DIVISION IN THE DINOFLAGELLATE GYRODINIUM COHNII (SCHILLER) : A New Type of Nuclear Reproduction

Dinoflagellates are of interest because their chromosomes resemble the nucleoplasm of prokaryotes both chemically and ultrastructurally. We have studied nuclear division in the dinoflagellate Gyrodinium cohnii (Schiller), using cells obtained from cultures undergoing phasic growth. Electron micrographs of serial sections were used to prepare three-dimensional reconstructions of nuclei and chromosomes at various stages of nuclear division. During division, a complex process of invagination of the intact nuclear envelope takes place at one side of the nucleus and results in the formation of parallel cylindrical cytoplasmic channels through the nucleus. These invaginations contain bundles of microtubules, and each of the bundles comes to lie in the cytoplasm of a cylindrical channel. Nuclear constriction occurs perpendicular to these channels without displacement of the microtubules. There are no associations between chromosomes and the cytoplasmic microtubules. In dividing cells most chromosomes become V-shaped, and the apices of the V's make contact with the membrane surrounding cytoplasmic channels. It is proposed that the membrane surrounding cytoplasmic channels in the dividing nucleus may be involved in the separation of daughter chromosomes. Thus, dinoflagellates may resemble prokaryotes in the manner of genophore separation as well as in genophore chemistry and ultrastructure.     

Comparison of two serologically distinct ribonucleic acid bacteriophages. II. Properties of the nucleic acids and coat proteins

Overby, L. R. (University of Illinois, Urbana), G. H. Barlow, R. H. Doi, Monique Jacob, and S. Spiegelman. Comparison of two serologically distinct ribonucleic acid bacteriophages. II. Properties of the nucleic acids and coat proteins. J. Bacteriol. 92:739-745. 1966.-The ribonucleic acid (RNA) molecules and coat proteins of two RNA coliphages, MS-2 and Qbeta, have been characterized. MS-2 RNA shows an S(20,w) of 25.8 and a molecular weight by light scattering of 10(6). The corresponding parameters for Qbeta-RNA were 28.9 and 0.9 x 10(6). A difference in base composition was reflected in the adenine-uracil ratio, which was 0.95 for MS-2 and 0.75 for Qbeta. The two RNA preparations are readily separated by chromatography on columns of methylated albumin. Both gave identical bouyant densities in cesium sulfate of 1.64 g/ml. The coat protein subunits were of similar molecular weights: 15,500 (Qbeta) and 14,000 (MS-2). They differed, however, in that the Qbeta-protein lacked tryptophan and histidine, whereas the MS-2 protein lacked only histidine.     

Induction of c-fos mRNA Expression by Afterdischarge in the Hippocampus of Naive and Kindled Rats

Periodic induction of focal electrical seizure [afterdischarge (AD)] is an absolute prerequisite for the development of kindling, an animal model of complex partial epilepsy. Once established, it is a permanent condition. The mechanism(s) that translate ADs, which last tens of seconds, into life-long alterations in the CNS is unclear. Cellular immediate-early genes have been implicated in the conversion of short-term stimuli to long-term alterations in cellular phenotypes by regulating target gene expression. We have investigated the contribution of one such early gene, c-fos, to this process. The relationship between ADs and expression of c-fos gene in the rat hippocampus, a key structure in kindling development, was studied by analysis of mRNA levels. The low constitutive expression of c-fos mRNA in the hippocampus was not altered by kindling. There was an "all-or-none" relationship between induction of c-fos and the duration of AD. The threshold for induction was approximately 30 s of AD. Above-threshold ADs induced c-fos in both naive and kindled animals to the same extent and with identical temporal profiles. Although the expression of c-fos is unchanged with kindling, c-fos may nonetheless contribute to many long-term changes of kindling, both adaptive and epileptogenic.     

