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Biomedical subjects

J Griffiths

Publications and source records attributed to J Griffiths.

At least 19 recordsLinked to original sources
PubMed1992

Exogenous chromophores for the argon and Nd:YAG lasers: a potential application to laser-tissue interactions.

Chromophore dyes can be employed to modify laser-tissue interaction. A number of dyes have been investigated for their effect on the absorption and transmission of argon and Nd:YAG laser energy by vascular tissue in vitro. Three histological dyes have been assessed as potential chromophores for the argon laser and four infrared dyes for the Nd:YAG. Segments of porcine coronary artery to which dye had been applied were lased (1,064 nm, 2.5 W, 83 W/cm2, 60 s and 488/514 nm, 400 mW, 10.5 W/cm2, 60s) and the tissue temperature measured remotely using an infrared thermometer. In addition, energy transmission was measured with a photodiode and tissue morphological changes assessed histologically. All three argon dyes significantly increased energy absorption (typically 60 degrees C v. 20 degrees C at 60 s, P less than 0.001, 2-way ANOVA). Three of the four infrared dyes behaved similarly (40-70 degrees C v. 20 degrees C, P less than 0.001). All dyes significantly increased the initial rate of rise in tissue temperature during lasing. A reduction in energy transmission was observed for each of the Argon dyes but not for the Nd:YAG dyes. Histological evidence of thermal damage in control tissue first occurred for the argon and Nd:YAG lasers at 800 mW and 7.5 W without chromophore and at 400 mW and 2.5 W with the chromophore, respectively. A number of effective chromophores have therefore been identified at each wavelength.

Absorption↗
PubMed1992

Strain-specific alterations in consumption of a palatable diet following repeated stressor exposure.

Exposure to acute inescapable shock caused reductions in the consumption of a highly palatable diet. The magnitude and duration of the reduction varied across strains of mice. With repeated exposure to footshock, consumption of the diet returned to baseline levels, although alterations of weight appeared to be more persistent. The course of the adaptation varied across strains of mice; however, the rate of adaptation was unrelated to the extent of the alterations of consumption induced by the acute stressor. When mice were exposed to a series of different stressors, the adaptation progressed less readily, and reductions of diet consumption were apparent in strains that had not shown such an effect following acute stressor application or when repeatedly exposed to a single type of stressor. Data were discussed with respect to the mechanisms that might be operative in subserving stressor-induced anhedonia.

Animals↗
PubMed1992

Different techniques of residual composite removal following debonding--time taken and surface enamel appearance.

Four different methods of in vitro residual composite removal following debonding performed by two different operators (an orthodontist and a hygienist) were assessed for enamel surface damage (using scanning electron microscopy) and the time involved. There was no difference in the quality of enamel surface appearance between the two operators, regardless of the method used for composite removal. There was a statistically significant difference (P less than 0.05) for the time taken for composite removal between the two operators using a tungsten carbide bur method only. It is suggested that an expanded duties auxiliary with the practical skills of the hygienist would be able to remove residual composite debris and produce a satisfactory polished enamel surface using tungsten carbide burs and aluminium oxide polishing discs, thus becoming a safe and cost-effective member of the orthodontic team.

Composite Resins↗
PubMed1992

Automation and other recent developments in clinical chemistry.

The decade 1980 to 1990 was the most progressive period in the short, but turbulent, history of clinical chemistry. New techniques and the instrumentation needed to perform assays have opened a chemical Pandora's box. Multichannel analyzers, the base spectrophotometric key to automated laboratories, have become almost perfect. The extended use of the antigen-monoclonal antibody reaction with increasing sensitive labels has extended analyte detection routinely into the picomole/liter range. Devices that aid the automation of serum processing and distribution of specimens are emerging. Laboratory computerization has significantly matured, permitting better integration of laboratory instruments, improving communication between laboratory personnel and the patient's physician, and facilitating the use of expert systems and robotics in the chemistry laboratory.

Automation↗
PubMed1992

An alternate origin for the placental isoenzyme of alkaline phosphatase.

By means of an electrofocusing technique, the serum specimens of pregnant women routinely revealed three bands of alkaline phosphatase (ALP) that were released by placental syncytiotrophoblast, germ cell (ovary), and fetal intestine at pl of 4.73, 4.65, and 4.55, respectively. When defining reference ranges for ostensibly healthy persons of all decades of age and investigating patients with elevated total ALP activity, we found the isoenzyme at pl 4.73 to be above the established reference range in some nonpregnant women and in men. Evidence suggests that T lymphocytes from whole blood or in vivo tissue were the origin of this pl 4.73 ALP band; the isoenzyme being released during cell lysis, in cellular turmoil from any cause, or when active cell division occurs. A designation of lymphocyte ALP is proposed for this ALP band that is observed in a broad group of diseases associated with abnormal lymphocyte function.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Steroid-eluting epicardial leads in pediatrics: improved epicardial thresholds in the first year.

