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Biomedical subjects

J C Hall

Publications and source records attributed to J C Hall.

At least 109 records · Page 6Linked to original sources
PubMed1997

Purification, characterization, and expression of rat epididymal beta-D-galactosidase.

The purpose of the present study is to purify, kinetically characterize and measure the amount of soluble acid beta-D-galactosidase (EC 3.2.1.23) in different anatomical regions (caput, corpus, and cauda) of the adult rat epididymis. Based upon SDS-PAGE analysis, the subunit molecular mass of the caput and cauda enzyme is approximately 85,000 daltons while the corpus enzyme is approximately 50,000 daltons. The apparent Km and Vmax values are 67, 24, and 59 microM and 5.0, 1.88 and 6.3 microM/min./-mg protein for the enzyme purified from the caput, corpus, and cauda regions of the epididymis, respectively. However, no regional differences in the amount of soluble enzyme protein are observed. These data demonstrates regional differences in the activity of epididymal acid beta-D-galactosidase and suggest that the observed regional differences in enzyme activity may be due to posttranslational modifications.

Animals↗
PubMed1997

Genomic organization and evolution of alternative exons in a Drosophila calcium channel gene.

The genomic organization of a gene coding for an alpha 1 subunit of a voltage-gated calcium channel of Drosophila melanogaster (Dmca IA) was determined. Thirty-four exons, distributed over 45 kb of genomic sequence, have been identified and mapped, including exons in three regions involved in alternative splicing and new sites potentially involved in RNA editing. The comparison of the intron/exon boundaries of this channel with a mammalian counterpart shows that the genomic structure of these two genes has remained fairly similar during evolution, with more than half of the Drosophila intron positions being perfectly conserved compared to the human channel. Phylogenetic analysis of the mutually exclusive alternative exons revealed that they have diverged considerably. It is suggested that this divergence, rather than reflecting evolutionary age, is the likely result of accelerated rates of evolution following duplication.

Amino Acid Sequence↗
PubMed1997

Extended reproductive roles of the fruitless gene in Drosophila melanogaster revealed by behavioral analysis of new fru mutants.

The fruitless mutants fru3 and fru4 were assessed for sex-specific reproductive-behavioral phenotypes and compared to the previously reported fru mutants. Among the several behavioral anomalies exhibited by males expressing these relatively new mutations, some are unique. fru3 and fru4 males are less stimulated to court females than fru1 and fru2. No courtship pulse song is generated by either fru3 or fru4 males, even though they perform brief wing extensions. fru3 and fru4 males display significantly less chaining behavior than do fru1 males. The hierarchy of courtship responses by fru males directed toward females vs. males, when presented with both sexes simultaneously, is that fru1 males perform vigorous and indiscriminant courtship directed at either sex; fru4 males are similarly indiscriminant, but courtship levels were lower than fru1; fru2 males prefer females; fru3 males show a courtship bias toward males. fru3 and fru4 males essentially lack the Muscle of Lawrence (MOL). On several reproductive criteria, there was no difference between fru-variant females and fru+. The increases in phenotypic severity measured for the new mutants are discussed in the context of the emerging molecular genetics of fru and with regard to the gene's position within the sex-determination pathway.

Animals↗
PubMed1997

Review: Peyer's patches.

The function of Peyer's patches as antigenic sampling sites involves the complex interplay of a variety of mechanisms that aim to recognize luminal antigens, induce an immunological response and decrease the incidence of antigen translocation across the mucosal epithelium. This is achieved by M cells, which facilitate the uptake of luminal antigens, a vascular architecture that promotes the retention of absorbed antigens within the patch interstitium (allowing for maximal antigenic activation of lymphocytes) and the presence of lymphoid follicles that contain antigen-presenting cells and lymphocytes. Lymphocytes encountering antigen in the Peyer's patches proliferate, differentiate into fully mature antigen-specific effector cells and migrate to the mesenteric lymph nodes where they undergo final maturation. The mature lymphocytes then enter the systemic circulation and migrate throughout the other mucosa-associated lymphoid tissues of the body and "home' into the gut via high endothelial venules and gut-associated lymphoid tissue-specific adhesion molecules, providing antigen-specific lymphocytes at sites likely to re-encounter the antigen.

