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Biomedical subjects

C A Hall

Publications and source records attributed to C A Hall.

At least 19 recordsLinked to original sources
PubMed2003

Use of a wave reverberation technique to infer the density compression of shocked liquid deuterium to 75 GPa.

A novel approach was developed to probe density compression of liquid deuterium (L-D2) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22-75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.

Journal Article↗
PubMed2003

Estimation of actinide skeletal content in humans based on bone samples collected at autopsy.

The USTUR has developed simple linear and multiple regression models for estimating skeletal actinide concentrations on the basis of bone samples collected at autopsies of non-whole body tissue donors. Bone samples usually collected include a clavicle, the patella(e), one or more ribs, the sternum, and a vertebral wedge cut from within the abdominal cavity. The described models were derived by regression analyses with the analytical results from those bones and the entire skeletons of eight whole body donations to the USTUR. With the model, skeletal concentrations of 238Pu, (239+240)Pu, and 241Am can be estimated from wet or ashed actinide concentrations in one to five of the bones usually collected at autopsy and analyzed. Application of the models to a selected USTUR non-whole body donation (Case 0240) indicated that the skeletal actinide concentration estimates were reasonably precise and that there was good agreement between the results from individual bones with wet or ashed actinide concentrations. The USTUR will apply the model that is based on wet concentrations of bones to estimate skeletal concentrations of actinides in all non-whole body autopsy cases for the sake of consistency because of the large number of early cases for which ashed weights of bones were not recorded.

Actinoid Series Elements↗
PubMed2003

The effect of stimulus height on visual discrimination in horses.

This study investigated the effect of stimulus height on the ability of horses to learn a simple visual discrimination task. Eight horses were trained to perform a two-choice, black/white discrimination with stimuli presented at one of two heights: ground level or at a height of 70 cm from the ground. The height at which the stimuli were presented was alternated from one session to the next. All trials within a single session were presented at the same height. The criterion for learning was four consecutive sessions of 70% correct responses. Performance was found to be better when stimuli were presented at ground level with respect to the number of trials taken to reach the criterion (P < 0.05), percentage of correct first choices (P < 0.01), and repeated errors made (P < 0.01). Thus, training horses to carry out tasks of visual discrimination could be enhanced by placing the stimuli on the ground. In addition, the results of the present study suggest that the visual appearance of ground surfaces is an important factor in both horse management and training.

Animals↗
PubMed2001

Equation of state measurements in liquid deuterium to 70 GPa.

Using intense magnetic pressure, a method was developed to launch flyer plates to velocities in excess of 20 km/s. This technique was used to perform plate-impact, shock wave experiments on cryogenic liquid deuterium ( L-D(2)) to examine its high-pressure equation of state. Using an impedance matching method, Hugoniot measurements were obtained in the pressure range of 30-70 GPa. The results of these experiments disagree with previously reported Hugoniot measurements of L-D(2) in the pressure range above approximately 40 GPa, but are in good agreement with first principles, ab initio models for hydrogen and its isotopes.

Journal Article↗
PubMed2001

Prevalence survey of multiple sclerosis in the Australian Capital Territory.

AIM: This study sought to obtain an estimate of the prevalence of multiple sclerosis (MS) in the Australian Capital Territory (ACT), a largely urban region that differs climatically and socioeconomically from other Australian cities examined in previous MS surveys. METHODS: Prevalence day was chosen to coincide with the 1996 National Census. All ACT neurologists' records for the previous 5 years were examined and cases of MS were classified according to the published diagnostic criteria of Rose et al. and Poser et al. RESULTS: By the criteria of Rose et al., as used in previous Australian surveys of MS, prevalence was 79.9/100,000 (95% confidence interval (CI) = 63.4-99.2) for females, 32.8 (22.7-46.2) for males and 56.7 (43.1-74.1) for all people, standardized to the 1996 population. Standardized to the 1981 population for direct comparison with 1981 surveys in New South Wales, the prevalence of MS in the ACT was still unexpectedly high, particularly for females. Using the criteria of Poser et al., the prevalence of MS standardized to the 1996 population was 70.6/ 100,000 (95% CI = 58.4-85.3) for females, 28.0 (20.3-37.8) for males and 49.5 (42.2-58.2) for all people. There was evidence from a relatively short duration of disease in the ACT sample that some persons with long-standing MS had been missed in the survey and therefore that the prevalence of MS observed in the ACT was an underestimate. CONCLUSIONS: The survey found an unexpectedly high prevalence of MS in the ACT. Possible reasons for this are discussed. There was no evidence that the advent of magnetic resonance imaging had increased the numbers of persons diagnosed with MS in the present survey.

