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Biomedical subjects

S M Hall

Publications and source records attributed to S M Hall.

252 records · Page 14Linked to original sources
PubMedDate not supplied

Pathogenesis of mouse scrapie. Evidence for direct neural spread of infection to the CNS after injection of sciatic nerve.

Previous studies of peripherally injected mouse scrapie suggested that invasion of the CNS occurs initially in mid-thoracic cord by neural spread of infection from spleen and other visceral sites of extraneural replication. We now show that infection of the left sciatic nerve leads to direct spread of infection to brain (at a rate of approximately 1.0-2.0 mm/day), bypassing the need for extraneural replication and thus producing shorter incubation periods. However, the efficiency of intraneural infection is low. It can be increased by crush injury or by the injection of lysophosphatidyl choline, both of which temporarily increase the surface area of axolemma exposed to inoculum. Once infection is established, agent seems to spread throughout the nervous system but, at the clinical stage of disease, the titres in the PNS are much lower than in the CNS.

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Depression and stages of change for smoking in psychiatric outpatients.

This article reports on the relations between depression and stages of change for smoking cessation. A convenience sample of 205 psychiatric outpatients (68% female, mean age 41) completed measures of depression Primary Care Evaluation of Mental Disorders [PRIME-MD] and Beck Depression Inventory-II [BDI-II]), all transtheoretical model constructs related to smoking (stages and processes of change, pros and cons of smoking, and situational temptations), and thoughts about abstinence. As hypothesized, patients who had never smoked showed substantially lower rates of currently diagnosed major depressive disorder (MDD) than those who had ever smoked. Patients in early stages of change did not show more MDD or depressive symptoms but, as hypothesized, showed more negative thoughts about abstinence. Findings are consistent with the documented association between smoking and depression and suggest the appropriateness of building smoking cessation interventions based on the transtheoretical model of change for use with psychiatric populations.

Adult↗
PubMedDate not supplied

The Schwann cell: a reappraisal of its role in the peripheral nervous system.

The Schwann cell is clearly essential for the maintenance of axonal integrity--yet we know little of the regulatory mechanisms governing its behaviour at any point in its life cycle, or of the nature of its interaction with the axons with which each Schwann cell is associated. In this article, the involvement of the Schwann cell in myelinogenesis, aspects of Schwann cell-axon recognition, the experimentally-demonstrable 'bipotentiality' of the Schwann cell and the possible functional significance of the proliferative response of the Schwann cell that occurs after injury are discussed. The isolation and preparation of pure populations of Schwann cells which can be injected or implanted into a damaged nerve, coupled possibly with the localized application of drugs to manipulate the cellular responses to injury within the nerve, represent interesting areas of recent research which may be applied in planning methods of therapeutic intervention in the treatment of peripheral nerve injury.

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The effect of 5-bromodeoxyuridine on remyelination in the peripheral nervous system of the mouse.

The thymidine analogue, 5-bromodeoxyuridine (BrdU), has been used in an attempt to manipulate experimentally the proliferative response of the Schwann cell population that follows induction of segmental demyelination in the peripheral nervous system. It was found that in the presence of BrdU, a significant number of Schwann cells displayed a susceptibility to the agent, in that they could be 'held' in the pro-myelinated state. It is suggested that there is some regulatory transition requiring the priming of the Schwann cell genome for myelination that occurs before the remyelinating phase of repair can be started, but after the establishment of the Schwann cell/axon relationship.

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The effects of multiple sequential episodes of demyelination in the sciatic nerve of the mouse.

Intraneural injections of lysophosphatidyl choline were used to examine the effects of multiple episodes of demyelination and repair in the sciatic nerves of adult mice. It was found that the early phases of repair, from initiation of myelinolysis to the appearance of promyelinated fibres, were achieved more rapidly in multiple-injected nerves than in single-injected nerves. However, this lead was temporary, since subsequent remyelination was delayed in the multiple-injected nerves until several days after it had been established in most single-demyelinated nerves. Cell-mediated demyelination was seen in multiple-injected nerves, but never in single-injected nerves. The results are discussed in terms of a the contribution of supernumerary Schwann cells to the acute stage of the programme of cellular repair; and b the possibility that the 'normal' response to an injection of LPC in a nerve which has previously undergone several episodes of demyelination is exacerbated by a local and self-limiting immune-mediated reaction.

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The effect of inhibiting Schwann cell mitosis on the re-innervation of acellular autografts in the peripheral nervous system of the mouse.

