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J A Hunt

Publications and source records attributed to J A Hunt.

At least 109 records · Page 6Linked to original sources
PubMed1991

Transmission electron microscope in situ fatigue experiments: a computer-control approach.

A computer-control procedure was developed to facilitate in situ fatigue experiments within an intermediate voltage transmission electron microscope using a goniometer-type straining holder. The procedure was designed to allow sine-wave tension-tension cyclic loading of a microfatigue specimen similar in geometry to a center-crack panel fatigue specimen. Computer control allows greater freedom for the operator to control the experiments while providing better reproducibility from one test to another. Further development of this procedure is possible by coupling this computer-control technique with computer-controlled stage motion and digitized TV imaging.

Electronic Data Processing↗
PubMed1991

Quantitative assessment of the tissue response to implanted biomaterials.

The tissue response to a small number of polymeric biomaterials was studied using monoclonal antibodies specific for certain inflammatory cell types, to develop a reliable and accurate method for the quantitative evaluation of biocompatibility. The sites of antibody binding were identified using an avidin-biotin staining procedure and the sections evaluated using a computer-aided image analysis system. The staining technique successfully demonstrated both polymorphonuclear leucocytes and macrophages in tissue samples containing polymeric biomaterials. The image analysis system facilitated the measurement of up to 30 cell-related parameters and allowed a large number of cells to be analysed.

Animals↗
PubMed1991

Rates of DNA change and phylogeny from the DNA sequences of the alcohol dehydrogenase gene for five closely related species of Hawaiian Drosophila.

The sequence of 1.6 kb of DNA surrounding the alcohol dehydrogenase (Adh) gene from five species of the Planitibia subgroup of the Hawaiian picture-winged Drosophila, with estimated divergence times of 0.4-5.1 Myr, has been determined. The gene trees which were found by using the sequence divergence from different regions of the sequences are generally in accord with the phylogeny proposed for these species when chromosomal inversions and island of origin are used. One of the species (D. picticornis) appears to be more distant from the other species in this group than they are from a member of the Grimshawi group (D. affinidisjuncta) which is chromosomally more distant. Two of the species (D. differens and D. plantibia) show heterogeneity in the nucleotide changes in the Adh coding region, heterogeneity which is interpreted to be due to a gene conversion or recombination after hybridization between the two species. The minimal rate of nucleotide substitution of synonymous nucleotides and of nontranscribed nucleotides downstream from the coding region is estimated as 1.5 x 10(-8) and 1.1 x 10(-8) substitutions/nucleotide/year, respectively. This rate is two to three times the maximal rate estimated for mammalian synonymous substitutions.

Alcohol Dehydrogenase↗
PubMed1991

The molecular evolution of the alcohol dehydrogenase locus and the phylogeny of Hawaiian Drosophila.

DNA sequences in the alcohol dehydrogenase genes of flies representing the major groups of Hawaiian Drosophila are used to clarify the relationships of these groups, among themselves and with mainland Drosophila. The topology of the tree derived from these sequences agrees with karyotypic and morphological data but disagrees, in part, with the results of an earlier study that used immunological comparisons between variants of a larval hemolymph protein. A time scale, derived from a comparison of closely related Hawaiian Drosophila species, provides divergence-time estimates that are substantially more recent than those obtained from the immunological studies, although they are still within the bounds set by fossil and biogeographical evidence. The two major lineages of Hawaiian Drosophila, the scaptomyzoids and the drosophiloids, are shown to be widely separated from one another. The scaptomyzoids appear to have diverged early in the history of the subgenus Drosophila, greater than 25 Mya. While hundreds of scaptomyzoid species are found in the Hawaiian archipelago, many fewer are found elsewhere around the world, suggesting that they could have originated outside Hawaii. The drosophiloid lineage is strictly endemic to Hawaii and originated little more than 10 Mya, according to the alcohol dehydrogenase molecular clock. Thus, Drosophila apparently inhabited the Hawaiian archipelago (greater than or equal to 5 Myr before the emergence of the oldest existing high island, Kauai, 5 Mya.

Alcohol Dehydrogenase↗
PubMed1989

A new, improved test system for rapid measurement of blood glucose.

