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Biomedical subjects

R Campbell

Publications and source records attributed to R Campbell.

At least 163 records · Page 9Linked to original sources
PubMed1988

Effects of ketanserin on blood pressure and platelet aggregation in elderly men with mild hypertension.

Thirteen men, age 60 +/- 2 years (mean +/- SEM) with mild hypertension, 151 +/- 4/95 +/- 3 mm Hg, completed a randomized, double-blind, placebo-controlled crossover trial of ketanserin therapy. In comparison to placebo, ketanserin treatment at 40 mg bid for 6 weeks lowered systolic and diastolic blood pressure, 148 +/- 4/92 +/- 3 vs. 140 +/- 6/86 +/- 3 mm Hg, P = 0.19/0.02. The rate of platelet aggregation in response to ADP and epinephrine was unchanged while the response to serotonin was greatly diminished. Neither the systemic pressor response nor the pupillary mydriatic response to phenylephrine was significantly altered. Plasma norepinephrine concentration declined significantly. Ketanserin reduced blood pressure, particularly the diastolic component, in elderly men with mild hypertension. While antagonism of serotonin's effects on platelet aggregation was evident, blockade of alpha 1-receptor-mediated events was not apparent. The results suggest that during chronic therapy the antihypertensive effects of ketanserin were mediated by serotonergic blockade and a possible lytic effect on sympathetic drive. The dual effects of ketanserin on blood pressure and platelet aggregation may be beneficial in reducing cardiovascular complications in hypertensive patients.

Adult↗
PubMed1987

The effects of endothelial injury on smooth muscle cell proliferation.

The endothelial injury induced by the placement of a synthetic graft has been implicated as a stimulus for the development of MIH. In this study we compared the degree of EC coverage and the early SMC-PR in the arterial segments proximal and distal to 2 mm diameter PTFE grafts that had been placed in rabbit carotid arteries (n = 49). In vivo labeling with 3H-thymidine and Evans blue was carried out at intervals of 2 to 33 days after grafting. The SMC-PR was measured as the degree of 3H-labeled DNA divided by the total DNA for each segment, and the EC coverage was determined by planimetry of the area of Evans blue exclusion. There was an early rise in the SMC-PR in both arterial segments, but it was more marked in the distal segment (p less than 0.001). There was no correlation between the SMC-PR and the degree of EC coverage in either the proximal (r = 0.25) or the distal segments (r = 0.10). The data suggest that there is a greater SMC-PR at the distal end of an implanted PTFE graft. The degree of endothelial loss and its regrowth does not appear to be an important factor.

Animals↗
PubMed1987

Control of energy balance during egg production in the laying hen.

The energetic costs of egg production are considered, as is the relationship between egg production and feed intake. Hens feed during the photophase with a peak in consumption prior to the scotophase. This pattern of intake, followed by nocturnal fast, would be expected to lead to an energy deficit at night. However, much of the energy requirement of the night is met by utilization of feed stored in the upper gastrointestinal tract. It is presumed that some nocturnal energy deficit occurs and is met by changes in metabolism and endocrine balance. The hormonal involvement in these changes in avian metabolism is discussed.

Animal Feed↗
PubMed1987

The Zelig phenomenon: a specific form of identity disturbance.

A variety of identity disturbances has been described in psychiatric patients. Although such disturbances possess some common features linked to shared or core psychological structures, qualitative differences that allow them to be distinguished from one another also exist. The cases reported are intended to draw attention to a severe and striking type of identity disturbance observed in psychotic patients, for which we have proposed the eponym, 'the Zelig phenomenon'. The discussion focuses upon the issue of the coexistence in psychopathology of continuity and discontinuity. This apparent paradox can be regarded as an example of parallax, in which two quite different, yet equally valid, perspectives are possible and may be brought alternately into play. It is, however, argued that in the delineation of psychopathological entities it is necessary to adopt the perspective that considers discontinuities and matters of form, even though they may be at times overshadowed by continuities that derive from the alternate perspective.

Adult↗
PubMed1986

Ocular immune responses. II. Priming of A/J mice in the vitreous induces either enhancement of or suppression of subsequent hapten-specific DTH responses.

