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Biomedical subjects

J Allison

Publications and source records attributed to J Allison.

At least 127 records · Page 7Linked to original sources
PubMed1985

(TAA)n within sequences flanking several intrachromosomal variant surface glycoprotein genes in Trypanosoma brucei.

In Trypanosoma brucei telomeric copies of intrachromosomal variant surface glycoprotein (VSG) genes are produced through a gene conversion mechanism and are expressed if the telomere is or becomes transcriptionally activated. We have analyzed a sequence that occurs 1 to 1.5 kb 5' to several intrachromosomal VSG genes. This flanking sequence has three distinct sections: a 5' section containing 5 to 116 TAA or TAA-like tandem repeats; a moderately conserved sequence with an alternating GT characteristic; and a highly conserved 3' sequence that is largely alternating TA. Restriction mapping data and the location of this sequence suggest that it occurs at or near the 5' gene conversion boundary. This sequence, however, is not 5' to all VSG genes. These data suggest that this flanking sequence alone is not sufficient for VSG gene expression but that it may function in gene conversion for many, but not all, VSG genes.

Animals↗
PubMed1985

Lick-trading by rats: on the substitutability of dry, water, and saccharin tubes.

Thirsty rats licked two metal tubes: a water tube paired with another water tube, with saccharin, or with a dry tube. For each pair, a multipoint baseline function was measured by offering free access to one tube throughout each session, and free or restricted access to the other. The three resulting baseline functions showed the members of each pair to be mutual substitutes: When access to either tube was restricted, the rats made more licks at the other. A linear function identified the two water tubes as perfect substitutes. Convex functions identified the members of the saccharin-water and the dry-water pair as imperfect substitutes. Each pair was also tested under several reciprocal fixed-ratio schedules that required instrumental licking of either tube for contingent access to the other. The resulting schedule functions showed the members of each pair to be perfect substitutes: Water licks decreased linearly as licks at the other water tube, the saccharin, or the dry tube increased, in agreement with a conservation model of instrumental performance. Baseline and schedule functions, indistinguishable in the water-water pair, indicated a schedule facilitation of dry-tube licking in the dry-water pair and of water-tube licking in the saccharin-water pair.

Animals↗
PubMed1984

The IsTat 1.3 VSG multigene family in Trypanosoma brucei: retention of the expression linked copy through multiple antigenic switches.

In the IsTaR 1 serodeme of T. brucei the 3 variant surface glycoprotein (VSG) gene family contains about 10 members, one of which has a telomeric location on a minichromosome. The expression linked copy (ELC) of the 3 VSG gene which occurs in an antigenic variant expressing the 3 VSG, also has a telomeric location but unlike the minichromosomal 3 VSG gene has restriction sites upstream from the 5' barren region. This ELC is retained on the same telomere in a subsequent variant that expresses a telomeric 7 VSG ELC and in relapse variants and procyclic forms derived from variant antigenic types (VATs) 3 and 7. The 7 ELC has a restriction map upstream from the 5' barren region that differs from, but is similar to, that of the 3 ELC. These data indicate that the 3 and 7 ELCs are on different telomeres when expressed.

Animals↗
PubMed1984

Antigenic variation in African trypanosomes by gene replacement or activation of alternate telomeres.

We have analyzed antigenic variants with a known lineage and show that there are several telomeres on which variant surface glycoprotein (VSG) genes can be expressed. These telomeres have similar restriction maps 5' to the barren region. In addition, the same VSG gene was expressed on different telomeres. Some antigenic switches in the lineage were accomplished by duplicative replacement of one VSG gene with another. Other switches occurred without duplication by transcriptional activation of an alternate telomeric VSG gene. We call the latter process telomeric activation and propose that these two processes can occur independently. We further propose that antigenic switching by telomeric activation is mediated by the regulatory system that controls which telomere is transcriptionally active, while the duplicative mechanism does not.

Animals↗
PubMed1983

The major histocompatibility complex-restricted antigen receptor on T cells in mouse and man: identification of constant and variable peptides.

