Genbank accession #: AJ237597

Plant Molecular Biology -     

Genbank accession #: 133708

Plant Molecular Biology -     

Mevalonate kinase in lysates of cultured human fibroblasts and lymphoblasts: kinetic properties, assay conditions, carrier detection and measurement of residual activity in a patient with mevalonic aciduria

An assay has been developed for the measurement of mevalonate kinase activity in extracts of cultured human fibroblasts and lymphoblasts. Individual elements of the assay were investigated in order to achieve optimum conditions. Apparent Michaelis constants (KMapp) for the substrates mevalonic acid and adenosine-5'-triphosphate were 22 +/- 10 mumol/l and 0.42-0.53 mmol/l, respectively, in lysates of control fibroblast lines. The same values in lysates of a control lymphoblast line were 17 mumol/l and 0.23 mmol/l, respectively. Mevalonate kinase activity in extracts of cultured fibroblasts derived from 6 control individuals was 3.24 +/- (SD) 0.91 nmol/min/mg protein. The activity in extracts of fibroblasts derived from a patient with mevalonic aciduria was 0.15 +/- 0.10 nmol/min/mg protein, approximately 5% of the control mean. The parents and brother of the patient displayed mevalonate kinase activities in fibroblast extracts approximating 38-42% of the control mean. Substantially higher mevalonate kinase activity was documented in extracts of cultured lymphoblasts. When assayed on various occasions, the mean activity of mevalonate kinase in extracts of lymphoblasts derived from the parents, brother and maternal grandmother of the patient ranged from 27 to 32% of the mean activity of 9.8 +/- (SD) 3.4 nmol/min/mg protein measured in a parallel control lymphoblast line, while the mean activity in a maternal and paternal uncle approximated 65-89% of the same control mean. The mean activity in extracts of lymphoblasts derived from the patient approximated 2% of the control mean. The data suggest that the parents, brother and maternal grandmother are carriers of the defective gene responsible for mevalonate kinase deficiency, consistent with an autosomal recessive mode of inheritance.     

The separation of adenine and hypoxanthine-guanine phosphoribosyl transferases isoenzymes by disc gel electrophoresis

Hypoxanthine-guanine (HGPRT; E.C. 2.4.2.8) and adenine (APRT; E.C. 2.4.2.7) phosphoribosyl transferases were studied by disc electrophoresis on polyacrylamide gel. The positions of the isoenzymes were detected by radiochemical enzyme assay. The nucleotide products of the reactions were precipitated in the gel with lanthanum chloride. APRT was found to migrate slightly less rapidly than albumin and produced a single narrow symmetrical peak of activity. HGPRT migrated 25–50% more slowly than albumin and produced a broad zone of activity consisting of four unequal peaks. The APRT enzyme of Rhesus monkey liver and the HGPRT enzyme of sheep erythrocytes migrated notably slower than the corresponding human enzymes. An isoenzyme of APRT was detected in human erythrocytes which migrated more rapidly than that of most individuals. In all instances, the adenine was utilized by one electrophoretic component and hypoxanthine and guanine by another. Furthermore, the components which utilized hypoxanthine and guanine were inseparable. The sensitivity of the assay made it possible to assess the electrophoretic and enzymatic characteristics of HGPRT isoenzymes on aliquots of hemolysates capable of producing 0.5 picomoles of IMP per minute. In human erythrocytes with normal enzyme content, this amount of activity is present in approximately 50 nanoliters of cells.Aided by U.S. Public Health Service grants Nos. HD 04608 and HD 03015 from the National Institute of Child Health and Human Development, National Institutes of Health.     

Retinoblastoma--genetic insights into neoplasia

Retinoblastoma is a highly malignant ocular tumor that has been known to be hereditary in some instances. New information from cytogenetic and molecular studies indicates that there is a retinoblastoma gene and that the mutant alleles are recessive. The wild-type gene appears to be a suppressor of this neoplasia, and, when both alleles are lost, malignancy develops.     

Improvement in in?vitro fertilization outcome following in?vivo synchronization of oocyte maturation in mice

Synchronization of oocyte maturation in vitro has been shown to produce higher in vitro fertilization (IVF) rates than those observed in oocytes matured in vitro without synchronization. However, the increased IVF rates never exceeded those observed in oocytes matured in vivo without synchronization. This study was therefore designed to define the effect of in vivo synchronization of oocyte maturation on IVF rates. Mice were superovulated and orally treated with 7.5 mg cilostazol (CLZ), a phosphodiesterase 3A (PDE3A) inhibitor, to induce ovulation of immature oocytes at different stages depending on frequency and time of administration of CLZ. Mice treated with CLZ ovulated germinal vesicle (GV) or metaphase I (MI) oocytes that underwent maturation in vitro or in vivo (i.e. in the oviduct) followed by IVF. Superovulated control mice ovulated mature oocytes that underwent IVF directly upon collection. Ovulated MI oocytes matured in vitro or in vivo had similar maturation rates but significantly higher IVF rates, 2–4 cell embryos, than those observed in control oocytes. Ovulated GV oocytes matured in vitro showed similar maturation rates but significantly higher IVF rates than those observed in control oocytes. However, ovulated GV oocytes matured in vivo had significantly lower IVF rates than those noted in control oocytes. It is concluded that CLZ is able to synchronize oocyte maturation and improve IVF rates in superovulated mice. CLZ may be capable of showing similar effects in humans, especially since temporal arrest of human oocyte maturation with other PDE3A inhibitors in vitro was found to improve oocyte competence level. The capability of a clinically approved PDE3A inhibitor to improve oocyte fertilization rates in mice at doses extrapolated from human therapeutic doses suggests the potential scenario of the inclusion of CLZ in superovulation programs. This may improve IVF outcomes in infertile patients.     

Inborn errors of GABA metabolism

Defects in man in four steps of 4-aminobutyric acid (GABA) metabolism may interefere with the function of this major inhibitory neurotransmitter. Glutamic acid decarboxylase, 4-aminobutyric acid aminotransferase, succinic semialdehyde dehydrogenase, and homocarnosinase are closely identified with the brain, but two of these enzymes are expressed in cultured peripheral cells, which may permit novel approaches to the study of the metabolism and regulation of GABA.