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Biomedical subjects

D Martin

Publications and source records attributed to D Martin.

At least 37 records · Page 2Linked to original sources

GDNF enhances dopaminergic cell survival and fibre outgrowth in embryonic nigral grafts.

Two groups of rats with unilateral 6OHDA lesions received either intrastriatal suspension grafts of embryonic ventral mesencephalon or sham grafts. Three subgroups of each of these received intrastriatal infusions of 1000 ng or 500 ng glial cell-line derived trophic factor (GDNF) or vehicle alone for 10 consecutive days. There was a highly significant dose-dependent effect of GDNF both on the number of TH-positive cells surviving in the grafts and on the density of fibre outgrowth. All grafted rats showed rapid compensation of amphetamine-induced rotation compared with rats with sham grafts. GDNF may provide a powerful tool to enhance the survival and maturation of dopaminergic neurones within mesencephalic transplants.

Animals

Inhibition of tumor necrosis factor-alpha reduces focal cerebral ischemic injury in the spontaneously hypertensive rat.

Tumor necrosis factor-alpha (TNF-alpha) is acutely expressed following focal cerebral ischemia, but its pathophysiological role remains to be extensively characterized. In this study we determined the effect of inhibiting TNF-alpha on the microvascular perfusion impairment and ischemic injury induced by permanent middle cerebral artery occlusion (MCAO). TNF-alpha activity was inhibited with recombinant type I soluble TNF receptor (TNFbp; 1 mg/kg i.v., 0.5 h pre- or post-MCAO). TNFbp significantly attenuated the microvessel perfusion impairment observed in vehicle treated rats, particularly in perifocal/penumbral regions of cortex, and significantly reduced (by 34-38%) the total volume of ischemic injury. These results demonstrate that TNF-alpha contributes to focal ischemic injury and that inhibition of TNF-alpha can confer dramatic neuroprotection. The association of the neuroprotective effect of TNFbp with improved microvascular perfusion suggests that inflammatory and vascular responses to TNF-alpha contribute to its pathological action.

Animals

Alpha-MSH stimulates neurite outgrowth of neonatal rat corticospinal neurons in vitro.

Peptides related to melanocortin (alpha MSH) and corticotropin (ACTH), collectively termed melanocortins, exert trophic effects on the outgrowth of neurites from peripheral and central nervous system in vitro. Here we study the neurite outgrowth promoting effect of alpha-MSH on corticospinal (CS) neurons in vitro. Corticospinal neurons were identified in cell culture of neonatal rat cortex by immunostaining of cholera toxin subunit B (CTB), retrogradely transported from the cervical parts of the spinal cord. The CTB-immunoreactive neurons represent a small percentage (3-5%) of the total cell population after 72 h in vitro. The axons or dendrites of cortical and CTB-labelled layer V neurons were visualized using antibodies against axon- or dendrite-specific markers and measured using a semi-automatic quantification device. Here we report that alpha-MSH stimulates axonal as well as dendrite outgrowth from both total and CTB-labelled neurons with a bell-shape response curve. Axonal outgrowth of CTB-labelled neurons was dose-dependently stimulated with a maximal effect of 50% at 10(-10) M alpha-MSH. The maximal effect for stimulation of axon outgrowth for the total cortex population was observed at 10(-8) M alpha-MSH. In addition dendrite outgrowth of both total and CTB-labelled neurons is stimulated in a dose-dependent manner with maximal effects (varying between 46 and 48%) at 10(-8) M alpha-MSH. Explanations in the shift for the optimal alpha-MSH concentration for stimulation of axonal outgrowth of CTB-labelled layer V neurons as compared to total cortex neurons are discussed.

Animals

Tumor escape from immune recognition: lethal recurrent melanoma in a patient associated with downregulation of the peptide transporter protein TAP-1 and loss of expression of the immunodominant MART-1/Melan-A antigen.

