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Biomedical subjects

J J Mitchell

Publications and source records attributed to J J Mitchell.

At least 19 recordsLinked to original sources
PubMed2000

Overexpression of NGF ameliorates ethanol neurotoxicity in the developing cerebellum.

Transgenic mice overexpressing NGF in the central nervous system under the control of the glial fibrillary acidic protein (GFAP) promoter were exposed to ethanol via vapor inhalation on postnatal days 4 and 5 (P4-5), the period of maximal cerebellar Purkinje cell sensitivity to ethanol. Wild-type controls were exposed in a similar manner. There were no differences in body weight or size following these procedures, but the transgenic brain weights at this age were significantly greater than wild-type controls. In the wild-type animals, a significant 33.3% ethanol-mediated loss of Purkinje cells in lobule I was detected via unbiased three-dimensional stereological counting on P5. In the GFAP-NGF transgenic animals, however, the 17.6% difference in Purkinje cell number in control and ethanol-exposed animals was not significant. There was a similar difference in Purkinje cell density in both groups, which did reach statistical significance (-32.7% in wild-type ethanol-treated animals, -17% in transgenic ethanol-exposed animals). These results suggest that endogenous overexpression of neurotrophic factors, which have previously been shown to protect against ethanol neurotoxicity in culture, can serve a similar protective function in the intact animal.

Alcohol-Induced Disorders, Nervous System↗
PubMed2000

Ethanol-induced alterations in the expression of neurotrophic factors in the developing rat central nervous system.

Neonatal rats were exposed to ethanol throughout gestation, or during the early postnatal period (postnatal days 4-10 (P4-10)), and enzyme-linked immunoabsorbent assays were subsequently conducted in order to assess nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) protein content in hippocampus, septum, cortex/striatum and cerebellum. These determinations revealed that following prenatal ethanol treatment, there were significant ethanol-induced increases in NGF in P1 cortex/striatum, but no changes in any of the three neurotrophic factors (NTFs) in the other brain regions. Cortex/striatal NGF protein returned to control levels by P10. Following early postnatal exposure, BDNF was elevated in hippocampus and cortex/striatum (assessed on P10), and NGF was also enhanced in cortex/striatum at this age. Hippocampal and cortex/striatal BDNF returned to control levels by P21, but cortex/striatal NGF levels remained enhanced at this age. This NTF did not differ in ethanol and control animals by P60, however. The possible significance of elevated levels of NTFs as a function of ethanol exposure is discussed, and it is speculated that while such alterations could play a protective role, increases in these substances during critical developmental periods could also prove to be deleterious, and could even contribute to certain of the neuropathologies which have been observed following developmental ethanol exposure.

Animals↗
PubMed2000

Effect of neonatal ethanol exposure on parvalbumin-expressing GABAergic neurons of the rat medial septum and cingulate cortex.

This study was performed to determine the long-term effects of ethanol exposure during the brain growth spurt (postnatal days 4-10) on the number of parvalbumin-immunoreactive (PA+) GABAergic neurons in the adult (P60) rat medial septum and anterior cingulate cortex. Significant loss of neurons within each of these populations has previously been demonstrated following prenatal ethanol exposure. In the present study, no significant differences in the number of PA+ neurons were found in either the medial septum or the cingulate cortex when control and ethanol-exposed animals were compared. The cellular densities and volumetric measures in both brain regions were also similar in the two groups. We speculate that compensatory up-regulative mechanisms may have accounted for the protection of the PA neuronal populations in these two areas following the early neonatal exposure.

Animals↗
PubMed2000

Amelioration of ethanol-induced neurotoxicity in the neonatal rat central nervous system by antioxidant therapy.

BACKGROUND: The cerebellum of the neonatal rat is highly susceptible to ethanol, with profound loss of Purkinje cells resulting from even brief exposure during the first postnatal week. Developmental ethanol exposure previously has been shown to induce free radicals/oxidative stress processes and/or down-regulate protective antioxidants. In an earlier study, we found antioxidants protected against ethanol neurotoxicity in a tissue culture environment. The present study was designed to determine whether similar protection could be manifested in the intact animal. METHODS: Neonatal rats were administered a liquid diet via intragastric intubation on postnatal days 4 and 5 (P4-P5), the peak period of ethanol sensitivity in the developing cerebellum. The diet consisted of milk formula with 12% ethanol, the isocaloric substitution of maltose-dextrin for ethanol, or ethanol plus the antioxidant vitamin E. Unbiased three-dimensional counting was utilized to analyze Purkinje cell numbers and density within defined volumes from these animals on P5. RESULTS: These determinations revealed a substantial loss of Purkinje cells in the ethanol-treated animals compared to controls (approximately 30-44%), but this loss was prevented by the inclusion of vitamin E (601U/100 ml) in the diet. A lower concentration of the antioxidant (301U/100 ml) was not effective in this regard, however. CONCLUSIONS: These results suggest that ethanol-related cerebellar damage during this early postnatal period may be related to oxidative stress processes or the insufficiency of protective antioxidants. Thus, antioxidant treatment may represent a possible therapy for preventing or ameliorating the central nervous system (CNS) damage seen in the fetal alcohol syndrome.

