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Biomedical subjects

D Robertson

Publications and source records attributed to D Robertson.

At least 523 records · Page 29Linked to original sources
PubMed1976

The localization of coronary artery stenoses by 12 lead ECG response to graded exercise test: support for intercoronary steal.

In 39 consecutive patients with unequivocally positive postexercise ECG we have correlated the location and severity of the coronary artery stenoses with the ECG leads in which ischemic ST changes occured. Patients with major stenoses of the right coronary artery, with or without disease of the left coronary system, showed ischemic ST changes in Leads II, III, and aVF. Patients with major stenoses of the left coronary system, many of whom had suffered old inferior wall infarction, showed ST changes in Leads I, aVL, and the chest leads. A group of 11 patients showed ischemic ST changes in leads other than those expected on the basis of the location and severity of coronary artery stenoses. In each of these 11 patients large collateral channels were donated by the vessel in whose territory the ischemic changes occurred. This finding lends support to the concept of intercoronary "steal" during exercise in coronary artery disease, at the same time reducing the value of the postexercise 12 lead ECG in predicting the location and severity of coronary artery stenoses.

Collateral Circulation↗
PubMed1976

Analysis of spontaneous activity of auditory neurones in the spiral ganglion of the guinea-pig cochlea.

1. Spontaneous activity of single afferent neurones in the cochlea of the guinea-pig was studied by measurement of mean rates and computation of interspike interval histograms. 2. The shapes of interval histograms agreed with those found in cat cochlear nerve fibres. Modes of the histograms were less than 7 msec for all cells with mean rates ranging from 20 to 150 spikes/sec. 3. The distribution of mean rates showed higher maximum rates than those found in cat. Cells from animals with abnormally high thresholds showed lower mean rates than those from sensitive animals. 4. No correlation was found between mean spontaneous rate and sensitivity to acoustic stimulation. No discrete populations of cells could be discerned on any of the criteria used. 5. The simultaneous effects of hypoxia on cell thresholds, mean spontaneous rate and scala media potentials are reported. These and other results are discussed in relation to possible sites of generation of spontaneous activity in primary auditory afferents.

Action Potentials↗
PubMed1976

Coronary artery disease with single coronary artery.

The authors have reviewed the literature in search of the coexistence of single coronary artery with significant coronary artery disease. Two cases of single right coronary artery are described. In both, the anomalies were unsuspected and diagnosed roentgenographically in life. Both patients had angina pectoris, positive graded-exercise stress tests, and hemodynamically significant obstruction or occlusion to the coronary arteries. In neither case was the stenosis proximal or amenable to bypass surgery.

Angina Pectoris↗
PubMed1975

The monolayer and organ culture of human colorectal carcinomata and the associated "normal" colonic mucosa and their production of carcinoembryonic antigens.

The carcinoembryonic antigen (CEA) was produced and released by human colorectal carcinomata and also the normal attached mucosa when maintained in both monolayer and organ culture. Immunoperoxidase cytochemical methods were employed for the cellular localization of CEA which was demonstrable only on the neoplastic cells. Gel filtration and immunological methods confirmed that CEA, produced by normal and neoplastic cells, had properties similar to "authentic" CEA derived from metastatic colorectal carcinomata. In addition, two other CEA cross-reacting macromolecules, neither of which was CCEA-2, were produced by these tumours in culture.

Carcinoembryonic Antigen↗
PubMed1975

An autoradiographic study of the binding of 3-H-chlorambucil to cells of a drug-sensitive and drug-resistant strain of the Yoshida ascites sarcoma.

The binding of chlorambucil to drug-sensitive and drug-resistant. Yoshida sarcoma cells has been investigated by an autoradiographic technique. The cells were treated with the drug at various concentrations both in vitro and in vivo. Using both light and electron microscope techniques, and by counting grains on various areas of the cell, the following conclusions were reached. (1) At all drug concentrations there was general cytoplasmic and nuclear uptake by both cell lines. There was no evidence of a specific localization in one site only or for specific exclusion of any one site. (2) At high dose levels (equivalent to 2 mM) the binding was approximately equal in both cell lines, although a few damaged cells bound much greater amounts of drug. (3) At low dose levels (equivalent to 3 mu-M) there was a higher uptake by the nucleus of the sensitive cells compared with the nucleus of the resistant cells; the cytoplasmic binding was similar.

Animals↗
PubMed1975

Ionic mechanism of the efferent olivo-cochlear inhibition studied by cochlear perfusion in the cat.