In the last few years, mutiple protein target antigens for immunorecognition by T cells have been identified on human melanoma. How melanoma lesions escape from functional antigen-specific immune recognition remains poorly understood. We have identified the concomitant loss of the immunodominant T cell-defined MART-1/Melan-A antigen and downregulation of the TAP-1 gene in a recurrent metastatic melanoma that was resected in 1993. This phenotype was not observed for an earlier autologous melanoma lesion resected in 1987. The "antigen loss" could be restored in the variant tumor cell line by simultaneously providing both the MART-1/Melan-A gene (by retroviral transfer) and the TAP-1 gene (by a bioballistic approach) resulting in tumor cell sensitivity to MART-1/Melan-A-specific cytotoxic T lymphocytes. This suggests that tumor escape from immune surveillance may have occurred in vivo as a sequential result of (a) antigen loss, and (b) downregulation of the peptide-transporter protein TAP-1 expression by this patient's tumor over a 6-yr period from 1987 to 1993. These results suggest that the characterization of the T cell response to melanoma in individual patients and definition of the immunologically relevant genetic defects in tumors may be required to select the most effective therapeutic strategies for a given patient.

ATP Binding Cassette Transporter, Subfamily B, Mem

Deprivation payments to general practitioners: limitations of census data.

The census data from which deprivation payments have been calculated since June 1995 suffer from limitations including underenumeration; under counting of homeless people and refugees, and artefactual errors because of the way in which the 1991 census data were tabulated. These limitations reduced the fairness of the changes that many practices experienced in their deprivation payments. The validity of the current system of deprivation payments would be improved if these limitations were borne in mind when allocating payments to practices and if enumeration districts were used as the basis of payments rather than electoral wards.

Catchment Area, Health

Effects of Schwann cell transplantation in a contusion model of rat spinal cord injury.

Cultured Schwann cells were transplanted at various delays into a spinal cord contusion injury performed at low thoracic level in adult female rats. The Schwann cells were purified from the dorsal root ganglia of adult syngeneic animals. the transplants were well tolerated, and the transplanted Schwann cells invaded the injured spinal cord. As quantified using video image analysis, the survival and growth of the transplanted cells were poor when the grafting procedure was performed 3-4 days after injury and very good when performed immediately or 10 days after injury, in which cases post-traumatic micro- and macrocavitation were strongly reduced. In animals grafted immediately after injury but not in animals grafted after 10 days, post-traumatic astrogliosis was much reduced. The Schwann cells transplanted area was invaded by numerous regenerating axons, the vast majority of which were, based on the neurotransmitter (CGRP and SP) profile, originating from dorsal root ganglion. No regeneration of the corticospinal tract as assessed after anterograde tracing or of descending aminergic fibers could be demonstrated.

Animals

Omega-3 polyunsaturated fatty acids increase purine but not pyrimidine transport in L1210 leukaemia cells.

Here we show that in vitro supplementation of L1210 murine lymphoblastic leukaemia cells with n-3 polyunsaturated fatty acids results in considerable changes in the fatty acid composition of membrane phospholipids. Incubations for 48 h with 30 microM eicosapentaenoic acid (20:5, n-3; EPA) or docosahexaenoic acid (22:6, n-3; DHA) results primarily in substitution of long chain n-6 fatty acids with long-chain n-3 fatty acids. This results in a decrease in the n-6/n-3 ratio from 6.9 in unsupplemented cultures to 1.2 or 1.6 for EPA and DHA supplemented cultures, respectively. Coincident with these changes in membrane fatty acid composition, we observed a 5-fold increase in the rate of adenosine (5 microM) uptake via a nitrobenzylthioinosine (NBMPR)-sensitive nucleoside transporter in EPA- and DHA-supplemented L1210 cells, relative to unsupplemented cells. This seemed to result from a decrease in the Km for adenosine from 12.5 microM in unsupplemented cultures to 5.1 microM in DHA-treated cultures. Guanosine (50 microM) transport was similarly affected by DHA with a 3.5-fold increase in the initial rate of uptake. In contrast, pyrimidine transport, as measured by uptake of thymidine and cytidine, was not similarly affected, suggesting that substrate recognition had been altered by fatty acid supplementation. Studies using [(3)H]NBMPR showed that there was no effect of EPA or DHA on either the number of NBMPR-binding sites or the affinity of these sites for NBMPR. This observation suggests that the increases in adenosine and guanosine transport were not due to increases in the number of transported sites but rather that EPA and DHA directly or indirectly modulate transporter function.