Adolescent↗
PubMed1998

Food-bound B12 absorption and serum total homocysteine in patients with low serum B12 levels.

This study was undertaken to determine whether measurements of serum total homocysteine (Hcys) and bound B12 absorption are useful in determining which patients with low- or low-normal levels of serum B12 are B12 deficient. In 40 patients with low or borderline serum levels of B12, food-bound B12 absorptions were determined using a body counter in an iron room, and were related to serum total Hcys levels. Food-bound B12 absorption was decreased in 16 patients and in an additional four, absorption of the free vitamin was also decreased. Homocysteine levels were elevated in four of the 16; in three of the four who had both decreased bound and free B12 absorptions, Hcys was elevated. If elevation of the Hcys level indicates tissue deficiency of B12, the 75% incidence of normal levels of Hcys in these patients with low food-bound B12 absorptions suggests the existence of a cohort of patients who may be at risk to develop, but have not yet developed, B12 deficiency. Only long term follow-up will reveal how many ultimately will become B12 deficient.

Adult↗
PubMed1997

Patient management in head injury care: a nursing perspective.

Through a review of the literature, this article provides a consideration of nursing responsibilities and nursing care in the management of patients with head injuries. A brief review of the pathophysiology of head injury is followed by a description of intracranial pressure (ICP) monitoring and cerebral perfusion pressure (CPP) measurement, using the Camino fibreoptic catheter and monitor, with exploration of pulse and trend waveforms and their significance in assessing cerebral compliance. Jugular venous bulb saturation (SjO2) monitoring adds another dimension to the assessment of neurological damage by demonstrating cerebral tissue perfusion and cerebral metabolic rate, and this is also discussed. After identification of assessment as a crucial part of the nursing role, aspects of nursing care of head-injured patients are discussed. The discussion of respiratory support measures includes the controversial use of hyperventilation in reducing ICP, the prevention of hypoxia, the risk of respiratory complications, the use of suctioning and turning to prevent these and the problems associated with these nursing care measures. Other aspects of care are also considered, including careful positioning and temperature control, and the benefits of mild hypothermia.

Blood Gas Analysis↗
PubMed1994

Physiotherapy in the treatment of temporomandibular joint disorders: a comparative study of four treatment methods.

Temporomandibular joint pain dysfunction syndrome (TMJPDS) comprises of a constellation of signs and symptoms including joint tenderness and pain on function, restricted jaw movement, clicking, jaw locking and tenderness in the muscles of mastication. Headache may also be a feature. Physiotherapy is commonly employed in the treatment of this condition but there is little published material reporting the relative efficacy of the different types of treatment currently available. Further, no attempt seems to have been made to compare the costs of physiotherapy with other forms of treatment of this disorder such as occlusal splint therapy. This paper reports a comparative evaluation of four different physiotherapy treatments and placebo in the management of TMJPDS and comments on their cost benefit aspects compared with that of splint therapy. The four methods of physiotherapy tested were short-wave diathermy, megapulse, ultrasound and soft laser. There was no statistically significant difference in success rate between any of the four tested (range 70.4-77.7%) although each individually was significantly better than placebo treatment. The time of improvement appeared to vary between the four methods.

Chi-Square Distribution↗
PubMed1994

Delayed-type hypersensitivity anergy in human immunodeficiency virus-infected persons screened for infection with Mycobacterium tuberculosis.

