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Biomedical subjects

W McBride

Publications and source records attributed to W McBride.

At least 55 records · Page 3Linked to original sources
PubMed1984

Nitrendipine: effects on vascular responses and myocardial binding.

We have further defined the binding characteristics of [3H]nitrendipine to myocardial microsomal membranes of cats, dogs, rats, and rabbits and to canine coronary vasculature (1.5-3.0 mm OD), and we have studied nitrendipine's effect on contractile responses in isolated feline cardiac muscle and canine coronary arteries. [3H]nitrendipine binding is rapid, saturable, and reversible in all four species and in all of these tissues. Feline myocardium has a single binding site with a dissociation constant (KD) of 1.94 nM. Canine myocardium may have two classes of binding sites, with the high-affinity site having a KD of 0.17 nM. Nitrendipine depresses contractility in isolated feline cardiac muscle and canine coronary arteries in a dose-dependent manner [half-maximal dose (ED50) 0.20 microM in isolated feline cardiac muscle and 1.6-6.3 nM for potential dependent contractile responses in isolated canine coronary arteries] and severely blunts the contractile response to increases in extracellular calcium concentration in isolated feline papillary muscles. In contrast to verapamil and D 600, nitrendipine does not prevent the treppe phenomenon. In isolated feline cardiac muscle and large canine coronary arteries, the minimal nitrendipine concentration required for specific binding and for depression of contractile responses is similar. However, only in large canine coronary arteries is the ED50 for nifedipine's depression of contractility similar to the KD for [3H]nitrendipine binding in the respective tissue.

Animals↗
PubMed1983

Differences in myocardial alpha- and beta-adrenergic receptor numbers in different species.

In the present study, we tested the hypotheses that 1) different species have different myocardial adrenergic receptor numbers and 2) selected "slow-channel" calcium antagonists compete with alpha-adrenergic antagonists for binding to varying degrees in different species. The data obtained in the present study demonstrate that there is a markedly decreased number of alpha 1-adrenergic and increased number of beta-adrenergic receptors in canine compared with rabbit and rat myocardium. The differences in adrenergic receptor numbers exist without major differences in alpha 1-adrenergic receptor affinity in the species studied. There was no significant difference in left ventricular or plasma catecholamine content between the rat and dog. Selected slow-channel calcium antagonists compete for alpha 1-adrenergic receptor binding in rabbit, rat, and canine myocardium. However, only in rabbit myocardium does verapamil antagonize alpha 1-adrenergic receptor binding at moderate concentrations, whereas verapamil in canine and rat myocardium and 1) 600 in all three species antagonize alpha 1-adrenergic receptor binding only at relatively high concentrations. Nifedipine, a dihydropyridine-type slow-channel calcium antagonist, had no effect on prazosin binding to rat, rabbit, and dog myocardial membranes.

Animals↗
PubMedDate not supplied

Neurobehavioural consequences of prenatal low level exposures to lead.

A cohort of 318 children born in three Sydney hospitals between April 1982 and March 1983 were recruited into a five year prospective study designed to investigate the relationship between low level lead exposures and neurobehavioural development. Blood samples were obtained at the time of birth, then at 6 month intervals to 4 years and then at 5 years; neurobehavioural and physical measures were taken at 6 months, 12 months and hence annually to 5 years. This paper presents some of the findings from the first three years of the study and addresses the issue of the relationship between fetal exposures to lead and child development to three years. Maternal and cord blood lead levels were in range 0-29 microgram/dl with the majority less that 15 micrograms/dl. The geometric means were, respectively, 9.1 micrograms/dl and 8.1 micrograms/dl. The analyses presented do not support the hypothesis of a relationship between maternal and cord blood lead levels in this range and developmental deficits in young children to the age of three years.

Adult↗
PubMedDate not supplied

Echocardiographic diagnosis of pneumopericardium and hydropneumopericardium.

Pneumopericardium and hydropneumopericardium are rare conditions in which hemodynamic compromise is common. Loss of the M-mode and two-dimensional image coincident with the systolic phase of each cardiac cycle and swirling echogenic bubbles within the pericardial space produce a distinctive M-mode and two-dimensional echocardiographic appearance. This provides an additional method for prompt diagnosis.

Adult↗
PubMedDate not supplied

Immunosuppression by melanoma cells as a factor in the generation of metastatic disease.

Studies of the regional nodes (RLN) of melanoma patients, using immunohistology with anti-S-100 protein and monoclonal antibodies have shown occult tumor cells (OTC) in nodes ostensibly tumor-free by H&E staining. OTC were demonstrated in 14% of Stage I patients, mainly those with deep, thick primaries and 30% of Stage II patients, mainly those with at least 3 tumor-positive nodes on H&E. The nodes containing OTC are those nearest to tumor on the direct lymphatic pathway (dye studies). Parallel studies show nodes in the same position to be immune suppressed (histology, immunohistology, response to mitogens, alloantigens and lymphokines) and to contain many suppressor T cells (Con-A). Melanoma-derived materials (gangliosides, prostaglandins, lipoprotein antigens) downregulate lymphocyte and macrophage functions, providing a possible mechanism for the suppressed function of nodes near tumor, a suppression that may facilitate tumor cells as evidenced by the survival of OTC.

Humans↗