Reactive gliosis in the zone immediately proximal to transection of the sciatic nerve has been inhibited by intraneural injection of mitomycin C, an anti-mitotic agent known to arrest Schwann cell division after transection, crush or demyelination. Mitomycin C-pretreated proximal stumps were subsequently sutured to cellular or acellular autografts (0.5 cm long) and neurite growth into and within the grafts was examined during a 5-week post-operative period. Neurites grew into cellular autografts and became associated with the resident population of Schwann cells within the grafts, to the extent that remyelination was well established in the majority of Schwann cell basal lamina tubes by week 5 post-suture. In marked contrast, very few neurites grew into acellular grafts during this time, and where axons and Schwann cells were seen they tended to be grouped in 'minifascicles'. The results suggest that neurite outgrowth from proximal stumps is dependent upon active Schwann cell participation.

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Regeneration in cellular and acellular autografts in the peripheral nervous system.

The regeneration that occurs in cellular autografts of sciatic nerve has been compared with that seen in acellular models prepared either by cycles of alternating freezing and thawing, or by detergent-extraction. The responses to either fresh or pre-degenerate grafts (cellular and acellular) have been examined electron microscopically. It was found that whereas neurites grew into a fresh autograft and rapidly re-established functional relationships with vital Schwann cells lying in bands of Büngner within the graft, penetration of acellular grafts was less efficient. Many basal lamina tubes in the acellular grafts remained either empty or filled with debris-laden macrophages for the first 2 weeks after suture, although subsequently reinnervation did occur. The roles of Schwann cells, macrophages and basal laminae during reinnervation are discussed.

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Chronic experimental allergic neuritis in Lewis rats.

An experimental chronic relapsing demyelinating neuropathy was produced by immunizing adult Lewis rats with bovine myelin in low (2.5 mg) and high (5 mg) doses, with and without Mycobacterium tuberculosis in the adjuvant. Each regime produced a similar disease course: acute severe hind limb weakness was followed by apparent recovery and then reappearance of mild neurological deficit with occasional spontaneous exacerbations. The partially recovered animals were relatively resistant to reimmunization with myelin. Immunization of four-week-old rats with myelin in complete adjuvant produced disease with a similar course. Subsequent immunization of these juvenile rats with adjuvant alone precipitated exacerbations. In the late stages, the prominent changes in peripheral nerves and nerve roots were axon loss, axonal regeneration and remyelination while inflammatory cell infiltration was confined to occasional foci. Onion bulb formation was extremely common in the dorsal root ganglia and affected in particular the nerve fibres close to the dorsal root ganglion cells. The cells forming the onion bulbs resembled the satellite cells surrounding the axon hillocks. Onion bulb formation also occurred in the portion of the ventral roots adjacent to the dorsal root ganglion but was rare elsewhere. Immunocytochemistry revealed only occasional lymphocyte infiltration but there was increased Class I and Class II MHC antigen expression throughout the peripheral nervous system. The results are relevant to the interpretation of biopsies from patients with chronic demyelinating neuropathy of possible inflammatory or autoimmune origin.

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Regeneration in the peripheral nervous system.

Mammalian peripheral nerve fibres can regenerate after injury. Repair is most likely to succeed if axons are simply crushed or have only a very short (less than 0.5 cm) interstump gap to cross and most likely to fail if the interstump gap is long (greater than 1 cm) and associated with soft tissue damage. Whereas reactive axonal sprouting appears to be an intrinsic neuronal response to injury, the subsequent organization of the axonal sprouts, in particular their orderly outgrowth in minifascicles towards a distant distal stump does not occur unless Schwann cells are present. During the injury response, Schwann cells proliferate; co-migrate with regrowing axons (when the proximal stump is separated from the distal stump); respond to axonal cues by transient upregulation or re-expression of molecules which provide a favourable substrate for axonal extension; and attract bundles of regrowing axons and their associated Schwann cells across interstump gaps up to 1 cm in length. Recruited macrophages remove myelin debris from the Schwann cell tubes; they probably interact with Schwann cells in other ways during the injury response, e.g. by presenting mitogens and cytokines.

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Quitting smoking.