A total of 479 human immunodeficiency virus (HIV)-infected persons at an HIV clinic in Florida and a tuberculosis clinic in New Jersey were skin-tested with tuberculin, tetanus toxoid, mumps antigen, and Candida antigen in a study of the prevalence of delayed-type hypersensitivity (DTH) anergy and the usefulness of two-step tuberculin testing in this population. Of the patients tested, 12% had a positive (> or = 5-mm) response to tuberculin; 57%, 45%, and 35% had a positive (> or = 3-mm) response to Candida antigen, tetanus toxoid, and mumps antigen, respectively; and 31% were anergic (< 3 mm of induration in response to each antigen). In a multivariate logistic regression model, anergy was significantly associated with a history of Kaposi's sarcoma, Pneumocystis carinii pneumonia, or oral candidiasis and with White race. Anergy was four times and 15 times as likely for persons with CD4+ T-lymphocyte counts of 200-400/mm3 and < 200/mm3, respectively, as for persons with > 499 CD4+ T lymphocytes/mm3. Of 103 patients who were tuberculin-tested a second time after their initial test result was negative, seven had > or = 5 mm of induration in response to the second test; only one of these patients was anergic at the initial screening. The findings of this study indicate that DTH antigens should be used in conjunction with tuberculin testing and that two-step tuberculin testing is not an alternative to anergy testing but may be useful for the detection of infection with Mycobacterium tuberculosis in nonanergic HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed1993

Cobalamin metabolism in cultured human chorionic villus cells.

Cobalamin (Cbl, vitamin B12) metabolism was analyzed in cultures of human chorionic villus (CV) cells obtained at 9-10 weeks of gestation. CV cells were shown to synthesize transcobalamin II (TCII) and to possess a high affinity receptor for that molecule. The cells bound and internalized radioactive cyanocobalamin (CN[57Co]Cbl) complexed to TCII. This internalized CN[57Co]Cbl was found to be converted to both methylCbl and adenosylCbl, the two intracellular coenzyme forms of Cbl, and bound to the two known intracellular Cbl requiring enzymes, methionine synthase (MS) and methylmalonyl-CoA mutase. Both enzyme systems were found to be functional in the intact cell by demonstrating the incorporation of the radioactive label from both [14C]CH3-tetrahydrofolate and [14C]propionate into acid insoluble products. MS activity was also detected in lysed cell material. CV cells were shown not to be auxotrophic for methionine since they were able to utilize homocysteine in place of methionine for cell division. Since CV cells are capable of performing many of the complex events associated with Cbl metabolism, it may be possible to use these cells to diagnose genetic defects of Cbl metabolism.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1993

The methylcobalamin metabolism of cultured human fibroblasts.

The effect of supplying exogenous methylcobalamin (MeCbl), a methyl donor to methionine synthase (MS), on the cellular metabolism of MeCbl was tested in cultured fibroblasts from healthy persons and from a subject with an inherited defect in the synthesis of MeCbl. MeCbl bound to transcobalamin II (TCII) was taken up in larger amounts than cyanocobalamin (CN-Cbl), but was equal to the uptake of hydroxocobalamin (OH-Cbl). The form of Cbl in the lysosomes persisted as the same form, bound to TCII, to which the cells were exposed in the medium. Once released from the lysosomes, both MeCbl and OH-Cbl were converted in the same proportions to coenzyme forms, suggesting equivalent entry into common cellular pools of Cbl from which active forms are synthesized. Exogenous MeCbl enjoyed no advantage in binding to MS, in synthesis of MeCbl, and in supporting cell division in the absence of methionine. All evidence supported the concept that in human cells the active MeCbl on MS forms de novo on the enzyme. It appeared unlikely that therapeutic MeCbl would have any advantage over OH-Cbl in the treatment of MeCbl deficiency or Cbl deficiency in general.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1992

Heterogeneity in cblG: differential retention of cobalamin on methionine synthase.

