Effects of micromolar concentrations of free calcium ions on the reduction of heart mitochondrial NAD(P) by 2-oxoglutarate.

1. The reduction of mitochondrial NAD(P) by 2-oxoglutarate was monitored as a measure of 2-oxoglutarate dehydrogenase activity in its intramitochondrial locale. In the absence of ADP, steady-state reduction of NAD(P) by 0.5 mM-2-oxoglutarate in the presence of 0.5 mM-L-malate was markedly increased by extramitochondrial Ca2+, with 50% activation at pCa 6.58, when the Na+ concentration was 10 mM, the Pi concentration ws 5 mM and the added Mg2+ concentration was 1 mM. Omission of Pi resulted in 50% activation at pCa 6.77; omission of Mg2+ resulted in 50% activation at pCA greater than or equal to 7.3. 2. The activation of 2-oxoglutarate dehydrogenase could be reversed on addition of an excess of EGTA. The rate of inactivation was dependent on the concentration of Na+, with K0.5 2.5 mM, which is consistent with the rate of withdrawal of Ca2+ from the mitochondria being the limiting factor. 3. The steady-state reduction of cytochrome c by 2-oxoglutarate (0.5 mM) also showed a marked dependence on pCa in the absence of ADP; in the presence of an excess of ADP, no such effect of Ca2+ was detectable. 4. Mitochondria from the hearts of senescent rats showed an undiminished rate of dehydrogenase activation by Ca2+ but a rate of inactivation by excess EGTA that was diminished by 40%. Direct studies of Ca2+ egress with Arsenazo III confirmed a decrement in rate with old age. 5. Studies of 2-oxoglutarate dehydrogenase activity as a function of the mitochondrial context of Ca2+, as measured by atomic-absorption spectrophotometry, showed half-maximal activation at a mitochondrial content of 1.0 nmol of Ca2+/mg of protein, and saturation at 3 nmol/mg. 6. These findings support the model advanced by Denton, Richards & Chin [(1978) Biochem. J. 176, 899-906], of a control of the tricarboxylate cycle by intramitochondrial Ca2+, and demonstrate the range of mitochondrial Ca2+ content over which this may occur. In addition, they raise the possibility of a disturbance of this control mechanism in old age.     

Bicyclo[3,2,1]octanoid,neolignans from Aniba simulans

Six bicyclo[3,2,1]octanoid neolignans, isolated from the benzene extract of Aniba simulans Allen (Lauraceae) trunk wood, are shown to derive from two basic structures: 1-allyl-8-hydroxy-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-7-methyl-3-oxobicyclo[3,2,1]octane, substituted by 4-hydroxy, 4-hydroxy-5-methoxy, 4-methoxy or 4,5-dimethoxy groups; and 1-allyl-8-hydroxy-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-7-methyl-4-oxobicyclo[3,2,1]oct-2-ene, substituted by 3-hydroxy or 3-hydroxy-5-methoxy groups. The structural proposals are based on spectral data, interconversions synthesis of a derivative from the known (2R,3S,3aS)-3a-allyl-5-methoxy-2-(3′-methoxy,4′,5′-methylenedioxyphenyl)-3-methyl-2,3,3a,6-tetrahydro-6-oxobenzofuran.     

Nitrogen fixation throughout growth,and varietal differences in nitrogen fixation by the rhizosphere of rice planted in pots

Summary The nitrogen-fixing activity in the rhizospheres of various rices was measured by the acetylene-reduction method throughout plant growth in green-house pots. The activity began to increase 4 weeks after transplanting, increased until heading stage, then decreased. The concentrations of exchangeable ammonium and sugars in the soil were not related to the variation of nitrogen-fixing activity during rice growth.The nitrogen-fixing activities in the rhizospheres of 41 rice varieties in pots were measured to discover varietal differences. Levels of nitrogen fixation were highly correlated with the rices' dry root weight at heading stage.     

