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Biomedical subjects

G Campbell

Publications and source records attributed to G Campbell.

At least 19 recordsLinked to original sources
PubMed1992

Structure of autonomic neuromuscular junctions in the sinus venosus of the toad.

The structure of cholinergic and adrenergic neuromuscular junctions in the sinus venosus of the toad, Bufo marinus, was determined by electron microscopy. From random sections of sinus venosus tissue it appeared that there were variable separations between cholinergic or adrenergic varicosities and the nearest sinus venosus muscle cell. However, when the structure of complete cholinergic and adrenergic varicosities was determined by examining serial electron micrographs, virtually all varicosities that lost their covering of Schwann cell were found to form an area of close apposition with an adjacent muscle cell. At the region of close apposition, the neuromuscular cleft was filled with a single layer of basal lamina to give a neuromuscular separation of about 70 nm. Synaptic vesicles within a varicosity were usually found to be concentrated towards the region of close apposition. These observations are discussed in relationship to the idea that when transmission occurs at these neuromuscular junctions the transmitters act on discrete pools of specialized subsynaptic receptors.

Animals↗
PubMed1992

Development of insulin sensitivity in rat skeletal muscle. Studies of glucose transporter and insulin receptor mRNA levels.

Expression of GLUT-4 and insulin receptor mRNAs was investigated in rat skeletal muscle by Northern hybridization. GLUT-4 mRNA was barely detectable in foetal muscle, was expressed at low levels by 1-8 days and at 2-3-fold higher levels during and after weaning (18-40 days). In contrast there was little change in insulin receptor mRNA levels prior to weaning and a reduction in mRNA abundance between 18 and 40 days. Weaning rats on to a diet rich in fat prevented the increase in GLUT-4 abundance seen between 15 and 29 days in animals weaned on a high-carbohydrate diet.

Aging↗
PubMed1992

Characterisation of an antigenically unusual virus responsible for two outbreaks of Newcastle disease in the Republic of Ireland in 1990.

Antigenic characterisation of two highly virulent virus isolates from outbreaks of Newcastle disease on two closely connected farms in County Monaghan, Republic of Ireland, in 1990 showed the viruses to be indistinguishable but unlike other Newcastle disease viruses so far tested. However, they appeared to be antigenically closest to avirulent viruses isolated from waterfowl from several countries and from chickens in Northern Ireland in 1986. Despite the antigenic differences, chickens vaccinated with a live commercial Hitchner B1 vaccine were protected against intramuscular challenge with one of the virulent isolates.

Animals↗
PubMed1992

Computerized immunoblot analyses (CIBA) of the distribution of prekallikrein and its activation products in vivo and in vitro.

The distribution of prekallikrein and the complexes of kallikrein with C1 inhibitor (C1INH), alpha 2-macroglobulin and approximately 58-kDa protein(s) (e.g. antithrombin III), differs in normal and C1INH-deficient human plasma, activated in vitro, due to different C1INH levels. Different distribution in the deficient plasma activated in vivo or in vitro, suggests different rates of complex clearance.

Antithrombin III↗
PubMed1992

Regeneration of adult rat CNS axons into peripheral nerve autografts: ultrastructural studies of the early stages of axonal sprouting and regenerative axonal growth.

If one end of a segment of peripheral nerve is inserted into the brain or spinal cord, neuronal perikarya in the vicinity of the graft tip can be labelled with retrogradely transported tracers applied to the distal end of the graft several weeks later, showing that CNS axons can regenerate into and along such grafts. We have used transmission EM to examine some of the cellular responses that underlie this regenerative phenomenon, particularly its early stages. Segments of autologous peroneal or tibial nerve were inserted vertically into the thalamus of anaesthetized adult albino rats. The distal end of the graft was left beneath the scalp. Between five days and two months later the animals were killed and the brains prepared for ultrastructural study. Semi-thin and thin sections through the graft and surrounding brain were examined at two levels 6-7 mm apart in all animals: close to the tip of the graft in the thalamus (proximal graft) and at the top of the cerebral cortex (distal graft). In another series of animals with similar grafts, horseradish peroxidase was applied to the distal end of the graft 24-48 h before death. Examination by LM of appropriately processed serial coronal sections of the brains from these animals confirmed that up to several hundred neurons were retrogradely labelled in the thalamus, particularly in the thalamic reticular nucleus. Between five and 14 days after grafting, large numbers of tiny (0.05-0.20 microns diameter) nonmyelinated axonal profiles, considered to be axonal sprouts, were observed by EM within the narrow zone of abnormal thalamic parenchyma bordering the graft. The sprouts were much more numerous (commonly in large fascicles), smoother surfaced, and more rounded than nonmyelinated axons further from the graft or in corresponding areas on the contralateral side of animals with implants or in normal animals. At longer post-graft survival times, the number of such axons in the parenchyma around the graft declined. At five days, some axonal sprouts had entered the junctional zone between the brain and the graft. By eight days there were many sprouts in the junctional zone and some had penetrated the proximal graft to lie between its basal lamina-enclosed columns of Schwann cells, macrophages and myelin debris. Within the brain, sprouts were in contact predominantly with other sprouts but also with all types of glial cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Pupillary constriction in response to light in rodents, which does not depend on central neural pathways.