The variability of the MHC restricted receptor on murine T cells was examined by comparing tryptic peptide fingerprints of the receptor isolated fom three T cell hybridomas and a T cell tumor. Both variable and constant peptides were seen. Constant peptides were most apparent when comparing receptors from the same mouse strain. Peptide fingerprints of receptors from two independent T cell hybridomas with the same idiotype and specificity were identical. We also describe a molecule detected on the surface of a human T cell leukemia whose properties were identical to those reported for the MHC receptor on normal human T cells. The molecule was a dimer of 85,000-90,000 MW containing a 46,000 MW acidic alpha-chain and an unrelated 40,000 MW neutral beta-chain.

Animals↗
PubMed1981

The construction and partial characterization of plasmids containing complementary DNA sequences to human calcitonin precursor polyprotein.

(1) Total poly(A)-containing RNA isolated from human thyroid medullary carcinoma tissue was shown to direct the synthesis in the wheat germ cell-free system of a major (Mr 21000) and several minor forms of human calcitonin precursor polyproteins. Evidence for processing of these precursor(s) by the wheat germ cell-free system is also presented. (2) A small complementary DNA (cDNA) plasmid library has been constructed in the PstI site of the plasmid pAT153, using total human thyroid medullary carcinoma poly(A)-containing RNA as the starting material. (3) Plasmids containing abundant cDNA sequences were selected by hybridization in situ, and two of these (ph T-B3 and phT-B6) were characterized by hybridization--translation and restriction analysis. Each was shown to contain human calcitonin precursor polyprotein cDNA sequences. (4) RNA blotting techniques demonstrate that the human calcitonin precursor polyprotein is encoded within a mRNA containing 1000 bases. (5) The results demonstrate that human calcitonin is synthesized as a precursor polyprotein.

Calcitonin↗
PubMed1981

A note on choosing a service provider from telephone listings: focus on community mental health centers.

178 college students searched telephone directories with instruction to find help for a friend with a serious emotional problem. There were no significant differences between white and yellow pages or between fine or bold print in the relative frequency with which CMHCs were found. The most important listing in the white pages was "Mental Health Center" and in the yellow pages was under "Clinics." More than two listings did not increase the relative frequency with which CMHCs were found and listed by a proper name was effective only in the absence of generic names.

Choice Behavior↗
PubMed1981

Paired baseline performance as a behavioral ideal.

Several recent theories view performance under the constraints of a schedule as an attempt to approach the basepoint, the total amount of the instrumental response and the total amount of the contingent response seen in the absence of schedule constraint. Some new analyses of experiments on concurrent ratio schedules, and simple ratio schedules offering an optional magnitude of contingent reward, tested this view directly. In each of the five experiments examined the organism rejected the chance of a closer approach to the basepoint, and thereby failed in addition to maximize the rate of reinforcement.

Journal Article↗
PubMed1980

Sclerotherapy of esophageal varices.

Sclerotherapy of esophageal varices is being reevaluated by many surgeons because of increasing dissatisfaction with shunting procedures. A new technique of sclerotherapy using the flexible fiberoptic endoscope with balloon tamponade of variceal channels is being evaluated. To date, 18 patients have been treated by us with this method. Nine patients with active bleeding had control of their hemorrhage. Two patients experienced three episodes of rebleeding. Of patients not actively bleeding at the time of injection, one patient experienced rebleeding and subsequently died. Four other deaths not related to varices have occurred in this series. All surviving patients underwent repeated sclerotherapy until eradication of varices was achieved. This report demonstrates the feasibility of sclerotherapy of esophageal varices using the flexible fiberoptic endoscope.

Adolescent↗
PubMed1979

Measuring prescribing practices in a state mental hospital system.

To determine the degree to which Nebraska's three state mental hospitals complied with recognized guidelines for prescription of psychotropic medications, a study was made for 1326 drug orders issued over a five-year period. The prescribing practices in the hospital were then reviewed in relation to the guidelines in areas of polypharmacy, daily dose frequency, time of day, use of p.r.n. orders, drug form, dosages for children and the elderly, dosages during acute and stabilized stages of illness, and brand versus generic names. The study highlighted areas of progress in drug use practices and identified areas for improvement.

Age Factors↗