Transplantation of microencapsulated bovine chromaffin cells reduces lesion-induced rotational asymmetry in rats

Surrounding bovine chromaffin cells by a semipermeable membrane may protect the transplanted cells from a host immune response and shield them from the inflammatory process resulting from the surgical trauma. Encapsulation of the chromaffin cells was achieved by inter-facial adsorption of a polycation on a polyanionic colloid matrix in which the chromaffin cells were entrapped. Basal and potassium-evoked release of catecholamines from encapsulated bovine chromaffin cells was analyzed over a 4-week period in vitro. Norepinephrine and dopamine release remained constant over time whereas epinephrine release significantly decreased. The chromaffin cells also retained the capacity for depolarization-elicited catecholamine release 4 weeks following the encapsulation procedure. Morphological analysis revealed the presence of intact chromaffin cells with well-preserved secretory granules. Striatial implantation of chromaffin cell-loaded capsules significantly reduced apomorphine-induced rotation compared to empty polymer capsules in animals lesioned with 6-hydroxydopamne frr at least 4 weeks. Intact chromaffin cells expressing tyrosine hydroxylase and dopamine-β-hydroxylase were observed in all capsules implanted in the striatum for 4 weeks. The assessment of the clinical potential of transplanting encapsulated adrenal chromaffin cells of either allo- or xenogeneic origin for Parkinson's disease will require long-term behavioral studies. The present study suggests, however, that the polymer encapsulation procedure may offer an alternative to adrenal autografts as a source of dopaminergic tissue.     

Adenosine release and changes in pial arteriolar diameter during transient cerebral ischemia and reperfusion

We utilized the closed cranial window technique in the anesthetized rat to determine changes in CSF concentrations of adenosine, inosine, and hypoxanthine and pial arteriolar diameter during transient (20 min) forebrain ischemia and reperfusion. After mock CSF under the cranial window was allowed to equilibrate with cerebral interstitial fluid, endogenous adenosine concentration was found to be 0.16 +/- 0.05 microM, while inosine and hypoxanthine were 0.35 +/- 0.17 and 1.23 +/- 0.47 microM, respectively. The concentration of adenosine in CSF increased 4.2-fold during ischemia and 13.8-fold during the first 5 min of reperfusion. Inosine and hypoxanthine concentrations were also significantly increased during ischemia and reperfusion. After 1 h of reperfusion, CSF adenosine and inosine levels had decreased from peak value but remained significantly above preischemic values. In contrast, hypoxanthine remained at peak concentrations even after 60 min of reperfusion. Preischemic arteriolar diameter was 42.6 +/- 11.3 microns and was not significantly changed after 20 min of ischemia. However, during the first 5 min of reperfusion, arteriolar diameter increased significantly (p less than 0.05), coincident with peak adenosine concentrations. By 60 min of reperfusion, arteriolar diameter had returned to baseline. These results indicate that during the postischemic period, adenine nucleosides and hypoxanthine in CSF are elevated and could affect reperfusion.     

Lack of sympathetic and cholinergic influences on cerebral vasodilation caused by sciatic nerve stimulation in the rat

We studied the influences of sympathetic and cholinergic mechanisms on pial arteriolar responses during cortical activation in the rat. Adult male Sprague-Dawley rats were anesthetized with alpha-chloralose and urethane and mechanically ventilated. Pial arterioles on the somatosensory cortex were visualized on a video monitor through a closed cranial window. Changes in arteriolar diameter induced by sciatic nerve stimulation (0.2 V, 5 Hz, 5 ms, for 20 s) were measured before and after (a) ipsilateral superior cervical ganglionectomy (n = 5), (b) intravenous (0.5 mg/kg) administration and topical (10(-5) M) application of atropine (n = 5), and (c) lesion of the nucleus basalis magnocellularis (the major source of intracerebral acetylcholine neurons, n = 7). Unilateral nucleus basalis magnocellularis lesions were performed stereotactically by injection of ibotenic acid (25 nmol/microliter). Sensory cortex cholinergic denervation was confirmed histologically. These treatments had no significant effect on arteriolar responses to sciatic nerve stimulation. Thus, the present results suggest that neither sympathetic nor cholinergic mechanisms play a significant role in somatosensory evoked cerebral vasodilation.     