We show here that the widely held belief that reflex constriction of the mammalian pupil in response to light depends exclusively upon neural pathways between eye and brain is in need of revision. We investigated the response of the pupil to light in dark-adapted rodents (golden hamsters; hooded rats; albino rats) subjected to a variety of surgical and pharmacological interventions designed to destroy or block all of the neural pathways and structures through which the reflex could be mediated. The interventions included bilateral intraorbital optic nerve section, or unilateral intracranial optic nerve section with enucleation of the contralateral eye, combined in some cases with bilateral removal of the superior cervical ganglia and/or pinealectomy; topical application of atropine; intraocular injection of tetrodotoxin (TTX). Golden hamsters and hooded rats, but not albino rats, retained an effective constriction of the pupil in response to light after all of these interventions, although the constriction was less and slower than in normal animals. These findings show that hamsters and hooded rats have both a neurally mediated fast light reflex that can be eliminated by severing connections between eye and brain, by blockade of cholinergic transmission to iris smooth muscle, and by blockade of action potentials by TTX; and a local, slower constriction in response to light, which remains after all these procedures. We have also confirmed previous observations of Bito and Turansky (1975) that pupillary constriction in response to light occurs in isolated in vitro anterior chamber preparations of hamster and hooded rat eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The autonomic innervation of the large intestine of the toad (Bufo marinus).

1. A study was made of the pelvic and the splanchnic nerve supplies to the toad large intestine. 2. Stimulation of pelvic nerve fibres in the 9th and 10th spinal nerves caused a series of contractions of the circular muscle, only the first of which was abolished by hyoscine. The entire response was blocked by d-tubocurarine. The response was not affected by capsaicin treatment. 3. Stimulation of the splanchnic nerves caused a rapid contraction followed by a prolonged relaxation. The relaxation was abolished by bretylium. The contraction was selectively antagonised by prolonged exposure to capsaicin. Splanchnic nerve stimulation also caused a slow, prolonged excitation that was abolished by bretylium. 4. Application of adrenaline caused relaxation of circularly cut strips of large intestinal wall, whereas substance P, acetylcholine, 5-hydroxytryptamine, somatostatin and galanin caused contraction. 5. The results suggest that stimulation of the pelvic nerves releases acetylcholine and a non-cholinergic co-transmitter from peripheral postganglionic neurons. Both the inhibitory response to splanchnic nerve stimulation and the subsequent slow excitation appear to be mediated by adrenergic nerves. The rapid capsaicin-sensitive excitation is likely to be due to release of substance P from antidromically activated afferent nerve fibres in the splanchnic outflow.

Animals↗
PubMed1992

Macrophage and epithelioid cell nuclear morphology in leprosy.

The spectrum of disease in leprosy is characterised by the presence of macrophages in lepromatous lesions and epithelioid cells in tuberculoid granulomas. Since changes in nuclear shape occur during macrophage activation, we have measured nuclear morphology by planimetry in biopsies across the leprosy spectrum. The results show no significant correlation of any of the parameters of nuclear morphology measured between different lesions or between biopsies from the centre and edge of the same lesion. There were no differences between the Ridley-Jopling groups. However, several parameters which measure the degree of ellipticity of the nuclei showed strong correlation with granuloma size in untreated leprosy patients. This suggests that local pressure effects may influence epithelioid cell and macrophage nuclear morphology in leprosy lesions.