1. A method for perfusing the scala tympani of the cat's cochlea from basal turn to apex is described. The perfusion with modified Krebs solution did not interfere with the recording of cochlear microphonic (CM) and neural responses to sound, nor with the efferent inhibition elicited by stereotaxic stimulation of the crossed olivo-cochlear bundle (COCB) in the medulla. 2. Cochlear perfusion with solutions in which most of the chloride was replaced by large anions (sulphate or gluconate) decreased or eliminated auditory nerve or the ventral cochlear nucleus. These effects were reversible. They were only observed if the rate of perfusion (2-20 mul/min) was adequate to reduce the chloride concentration in perilymph below about 80 mM, this being estimated, in different perfusion of the same cochlea, by a chloride-selective electrode. 3. The COCB-induced negative shift of the endocochlear potential recorded with a glass micro-electrode inserted into the scala media was abolished by I.V. strychnine o.2 mg/kg. It was decreased when the perilymph chloride was reduced to 50-70 mM and could be abolished when the perilymph chloride dropped to about 5 mM. 4. The COCB-induced potentiation of the cochlear microphonic potential was also reduced by chloride substitution but the pattern of this effect differed from that of neural inhibition. 5. Similar cochlear perfusions with a solution in which the small diameter bromide anion was substituted for chloride did not affect the COCB-efferent effects. 6. The data indicate that the inhibitory transmitter released by COCB terminals elicits an increased conductance to small anions (normally to chloride) in the membrane of the auditory dendrite and of the outer hair cell. The significance of the COCB-induced negative shift of endocochlear potential and of the potentiation of CM is discussed, as well as the pre- and post-synaptic mechanisms involved in the efferent gating exerted on the auditory input. The latter would seem to involve primarily a post-synaptic mechanism at efferent axo-dendritic synapses.

Acoustic Stimulation↗
PubMed1975

The effect of chlorpromazine on plasma renin activity and aldosterone in man.

The response of plasma renin activity (PRA) and aldosterone to the intravenous administration of chlorpromazine was determined in schizophrenic patients while they were supine and on a normal sodium diet. In all subjects PRA and aldosterone increased during chlorpromazine administration with little or no change in blood pressure. The maximum PRA and aldosterone levels occurred 60 min after the higher dose of chlorpromazine. These data suggest that chlorpromazine affects the renin-angiotensin-aldosterone system and it may interfere with the evaluation of this system in patients receiving this drug.

Adult↗
PubMed1975

Ultrastructural and serological studies on the resistance of activated B cells to the cytotoxic effects of anti-immunoglobulin serum. Patch and cap formation of surface immunoglobulin on mitotic B lymphocytes.

Previous studies have shown that rabbit anti-mouse immunoglobulin sera (anti-Ig) which kill non-activated B lymphocytes in the presence of complement, are incapable of doing so when the cells are activated by antigen or mitogen into mitosis. Results reported here indicate that the resistance is not dependent on either the source of antiserum or complement, or on the presence of a mitotic inhibitor, colcemid. Immunoperoxidase staining-electron microscopy techniques were applied to assess whether there was any conspicuous difference between unstimulated versus mitogen-stimulated, mitotic cells with respect to density or distribution of cell surface Ig. No such differences were found; furthermore, mitotic cells showed rapid classical 'patch and cap' formation of cell surface Ig when incubated with anti-Ig at room temperature, indicating the retention of fluid membrane dynamics by lymphocytes in this stage of the cell cycle. In contrast to this cytotoxic resistance, T or B lymphocytes in mitosis were found to be as sensitive, or more so, to lysis by various other antisera when compared to non-mitotic cells. Thus the resistance of mitotic B cells to the cytotoxic effects of anti-Ig serum seems unique and appears independent of any conspicuous quantitative or qualitative change in cell surface Ig.

Animals↗
PubMed1974

Cochlear neurons: frequency selectivity altered by perilymph removal.

Removal of perilylmph from the scala tympani of the guinea pig cochlea reversibly broadened the tuning curves of single spiral ganglion cells emanating from the basilar membrane. Thus, fluid continuity along the membrane is essential for normal cochlear function, in particular for sharp neural tuning curves. These data reveal a possible source of error in some estimates of basilar membrane motion and suggest a reappraisal of current concepts of the mechanism of sharp tunig in primary auditory nerve fibers.

Acoustic Stimulation↗
PubMed1974

Structure and function of developing barley plastids.

Five different regions of the first foliage leaf of etiolated barley seedlings were studied with respect to leaf growth, plastid growth and replication, differentiation of etioplasts, and conversion of etioplasts into chloroplasts upon illumination. Ultrastructural changes of the plastids were correlated with chlorophyll synthesis and development of photosynthetic activity as measured by (14)CO(2) incorporation and O(2) evolution. The first foliage leaf has greater linear growth over a longer period of time in the dark than in the light. Only the bottom two regions (4 and 5) are still growing in the 5-day etiolated leaf. Region 4 grows by cell elongation, and region 5 grows by both cell division and elongation. Plastids in all five regions of the leaf are capable of enlarging when exposed to light. This is true both for the intact plant and for excised sections. Plastid replication occurs predominantly in the younger regions of the leaf (regions 3, 4, and 5). The amount of chlorophyll synthesized by different regions in the intact plant is significantly higher (3-40 times) than that made by excised sections. Ultrastructural changes occurring in each region when excised sections are illuminated were classified into five stages involving increased membrane synthesis and appression into grana, and these changes were correlated with the first appearance of photosynthetic activity. The earliest detectable photosynthetic activity occurs in region 1 after 2 hours of illumination when chloroplasts show only a few overlaps in the thylakoids. Plastids in younger regions of the leaf require up to 24 hours of light to form grana and develop photosynthetic activity. Plastids in each region of the leaf are in different stages of development when photosynthesis is initiated, indicating that development of photosynthetic activity is not strictly correlated with a certain stage of plastid development. Membrane appression is not indicative of photosynthetic activity since overlaps are formed in the dark, but it was always present when photosynthetic activity was detectable. Likewise, there does not appear to be any strict correlation between the presence of chlorophyll and membrane appression. These results show that the particular structural and functional correlations that can be made depend to a large degree on age of the tissue.

Journal Article↗