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Biomedical subjects

D Robertson

Publications and source records attributed to D Robertson.

At least 307 records · Page 17Linked to original sources
PubMed1989

Descending projections from auditory brainstem nuclei to the cochlea and cochlear nucleus of the guinea pig.

Projections from auditory brainstem nuclei to the cochlea and cochlear nuclei in the guinea pig were studied by injection of two retrograde fluorescent neuronal tracers. For seven experiments fast blue was injected into the scala tympani of one cochlea and diamidino yellow was injected into dorsal or anteroventral cochlear nucleus of the same side. The results show that the efferent projections to the cochlea and cochlear nucleus generally form two separate neuronal systems even though they share many common nuclei of origin. The largest projections to the cochlear nucleus come bilaterally from the lateral and ventral nuclei of the trapezoid body. Other nuclei, the lateral superior olive, the ventral nucleus of the lateral lemniscus, the dorsomedial periolivary nuclei, and the medial nucleus of the trapezoid body showed an ipsilateral bias in their projections to the cochlear nucleus. An upper limit of 3.5% of the medial system olivocochlear efferent neurones projecting to the cochlea were labelled with both diamidino yellow and fast blue, suggesting that few efferent neurones projecting to the cochlea send collaterals to the cochlear nucleus in this species. However, the site of medial system olivocochlear efferent collateral terminations is the granule cell area for the cat, mouse, and gerbil. When diamidino yellow was injected in the superficial layers of the cochlear nucleus, including the superficial granule cell layer of the ventral cochlear nucleus, approximately 3.6% of medial system olivocochlear efferents projecting to the cochlea sent collaterals to the cochlear nucleus. In three animals fast blue was injected into the cochlear nucleus and diamidino yellow into the cochlea. These experiments revealed a greater proportion of the medial system olivocochlear efferents projecting to the cochlea sending collaterals to the cochlear nucleus, but this proportion was still less than 10%. These results were confirmed by the extracellular injection of horseradish peroxidase into the intraganglionic spiral bundle. Only three medial system olivocochlear efferents were observed to send collaterals to the cochlear nucleus. This number was less than 10% of all labelled medial system fibres. Although these experiments suggest that in the guinea pig the number of olivocochlear efferents sending collaterals to the cochlear nucleus is considerably smaller than is found for the cat, mouse, and gerbil, it is not possible with the current experimental procedures to conclude whether the results are due to species or methodological differences.

Animals↗
PubMed1989

Patterns of plasma levels of catechols in neurogenic orthostatic hypotension.

Patients with neurogenic orthostatic hypotension can have deficits in sympathetic neural function at any of several levels of the sympathetic neuraxis. We determined whether patterns of plasma levels of dopa, norepinephrine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid would distinguish patients with orthostatic hypotension associated with multiple system atrophy, pure autonomic failure, or deficiency of dopamine-beta-hydroxylase. Plasma levels of catechols were normal in most patients with multiple system atrophy, consistent with relatively intact peripheral sympathetic neurons; in contrast, most patients with pure autonomic failure had decreased levels of all four catechols, consistent with degenerative loss of sympathetic nerve endings. Patients with deficiency of dopamine-beta-hydroxylase had increased levels of dopa and dihydroxyphenylacetic acid and markedly decreased levels of norepinephrine and dihydroxyphenylglycol, suggesting compensatory increases in sympathetic nerve activity in the absence of norepinephrine biosynthesis. Subgroups of patients with pure autonomic failure or multiple system atrophy had low levels of norepinephrine with normal levels of dopa, dihydroxyphenylglycol, and dihydroxyphenylacetic acid, consistent with normal catecholamine biosynthesis and decreased postganglionic sympathetic nerve traffic or decreased exocytotic release from sympathetic nerve endings. The results demonstrate the value of examining patterns of plasma levels of catechols to elucidate mechanisms of neurogenic orthostatic hypotension.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Identification of vascular endothelial cells in murine omentum using the lectin, Dolichos biflorus agglutinin: possible applications in the study of angiogenesis.