Several models of blood glucose meters are available to diabetic patients. They all require several steps for their operation, which increases the potential for user error. A new meter (One Touch TM System, Lifescan Inc., a Johnson & Johnson Company, Mountain View, CA) was designed to minimise the operational steps and therefore increase reliability. This system was compared for precision, accuracy and clinical safety to the Yellow Spring Instrument (YSI) Model 23A Glucose Analyser (Yellow Springs, OH) in 20 diabetic subjects. Good precision was demonstrated by the coefficient of variation (CV%) in 20 tests performed by each subject on a single heparinised specimen of their own venous blood. The CV was 4.5% (range 1.8-10.4). Accuracy was determined by the regression of the mean of the glucose results corrected for glycolysis compared to the mean YSI result. The regression line had a slope of 1.02, a Y intercept at -4.21 mg/dl, a correlation coefficient (r) of 0.999 (P less than 0.001) and a root mean square % (RMS) error of 4.385. Clinical safety was demonstrated by error grid analysis in which 399 of 400 tests fell in the clinically safe range, and reading error analysis in which two of 400 tests fell more than 25% from the reference method. It is concluded that the One Touch system has good accuracy when compared with the YSI method, is easier to use than the presently available meters, and is a useful addition to the management of diabetes in patients who perform self-monitoring of blood glucose.

Adult↗
PubMed1989

Molecular screening for haemoglobin constant spring.

Haemoglobin H/Constant Spring is an important cause of severe haemoglobin H disease, but the Constant Spring protein is difficult to detect by electrophoresis. A technique for allele specific polymerase chain amplification of the 3'-end of the alpha 2 globin gene improved detection of the alpha cs alpha haemoglobin variant in DNA samples by slot-blot hybridisation. The alpha cs alpha mutation was confirmed in subjects that had been previously diagnosed by haemoglobin electrophoresis, and it was also detected in patients who were negative by protein electrophoresis. 10 of 103 unrelated Laotians with HbE were alpha cs alpha heterozygotes. Of these, 3 were negative to the normal probe because they had -alpha 3.7/alpha cs alpha with a single alpha globin deletion. 5 samples did not amplify or hybridise to either probe because they had deletions of both alpha 2 globin regions. The gene frequency for alpha cs alpha is about 0.05 for Laotians. This technique, which is highly specific and sensitive for rapid detection of the alpha cs alpha mutation, is suitable for clinical diagnoses and population studies. The true incidence of alpha cs alpha may prove to be greater than previously suspected from protein electrophoresis.

Alpha-Globulins↗
PubMed1989

Expression and desensitisation of A2 purinoceptors on cultured bovine aortic endothelial cells.

Purine nucleotides and their metabolites are important mediators of vascular tone. Adenosine promotes relaxation of vascular smooth muscle, acting on the A2 subclass of purinoceptors. There is some evidence that these receptors are also present on vascular endothelial cells. We have therefore examined cultured aortic endothelial cells for adenosine (A2) sensitivity. Bovine aortic endothelial cells (AG4762) were obtained from the Institute of Aging cell repository (USA), and cultured in monolayer flasks. Adenylate cyclase activity in homogenates of AG4762 cells was increased by 5'-(N-ethylcarboxamido)-adenosine (NECA) greater than 2-chloroadenosine greater than adenosine. NECA dependent activation of adenylate cyclase was inhibited by 3-isobutyl-l-methylxanthine greater than theophylline greater than caffeine. The rank order of potency of these compounds identified the responses as mediated by A2 purinoceptors. Prolonged exposure of AG4762 cells to NECA in culture resulted in loss of A2 purinoceptor responsiveness, and purinoceptor activity could be restored to non-dividing densensitized cells by further culture in the absence of the desensitising agent. The cyclic AMP dependent phosphorylation of specific sites in endothelial cells may trigger a number of important biological events which are yet to be determined.

Adenosine↗
PubMed1988

Specific role of manganese and magnesium on RNA synthesis in rabbit bone marrow erythroid cell nuclei.