HIV in the U.K.: problems of prevalence, sociological response and health education.

It is argued that the prevalence of AIDS is substantially under-represented in existing national AIDS data. Thus although official statistics demonstrate significant recent shifts in transmission routes for HIV, health educators are faced with a problem because it is difficult to develop preventive strategies against a syndrome whose prevalence can only be estimated. Problems of the true extent of the prevalence of HIV are compounded when there is a lack of knowledge about the specifics of heterosexual behaviour. It is unwise to assume that the protective strategies developed by gay men in the face of HIV are routinely available for adoption by heterosexuals, who are characterised by social divisions of age, gender and relative amounts of social power. These concerns represent a problem for health educators. To date, sociological work may not have made the most effective contribution in its support of intervention strategies against HIV/AIDS. Examination of the empirical literature on lay concepts of health and illness reveals a pessimistic stance on the part of some researchers about the ability of individuals to modify behaviour. More positive readings of their own data are possible. The traditional concerns to emphasise the socio-economic determinants of health and behaviour, now also shared by some health educators, should not obscure a concern for the fate of individuals. The most effective contribution that health promotion may be able to make to the control of HIV in the heterosexual population is to assist in the development of strategies of empowerment and 'horizontal intervention'.     

Analyses of T-cell differentiation from hemopoietic stem cells in the G0 phase by an in vitro method.

Using differential radiation sensitivity of components of mouse embryonal thymus, an in vitro method for studying T-cell differentiation from hemopoietic stem cells (HSCs) in the G0 phase was established. Intrathymic T-cell precursors present in embryonal thymus were found to be quite radioresistant (up to 20 Gy), and consequently 25-Gy-irradiated embryonal thymic lobes were used. Thymic lobes (25-Gy irradiated) taken from mouse fetuses (gestation day 15) were placed in Millipore-HA culture plates supported on squares of gelatin foam sponge in 24-well culture plates in which neonatal thymus stromal cells were cultured. HSCs (10(5) cells per well) in the G0 phase were added to these thymic lobes and cocultured at 37 degrees C in a 5% CO2/95% air incubator. Half the culture medium was changed every week. After 3 weeks, a large number of colonies had formed. Immunohistochemical studies and fluorescence-activated cell sorter analyses revealed that the colonizing cells regularly develop and exhibit surface markers characteristic of T cells (Thy-1, IL-2R, L3T4, Lyt-2, etc.). In situ hybridization analyses revealed that mRNA expression for T-cell receptor (TCR) beta chains occurred within colonizing cells. Using a monoclonal antibody (F23.1), expression of TCR beta-chain variable domain (V beta 8) on the surface of these developing T cells was demonstrated. These cells responded to interleukin 2 and/or anti-CD3 monoclonal antibody, indicating functional T cells. This method will be useful in studying T-cell differentiation pathways from pluripotent HSCs and in clarifying the mechanisms involved in negative and positive selection of T cells within the thymus.     

Interactions of human phagocytes with moulds Fusarium spp. and Verticillium nigrescens possessing different pathogenicity.