The purpose of this study was to determine whether the plant lectin, Dolichos biflorus agglutinin (DBA), can be used to recognize capillary endothelial cells and their processes during angiogenesis. By means of a peroxidase conjugate of DBA, blood vessels were visualized in whole mounts and ultrathin sections of mouse omentum. A part of this mesentery normally comprises an avascular membrane that is approximately 30 microns in thickness. Changes in the vascular plexus bordering this membrane were induced by intraperitoneal injection of irradiated Landschutz cells. Vascular endothelial cells were precisely and intensely stained, and vasculogenic processes were reliably distinguished from those of other cells. This technique permitted observation of the structure and distribution of capillary sprouts, and their relationship to each other and to pre-existing blood vessels. It was discovered that filiform projections extend from sprout apices. These projections may fuse allowing adjacent sprouts to form a new capillary loop.

Animals↗
PubMed1989

Congenital vertebral-jugular fistula in an infant.

Pediatric cardiologists are often consulted to evaluate continuous murmurs in children. This case report describes a child with a congenital vertebral-jugular fistula who presented with torticollis and a continuous murmur. The differential diagnosis of continuous murmurs in this setting is discussed.

Arteriovenous Malformations↗
PubMed1989

Response bias in a health status survey of elderly people.

This paper compares respondents and non-respondents from the community sample of the Saskatchewan Health Status Survey of the Elderly. Response bias was assessed by comparing the demographic characteristics and use of health care services of the two groups. A stratified two-stage area probability sample was drawn from a comprehensive sampling frame. There were 1614 subjects eligible; interviews were completed with 1267 (78.5%). In the very elderly (85+ years) cohort, disproportionately more urban dwellers and more males were interviewed; the sample was otherwise demographically representative of the elderly population. Non-respondents, especially the very elderly, used significantly more medical services than respondents, and had a higher number of hospital admissions. Non-respondents over age 75 experienced significantly longer average lengths of stay. On average, non-respondents used approximately 15% more hospital days. Non-respondents over age 75 appear to be more likely to experience ill health than respondents. Hence, statistics from this survey are conservative estimates of the ill health of the elderly.

Aged↗
PubMed1989

The prevalence of cognitive impairment in an elderly Canadian population.

We investigated cognitive impairment in a study of the health of the elderly population of Saskatchewan. Surveys of elderly persons living at home (n = 1267) and living in long-term care facilities (n = 990) were conducted in 1981. Cognitive impairment was assessed by a short 10-item mental status questionnaire previously validated against a clinical diagnosis of dementia in an elderly Canadian population. The prevalence of clinically significant cognitive impairment was found to increase with age and with dependence level in long-term care facilities. We estimate that 7.8% of the elderly population have cognitive impairment consistent with a clinical diagnosis of dementia. Our estimates are compared with those derived from other studies. These findings affirm the importance of dementia as a cause of dependence in the elderly and the need for long-term care facilities to deal with dementia and its consequences. Also, since at least as many persons with cognitive impairment live at home as in long-term care facilities, health care planners must direct attention to the elderly with dementia at home.

Activities of Daily Living↗
PubMed1989

Cardiovascular effects of neuropeptide Y in rat brainstem nuclei.

Central catecholaminergic neurons are involved in cardiovascular regulation. Neuropeptide Y (NPY) coexists with adrenaline and noradrenaline in the rat brain, and interactions among these substances have been studied. The purpose of this study was to investigate the possible role of NPY in central cardiovascular control. Male Sprague-Dawley rats were anesthetized with urethane, and blood pressure was monitored intra-arterially. Intramedullary microinjection (60 nl) of NPY (0, 46.5 fmol, 465 fmol, 1.5 pmol, and 4.65 pmol) was made into the nucleus tractus solitarii (NTS), into the area postrema, and into the C1 area in the rostroventrolateral medulla. Injection site was identified by L-glutamate administration and confirmed histologically. Unilateral injection of NPY into the NTS produced a prominent dose-related decrease in heart rate and systolic and diastolic blood pressure (-106 +/- 8 beats/min, -56 +/- 2 mm Hg, and -33 +/- 2 mm Hg, respectively after 4.65 pmol NPY, n = 7, p less than 0.001). Maximal changes occurred at 30 seconds and recovered in 10 minutes for blood pressure and 20 minutes for heart rate. Injection into the area postrema produced an initial increase in heart rate and mean blood pressure (+23 +/- 2 beats/min and +18 +/- 2 mm Hg) followed by a prolonged decrease in heart rate and mean blood pressure (-14 +/- 4 beats/min and -15 +/- 2 mm Hg, respectively, n = 7, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Adenosine produces pulmonary vasoconstriction in sheep. Evidence for thromboxane A2/prostaglandin endoperoxide-receptor activation.

