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Biomedical subjects

G Allen

Publications and source records attributed to G Allen.

At least 163 records · Page 9Linked to original sources
PubMed1980

Effects of increased vertical dimension on size of constriction port and fricative sound intelligibility.

The effect of increased vertical bite dimension on fricative sound productions was studied in five adults who wore dentures. Oral port size and sound intelligibility were evaluated at different degrees of artificially induced open bite. The data demonstrate that rapid compensatory adjustments occurred and oral port size changed minimally at all degrees of opening tested. However, in three of the subjects, sound intelligibility declined at the 6-mm opening, and in all subjects, a four-fold increase in sound distortions occurred in the edentulous state. This finding suggests the possibility that either physiological parameters are controlled more successfully than acoustical parameters or that compensatory efforts to maintain constrictor size may, under certain circumstances, adversely affect sound intelligibility.

Adult↗
PubMed1980

An introduction to antigenic variation in trypanosomes.

The salivarian trypanosomes have a unique capacity for antigenic variation at the cell surface. This phenomenon is their primary mechanism for evasion of the host's immune response. Variation is mediated through alternate expression of an extensive repertoire of variant surface glycoproteins (VSGs). Extensive amino acid sequence diversity is responsible for the antigenic diversity of VSGs. All the isolated VSGs of Trypanosoma brucei studied also contain an immunologically cross-reacting glycosyl side chain at the C-terminus, which probably represents a recognition site for proteolytic processing of the hydrophobic putative membrane-binding tail present on the synthesized molecule but not so far found on purified VSGs.

Amino Acid Sequence↗
PubMed1979

Identification of the amino acid residues of proteins S5 and S8 adjacent to each other in the 30 S ribosomal subunit of Escherichia coli.

When Escherichia coli 30 S ribosomal subunits are reacted with protein-protein bifunctional reagents, a number of protein pairs as well as aggregates containing three or more ribosomal proteins are formed. In the present study we have purified one of the protein pairs obtained by reaction of 30 S ribosomal subunits with either radioactive or nonradioactive dimethylsuberimidate. Following molecular weight determination and ammonolysis, the pair was shown to consist of ribosomal proteins S5 and S8. The "native" structure of the complex was surmised from its capacity to be reconstituted into a biologically active 30 S ribosomal subunit. From peptide maps and primary structure determination of various peptides it was demonstrated that the cross-linking bond between ribosomal proteins S5 and S8 involves primarily the residues Lys-93 of protein S8 and the COOH-terminal lysine (Lys-166) of ribosomal protein S5. This result is substantiated by the finding that a mutant carrying an altered S5 lacking the COOH-terminal lysine yields a greatly reduced amount of S5-S8 cross-link. In addition to the points of cross-linking it was found that Lys-30, Lys-68, and Lys-86 of S8 and Lys-5 of S5 react with dimethylsuberimidate, indicating that these residues are available for reaction and suggesting their topographical localization on the ribosomal surface.

Amino Acid Sequence↗
PubMed1979

Holzinger's Hc revised.

The formula H'C = 1 - CDZ/CMZ is suggested as a better summary of twin concordance data than the familiar Holzinger concordance formula, HC = (CMZ - CDZ)/(1 - CDZ). The new formula better estimates degree of genetic determination, G, as calculated from a threshold model, but never exceeds unity, as G sometimes does. For high concordance rates, if CMZ + CDZ greater than 1, HC may be more useful than either G or H'C.

Female↗
PubMed1979

Twin concordance. A more general model.

Estimation of the twin concordance rate for a disease often requires two stages. First, the disease is ascertained in a population or in a population sample, and such twins as are found with the disease become probands. Second, twin pairs with only one proband are further investigated and additional concordant pairs are thus discovered. A mathematical model is presented that allows for continuous variation in completeness of ascertainment in both stages, for correlation within pairs in the primary ascertainment process, and for correlation within pairs in occurrence of the disease. The concordance rate can be estimated by the proband method if secondary ascertainment is complete; other measures of concordance are accurate only if primary ascertainment is complete. A parameter analogous to the concordance rate but related to correlation in primary ascertainment can be estimated from the same data.

Age Factors↗
PubMed1979

The effects of graded experimental trauma on cerebral blood flow and responsiveness to CO2.

