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Biomedical subjects

A Leon

Publications and source records attributed to A Leon.

At least 127 records · Page 7Linked to original sources
PubMed1991

Disturbances of affect expression in failure-to-thrive.

Positive and negative affects were assessed in 28 6- to 36-month-old children with failure-to-thrive and 14 normally growing children in feeding and nonfeeding situations. The roles of malnutrition and severity of organic effects also were examined. Failure-to-thrive children expressed less positive affect in the feeding and nonfeeding situations and more negative affect in feeding than normally growing children. Among failure-to-thrive children, the presence of both acute and chronic malnutrition was associated with heightened negative affect during feeding, whereas the degree of organic contribution had no effect. These results, if replicated, may have implications for clinical assessment and are discussed in terms of current theories of failure-to-thrive.

Affective Symptoms↗
PubMed1991

Tumor-associated trypsin inhibitor (TATI) in primary esophageal carcinoma.

Esophageal carcinoma has a catastrophic clinical course with a very low 5 year survival rate of 5%. A circulating tumor marker with good specificity and sensitivity would be useful in the management strategy of the disease. So far, no tumor marker effective in esophageal carcinoma has been identified. Preliminary reports suggest satisfactory positivity rates of tumor-associated trypsin inhibitor (TATI) in esophageal carcinoma. We measured TATI levels in 71 patients with primary squamous cell esophageal carcinoma as well as in 30 tissue samples from both carcinoma and normal esophageal mucosa. Detectable TATI levels were not found in tumor tissue samples. The marker showed significantly higher serum levels in patients than in controls, with an overall positivity rate of 28%. TATI levels were significantly lower in patients with a high number of tumor-positive lymph nodes. No relationship was found between TATI and several other clinical and pathological parameters. High TATI levels correlated with a lower probability of overall survival as well as in cases without clinical evidence of lymph node metastases. TATI did not show any relationship with CEA, TPA, ferritin or SCC. The results of the present study suggest that TATI shows a satisfactory positivity rate in esophageal carcinoma, and TATI levels are related to local disease spread and prognosis.

Biomarkers, Tumor↗
PubMed1991

Death of cultured hippocampal pyramidal neurons induced by pathological activation of N-methyl-D-aspartate receptors is reduced by monosialogangliosides.

Glutamate-induced delayed neurotoxicity has been proposed to account for the selective loss of hippocampal pyramidal neurons after an ischemic period. We have studied the effects of exogenous glutamate and combined oxygen-glucose deprivation on the survival of hippocampal pyramidal neurons cultured from rat fetuses. Acute glutamate neurotoxicity (20 min, 23-25 degrees C) occurred in a concentration-dependent manner (LD50: 50 microM), destroying virtually all neurons 24 hr later. Such injury was prevented by N-methyl-D-aspartate (NMDA), but not non-NMDA, antagonists. Hippocampal cell death induced by removal of oxygen and glucose showed a similar pharmacological profile, indicating a role for NMDA receptor activation in neuronal loss associated with this energy crisis situation. Monosialogangliosides such as GM1 were effective in protecting against neurodegeneration induced by either direct glutamate exposure or oxygen and glucose deprivation. The selective action of gangliosides in disrupting the pathological consequences of glutamate receptor activation may provide a new therapeutic tool for excitatory amino acid-related brain injury processes.

Animals↗
PubMed1990

Gangliosides attenuate the delayed neurotoxicity of aspartic acid in vitro.

The neurotoxic effects of L-aspartate were evaluated in rat cerebellar granule cell cultures. Acute (15 min) exposure to L-aspartate produced a time-dependent, delayed degeneration of neuronal cell bodies and neurites (LD50 about 40 microM) over 24 h. Aspartate neurotoxicity was prevented by competitive and non-competitive N-methyl-D-aspartate (NMDA) antagonists, but not by non-NMDA antagonists, suggesting a major involvement of NMDA receptors in this neuronal injury. Gangliosides, including GM1, were also effective in attenuating the cytotoxicity of L-aspartate. The neurotoxic potential of L-aspartate may thus contribute to pathologies involving the action of endogenous excitatory amino acids.

