Fine structure of the epithelial reticular cells of the medulla of the thymus in the golden hamster

Summary The epithelial reticular cells of the thymic medulla of the golden hamster were studied by electron microscopy. On the basis of their structural details two cell types are distinguished, although the two types are similar in basic structure. The cells of one type are more extended in shape and darker in appearance. They are connected with one another by their cytoplasmic processes, forming a reticulum in the medulla. Thus they appear to play a supporting role as do the cortical epithelial reticular cells. The other cell type is larger, more rounded and lighter. The characteristic feature of this cell type is an abundance of vesicular structures, which occur as vesicles or vacuoles of varying sizes. In addition, an enormous, intracytoplasmic ciliated cyst is occasionally encountered in the latter cell type. The cyst may be regarded as representing a specialized form of the vesicular structures. The possible functional significance of the latter cell type is discussed in relation to recent concepts concerning the mechanism of thymic function.Dedicated to Professor W. Bargmann, under whose guidance my thymus studies were begun, in honor of his 60th birthday (T. Ito).     

Use of the Stereoisomers of Isoleucine by Lactobacillus fermenti

The use of four stereoisomers of isoleucine by Lactobacillus fermenti strain 36 was studied in detail. All four isoleucine isomers were used for growth in the presence of vitamin B(6) compounds, but only l-isoleucine was active in the absence of these vitamins. Of the vitamin B(6) compounds, pyridoxal and pyridoxamine were equally more effective than pyridoxine for the utilization of these isomers. Lowering the initial pH, decreasing the amounts of leucine and valine, and adapting the organism to d-alloisoleucine medium accelerated the use of isoleucine isomers. Thus, the conditions were established under which respective isomers gave the same growth response, and these findings were applied to the separate microbiological assay of l-isoleucine and total isoleucine isomers.     

Histochemical demonstration of O-glycosidically linked,type 3 based ABH antigens in human pancreas using lectin staining and glycosidase digestion procedures

Summary Histochemical analyses of the chemical structures of sugar sequences with or without blood group specificity were carried out by combined stepwise digestion of tissue sections with exo-and endoglycosidases and subsequent lectin stainings in formalin-fixed, paraffin-embedded human pancreas. In acinar cells from blood group A or AB secretor individuals, sequential digestion with -N-acetylgalactosaminidase and -L-fucosidase imparted reactivity with peanut agglutinin (PNA) in cells reactive with Dolichos biflorus agglutinin as well as those with Ulex europaeus agglutinin I(UEA-I). Simple fucosidase digestion imparted the PNA reactivity only in UEA-I reactive cells. Sequential digestion with -galactosidase and fucosidase likewise liberated the PNA binding sites in Griffonia simplicifolia agglutinin I-B₄ reactive cells from blood group B and AB secretors. Sialidase digestion liberated the PNA binding sites not only in acinar cells but also intercalated duct cells, islet cells of Langerhans and endothelial cells. The PNA reactivity obtained by these enzyme digestions was eliminted by endo--N-acetylgalactosaminidase (endo-GalNAcdase) digestion. Preexisting PNA affinity in acinar cells from nonsecretors was also susceptible to endo-GalNAcdase treatment. Following the endo-GalNAcdase digestion, fucosidase or sialidase digestion recovered the PNA reactivity in acinar cells from nonsecretors. These results show that ABH determinants carried on O-glycosidically linked type 3 chain (D-galactose-(1-3)-N-acetyl-D-galactosamine1-serine or threonine) are secreted in pancreatic acinar cells and suggest that product coded by the secretor gene is required for the complete conversion of type 3 precursor chains into H determinants.     

Molecular cloning and nucleotide sequence of a gene for alkaline cellulase from Bacillus sp. KSM-635

A gene for alkaline cellulase from the alkalophilic Bacillus sp. KSM-635 was cloned into the HindIII site of pBR322 and expressed in Escherichia coli HB101. Although the recombinant plasmid contained two HindIII inserts of 2.6 kb and 4.0 kb, the inserts were found to be contiguous in the Bacillus genome by hybridization analysis. Nucleotide sequences of a 2.4 kb region which was indispensable for the production of cellulase, and the flanking, 1.1 kb region, were determined. There was an open reading frame (ORF) of 2823 bp in the 3498 bp sequence determined, which encoded 941 amino acid residues. Two putative ribosome-binding sites and a sigma 43-type, promoter-like sequence were found upstream from an initiation codon in the ORF. The deduced amino-terminal sequence resembles the signal peptide of extracellular proteins. A region of amino acids, 249 to 568, of the deduced amino acid sequence of the cellulase from this organism is homologous with those of alkaline and neutral enzymes of other micro-organisms, but nine amino acid residues were found to be conserved only in the alkaline enzymes.     

Synthesis of polypeptides by microwave heating II. Function of polypeptides synthesized during repeated hydration-dehydration cycles

Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the k_cat values of different resulting polypeptides were 10³–10⁶ times less than those of native hydrolases, the K_m value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)^3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD⁺ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed.     

Synthesis of polypeptides by microwave heating I. Formation of polypeptides during repeated hydration-dehydration cycles and their characterization

Summary Amino acid amides effectively reacted to produce polypeptides in response to microwave heating during repeated hydration-dehydration cycles. The polypeptides, formed from a mixture of glycinamide, alaninamide, valinamide, and aspartic acid -amide, had molecular weights ranging from 1000 to 4000 daltons. Amino acids were incorporated into the polypeptides in proportion to the starting concentrations, with the exception of glycine whose incorporation was 1.5 times higher than that of the other amino acids. The polypeptides had some definite secondary structure, such as -helix and -sheet, in aqueous solution. This reaction provides not only a convenient method for abiotic peptide formation but also a convenient method for the chemical synthesis of peptides.