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Biomedical subjects

C Thomas

Publications and source records attributed to C Thomas.

At least 325 records · Page 18Linked to original sources
PubMed1991

Restricted virus replication in the spinal cords of nude mice infected with a Theiler's virus variant.

The Daniels strain of Theiler's murine encephalomyelitis produces a chronic disease which is an animal model for human demyelinating disorders. Previously, we selected a neutralization-resistant virus variant producing an altered and diminished central nervous system disease in immunocompetent mice which was evident during the later stage of infection (after 4 weeks) (A. Zurbriggen and R. S. Fujinami, J. Virol. 63:1505-1513, 1989). The exact epitope determining neurovirulence was precisely mapped to a capsid protein, VP-1, and represents a neutralizing region (A. Zurbriggen, J. M. Hogle, and R. S. Fujinami, J. Exp. Med. 170:2037-2049, 1989). Here, we present experiments with immunoincompetent animals to determine viral replication, spread, and targeting to the central nervous system in the absence of detectable antibodies or functional T cells. Nude mice were infected orally, and the virus was monitored by plaque assay, immunohistochemistry, and in situ hybridization. Early during the infection (1 week), the variant virus induced an acute disease comparable to that induced by the wild-type virus in these nude mice. Alterations in tropism in the central nervous system were not apparent when wild-type parental Daniels strain virus was compared with the variant virus. Moreover, variant virus replicated in tissue culture (BHK-21 cells) to similarly high titers in a time course identical to that of the wild-type virus (A. Zurbriggen and R. S. Fujinami, J. Virol. 63:1505-1513, 1989). However, replication of the variant virus versus the wild-type virus within the spinal cord of athymic nude mice infected per os was substantially restricted by 6 weeks postinfection. Therefore, the reduced neurovirulence in the later stage (6 weeks) of the disease is most likely due to a diminished growth rate or spread of the variant virus in the central nervous system rather than to marked differences in viral tropism.

Animals↗
PubMed1991

Direct evidence of a role for amino acid 101 of VP-1 in central nervous system disease in Theiler's murine encephalomyelitis virus infection.

The DA virus, a member of the TO subgroup of Theiler's virus, invokes a chronic demyelinating disease in its natural host, the mouse, RNA transcripts from a cDNA clone, pDAFL3, are infectious, and the resulting virus, DAFL3, produces in mice a disease indistinguishable from that caused by the DA virus. Using oligonucleotide-directed site-specific mutagenesis, a single nucleotide, cytosine at position 3305 (viral genome), was changed in this infectious cDNA to a thymine. The mutated nucleotide is located in an area coding for a neutralizing epitope on loop II of VP-1. Virus OSM101, produced from the mutagenized plasmid pDA101, had the same growth characteristics and plaque phenotype in vitro as the virus DAFL3 produced from clone pDAFL3. However, in vivo in the mouse, virus OSM101 was markedly less neurovirulent than DAFL3. Central nervous system tissues from mice infected 4 to 6 weeks previously with the OSM101 virus contained less infectious virus and fewer infected cells than central nervous system tissues from animals infected with the control virus, DAFL3. Thus, we demonstrated that the single nucleotide change resulting in an amino acid substitution at position 101 (threonine to isoleucine) of VP-1 determines one aspect of Theiler's virus persistence and disease in mice.

Animals↗
PubMed1991

Silver-stained structures in prostatic carcinoma: evaluation of diagnostic and prognostic relevance by automated image analysis.

The comparison of the diagnostic and prognostic significance of histology, immunohistochemical parameters (PSA, PSP), and silver-stained nucleolar organizer regions (AgNORs) was estimated in paraffin sections taken of 63 prostatic carcinomas prior to therapy. AgNORs were visualized with a one-step silver staining technique with the appropiate staining time determined by preliminary staining-time series. The mean AgNOR number per cell (n) and the mean AgNOR area per silver-stained dot (A) were determined by means of an automatic image analysis system. Thereby prostatic carcinomas exhibited multiple small AgNORs within their nuclei (n = 4.7, A = 0.09 micron 2), whereas benign prostatic epithelium showed few but large silver-stained particles (n = 1.8, A = 0.27 micron 2; p less than 0.001). This relationship was then calculated as a quotient of AgNOR number and area (NQ = n/A) which provided additional information for the diagnosis of malignancy as well as survival. Univariate survival analysis disclosed a set of four variables predicting death from prostatic cancer; cribriform growth pattern, AgNOR quotient, histological grade, and PSA immunoreactivity. Of these parameters, immunoreactivity of PSA failed to prove its prognostic significance in multivariate survival analysis (Cox model). No relation to prognosis was found for the number as well as the area of AgNORs alone. Therefore, image analysis proved to be a prerequisit for the feasibility of this promising technique by providing objective and reproducible results.