Animals↗
PubMed1990

Is tissue polypeptide antigen still a useful tumor marker in breast carcinoma? Comparison with CA15.3 and MCA.

Serum levels of tissue polypeptide antigen (TPA) are related to the proliferative activity and to the mass of the malignancy, differently from any other available tumor marker. We therefore evaluated TPA in comparison with CA15.3 and MCA (mucinous-like carcinoma-associated antigen) in patients with primary breast cancer. TPA was measured in tumor cytosol and in serum. Cytosol and serum TPA levels were not significantly correlated. Serum TPA was higher in patients with locally more advanced disease and in receptor-negative cases. The relation between TPA and disease spread was not directly dependent on tumor bulk, whereas CA15.3 and MCA were highly correlated to the number of positive lymph nodes and tumor size. No correlations were found between TPA and CA15.3 or MCA, and the positivity concordance rate between TPA and CA15.3 or MCA was very low. Patients with higher TPA serum levels showed a worse prognosis in cases with and in those without axillary metastases. From our data we conclude that TPA provides information different from that obtained with breast-specific tumor markers and could therefore be useful in association with CA15.3 and/or MCA in the management of patients with breast cancer.

Adult↗
PubMed1990

Ten-year mortality from cardiovascular disease in relation to cholesterol level among men with and without preexisting cardiovascular disease.

To determine the associations of total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol with mortality from coronary heart disease and cardiovascular disease, we studied 2541 white men who were 40 to 69 years old at base line and followed them for an average of 10.1 years. Seventeen percent had some manifestation of cardiovascular disease at base line, whereas the others did not. Among the men who had cardiovascular disease at base line, we found, after multivariate adjustment, that those with "high" blood cholesterol levels (above 6.19 mmol per liter) had a risk of death from cardiovascular disease, including coronary heart disease, that was 3.45 times higher (95 percent confidence interval, 1.63 to 7.33) than that for men with "desirable" blood cholesterol levels (below 5.16 mmol per liter). The corresponding hazard ratios were 5.92 (95 percent confidence interval, 2.59 to 13.51) for LDL cholesterol levels above 4.13 mmol per liter as compared with those below 3.35 mmol per liter, and 6.02 (95 percent confidence interval, 2.73 to 13.28) for HDL cholesterol levels below 0.90 mmol per liter as compared with those above 1.16 mmol per liter. All three lipid levels were also significant predictors of death from coronary heart disease alone (P less than 0.005). Total cholesterol and LDL cholesterol levels were also significant predictors of death from cardiovascular and coronary heart disease in men without preexisting cardiovascular disease, although at a lower level of absolute risk of death. Thus, the 10-year risk of death from cardiovascular disease for a man with preexisting cardiovascular disease increased from 3.8 percent to almost 19.6 percent with increasing levels of total cholesterol from "desirable" to "high," whereas the corresponding risk for a man who was free of cardiovascular disease at base line increased from 1.7 percent to 4.9 percent. Our findings suggest that total, LDL, and HDL cholesterol levels predict subsequent mortality in men 40 to 69 years of age, especially those with preexisting cardiovascular disease.

Adult↗
PubMed1990

Seasonal independence of low prolactin concentration and high spontaneous eye blink rates in unipolar and bipolar II seasonal affective disorder.

Twenty-four subjects with seasonal affective disorder (SAD: bipolar II, n = 14; unipolar, n = 10) and 20 normal controls were assessed for early follicular basal serum prolactin (PRL) concentration in winter and summer. Luteal basal PRL concentration was assessed in winter. The PRL values represented the mean of three values derived during a 45-minute period. A subset of 17 subjects with SAD and 11 controls were also assessed for spontaneous eye blinking via a polygraphic recording in winter and summer. In winter, compared with controls, subjects with SAD were characterized by significantly lower follicular (10.1 vs 4.5 micrograms/L, respectively) and luteal (14.4 vs 7.4 micrograms/L, respectively) PRL values and by significantly higher eye blink rates (30 vs 61 blinks per 3 minutes, respectively). In summer, controls and subjects with SAD showed similar significant differences in follicular PRL values (9.3 vs 3.9 micrograms/L, respectively) and eye blink rates (25 vs 67 blinks per 3 minutes, respectively). No significant differences in PRL values or eye blink rates were found between the bipolar II and unipolar forms of SAD in either season. Results were discussed in terms of dopamine functioning.

