Dietary phosphate deprivation increases 1,25-dihyroxyvitamin D3 synthesis in rat kidney in vitro

A sensitive radioreceptor assay has been used to measure in vitro 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) synthesis in vitamin D-replete rats. Incubation of kidney cortical slices with 25-hydroxyvitamin D3 produced a product which co-migrated on high performance liquid chromatography with authentic 1,25(OH)2D3 in two different solvent systems and displaced 1,25(OH)2D3 from its intestinal receptor. In addition, mass spectral analysis of the product produced a mass fragmentation consistent with that of authentic 1,25(OH)2D3. Endogenous renal cortical 1,25(OH)2D3 content in phosphate-deprived rats averaged 1.1 +/- 0.3 pmol/g (n = 11), which was significantly greater than the renal cortical 1,25(OH)2D3 content of age-matched rats eating a normal diet which averaged 0.44 +/- 0.21 pmol/g (n = 8, p less than 0.001). After incubation, net 1,25(OH)2D3 synthesis in renal slices from phosphate-deprived rats averaged 51 pmol/g/h, about 13-fold greater than the mean of 3.8 pmol/g/h observed in renal slices from rats eating the normal diet. These results indicate that the elevated plasma 1,25(OH)2D3 levels observed in rats during dietary phosphate deprivation are due to increased renal synthesis of the hormone.     

Isolation and comparison of two molecular species of the BAL 31 nuclease from Alteromonas espejiana with distinct kinetic properties

The extracellular nuclease from Alteromonas espejiana sp. BAL 31 can be isolated as two distinct proteins, the "fast" (F) and "slow" (S) species, both of which have been purified to homogeneity. The F and S species of the nuclease have molecular weights, respectively, of 109 X 10(3) and 85 X 10(3), and both are single polypeptide chains with an isoelectric pH near 4.2. Both species catalyze the degradation of single-stranded and linear duplex DNAs to 5'-mononucleotides. The degradation of linear duplex DNA occurs through a terminally directed hydrolysis mechanism that results in the removal of nucleotides from both the 3' and 5' ends. Apparent Michaelis constants (Km) have been obtained for the exonuclease activities of both species and for the activity against single-stranded DNA of the S species. The Km for the hydrolysis of single-stranded DNA catalyzed by the F species has not been obtained because the reaction velocity was maximal even at the lowest substrate concentrations accessible in the photometric assay. The ratio of the turnover numbers for the exonuclease activities of the two species indicates that the F species will shorten linear duplex DNA at a rate 27 +/- 5 (S.D.) times faster than an equimolar concentration of the S species in the limit of high substrate concentration, while the corresponding ratio for the activities against single-stranded DNA (1.2 +/- 0.1) shows that the two species are similar with respect to hydrolysis of this substrate. In the limit of high substrate concentrations, the F and S species break phosphodiester bonds in single-stranded DNA at rates 1.3 +/- 0.3 and 33 +/- 2 times those for the exonucleolytic degradation of linear duplex DNA, respectively. It has not been established whether the two species are physically related.     

Desired family size and sex of children in Nigeria

During 1981, sex ratio data and preferences for family size and for combinations and permutations of children were provided by 333 Nigerian students at the University of Ilorin, Ilorin, Nigeria. For the present and parental generations combined, the secondary sex ratio was estimated to be 95.8 males:100 females. In the projected families, preferences for family sizes resulted in an average of 4.88 children per family. The most preferred family consisted of four children--a 2m2f combination in a mfmf order, whereas the second most preferred family consisted of five children--3m2f combination in a mfmfm order. Also expressed was a strong preference for permutations of sexes, resulting in a male child as first-born followed by an alternation of sexes. A greater preference for male children was indicated by the combined sex ratio of 167 males:100 females for the preferred families.     

Centromeric index measurement by slit-scan flow cytometry

We report here the application of slit-scan flow cytometry (SSFCM) in the classification of muntjac, Chinese hamster, and human chromosomes according to centromeric index (CI) and total fluorescence. Chromosomes were isolated from mitotic cells, stained with propidium iodide and processed through the SSFCM where fluorescence profiles were measured. The centromere for each profile was taken as the point of maximum difference between the measured profile and a standard profile having no centromeric dip. The areas under the profile on either side of the centromere were then calculated and the CI was calculated as the ratio of the larger area to the total area under the profile. Relative DNA contents for each chromosome were taken to be proportional to the total fluorescence. Mean CI's for muntjac chromosomes 1, 2, and X + 3 were 0.52, 0.88, and 0.73, respectively; CI's for Chinese hamster M3-1 chromosomes 1, 2, 5, 8, and M2 were 0.53, 0.55, 0.57, 0.77, and 0.86, respectively; and average CI's for chromosome groups 4 + t (X;5), 6 + 7 + Y, 9 + M1, and 10 + 11 were 0.56, 0.82, 0.58, and 0.60, respectively. These results were, on average, within 4.4% of CI measurements made by image cytometry. CI's measured for human chromosomes 9 through 12, were, on average, within 2.0% of those made by image cytometry.     