Acid Phosphatase↗
PubMed1991

Angiodynography (color-coded duplex sonography) in the evaluation of vasculogenic impotence.

The penile arteries of 18 men with erectile dysfunction were examined by angiodynography (color-coded duplex sonography). Blood flow velocity was measured before and after intracavernous injection of papaverine/phentolamine. The angiodynographic findings were compared to arteriography. Normal values of peak flow velocity (after injection) were obtained from 6 men with normal arteriographic findings (deep artery greater than 25 cm/s, superficial artery greater than 30 cm/s). Angiodynography enables good imaging of the four penile arteries superior to duplex sonography. A strong correlation with the arteriographic findings could be found. Thus noninvasive angiodynography may replace penile arteriography for the routine evaluation of impotence.

Adult↗
PubMed1991

Effects of endothelin on cultured human and rat glomerular mesangial cells.

Figure 5 summarizes our results and the data in the literature with regard to both short-term signalling and long-term signalling induced by endothelin. Short-term signalling, which induces vasoconstriction, is undoubtedly mediated by multiple signals including increments of cytosolic calcium, stimulation of protein kinase C and alkalinization of the cytosol. Endothelin also activates negative feedback pathways including arachidonate release with the synthesis of vasorelaxant prostaglandins and potentiation, in a prostaglandin-dependent manner, of beta-adrenergic-stimulated adenylate cyclase. Long-term signalling is less well understood and may depend not only on phospholipase activation with subsequent changes of calcium and protein kinase C but also stimulation of other protein kinases which phosphorylate key intermediates. Endothelin stimulates the transient appearance of protooncogenes that might play a role in the induction of cellular proliferation.

Animals↗
PubMed1991

Intracarotid saline infusion improves outcome from incomplete ischemia in rats.

Previous studies suggest that rheological changes associated with ischemia may produce postischemic hypoperfusion. We tested whether intracarotid or intravenous infusions of saline improve neurological outcome from incomplete cerebral ischemia in rats. Rats were anesthetized with 1.4% isoflurane in air, and ischemia was produced by unilateral carotid artery ligation combined with hemorrhagic hypotension to 30 mm Hg for 30 minutes. Intracarotid (n = 10) or intravenous (n = 10) saline infusion (0.3 ml/min) decreased hematocrit 20% compared with control rats (n = 10). Neurological outcome was significantly improved in rats infused with intracarotid (p less than 0.05) but not intravenous saline during ischemia without a change in brain temperature. Cerebral blood flow, measured in a separate study using laser Doppler flowmetry (n = 5), decreased 70% (p less than 0.01) during carotid ligation and hypotension but was not changed by intracarotid saline infusion (p greater than 0.30). These results show that perfusion of ischemic brain with saline improves outcome by factors not related to changes in hematocrit, brain temperature, or intraischemic tissue blood flow.

Animals↗
PubMed1991

Persistence and remission of depressive symptoms in late life.

OBJECTIVE: The relation of poor health to the onset of depression symptoms in late life is well recognized, but little attention has been given to characteristics that might predict persistence or remission of depressive symptoms. In previous analyses the authors found that increasing disability and declining health preceded the emergence of depressive symptoms in older community residents and accounted for 70% of the variance explained by discriminant analyses. The aim of the present analysis was to examine the relevance of changes in health and disability to the persistence of depressive symptoms. METHOD: A representative sample of 1,855 adults aged 65 or older were assessed with the Center for Epidemiologic Studies Depression Scale at baseline. Twenty-four months later, 1,577 individuals were available for a second assessment of depressive symptoms. The characteristics of the 97 community residents whose depressive symptoms persisted over 24 months were compared to those of the 114 whose symptoms remitted. RESULTS: Changes in health, differences in age, sleep disturbance, and added formal support services accounted for more than 30% of the variance between the persistently depressed and remission groups. Advanced age and worsening health were associated with persistent symptoms, improved health with remission. CONCLUSIONS: Previous studies have indicated that untoward changes in health and disability play a major role in the onset of depressive symptoms. These findings show a substantial contribution to chronicity as well.

