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Biomedical subjects

A Hall

Publications and source records attributed to A Hall.

At least 379 records · Page 21Linked to original sources
PubMed1987

Toxicity of Cyclamen persium (Mill).

Cyclamen spp contain toxic saponins, although the number of serious exposures is very low. The plant was investigated for toxic and pharmacologic properties in the 1950's and 1960's, but there is little current investigation. Cyclamens have been found both as woodland plants and houseplants in Europe for years, and the plant is becoming increasingly popular in the US. Poison centers should be aware of the potential toxicity of this plant, especially that of the rhizomatous tubers. Additional data on exposures reported to poison centers may be helpful in further defining the toxicity of this plant.

Humans↗
PubMed1986

The effect of Mg2+ on the guanine nucleotide exchange rate of p21N-ras.

There is growing evidence that the protein products of the ras gene family, p21ras, can couple growth factor receptors to intracellular second messenger production and in particular to phosphoinositol lipid turnover. So far, however, there has been no direct proof that the ras proteins function as typical regulatory G proteins. We show here that the human p21N-ras protein, isolated from an Escherichia coli expression system, can exist as a stable GDP complex which exchanges very slowly with exogenous GTP, the half-life of the p21N-ras X GDP complex being around 20 min. However, in low Mg2+ (0.5 microM) the exchange rate is dramatically increased and the half-life of the p21N-ras X GDP complex is less than 30 s. Furthermore, in low Mg2+, the relative binding affinity of the protein for GTP as compared to GDP is increased 10-fold. The effect of low Mg2+ on the exchange rate of both normal and oncogenic mutant p21ras molecules is identical. We propose that removal of Mg2+ in vitro induces a similar conformational change to stimulation in vivo. The properties described here are consistent with a G protein-like activity for p21N-ras.

Escherichia coli↗
PubMed1986

Enkephalin-like substance in aplysia nervous tissue and actions of leu-enkephalin on single neurons.

Extract from the abdominal ganglia of Aplysia was fractionated by high performance liquid chromatography. Several large uv absorbing peaks were found. One of these peaks from the ganglionic extract was analyzed by displacement assay with the use of Mytilus edulis membranes. The results revealed the substance in this peak was able to displace 3H-D-Ala2, met5-enkephalinamide. In electrophysiological studies of abdominal and cerebral neurons, depolarizing and hyperpolarizing responses were obtained from some neurons, including neurons in the identified cerebral B cell cluster. A smaller population of cells exhibited biphasic responses. Some of the responses could be depressed by prior naloxone treatment. In conclusion, an endogenous opioid system, using substance related to but distinct from the enkephalins, may exist in Aplysia.

Animals↗
PubMed1986

A survey of computer usage amongst Auckland general practitioners.

Auckland general practitioners were surveyed to assess their use of computers. Forty-eight practitioners (9.6%) had computers which were primarily used for practice administration. The main benefit offered by the computer was an improvement in quality of work rather than a reduction in quantity. Areas of dissatisfaction revealed by the survey included cost, limited flexibility, and the consequences of computer failure. Although most respondents suggested improvements in specific areas, many felt that the age of computerised general practice had arrived.

Adult↗
PubMed1986

Transformation and stimulation of DNA synthesis in NIH-3T3 cells are a titratable function of normal p21N-ras expression.

A plasmid has been constructed which contains the normal human N-ras proto-oncogene under the transcriptional control of the steroid-sensitive promoter of the mouse mammary tumor virus long terminal repeat. This plasmid has been introduced into NIH-3T3 cells producing a clone of cells, T15, which is phenotypically normal in the absence of the transcription inducer, dexamethasone, and transformed when treated with high levels of the inducer. At lower levels of dexamethasone, both morphological transformation and stimulation of DNA synthesis are titratable functions of p21N-ras levels. T15 cells have been used to demonstrate that: (i) a 20- to 50-fold over-expression of normal p21ras is required for complete cellular transformation, (ii) p21N-ras expression induces DNA synthesis and the effect can be amplified by epidermal growth factor, (iii) moderate increases in normal p21ras expression can influence cell behaviour.

Animals↗
PubMed1986

Effects of restraint stress on voluntary ethanol intake and ulcer proliferation in rats.

The present study examined the effect of exposure to a schedule of predictable restraint stress on voluntary ethanol consumption and ulcer proliferation in rats. Following ethanol screening rats were divided into high, medium and low ethanol consuming groups on the basis of daily ethanol intake (g/kg/day) and exposed to daily 1 hr restraint stress for 10 consecutive days. Voluntary ethanol consumption was monitored both during the stress period and for an additional 25 days post-stress. Stomach pathology was assessed on days 1, 5 and 10 of the stress period as well as at the conclusion of the post-stress period. Results indicated a differential effect of stress on ethanol intake in that high ethanol preferring rats consumed less ethanol in the first 5 days of the post-stress period as compared to non-stressed controls. In contrast, the medium ethanol preferring group drank more ethanol than controls during days 1-5 of the post-stress period. Ethanol consumption for the low ethanol groups did not change during the entire experiment. Stomach pathology data revealed no ulcer formation in the stressed groups during the stress period. At the end of the post-stress period, however, stressed animals exhibited a significantly greater ulcer severity (mean cumulative ulcer length) and ulcer frequency (mean number of ulcers per rat) than non-stressed groups. Stomach pathology for ethanol consuming groups did not differ from controls, indicating that ethanol did not, by itself, affect ulcer development.

