Histochemical observations on the giant neurosecretory cells of the thoracic ganglion of the adult and juvenile crabs, Potamon magnum magnum (Pretzman).

The giant neurosecretory cells in the thoracic ganglion of the adult and juvenile crab, Potamon magnum magnum (Pretzman) were histochemically investigated. The secretion is mainly proteinaceous in nature, containing considerable amounts of acid mucosubstances, sulphate esters, lipids and a little carbohydrate but no glycogen. The detailed nature of proteinaceous neurosecretory material in the adult crab was further tested. It appears that the neurosecretory material of these cells contains moderate amounts of sulfhydryl groups and few of disulphide bonds. No trace of tyrosine could be observed. The neurosecretory granules were associated with considerable amounts of cytoplasmic RNA. In general, stronger reactions were obtained in summer and winter than in other seasons.     

Analysis of the conformation of polypeptides : the combined use of energy computations and nuclear magnetic resonance studies.

This review surveys current approaches to the problem of determining the solution conformation of polypeptides. The basic principles of energy computations are described. The utility, problems, and limitations of various theoretical methods are summarized: conformational energy mapping, energy minimization, scanning of selected local conformations, statistical predictive schemes. The need for combining the calculations with experimental studies is pointed out. The information content of various physico-chemical methods is compared for this purpose. The analysis of nmr coupling constants is discussed in more detail. In combination with energy computations, it can furnish specific information on local aspects of the conformation. Examples of such combined studies on small peptides are summarized.     

Role of B-lymphocytes in inactivating allogenic stem cells]

Antisera to membrane antigens of B lumphocytes eliminated the capacity of lymphocytes to inactivate allogenous stem cells by 60%; however, lymphocytes from the lymph nodes of B mice possessed no inactivating capacity. T-lymphocytes were the main criteria inactivating allogenous stem cells. Cooperating with T-lymphocytes, B-lymphocytes probably contributed to inactivation of precursor cells realized by T-lymphocytes. However, the presence of B-lymphocytes in the killer cells population was not a determinant, since T-lymphocytes were capable of inactivating allogenous stem cells without any participation of B-lymphocytes.     

Isolation of Tyr- mutants of facultative methylotrophic Pseudomonas sp. M

A method for isolation of Tyr- mutants of facultative methylotrophic bacteria Pseudomonas sp. M which possess two tyrosine synthesis pathways is presented. The method is based on the two-step blocking of the tyrosine synthesis: the first step of the supplementary pathway of synthesis from phenylalanine, the second being the main pathway from 4-hydroxyphenylpyruvate.