Animals↗
PubMed1999

Vitamin E and beta-carotene protect against ethanol combined with ischemia in an embryonic rat hippocampal culture model of fetal alcohol syndrome.

Neurodevelopmental damage can occur as a result of in utero exposure to alcohol. Oxidative stress processes are one of many proposed mechanisms thought to contribute to nervous system dysfunction characterized in fetal alcohol syndrome (FAS). Therefore, this study examined neuroprotective effects of antioxidant supplementation during ethanol (EtOH) treatment (0, 200, 400, 800 or 1600 mg/dl) combined with concomitants of EtOH exposure: acute (2-h) ischemia (aISCH) and chronic (16-h) hypoglycemia (cHG). The antioxidants vitamin E and beta-carotene protected embryonic hippocampal cultures against 0-1600 mg/dl EtOH/aISCH/cHG treatments. In addition, neuronal viability, as measured by MTT ((3,4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; 5 mg/ml)), was equal to untreated cultures when supplemented with vitamin E or beta-carotene at 0-800 mg/dl or 0-200 mg/dl EtOH/aISCH/cHG, respectively. These in vitro studies mirror potential in utero ethanol-exposed CNS conditions and may lead to therapeutic strategies targeted at attenuating neurodevelopmental FAS-related deficits.

Animals↗
PubMed1999

The antioxidants vitamin E and beta-carotene protect against ethanol-induced neurotoxicity in embryonic rat hippocampal cultures.

Fetal alcohol syndrome is characterized by numerous nervous system anomalies with the developing hippocampus being highly vulnerable. Other conditions can result from maternal ethanol consumption including oxidative stress. Critical antioxidants, such as vitamin E, can be decreased and antioxidative defenses altered. Gestational day 18 rat hippocampal cultures were exposed to ethanol ranging from 400 to 2400 mg/dl (16 h). MTT assays assessed neurotoxicity. Viability was decreased dose dependently. Supplementation with vitamin E or beta-carotene afforded neuroprotection against all ethanol concentrations. Vitamin E completely ameliorated neuronal loss following 400 and 800 mg/dl ethanol. Vitamin E increased survival to 95%, 79%, 66%, and 75% during 1600, 1800, and 2000 and 2400 mg/dl ethanol compared to nonethanol treatment. Vitamin E increased viability by 38%, 23%, 12%, and 29% at 1600, 1800, 2000, and 2400 mg/dl compared to non-vitamin E-supplemented, ethanol treatment. beta-Carotene completely ameliorated cell loss from 400 mg/dl ethanol and increased survival by 18% at 1600 mg/dl and 12% at 2000 mg/dl. This study demonstrates in vitro antioxidative neuroprotection against developmental ethanol exposure and suggests that nutritional therapies incorporating antioxidants may help protect against deleterious fetal effects from maternal alcohol abuse.

Animals↗
PubMed1999

TNF-alpha and insulin, alone and synergistically, induce plasminogen activator inhibitor-1 expression in adipocytes.

Obesity is associated with hyperinsulinemia and elevated concentrations of tumor necrosis factor-alpha (TNF-alpha) in adipose tissue. TNF-alpha has been implicated as an inducer of the synthesis of plasminogen activator inhibitor-1 (PAI-1), the primary physiological inhibitor of fibrinolysis, mediated by plasminogen activators in cultured adipocytes. To identify mechanism(s) through which TNF-alpha induces PAI-1, 3T3-L1 preadipocytes were differentiated into adipocytes and exposed to TNF-alpha for 24 h. TNF-alpha selectively increased the synthesis of PAI-1 without increasing activity of plasminogen activators. Both superoxide (generated by xanthine oxidase plus hypoxanthine) and hydrogen peroxide were potent inducers of PAI-1, and hydroxyl radical scavengers completely abolished the TNF-alpha induction of PAI-1. Exposure of adipocytes to TNF-alpha or insulin alone over 5 days increased PAI-1 production. These agonists exert synergistic effects. Results obtained suggest that TNF-alpha stimulates PAI-1 production by adipocytes, an effect potentiated by insulin, and that adipocyte generation of reactive oxygen centered radicals mediates the induction of PAI-1 production by TNF-alpha. Because induction of PAI-1 by TNF-alpha is potentiated synergistically by insulin, both agonists appear likely to contribute to the impairment of fibrinolytic system capacity typical in obese, hyperinsulinemic patients.

