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Biomedical subjects

R T Jackson

Publications and source records attributed to R T Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Inhibition by astemizole of activity from the isolated semicircular canal.

Since astemizole does not readily pass the blood-brain barrier, it was surprising that it was found useful in patients with chronic vertigo. We therefore speculated that the drug may reach the inner ear and act directly on the sensory cell-afferent nerve synapse. Mice, injected with tritiated astemizole and killed 17 hours later, showed the presence of the drug in the vestibular tissues. Nerve recordings were made from the isolated posterior semicircular canal of the frog. Both spontaneous and stimulated firing rates were obtained with artificial perilymph containing astemizole bathing the isolated canal preparation. Results showed that astemizole has a significant inhibitory effect on vestibular nerve activity at concentrations of 10(-7) mol/L and higher. The exact site of astemizole's inhibitory action is undetermined but is most likely at the hair cell-afferent nerve synapse.

Animals↗
PubMed1987

Effect of bile salts on nasal permeability in vitro.

Nasal mucosa excised from dogs or rabbits was mounted as a flat sheet in an in vitro chamber. The permeability was assessed by measuring the unidirectional flux of the radiolabeled tracer compounds, water, sucrose, polyethylene glycol, and cholecystokinin octapeptide. The permeability coefficients calculated from the fluxes indicate that the nasal mucosa is moderately permeable to water-soluble compounds and compares with ileum or gallbladder. The addition of 0.5% sodium deoxycholate to the mucosal bathing solution caused a rapid, four- to fivefold increase in permeability to sucrose or cholecystokinin octapeptide. The increase in permeability was bidirectional, was not reversed by washing, and was accompanied by histological evidence of extensive loss of the surface epithelial layer. These results indicate that bile salts enhance nasal permeability by removing the epithelial cells, which constitute a major permeability barrier, rather than causing a chemical modification of the mucosal cells. This argues against the use of bile salts to enhance nasal drug absorption in patients.

Animals↗
PubMed1987

Underestimation of relative weight by use of self-reported height and weight.

Self-reported and measured height and weight were obtained from a representative sample of 1,598 persons in Auckland, New Zealand during 1982. The accuracy of the self-reported data and its effect on the misclassification of relative weight, as measured by Quetelet index, were examined. The finding that for most participants (75%), self-reported measures were no more than 3.5 cm from their measured height and 2.4 kg from their measured weight indicates that self-reports have a high degree of accuracy. However, the participants consistently overestimated their height and underestimated their weight, resulting in an underestimation of relative weight. This would have little effect on analyses using the self-reported relative weight measures as a continuous covariate, but misclassification would occur when using relative weight as a categorical variable. The sensitivities and specificities associated with categorized self-reported relative risks that have been calculated from relative weight derived from self-reported height and weight.

Adult↗
PubMed1985

The inhibition of norepinephrine release in nasal mucosa by acetylcholine.

Tritiated norepinephrine was incorporated into isolated dog nasal mucosa. Electrical stimulation of this mucosa induced a release of the tritiated norepinephrine. Acetylcholine inhibited this release in a dose-related manner. The inhibition is prevented by atropine. This data provides further evidence for the existence of presynaptic, inhibitory, muscarinic receptors on the sympathetic nerve terminals in nasal blood vessels.

Acetylcholine↗
PubMed1985

Influence of dietary cyanide on immunoglobulin and thiocyanate levels in the serum of Liberian adults.

Serum thiocyanate, antibody titers to thiocyanates, and serum immunoglobulins (IgM, IgG, IgA) were measured in 73 Liberian adults normally consuming diets of low, moderate, high, or no (control) cassava-derived cyanide (CN(-)). When control and low groups (n = 40; daily intake less than 0.60 mg CN(-) per kg body weight) were contrasted with moderate and high groups (n = 33; daily intake greater than or equal to 0.60 mg CN(-) per kg body weight), the authors observed that (1) one-time serum thiocyanate measurements were not sensitive to long-term cyanide intake; however, (2) antibody titers to thiocyanates were positively correlated with cassava-based cyanide intakes (r = .22, P = 0.05); and (3) serum IgM, IgG, and IgA levels were elevated in individuals regularly consuming moderate and high levels of dietary cyanide. Possible responsible mechanisms and health implications are discussed.

