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Biomedical subjects

J C Austin

Publications and source records attributed to J C Austin.

At least 19 recordsLinked to original sources
PubMed1992

Substrate polarization by residues in delta 5-3-ketosteroid isomerase probed by site-directed mutagenesis and UV resonance Raman spectroscopy.

delta 5-3-Ketosteroid isomerase (KSI: EC 5.3.3.1) of Pseudomonas testosteroni catalyzes the isomerization of delta 5-3-ketosteroids to delta 4-3-ketosteroids by the stereospecific transfer of the steroid 4 beta-proton to the 6 beta-position, using Tyr-14 as a general acid and Asp-38 as a base. Ultraviolet resonance Raman (UVRR) spectra have been obtained for the catalytically active double mutant Y55F + Y88F, which retains Tyr-14 as the only tyrosine residue (referred to as the Y14(0) mutant), and the Y14F mutant, which has 50,000-fold lower activity. The UVRR results establish that binding of the product analog and competitive inhibitors 19-nortestosterone or 4-fluoro-19-nortestosterone to the Y14(0) mutant does not result in the formation of deprotonated Tyr-14. The UVRR spectra of the steroid inhibitors show large decreases in the vinyl and carbonyl stretching frequencies on binding to the Y14(0) enzyme but not on binding to the Y14F enzyme. These changes cannot be mimicked by protonation of the steroids. For 19-nortestosterone, the vinyl and carbonyl stretching frequencies shift down (with respect to the values in aqueous solution) by 18 and 27 cm-1, respectively, on binding to Y14(0) KSI. It is proposed that the changes in the steroid resonance Raman spectrum arise from polarization of the enone moiety via the close proximity of the charged Asp-38 side chain to the vinyl group and the directional hydrogen bond between Tyr-14 and the 3-carbonyl oxygen of the steroid enone. The 230-nm-excited UVRR spectra do not, however, show changes that are characteristic of strong hydrogen bonding from the tyrosine hydrogen. It is proposed that this hydrogen bonding is compensated by a second hydrogen bond to the Tyr-14 oxygen from another protein residue. UVRR spectra of the Y14(0) enzyme obtained using 200 nm excitation show enhancement of the amide II and S Raman bands. The secondary structure of KSI was estimated from the amide II and S intensities and was found to be low in alpha-helical structure. The alpha-helix content was estimated to be in the range of 0-25% (i.e., 10 +/- 15%).

Binding, Competitive↗
PubMed1989

An ultraviolet resonance Raman study of dehydrogenase enzymes and their interactions with coenzymes and substrates.

Ultraviolet resonance Raman (UVRR) spectra, with 260-nm excitation, are reported for oxidized and reduced nicotinamide adenine dinucleotides (NAD+ and NADH, respectively). Corresponding spectra are reported for these coenzymes when bound to the enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and liver and yeast alcohol dehydrogenases (LADH and YADH). The observed differences between the coenzyme spectra are interpreted in terms of conformation, hydrogen bonding, and general environment polarity differences between bound and free coenzymes and between coenzymes bound to different enzymes. The possibility of adenine protonation is discussed. UVRR spectra with 220-nm excitation also are reported for holo- and apo-GAPDH (GAPDH-NAD+ and GAPDH alone, respectively). In contrast with the 260-nm spectra, these show only bands due to vibrations of aromatic amino acid residues of the protein. The binding of coenzyme to GAPDH has no significant effect on the aromatic amino acid bands observed. This result is discussed in the light of the known structural change of GAPDH on binding coenzyme. Finally, UVRR spectra with 240-nm excitation are reported for GAPDH and an enzyme-substrate intermediate of GAPDH. Perturbations are reported for tyrosine and tryptophan bands on forming the acyl enzyme.

Alcohol Dehydrogenase↗
PubMed1989

Factors predicting failure of medical therapy for gastric ulcers.

We reviewed the charts of all patients admitted with a diagnosis of gastric ulcer from January 1970 to December 1980. Multiple risk factors were recorded in patients receiving medical treatment and compared in those patients successfully treated medically versus those requiring operation after a failed course of medical treatment. One hundred patients were treated medically without surgical intervention, and 34 patients underwent operation after medical therapy failed. Significant risk factors in patients requiring operative therapy included smoking (p = 0.03), multiple trauma and sepsis (p = 0.02), large ulcers (p = 0.03), and multiple ulcers (p = 0.02). We have identified a set of factors associated with a high risk of failure of medical therapy. Patients with any of these risk factors may be treated most effectively by a limited trial of medical therapy with close follow-up. If their ulcer disease does not respond readily to standard medical therapy, they should be considered for early elective surgery.

Emergencies↗
PubMed1988

Vaterian cancer in siblings.

The simultaneous occurrence of Vaterian carcinoma in two siblings suggests a genetic influence in their pathogenesis. Their classic clinical presentation of obstructive jaundice and weight loss required pancreaticoduodenectomy for this neoplasm. Pedigree analysis revealed a third sibling who died from an unresectable periampullary malignancy. Neither of the probands exhibited, as late as the seventh decade, evidence compatible with a diagnosis of familial polyposis coli or Gardner's syndrome. Flow cytometry studies revealed an aneuploid distribution in one tumor and tetraploid in the other. The rarity of this neoplasm, in the absence of contributing epidemiologic factors, suggests that this is a pleotrophic manifestation of a cancer-prone genotype.