Animals

Human intestinal Vdelta1+ lymphocytes recognize tumor cells of epithelial origin.

gammadelta T cells can be grouped into discrete subsets based upon their expression of T cell receptor (TCR) variable (V) region families, their tissue distribution, and their specificity. Vdelta2+ T cells constitute the majority of gammadelta T cells in peripheral blood whereas Vdelta1+T cells reside preferentially in skin epithelium and in the intestine. gammadelta T cells are envisioned as first line host defense mechanisms capable of providing a source of immune effector T cells and immunomodulating cytokines such as interleukin (IL) 4 or interferon (IFN) gamma. We describe here the fine specificity of three distinct gammadelta+ tumor-infiltrating lymphocytes (TIL) obtained from patients with primary or metastatic colorectal cancer, that could be readily expanded in vitro in the presence of IL-1beta and IL-7. Irrespective of donor, these individual gammadelta T cells exhibited a similar pattern of reactivity defined by recognition of autologous and allogeneic colorectal cancer cells, renal cell cancer, pancreatic cancer, and a freshly isolated explant from human intestine as measured by cytolytic T cell responses and by IFN-gamma release. In contrast, tumors of alternate histologies were not lysed, including lung cancer, squamous cell cancer, as well as the natural/lymphocyte-activated killer cell-sensitive hematopoietic cell lines T2, C1R, or Daudi. The cell line K562 was only poorly lysed when compared with colorectal cancer targets. Target cell reactivity mediated by Vdelta1+ T cells was partially blocked with Abs directed against the TCR, the beta2 or beta7 integrin chains, or fibronectin receptor. Marker analysis using flow cytometry revealed that all three gammadelta T cell lines exhibit a similar phenotype. Analysis of the gammadelta TCR junctional suggested exclusive usage of the Vdelta1/Ddelta3/Jdelta1 TCR segments with extensive (< or = 29 bp) N/P region diversity. T cell recognition of target cells did not appear to be a major histocompatibility complex restricted or to be correlated with target cell expression of heat-shock proteins. Based on the ability of some epithelial tumors, including colorectal, pancreatic, and renal cell cancers to effectively cold target inhibit the lysis of colorectal cancer cell lines by these Vdelta1+ T cell lines, we suggest that intestinal Vdelta1+ T cell lines, we suggest that intestinal Vdelta1+ T cells are capable of recognizing cell surface Ag(s) shared by tumors of epithelial origin.

Amino Acid Sequence

Functional recovery in parkinsonian monkeys treated with GDNF.

Parkinson's disease results from the progressive degeneration of dopamine neurons that innervate the striatum. In rodents, glial-cell-line-derived neurotrophic factor (GDNF) stimulates an increase in midbrain dopamine levels, protects dopamine neurons from some neurotoxins, and maintains injured dopamine neurons. Here we extend the rodent studies to an animal closer to the human in brain organization and function, by evaluating the effects of GDNF injected intracerebrally in rhesus monkeys that have had the symptomatology and pathophysiological features of Parkinson's disease induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The recipients of GDNF displayed significant improvements in three of the cardinal symptoms of parkinsonism: bradykinesia, rigidity and postural instability. GDNF administered every four weeks maintained functional recovery. On the lesioned side of GDNF-treated animals, dopamine levels in the midbrain and globus pallidus were twice as high, and nigral dopamine neurons were, on average, 20% larger, with an increased fibre density. The results indicate that GDNF may be of benefit in the treatment of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Pre-operative visits to reduce patient anxiety: a study.

The aim of this study was to evaluate the effect of pre-operative visits by theatre nurses on pre- and post-operative levels of anxiety in two groups of general surgical patients, and to see if the outcome was reflected in the level of post-operative pain, nausea, mobility or length of hospitalisation. One group received pre-operative visits while the other group did not. Results of the study showed a significant decrease in anxiety 24 to 72 hours post-operatively for the visited group. A positive relationship between pre-operative anxiety levels and the level of pain, nausea and lack of independence experienced by both groups was also found. Length of hospitalisation was unaffected by the level of anxiety experienced in both groups. The author recommends that all surgical patients should receive a visit from theatre nurses before their operation.

Anxiety

Changes in plasma HIV-1 RNA and CD4+ lymphocyte counts and the risk of progression to AIDS. Veterans Affairs Cooperative Study Group on AIDS.