Cultured fibroblasts from patients with functional methionine synthase deficiency have been shown to belong to two complementation classes, cblE and cblG. Both are associated with decreased intracellular levels of methylcobalamin (MeCbl) and decreased incorporation of label from 5-methyltetrahydrofolate into macromolecules. Methionine synthase specific activity is normal or near normal in cell extracts from cblE patients under standard reducing conditions, whereas specific activity is low in cblG extracts. Seven of 10 cblG cell lines accumulated [57Co]CN-Cbl equivalent to control cells and showed similar proportions of label associated with the two intracellular cobalamin binders, methionine synthase and methylmalonyl-CoA mutase. The remaining three cblG lines showed reduced accumulation of labeled Cbl and virtually none associated with methionine synthase. The specific activity of methionine synthase was decreased in cell extracts from both cblG subgroups, being almost undetectable in extracts from the latter three lines. Incorporation of label from [14C]MeTHF into either macromolecules or into methionine was decreased in both cblG groups, but was paradoxically higher in the three lines with very low in vitro methionine synthase activity. These results demonstrate further heterogeneity within cblG and suggest that the defect in the three variant lines affects the ability of methionine synthase to retain Cbl.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1992

The neurologic aspects of transcobalamin II deficiency.

Thirty-four symptomatic cases of inherited transcobalamin II (TCII) deficiency were analysed in order to determine the frequency and nature of neurologic manifestations. In no instance was there definite evidence of a neurologic disorder at the time of presentation as a young infant. One child of 2 1/2 years transiently lost deep tendon reflexes at a time of suboptimal treatment. A syndrome of mental retardation and other neurologic manifestations was observed in three cases, all with the following in common: (1) an extended duration of illness of 2-17 years; (2) inadequate or not treatment with Cbl; (3) treatment with folic of folinic acid. TCII deficiency rarely if ever presents with neurologic manifestations. However, neurologic disorders can be produced subsequently by improper treatment.

Central Nervous System Diseases↗
PubMed1992

Rescue angioplasty during myocardial infarction has a beneficial effect on mortality: a tenable hypothesis.

HYPOTHESIS: Rescue percutaneous transluminal coronary angioplasty (PTCA) reduces mortality during myocardial infarction. OBJECTIVE: To determine if PTCA after failed thrombolytic therapy results in reduced mortality. DESIGN: Twenty-eight patients with a persistently occluded infarct artery following thrombolytic therapy more than 3 h after symptom onset were randomized to rescue PTCA (n = 16) or conservative treatment (n = 12) as part of a prospective randomized trial of reperfusion therapy during myocardial infarction in 184 patients. Hospital mortality was assessed in these groups as well as in the 177 patients with known infarct artery status after initial attempts at reperfusion. MAIN RESULTS: There was one death among the 16 patients in the rescue PTCA group versus four deaths in the 12 patients treated conservatively (P = 0.13). Moreover, the death in the rescue PTCA group occurred in one of three patients in whom the procedure failed. Mortality in the entire study group was 10.3% (19 of 184); 4.2% (six of 142) in patients in whom patency was achieved after thrombolysis and/or PTCA and 34.3% (12 of 35) in those in whom reperfusion was not achieved (P less than 0.001). In patients with anterior myocardial infarction, mortality was 6.7% (four of 60) in those with reperfusion and 47.1% (eight of 17) in those with a persistently occluded artery (P less than 0.001). In patients with inferior myocardial infarction, 2.4% (two of 82) with reperfusion and 22.2% (four of 18) with a persistently occluded artery died (P less than 0.01). CONCLUSIONS: Although the number of patients in the randomized groups was small, the trend toward a lower mortality after rescue PTCA supports the hypothesis that rescue PTCA may be beneficial. The mortality results in relation to presence or absence of reperfusion from the entire study population underscores the importance of achieving patency during myocardial infarction.

Aged↗
PubMed1991

Transcobalamin II deficiency: case report and review of the literature.

A male Caucasian infant presented at 6 weeks of age with failure to thrive, diarrhoea, macrocytic anaemia, and decreased IgG. He had normal serum B12 and folate levels. Serum cobalamin binding capacity showed no detectable transcobalamin II. Both parents showed levels consistent with a heterozygous state. The literature is extensively reviewed, and the importance of early diagnosis to prevent neurological dysfunction is stressed.

Failure to Thrive↗