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M Guizzetti

Publications and source records attributed to M Guizzetti.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effect of ethanol on muscarinic receptor-induced calcium responses in astroglia.

The effects of ethanol on muscarinic receptor-mediated calcium responses were investigated in individual primary rat astrocytes and human 132 1N1 astrocytoma cells using indo-1/AM and image cytometry. After a 30-min incubation, carbachol-induced calcium responses were inhibited only at 100 or 250 mM ethanol. The effects of ethanol were more pronounced and occurred at lower concentrations with longer exposures, with significant inhibition seen at 10 mM following a 24-hr incubation. Thapsigargin- and glutamate-induced responses were unaffected by ethanol, indicating some selectivity in this inhibition. Upon removal of ethanol, inhibition of calcium responses persisted for up to 6-12 hr, with carbachol responses returning to control levels by 24 hr after washout. Ethanol exposure did not affect muscarinic-receptor binding in astrocytoma cells, but inhibited carbachol-induced IP(3) formation. Inhibition of (3)H-thymidine incorporation by ethanol also persisted upon removal of the alcohol, with a time-dependency similar to that of the calcium responses. These results indicate that ethanol inhibits muscarinic receptor-induced calcium responses in astroglia in a concentration- and duration-dependent manner. They also show that co-incubation with ethanol is not necessary for this effect, suggesting that long-term exposure to ethanol may modify, in a reversible manner, the coupling of muscarinic receptors with its effector. This effect of ethanol may play a role in ethanol's inhibition of carbachol-induced thymidine incorporation.

Animals↗
PubMed2000

Exposure to 60-Hz magnetic fields and proliferation of human astrocytoma cells in vitro.

Epidemiological studies have suggested that exposure to electric and magnetic fields (EMF) may be associated with an increased incidence of brain tumors, most notably astrocytomas. However, potential cellular or molecular mechanisms involved in these effects of EMF are not known. In this study we investigated whether exposure to 60-Hz sinusoidal magnetic fields (0.3-1.2 G for 3-72 h) would cause proliferation of human astrocytoma cells. Sixty-Hertz magnetic fields (MF) caused a time- and dose-dependent increase in proliferation of astrocytoma cells, measured by (3)H-thymidine incorporation and by flow cytometry, and strongly potentiated the effect of two agonists (the muscarinic agonist carbachol and the phorbol ester PMA). However, MF had no effect on DNA synthesis of rat cortical astrocytes, i.e., of similar, nontransformed cells. To determine the amount of heating induced by MF, temperatures were also recorded in the medium. Both 1.2 G MF and a sham exposure caused a 0.7 degrees C temperature increase in the medium; however, (3)H-thymidine incorporation induced by sham exposure was significantly less than that caused by MF. GF 109203X, a rather specific protein kinase C (PKC) inhibitor, and down-regulation of PKC inhibited the effect of MF on basal and on agonist-stimulated (3)H-thymidine incorporation. These data indicate that MF can increase the proliferation of human astrocytoma cells and strongly potentiate the effects of two agonists. These findings may provide a biological basis for the observed epidemiological associations between MF exposure and brain tumors.

Animals↗
PubMed2000

Effect of phenylalanine and its metabolites on the proliferation and viability of neuronal and astroglial cells: possible relevance in maternal phenylketonuria.

Phenylketonuria is a genetic defect that, without strict dietary control, results in the accumulation of phenylalanine (Phe) in body fluids. If a low-Phe diet is not maintained during pregnancy, the offspring of phenylketonuric women are born with mental retardation and microcephaly. Primary cultures of rat cerebellar granule cells, rat cortical astrocytes, human fetal astrocytes, and human neuroblastoma (SY5Y) cells and human astrocytoma (1321N1) cells were used to test the hypothesis that the microencephaly may be a result of neuronal cell death and reduced astrocyte proliferation. Exposure to Phe or to six Phe metabolites [phenylacetic acid (PAA), phenyllactic acid, hydroxyphenylacetic acid, phenylpyruvic acid, phenylethylamine (PEA), and mandelic acid] did not result in astroglial or neuronal cell cytotoxicity. Treatment of 1321N1 cells, human fetal astrocytes, or rat astrocytes with 5 mM Phe for 24 h decreased DNA synthesis 19 +/- 4, 30 +/- 4, and 60 +/- 6%, respectively. This effect was concentration dependent, and flow cytometry revealed that Phe treatment resulted in the accumulation of cells in the G(0)/G(1) phase of the cell cycle. In addition, in 1321N1 cells, exposure to 5 mM PAA, and in rat astrocytes, exposure to 0.5 mM PEA inhibited cell proliferation 42 +/- 4 and 55 +/- 4%, respectively. These metabolites also resulted in the accumulation of cells in the G(0)/G(1) phase of the cell cycle. In human fetal astrocytes, 0.5 mM PEA and 0.5 mM PAA resulted in a 41 +/- 12 and 52 +/- 11% reduction proliferation, respectively.

