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Biomedical subjects

L Snyder

Publications and source records attributed to L Snyder.

13 recordsLinked to original sources
PubMed1992

Cytogenetic characterization of B-cell lymphomas from severe combined immunodeficiency disease mice given injections of lymphocytes from Epstein-Barr virus-positive donors.

We analyzed the karyotype of 27 B-cell lymphomas of human origin that developed in mice with severe combined immunodeficiency disease following the injection of peripheral blood leukocytes from Epstein-Barr virus-seropositive donors. Three tumors had clonal abnormalities detected with conventional techniques, 2 had trisomy 11, and 1 had a del(6)(q21q25). One other tumor had trisomy 11 detected with fluorescence in situ hybridization. Twelve tumors had a normal karyotype, 11 tumors had nonclonal abnormalities (which included trisomy 9 or 12 in 3 or 2 tumors, respectively), and one tumor had a karyotype of 92,XXXX(75%)/46,XX(25%) by conventional cytogenetic analysis. Trisomy for chromosomes, 9, 11, and 12 are recurring abnormalities that have been observed in lymphomas associated with an immunocompromised state. Clonal or nonclonal abnormalities were observed in 8 of 11 tumors derived from 3 donors whose peripheral lymphocytes induced a high incidence of tumors in mice with severe combined immunodeficiency disease compared with a clonal abnormality and 2 nonclonal abnormal cells in 2 of 5 tumors derived from 3 donors whose lymphocytes induced an intermediate to low incidence. These observations suggest an association between a higher incidence of karyotypically abnormal cells in lymphomas and the increased tumorigenic potential of the lymphocytes that induced these tumors.

Animals↗
PubMed1990

A site in the T4 bacteriophage major head protein gene that can promote the inhibition of all translation in Escherichia coli.

The cryptic DNA element, e14, synthesizes a protein, Lit, which can inhibit gene expression late in T4 bacteriophage development. This inhibition is due to the interaction between the Lit protein and a short region, the gol region, within gene 23, the major head protein gene of phage T4. We have constructed plasmids in which the gol region is transcribed from the lac promoter and fused translationally and transcriptionally to lacZ and cat (chloramphenicol acetyltransferase). These fusion plasmids were used to demonstrate that, in the presence of Lit protein, the gol region inhibits the expression of genes downstream in the same transcription unit. This local inhibition does not require the gene 23 polypeptide from the gol region. In addition, inducing the transcription and translation of the gol region in the presence of Lit protein causes an immediate global inhibition of all translation in Escherichia coli. This global inhibition does require the gene 23 polypeptide. No more than 75 base-pairs of DNA from the gol region are required for both the local and global inhibitions. The gol region sequence contains a short dyad symmetry. However, it is the sequence of bases in the region of dyad symmetry and not the ability to form a hairpin in the RNA that is required for gol region activity.

Amino Acid Sequence↗
PubMed1990

The optional E. coli prr locus encodes a latent form of phage T4-induced anticodon nuclease.

The optional Escherichia coli prr locus restricts phage T4 mutants lacking polynucleotide kinase or RNA ligase. Underlying this restriction is the specific manifestation of the T4-induced anticodon nuclease, an enzyme which triggers the cleavage-ligation of the host tRNALys. We report here the molecular cloning, nucleotide sequence and mutational analysis of prr-associated DNA. The results indicate that prr encodes a latent form of anticodon nuclease consisting of a core enzyme and cognate masking agents. They suggest that the T4-encoded factors of anticodon nuclease counteract the prr-encoded masking agents, thus activating the latent enzyme. The encoding of a tRNA cleavage-ligation pathway by two separate genetic systems which cohabitate E. coli may provide a clue to the evolution of RNA splicing mechanisms mediated by proteins.

Amino Acid Sequence↗
PubMed1978

Isolation of a bacterial host selective for bacteriophage T4 containing cytosine in its DNA.

An Escherichia coli B strain, B834 galU56, has been isolated which supports growth of bacteriophage T4 with cytosine in its DNA while restricting growth of T4 with hydroxymethylcytosine. This host is partially deficient in uridine diphosphoglucose as determined by the ability of DNA isolated from T4 grown on it to accept glucose in an in vitro assay. In this mutant an intact rgl restriction system recognizes unglucosylated hydroxymethylcytosine residues in phage DNA, while the absence of a functional rB restriction function prevents degradation of unmodified DNA containing cytosine.

Coliphages↗
PubMed1977

Postmortem pink teeth.

A series of cases is reported in which pink teeth were observed during the postmortem period. Most cases were associated with decomposition in a moist environment. Experimental procedures led to the extraction of pink material from dentin and demonstration that hemoglobin and serum proteins were present. The pink-tooth phenomenon was duplicated in human teeth by instilling into the pulp chambers whole blood and blood with the red cells hemolyzed. The change was manifested in teeth of dogs after freezing, heating, and decomposition in a moist environment. The authors postulate that pink teeth occur as a result of breakdown of red blood cells in the pulp chamber of the tooth and diffusion of hemoglobin and other serum proteins into the dentin via the dential tubules. Histochemical studies show that the brown or gray material in some teeth subjected to postmortem aging is probably hemoglobin and serum proteins. Factors of age, vascularity of the pulp chamber, and postmortem conditions are discussed in relation to the postmortem development of pink teeth.

Adult↗
PubMed1977

Transient and permanent effects of hyperthermia in dogs: a study of a simulated air transport environmental stress.

Heat-induced hyperthermia can be a major problem in dogs shipped during summer months. Dogs shipped by air transport can encounter temperatures as high as 54.4 C. Usually, little concern is given to effects produced by hyperthermia. To assess the heat stress problem, 20 dogs were exposed to a temperature of 54.4 C for 30 minutes--10 dogs at 15% relative humidity and 10 dogs at 35%. Dogs did not die as a result of exposure, but certain transient and permanent changes occurred. All dogs had increased heart rate, rectal temperature, blood pH, hemoglobin concentration, packed cell volume, and erythrocyte count. Body weight and PVCO2, decreased. Differences also were shown between the 2 humidity group for blood PH PVCO2, rectal temperature, and weight loss. The major tissue changes attributed to hyperthermia were fragmentation of the myocardium, acute cortical necrosis in kidney, and marked degenerative changes in the cerebellum and cerebral cortex. Changes in the cerebellum and cerebral cortex were considered severe and permanent.

Aircraft↗
PubMed1976

A gene of bacteriophage T4 whose product prevents true late transcription on cytosine-containing T4 DNA.

T-even coliphages have 5-hydroxymethylcytosine in their DNA instead of cytosine. In some T4 mutants, the replicated DNA contains cytosine, but then no late gene products are made. We show that the inability to make late gene products with cytosine-containing T4 DNA is due to a T4 gene products. This gene product, while probably nonessential under normal conditions, interacts with an essential part of the transcription apparatus. Mutations in this gene allow viable T4 particles to be made whose DNA has been substituted almost 100% with cytosine.

Coliphages↗