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Biomedical subjects

D Robertson

Publications and source records attributed to D Robertson.

At least 253 records · Page 14Linked to original sources
PubMed1992

Histological and angiographic effects of a pulsed holmium:YAG laser in normal and atherosclerotic human coronary arteries and aorta.

OBJECTIVE: The aims were (1) To determine the histological and angiographic effects of holmium:YAG laser energy delivered through clinical multifibre laser catheters on fresh cadaveric coronary arteries; and (2) to relate the placement of optical fibres in the catheter to patterns of tissue ablation in cadaveric aorta. METHODS: Eight fresh cadaveric hearts and segments of aorta were used. Hearts were mounted on a new pressure perfusion device. The laser catheter was delivered over a guidewire in the lumen until it met an area of resistance. The coronary artery lumen was perfused at approximately 100 mm Hg mean pressure. These arterial areas were identified on angiography, marked, and then exposed to laser energy in the range 600-3000 mJ.mm-2. Normal and atherosclerotic areas of fresh cadaveric aortic strips were exposed to increasing laser energies using either constant or increasing fluence. Coronary arteries were pressure perfused with formalin for 18-24 h at 100 mm Hg mean pressure, and aortic strips were immersed in 5% formalin. Light and scanning electron microscopy studies were carried out. RESULTS: There were no perforations or dissections by angiography in the fresh coronary arteries. One of 15 normal coronary artery segments and 10 of 16 of the pressure perfused, fixed, atherosclerotic coronary artery segments showed thermal changes associated with atherosclerotic plaque ablation. In aortic tissue, thermal effects extended 0 to 0.6 mm lateral to the ablated crater. Acoustic effects were seen only in the aortic strips after ablation at fluences > 1000 mJ.mm-2. The "dead spaces" around the optical fibres in the catheter resulted in significant amounts of coagulated tissue fragments remaining in the crater. CONCLUSIONS: Holmium:YAG laser energy delivered through multifibre catheters ablated atherosclerotic tissue in coronary arteries with minimal damage to the normal walls. The cadaveric coronary artery perfusion apparatus is useful for assessing catheter delivery and mobility and the effects of laser energy on the coaxially orientated normal and atherosclerotic coronary arterial wall.

Aorta↗
PubMed1992

An appraisal of low-temperature embedding by progressive lowering of temperature into Lowicryl HM20 for immunocytochemical studies.

The progressive lowering of temperature (PLT) method of embedding for electron microscope immunolabelling has been examined with the objective of formulating a standardized protocol which can be applied to a wide variety of samples. The methods described cover fixation, processing of samples by the PLT method, embedding in Lowicryl HM20 and subsequent immunolabelling. Each of the steps in the fixation and embedding protocol has been assessed for its potential to retain both morphology and antigenicity. Comparison of samples embedded in Lowicryl K4M and HM20 at -25 degrees C indicate an increased membrane contrast in HM20 sections, and a further improvement in morphology when samples were embedded in HM20 at -50 degrees C rather than at -25 degrees C. The results of applying the methods described are demonstrated in a range of samples of both mammalian and botanical origin, which includes solid tissues, cells in suspension, and cells grown in vitro as a monolayer culture and embedded in situ. Samples processed by this method have been immunolabelled using a wide range of antibodies recognizing nuclear, cytoplasmic, cell membrane and extracellular matrix antigens.

Acrylic Resins↗
PubMed1992

Ultrastructural localization of bcl-2 protein.

Previous cell subfractionation studies have indicated that bcl-2 is an inner mitochondrial membrane protein. We have sought to determine the ultrastructural localization of bcl-2 protein in lymphoma and breast carcinoma cell lines and biopsy material known to overexpress bcl-2 using immunoelectron microscopy. To avoid the possibility of processing artifacts, samples were prepared by three different methods: progressive lowering of temperature, cryosectioning, and freeze-substitution. In all instances the labeling of bcl-2 protein was relatively weak but the distribution the same. In both lymphoma and breast carcinoma tissues, bcl-2 protein was detected on the periphery of mitochondria: little labeling of either the mitochondrial matrix or cristae could be detected. Labeling was also detected on the perinuclear membrane and throughout the cytoplasm, as also indicated by confocal microscopy. These data therefore indicate that bcl-2 protein can be detected at several intracellular sites and that at the likely functional destination, the mitochondria, there appears to be, contrary to expectations, a preferential association with the outer membrane.

Breast Neoplasms↗
PubMed1992

Synthesis and deposition of glycosaminoglycans in the murine hemopoietic stromal line S17: modulators of the hemopoietic microenvironment.

