and, in the old adult, the 3 form is present almost exclusively (12,14). In the young adult animals used in this study, the ( form/a form ratio was =4:1 (12 (27).Construction and Screening of cDNA Clones. Single-and double-stranded cDNA wa...

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Hyperglycemia causes increased protein glycation and the formation of early glycation products and advanced glycation end products (AGEs) which are major factors responsible for the complications associated with diabetes. The aim of the present study was to investigate the antioxidant as well as antiglycative potential of ethyl acetate fraction of guava leaves. Oral administration of the extract at different doses showed a significant decrease in blood glucose level. It also showed an improved antioxidant potential as evidenced by decreased lipid peroxidation and a significant increase in the activity of various antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Glycated hemoglobin as well as fructosamine which are indicators of glycation was also reduced significantly in treated groups when compared to diabetic control. In vitro studies also support the antioxidant as well as antiglycative potential of guava leaves.

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