Epidermal cellular proliferation and differentiation in sexually mature male Salmo salar with androgen levels depressed by oil

Sexually mature male Salmo salar exhibit epidermal thickening and an increase in goblet cell concentration during the spawning season. The ventral skin, which is likely to experience most abrasive contact during the spawning period, has the thickest epidermis and the greatest goblet cell concentration. Following exposure to crude oil there is inhibition of cellular proliferation and elongation associated with epidermal thickening, and also inhibition of mucigenesis. Data on the androgen levels in these fish, and data from earlier studies involving treatment with hormones, indicate that oil-related epidermal effects during the spawning period are most likely systemic in origin, probably arising from reduced plasmatic androgen levels.     

Immobilization of enzymes in porous supports: Effects of support-enzyme solution contacting

Proteins have been immobilized in porous support particles held in a fixed-bed reactor through which protein solution is continuously circulated. Changing the recirculation flow rate alters the observed immobilization kinetics and the maximum enzyme loading which can be achieved for glucose oxidase and glucoamylase on carbodiimide-treated activated carbon and for glucoamylase immobilized on CNBr-Sepharose 4B. Direct microscopic examination of FITC-labelled protein in sectioned Sepharose particles and indirect activity-loading studies with activated carbon-enzyme conjugates all indicate that immobilized enzyme is increasingly localized near the outer surface of the support particles at larger recirculation flow rates. Restricted diffusion of enzymes may be implicated in this phenomenon. These contacting effects may be significant considerations in the scaleup of processes for protein impregnation in porous supports, since apparent activity and stability of the final preparation depend on internal protein distribution.     

Seasonal changes in photosynthetic activity of snow tussocks (Chionochloa spp.) along an altitudinal gradient in Otago,New Zealand

Summary Photosynthetic characteristics were studied in Chionochloa rigida, an altitudinally widespread snow tussock and a closely related high-altitude species C. macra. Along a gradient from near sea level to 1600 m there were no consistent differences in maximum photosynthetic capacity which averaged 4.5 mol CO₂ m^-2s^-1. The photosynthetic temperature optimum ranged between 15 and 18°C and there was only a limited capacity for seasonal adjustment. Net photosynthesis was light-saturated at about 500 mol photons m^-2s^-1. In winter, the photosynthetic capacity decreased significantly with increasing altitude of origin of the snow tussocks. A transplant experiment indicated this was partly genetically controlled.     

Neuroendocrine and behavioral effects of m-chlorophenylpiperazine administration in rhesus monkeys

The effects of m-chlorophenylpiperazine (mCPP), a serotonin receptor agonist, on the release of plasma prolactin (PRL), growth hormone (GH), and cortisol in the rhesus monkey were studied. mCPP was administered intravenously at doses of 0.5, 1.5, and 3.0 mg/kg. GH and cortisol were increased significantly at all doses whike PRL was significantly increased only following administration of 3.0 mg/kg mCPP. mCPP administration also produced behavioral alterations in each monkey, including sedation, penile erection, and defecation. PRL, GH and behavioral responses to mCPP were completely blocked by pretreatment with the serotonin anatgonist metergoline (MTG). However, pretreatment with MTG failed to entirely antagonize the cortisol response to mCPP. These data suggest that mCPP has prominent neuroendocrine and behavioral effects which are mediated, in part, by serotonergic mechanisms.     

Analysis of the kinetics of phospholipid activation of cobra venom phospholipase A2

A kinetic analysis of the "dual phospholipid model" for cobra venom phospholipase A2 (Hendrickson, H. S., and Dennis, E. A. (1984) J. Biol. Chem. 259, 5734-5739) was applied to the activation of phospholipase A2-catalyzed hydrolysis of a thiol ester analog of phosphatidylethanolamine (thio - PE) in Triton X - 100/phospholipid mixed micelles by various phosphorylcholine-containing activators. Activation of thio-PE hydrolysis by didecanoylphosphatidylcholine (PC) was found to be a function of the surface concentration of activator rather than bulk concentration. Its presence did not affect the initial binding of enzyme to phospholipid in the micelle surface as determined kinetically. After initial binding of enzyme to the surface, the activation appears to be due to enzyme-lipid binding in the surface. Activation does not appear to affect the affinity of the enzyme for phospholipid substrate, but rather affects the catalytic efficiency of the enzyme as characterized by the value of Vmax. The monomeric phospholipid dibutyryl-PC, when used as an activator at 57 mM (bulk concentration), also showed effects of surface dilution with Triton X-100, which would not be expected unless the lipid is incorporated into the micelles to some extent at these high concentrations. A thiol ester analog of phosphatidylcholine, thio-PC, was less effective than didecanoyl-PC as an activator, but appeared to be more effective than decylphosphorylcholine. A conformational change of the enzyme upon binding of the activator, after enzyme is bound to substrate at the interface, is discussed as a possible mechanism for this activation.     

Knob heterochromatin homology in maize and its relatives

Summary We have characterised the major DNA sequence component of knob heterochromatin in maize, teosinte andTripsacum. Sequence analysis of this DNA gives strong support to the proposal that maize originated by selection of variants in teosinte. In situ hybridization has confirmed that this repeating DNA sequence, which is the major component of maize knob heterochromatin, is also the major component of knobs in teosinte,Zea diploperennis andTripsacum. In Southern blot hybridizations the repeat has a similar basic organization in all taxa;Tripsacum, however, is differentiated from maize and teosinte by a number of sequence features. Maize and teosinte knob heterochromatin are indistinguishable with regard to the distribution of mutations in the 180-bp repeat and the presence and organization of a 202-bp variant sequence. The knob DNA sequence was not detectable in three species ofCoix, an Old World genus of the Maydeae.Within the repeat unit is a 27-bp region that shows no sequence changes in maize, teosinte orTripsacum. The remainder of the repeat unit has randomly distributed nucleotide changes. The presence of the conserved sequence region suggests that knob DNA may have a functional role in the nucleus.