Fusarium spp. are emerging as important causes of invasive fungal infections. They tend to have decreased susceptibility to antifungal agents, making host defences very important. The ability of human phagocytes to cause damage to hyphae of Fusarium solani, F. oxysporum and Verticillium nigrescens, a mould with very low pathogenicity, was assessed using the 2,3-bis[2-methoxy-4-nitro-5-sulphophenyl]2H-tetrazolium-5-carboxanilide (XTT) metabolic assay. The oxidative burst, evidenced as superoxide anion (O2-) production, of phagocytes in response to hyphae was also investigated, as well as phagocytosis of conidia by monocyte (MNC)-derived macrophages (MDM). Hyphal damage by polymorphonuclear leukocytes (PMNL) and MNC showed a linear trend increasing with effector cell:target cell (E:T) ratio. Although no significant differences were observed for PMNL, MNC-induced damage to F. solani hyphae was lower than that seen with F. oxysporum hyphae at an E:T ratio of 20:1 and with V. nigrescens hyphae at ratios of 1:1, 5:1 and 20:1 (P < 0.05). In contrast, levels of O2- production by phagocytes in response to F. oxysporum were lower than those induced in response to the other fungi (P < 0.01). The average number of V. nigrescens conidia ingested by MDM was higher than that of conidia of the other fungi (P < 0.01). Phagocytes respond to the test fungi differentially, with F. solani being the least susceptible to damage by MNC. This may correlate with the observation that, compared to the other fungi studied, it causes a relatively high incidence of infections in neutropenic patients.     

Lassa virus hepatitis. Observations on a fatal case from the 1972 Sierra Leone epidemic.

During a recent outbreak of Lassa fever in Sierre Leone, a 20-year-old woman developed an acute febrile disease with tonsillar exudates and hemorrhagic manifestations. Lassa virus was isolated in cell cultures from pharyngeal secretions and pleural fluid and was identified by complement fixation. Typical arenavirus particles were observed in these infected cell cultures. In a liver biopsy specimen, diffuse hepatocellular damage and focal necroses were evident, with a spectrum of liver cell change, ranging from slight vacuolizaiton to frank lysis. Virus was frequently observed in nearby extracellular spaces and was clearly associated with hepatocytes rather than sinusoidal cells. The demonstration for the first time of Lassa virus particules in human tissue provides direct evidence that the virus is responsible for the observed pathologic changes.     

Monochloramine enhances Fas (APO-1/CD95)-induced apoptosis in Jurkat T cells

Monochloramine derivatives are physiological oxidants produced by activated neutrophils. We report the effects of chemically prepared monochloramine (NH2Cl) on Fas-induced apoptosis in Jurkat T cells. When the cells were pretreated with NH2Cl (20-70 microM), subsequent addition of apoptosis-inducing anti-Fas antibody resulted in a synergistic enhancement of apoptosis. Treatment of NH2Cl (50-70 microM) alone resulted in a slight but definite apoptosis. Caspase activities, as measured by DEVD and IETD cleavage activities, were also elevated synergistically by NH2Cl + anti-Fas antibody stimulation. Moreover, a broad caspase inhibitor, Z-VAD-fmk, almost completely inhibited the apoptosis induced by NH2Cl and/or anti-Fas antibody. Fas expression on the Jurkat cell surface was not affected by the NH2Cl treatment. After 3 h of NH2Cl treatment, when the apoptosis was beginning to increase, the cells showed cytochrome c release from mitochondria, proteolytic activation of caspase 9, and poly (ADP-ribose) polymerase cleavage, regardless of Fas stimulation. Z-VAD-fmk almost completely inhibited this poly (ADP-ribose) polymerase cleavage, but not cytochrome c release. By contrast, Fas stimulation alone resulted in neither cytochrome c release nor caspase 9 activation at 3 h, and the increase in the DEVD cleavage activity and apoptosis became evident at later time points. These results suggested that NH2Cl enhanced Fas-induced apoptosis through the cytochrome c release and caspase 9 activation at the early stage of apoptosis. Chloramines derived from acute inflammation may modify immune reactions, such as cell-mediated cytotoxicity and some autoimmune diseases, by the enhancement of Fas-induced apoptosis.     

Online measurement of ocular accommodation using a low-cost microcomputer system

The paper describes a low-cost system for the measurement of ocular accommodation. Digitisation of the low-frequency signals obtained from the measurement is straightforward and high-speed methods are not necessary. The methods described are, therefore, of interest to workers involved in the study of low-frequency signals, which are common in biological systems.