ISOLATED NERVE ENDINGS (NEUROSECRETOSOMES) FROM THE POSTERIOR PITUITARY : Partial Separation of Vasopressin and Oxytocin and the Isolation of Microvesicles

Subcellular fractions of the bovine posterior pituitary, including one composed almost exclusively of pinched-off nerve endings (neurosecretosomes), were characterized electron microscopically, hormonally, and enzymically. 15% of the nerve terminals in the gland were isolated as neurosecretosomes, as estimated from determinations of lactic dehydrogenase, a soluble, cytoplasmic enzyme. Neurosecretosomes were subdivided into three fractions by density-gradient centrifugation. The three subfractions, each shown to be nearly homogeneous populations of neurosecretosomes by means of electron microscopic and enzymic criteria, differed from each other in their vasopressin/oxytocin (VP/OT) ratios. The VP/OT ratio increased from the lightest to the densest fraction, indicating that VP is localized to denser and OT to lighter neurosecretosomes; similar results have been obtained previously for subfractions of neurosecretory granules (NSG). No morphological differences were apparent in neurosecretosomes among the three subfractions. Although complete separation of VP and OT was not achieved, the findings suggest that VP and OT are each stored in a different species of nerve ending and support the hypothesis that a given neurosecretory cell synthesizes, stores, and secretes only one of the peptide hormones. Microvesicles, 40–80 mµ diameter and contained in typical neurosecretory cell terminals, are believed to be degradation products of membrane ghosts of depleted NSG; electron micrographs indicative of this transformation are presented. A fraction rich in microvesicles, but containing some NSG membranes, was prepared by density-gradient centrifugation of an osmolysate of neurosecretosomes. Smaller, apparently nonneurosecretory nerve endings, lacking NSG but filled with small vesicles, are occasionally seen in sections from whole gland. The vesicles in these atypical posterior pituitary nerve endings may be true neurohumor-containing, "synaptic" vesicles.     

Studies on multiple polyploids inNicotiana

A trispecific hybrid combination ofNicotiana glutinosa-trigonophyllatabacum was successfully colchicine doubled, and multiple polyploids were raised. Chromosome complement was full (96) in most of the plants. Three of the fifteen plants studied showed chromosomal elimination of varying numbers.Six plants showed floral modifications, each of a different type; of these two were associated with chromosome loss, others were attributed to genome-cytoplasm interaction, or to genetic factors.Pollen fertility was good in almost all the plants but no capsule was set on them. On some plants parthenocarpic fruits developed easily and capsules were quickly set when back- or out-crossed.Several quadruple hybrid combinations were obtained and their survival capacity is reported. Difficulties in establishing, and possibilities of successfully utilising the multiple polyploids for breeding work are discussed.An abstract of this paper has been presented at the 3rd Tobacco Research Worker's Conference held at Madras from 13th to 15th September, 1962.     

Effect of Growth Stage and Initial Inoculum Level on Leaf Rust Development and Yield Loss Caused by Puccinia recondita f. sp. tritici

The effects of the combinations of leaf rust inoculation at different growth stages and initial inoculum levels on leaf rust development and yield of winter wheat cultivars, McNair 1003 and Coker 762 were evaluated. Disease onset stage and initial inoculum level affected the rate of leaf rust development and shape of the disease progress curves in both cultivars. Epidemics with common onset stages and different initial inoculum levels differed in area under the disease progress curve (AUDPC). Leaf rust epidemics initiated at Feeke's growth stages 5, 7, and 10 reduced yield in both cultivars. Leaf rust epidemics initiated early with high inoculum levels had the greatest deleterious effect on yield. Maximum losses due to leaf rust were 30–40 %. Yield loss was directly related to AUDPC when the AUDPC varied from 500 to 1700 in McNair 1003 and from 250 to 1700 in Coker 762. Yield reduction was mainly due to reduction in grain weight.     

Transformation of T lymphocytes by the v-fos oncogene

Activation of T lymphocytes through the T cell antigen receptor has been shown to stimulate a rapid and transient accumulation of c-fos mRNA and protein. Transfection of a normal murine T lymphocyte clone with the FBJ-v-fos oncogene resulted in generation of a cell line that was morphologically transformed, had lost the requirement for IL-2 for proliferation, and was tumorigenic in adult syngeneic mice; however, the transformed cells retained the ability to proliferate in response to IL-2. The transformed cells did not show constitutive expression of IL-2 or c-fos mRNA, although the promoter regions of both IL-2 and c-fos genes contain AP-1 sites that are expected to be targets for binding of Fos/Jun complexes. In contrast, the transformed T cells showed increased constitutive expression of IL-2R alpha and c-myc mRNA; these genes may represent cellular targets for transformation by v-fos and physiologic activation by c-fos. We discuss the possibility that these transformed cells behave as cells partially activated through the TCR, and that transformation occurs through a mechanism independent of IL-2.