Effect of Testosterone on Neuronal Morphology and Neuritic Growth of Fetal Lamb Hypothalamus-Preoptic Area and Cerebral Cortex in Primary Culture

Testosterone plays an essential role in sexual differentiation of the male sheep brain. The ovine sexually dimorphic nucleus (oSDN), is 2 to 3 times larger in males than in females, and this sex difference is under the control of testosterone. The effect of testosterone on oSDN volume may result from enhanced expansion of soma areas and/or dendritic fields. To test this hypothesis, cells derived from the hypothalamus-preoptic area (HPOA) and cerebral cortex (CTX) of lamb fetuses were grown in primary culture to examine the direct morphological effects of testosterone on these cellular components. We found that within two days of plating, neurons derived from both the HPOA and CTX extend neuritic processes and express androgen receptors and aromatase immunoreactivity. Both treated and control neurites continue to grow and branch with increasing time in culture. Treatment with testosterone (10 nM) for 3 days significantly (P < 0.05) increased both total neurite outgrowth (35%) and soma size (8%) in the HPOA and outgrowth (21%) and number of branch points (33%) in the CTX. These findings indicate that testosterone-induced somal enlargement and neurite outgrowth in fetal lamb neurons may contribute to the development of a fully masculine sheep brain.     

Analysis of Cyanothece sp. BH68K mutants defective in aerobic nitrogen fixation

The unicellular cyanobacterium, Cyanothece sp. BH68K, is capable of performing both oxygen-sensitive nitrogen fixation and oxygenic photosynthesis within a single cell. To understand the oxygen protection mechanisms of nitrogenase, mutants defective in nitrogen fixation (Nif^-) were isolated by use of diethyl sulfate as a mutagen. Out of 24 mutants screened, 6 mutants could not express nitrogenase activity under aerobic conditions, but expressed activity under anaerobic conditions (Fox^-); 4 mutants showed no activity under both aerobic and anaerobic conditions (Fix^-); and the remaining mutants were impaired in both aerobic and anaerobic nitrogenase activity (Imp). Respiratory oxygen consumption and photosynthetic oxygen evolution were analyzed in the wild-type and in two Fox^- mutants. In the wild-type the appearance of high aerobic nitrogenase activity was correlated with an increase in dark respiration, whereas no such increase was seen in the Fox^- mutants. We propose that in Fox^- mutants, respiratory oxygen consumption plays an important role in maintaining aerobic nitrogenase activity.     

Auxin-regulated changes in protein phosphorylation in pea epicotyls

Auxins regulate various aspects of plant growth and development. However, the mechanism by which these hormones elicit diverse physiological processes is not clear. We present evidence for the role of auxin in protein phosphorylation and the possible involvement of calmodulin in auxin-induced changes. In the presence of auxin, phosphorylation of 23,000, 82,000, 105,000 and 110,000 molecular weight polypeptides markedly decreased whereas phosphorylation of 19,000, 24,000 and 28,000 molecular weight polypeptides increased. These results open up a new experimental approach in understanding the molecular mechanism by which auxins regulate various physiological processes in plants.     

Activation of the abl oncogene and its involvement in chromosomal translocations in human leukemia

Activation of the abl gene and its involvement in human leukemia is one of the most thoroughly characterized examples of the structural alterations of chromosomes associated with the conversion of a normal cell into a cancer cell. The abl oncogene as first identified on the Abelson murine leukemia virus (A-MuLV). Activation of the viral oncogene is associated, in part, with the truncation of the gene at its 5' end. As in studies with other retroviruses, results with A-MuLV presaged the mechanism of activation by abl in naturally occurring human malignancies. Thus, chronic myelogenous leukemia (CML) is consistently associated with a translocation of a piece of chromosome 9 onto chromosome 22 creating what is known as the Philadelphia chromosome (Ph1). The result of this translocation is the truncation of the 5' end of the cellular abl gene, which is located at the breakpoint of chromosome 9. The function of the abl gene product is poorly understood but is thought to participate in an, as yet, undefined pathway of growth control signals, which originate outside the cell, and traverse through the cell into its nucleus. The loss of the gene product's N-terminal amino acid sequences brought about by the truncation of the 5' portion of the gene is consistent with the hypothesis that the protein's growth-controlling activity is deregulated by the structural alterations which occur in the cancer cells. The abl gene and CML serve as a paradigm of the mechanism of activation of proto-oncogenes by chromosomal alterations. The case of CML and the Ph1 chromosome illustrates the findings we might expect as other chromosomal abnormalities are characterized at the molecular level.     

Effect of a new non-steroidal anti-inflammatory agent on lysosomal stability in adjuvant induced arthritis

The effect of new non-steroidal anti-inflammatory agents on lysosomal stability was studied by determining the activity of beta-glucuronidase, a typical lysosomal enzyme, in various sub-cellular fractions and its release from the lysosome-rich fraction. Adjuvant arthritic animals showed a significant increase in the beta-glucuronidase activity in sub-cellular fractions. The increased rate of the release of beta-glucuronidase from lysosome-rich fraction clearly suggested that arthritic syndrome caused decreased stability of the lysosomes. Administration of boswellic acids or salai-guggal to arthritic animals was found to increase the lysosomal stability by inhibiting the rate of release from lysosome-rich fraction and reducing beta-glucuronidase activity in various sub-cellular fractions. Of the two anti-inflammatory agents tested, salai-guggal was found to afford more therapeutic value than boswellic acids.     

Trees on networks: resolving statistical patterns of phylogenetic similarities among interacting proteins

Background  

Phylogenies capture the evolutionary ancestry linking extant species. Correlations and similarities among a set of species are mediated by and need to be understood in terms of the phylogenic tree. In a similar way it has been argued that biological networks also induce correlations among sets of interacting genes or their protein products.     

Redifferentiation and subsequent dedifferentiation of the livers of roosters resulting from acute estrogen challenges

1. Histologic and metabolic changes take place in livers of rooster receiving challenges consisting of acute doses of estrone. 2. During initial Growth and Redifferentiation livers rapidly increase in size by division of hepatocytes within most lobules, changing from cordlike to acinar configurations. 3. No new lobules appear and degeneration of some cells within lobules takes place even as cell divisions predominate. 4. Cells within lobules assume secretory features. 5. Vitellogenins, very low density lipoproteins, calcium and alkaline phosphatase increase greatly in plasma. 6. Within 35-40 days of cessation of estrogen, livers have returned to near normal sizes and plasmas exhibit normal parameters.