Adult↗
PubMed1990

Excitatory amino acid neurotoxicity in cultured retinal neurons: involvement of N-methyl-D-aspartate (NMDA) and non-NMDA receptors and effect of ganglioside GM1.

Cultures of chicken day 8 embryo retinal cells, essentially free of contaminating non-neuronal elements, were used to examine the neurotoxicity of various excitatory amino acid transmitter receptor agonists. At 7 days in vitro, N-methyl-D-aspartate (NMDA), following 24 hr exposure to 0.1-1.0 mM, destroyed 60-70% of the multipolar neurons, but apparently spared photoreceptors. The cytotoxic effect of NMDA was prevented by extracellular Mg2+ or phencyclidine, suggesting a role for the NMDA ion channel; competitive NMDA antagonists were also neuroprotective. The mixed excitatory amino acid receptor agonist glutamate (0.1-1.0 mM) was also neurotoxic (approximately 70% loss of multipolar neurons) and strongly blocked by NMDA (but weakly by non-NMDA) antagonists and Mg2+, indicating a major action at NMDA receptors. As with NMDA, glutamate did not appear to affect photoreceptors. The neurotoxic action of kainate against multipolar retinal neurons, as reported by others, was confirmed here. Kainate neuronal injury was sensitive to the quinoxalinedione non-NMDA antagonists 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 6-cyanoquinoxaline-2,3-dione (CNQX), but not to Mg2+ or phencyclidine. Ibotenate and quisqualate, even at millimolar concentrations, were not neurotoxic. The monosialoganglioside GM1 was also effective in reducing NMDA and non-NMDA agonist neurotoxicity to retinal neurons. Maximal ganglioside benefit required 1-2 hr of pretreatment with 100-200 microM GM1. The percentage of multipolar neurons remaining after the neurotoxin insult approximately doubled with GM1 treatment. Gangliosides may thus have a therapeutic potential in excitatory amino acid-initiated neuropathologies.

Amino Acids↗
PubMed1990

Relationship of neuronal vulnerability and calcium binding protein immunoreactivity in ischemia.

The relationship between neuronal calcium binding protein content (calbindin D28K: CaBP and parvalbumin: PV) and vulnerability to ischemia was studied in different regions of the rat brain using the four vessel occlusion model of complete forebrain ischemia. The areas studied, i.e. the hippocampal formation, neocortex, neostriatum and reticular thalamic nucleus (RTN), show a characteristic pattern of CaBP and PV distribution, and are involved in ischemic damage to different degrees. In the hippocampal formation CaBP is present in dentate granule cells and in a subpopulation of the CA1 pyramidal cells, the latter being the most and the former the least vulnerable to ischemia. Non-pyramidal cells containing CaBP in these regions survive ischemia, whereas PV-containing non-pyramidal cells in the CA1 region are occasionally lost. Hilar somatostatin-containing cells and CA3 pyramidal cells contain neither PV nor CaBP. Nevertheless, the latter are resistant to ischemia and the former is the first population of cells that undergoes degeneration. Supragranular pyramidal neurons containing CaBP are the most vulnerable cell group in the sensory neocortex. In the RTN the degenerating neurons contain both PV and CaBP. In the neostriatum, ischemic damage involves both CaBP-positive and negative medium spiny neurons, although the degeneration always starts in the dorsolateral neostriatum containing relatively few CaBP-positive cells. The giant cholinergic interneurons of the striatum contain neither CaBP nor PV, and they are the most resistant cell type in this area. These examples suggest the lack of a consistent and systematic relationship between neuronal CaBP or PV content and ischemic vulnerability. It appears that some populations of cells containing CaBP or PV are more predisposed to ischemic cell death than neurons lacking these proteins. These neurons may express high levels of calcium binding proteins because their normal activity may involve a high rate of calcium uptake and/or intraneuronal release.

Animals↗
PubMed1990

Tissue polypeptide antigen in tumor cytosol: a new prognostic indicator in primary breast cancer.