Astrocytes↗
PubMed2000

Muscarinic receptors, protein kinase C isozymes and proliferation of astroglial cells: effects of ethanol.

Activation of cholinergic muscarinic receptors (primarily the M3 subtype) causes proliferation of astroglial cells and this effect is inhibited by low concentrations (10-50 mM) of ethanol. Investigations on the signal transduction pathways activated by muscarinic receptors in a human astrocytoma cell line (1321N1) have focused on protein kinases C (PKC). Among PKC isozymes expressed in this cell line (alpha, epsilon, zeta), the atypical PKCzeta appears to play a primary role in the mitogenic action of muscarinic agonists. We investigated whether activation of these PKC isozymes may be affected by ethanol at concentrations that can inhibit muscarinic receptor-induced proliferation. Carbachol caused an increase in phorbol ester binding and translocation of PKCepsilon, however, these were inhibited only by 100-200 mM ethanol. On the other hand, translocation of the atypical PKCzeta to the perinuclear area by carbachol was inhibited by ethanol in a dose-dependent manner (10-100 mM). These results suggest that activation of PKCzeta may represent a relevant target for the inhibitory effect of ethanol on muscarinic receptor-induced glial cell proliferation.

Astrocytes↗
PubMed1999

Muscarinic cholinergic receptor signal transduction as a potential target for the developmental neurotoxicity of ethanol.

Central nervous system dysfunctions (most notably mental retardation and microcephaly) are among the most significant effects of in utero exposure to ethanol. Ethanol has been shown to cause alterations of both neuronal and glial cells, including cell loss, and changes in their migration and maturation. Here, we propose that one of the potential targets for the developmental neurotoxicity of ethanol may be represented by the signal transduction systems activated by cholinergic muscarinic receptors. Ethanol has been shown to inhibit second messenger systems activated by various G-protein-coupled receptors, including certain subtypes of muscarinic receptors. Although the roles of muscarinic receptors in brain development have not been fully elucidated, two potentially relevant effects have been discovered in the past few years. By activating muscarinic receptors coupled to phospholipid metabolism, acetylcholine can induce proliferation of glial cells, and act as a trophic factor in developing neurons by preventing apoptotic cell death. Ethanol has been shown to inhibit both actions of acetylcholine in vitro. These effects of ethanol may lead to a decreased number of glial cells and to a loss of neurons, which have been observed following in vivo alcohol exposure. In turn, these may be the basis of microencephaly and cognitive disturbances in children diagnosed with Fetal Alcohol Syndrome.

Animals↗
PubMed1999

Effects of ethanol on calcium homeostasis in the nervous system: implications for astrocytes.

Ethanol is a major health concern, with neurotoxicity occurring after both in utero exposure and adult alcohol abuse. Despite a large amount of research, the mechanism(s) underlying the neurotoxicity of ethanol remain unknown. One of the cellular aspects that has been investigated in relationship to the neuroteratogenicity and neurotoxicity of ethanol is the maintenance of calcium homeostasis. Studies in neuronal cells and other cells have shown that ethanol can alter intracellular calcium levels and affect voltage and receptor-operated calcium channels, as well as G protein-mediated calcium responses. Despite increasing evidence of the important roles of glial cells in the nervous systems, few studies exist on the potential effects of ethanol on calcium homeostasis in these cells. This brief review discusses a number of reported effects of alcohol on calcium responses that may be relevant to astrocytes' functions.

Astrocytes↗
PubMed1998

The role of protein kinase C alpha and epsilon isozymes in DNA synthesis induced by muscarinic receptors in a glial cell line.

Acetylcholine has been shown to induce proliferation of human astrocytoma cells by activating muscarinic receptors, particularly the m3 subtype. In the present study the role of protein kinase C in DNA synthesis induced by carbachol has been investigated. Carbachol-induced [methyl-3H]thymidine incorporation was inhibited by the protein kinase C inhibitors GF 109203X and staurosporine. However, carbachol-induced DNA synthesis was only partially reduced by protein kinase C down-regulation by phorbol 12-myristate 13-acetate (PMA), and maximal concentrations of carbachol and PMA had an additive effect on [methyl-3H]thymidine incorporation. Exposure for 24 h to maximally effective concentrations of carbachol did not induce down-regulation of protein kinase C alpha, and caused a small but significant down-regulation of protein kinase C epsilon; cells exposed for 24 h to carbachol were still able to respond with protein kinase C translocation to PMA stimulation. Carbachol caused a significant increase of phorbol ester binding, but did not stimulate protein kinase C alpha translocation, while it caused a short-lasting translocation of protein kinase C epsilon; however, protein kinase C epsilon translocation was not correlated with the time-course of carbachol-induced increase in [methyl-3H]thymidine incorporation. On the other hand, the time-course of translocation/down-regulation of protein kinase C alpha and protein kinase C epsilon induced by PMA was in good correlation with the time-course of PMA-induced [methyl-3H]thymidine incorporation. These results suggest that protein kinase C alpha may not be involved in DNA synthesis induced by muscarinic receptors stimulation in 132-1N1 astrocytoma cells, while protein kinase C epsilon appears to play a role in the initial exit from G0/G1 phase, though it cannot be considered the major determinant for sustained proliferation.