Adolescent↗
PubMed1984

Death from asthma in Auckland: circumstances and validation of causes.

New Zealand has experienced an epidemic of asthma deaths since 1977 with mortality rates of over 3.0/100 000 for people aged 5-34 years, more than three times the rate of comparable countries. To examine the reasons for this high mortality rate all deaths from asthma in people under 70 years in the Auckland region in 1981-82 were investigated. A total of 84 possible cases were studied and the validity of death certificates was found to be excellent for people under the age of 50 years. Fifty-three cases had usefully reversible asthma at the time of death and the mortality rate was almost four times higher in Pacific Islanders than in caucasians, with the Maori rate being intermediate. Sixty-seven percent (35) of the deaths in people with usefully reversible asthma occurred at home. In only 40% of cases had the patient reached some form of medical care. No deaths occurred in the patients admitted to hospital with the diagnosis of asthma during this period.

Adolescent↗
PubMed1984

Myocardial infarction and sudden death in Auckland.

A population-based register of definite myocardial infarction and sudden death was established in Auckland for the twelve months from 1 March 1981. Data were collected on 905 myocardial infarctions and 300 sudden deaths that occurred in people under the age of 70 years. The age standardised event rates were more than three times higher in men than in women. The rates of myocardial infarction were comparable in Maoris and non-Maoris but the sudden death rate was almost three times higher in Maoris than in the other ethnic groups. The age standardised 28 day myocardial infarction case fatality rates were 27% and 21% for men and women respectively. Overall, 42% of patients who reached hospital were transported by a life support unit, and 59% of patients who reached a coronary care unit did so within four hours of onset.

Adult↗
PubMed1984

Evidence of alpha 2-adrenoceptors in the nasal blood vessels of the dog.

alpha-Adrenoceptor subtypes were demonstrated in an in vitro preparation of the vascular smooth muscle of the canine nasal mucosa. alpha 1-Receptors were located on the surface of vascular smooth muscle (postsynaptic). alpha 2 Subtypes were situated both at postsynaptic and presynaptic sites on adrenergic nerve terminals. Presynaptic alpha 2-adrenoceptor stimulation yielded an inhibition of excessive norepinephrine release from nerve terminals. Stimulation of postsynaptic receptors, either alpha 1 or alpha 2, produced vasoconstriction. Although there was good evidence of the presence of postsynaptic alpha 2-receptors, they did not appear to be dominant among the postsynaptic receptors.

Adrenergic alpha-Agonists↗
PubMed1983

Blood pressure levels and the treatment of hypertension in Auckland, 1982.

The level of coronary heart disease risk factors in a random sample of 1598 people aged 35-64 years was examined in Auckland in 1982. Blood pressure was measured and the prevalence of treated and untreated hypertension determined. Mean systolic blood pressure increased with age from 124 mmHg (16.49 kPa) in men aged 35-39 years to 144 mmHg (19.15 kPa) in those aged 60-64 years, and from 115 mmHg to 140 mmHg (15.29-18.62 kPa) in women in the same age groups. Compared with previous New Zealand studies blood pressure levels were lower in this study and considerably more people were on antihypertensive treatment. Hypertension is still a major problem in Auckland with 21% of men and 19% of women aged 35-64 years either hypertensive or on antihypertensive treatment. Although half of these people were on treatment, 16% of men and 9% of women in this age group in Auckland were estimated to have a blood pressure level in the hypertensive range.

Adult↗
PubMed1983

Trends in hospital admission rates and drug treatment of asthma in New Zealand.

Trends in hospital admission rates from asthma and sales of anti-asthma drugs in New Zealand for the past two decades were examined. In this period there has been a marked increase in hospital admissions for asthma and in sales of anti-asthma medications. These findings and the recently reported increase in asthma mortality in New Zealand indicate that asthma is an important health problem in this country.

Asthma↗
PubMed1983

Sudden death in runners.

Coronary heart disease risk factors and circumstances of death were examined in 258 people who were a representative sample of all persons, less than 70 years of age, dying suddenly and unexpectedly in Auckland during the twelve month period from 1 March 1981. From this sample we identified nine individuals who had been running regularly for more than three months prior to death. All those identified were men aged between 35 and 56 years, all had historical evidence of abnormal coronary heart disease risk factors and six were known to have had symptomatic cardiovascular disease. Seven of the nine died during or within 30 minutes of exercise and eight of the nine had postmortems showing severe coronary artery disease.