We previously showed that the "immunologic privilege" of the anterior chamber results not from afferent blockade, but rather from induction of hapten-specific suppressor T cells that appear after anterior chamber priming with antigen. These suppressor T cells induced by anterior chamber priming differ from those induced by i.v. priming in their ability to block the efferent as well as the afferent limb of the immune response and in their lack of idiotypic surface receptors detected by rabbit anti-idiotypic antibody. We now report that intravitreal priming with haptenated syngeneic spleen cells does not result in generation of suppressor cells, but rather, can in some instances result in an enhanced systemic immunoreactivity to the priming hapten. If soluble antigenic preparations are used, however, intravitreal priming results in the generation of the suppressor T cells, which suppress subsequent DTH and CTL responses to the immunizing hapten. The suppressor cell generation after intravitreal priming is a cyclophosphamide-sensitive process. These results demonstrate that soluble products are processed differently in ocular compartments compared with cell surface coupled ligands, and further demonstrate that the generation of hapten-specific suppressor T cells is dependent, at least in part, on the form and on the specific compartment of the eye that is inoculated.

Animals↗
PubMed1986

Substrate specificities and inhibition of two hemorrhagic zinc proteases Ht-c and Ht-d from Crotalus atrox venom.

The proteolytic specificities of two zinc hemorrhagic toxins (Ht-c and Ht-d), isolated from Crotalus atrox venom, were investigated by using the oxidized B chain of bovine insulin and synthetic peptide substrates. The enzymes cleaved the Ala14-Leu15 bond of the insulin B chain most rapidly and the Tyr16-Leu17 slightly more slowly. The His5-Leu6, His10-Leu11, and Gly23-Phe24 bonds were also cleaved but at considerably slower rates. In order to assess the substrate length preferences of the enzymes, peptide analogs of the B chain about the Ala14-Leu15 bond were synthesized ranging in length from four to seven residues. The heptapeptide NH2-Leu-Val-Glu-Ala-Leu-Tyr-Leu-COOH was the best peptide substrate tested with the other peptides having decreasing kcat/Km values with decreasing length. The tetrapeptide NH2-Ala-Leu-Tyr-Leu-COOH was not cleaved by the enzymes. Furthermore, this peptide was shown to serve as a competitive inhibitor of the toxins. The N-acetylated pentapeptides and hexapeptides, synthesized to probe the active site environment of the enzymes, were significantly better substrates than their unacetylated counterparts. The toxins had the highest kcat/Km values for the acetylated peptide Ac-Val-Ala-Leu-Leu-Ala-COOH. The data suggest that the toxins may indeed have extended substrate-binding sites, which may accommodate at least six amino acid residues. The best substrate examined thus far for the toxins is the fluorogenic peptide analog 2-aminobenzoyl-Ala-Gly-Leu-Ala-4-nitrobenzylamide, suggestive of similarities between the toxins and mammalian collagenases as well as thermolysin. Mechanisms for inhibition of the enzymes were investigated using amino acid hydroxamates, chloromethyl esters, phosphoramidon and the peptide NH2-Ala-Leu-Tyr-Leu-COOH. All of these inhibitors had Ki values in the 10(-4) M range.

Binding Sites↗
PubMed1986

The control of fibrogenesis: stimulation and suppression of collagen synthesis in the chick chorioallantoic membrane with fibrin degradation products, wound extracts and proteases.

The chick chorioallantoic membrane model (CAM) has previously been used to demonstrate cell proliferation, characteristic of both angiogenesis and fibrogenesis, after exposure to fibrin degradation products. This model has now been adapted for quantitative in vivo assay of collagen polypeptide synthesis and prolyl hydroxylase activity. The CAM exhibits oscillations in the level of labelled collagen, a pattern attributable to rapid intracellular degradation and proline recycling following a brief labelling period. Both collagen synthesis and prolyl hydroxylase activity are stimulated by fibrin degradation products (less than 50 000 MW). Such stimulation occurs by 3 h and precedes the rise in general protein synthesis. Extracts of healing mouse skin wounds, rich in proteases, inhibited collagen synthesis, as did pure plasmin. Conversely, stimulation was achieved when proteolytic activity was neutralized by soybean trypsin inhibitor. These findings help to explain the observation that fibroblasts and endothelial cells proliferate and migrate centrally in an inflammatory lesion without depositing collagen, whilst in a milieu of high proteolytic activity. More peripherally, where proteases are inactivated by antiproteases in inflammatory exudate, such cell movement ceases and collagen deposition is observed.