Activities of Daily Living↗
PubMed1991

Patterns of stability and change in health use among elderly people. Do service systems leave an imprint on behavior?

Stability and change in patterns of health service use over a 3-year period were determined for a sample of elderly people in an urban area who claimed one of five types of health service provider as a primary source of health care--a hospital, a private physician, a network model health maintenance organization (HMO), a hospital-based group practice program (G-HMO), or a preferred provider organization (PPO). Despite certain differences in use rates for individual services, the total volume of ambulatory service use was equivalent for all five groups as was the relative rank order of use of specific ambulatory services for four of the five groups. People who claimed a hospital as their primary care source had the most unique use patterns over a full range of health care services, characterized by extremely low rates of physician visits and the highest rates of visits to hospital outpatient clinics across three time periods. G-HMO members used health-related services more frequently than did all others. PPO members, at baseline, had lower rates of total and mean hospital days than other source group members except hospital users. People who changed principal source of care during the study period were most likely to report a hospital as their care source initially. Although there is much consistency in hospital and ambulatory use across groups, the persistence of certain use patterns for members of some groups suggests that health care systems can leave an imprint on the health service use of people for whom they provide regular care.

Aged↗
PubMed1991

Biosynthesis of the insulin-like growth factor-II (IGF-II)/mannose-6-phosphate receptor in rat C6 glial cells: the role of N-linked glycosylation in binding of IGF-II to the receptor.

We examined the role of N-linked glycosylation of the insulin-like growth factor-II (IGF-II)/mannose 6-phosphate (Man-6-P) receptor in binding of [125I]IGF-II to the receptor. First we studied the synthesis and posttranslational processing of this receptor in rat C6 glial cells, which have abundant IGF-II/Man-6-P receptors. Cells were pulse labeled with [35S]methionine and lysed, and the IGF-II/Man-6-P receptor was immunoprecipitated using a specific IGF-II/Man-6-P receptor antibody (no. 3637). Analysis of the immunoprecipitate by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with reduction of disulfide bonds showed a 235-kDa receptor precursor that was processed into the mature 245-kDa IGF-II/Man-6-P receptor within 2 h of chase. Digestion of the 235-kDa precursor with endoglycosidase-H (Endo H) produced a 220-kDa form, whereas the mature 245-kDa receptor was relatively resistant to cleavage by Endo H. When cells were cultured in the presence of 2 microM monensin, the 235-kDa receptor was not further processed into the mature Endo H-resistant receptor form. In addition, the presence of swainsonine in C6 glial cell cultures led to the formation of a 240-kDa receptor hybrid molecule, which was cleaved by Endo H into a 225-kDa species. When tunicamycin was present during the pulse-chase labeling experiment, a 220-kDa receptor species accumulated. This species was 205 kDa by immunoblotting when SDS-PAGE was performed under nonreducing conditions. Pure IGF-II/Man-6-P receptor was digested with N-glycosidase-F, and the digest was immunoblotted with antiserum 3637 after SDS-PAGE under nonreducing conditions. Whereas undigested receptor was a single band of 215 kDa under nonreducing conditions, digested receptor was 205 kDa. The binding affinity of IGF-II for the digested receptor was the same as the binding affinity of IGF-II for the undigested receptor. In addition, affinity cross-linking experiments showed that [125I]IGF-II also bound to the unglycosylated receptor precursor that accumulated in the tunicamycin-treated cells, and the binding affinity of IGF-II for this species was indistinguishable from the binding affinity of IGF-II for the mature receptor. We conclude that IGF-II can bind to an IGF-II/Man-6-P receptor that lacks N-linked oligosaccharides.

Acetylglucosaminidase↗
PubMed1991

Encephalo-myelo-radiculo-ganglionitis presenting as pandysautonomia.

A 68-year-old man developed pandysautonomia with severe orthostatic dysfunction, fixed heart rate, low serum levels of norepinephrine and epinephrine, absent sympathetic skin responses, and pupillary abnormalities. CSF protein was 92 mg/dl. In spite of a good recovery following corticosteroid administration, a relapse occurred, with accompanying sensory symptoms confined to both arms. Fatal sudden cardiac arrest occurred after 4 months. Autopsy revealed numerous lymphocytic infiltrates, predominantly in autonomic and sensory ganglia and, to a lesser extent, in the nerve roots, spinal cord, and brainstem without evidence for an underlying tumor. This case provides histopathologic evidence for an inflammatory etiology of panautonomic neuropathy in some patients.