BACKGROUND: Clinical trials of antiretroviral drugs can take years to complete because the outcomes measured are progression to the acquired immunodeficiency syndrome (AIDS) or death. Trials could be accelerated by the use of end points such as changes in CD4+ lymphocyte counts and plasma levels of human immunodeficiency virus type 1 (HIV-1) RNA and beta 2-microglobulin, but there is uncertainty about whether these surrogate measures are valid predictors of disease progression. METHODS: We analyzed data from the Veterans Affairs Cooperative Study on AIDS, which compared immediate with deferred zidovudine therapy. Patients' plasma levels of HIV-1 RNA and beta 2-microglobulin were measured in stored plasma. RESULTS: Among the 129 patients in the immediate-treatment group, 34 had disease that progressed to AIDS, as compared with 57 of the 141 patients in the deferred-treatment group (P = 0.03). Progression to AIDS correlated strongly with base-line CD4+ lymphocyte counts (P = 0.001) and plasma levels of HIV-1 RNA (P < 0.001), but not with base-line levels of beta 2-microglobulin (P = 0.14). A decrease of at least 75 percent in the plasma level of HIV-1 RNA over the first six months of zidovudine therapy accounted for 59 percent of the benefit of treatment, defined as the absence of progression to AIDS (95 percent confidence interval, 13 to 112 percent). Plasma beta 2-microglobulin levels and CD4+ lymphocyte counts explained less of the effect of treatment. A 75 percent decrease in the plasma HIV-1 RNA level plus a 10 percent increase in the CD4+ lymphocyte count could explain 79 percent of the treatment effect (95 percent confidence interval, 27 to 145 percent). CONCLUSIONS: Treatment-induced changes in the plasma HIV-1 RNA level and the CD4+ lymphocyte count, taken together, are valid predictors of the clinical progression of HIV-related disease and can be used to assess the efficacy of zidovudine and possibly other antiretroviral drugs as well.

Acquired Immunodeficiency Syndrome

Intrastriatal injection of GDNF attenuates the effects of 6-hydroxydopamine.

Our study was designed to determine whether intrastriatal administration of glial cell line-derived neurotrophic factor (GDNF) can attenuate the behavioral effects and injury to the mesostriatal dopaminergic system caused by 6-hydroxydopamine (6-OHDA). Four groups of rats received a series of four intrastriatal injections of vehicle or one of three doses of GDNF (0.1, 1 or 10 micrograms per injection) on days 1,3,5 and 8. On day 4 the animals received a single, intrastriatal injection of 25 micrograms 6-OHDA. Treatment with GDNF significantly reduced the development of amphetamine-induced rotation, and the dose of 1 microgram per injection appeared to be the most effective. The group treated with this dose had significantly greater preservation of tyrosine hydroxylase-immunoreactive (TH-IR) fibers adjacent to the injection site in the striatum and significantly greater preservation of Nissl-stained and TH-IR neurons in the substantia nigra pars compacta (SNpc).

Amphetamine

Peripheral administration of Interleukin-1 Receptor antagonist inhibits brain damage after focal cerebral ischemia in the rat.

We assessed the efficacy of recombinant human interleukin-1 receptor antagonist (rhIL-1ra) on brain injury and edema formation after permanent middle cerebral artery occlusion (MCAo) in the rat. Previous studies showed that low amounts of rhIL-1ra injected directly into the brain significantly decreased infarct size after MCAo or excitotoxic injury in rats. Peripheral administration of rhIL-1ra (100 mg/kg sc at 0, 4, 8, 12, and 18 h after MCAo) significantly inhibited infarct size, by 46% (P < 0.05), measured at 24h. This was greater than the effect of MK801 administered immediately after MCAo (4 mg/kg ip, 0 h) which did not significantly reduce infarct size. rhIL-1ra (100 mg/kg also significantly inhibited cerebral edema formation by 49% (p< 0.05 measured 24 h after MCAo, but did not reduce edema formation measured 2 h after MCAo, but did not reduce edema formation measured 2 h after MCAo. Inhibition of infarction by rhIL-1ra was dependent on dose and time of administration. Together the results demonstrate that peripherally administered rhIL-1ra at high doses is able to mimic the efficacy of low dose of rhIL-1ra administered directly into the brain in a rodent model of stroke and that protection observed with rhIL-1ra was better than that offered by MK801 in this model.

Animals

The role of cyclooxygenase and 5-lipoxygenase metabolites in potentiated endothelin-1-evoked contractions in bovine bronchi.