Allantois↗
PubMed1986

Genetic studies on murine susceptibility to herpes simplex keratitis.

We studied the influence of lgh-linked genes on the development of keratopathy after corneal inoculation with herpes simplex virus (HSV). Using congenic strains of mice, we found that the lgh-1 gene locus, or genes closely linked to it, influence the clinical expression of HSV infection. Mice with the lgh-1e or lgh-1d allotype routinely developed severe keratopathy after HSV corneal inoculation, whereas congenic strains with lgh-1a or lgh-1b allotype were less susceptible. Cell-mediated immune responses to HSV also differed between susceptible and resistant murine strains. We interpret our results to imply a genetic influence on cell-mediated, acquired immune responses to HSV infection.

Animals↗
PubMed1986

The lateralization of lip-read sounds: a first look.

Two tachistoscopic studies on the lateralization of lip-read still photographs in normal right handers are reported. In the first, subjects matched a still lip photograph with a heard speech sound. A clear right hemisphere (LVF) advantage emerged, despite the phonological requirements of this task. This pattern of laterality failed to interact with the type of response (same/different) or with the status of the heard phoneme; both consonant and vowel matching showed the same pattern of LVF advantage, despite the significantly greater difficulty of consonant than vowel matching in this particular task. In the second study subjects were required to speak the sound they saw being spoken by a centrally displayed face photograph. The displayed face was chimeric; that is, one side of the face was seen saying one sound, one side another. Here, a rather complex pattern of results ensued. For the speakers seen a clear expressor asymmetry emerged; speech sounds were judged more accurately when they issued from the right side of the speaker's face. However, in the LVF, and only the LFV, accuracy in reporting chimeric face sounds correlated with speed in learning to lip-read, suggesting that the LVF is systematically involved even when task demands (speaking the response, phonological analysis, small, more central displays) do not, at first sight, suggest that they should. Taken together, these studies suggest that the right hemisphere could support some aspects of the processing of seen speech in normally hearing, normally lateralized individuals.

Adolescent↗
PubMed1986

Face recognition and lipreading. A neurological dissociation.

Two cases with medial occipitotemporal ischaemic infarction in the territory of the posterior cerebral artery are discussed; neither was aphasic. The patient with the right-sided lesion is prosopagnosic and topographagnosic and is impaired at recognizing or classifying facial expressive gestures but can lipread speech efficiently. The other patient, with only a left-sided lesion, shows no deficits in face recognition nor in the classification of faces in terms of nonverbal messages, but is alexic and impaired at lipreading. It is argued that processing faces for verbal information (lipreading) and processing faces for nonverbal information (face recognition and interpretation of emotive and gestural messages) are functionally dissociated in the human brain. Theoretical interpretations of prosopagnosia that stress a perceptual component to all types of face recognition failure may therefore be misleading, for similar stimulus processing mechanisms are likely to be required to identify a speech sound from a face as to identify a nonverbal gesture of the mouth. Only the associative properties of the task differ.

Aged↗
PubMed1986

Maximum transfusion rates in neonates and infants.

A common method of rapid transfusion in neonates and infants is to manually inject an appropriate volume of blood using a syringe connected to a 3-way tap in the infusion tubing. We measured the maximum infusion rates this technique could generate through small bore cannulae (22 ga-25 mm, 24 ga-19 mm), and compared the efficiency of a range of syringe sizes. We also compared infusion rates generated by this technique with those obtained using a pressure pump chamber in the giving set. The manual syringing technique using a 10 ml syringe was the most efficient for all the fluids tested, providing infusion rates through the 22 ga cannulae of 64 ml/min for packed cells, 73 ml/min for whole blood and 105 ml/min for 0.9% saline.

Blood Transfusion↗