Calcium transients in a crustacean motoneuron soma: Detection with arsenazo III

Summary Long lasting action potentials can be triggered in crayfish giant motor neurons by a short depolarizing pulse under different conditions. The concomitant increase in absorbance of the Ca indicator arsenazo III preloaded into the soma, confirms observations suggesting that these potential changes are related to a Ca inward current through the some membrane.     

Tumour necrosis factors alpha and beta inhibit virus replication and synergize with interferons

Tumour necrosis factor (TNF) and lymphotoxin were initially described as tumoricidal proteins that are produced by activated macrophages and lymphocytes, respectively. Since TNF and lymphotoxin are structurally related, bind to the same cell surface receptor and have indistinguishable biological activities, they have been designated as TNF-alpha and TNF-beta, respectively. The multiple activities of these molecules indicate their importance in immunoregulative responses. Here we report that both TNF-alpha and TNF-beta have antiviral activity and synergize with interferons (IFNs) in the induction of resistance to both RNA and DNA virus infection in diverse cell types. These effects of TNFs are not due to the induction of IFN synthesis. Virus-infected cells are selectively killed by TNFs and this activity is accelerated by IFN-gamma. The production of TNFs is induced by viruses, further suggesting the importance of TNFs in the physiological antiviral response.     

Expressed genes, Alu repeats and polymorphisms in cosmids sequenced from chromosome 4p16.3.

The sequences of three cosmids (90 kilobases) from the Huntington's disease region in chromosome 4p16.3 have been determined. A 30,837 base overlap of DNA sequenced from two individuals was found to contain 72 DNA sequence polymorphisms, an average of 2.3 polymorphisms per kilobase (kb). The assembled 58 kb contig contains 62 Alu repeats, and eleven predicted exons representing at least three expressed genes that encode previously unidentified proteins. Each of these genes is associated with a CpG island. The structure of one of the new genes, hda1-1, has been determined by characterizing cDNAs from a placental library. This gene is expressed in a variety of tissues and may encode a novel housekeeping gene.     

Bacterial lysis of cytoplasm of Cosmarium,a green alga

Summary The protoplast of the green alga Cosmarium is lysed by a coccoid bacterium, whereas the cell wall remains intact. Pyrenoids are more resistant to lytic action than the rest of the chloroplast. Different stages of the lysis are described.We thank the Heads of the Botany and Soils Departments for providing laboratory facilities. Thanks are also due to Dr V. R. P. Garg for help in photography.     

Localization of insulin-like growth factor genes to human chromosomes 11 and 12

The insulin-like growth factors IGF-I and IGF-II are required for growth and development. Both are single-chain proteins (of 70 and 67 amino acids respectively) derived from precursors by proteolytic processing. IGF-I may be particularly important in promoting normal stature and IGF-II may be a fetal growth hormone. The IGF proteins are probably synthesized by many normal tissues and by some tumours. The secretion of growth factors by tumours and tumour-derived cell lines suggests that they may act as autocrine regulators of cell proliferation. Because of the possible role of these proteins in growth disorders and cancer, and their sequence homology with insulin, we have determined their chromosomal localization. Using somatic cell hybrids and cloned cDNA probes for these proteins, we have assigned the genes for IGF-I and IGF-II to human chromosomes 12 and 11, respectively. We present evidence that the IGF-II gene is located on the short arm of chromosome 11 with a ras proto-oncogene and the insulin structural gene, and also suggest the existence of a fragment length polymorphism using the IGF-I probe.     

Impaired insulin release in aging rats: Metabolic and ionic events

We investigated the effect of aging on glucose uptake, glucose-induced O₂ consumption, glucose-induced⁴⁵Ca movements, and calmodulin content to elucidate age-related impairment of glucose-induced insulin release in pancreatic islets of Wistar rats. Intact pancreatic islets from old (24-month-old) rats showed impaired glucose-induced insulin release; glucose uptake and O₂ consumption were lower in old than in young (2-month-old) or adult (12-month-old) rats. Moreover,⁴⁵Ca uptake and calmodulin content were decreased in pancreatic islets from older rats, which explained the impairment in glucose-induced insulin release in aging. No major differences between the 3 age groups in glucose-induced⁴⁵Ca efflux in pancreatic islets were observed.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Role of neurotransmitter release and cyclic AMP-dependent membrane phosphorylation in low voltage myocardial automaticity

Low voltage myocardial automaticity (LVA) was investigated by pharmacological modulations of the presynaptic and postsynaptic processes. The sensitivity of LVA both to inhibitor and stimulator of neurotransmitter release suggests its involvement in LVA genesis. Moreover, LVA is blocked by the inhibition of the cyclic AMP system, supporting the participation of the c-AMP-dependent membrane phosphorylation in calcium-mediated cardiac electrogenesis.