We have previously shown that angiotensin II (AII) potentiates responses evoked by endothelin-1 (Et-1). In the present study, the additional ability of hypoxia or phorbol 12, 13-dibutyrate (PDBu) to evoke hyperreactivity was examined. In addition, the role of cyclooxygenase and 5-lipoxygenase metabolites of arachidonic acid in the potentiation evoked by AII, hypoxia or PDBu was studied, using indomethacin and nordihydroguaiaretic acid (NDGA). The involvement of protein kinase C in the enhanced response was examined using staurosporine. Contractions were measured isometrically from rings of bovine bronchi. Contractions evoked by Et-1 alone were unaltered by indomethacin (10(-6)M), NDGA (10(-5)M) or staurosporine (3 x 10(-8)M). AII (3 x 10(-7)M), hypoxia (4% O2) or PDBu (10(-8)M) each significantly potentiated the contractions evoked by Et-1. Indomethacin (10(-6)M) virtually abolished the effect of AII, hypoxia or PDBu. NDGA (10(-5)M) reversed the potentiating effect of both AII and hypoxia and partially reversed PDBu-evoked enhancement of Et-1-mediated responses. Staurosporine (3 x 10(-8)M) abolished the ability of AII or PDBu, but not hypoxia, to enhance Et-1-mediated contractions. In conclusion, AII, hypoxia and PDBu evoke hyperresponsiveness which is mediated by prostanoids and/or leukotrienes, the precise nature of which remains to be elucidated. Differences in the ability of staurosporine to reverse AII- and hypoxia-induced hyperreactivity suggests, however, that these conditions may generate different eicosanoids.

Animals

Metabolic intermediates in lactic acidosis: compounds, samples and interpretation.

A number of acquired conditions including infections, severe catabolic states, tissue anoxia, severe dehydration and poisoning can give rise to hyperlactacidaemia. All these causes should be ruled out before considering inborn errors of metabolism. Carefully collected samples are necessary if artefacts that result in spuriously increased lactate/pyruvate (L/P) and 3-hydroxybutyrate/acetoacetate (B/A) ratios are to be avoided. When properly performed, 24-h studies of L/P and B/A ratios provide a useful tool in making a diagnosis. A few metabolic profiles when present are specific or highly suggestive of a given disorder. When the L/P ratio is normal or low, pyruvate dehydrogenase (PDH) deficiency is highly probable whatever the lactate concentration, which is often only moderately elevated after meal, may be. When the L/P ratio is very high in association with post-prandial hyperketonaemia and in contrast to a normal or low B/A ratio, pyruvate carboxylase (PC) deficiency and alpha-ketoglutarate dehydrogenase (KGDH) deficiency are the most likely diagnoses. The distinction between the two disorders relies upon amino acid and organic acid profiles (glutamate and alpha-ketoglutarate accumulations in KGDH deficiency and hyperammonaemia and hypercitrullinaemia in PC deficiency). When both L/P and B/A ratios are elevated and associated with significant post-prandial hyperketonaemia, respiratory-chain disorders should first be suspected. All other profiles, especially a high L/P ratio without hyperketonaemia, are compatible with respiratory-chain disorders but are not specific; all acquired anoxic conditions should also be ruled out. Clearly, the clinical utility of these profiles needs to be interpreted cautiously in very ill patients in relation to the cardiocirculatory condition and to therapy. Finally, a normal profile, even after stress and loading, does not rule out an inborn error of lactate/pyruvate oxidation.

Acidosis, Lactic

Clinical experience with synthetic serum substitute as a protein supplement in IVF culture media: a retrospective study.

OBJECTIVE: Our objective was to evaluate the efficacy of Synthetic Serum Substitute (Irvine Scientific--Materials Section, Santa Ana, CA), a globulin-enriched protein preparation containing human serum albumin for supplementation of IVF culture media. DESIGN: We retrospectively analyzed IVF cycles performed at MacDonald Womens Hospital between January 1992 and November 1994. IVF cycles were reviewed and classified according to the nature of protein supplementation used in the embryo culture medium. Three protein supplements utilized during this time period were compared: Synthetic Serum Substitute (SSS), Plasmanate (PL), and maternal serum (MS). RESULTS: Although clinical pregnancy rates among the three treatment groups were not statistically different, there was a definite trend toward a higher pregnancy rate with SSS supplementation (SSS, 38.2%; MS, 28.0%; and PL, 24.9%). Embryos grown in SSS-supplemented culture media had a significantly higher implantation rate (17.8 vs 10.4 and 10.3%, respectively, for MS and PL). Preliminary data also suggest that human embryo development and blastulation in vitro were enhanced by this protein supplement. CONCLUSIONS: The higher implantation rate with SSS suggests that it may be superior to both maternal serum and Plasmanate in supporting human embryo development in vitro. Whether blastocysts derived from PL- and SSS-supplemented media are able to implant and give rise to clinical pregnancies remains to be seen.

Adult