Adenosine, an intermediate product in the metabolism of ATP, is thought to produce vasodilation in all vascular beds with the exception of the kidney. Due to its theoretical potential as a pulmonary vasodilator, we studied the hemodynamic effects of adenosine in the pulmonary vasculature of chronically instrumented awake sheep. Adenosine produced significant pulmonary vasoconstriction instead of the expected vasodilatation. Bolus injections of adenosine into the superior vena cava produced a dose-dependent increase in pulmonary artery pressure that was entirely due to an increase in vascular resistance, since cardiac output decreased slightly. This effect is produced via activation of specific cell surface adenosine receptors, since it was blocked by the adenosine-receptor antagonists theophylline and dipropylsulfophenylxanthine. The cell type involved in adenosine-induced pulmonary vasoconstriction appears to be located within the lung, since vasoconstriction was blunted when adenosine was infused into the left atrium, distal to the lung. However, adenosine does not directly vasoconstrict the pulmonary vasculature, because its effect could be completely abolished by cyclooxygenase inhibition with either indomethacin or ibuprofen and by a thromboxane A2/prostaglandin endoperoxide-receptor antagonist (SQ 29,548). Adenosine-induced vasoconstriction was also greatly reduced after inhibition of thromboxane synthesis. Thus, adenosine produced pulmonary vasoconstriction through generation of a thromboxane/endoperoxide product. Whether endogenous adenosine is involved in the generation of pulmonary vasoconstriction seen in pathophysiological states remains to be determined. To our knowledge, this is the first clear evidence for adenosine-induced vasoconstriction outside the kidney and for an interaction between adenosine and eicosanoid mechanisms.

Adenosine↗
PubMed1989

Caffeine potentiates the renin response to furosemide in rats. Evidence for a regulatory role of endogenous adenosine.

Adenosine is a potent inhibitor of renin release. It has therefore been suggested that endogenous adenosine may play a role in the regulation of renin release. Sodium-chloride transport at the level of the macula densa has been proposed as the primary source of endogenous adenosine. Evidence to support a modulatory role of adenosine on renin release in vivo is, however, limited. We therefore wanted to determine if: 1) adenosine modulates furosemide-induced renin release and 2) sodium-chloride reabsorption at the macula densa is essential for adenosine actions. To test these hypotheses, three groups of rats were pretreated either with saline or the adenosine receptor antagonists caffeine or 1,3-dipropyl-8-(p-sulfophenyl)xanthine (both at a dose of 30 mg/kg followed by 450 micrograms/kg/min). Rats then received furosemide (50 mg/kg i.v.). In the vehicle group, furosemide increased urinary volume, sodium and potassium excretion and increased plasma renin activity from 6 +/- 1 to 45 +/- 11 ngAl/ml/hr. Caffeine and 1,3-dipropyl-8-(p-sulfophenyl)xanthine potentiated the increase in plasma renin activity produced by furosemide (to 120 +/- 15 and 147 +/- 21 ng Al/ml/hr, respectively), whereas having no significant effects on urinary volume, sodium excretion or blood pressure. These results suggest that furosemide-induced renin release in vivo is restrained by endogenous adenosine. In as much as furosemide blocks sodium-chloride transport in the thick ascending limb of Henle's loop and the macula densa cells, it appears that under the conditions of this study sodium transport across these segments is not essential to initiate adenosine-mediated mechanisms.

Adenosine↗
PubMed1989

Some properties of dendritic macrophages from peripheral lymph.

Peripheral lymph was collected from the skin and liver of sheep, and from the intestine of rats. The dendritic macrophages contained in it were isolated by centrifuging the lymph over a layer of 'Nycodenz'. Similar cells were produced by culturing mononuclear cells from venous blood, but the yields were very small. The numbers of dendritic cells in the lymph from the legs of sheep increased five-fold after xylene had been applied to the skin. Dendritic macrophages displayed abundant class II histocompatibility antigens on their surfaces, as well as immunoglobulins. Although the latter were probably acquired passively, they remained present for several days on cells cultured in vitro. When in vitro, dendritic cells could be shown to phagocytose marker particles, such as latex beads, but their performance was unimpressive compared to macrophages from the peritoneal cavities of rats. In contrast, their ability to phagocytose rapidly T4 phage or influenza viruses unequivocal and striking.

Animals↗
PubMed1988

Prevalence of urinary incontinence in patients receiving home care services.