Aged↗
PubMed1991

Clonidine decreases plasma catecholamines and improves outcome from incomplete ischemia in the rat.

Clonidine decreases central sympathetic activity and anesthetic requirement. We tested whether clonidine improves outcome from incomplete ischemia of the brain in rats. Control rats were anesthetized with 25 micrograms.kg-1.h-1 of intravenous fentanyl and inhalation of 70% nitrous oxide (N2O). Clonidine-treated rats received fentanyl/N2O and 10 micrograms/kg of intravenous clonidine 10 min before ischemia, which was produced by right carotid ligation combined with hemorrhagic hypotension to 35 mm Hg for 30 min. Clonidine increased plasma glucose before ischemia and decreased blood catecholamine concentrations during ischemia compared with the control group. Neurologic outcome was evaluated daily for 3 days after ischemia and histopathology was performed at the end of this period. Clonidine significantly improved neurologic outcome on each of the 3 days after ischemia. Histopathology was severe in the control group but not enough rats survived in this group for statistical analysis. The authors conclude that clonidine decreases sympathetic activity during ischemia and that this is associated with an improvement in outcome from incomplete ischemia.

Animals↗
PubMed1991

[Pulmonary metastasis of a dermatofibrosarcoma].

Progressive and recurrent dermatofibrosarcoma, described by Darier and Ferrand in 1924, is a fibrous skin tumour with essentially local malignancy. The authors report a case with pulmonary metastasis, a rare event as only 13 cases of visceral metastases have been reported in the literature. The clinical course of this case was favourable (follow-up of 5 years), in contrast with the usually pejorative nature of metastatic disease (death after several months to one year following the discovery of the first metastasis).

Fibrosarcoma↗
PubMed1991

Lymphoma developing in a patient with rheumatoid arthritis taking low dose weekly methotrexate.

We describe the occurrence of a lymphoma in a patient with rheumatoid arthritis (RA) taking weekly oral pulse methotrexate (MTX) in low doses for 33 months. This occurrence may be coincidental. There may be an increased incidence of lymphoma in RA not treated with immunosuppressive medications. However, the increasing use of MTX warrants reporting unusual events, especially malignancy. It is possible that even the mild immunosuppression that occurs with MTX therapy places patients with RA at added risk for developing lymphoproliferative diseases.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Cytogenetics of fleas (Siphonaptera: Pulicidae). 1. Rat fleas of the genus Xenopsylla.

Five populations of Xenopsylla cheopis exhibit a chromosome complement of 2n = 17, X1X2Y (male), and 2n = 18, X1X1X2X2 (female). A detailed analysis of populations of X. astia from Bombay and Trivandrum led to the identification of two distinct cytotypes which hybridisation studies indicated were sibling species. These are referred to as X. astia with a diploid chromosome number of 2n = 18, X1X2X3Y (male), and 2n = 20, X1X1X2X2X3X3 (female) and X. prasadii with 2n = 10, X1X2Y1Y2 (male), and 2n = 10 X1X1X2X2 (female). It is proposed that X. prasadii is derived from X. astia through translocation/fusion events since the average total chromosome lengths are remarkably similar in all three species.

Animals↗
PubMed1990

MK-801 reduced cerebral ischemic injury by inducing hypothermia.

The non-competitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, has been reported to prevent or attenuate ischemic brain damage in various animal models. In halothane-anesthetized gerbils it was found that an optimal dose of MK-801 (3.0 mg/kg) for providing cerebral protection also produced hypothermia (31.1 +/- 0.62 degrees C) relative to control animals (34.2 +/- 0.77 degrees C, P less than 0.01). This degree of hypothermia alone was sufficient to provide complete histological and functional protection (spatial memory) against 5 min of carotid artery occlusion. In gerbils made ischemic, but maintained at normal body temperature, a dose of 3.0 mg/kg of MK-801 provided no protection against hippocampal cell loss or spatial memory impairment. These data suggest that the protective actions of MK-801 may be due entirely to drug-induced hypothermia.

Animals↗