Specific roles of manganese (Mn) and magnesium (Mg) on the activities of DNA-dependent RNA polymerases I and II isolated from rabbit bone marrow erythroid cell nuclei were investigated. Three main polymerases were separated from the cell nuclei. When RNA polymerase I and Mg were added to the RNA synthesis assay mixture containing erythroid cell DNA as template, RNA transcription activity was highest, but when Mg was replaced with Mn, denatured calf thymus DNA formed a better template than erythroid cell DNA. In contrast, nucleoplasmic DNA from erythroid cell and liver DNA were the best templates to stimulate RNA transcription when RNA polymerase II and Mn were added to the assay mixture. However, if Mn was replaced with Mg, RNA synthesis activity was drastically reduced when the template was nucleoplasmic DNA of erythroid cell. RNA polymerase I and Mg synthesized GC rich RNA, whereas RNA polymerase II and Mn synthesized AU rich RNA. Sedimentation analysis showed that the molecular weights of the RNA produced by polymerase I were larger when the enzyme was activated with Mg than with Mn, whereas those of the RNA produced by polymerase II were larger with Mn than with Mg. Furthermore, RNA produced by polymerase I and Mg using chromatin as a template hybridized better with nucleolar DNA than with nucleoplasmic DNA, whereas that produced by polymerase II and Mn hybridized better with nucleoplasmic DNA than with nucleolar DNA. These results suggest that RNA synthesis is dependent on the activity of specific RNA polymerases and the presence of specific divalent cations and templates, and that the cofactor and template for RNA polymerase I are, respectively, Mg and the nucleolar DNA of cell nuclei, whereas those for RNA polymerase II are Mn and nucleoplasmic DNA.

Animals↗
PubMed1988

DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila.

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.

Alcohol Dehydrogenase↗
PubMed1988

The different types of alpha-thalassemia: practical and genetic aspects.

From May 1985 to October 1987, 1,564 Southeast Asians living in Hawaii were screened for hereditary anemias. Microcytosis was determined by electronic red cell indices and morphology; iron deficiency was ruled out by normal red cell distribution width and normal protoporphyrin levels; Hb E was determined by electrophoresis; beta-thalassemia (thal) heterozygotes were identified by raised Hb A2 on column chromatography. alpha-Thalassemia heterozygotes were diagnosed by exclusion. Family studies helped identify or confirm diagnoses, especially for the alpha-thal-2 heterozygotes (-alpha/alpha alpha) and homozygotes (-alpha/-alpha). Provisional diagnoses are being checked by DNA analyses. Iron deficiency prevented detection of possibly coexisting alpha-thalassemias in 97 individuals. Technical problems included the obscuring of standard criteria for recognizing the alpha-thal variants by the presence of Hb E or beta-thal. In such cases, alpha-thal could only be detected by family studies or DNA analyses. Problems with hemoglobin (Hb) electrophoresis included Hb H migrating beyond the edge of the strip if incubation was not closely monitored, and difficulty in detecting the small amounts of unstable Hb Constant Spring. DNA analyses also had limitations, since the nondeletion alpha-thalassemias would not be detected by routine Southern blotting. DNA analyses suggested that about 50% of presumed alpha-thalassemias were alpha-thal-2 (-alpha/alpha alpha) variants, and a corresponding number of alpha-thal-2 variants were among the apparent normals. Gene frequencies in the unselected Lao subjects were approximately 0.2 for Hb E, at least 0.1 for (-alpha), usually a rightward (alpha -3.7) type, 0.04 for (-), and 0.01 for a beta-thal. Multistep screening for the alpha- and beta-thalassemias was an effective and efficient strategy.

Asia, Southeastern↗
PubMed1988

Alpha-thalassemia screening reveals quadruple zeta-globin genes in a Laotian family.

In screening families for alpha-thalassemia (thal) by the Southern blot technique, several Laotian families were found which had anomalous zeta-globin haplotypes. The zeta-globin genes encode alpha-like embryonic hemoglobin subunits in the alpha-globin multigene complex on chromosome 16. There are normally two zeta-globin genes in this cluster: 5' zeta 2 and 3' psi zeta 1. In our study, six individuals in three families had triple zeta-globin genes. Another family revealed a novel quadruple zeta-globin arrangement. Two aberrant fragments were seen in Eco R1, Bam H1, Bgl II and Hind III digests using a zeta-globin gene probe. These anomalous bands were in the integral 10 kb range consistent with duplication of the zeta-globin region. This haplotype interpretation was confirmed by Southern blot analyses using double digestions hybridized to a cDNA zeta-gene probe, and Pvu II digests probed with a 5'-psi zeta 1 intergenic fragment. Proposed mechanisms of recombination and implications of this novel arrangement are discussed.