3T3 Cells↗
PubMed1999

BDNF and NGF afford in vitro neuroprotection against ethanol combined with acute ischemia and chronic hypoglycemia.

Consumption of alcohol during pregnancy can result in central nervous system deficits in infants ranging from fetal alcohol effects to fetal alcohol syndrome. Changes in cerebral metabolism causing ischemic in utero conditions can also result from ethanol (EtOH). Growth factors have been shown to ameliorate ischemic damage and EtOH-induced neurotoxicity. However, using an in vitro model system of fetal alcohol effects/fetal alcohol syndrome, this study examines the neuroprotective effects of nerve growth factor, brain-derived neurotrophic factor, or glial cell line derived neurotrophic factor against EtOH treatment (0, 200, 400, 800, or 1, 600 mg/dl) combined with acute ischemia (2-hour hypoxia in EtOH-containing glucose-free media) followed by chronic hypoglycemia (16-hour glucose deprivation in EtOH-containing media). 3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays assessed relative neurotoxicity. Glial cell derived neurotrophic factor was not neuroprotective. Nerve growth factor protected against ischemia/hypoglycemia combined with 0-1,600 mg/dl EtOH. Brain-derived neurotrophic factor protected against ischemia/hypoglycemia combined with 0-800 mg/dl EtOH. These studies demonstrate marked growth factor neuroprotection against a myriad of conditions encountered by developing EtOH-exposed fetuses.

Acute Disease↗
PubMed1999

Insulin-induced insulin receptor substrate-1 degradation is mediated by the proteasome degradation pathway.

Insulin receptor substrate (IRS) proteins are important intracellular molecules that mediate insulin receptor tyrosine kinase signaling. A decreased content of IRS proteins has been found in insulin-resistant states in animals, humans, and cultured cells under various conditions. However, the molecular mechanism that controls cellular levels of IRS proteins is unknown. We report that chronic insulin treatment induces the degradation of IRS-1, but not IRS-2, protein in cultured cells. The insulin-induced degradation of IRS-1 can be prevented by pretreatment with lactacystin, a specific inhibitor for proteasome degradation. These data demonstrate, for the first time, that insulin-induced degradation of IRS-1 is mediated by the proteasome degradation pathway. IRS-2 can escape from the insulin-induced proteasome degradation, suggesting the existence of specific structural requirements for this degradation process.

Adenosine Triphosphatases↗
PubMed1999

Ethanol-induced alterations in neurotrophin expression in developing cerebellum: relationship to periods of temporal susceptibility.

BACKGROUND: The developing cerebellum has been shown to be profoundly affected by exposure to ethanol and to exhibit a temporal pattern of vulnerability. Cerebellar Purkinje cells are particularly susceptible to ethanol on postnatal day 4 or day 5 (P4-5), whereas this population is much less vulnerable to similar ethanol insult slightly later in the postnatal period (P7-9). The purpose of the study was to determine whether differential alterations in neurotrophic factors might be associated with this differential susceptibility. METHODS: Neonatal rats were exposed to ethanol via vapor inhalation, and enzyme-linked immunoabsorbent assays were subsequently conducted to assess cerebellar nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 protein content. These analyses were made after ethanol exposure during the period of maximal cerebellar ethanol sensitivity (postnatal days 4-5 [P4-51), during a period of much lower sensitivity (P7-8), and during the entire "brain growth spurt" (P4-10). RESULTS: These determinations revealed a significant ethanol-induced decrease in cerebellar nerve growth factor after exposure on P4-5 but not after exposure on P7-8 or P4-10. No significant changes in brain-derived neurotrophic factor or neurotrophin-3 were found with any of the exposure paradigms. CONCLUSIONS: These results suggest that alterations in nerve growth factor, which has previously been shown to support cerebellar Purkinje and granule cells, may be a mechanism contributing to the early ethanol susceptibility within these neuronar populations.

Animals↗
PubMed1998

A comparative study of ethanol, hypoglycemia, hypoxia and neurotrophic factor interactions with fetal rat hippocampal neurons: a multi-factor in vitro model developmental ethanol effects.