Alcohol Drinking↗
PubMed1986

Investigation of 'weight pathology' of 58 mothers of anorexia nervosa patients and 204 mothers of schoolgirls.

'Weight pathology'--defined by Kalucy et al. (1977) as 'deviations in weight, shape, eating behaviour and activity'--has been hypothesized to be unduly common in families with anorexia nervosa. It was investigated in this study by means of questionnaires evaluating both weight history and attitudes towards weight-related matters in 58 mothers of anorexia nervosa patients and 204 mothers of schoolgirls of similar age and socioeconomic status (SES). No support was found for the hypothesis. A family history of aberrant weight and mother's current weight and past weight histories showed no significant differences between the groups. 142 other mothers of schoolchildren and 446 attenders at Weight Watchers also completed the questionnaire on attitudes towards weight-related matters. Mothers of patients showed a lower concern on all scales than did all other groups. The findings are discussed in relation to earlier controlled studies of family factors in anorexia nervosa.

Adolescent↗
PubMed1986

Malignant transformation of murine fibroblasts by a human c-Ha-ras-1 oncogene does not require a functional epidermal growth factor receptor.

Although mutations in ras genes are thought to be important for the development of about 20% of human tumors, almost nothing is known about the way in which these mutations lead to cellular transformation. The known biochemical properties of the 21-kilodalton ras proteins suggest that they may behave as G proteins, regulating the proliferation of cells in response to growth factor stimulation of a receptor. Although the putative receptor(s) has not been identified, several lines of evidence, in particular the fact that rodent cell lines containing ras oncogenes produce transforming growth factor alpha, have suggested that the epidermal growth factor (EGF) receptor is involved in ras transformation. Here we show that murine fibroblasts with no EGF receptors can be transformed to a completely malignant phenotype with a mutated ras gene. It appears, therefore, that the EGF receptor is not required for ras-mediated transformation of these cells.

Animals↗
PubMed1986

Quantitative analysis of intracranial circulation using rapid-sequence DSA.

By using a high-frame-rate technique, intravenous digital subtraction angiography (IVDSA) of the intracranial circulation was performed in patients with transient ischemic attacks and asymptomatic bruits. Twenty patients with normal carotid arteries or mild stenosis of no hemodynamic significance were selected as a control group to evaluate the effect of carotid stenosis on the difference between hemispheres in the peak arrival time (delta TMAX) of the contrast bolus. Data were obtained for the anterior (ACA), middle (MCA), and posterior (PCA) cerebral artery distributions. Raw data of the time-density curve in a region of interest were analyzed by polynomial curve-fitting techniques to obtain the peak arrival time (TMAX). The delta TMAXs for normal middle, anterior, and posterior distributions were 0.140 +/- 0.119 sec, 0.152 +/- 0.146 sec, and 0.189 +/- 0.187 sec, respectively. Eleven patients with tight carotid stenosis or occlusion whose delta TMAX fell outside the normal range as established from the 20 control patients were analyzed with regard to ischemic symptoms. The delta TMAXs of the MCA, ACA distributions in the asymptomatic patients with tight carotid stenosis or occlusion were 0.653 +/- 0.379 sec and 0.118 +/- 0.159 sec, respectively; p less than 0.001 in the MCA when compared with controls. The delta TMAXs of the MCA, ACA distribution in the symptomatic patients with tight carotid stenosis or occlusion were 1.31 +/- 0.13 sec and 0.525 +/- 0.079 sec, respectively; p less than 0.001 in the MCA and ACA distributions when compared with controls. Quantitative analysis of this type of physiologic data may enable the detection of patients with carotid stenosis who are well compensated by collateral flow from those who are poorly compensated and at risk for possible infarction on a hemodynamic basis. Serial followup DSA studies in patients with asymptomatic bruits may help to correlate the progression of extracranial carotid stenosis and the status of intracranial collateral reserves.

Adult↗
PubMed1985

Human N-ras: cDNA cloning and gene structure.

The structure and organisation of the human N-ras gene has been determined by analysing cDNA clones derived from the two main mRNA transcripts. One clone in particular is 4.1 Kb long and originates from the larger (4.3 Kb) message. Sequence analysis of this clone has revealed that the N-ras gene consists of seven exons. A second clone deriving from the smaller (2 Kb) message shows that the difference between the two transcripts is a simple extension through the termination site of the 2 Kb transcript. Using S1 analysis, two transcriptional starts have been mapped, 10 bp apart. There is no obvious TATA box in the expected promoter region of the gene, though there are 4 GGGCGG sequences surrounding the start sites. The 5' untranslated sequence contains 2 ATGs upstream of the initiation codon.

Amino Acid Sequence↗
PubMed1985

Serious illness in 204 New Zealand families during a 16 year period.

Mothers of 204 senior school pupils completed a questionnaire about serious illness in nuclear family members during the lifetime of each adolescent. The information provided was sufficiently detailed to estimate incidence of various types of illness, to categorise illness by degree of seriousness and to compare illness histories between families. Gynaecological conditions in mothers and accidents and infectious diseases in children were the most common serious illness; asthma was reported in 7% of the individuals (27% of families). There had been 17 deaths, 31 life threatening illnesses, 108 major illnesses (defined as at least one week in hospital for a medical condition or for major surgery), 150 serious but non-major illnesses and 84 episodes of minor surgery. Six percent of families reported 36% of the medically serious illnesses.

Accidents↗