CROSS-SECTIONAL ECHOCARDIOGRAPHIC FINDINGS IN VEGETATIVE AORTIC VALVE ENDOCARDITIS

M-mode echocardiograms of two patients with bacterial endocarditis of approximately 4 months' duration showed dense echoes in the area of the aortic valve. In one patient, who had no prior abnormal cardiac findings, the echoes were clearly suggestive of valvular vegetations. The second patient, however, was known to have had aortic valve disease and a systolic murmur for more than a decade; therefore, dense echoes arising from the aortic valve also could have resulted from valvular calcification. In both patients, cross-sectional echocardiography provided important information. In the first patient, retrograde cardiac catheterization was prevented by large and highly mobile masses attached to the aortic cusps that prolapsed into the left ventricular outflow tract during diastole. Aortic valve replacement without further hemodynamic evaluation was recommended. In the second patient, whose blood cultures remained negative after the acute phase of his illness had been treated, cross-sectional echocardiography showed large vegetations on the aortic valve. Intraoperative findings confirmed the echocardiographic interpretation in each case.     

Isolation and identification of β 1 → 2-d-glucans in extracellular polysaccharides of Rhizobium meliloti strain L5-30

Abstract Exopolysaccharides have been found as bound to R. meliloti cells (strain L5-30) or free in the culture medium; they consist of acidic and neutral polysaccharides. Bound and soluble neutral polysaccharides were identified as β 1 → 2 linked glucans with an average M _r value of 4000 to 6000.     

Spatial and temporal gene expression patterns occur during corm development.

We investigated gene expression patterns that occur during taro corm development. Two-dimensional gel electrophoresis identified several different prevalent proteins that accumulate during corm development. Microsequencing studies indicated that some of these proteins are related to taste-modifying proteins, such as curculin and miraculin, and proteins found in other storage organs, such as sporamin and the Kunitz trypsin inhibitor. A curculin-encoding cDNA clone, designated as TC1, was identified that corresponds to a highly prevalent 1-kb corm mRNA. The TC1 mRNA accumulates during corm development, is more prevalent in corm apical than basal regions, and is either absent, or present at low concentrations, in other vegetative organs such as the leaf and root. In situ hybridization experiments showed that the TC1 mRNA is highly concentrated in corm storage parenchyma cells and is absent, or present in reduced concentrations, in other corm cells and tissues. Our results show that corm development is associated with the differentiation of specialized cells and tissues, and that these differentiation events are coupled with the temporal and spatial expression of corm-specific genes.     

Prothymosin alpha is phosphorylated by casein kinase-2.

Prothymosin alpha (ProT alpha) is a 12.5 kDa acidic polypeptide that is considered to have a nuclear function related to cell proliferation. Inspection of its amino acid sequence revealed the presence of sequences that may serve as targets for phosphorylation by casein kinase-2 (CK-2). ProT alpha isolated from calf thymocytes was phosphorylated in vitro by CK-2. The phosphorylation sites are Ser and Thr residues located among the first 14 amino acid residues in the ProT alpha sequence. Another site that is theoretically suitable for phosphorylation by CK-2, at the C-terminus of the polypeptide, is not, in fact, phosphorylated. Thymosin alpha 1 (T alpha 1), a peptide whose sequence corresponds to the first 28 amino acids of ProT alpha, is also phosphorylated by CK-2 at the same phosphorylation sites as ProT alpha. In cultured splenic lymphocytes ProT alpha was phosphorylated at Thr residues located at positions 7, 12 and/or 13. Based on these observations we conclude that CK-2, or another cellular kinase with similar sequence specificity, is responsible for phosphorylation of ProT alpha in vivo.     

Low concentrations of hydrogen sulphide alter monoamine levels in the developing rat central nervous system.

The central nervous system is one of the primary target organs for hydrogen sulphide (H2S) toxicity; however, there are limited data on the neurotoxic effects of low-dose chronic exposure on the developing nervous system. Levels of serotonin and norepinephrine in the developing rat cerebellum and frontal cortex were determined following chronic exposure to 20 and 75 ppm H2S during perinatal development. Both monoamines were altered in rats exposed to 75 ppm H2S compared with controls; serotonin levels were significantly increased at days 14 and 21 postnatal in both brain regions, and norepinephrine levels were significantly increased at days 7, 14, and 21 postnatal in cerebellum and at day 21 in the frontal cortex. Exposure to 20 ppm H2S significantly increased the levels of serotonin in the frontal cortex at day 21, whereas levels of norepinephrine were significantly reduced in the frontal cortex at days 14 and 21, and at day 14 in the cerebellum.     

Effect of corticosteroids on the congenital transmission of experimental toxoplasmosis]

Female white mice with chronic toxoplasmosis were treated with cortisone acetate (3mg for each 25 g of body weight) 12, 8, 4 and 0 days before mating. Cortisone induces congenital transmission of T. gondii.