Physical mapping of the von Recklinghausen neurofibromatosis region on chromosome 17

The von Recklinghausen neurofibromatosis (NF1) locus has been linked to chromosome 17, and recent linkage analyses place the gene on the proximal long arm. NF1 probably resides in 17q11.2, since two unrelated NF1 patients have been identified who possess constitutional reciprocal translocations involving 17q11.2 with chromosomes 1 and 22. We have used a somatic-cell hybrid from the t(17;22) individual, along with other hybrid cell lines, to order probes around the NF1 locus. An additional probe, 17L1, has been isolated from a NotI linking library made from flow-sorted chromosome 17 material and has been mapped to a region immediately proximal to the translocation breakpoint. While neither NF1 translocation breakpoint has yet been identified by pulse-field gel analysis, an overlap between two probes, EW206 and EW207, has been detected. Furthermore, we have identified the breakpoint in a non-NF1 translocation, SP-3, on the proximal side of the NF1 locus. This breakpoint has been helpful in creating a 1,000-kb pulsed-field map, which includes the closely linked NF1 probes HHH202 and TH17.19. The combined somatic-cell hybrid and pulsed-field gel analysis we report here favors the probe order D17Z1-HHH202-TH17.19-CRYB1-17L1-NF1- (EW206, EW207, EW203, L581, L946)-(ERBB2, ERBA1). The agreement in probe ordering between linkage analysis and physical mapping is excellent, and the availability of translocation breakpoints in NF1 should now greatly assist the cloning of this locus.     

Adrenal glucocorticoids regulate adipsin gene expression in genetically obese mice

Adipsin expression at the protein and mRNA levels is greatly reduced in several distinct syndromes of obesity in the mouse: genetic obesity due to the db/db and ob/ob genes, and a chemically induced model secondary to neonatal exposure to monosodium glutamate. We considered first the possibility that the adipsin gene might be identical to the db or ob locus and the lowered expression of this protein might result from a mutation in this gene. We show here that the adipsin structural gene is located on chromosome 10 and hence is physically distinct from any obesity genes so far identified in the mouse. A major role for the adrenal gland and adrenal glucocorticoids in the aberrant regulation of adipsin in these models of obesity is indicated by several experiments. Adrenalectomy of the ob/ob mouse raises the circulating levels of adipsin protein and the amount of this mRNA in epididymal fat pads (5-fold), although neither is increased to the levels seen in lean controls. Exogenous administration of corticosterone completely blocks the effects of adrenalectomy on adipsin, suggesting that the effect of this endocrine ablation is through reduction of adrenal glucocorticoids. Corticosterone administration also causes suppression in the levels of adipsin mRNA and protein in lean mice, although this decrease is never as severe as that seen in obese mice. The effect of exogenous corticosterone in lean mice occurs within 2 days and hence is not secondary to the obesity which these hormones eventually elicit. These results indicate that glucocorticoids can regulate adipsin expression in vivo and strongly suggest that the hyperglucocorticoid state seen in certain obese models plays a significant role in lowering adipsin mRNA and protein levels. Quantitative analysis of these experiments suggests that other as yet unknown neuroendocrine factors also function to suppress adipsin in obesity.     

Lateral bias in feeding and brachiation inHylobates

Lateralized hand use in gibbons was assessed for both food reaching and leading limb in brachiation. Sex and age effects were found in hand preference for food reaching. Adult females were all very strongly right hand preferent, whereas adult males had no across group consistent preference. Within the female group there was a strong correlation between age and strength of right handedness. When compared in terms of absolute strength of hand preference, females were found to be more strongly lateralized than males. Leading limb preference in brachiation was scored into vocal and non-vocal categories. Three subjects had a shift in preferred leading limb from the non-vocal brachiation condition to the vocal brachiation condition. This shift may be influenced by the arousal effects of species typical vocalization. The results of this study underline the importance of consideration of such factors as sex and age when interpreting behavioral lateralization data. The exploration of laterality in many different response measures is important to the achievement of a complete understanding of behavioral lateralization in primates.     

Application of p-Toluidine in Chromogenic Detection of Catechol and Protocatechuate, Diphenolic Intermediates in Catabolism of Aromatic Compounds

In the presence of p-toluidine and iron, protocatechuate and catechols yield color. Inclusion of p-toluidine in media facilitates the screening of microbial strains for alterations affecting aromatic catabolism. Such strains include mutants affected in the expression of oxygenases and Escherichia coli colonies carrying cloned or subcloned aromatic catabolic genes which encode enzymes giving rise to protocatechuate or catechol. The diphenolic detection system can also be applied to the creation of vectors relying on insertion of cloned DNA into one of the latter marker genes.