We conducted a 1-day survey to determine the prevalence of urinary incontinence among patients in four home care programs in southern Ontario and the characteristics of incontinent patients. Of the 2801 patients for whom the continence status was known, 22% were assessed as incontinent. The mean age of the incontinent patients was 74 (extremes 18 and 101) years, and 65% were women. A total of 89% had at least one functional disability in cognition, mobility, transferring in and out of bed or chair, or undoing garments. The incontinence was moderate to severe in 41% of the patients, and 95% of the family caregivers living with these patients viewed the incontinence as a problem. Palliative rather than remedial treatment was used most frequently; only 5% of the patients had undergone a urodynamic assessment in the previous year. Future research should emphasize the assessment of remedial interventions.

Adolescent↗
PubMed1988

Cochlear nucleus inputs to olivocochlear neurones revealed by combined anterograde and retrograde labelling in the guinea pig.

Injections of the fluorescent tracer, Fast blue (FB), into cochlear nucleus complex in guinea pig produced strong anterograde labelling of ascending projections from this nucleus. When combined with retrograde labelling of olivocochlear efferent neurones by intracochlear injection of a second fluorescent tracer, Diamidino yellow (DY), the synaptic terminals formed on these cells by projections from the cochlear nucleus could be identified. The results provide direct support for the notion that many of the ipsilateral-monaural cochlear efferents identified in physiological studies correspond to the olivocochlear neurones located in brainstem nuclei contralateral to their target cochlea.

Amidines↗
PubMed1988

AIDS and the small city: the cost at Kingston General Hospital.

Although AIDS is often thought of as a "big-city" disease, it is also becoming a serious health care issue for doctors and other health care workers in "small-city" Canada. Kingston, Ont., is one of those small cities, and of the facilities trying to come to grips with a disease about which much remains to be learned. In this article, Drs. Peter Ford and David Robertson outline their hospital's estimate of the cost, in manpower and money, of dealing with the AIDS crisis. The final estimate: roughly $700,000. Although most of the cost will involve one-time capital spending, they point out that there will likely be ongoing labour-related costs because of the special programs and increased manpower needed to deal with AIDS patients. Clearly, AIDS is no longer a big-city disease.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Both alpha- and beta-adrenoreceptors contribute to the central depressor effect of catecholamines.

We compared the effects of alpha 2- and beta-adrenoreceptor blockade on the central actions of catecholamines and metabolites of alpha-methyldihydroxyphenylalanine, epinephrine, alpha-methylnorepinephrine, and alpha-methylepinephrine were studied. I.c.v. and nucleus tractus solitarii (NTS) injections were carried out under anesthesia. Following i.c.v. injection, both epinephrine and methylepinephrine rapidly reduced blood pressure and heart rate, but the effects of methylnorepinephrine occurred somewhat later. Following microinjection into the nucleus of the solitary tract, epinephrine, methylepinephrine, and methylnorepinephrine all caused hypotension and bradycardia. The hypotensive effects of all 3 amines in the NTS were attenuated in additive fashion by yohimbine, an alpha 2 adrenoreceptor antagonist, and timolol, a beta-adrenoreceptor antagonist, whereas only yohimbine attenuated the bradycardia. The combination of yohimbine and timolol abolished the effects of the amines. These data suggest that in the NTS both alpha 2 and beta adrenoreceptor stimulation contribute to the hypotensive effects of these amines, but that only alpha 2 adrenoreceptors are principally involved in the heart rate response.

Animals↗
PubMed1988

Chloroplast transformation in Chlamydomonas with high velocity microprojectiles.

Bombardment of three mutants of the chloroplast atpB gene of Chlamydomonas reinhardtii with high-velocity tungsten microprojectiles that were coated with cloned chloroplast DNA carrying the wild-type gene permanently restored the photosynthetic capacity of the algae. In most transformants of one of the mutants, a fragment with a 2.5-kilobase deletion was restored to normal size by a homologous replacement event; in about 25 percent of the transformants the restored restriction fragment was 50 to 100 base pairs smaller or larger than that of wild type. About one-fourth of the transformants of this mutant contained unintegrated donor plasmid when first examined. This plasmid persisted in four different transformants after 65 cell generations of continuous liquid culture but was lost from all transformants maintained on plates of selective medium. The restored wild-type atpB gene remains in all transformants as an integral part of the chloroplast genome and is expressed and inherited normally.

Chlamydomonas↗