Adult↗
PubMed1992

Micromechanics and mathematical modeling: an inside look at bioprosthetic valve function.

A major contributing factor in the degeneration of glutaraldehyde-treated porcine xenograft bioprostheses is tearing of the valve cusps near their commissural attachment to the supporting stent. We have been examining aortic valves at the micromechanical level, and have developed several sensitive techniques to evaluate the biomechanical changes produced by the glutaraldehyde fixation process. Additionally, we have developed a mathematical modeling technique that stimulates valve function during the entire cardiac cycle. Our micromechanical tests have shown that compressive buckling is common to all fixed tissues, occurs at physiological bending curvatures, and is likely to be the primary mode of mechanical failure of bioprosthetic valves. We have also shown that existing glutaraldehyde fixation techniques inhibit the natural internal shearing of the valve cusps, and disable the interaction of the fibrosa and the ventricularis. With our modeling technique, we have shown that flexural stresses are indeed concentrated near the valve commissures, and that appropriate modifications of the supporting stent can reduce flexural deformations. With these new, more revealing techniques at hand, prospective valve designs can be better evaluated prior to large scale animals and clinical testing.

Animals↗
PubMed1992

Bilateral aberrant internal carotid arteries.

This case report represents the first well-documented case of aberrant internal carotid arteries in both middle ears. CT and DSA can establish the diagnosis before surgical intervention. Aberrant internal carotid artery represents a rare finding in the differential diagnosis of middle ear masses. Most patients manifest either vertigo, tinnitus, or a variable hearing loss. Clinical findings include a red or blue mass behind the eardrum that may or may not be pulsatile. The otolaryngologist should be aware that this potential landmine may be obscured by serous otitis media. Once suspected, the mass should be evaluated by radiographic studies before surgical intervention.

Carotid Artery, Internal↗
PubMed1992

Nitric oxide synthase immunoactivity and NADPH diaphorase enzyme activity in neurons of the gastrointestinal tract of the toad, Bufo marinus.

The presence of nitric oxide synthase (NOS) was demonstrated immunohistochemically, and NADPH diaphorase was demonstrated by enzyme histochemistry in neurons throughout the gastrointestinal tract of the anuran amphibian, Bufo marinus. Successive staining showed that NOS immunoreactivity and NADPH diaphorase activity occurred in precisely the same subgroup of enteric neurons. Subsequent detailed studies of the distribution of these neurons were made using NADPH diaphorase histochemistry. Numerous reactive nerve cell bodies and fibres were found in the myenteric plexus from the esophagus to the cloaca. A dense innervation of the longitudinal and circular muscle layers occurred throughout the gastrointestinal tract. The lamina muscularis mucosae was only prominent in the stomach, where it was sparsely innervated. Reactive nerve cell bodies were common in the submucosa of the large intestine, less common in the small intestine and extremely rare in the stomach and esophagus. Reactive fibres contributed to subepithelial plexuses in the esophagus, colon, rectum and cloaca. It is concluded that NOS/NADPH diaphorase is conserved amongst vertebrate classes and that NO is a likely neurotransmitter in the toad gastrointestinal tract.

Amino Acid Oxidoreductases↗
PubMed1992

Provision of, and patient satisfaction with, primary care services in a relatively affluent area and a relatively deprived area of Glasgow.

This paper presents the results of a survey of the structure of general practice in two contrasting areas within Greater Glasgow health board: the south west area had a more deprived social profile at the 1981 census and higher than average all cause and selected major cause standardized mortality ratios than the health board as a whole while the north west area had a more affluent social profile at the 1981 census and lower than average all cause and selected major cause standardized mortality ratios. The general practice survey data gathered in 1989 were supplemented with data from a survey of residents of the localities in three age cohorts carried out in 1987-88, which provided information on use of services, as well as perceived accessibility of and satisfaction with them. Despite the more deprived social and mortality profile of the south west area, and greater use of services, few systematic differences in the structure of general practices were found in the two areas. These findings support other studies which suggest that the stereotype of poorly resourced, low quality primary care in inner city areas may apply in London, but not elsewhere. Respondents in both areas were equally satisfied with services and found them accessible.

Adolescent↗
PubMed1992

Synapses formed by identified retinogeniculate axons during the segregation of eye input.