Fetal alcohol syndrome (FAS) is characterized by numerous central nervous system anomalies, with the hippocampus being particularly vulnerable to developmental ethanol exposure. In addition to direct ethanol neurotoxicity, other conditions resulting from maternal ethanol consumption, such as hypoglycemia and hypoxia, may also contribute to FAS. The present study used a tissue culture system to model multiple conditions which may relate to in vivo FAS, and assessed their relative neurotoxicity with MTT assays. Gestational day 18 rat hippocampal cultures were exposed to varying ethanol concentrations, glucose withdrawal-induced hypoglycemic (gwHG, 16 h) or acute hypoxic (aHP, 2 h) conditions alone, as well as to co-treatments with ethanol and gwHG or aHP. Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have previously been shown to ameliorate ethanol-, hypoglycemia- and hypoxia-induced neurotoxicity. Therefore, their neuroprotective potential, along with ciliary neurotrophic factor (CNTF), was examined. Neuronal viability was reduced dose-dependently by ethanol, alone or with hypoglycemia or hypoxia. Ethanol + gwHG or aHP was not uniformly additive. NGF treatment provided the most extensive neuroprotection, being effective against ethanol (200 and 400 mg/dl), gwHG, and aHP, alone and combined. BDNF afforded similar protection, but not against ethanol + gwHG. CNTF protected only against aHP. CNTF + BDNF, previously shown to act synergistically, protected against ethanol + aHP up to 800 mg/dl ethanol, but not, paradoxically, against ethanol alone, gwHG, or ethanol + gwHG, all conditions BDNF alone protected against. This study demonstrated that several neurotrophic factors are capable of mitigating neurotoxicity associated with ethanol, hypoglycemia and hypoxia.

Animals↗
PubMed1998

Myofibroblasts in diffuse alveolar damage of the lung.

The myofibroblast is an ultrastructurally and metabolically distinctive connective tissue cell identified as a key participant in tissue remodeling in human granulation tissue, organ fibrosis, and the fibroblastic host response to malignant neoplasms. In this study of myofibroblasts in human lung diffuse alveolar damage (DAD), we identified 36 autopsy cases in which DAD could be histologically documented. DAD is known to progress from initial injury through an exudative, proliferative, and terminal fibrotic phase. In the exudative phase (16 cases), myofibroblasts expressing alpha-smooth muscle actin (alpha-SMA) are found in the septa and less frequently in hyaline membranes. In the proliferative phase (18 cases), many myofibroblasts in septa, hyaline membranes, and intra-alveolar fibroplasia express alpha-SMA. The alpha-SMA phenotype should be used in additional studies of myofibroblast differentiation, replication, and apoptosis. A better understanding of the biology of this cell type should offer new therapy for patients with DAD.

Actins↗
PubMed1996

Twenty-year outcome analysis of genetic screening programs for Tay-Sachs and beta-thalassemia disease carriers in high schools.

Programs for education, screening, and counseling of senior-high-school students, in populations at high risk for Tay-Sachs and beta-thalassemia diseases, have existed for >20 years in Montreal. Four process and outcome variables are reported here: (i) voluntary participation rates in the high-school cohort; (ii) uptake rates for the screening test; (iii) origin of carrier couples seeking the prenatal diagnosis option in the programs; and (iv) change in incidence of the two diseases. Between 1972 and 1992, we screened 14,844 Ashkenazi-Jewish students, identified 521 HexA-deficient carriers (frequency 1:28), reached 89% of the demographic cohort in the educational component of the program, and achieved 67% voluntary participation in the subsequent screening phase. The corresponding data for the beta-thalassemia program are 25,274 students (mainly of Mediterranean origin) representing 67% of the cohort with 61% voluntary participation in the screening phase (693 carriers; frequency 1:36). From demographic data, we deduce that virtually all the carriers identified in the high-school screening program remembered their status, had their partner tested if they did not already know they were a carrier couple, and took up the options for reproductive counseling/prenatal diagnosis. In Montreal, the current origin of all couples using prenatal diagnosis for Tay-Sachs and beta-thalassemia diseases is the corresponding genetic screening/testing program, whereas, at the beginning of the programs, it was always because there was a history of an affected person in the family. Incidence of the two diseases has fallen by 90%-95% over 20 years; the rare new cases are born (with two exceptions) outside the target communities or to nonscreened couples.

Adolescent↗
PubMed1994

U-type exchange in a paracentric inversion as a possible mechanism of origin of an inverted tandem duplication of chromosome 8.

A mentally retarded male with dysmorphic features was found to have a de novo 46,XY,inv dup(8) (p.23.1-->12). Confirmation of the segments duplicated in the rearrangement was achieved by biochemical analysis of glutathione reductase, which maps to 8p21.1, and DNA studies using the chromosome specific probe y-19-1D (D85131), which maps to 8p21. Assay of cathepsin B, which has been localised to 8p22, did not differ from controls with normal chromosomal constitution. DNA studies using the Defensin 1 gene probe, which maps to 8p23, showed a previously undetected deletion of that segment. We propose that the inverted tandem duplication/deletion arose as a single U-type exchange within an inversion loop.

Abnormalities, Multiple↗