The effects of graded mechanical cerebral trauma on cerebrovascular reactivity to CO2 was studied in 26 cats. A fluid-wave percussion model was employed which delivered an epidural trauma of fixed duration and variable amplitude. The animals were maintained at arterial normoxia, with constant monitoring of intracranial and systemic arterial pressures, electroencephalograms, and end-tidal CO2. Following trauma, cerebral blood flow was measured using the H2 ion clearance technique at PaCO2 levels ranging sequentially from 20 to 60 mm Hg. Cerebrovascular reactivity for control animals (uninjured) was 2.7%. In the group with mild trauma (0.76 to 1.90 atm) reactivity was impaired (1.7%), and it was abolished in the severely injured group (2.90 to 4.60 atm). Mild injuries did not alter resting blood flows, while severe trauma resulted in a significant decrease in cerebrovascular resistance. Intracranial and systemic arterial pressures were altered proportionately to the level of cerebral injury. The authors propose that trauma to the brain-stem vasoregulatory centers accounts for these findings.

Animals↗
PubMed1978

Primary structures of cysteine-containing peptides from the calcium ion-transporting adenosine triphosphatase of rabbit sarcoplasmic reticulum.

A preliminary investigation of the primary structure of the Ca(2+-transporting ATPase (adenosine triphosphatase) protein of rabbit skeletal-muscle sarcoplasmic reticulum is reported. The preparation of derivatives of delipidated protein in a form suitable for sequence analysis is described. Tryptic peptides containing S-carboxymethylcysteine residues were isolated from the reduced carboxymethylated protein, and their sequences were partially determined. The results are consistent with mol.wt. about 105000 for the polypeptide, and the absence of extended repeated lengths of sequence. The distribution of tryptophan and cysteine residues between large, aggregated peptides and soluble tryptic peptides shows that these residues are concentrated in different regions of the primary structure. This observation agrees with other evidence that these residues are, on the whole, widely separated in the native protein. The details of the procedures used to isolate the peptides, and the evidence for the determination of their sequences, are given Supplementary Publication SUP 50085 (30 pages), which has been deposited at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem.J. (1978) 169, 5.

Adenosine Triphosphatases↗
PubMed1978

Controlled proteolytic digestion of the M-protein of Sendai virus: the isolation of a fragment of 30000 molecular weight.

Proteolytic digestion of the M-protein of Sendai virus produces a product with a mol. wt. approximately 5000 less than that of the intact protein. In the case of digestion with chymotrypsin this cleavage is quite specific and the cleaved protein can be isolated. The smaller fragment appears to be physically removed from the larger (30000 mol. wt.) fragment, rather than remaining in non-covalent association with it. The cleavage is likely to be near the N-terminus of the protein. At the present time there is no indication of the biological function of this fragment.

Amino Acids↗
PubMed1978

The amino acid sequence of the ribosomal protein S8 of Escherichia coli.

The primary structure of protein S8 from the 30S subunit of Escherichia coli ribosomes has been determined by sequencing the peptides derived from tryptic, chymotryptic, thermolytic and staphylococcal protease digestion of the protein. Protein S8 has 129 amino acid residues which result in a molecular weight of 13996. The N-terminal part of the sequence up to position 68 is in complete agreement with the reported sequence data[1,2]. However, differences exist in the C-terminal half, where an additional hydrophobic tryptic peptide has been found.

Amino Acid Sequence↗
PubMed1978

Oncogenic transformation of non-permissive murine cells by viable equine herpesvirus type 1 (EHV-1) and EHV-1 DNA.

Primary cultures of BALB/c mouse embryo fibroblasts infected with as much as 100 PFU per cell of EHV-1 do not exhibit cytopathology or synthesize detectable amounts of EHV-1 specific RNA, DNA, or infectious virus. Addition of 1--2 microgram of non-fragmented EHV-1 DNA as a co-precipitate with calcium phosphate to monolayers of such non-permissive mouse cells resulted in the appearance, after 4--6 weeks, of foci of piled-up, morphologically altered cells. Cell lines established from such transformed foci exhibited a greatly increased growth rate, unlimited growth potential, aneuploid karyotype, and grew with colony formation in soft agar. Inoculation of 10(6) transformed cells into newborn syngeneic mice resulted in the formation of serially transplantable tumours (undifferentiated fibrosarcomas) with a 100% incidence within eight weeks. Infectious virus could not be rescued from the EHV-1 transformed or tumour-derived cell lines by growth in the presence of IUDR, by cocultivation with permissive horse cells, or by attempts to transfect permissive cells with transformed or tumour cell DNA. However, EHV-1 specific membrane antigens were detected in the transformed cells by immunofluorescence with hyperimmune anti-EHV-1 mouse serum, and the presence of a fragment of the EHV-1 genome was demonstrated in both the transformed and tumour cells. These results indicate that cells nonpermissive for replication of EHV-1 remain susceptible to neoplastic transformation by the EHV-1 genome.

Animals↗