Identifying DNA polymorphisms in human TCRA/D variable genes by direct sequencing of PCR products

 The T-cell receptor (TCR) is a highly variable molecule composed of two polypeptide chains that recognize antigenic peptides in the context of major histocompatibility complex (MHC) molecules. In this study, we describe a sequence-based search for germline polymorphisms in the variable (V) gene segments of the human TCRA/D locus. Thirty different V gene segments were amplified from six to eight unrelated individuals and sequenced from low melting point agarose. Twenty-seven polymorphisms were identified in 15 V gene segments. These polymorphisms are mainly single nucleotide substitutions, but an insertion/deletion polymorphism and a single dinucleotide repeat with variable length were also seen. Of the 15 sequence variations found in the coding regions, six are silent and nine encode amino acid changes. All of the amino acid changes are found at non-conserved residues, frequently in the hypervariable regions, where they may influence MHC and/or peptide recognition. Therefore, it is possible that germline variations in TCR genes could influence an individual’s immune response, and may also contribute to susceptibility to diseases such as autoimmunity. Received: 9 January 1996 / Revised: 22 February 1996     

Endurance training alters alanine and glutamine release from muscle during contractions

The release of alanine and glutamine from perfused muscle of trained and control animals was investigated. Release rates did not differ between trained and control muscle at rest. During contractions in trained muscle, alanine release was higher than at rest, while glutamine release was transiently increased. Phenylalanine release did not differ between trained and control muscle, implying that protein degradation was not increased in trained muscle. The muscle cellular adaptations to training include a selective modification of amino acid output, which could potentially influence gluconeogenic flux and alter muscle ammonia levels during contractions.     

Needle aspiration cytology of a benign and a malignant schwannoma

The histologic and cytologic features of an uncommon solitary, malignant schwannoma and a benign schwannoma are presented. The benign tumor revealed characteristic interlacing fascicles of spindle-shaped cells on both histology and cytology. The malignant schwannoma produced a variable histologic pattern that was selectively sampled from a recurrence in a scar; only obviously malignant, undifferentiated, spindle-shaped cells not capable of further characterization were seen on cytology. Preliminary experience with immunoperoxidase staining for the neural crest marker S-100 protein has been encouraging and may permit identification of these tumors on aspiration smears.     

Effects of temperature,ph, salinity,and inorganic nitrogen on the rate of ammonium oxidation by nitrifiers isolated from wetland environments

Ammonium-oxidizing bacteria were examined in two wetland environments, a freshwater marsh and an estuarine bay, during a 2-year period. Two predominant types were consistently isolated, one from each environment. Both isolates were identified as species ofNitrosomonas. Using a closed culture, high cell density assay, the effects of temperature, pH, salinity, Na⁺, K⁺, nitrite, nitrate, and ammonium concentrations on ammonium oxidation were determined. Maximum activity was observed for the freshwater isolate at 35°C, pH 8.5, salinities of 0.3 to 0.5% Na⁺ and K⁺, and ammonium concentrations greater than 0.5 g/l. For the estuarine isolate, maximum activity was observed at 40°C, pH 8.0, salinities of 0.5 to 1.0%, 1.0% Na⁺ and K⁺, and 0.2 g/l ammonium. The estuarine isolate had a Na⁺ requirement which could be partially substituted by the K⁺, suggesting that the organism is a true estuarine bacterium. Nitrite inhibited both isolates at concentrations greater than 5 mg/l, whereas nitrate had no significant effect on either isolate.     

Peptide map comparisons of epidermal and spleen H-2 molecules

Peptide map comparisons of molecules encoded in the mouseH-2 complex isolated from epidermal cell preparations have been carried out. We previously showed that the Ia molecules from both theI-A andI-E subregions are synthesized by nonlymphoid bone-marrow-derived cells, probably Langerhans cells. The K and D or transplantation molecules are synthesized by both true epidermal cells and nonlymphoid bone-marrow-derived cells. The tryptic maps generated by separating tryptic peptides by high pressure liquid chromatography (HPLC) of epidermal H-2 molecules are identical to their spleen-cell counterparts. The biological significance of this finding is discussed.     

Increased susceptibility of carbamylated glutamate dehydrogenase to proteolysis

Glutamate dehydrogenase is very susceptible to carbamylation which results in loss of activity. The effect of a number of proteolytic enzymes (pronase, trypsin and chymotrypsin) on native and carbamylated glutamate dehydrogenase was tested. In all cases, the carbamylated enzyme was at least twice as susceptible to proteolysis as the native enzyme. Antibodies were prepared against glutamate dehydrogenase and carbamylated glutamate dehydrogenase; the carbamylated enzyme was antigenically indistinguishable from the native enzyme. Preliminary experiments indicate that the carbamylated glutamate dehydrogenase is taken up by ascites tumor cells while glutamate dehydrogenase is not. It seems possible that the effects described can be extrapolated to degradation by lysosomes and to other covalently modified enzymes.     

Distribution ofVibrio cholerae in two Florida estuaries

The distribution ofVibrio cholerae was examined in 2 Florida estuaries, Apalachicola and Tampa Bay.Vibrio cholerae serotype non-01 was the most abundant serotype, being isolated from 45% of the oyster samples, 30% of the sediments, 50% of the waters, and 75% of the blue crabs.Vibrio cholerae serotype 01 was isolated from only one oyster sample. Strong linear correlations betweenV. cholerae and temperature, salinity, or the other physical/chemical parameters measured,Escherichia coli, or fecal coliforms were not observed, but a range of temperatures and salinities appeared relevant to the distribution of the organism. The organism was present in the highest concentrations when salinities were 10‰–25‰ and temperatures were 20?C–35?C.In vitro growth curves of 95V. cholerae environmental isolates further supported that 10‰–25‰ was an ideal salinity range for the organisms. The results suggest thatV. cholerae is a widely distributed organism in the nutrient-rich warm waters of the Gulf Coast estuaries.