The synaptic organization of identified retinogeniculate axons was studied during the prenatal development of eye-specific layers in the LGN of the cat. During this period, retinogeniculate axons undergo stereotyped morphological changes. Retinogeniculate axons originating from one eye and passing through LGN territory destined to be solely innervated by the other eye (inappropriate territory) initially give rise to many side branches. As the eye-specific layers emerge, these axons elaborate extensive terminal arbors within territory appropriate to their eye of origin and concurrently retract their side branches from inappropriate territory (Sretavan and Shatz, 1986). These transient side branches may therefore represent a morphological substrate for the observed functional convergence of inputs from the two eyes onto common LGN neurons during prenatal development (Shatz and Kirkwood, 1984). This possibility was investigated by examining whether identified axons and their side branches form synapses in inappropriate territory. Three retinogeniculate axons from two fetuses aged embryonic day 53 (E53) and E57 were filled with HRP in an in vitro preparation, prior to being processed for electron microscopy (EM). The HRP-filled axons, originating from the contralateral eye, were first reconstructed at the light microscope level. The portion of axon passing through the center of ipsilaterally innervated layer A1 was then serially sectioned and reconstructed by EM. Two sets of 450 serial EM sections revealed that all three contralateral axons established synaptic contacts in ipsilateral territory. Many of these synapses were made by side branches and a few were even formed by the main axon trunks. Both side branches and trunks formed mainly en passant asymmetrical contacts that were associated with spherical synaptic vesicles and that were apposed to immature dendritic elements and dendritic shafts. For comparison, a portion of the same E53 axon within the future contralateral layer A was also serially sectioned and reconstructed for EM. Within this contralateral zone, the E53 axon formed synaptic contacts similar to those established in the ipsilateral region, except that in the appropriate zone they contained significantly more synaptic vesicles. These results demonstrate that axons from the contralateral eye can establish synapses in territory simultaneously innervated by the ipsilateral eye, both via side branches and by means of contacts along the main axon trunk. Thus, the development of eye-specific layers is accompanied by the formation and subsequent elimination of synapses that almost certainly represent a morphological substrate for the known transient functional convergence of inputs from the two eyes.

Animals↗
PubMed1991

Myosin heavy-chain mRNA is present in both myofibrillar and subsarcolemmal regions of muscle fibres.

Hybridization in situ with riboprobes to the myosin heavy-chain slow isoform showed that, in the rat soleus muscle, the myosin heavy-chain mRNA was distributed throughout the myofibres. There was greater density of autoradiographic grains in the subsarcolemmal regions of the fibres, but there was also a considerable number of grains in the core myofibrillar region of the fibres. Microdensitometry showed that the grain density in the myofibrillar region was approximately half that in the subsarcolemmal rim; this would correspond to some 70% of the mRNA being present in the myofibrillar region. The results are consistent with the hypothesis that myosin is synthesized on polyribosomes present in the intermyofibrillar cytoplasm.

Animals↗
PubMed1991

GAP-43 in the axons of mammalian CNS neurons regenerating into peripheral nerve grafts.

Although mature mammalian CNS neurons do not normally regenerate axons after injury, it is well established that they will regrow axons over long distances into peripheral nerve implants. We have autografted segments of sciatic nerve into the brains of adult albino rats and have used light and electron microscopic immunocytochemistry to examine the distribution of the growth associated protein GAP-43 in and around the graft in the first two weeks following implantation. GAP-43 was present, 3-14 days after grafting, in small non-myelinated axonal sprouts in the brain parenchyma around the proximal tip of the graft. At 11-14 days after implantation similar sprouts within the graft itself were GAP-43 immunoreactive. The sprouts were either naked or associated with other cell processes (chiefly of Schwann cells; to a lesser extent of astrocytes). We also show that small numbers of neuronal perikarya around the tip of the graft become GAP-43 immunoreactive 11-14 days after implantation. Thus mature mammalian CNS neurons regenerating axons into a PNS graft display a marked increase in their content of GAP-43. In addition, we report that small plaques of GAP-43 reaction product are sometimes present on the plasma membranes of Schwann cells or astrocytes adjacent to immunoreactive axons, and that narrow sheet-like or filopodial processes of astrocytes, Schwann cells and possibly other non-neuronal cell types, may contain small amounts of GAP-43.

Animals↗