Animals↗
PubMed1997

Enteral branched-chain amino acids increase the specific activity of jejunal glutaminase and reduce jejunal atrophy.

Branched-chain amino acid (BCAA)-enriched nutrient solutions reduce gut atrophy associated with parenteral nutrition. We hypothesized that this effect was mediated by phosphate-dependent glutaminase. Thirty male Wistar rats (300-350 g) underwent a standardized surgical procedure and were then randomized into three groups to receive 6 days of ad libitum enteral nutrition. The animals were fed a solution of conventional nutrients, a solution of conventional nutrients enriched with 2.0% BCAA or a solution of conventional parenteral nutrients enriched with 2.5% glutamine. When compared with rats fed conventional nutrients, rats fed BCAA and glutamine had less jejunal atrophy (P < 0.05) and a greater specific activity of phosphate-dependent glutaminase in the jejunum (131%; P < 0.05). It is concluded that enteral BCAA reduce atrophy of the jejunum via the generation of glutamine.

Amino Acids, Branched-Chain↗
PubMed1997

Circadian cycling of a PERIOD-beta-galactosidase fusion protein in Drosophila: evidence for cyclical degradation.

The authors analyzed circadian features of two period-lacZ (per-lacZ) fusion genes in transgenic strains of Drosophila. Both genes manifest circadian fluctuations of mRNA levels, but fluctuations of only the larger chimeric protein are apparent. Fusion protein cycling is indistinguishable from the behavior of wild-type per protein (PER), including apparent temporal regulation of phosphorylation state. Several arguments indicate that the difference in the two constructs is proper regulation at the level of protein turnover: the smaller protein has much higher levels; a beta-galactosidase degradation products is visible in both strains but fails to manifest cycling, presumably due to a long half-life; and only the noncycling proteins accumulate as a function of adult age. The large cycling fusion protein also undergoes modest cycling in an arrhythmic per01 background. This is light dependent, resembles the regulation of the timeless protein (TIM) by light, and reflects a documented fusion protein-TIM interaction. The results are discussed with respect to the posttranscriptional regulation that is necessary for proper cycling of both PER and TIM as well as for clock function.

Aging↗
PubMed1997

Quantitative analysis of Drosophila period gene transcription in living animals.

To determine the in vivo regulatory pattern of the clock gene period (per), the authors recently developed transgenic Drosophila carrying a luciferase cDNA fused to the promoter region of per. They have now carried out noninvasive, high time-resolution experiments allowing high-throughput monitoring of circadian bioluminescence rhythms in individual living adults for several days. This immediately solved several problems (resulting directly from individual asynchrony within a population) that have accompanied previous biochemical experiments in which groups of animals were sacrificed at each time point. Furthermore, the authors have developed numerical analysis methods for automatically determining rhythmicity associated with bioluminescence records from single flies. This has revealed some features of per gene transcription that were previously unappreciated and provides a general strategy for the analysis of rhythmic time series in the study of molecular rhythms.

Animals↗
PubMed1997

Rhythmic expression of a PER-reporter in the Malpighian tubules of decapitated Drosophila: evidence for a brain-independent circadian clock.

The protein product (PER) of the Drosophila clock gene, period (per), is involved in a molecular feedback loop in which PER inhibits the transcription of its own mRNA. This feedback causes the PER protein to cycle in a circadian manner, and this cycling in specific regions of the brain (the presumed location of the central pacemaker) is responsible for the rhythmicity of locomotor activity and possibly eclosion. PER has also been detected in several nonneural tissues in the abdomen, but whether PER exhibits free-running and light-sensitive cycles in any of these tissues is not known. In this study, the authors assayed the spatial and temporal distribution of a PER-reporter expressed in transgenic flies carrying a per-lacZ construct, which was shown to cycle in per-expressing brain cells. The authors demonstrate that this PER-reporter fusion protein cycles in the Malpighian tubules, showing first cytoplasmic accumulation, which is then followed by translocation of the signal into the nucleus. To test whether this rhythm was controlled by the brain, flies were decapitated and assayed for 3 days after decapitation. Expression patterns of PER-reporter in decapitated flies were nearly identical to those in intact flies reared in normal light-dark cycles, reversed light-dark cycles (phase shifted), and constant darkness. These results suggest that the Malpighian tubules contain a circadian pacemaker that functions independently of the brain.