The assessment of the risk of relapse is a critical need in the management strategy of breast cancer patients. To date, the most reliable prognostic factor is axillary nodal status. Several other pathological and biological parameters are currently under evaluation. Since 1982 we have been studying the prognostic role of several tumor markers in breast cancer cytosol. Elevated cytosol concentrations of tissue polypeptide antigen (TPA) have been found to have a highly significant direct correlation with both prolonged relapse-free interval (RFI) and higher survival rate. The information provided by cytosol TPA was independent of both axillary nodal status and steroid receptor content. In patients with a low risk of relapse (no axillary metastases, estrogen and progesterone receptor positive), cytosol TPA was still a significant prognostic indicator.

Adult↗
PubMed1990

Autosomal dominant rod-cone dysplasia in the Rdy cat. 1. Light and electron microscopic findings.

Detailed morphological analyses, including retinal layer thickness studies, were performed on heterozygous affected cats with autosomal dominant rod-cone dysplasia (gene symbol Rdy). Abnormalities were evident in retinas from the earliest age examined (2 weeks). Both rod and cone photoreceptors were affected equally by the dystrophy which was characterized by retarded and abnormal development of the visual cells. Photoreceptor inner segments remained rudimentary and outer segments did not elongate normally. Outer segment material was sparse and consisted mostly of whorls of disorganized and disoriented disc lamellae. Photoreceptor cell synaptic terminals showed delayed and incomplete synaptogenesis. Degenerative changes were first observed at 4.5 weeks of age and were characterized by the appearance of pyknotic nuclei in the outer nuclear layer and displacement of photoreceptor cells into the subretinal space. Degeneration began in central retinal regions and proceeded towards the periphery, resulting in progressive loss of the photoreceptor cell layers. By 30 weeks of age only two to five rows of nuclei remained in the outer nuclear layer. Area centralis degenerative lesions in advanced affected eyes were characterized by focal absence of the retinal pigment epithelium and choriocapillaris and thinning of the underlying tapetum. Retinal autoradiography showed that in normal kittens aged between 4.5 and 11 weeks of age rod outer segment renewal rates varied between 2.49 and 2.79 microns per 24 hr. The failure to form a labelled band in retinal autoradiograms from Rdy-affected kittens most probably indicates defective rod disc morphogenesis. It appears that the genetic defect in Rdy cats permits retarded development of the photoreceptor cells, but becomes lethal when these cells begin functional differentiation.

Animals↗
PubMed1990

Hippocampal cell death following ischemia: effects of brain temperature and anesthesia.

The effect of brain temperature and anesthesia on ischemic neuronal damage was studied in the hippocampal formation using the four vessel occlusion model in awake and anesthetized rats. Neuronal damage was assessed by immunocytochemistry and silver impregnation of tissue sections. The degree of ischemia was monitored by recording spontaneous and evoked electrical activity from the hippocampus and dentate gyrus in all animals. In addition, the hippocampal temperature and oxygen tension were also recorded using a chamber-type thin-film microelectrode in the anesthetized animals. Fifteen minutes ischemia in the awake animals caused greater neuronal damage and mortality of animals than 30 min ischemia in anesthetized rats. The temperature of the brain was found to drop by 4-6 degrees C during complete forebrain ischemia in the latter group. Neuronal damage was observed infrequently in the hippocampus of these animals. When the brain temperature was kept constant at the preischemic level during 30 min occlusion, all animals died within a day, while after 15 min occlusion the majority showed an almost complete degeneration of CA1 pyramidal cells and hilar somatostatin immunoreactive neurons. Following 15 min ischemia, the awake animals showed a similar cell loss in the CA1 region and the hilus. It is concluded that, in the anesthetized animals prepared for acute recording, the decreased temperature of the brain during ischemia is a major factor in protecting neurons from damage, but that Equithesin anesthesia also has a significant protective effect. Consistent ischemic degeneration occurs in awake animals by four vessel occlusion, if the brain temperature is controlled and the completeness of ischemia is monitored by recording spontaneous and evoked electrical activity with chronic electrodes.

Anesthetics↗
PubMed1990

Hypoglycemic neurotoxicity in vitro: involvement of excitatory amino acid receptors and attenuation by monosialoganglioside GM1.