The murine hemopoietic stromal cell line S17 can support either myelopoiesis or lymphopoiesis depending on the culture conditions (i.e., the presence of steroid or mercaptoethanol). The glycosaminoglycans are important components of the extracellular matrix, which influence hemopoietic cell proliferation. Accordingly, glycosaminoglycans have been compared under different growth conditions. Under myeloid conditions (with steroid) a higher proportion of the sulfated glycosaminoglycans was incorporated into the cell layer and the extracellular matrix was increased, whereas synthesis was reduced under lymphoid conditions (with mercaptoethanol). The inclusion of steroid or mercaptoethanol did not alter the nature of the heparan sulfate synthesized as shown by DEAE anion-exchange chromatography, cleavage with specific enzymes and resolution of the digestion products by gel electrophoresis (oligomapping), and glycosaminoglycan size. The major species of sulfated proteoglycan synthesized under the different growth conditions (200 and 110 kd for the culture supernatant and 110, 71, and 38 kd for the cell layer) were shown to be very similar by polyacrylamide gel electrophoresis. Although no qualitative difference was found biochemically between the major glycosaminoglycans/proteoglycans, scanning electron microscopy revealed major differences in the pattern of deposition of the glycosaminoglycans. Under myeloid conditions, a rich fibrous matrix covered the cell layer, whereas under lymphoid conditions glycosaminoglycan was sparsely deposited. The arrangement of the extracellular matrix may have important consequences for myelo- and lymphopoiesis.

Animals↗
PubMed1992

The roles of health care teams in care of the elderly.

In this brief overview of the issues relating to health care teams in geriatric care, some advantages of multidisciplinary team care versus care by an individual practitioner are outlined. An examination of barriers to teamwork and strategies to overcome them follows. Finally, a Canadian program in which medical students and family practice residents participated in interdisciplinary teamwork is described.

Aged↗
PubMed1992

Chronic hypotension. In the shadow of hypertension.

Understanding the causes and treatment of chronic hypotension is of benefit to affected patients and may also shed light on the physiology and genetics of mechanisms of blood pressure control. Symptomatic hypotension (almost always with a blood pressure fall greater than or equal to 20/10 mm Hg) may reflect unrecognized medication effects or a variety of other causes. Autonomic neuropathies include those secondary to diabetes, peripheral autonomic impairment (the Bradbury-Eggleston syndrome), central autonomic impairment (the Shy-Drager syndrome), or newly described gene defects such as dopamine-beta-hydroxylase deficiency (which causes the absence of norepinephrine with an accumulation of dopamine). Baroreceptor dysfunction causes wide swings in blood pressure that are unrelated to posture, whereas a variety of stimuli (cough, micturition, or carotid sinus pressure) may precipitate paroxysmal parasympathetic activation, and sympathetic orthostatic hypotension associated with hypovolemia may occur with mitral valve prolapse or as an idiopathic condition. The differentiation of these and other causes of symptomatic hypotension may in many cases lead to beneficial therapy.

Chronic Disease↗
PubMed1992

Relationships among health beliefs, self-efficacy, and exercise adherence in patients with coronary artery disease.

Management of the pathologic progression of coronary artery disease requires life-style changes in patients, but the level of compliance with medical recommendations is low. Critical care nurses have a unique opportunity to encourage patients to assume responsibility for their health care and life-style behavior. In this study we developed a model to identify the relationships among variables that explained adherence to a recommended exercise regimen. The variables studied included self-efficacy, perceived severity, barriers, benefits, and cues to action.

Adult↗
PubMed1991

Administration of carbamazepine in the nucleus of the solitary tract inhibits the antihypertensive effect of clonidine.

The effects of carbamazepine administration into the nucleus tractus solitarii (NTS) on central alpha 2-adrenergic cardiovascular function were studied in normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Stereotaxic microinjections of carbamazepine (288 ng/60 nl) into the NTS of SHR transiently increased blood pressure, heart rate, and renal sympathetic nerve activity. These effects were followed by a modest depressor and bradycardic effect, with no change in sympathetic nerve activity. In addition, previous intra-NTS administration of carbamazepine attenuated the antihypertensive effect of the centrally acting alpha 2-adrenoceptor agonist, clonidine. Similar carbamazepine effects were observed in the WKY rats. These results suggest that some of the cardiovascular changes observed during carbamazepine treatment involve antagonism of central noradrenergic mechanisms.

Animals↗