From 1986 to 1991, we evaluated the clinical use of three new epicardial lead designs incorporating a steroid-eluting electrode. Medtronic models SP2114 (bipolar high profile), 10320 (bipolar low profile), 10295A/4965 (unipolar low profile) steroid epicardial (SE) leads were used on either atrium or ventricle for a total of 21 lead placements in 17 patients. Energy thresholds (T) were calculated and compared with our most recent 16 nonsteroid epicardial (NE) Medtronic model 4951 lead implants for which T was available. SE leads demonstrated no acute T rise and continued T improvements at 1 year of follow-up. We conclude that epicardial application of SE lead technology offers a major improvement in pacing lead function and potential pacemaker longevity over NE leads in pediatric patients in whom endocardial pacing is precluded by size or anatomy.

Animals↗
PubMed1990

Mouse strain differences in plasma corticosterone following uncontrollable footshock.

Exposure to acute inescapable footshock provoked marked increases of plasma corticosterone concentrations in six strains of mice (A/J, Balb/cByJ, C57BL/6J, C3H/HeJ, DBA/2J and CD-1). However, the magnitude of the increase, as well as the time required for corticosterone to return to control values, varied appreciably across strains. Moreover, it appeared that the strain-specific corticoid increases ordinarily observed after acute shock were also evidence following a chronic stressor regimen. The data were related to previously observed strain differences in stressor-induced alterations of brain norepinephrine, dopamine and serotonin, as well as variations in performance in several behavioral paradigms.

Animals↗
PubMed1989

Management of supracondylar fractures of the femur with Zickel supracondylar nails.

Twenty-one cases of supracondylar fracture of the femur treated at St Vincent's Hospital, Melbourne, during 1983-86, by intramedullary Zickel supracondylar nails were reviewed. The causes were high energy trauma in young patients (six), minor trauma in elderly patients (13), and metastatic malignant fracture (two). The functional results were considered excellent in 10, good in six and poor in five. There were two cases of superficial wound infection. All cases united after 3-6 months. The best functional results were in those patients below 60 years or with pathological fractures. It is concluded that internal fixation of supracondylar fractures of the femur with Zickel supracondylar nails is a successful technique and can be performed by open and closed methods. It is most useful in osteoporotic or pathological bone which is unsuitable for bone plating.

Aged↗
PubMed1989

Alkaline phosphatases. Newer concepts in isoenzymes and clinical applications.

ALP is a profoundly ubiquitous enzyme that originates in many, if not all, mammalian tissues. The development of a simple ISEF technique has allowed reflection of at least 12 cellular components. Improvements in technique may add further zones of information. The aura of darkness surrounding ALP is being slowly dissipated.

Alkaline Phosphatase↗
PubMed1988

Role of retroviruses in acquired hypogammaglobulinaemia.

Mononuclear cells were obtained from 42 patients with 'common variable' hypogammaglobulinaemia (CVH) and co-cultured with various cell lines in an attempt to isolate retroviruses. Cultures from only two patients showed evidence of a viral infection, although the virus could not be isolated and characterized in either. Despite the previous isolation of HIV's from two other CVH patients, this data suggests that similar viruses are not etiologically involved in the majority of patients.

Adult↗
PubMed1987

Separation and identification of alkaline phosphatase isoenzymes and isoforms in serum of healthy persons by isoelectric focusing.

We have developed an isoelectric focusing procedure for resolving alkaline phosphatase (EC 3.1.3.1) isoenzymes and isoforms in serum. We use a thin-layer agarose gel film containing synthetic carrier ampholytes and a "separator" to flatten the pH gradient in the region of the isoenzyme and isoform isoelectric points. Sharp, highly resolved zones of enzyme activity are obtained by limiting diffusion; for this we rapidly couple the released product, 1-naphthol, to a diazonium salt, which forms a colored precipitate at the site of activity. We have resolved and identified 12 zones of alkaline phosphatase activity in the serum of ostensibly healthy persons within a wide age range. Theoretically, three basic isoenzymes are produced from independent gene loci: intestinal, placental, and nonspecific tissue alkaline phosphatase. The other zones of activity may be isoforms.

Adolescent↗