Effect of a melatonin implant on the circadian variation of plasma prolactin and rectal temperature in newborn sheep.

Plasma prolactin and rectal temperature show a circadian rhythm in newborn sheep raised under continuous light. Melatonin lowers the concentration of plasma prolactin but it is not known if it affects its circadian rhythm. To detect whether melatonin acts on the circadian system we studied the effect of a subcutaneous melatonin implant in the circadian rhythms of prolactin and rectal temperature in newborn lambs raised under continuous light. We placed catheters in the pedal artery and vein in 9 newborn lambs (2-5 days of age). A subcutaneous melatonin implant was placed in 4 of the lambs at 9-12 days of age. Blood samples and rectal temperature measurements were obtained hourly for a period of 24 h, 11-15 days after the implant, at 20-27 days of age. To avoid interferences of heparin in our melatonin assay, serum melatonin concentration was measured before and during the implant in three additional newborns. Prolactin and melatonin were measured by RIA. Melatonin concentrations were 52.8 +/- 45.9 pg/ml (day) and 315.5 +/- 77.0 pg/ml (night) before treatment (SEM, P less than 0.001), and increased to 594.1 +/- 54.5 pg/ml after placing the implant (there was no difference in melatonin concentration between day and night during the time that the implant was in place). Melatonin had no effect on rectal temperature or its rhythm, but decreased basal plasma prolactin concentration (control: 97.5 +/- 11.3 ng/ml; treated: 25.1 +/- 2.4 ng/ml, P less than 0.001) and abolished the prolactin circadian rhythm, (Cosinor analysis): control: log prolactin (ng/ml) = 1.8 + 0.26 cos 15 (t - 11.16), p = 0.05; treated: log prolactin (ng/ml) = 1.2 + 0.14 cos 15 (t - 9.43), P = 0.36.     

Adherence to epithelial cells and ultrastructure of fosfomycin-resistant mutants of group A streptococci

Adherence of three strains of group A streptococci and their fosfomycin-resistant mutants to HEp-2 tissue culture cells was compared with some cell-surface characteristics, i.e. ultrastructure and hydrophobicity. Among Fosr mutants, both well-adhering and weakly adhering mutants were found. Clonal analysis of the mutants proved their greater stability in the adherence. Well-adhering parent strains of streptococci and Fosr mutants exhibited surface fibrillae in contrast to weakly adhering Fosr mutants which were devoid of fibrillae or contined fibrillae of lower electron density. Decrease of adherence of Fosr mutants of two strains was accompanied by a decrease of their hydrophobicity.     

Leaf water potential and leaf conductance during the growing season in almond trees under different irrigation regimes

Seasonal changes in leaf water potential (Φ) and leaf conductance (g₁) were determined in almond trees under different irrigation regimes. The development of water stress in the rainfed treatment induced a specific seasonal dynamics of Φ values and an important reduction in g₁ values. A decrease in g₁ values occurred independently of the irrigation treatment through the growing season. No statistically significant differences were obtained in g₁ values within the drip irrigated treatments.     

The adhesin structures involved in the adherence of group B streptococci to human vaginal cells

The adherence of group B streptococci (GBS) of serotypes Ia, II and III to human vaginal cells was studied in vitro. The adherence was not dependent on the viability of bacteria; killing of GBS by UV irradiation or glutaraldehyde treatment did not inhibit the adherence. Killing of GBS by heating to 56 degrees C for 1 h led to a pronounced decrease of adherence, demonstrating the thermosensitivity of the GBS structures involved. The protein nature of these structures was proved by a significant reduction of adherence after pretreatment of GBS with trypsin or pepsin. Pretreatment of GBS with sialidase had no influence on the adherence. Such a pretreatment of vaginal cells caused an increase of adherence showing that the receptors on epithelial cells may be partly masked by sialic acid.     

Glutamicin CBII,a bacteriocin-like substance produced by

Corynebacterium glutamicum CBII, in the stationary phase of growth, was found to produce spontaneously a substance resembling bacteriocins by its bactericidal properties. This substance designated glutamicin CBII was observed to exhibit bactericidal activity against coryneform bacteria (12 species tested) but not against unrelated gram-positive (3) and gram-negative (3) bacteria, while its action on bacteria with no quite known relatedness to the coryneform group (14) was found to be variable. Glutamicin CBII was partially purified by precipitation with ammonium sulphate (70% saturation), selective heat precipitation and gel chromatography on Sepadex G-50. The antibacterial substance diffused through cellophane membrane with an approximate cut-off of 10000 dalton and its sedimentation coefficient was determined to be 1.1. S by ultracentrifugation. Heating at 100°C for 30 min had no effect on its activity. Glutamicin CBII was proved to be resistant to chloroform, trypsin, chymotrypsin, pronase, and subtilisin. According to its staining behaviour and ¹H NMR spectra it probably represents a glycoprotein containing only a minor protein component.

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Changes in carbohydrate composition in wheat and pea seedlings induced by calcium deficiency

Wheat (Triticum aestivum L. cv Jubilar) seedlings were grown for 10 days in hydroponics with or without calcium. In the leaves, Ca deficiency caused the level of ethanol soluble carbohydrate to increase between 2-and 10-fold, enhanced dark respiration and decreased CO₂ fixation capacity. Sucrose was the major carbohydrate to accumulate in wheat roots.     

Production of microsporidia pathogenic to the Colorado potato beetle (Leptinotarsa decemlineata) in alternate hosts

The microsporida Nosema gastroideae and N. equestris, which are highly pathogenic for Leptinotarsa, have been successfully produced in some other chrysomelid species, Gastrophysa polygoni and G. viridula. As the principal target host, Leptinotarsa is very susceptible to these pathogens, and death occurs before massive sporulation by the microsporidia. By contrast, the infected larvae of G. polygoni or G. viridula are able to develop until the adult stage when most of the tissues become filled with spores. In addition, the larvae and adults of these species can be reared in the laboratory on Polygonum aviculare and Rumex obtusifolius. These plants have longer vegetative periods and are better sources of food than potato leaves. In both species of Gastrophysa the yields of spores related to unit weight were about five times higher than in Leptinotarsa. In the adults of G. viridula there was up to 4.8 × 10⁶ spores mg^?1 body weight of N. gastroideae, or 9.1 × 10⁶ spores mg^?1 of N. equestris. The higher content of microsporidian spores facilitates their purification and isolation.