Adenocarcinoma↗
PubMed1978

Histologic response of replanted teeth pretreated with acidulated sodium fluoride.

Central incisors in the vervet monkey were extracted, endodontically treated, and replanted into their original sockets after immersion in a 2 per cent acidulated sodium fluoride solution (pH 5.5) for 30 minutes. Histologic examination at 1, 2, 4, and 8 weeks postoperatively showed that by the second week resorption had taken place and that ankylosis, first seen by the fourth week, along both the buccal and palatal root surfaces, was well established by the eighth week. Under the conditions of the study, pretreatment of the tooth roots with 2 per cent acidulated sodium fluoride did not reduce root resorption and ankylosis.

Acids↗
PubMed1978

Nitrous oxide contamination in dental surgeries using relative analgesia.

The concentrations of nitrous oxide were determined at various positions in four dental surgeries in which nitrous oxide sedation was used without scavenging. Contamination was present in all the surgeries, the greatest concentration being recorded at the dentist's nose and the least in the peripheral air. The reception area adjoining the surgeries was found also to be contaminated by nitrous oxide.

Air Pollutants↗
PubMed1978

Comparison of sampling techniques for studies of nitrous oxide pollution.

The retention of nitrous oxide in samples of nitrous oxide in air held in disposable plastic syringes, glass syringes and custom-made nylon film bags was studied by means of gas chromatography at intervals of 90 min, 24, 48 and 120 h after filling the containers. After 24 h the nylon bags retained a mean concentration of 94.5% of the original concentration of nitrous oxide. The disposable plastic syringes and glass syringes were unsatisfactory and retained only 80% of the original concentration of nitrous oxide after 90 min. These values decreased to 51% and 31% of the original concentration of nitrous oxide respectively at 24 and 48 h.

Air Pollution↗
PubMed1978

The role of laboratory animals in dental research.

In dental research, in common with other forms of scientific research, the use of laboratory animals is necessary to carry out many investigations that may not be undertaken on man, and to control biological variability. In South Africa the main experimental animals used in dental research are rats and vervet monkeys, although other species such as dogs and baboons have been used. This paper lists examples of published dental research carried out in laboratory animals in South Africa in the fields of bone healing, dental caries, dental materials, growth studies, oral cancer, oral mucosa and periodontal disease investigations.

Animals↗
PubMed1978

Current status and future options for the development of laboratory animal technology and the training of laboratory animal technicians.

Laboratory animal technology has evolved into a specialised field of expertise which is associated with the production, care and use of laboratory animals in biomedical teaching and research. A survey of laboratory animal facilities and supporting personnel was undertaken to assess the uses of laboratory animals in relation to the administrative and technical staffing of animal facilities. The results of this study indicate that there is a need for training in laboratory animal science at both the technical and professional levels. Options for the development of formal training in laboratory animal technology are reviewed.

Academies and Institutes↗
PubMed1978

The Japanese quail (Coturnix coturnix japonica) as a laboratory animal.

The use of the Japanese quail as a laboratory animal was first reported in 1959. Since then this species has been increasingly used as an avian model for biomedical research. A quail colony was recently established in the Dental Research Institute to provide adult birds for teratogenicity and toxicity studies. These birds are not widely used for biological research in South Africa at present. The housing, husbandry, breeding and nutrition of this species is described, together with the biomethodology which is applicable to this species.

Animal Husbandry↗
PubMed1978

Design and use of an inhalation chamber for air pollution studies in small animals.

Environmental chambers provide a convenient means of studying the toxicology of gases in experimental animals. The specialised equipment needed for these studies is not commercially available. This paper reports on the design, construction and performance of a simple, and inexpensive, inhalation chamber and gas mixing unit for air pollution studies in small laboratory animals. Provision has been made for controlling the mixing of gases, the ventilation rate, the even distribution of gases in the chamber and for the removal of vented gases to prevent the hazard of air pollution in the laboratory animal facility. No significant differences were found between the food and water consumption and body mass gain of a group of rats housed in the chamber for 5 days and a control group housed im similar cages located in a rodent room and managed under conventional laboratory conditions. The chamber fulfills all the requirements for an animal inhalation system.

Air Pollutants↗
PubMed1977

The effect of a proteolytic enzyem mixture (Orenzyme-Forte) on experimentally induced pulpitis.

A proteolytic enzyme mixture, Orenzyme-Forte, containing trypsin, chymotrypsin, and ribonuclease was used to treat experimentally induced pulpitis in the teeth of three monkeys. Assessment by means of the criteria of Stanley showed that the enzyme mixture induced better healing than a zinc oxide--eugenol dressing. When the two were used simultaneously, a synergistic effect was seen. We suggest that this enzyme mixture may be useful in clinical practice in the treatment of pulpitis.

Animals↗