Proteins synthesized by inducer T cells: evidence for a mitogenic peptide shared by inducer molecules that stimulate different cell types

Inducer T lymphocytes synthesize and secrete peptides that stimulate growth and differentiation of many cell types, including lymphocytes and monocytes that kill foreign organisms, B lymphocytes, mast cells and hematopoietic precursor cells. To define these inducer molecules more precisely, we have generated clones of these T cells as a source of homogeneous material for biochemical analysis. These clones synthesize peptides that stimulate T and B cells to divide and that also induce the latter cells to secrete immunoglobulin. Inducer cells synthesize a 14 kilodalton growth polypeptide that stimulates T and B lymphocytes, as well as other cell types, to divide. This 14 kilodalton peptide is normally associated with different, larger peptides that appear to focus its mitogenic activity to one or another target cell.     

Incorporation of3H-thymidine into DNA and the activity of alkaline phosphatase in zinc-deficient fetal rat brains

The incorporation of³H-thymidine into DNA in the brains of the 17-day and 20-day old rat fetuses was significantly reduced by maternal zinc restriction during pregnancy. The activity of the enzyme thymidine kinase (EC 2.7.1.21) was similarly reduced in the zine-deprived fetal brains on days 14 and 20 of gestation, but not on day 17. Fetal brain alkaline phosphatase (EC 3.1.3.1) was significantly depressed by maternal zinc deprivation on days 17 and 20 of pregnancy. The data suggest an association between thymidine kinase and the reduced incorporation of³H-thymidine into DNA in the brains of 20-day old fetuses but not in animals on day 17. Alkaline phosphatase was however depressed at this stage. The suggestion is made that because of the complexity of brain development, future biochemical studies in this area should concern specific structures in the brain at particular critical stages during neurogenesis.     

Formaldehyde-induced appearance of septate junctions between digestive vacuoles

Tissue biopsies from (1) some chronic inflammatory diseases, (2) a necrotic tumoral process, (3) normal human lymphatic ganglia, and (4) two congenital diseases of the adrenal cortex were selected for study. A block from each biopsy was fixed in glutaraldehyde-paraformaldehyde; a second block was fixed in 10% formaldehyde. In all cases septate junctions between digestive vacuoles did occur in phagocytic cells and some adrenal cortex cells fixed in formaldehyde. These junctions were similar to those reported recently for malakoplakia phagocytes. Consistently, they were not found to attach organelles other than lysosomes derivatives. Both phagocytes and adrenal cortex cells in the material fixed in glutaraldehyde-paraformaldehyde did not display adhesive specializations between digestive vacuoles. This suggests that the septate junctions described herein are artifactuous structures induced by formaldehyde. There is, however, a certain degree of specificity of cells having the capability of developing these septate junctions. It is assumed that the coating material of digestive organelles in phogocytes and some other cells would be responsible for both cell specificity and organelle specificity of the formaldehyde-induced septate junctions.     

Temperature regulation in a hypometabolic primate, the slow loris (Nycticebus coucang).

Six slow loris were exposed to air temperatures between 10 degrees C and 40 degrees C. Rectal temperature was stable (mean, 34.8 degrees C) at air temperatures between 17 degrees C and 31 degrees C; at higher air temperatures, the animals became hyperthermic. Oxygen consumption was minimal at air temperatures of 31.4-36.6 degrees C; the mean value (0.250 ml O2 g-1 h-1) was only 36% of the expected level for a eutherian Mammal. The slow loris increased its heat production at lower air temperatures. Thermal polypnea occurred in response to heat, and some of the animals were able to dissipate their entire metabolic heat production at lower air temperatures. Thermal polypnea occurred in response to heat, and some of the animals were able the combined thermal conductance of the tissues and haircoat was 73% of the predicted values. It was concluded that, in spite of its low metabolic rate, the slow loris had effective responses to moderate cold, and that, in addition, it was well adapted to a hot climate.     

Oviposition and development of Drosophila modified by magnetic fields

Drosophila flies placed in a habitat with two lateral boxes demonstrated sensitivity to magnetic fields: Oviposition decreased by exposure to pulsated extremely low frequency (ELF) (100)Hz, 1.76 miliTesla (mT) and sinusosidal fields (50 Hz, 1 mT), while there was no initial effect of exposure to a static magnetic field (4.5 mT). Drosophila eggs treated for 48 h with the above described fields showed that (1) mortality of eggs was lower in controls than in eggs exposed to all tested magnetic fields; (2) mortality of larvae increased when a permanent magnet was used; (3) mortality of pupae was highest when a permanent magnet was used; and (4) general adult viability was highest in controls (67%) and diminished progressively when eggs were exposed to pulsated (55%), sinusoidal (45%), and static (35%) magnetic fields.     

SE- and SW-migrating Blackcap (Sylvia atricapilla) populations in Central Europe: Orientation of birds in the contact zone

In the Blackcap (Aves: Sylvia atricapilla), a widespread passerine noctural migrant, a “migratory divide” between SE- and SW-migrating populations exists in Central Europe at about 14° E and south of 52° N. The autumn migratory directions are known to have a genetic basis and are expressed in orientation cages in captivity. Migratory directions of birds in the contact zone between the two populations were studied by analysing ringing data and by testing three groups of hand-raised individuals in orientation cages. Available ringing data are insufficient to establish migratory directions in the contact zone north of the Alps. Hand-raised birds from south-west Germany and the most eastern part of Austria oriented SW and SE, respectively, confirming directions known from ringing recoveries. A sample of birds from the contact zone near Linz (Austria) oriented SW to NW (mean = 268°) and was significantly different from both adjoining populations. This contrasts with results of a cross-breeding experiment with mixed pairs of SW- and SE-migrants bred in captivity: The F1-offspring chose southerly directions, intermediate between both parental populations (Helbig, 1991). It is suggested, therefore, that a distinct subpopulation with a large fraction of birds wintering in the British Isles has established itself in the contact zone. Differences in directional choices between groups of siblings from this area indicate that intrapopulation genetic variability is present. This may have led to a rapid spread of the novel W-NW migratory direction, because north of the Alps strong selection seems to be acting against mixing of SE- with SW-migrating populations.