Localization of serotonin within tanycytes of the rat median eminence

Summary Formaldehyde and glyoxylic acid histochemical methods were employed to examine monoamine fluorescence of the rat median eminence. Tanycytes of the median eminence contained a yellow histofluorescence which was verified with microspectrofluorometry as due to the presence of serotonin. Catecholamine-containing varicosities, arranged in linear profiles throughout the depth of the median eminence, were observed. These linear profiles appeared to follow the contours of serotonin-containing tanycytes. Organculture experiments supported the hypothesis that the serotonin associated with tanycytes is localized within the tanycytes and does not arise from an extrahypothalamic source of nerve terminals. These data provide evidence that a tanycytic catecholamine-indoleamine morphological juxtaposition occurs in a manner reminiscent of that of another circumventricular organ, the pineal.Supported by USPHS Grants NS11642 and AM-19761USPHS Career Development Awardee NS-00259     

Influence of low temperature on phosphatase in roots of Verbascum thapsus,a biennial weed

The temperature peak (15 °C) of acid and alkaline phosphatase in this study coincides with a peak in alpha-amylase as seen in an earlier study of roots of Verbascum thapsus. It is speculated that one of the results of higher phosphatase activities may be increased amount of orthophosphate which can be utilized in phosphorylation of soluble carbohydrates which in turn are in greater supply due to the higher activities of the starch-degrading enzymes.A second peak in activities of acid and alkaline phosphatase was seen in plants which were returned to the greenhouse following cold treatment. This increase in enzymatic activities is also similar to increases in activities of three starch degrading enzymes studied earlier. Alkaline phosphatase showed greater activities than did acid phosphatase at lower temperatures (10 and 4 °C) and under greenhouse conditions following cold treatment.     

Variation in the susceptibility of sockeye salmon Oncorhynchus nerka to infectious haemopoietic necrosis virus

Haemoglobin concentrations, haematocrit values, red blood cell counts, red blood cell diameter, erythrocyte sedimentation rate and plasma haemoglobin concentration were measured on the air-breathing mud eel Amphipnous cuchia .     

The identification of membrane glycocomponents in polyacrylamide gels: A rapid method using I-labeled lectins

A rapid method is described for the identification of lectin binding membrane glycocomponents in polyacrylamide gels. The method requires only small quantities of membrane material and is applicable to a wide variety of lectins. Solubilized membrane components are electrophoretically separated according to molecular weight in a SDS-polyacrylamide gel. The gel is then incubated in a solution containing the ¹²⁵I-lectin. After elution of unbound ¹²⁵I-lectin, the gel is dried down and those bands which have bound the ¹²⁵I-lectin are identified by radioautography. The amount of bound ¹²⁵I-lectin can be quantified by either densitometric scanning of the radioautogram or by liquid scintillation counting of the dried gel.     

Stereoselective action of acylated crude papain toward mandelic and atrolactic hydrazides

Acylated crude papain has been shown to exert stereoselective behavior toward racemic hydrazides devoid of an amino acid residue, namely, (RS)-mandelic and (RS)-atrolactic hydrazides. These hydrazides functioned as nucleophiles to yield N¹,N²-diacylhydrazines. Several achiral acylating agents for the enzyme were chosen, including Z-glycine, BOC-glycine, AOC-glycine, and hippuric acid. With the exception of hippuric acid as the acylating agent, the reaction product, in every instance for these achiral hydrazides, consisted of an excess of the (+)-N¹,N²-diacylhydrazine. The relative rates of product formation for the mandelic hydrazides were considerably greater than for corresponding reactions with racemic atrolactic hydrazide. When chiral Z-l-alanine was employed to acylate crude papain, the stereoselective action was most pronounced, with the formation of a mixture of diastereoisomers consisting of 73% N¹-(Z-l-alanyl)-N²-[(R)-mandelyl]hydrazine. The relative reactivities for the electrophiles was Z-l-alanine ? Z-glycine ? hippuric acid ? AOC-glycine > BOC-glycine. The hydrazides of (R)-, (S)-mandelic, and (RS)-atrolactic acids were prepared by conversion of the corresponding acids to their esters by means of a catalytic dehydrating agent and subsequent treatment with a methanolic solution of hydrazine.     

A steady-state kinetic study on the catalytic mechanism of ribulose bisphosphate carboxylase from soybean

The catalytic mechanism of soybean ribulose bisphosphate carboxylase was examined, through a study of the steady-state kinetic behavior of the fully activated enzyme using short time assays. The effects of substrates, products, alternative products, and two dead-end inhibitors were investigated. High concentrations of both substrates were observed to lead to nonhyperbolic relationships: concentrations of bicarbonate greater than 15 mm inhibited and concentrations of ribulose bisphosphate greater than 0.2–0.5 mm stimulated enzyme activity over that expected from a hyperbolic fit to the data. The kinetic patterns obtained and the nonhyperbolic behavior of substrates are interpreted to suggest that the binding of substrates and the release of products follow a steady-state random mechanism. The substrate activation by ribulose bisphosphate is likely to be physiologically significant.