Four factors which influence smoking treatment outcome are identified: environmental variables, client characteristics, process variables, and specific treatment approaches. Important environmental factors are stress and social support. Of client characteristics, sex is the best predictor of treatment success. Men are more likely to quit and maintain abstinence than women. However, the majority of women alter their smoking habits during pregnancy. Low-income persons and ethnic minorities are underrepresented among subjects in treatment studies and have larger percentages of smokers in the population at large. Extraverted smokers are more likely to begin to smoke and have difficulty quitting. Also, the more anxious, poorly adjusted smoker has more trouble quitting than the less troubled smoker. The higher the client's sense of self-efficacy, the better the chance of that person entering treatment and doing well. Furthermore, smokers who take in lower levels of nicotine are more successful at quitting. Many process questions are suggested. Few have been approached empirically. The effectiveness of ex-smokers as therapists in smoking cessation programs has not been systematically investigated, even though the smoking history of therapists is a question frequently asked by clients. We suggest that the skill and empathy of group leaders is more important than smoking history. Smoking therapists should be aware of nonspecific treatment factors such as positive expectations, social reinforcement, and self-disclosure which may have a powerful influence on the efficacy of smoking treatment. Specific treatment approaches were classified into three categories: low-contact approaches, including educational, self-help, and minimal treatment approaches; psychological treatments; and pharmacological treatment. Education, self-help, and minimal treatment approaches are thought to be accretively effective when the large size of the audience is considered. Also, innovative treatments which address the influence of social support systems and physiological addition are promising treatments for individuals requiring a structured or intensive method of quitting.

Black or African American↗
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Unilateral lung transplantation: ultrastructural studies of ischemia-reperfusion injury and repair in the canine pulmonary vasculature.

UNLABELLED: The left lung was transplanted in 12 adult beagles; the donor lung had been preserved by flush perfusion of the pulmonary artery with 60 ml/kg of Euro-Collins solution at 4 degrees C then stored in Euro-Collins solution at 4 degrees C for 6 hours. Biopsy specimens were taken from control and donor left lungs before and immediately after perfusion, after 6 hours storage, and after transplantation at 4 and 24 hours (total = 46). Tissue from seven animals was injected with the tracer ruthenium red. All tissue was examined by light and electron microscopy. After preservation capillary edema developed, but ruthenium red did not penetrate junction complexes, indicating structurally intact complexes. The proportion of ruthenium red-labeled plasmalemmal vesicles decreased (p less than 0.05). Endothelial cells and type I pneumonocytes because abnormally thin and detached from the basement membrane. The epithelial, but not the endothelial, sheet was disrupted. Four hours after transplantation, edema decreased, and endothelial and epithelial cells regained a more normal shape. The proportion of labeled plasmalemmal vesicles increased (p less than 0.05) by 24 hours, when the value was similar to normal. During preservation, edema formed when alveolar capillary white cell count was normal and decreased after reperfusion when the cells increased threefold (p less than 0.001), indicating that edema was not neutrophil dependent. Many small muscular arteries constricted intensely on cold perfusion. Four hours after transplantation, these abnormalities had improved. CONCLUSION: The pulmonary vasculature showed no evidence that it had sustained additional structural injury after reperfusion. Reperfusion was associated with a gradual resolution of the structural abnormalities incurred during preservation.

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Splenic granulomas in broiler chickens produced experimentally by inoculation with Eubacterium tortuosum.

Eubacterium tortuosum, a gram-positive anaerobic filamentous bacillus, was isolated from splenic and hepatic granulomas of a 56-day-old slaughtered chicken. This isolate was injected intravenously into two groups of 2-week-old broiler chickens, which were necropsied 19 days later. Five of 15 chickens injected with 5 x 10(6) colony-forming units of a 48-hour culture of E. tortuosum developed splenic granulomas typical of those seen in chickens at slaughter. No lesions were observed in chickens given 5 x 10(5) colony-forming units of E. tortuosum or in control chickens receiving phosphate-buffered saline solution. Attempts to reisolate E. tortuosum from experimentally infected chickens were unsuccessful; however, typical filamentous organisms were observed in splenic granulomas of all five affected chickens.

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CRIS: a clinical research information system for substance abuse services at VA medical center.

The clinical research information system (CRIS) at the San Francisco VA Medical Center was designed to provide information on use of services and treatment outcomes and to support the clinics for treatment of substance abuse. This system fills a niche often neglected by centralized hospital systems, which are usually designed to satisfy administrative demands for automated fiscal functions, but not designed to support patient care. Full integration with our central computing system remains a goal; for now, CRIS operates as a self-contained clinical system with several workstations linked by a telephone network.

Computer Communication Networks↗
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Do research interviews cause distress or interfere in management? Experience from a study of cancer patients.

Research interviews with seriously ill patients are now often undertaken in quality of life research. Clinicians may be approached by researchers wishing to study their patients, and may be worried at some ethical aspects of interviewing. Concerns may include potential distress which interviews may cause, that they may interfere with the doctor-patient relationship, and perhaps, a scepticism that techniques addressing psychosocial concerns produce only 'soft' data. However, interview methods are a valuable tool for medical sociologists, nurse researchers and others. We discuss here some reflections following a study that involved interviewing severely ill patients with incurable malignant cerebral glioma. We use our observations to answer concerns and to discuss problems that arose. We suggest areas researchers and clinicians might consider before embarking on such collaboration.

Adult↗