Animals↗
PubMed1997

The role of wound infection as a clinical indicator after colorectal surgery.

The objective of this study was to evaluate the role of wound infection as a clinical indicator after colorectal surgery. We assessed 553 patients who were entered into clinical trials at Royal Perth Hospital. In the clinical trials, the incidence of wound infection after colorectal surgery was 12%, however, this rose to 20% for patients over 60 years of age and with an American Society of Anaesthesia score of greater than 2. One-third of these infections occurred following discharge from hospital. We found that the incidence of wound infection following colorectal surgery was dependent upon patient characteristics, and many infections occurred after discharge from hospital. Collecting this data accurately is time consuming and expensive. Therefore, for this reason alone, wound infection may not be an appropriate clinical indicator for patients undergoing colorectal surgery.

Age Factors↗
PubMed1996

A Drosophila calcium channel alpha1 subunit gene maps to a genetic locus associated with behavioral and visual defects.

We have cloned cDNAs that encode a complete open reading frame for a calcium channel alpha1 subunit from Drosophila melanogaster. The deduced 1851 amino acid protein belongs to the superfamily of voltage-gated sodium and calcium channels. Phylogenetic analysis shows that the sequence of this subunit is relatively distant from sodium channel alpha subunits and most similar to genes encoding the A, B, and E isoforms of calcium channel alpha1 subunits. To indicate its similarity to this subfamily of vertebrate isoforms, we name this protein Dmca1A, for Drosophila melanogaster calcium channel alpha1 subunit, type A. Northern blot analysis detected a single 10. 5 kb transcript class that is regulated developmentally, with expression peaks in the first larval instar, midpupal, and late pupal stages. In late-stage embryos, Dmca1A is expressed preferentially in the nervous system. Variant transcripts are generated by alternative splicing. In addition, single nucleotide variations between cDNAs and genomic sequence are consistent with RNA editing. Dmca1A maps to a chromosomal region implicated in, and is the likely candidate for, the gene involved in the generation of behavioral, physiological, and lethal phenotypes of the cacophony, nightblind-A, and lethal(1)L13 mutants.

Amino Acid Sequence↗
PubMed1996

Control of male sexual behavior and sexual orientation in Drosophila by the fruitless gene.

Sexual orientation and courtship behavior in Drosophila are regulated by fruitless (fru), the first gene in a branch of the sex-determination hierarchy functioning specifically in the central nervous system (CNS). The phenotypes of new fru mutants encompass nearly all aspects of male sexual behavior. Alternative splicing of fru transcripts produces sex-specific proteins belonging to the BTB-ZF family of transcriptional regulators. The sex-specific fru products are produced in only about 500 of the 10(5) neurons that comprise the CNS. The properties of neurons expressing these fru products suggest that fru specifies the fates or activities of neurons that carry out higher order control functions to elicit and coordinate the activities comprising male courtship behavior.

Age Factors↗
PubMed1996

Defects in courtship and vision caused by amino acid substitutions in a putative RNA-binding protein encoded by the no-on-transient A (nonA) gene of Drosophila.

The Drosophila no-on-transient A (nonA) gene is involved in the visual behaviors and courtship song of the fly. The NONA polypeptide contains two copies of the RNA-recognition motif (RRM), a hallmark of proteins involved in RNA binding, and an adjacent conserved charged region. This 311-amino-acid region is found in four other proteins and largely overlaps the Drosophila-Behavior/Human Splicing (or DBHS) domain. The newest family member, Drosophila nAhomo, was discovered in a database search, and encodes a protein with 80% identity to NONA. In this study, three nonA mutations generated by chemical mutagenesis were sequenced and found to fall within the conserved region. Site-directed mutagenesis of the two RRMs, and within a (conserved) charged region located C-terminal to them, was performed to determine the significance of these domains with respect to whole-organismal phenotypes. Behavior and viability were assessed in transformed flies, the genetic background of which lacks the nonA locus. Point mutations of amino acid 548 in the charged region confirmed the etiology of the nonAdiss courtship-song mutation and showed that a milder substitution at this site produced intermediate singing behavior, although it failed to rescue visual defects. Mutagenesis of the RRM1 domain resulted in effects on viability, vision, and courtship song. However, amino acid substitutions in RNP-II of RRM2 led to near-normal phenotypes, and the in vivo nonA mutations located in or near RRM2 caused visual defects only. Thus, we suggest that the first RRM could be important for all functions influenced by nonA, whereas the second RRM may be required primarily for normal vision.