Adult↗
PubMed1983

Calcium, calcium blockers, and nasal smooth muscle.

A canine in vitro nasal blood vessel preparation was tested to determine the effects of calcium (Ca) on smooth-muscle contraction. The contractions induced by either electrical stimulation or vasoconstricting agents were reduced or abolished by reducing the concentration of the Ca in the medium. The Ca response was dose-dependent and reversed at a high concentration. Contractions induced by vasoconstrictors were more resistant to the change of the Ca concentration than by electrical stimulation. Verapamil, a blocker of Ca entry, inhibited the contraction by simulating Ca depletion. These changes show that the extent of Ca influx regulates the smooth-muscle contraction of the nasal blood vessels consistent with the reports concerning other vascular smooth muscle.

Animals↗
PubMed1983

Comparison of hemoglobin values in black and white male U.S. military personnel.

Black and white male military personnel were studied to determine if hemoglobin (Hb) differences existed between the two groups, and if so, whether they were due to dissimilar nutrient intakes or to different patterns of vitamin and mineral self-therapy. Data analyses showed that black males (n = 331) had a 0.27 g/dl lower mean Hb than white males (n = 2268, P = 0.006). However, when only black (n = 60) and white (n = 371) subjects with known iron intakes at or above the recommended level were compared, the differences in the Hb of the two groups became smaller. The serum ferritin values of both of the latter groups appeared adequate for unimpaired Hb synthesis. The use of vitamin and mineral supplements did not differ significantly between the two groups. Adequate intakes of the hemopoietic nutrients resulted in higher Hb levels for both black and white males; at these levels of nutrient intakes the differences in the Hb values of black and white subjects were smaller than those previously reported. Studies comparing the Hb levels of black and white personnel should consider the level of iron intake of the two groups before drawing conclusions about the magnitude and implications of observed differences in Hb concentrations.

Adult↗
PubMed1983

Astemizole: its use in patients with chronic vertigo and eng signs--a pilot study of a new drug.

Astemizole, a new H1 antihistamine, was tested on 10 patients with chronic dizziness and either spontaneous or positional nystagmus. Patients with Meniere's disease were excluded from the study. The patients took 10 mg of astemizole per day for 30 days. Four ENGs were performed; one pre-drug, one after 2 weeks of drug, one after 4 weeks of drug and one post-drug ENG. Six of the 10 patients showed a clear decrease in spontaneous and/or positional nystagmus at the second and third ENG and a rebound of nystagmus when the drug was stopped. There was a positive relation between subjective symptoms and nystagmus. No side-effects were observed.

Adult↗
PubMed1983

Tissue response to Plasti-Pore and Proplast otologic implants in the middle ears of cats.

Plasti-Pore (high density polyethylene) and Proplast (polytetrafluoroethylene-carbon fiber composite) are porous materials that have been employed for the fabrication of ossicular replacement prostheses. Despite many years of clinical experience with these otologic implants, questions remain regarding the tissue response elicited by these materials in the middle ear. The objective of this study was to evaluate histologically the tissue response to Plasti-Pore and Proplast implants in the middle ears of cats through one year of implantation. Plasti-Pore and Proplast total ossicular replacement prostheses, trimmed to "T" shapes, were inserted in fourteen cats, replacing the superstructure of the stapes. One Plasti-Pore and one Proplast implant were implanted in each animal. Cats were killed after two weeks, one, three, and six months, and one year. The histologic response to the Plasti-Pore and Proplast implants was similar. A fibrous capsule contained within a flattened epithelial cell sheath enveloped both types of implants. The mucosa enveloping the devices was continuous with the lining of the tympanic cavity and served to stabilize the implants. Fibrous tissue from the capsule infiltrated larger surface pores. Multinucleated giant cells and macrophages were the predominant cell types in the porosity of both types of implants. The relatively small pores of the devices did not appear to be able to accommodate both the phagocytic cells, which were responding to the particulate features of the materials, and fibrous tissue.

Animals↗