Rat cerebellar granule cells, when subjected to a glucose-free environment for 4 h, developed extensive degeneration of neuronal cell bodies and their associated neurite network over the following 24 h. This neuronal damage was quantitated with a colorimetric assay using the metabolic dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. Hypoglycemic neuronal injury could be markedly reduced by the presence of both competitive (3-(+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid) and non-competitive (phencyclidine) N-methyl-D-aspartate receptor antagonists, but not by kainate/quisqualate preferring antagonists 6-cyano-7-nitroquinoxaline-2,3-dione and 6,7-dinitroquinoxaline-2,3-dione. Glucose deprivation neuronal injury was also reduced by adding glutamate-degrading enzymes to the incubation medium. Monosialoganglioside GM1, but not its asialo derivative (lacking sialic acid), was also effective in protecting against hypoglycemic neurodegeneration when included during the period of glucose deprivation. These results suggest that the neuronal injury to cerebellar granule cells resulting from glucose deprivation is mediated predominantly by activation of the N-methyl-D-aspartate type of excitatory amino acid receptor, perhaps through the action of endogenously released glutamate. Furthermore, the monosialoganglioside GM1, a member of a class of naturally occurring sialoglycosphingolipids, is able to attenuate this neuronal injury--as already observed for glutamate neurotoxicity and anoxic neuronal death in cerebellar granule cells. Gangliosides may thus prove to be of therapeutic utility in excitatory amino acid-associated neuropathologies.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1990

Excitatory amino acid receptor agonists stimulate membrane inositol phospholipid hydrolysis and increase cytoplasmic free Ca2+ in primary cultures of retinal neurons.

A variety of neurotransmitters are believed to elicit effects through receptor-stimulated inositol phospholipid metabolism. It appears that most major types of retinal neurons receive a direct glutamatergic input. The aim of the present studies was to characterize excitatory amino acid (EAA) receptor-mediated breakdown of inositol phospholipids and changes in Ca2+ homeostasis in primary avian retinal cell cultures. Cell monolayers, prepared from 8-day-old chick embryo neural retina, were labelled with [3H]inositol for 48 h, and used after 7 days in vitro. Kainic acid stimulated the accumulation of inositol phosphates in a time- and dose-dependent manner (ED50 = 30 microM). The EAA receptor agonists glutamate, N-methyl-D-aspartate (NMDA), ibotenate and quisqualate were all active, with the rank order: glutamate greater than kainate greater than NMDA much greater than ibotenate approximately quisqualate. External Ca2+ was required for these effects. Agonist actions were inhibited by type-specific antagonists, and also Mg2+ in the case of glutamate and NMDA. Glutamate, NMDA and kainate also elevated cytosolic free Ca2+ in individual retinal cells loaded with the Ca2(+)-sensitive dye Fura-2, as assessed by digital fluorescence ratio imaging microscopy. The agonist-induced increases in [Ca2+]i were largely dependent on extracellular Ca2+, independent of membrane depolarization and were blocked by Mg2+ for glutamate and NMDA. These results demonstrate that vertebrate retinal cells possess EAA receptors coupled to intracellular signal transduction pathways.

Amino Acids↗
PubMed1990

Protective effects of a monosialoganglioside derivative following transitory forebrain ischemia in rats.

We evaluated the effects of treatment with the inner ester derivative of the monosialoganglioside GM1 on cortical electroencephalographic activity and hippocampal CA1 morphology after transitory, near-complete cerebral ischemia in rats. Ischemia was induced by the four-vessel occlusion method, and we studied only the 58 rats that showed flattening of the cortical electroencephalogram for the entire 30 minutes of occlusion. The ganglioside (n = 30) or saline (n = 28) was administered intravenously immediately after release of the carotid clips and then intramuscularly for 21 days of observation. Cortical electroencephalographic activity was monitored throughout the experiment. After 21 days of recirculation we assessed hippocampal CA1 damage by light microscopy. The results indicate that treatment with the ganglioside reduces postischemic secondary damage to the cortical circuitry (as indicated by significantly higher cortical electroencephalographic activity late after reperfusion) and limits neuronal loss in the CA1 region. Our results lend support to the possible therapeutic use of ganglioside in human pathologic conditions associated with cerebrovascular insufficiencies.

Animals↗