Alkaloids,coumarins, triterpenes and a flavanone from the root of Zanthoxylum dipetalum

The root bark of Zanthoxylum dipetalum contained the alkaloids canthin-6-one, chelerythrine, nitidine and tembetarine, the pyranocoumarins avicennol and xanthoxyletin, the triterpene lupeol and the flavanoid hesperidin. The MS fragmentation pattern for avicennol is discussed and a tentative structure is proposed for a third coumarin, designated ZD/1. The root wood of the type species and the stem bark of the γ variety contained most of the above compounds plus sitosterol and, in the root wood only, magnoflorine. The chemotaxonomic implications of these findings are briefly discussed.     

The interrelationships of chromosome banding patterns in procyonids, viverrids, and felids.

The Giemsa banding patterns of the chromosomes of 4 species of Procyonidae, 13 of Viverridae, and 6 of Felidae have been studied. The patterns have all been related to the basic felid karyotype. Each procyonid and viverrid has a distinctive karyotype, whereas some felids have indistinguishable karyotypes even when banded. Extensive interfamilial G-banding conservatism has been demonstrated, with many chromosomes being "shared" by all three families. A chromosome identification and karyotyping system for the Carnivora has been devised to facilitate comparison of data from future studies. Phylogenetic implications of the findings have been discussed.     

Transamidase kinetics. Amide formation in the enzymic reactions of thiol esters with amines.

1. Beta-Phenylpropionylthiocholine and N-(5-aminopentyl)-5-dimethylaminonaphthalene-1-sulphonamide (dansylcadaverine) serve as a pair of water-soluble (pH7.5) model substrates for transamidating enzymes. Amide formation could be followed directly through fluorescence measurements by monitoring the continuous extraction of the water-soluble coupling product, N-(beta-phenylpropionyl)dansylcadaverine, into n-heptane. By this procedure, the steady-state kinetics of glutamine-lysine endo-gamma-glutamyltransferase from human plasma (fibrinoligase, thrombin- and Ca2+-activated blood coagulation Factor XII) and from guinea-pig liver (liver transglutaminase) were investigated at 25 degrees C. 2. With beta-phenylpropionylthiocholine as the varied substrate, Lineweaver-Burk plots with various concentrations of dansylcadaverine intercept on the horizontal axis, suggesting that formation of the acyl-enzyme is rate limiting. 3. On the basis of functional normality of active sites, kcat. values of 1.8 s(-1) and 0.9 s(-1) were obtained for the plasma and liver gamma-glutamyltransferase respectively. The two enzymes show identical affinities for the first substrate, beta-phenylpropionylthiocholine, with Ka 4 times 10(-4) M. 4. Utilization of the second substrate, dansylcadaverine, appears to be an order of magnitude more efficient with the liver enzyme. 5. N-(5-Amino-3-thiapentyl)-5-dimethylaminonaphthalene-1-sulphonamide (dansylthiacadaverine) could be used instead of dansylcadaverine in the fluorescent kinetic system. 6. Competitive inhibition by a non-fluorescent amine substrate histamine was also evaluated.     

Extracellular nucleases of Pseudomonas BAL 31. I. Characterization of single strand-specific deoxyriboendonuclease and double-strand deoxyriboexonuclease activities.

The culture medium of Pseudomonas BAL 31 contains endonuclease activities which are highly specific for single-stranged DNA and for the single-stranded or weakly hydrogen-bonded regions in supercoiled closed circular DNA. Exposure of nicked DNA to the culture medium results in cleavage of the strang opposite the sites of preexisting single-strand scissions. At least some of the linear duplex molecules derived by cleavage of supercoiled closed circular molecules contain short single-stranded ends. Single-strand scissions are not introduced into intact, linear duplex DNA or unsupercoiled covalently closed circular DNA. Under these same reaction conditions, 0X174 phage DNA is extensively degraded and PM2 form I DNA is quantitatively converted to PM2 form III linear duplexes. Prolonged exposure of this linear duplex DNA to the concentrated culture medium reveals the presence of a double-strand exonuclease activity that progressively reduces the average length of the linear duplex. These nuclease activities persist at ionic strengths up to 4 M and are not eliminated in the presence of 5% sodium dodecyl sulfate. Calcium and magnesium ion are both required for optimal activity. Although the absence of magnesium ion reduces the activities, the absence of calcium ion irreversibly eliminates all the activities.