Blotting, Southern↗
PubMed1986

Surgical management of diffuse peritonitis complicating obstetric/gynecologic infections.

A retrospective review of 176 women undergoing surgery for diffuse peritonitis secondary to pelvic infections from 1972 to 1976 was conducted. Mortality with septic abortion was 27.3% (12 of 44), with pelvic inflammatory disease 7.1% (eight of 113), and with puerperal sepsis 6.7% (one of 15). Overall mortality was 13.1% (23 of 176). Mortality was lower (P less than .05) with surgery within 24 hours (7.5%, six of 80) than after 24 hours (17.7%, 17 of 96). Mortality was lower (P less than .01) with specific antianaerobic antibiotics (zero of 36) than without (16.4%, 23 of 140). Mortality was 21.3% with hysterectomy (ten of 47) and 10.1% (13 of 129) with conservative surgery, however hysterectomy was usually performed in the more severe cases (septic abortion 75%, puerperal sepsis 66%, pelvic inflammatory disease 3%). Mortality declined from 17.6% in 1972 to 1974 (21 of 119) to 3.5% in 1975 to 1976 (two of 57). Significant differences between the two periods included an increased use of specific antianaerobic antibiotics (8.4%/45.5%) and an increased incidence of early surgery (35.3%/66.6%) in the latter years. This series emphasizes the overriding importance of early surgery and the need for the inclusion of specific antianaerobic antibiotic agents in the chemotherapeutic regimen.

Abortion, Septic↗
PubMed1985

In vitro stimulation of monocyte tissue factor activity by autologous platelets.

Washed human platelets were found to enhance phytohemagglutinin (PHA)-stimulated tissue factor (TF) synthesis when incubated with autologous mononuclear cell cultures. Furthermore, platelets increased TF synthesis even when no other stimulator was present during the incubation. Experiments utilizing similar cultures derived from blood of patients with Glanzmann's disease, von Willebrand's disease, and platelet storage pool disease indicated that platelets with each of these genetic defects possessed the capacity to enhance the synthesis of this initiator of coagulation by unstimulated cells as did normal platelets. The degree of platelet enhancement varied between individuals, but for any given donor, the extent of the effect depended on the concentration of platelets used. The effect was demonstrable at platelet/monocyte ratios ranging from a low of approximately 15 to the highest ratio used, about 300. For comparison the ratio of these two cellular elements in normal human blood is estimated to be approximately 1,000. These findings may reflect a relationship between these two cell types that can occur in vivo.

Blood Coagulation↗
PubMed1984

Chromosomal mapping of a middle-repetitive DNA sequence in a cluster of five species of Hawaiian Drosophila.

We describe the properties of a repetitive transposable element isolated from a chromosomal site close to the Adh (alcohol dehydrogenase gene) region of the Hawaiian Drosophila species, D. heteroneura. The cloned element is less than 2 kilobases in length. Although its polytene chromosome sites are constant in an individual, it shows a pattern of in situ hybridization that varies both within and between five species of the D. planitibia subgroup. These species are closely related, having diverged at various times from 0.5 to 5 million years ago. The distribution of the element appears to reflect the evolutionary relationships of the species except that the differences between D. planitibia and D. differens are ambiguous. Evidence of ragged excision of the element is found in one species.

Alcohol Dehydrogenase↗
PubMed1984

Continual postoperative antibiotic peritoneal lavage in diffuse peritonitis complicating cesarean section.

Nine women treated surgically for diffuse peritonitis complicating cesarean section underwent continual postoperative antibiotic peritoneal lavage as an adjunct to surgery. In all the patients the indication for surgery was failure to respond to standard medical therapy. Seven patients treated with hysterectomy recovered without evidence of continuing peritonitis or intraabdominal abscess formation. One of two patients in whom uterine conservation was attempted required an emergency hysterectomy three days later. In this series, continual postoperative antibiotic peritoneal lavage appeared to be an effective adjunctive treatment in the prevention of continuing peritonitis and abscess formation provided that hysterectomy was performed at the initial operation.

Adult↗