N-terminal acetyl-peptides from two calf thymus histones

1. The same N-terminal peptide was isolated from two major calf thymus histone fractions, F2al and F2a2. 2. The structure of the peptides is N-acetylseryl-glycyl-arginine, and the yields account for most of the N-acetyl groups previously found in these histones. 3. Some other peptides not giving a ninhydrin reaction were also investigated.     

Correlation of cell surface antigen expression on human thymocytes by multi-color flow cytometric analysis: implications for differentiation

Thymocytes undergo a complex series of phenotypic and genotypic changes during maturation in the thymus. This dynamic process involves qualitative and quantitative changes in the expression of certain cell surface differentiation antigens. In this study, we have directly examined the relationship of T cell differentiation antigen expression on normal human thymocytes by using multi-color immunofluorescence and multi-parameter flow cytometric analysis. The results from these studies have provided new insights into the complexity of antigen expression during thymic maturation and suggest that the CD3/T cell antigen receptor complex is expressed early in the development of thymocytes. Direct quantitative measurements of antigen expression by using multi-parameter flow cytometric analysis also suggest quantitative co-regulation of certain antigens (e.g., CD3 and CD5) during thymic maturation.     

Amino-Terminal Charge Affects the Periplasmic Accumulation of Recombinant Heregulin/EGF Hybrids Exported Using theEscherichia coliAlkaline Phosphatase Signal Sequence

AnEscherichia coliexpression system that exploits the bacterial alkaline phosphatase (PhoA) signal sequence to translocate recombinant human epidermal growth factor (hEGF) to the periplasm was used to evaluate how changes in the composition and sequence of amino acids near the PhoA–hEGF junction influence the periplasmic accumulation of recombinant protein. A series of chimeric structural genes was generated byin vitroreplacement of hEGF sequence with analogous segments from the EGF-like domain of human heregulin (HRG), significantly altering the electrostatic character of the amino-terminal region of the mature protein. Quantitation of HRG/EGF protein inE. coliperiplasmic extracts, by RP-HPLC, showed a fourfold decrease after one of two acidic residues located in the amino-terminal region of the mature hEGF, near the PhoA junction, was replaced. An additional threefold decrease was observed when the second acidic residue was replaced with a positively charged lysine. Further extension of the amino-terminal HRG sequence, beyond the first six residues, resulted in net neutralization of a more distant EGF acidic residue with no additional effect on protein yield. The importance of having a negatively charged group in the amino-terminal region of the mature protein was confirmed when insertion of an aspartic acid near the amino-terminus of two poorly expressed hybrid protein sequences resulted in a five- to eightfold increase in their recovery from the periplasm. This study demonstrates the importance of having negatively charged residues near the fusion junction of recombinant proteins expressed inE. coliusing the PhoA signal sequence for protein export.     

Dictyosome vesicle production and plasma membrane turnover in auxin-stimulated outer epidermal cells of coleoptile segments fromAvena sativa (L.)

Summary Dark grown coleoptile segments were floated on solutions of IAA alone and of IAA and the secretion inhibitors cytochalasin and monensin. The secretion inhibitors prevented normal elongation of the tissue segments, the monensin inhibition being virtually complete while cytochalasin gave a 40% reduction over the first six hours with little further further elongation in the following 18 hours. Vesicle production was assessed in outer epidermal cells after 6 hours of IAA-stimulated elongation using the vesicle accumulation method following a cytochalasin-block of vesicle transport. The results were compared with the area of plasma membrane required to enable cell elongation to proceed at the observed rate. The area of vesicle membrane delivered to the cell surface exceeded this requirement to such an extent that at least 65% of the delivered membrane must be recycled back into the cytoplasm. Expressed in terms of the whole cell, the plasma membrane turnover rate was found to be once every 200 minutes. It is concluded that limitation of elongation by secretion inhibitors is more likely to reflect a requirement for the vesicle contents than the vesicle membrane. These results are compared with those obtained from other secretory systems using a similar approach.Abbreviations IAA indole acetic acid - DMSO dimethyl sulphoxide - D dictyosome - ER endoplasmic reticulum - V vesicle     

Studies on anaerobic bacteria

Summary A new chromogenic anaerobe, Clostridium roseum nov. spec., has been found. It is characterized by: red-orange pigment, turning purplish on oxidation; gelatin liquefaction and other evidence of proteolysis; nitrate reduction; fermentation of various carbohydrates including pectin; close resemblance to Cl. acetobutylicum in corn mash fermentation, with the same neutral products, acetone, ethyl alcohol and butyl alcohol, in nearly the same ratios; agglutinative specificity and separation from Cl. acetobutylicum and Cl. felsineum, as well as several less nearly physiologically related butyric anaerobes.     

Cell-wall lysing enzymes and products of cell-wall digestion elicit ethylene in citrus

Ethylene production was induced in Valencia oranges [ Citrus sinensis (L.) Osbcck] by injection of the fungal enzyme mixture Pectolyase ( Aspergillus japonicus ) which contains pectolytic enzymes into the peel. The mixture also stimulated production of 1-aminocyclopropane-1-carboxylic acid (ACC). Cycloheximide partially inhibited the Pectolyase-induced ethylene response. Pectin fragments, resulting from partial acid hydrolysis or Pectolyase digestion, caused an increase in ethylene production when injected into the peel of intact orange fruits. Pectic fragments produced by fungal enzymes are known to be elicitors of phytoalexins and in this study are shown to elicit ethylene in citurs.     

Twin death and mourning worldwide: a review of the literature.

Cultural beliefs about the nature of multiples appear in the mourning practices of many civilizations. Ethnographic literature suggests common themes that echo modern concepts. Many societies viewed twins as fragile, likely to die without preferential or meticulously equal treatment. A shared soul between twins is a common tenet, and the death of one is often felt to herald the other's prompt demise. The close relationship between multiples influences funerary rites. Honor, fear and mysticism are often evident in rituals. Twin infanticide was widely practiced, yet mourning customs were still observed. Many peoples recognize the special status of multiples and their families after one, two or more die.