Amino Acid Sequence↗
PubMed1996

Prevention of respiratory complications after abdominal surgery: a randomised clinical trial.

OBJECTIVE: To evaluate the prevention of respiratory complications after abdominal surgery by a comparison of a global policy of incentive spirometry with a regimen consisting of deep breathing exercises for low risk patients and incentive spirometry plus physiotherapy for high risk patients. DESIGN: Stratified randomised trial. SETTING: General surgical service of an urban teaching hospital. PATIENTS: 456 patients undergoing abdominal surgery. Patients less than 60 years of age with an American Society of Anesthesia classification of 1 were considered to be at low risk. OUTCOME MEASURES: Respiratory complications were defined as clinical features consistent with collapse or consolidation, a temperature above 38 degrees C, plus either confirmatory chest radiology or positive results on sputum microbiology. We also recorded the time that staff devoted to prophylactic respiratory therapy. RESULTS: There was good baseline equivalence between the groups. The incidence of respiratory complications was 15% (35/231) for patients in the incentive spirometry group and 12% (28/225) for patients in the mixed therapy group (P = 0.40; 95% confidence interval -3.6% to 9.0%). It required similar amounts of staff time to provide incentive spirometry and deep breathing exercises for low risk patients. The inclusion of physiotherapy for high risk patients, however, resulted in the utilisation of an extra 30 minutes of staff time per patient. CONCLUSIONS: When the use of resources is taken into account, the most efficient regimen of prophylaxis against respiratory complications after abdominal surgery is deep breathing exercises for low risk patients and incentive spirometry for high risk patients.

Abdomen↗
PubMed1996

Warm ischaemia time in a model for small bowel transplantation.

Intestinal transplantation is associated with high rates of mortality and morbidity. This paper details our initial experience with 82 heterotopic small bowel transplants based upon the original rat model described by Monchik and Russell (Surgery 70:693-702, 1971). A key issue associated with mortality was a warm ischaemia time of more than 40 min (P < 0.01). Sixty-eight percent of the recipients (44/65) survived for more than 24 hr when the warm ischaemia time of the donor bowel was reduced to less than 40 min. Investigators establishing an animal model of heterotopic small bowel transplantation should pay particular attention to the warm ischaemia time of the donor bowel.

Animals↗
PubMed1996

Glutamine.

Glutamine is the most abundant free amino acid in the circulation. It is a primary fuel for rapidly dividing cells and plays a key role in the transport of nitrogen between organs. Although glutamine is absent from conventional regimens aimed at nutritional support, glutamine deficiency can occur during periods of metabolic stress; this has led to the reclassification of glutamine as a conditionally essential amino acid. Experiments with various animal models have demonstrated that the provision of glutamine can result in better nitrogen homoeostasis, with conservation of skeletal muscle. There is also considerable evidence that glutamine can enhance the barrier function of the gut. This review concludes by discussing the clinical evidence that supports the inclusion of stable forms of glutamine in solutions of nutrients.

Enteral Nutrition↗
PubMed1996

Peritoneal defences and peritoneum-associated lymphoid tissue.

The peritoneum is mainly protected by the innate immune system. This consists of mechanical clearance of the peritoneal cavity, activation of complement, and the actions of polymorphonuclear neutrophils and macrophages. The specific immune system, which is mediated by the activity of lymphocytes, provides a secondary amplification system that may be of great importance for patients with intraperitoneal sepsis. This review provides an overview of the relevant innate immune mechanisms and explores the possible role of peritoneum-associated lymphoid tissue.

Ascitic Fluid↗