Astrocytoma↗
PubMed1998

Internal mammary blood supply for ileo-colon interposition in esophagogastroplasty: a case report.

We report on a clinical case where microsurgical techniques successfully supported traditional surgery in a wide reconstruction between the oropharynx and small bowel. Several years ago, the patient sustained a severe corrosive injury of the upper digestive tract with subsequent esophageal stricture and stiffening; at that time, an emergency gastrectomy was performed. In this case, the restoration of the defect could not rely on the classic colonic interposition. During the operation the ileo-colic flap, well-fitted for tension-free reconstruction, revealed the foreseen inadequacy of its vascularization based on the sole middle colic vascular pedicle. The blood supply to its proximal part was then increased by microanastomosis between the right internal mammary and ileo-colic vessels. The revascularization ensured the viability of the interposed tissue. Oral intake resumed after 3 weeks; nowadays the patient is able to maintain her ideal weight with adequate nutrition.

Adult↗
PubMed1997

The effects of ethanol on glial cell proliferation: relevance to the fetal alcohol syndrome.

Exposure to ethanol during pregnancy is detrimental to brain development. Individuals affected by the Fetal Alcohol Syndrome present a number of central nervous system dysfunctions including microencephaly and mental retardation. Studies on the mechanisms of ethanol's developmental neurotoxicity have focused on its interaction with neurons; however, emerging evidence is suggesting that ethanol can significantly affect glial cells as well. A number of in vitro studies have shown that ethanol can inhibit the proliferation of various glial cells (mostly primary astrocytes or astrocytoma cells) at relatively high concentrations (100-200 mM). On the other hand, proliferation induced by some, but not all mitogens, is inhibited by low concentrations (10-50 mM) of ethanol. These inhibitory effects of ethanol may contribute to its developmental neurotoxicity observed following in vivo exposure. Animal models have indeed shown that ethanol causes microencephaly when given during the brain growth spurt, a period of brain development characterized by astroglial proliferation and maturation.

Animals↗
PubMed1997

Thyroid peroxidase as toxicity target for dithiocarbamates.

In vivo ethylenebisdithiocarbamates and ETU are toxic to the thyroid gland. Since the molecular target of these compounds is thought to be thyroid peroxidase (TPO) which catalyzes the transfer of iodine to thyroglobulin, we examined the effect of these compounds on peroxidative activity in Chinese hamster ovary (CHO) cells transfected with the human TPO gene. The activity was inhibited by 50 microM ETU, 5 microM ziram and 5 microM zineb, the last-mentioned effect being irreversible in the absence of iodide. Thiram had no effect. By contrast, the iodinating activity of TPO was blocked only by 5 microM ETU and 50 microM zineb but not by the other compounds. The effect on TPO-catalysed iodination could explain the differences in thyrotoxicity of these compounds in vivo.

Animals↗
PubMed1996

Acetylcholine as a mitogen: muscarinic receptor-mediated proliferation of rat astrocytes and human astrocytoma cells.

The mitogenic effect of muscarinic receptor agonists in glial cells has been characterized in rat cortical astrocytes and human 132 1N1 astrocytoma cells. The muscarinic receptor agonist carbachol caused a dose- and time-dependent increase in proliferation, as measured by [3H]thymidine incorporation. The mitogenic effect was mimicked by several muscarinic, but not nicotinic receptor agonists, and was blocked by muscarinic receptor antagonists. Reverse transcription-polymerase chain reaction (RT-PCR) experiments indicated the presence of m2, m3 and to a lesser degree, m5 muscarinic receptor mRNA in both astrocytes and astrocytoma cells. Proliferation experiments with subtype-specific muscarinic receptor antagonists suggest that carbachol-induced proliferation is due to activation of muscarinic M3 receptors. The phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) also stimulated glial cell proliferation. Down-regulation of protein kinase C, or the protein kinase C antagonist 1,5-(isoquinolynsulfanyl)-2-methylpiperazine dihydrochloride (H7) blocked proliferation induced by either TPA or carbachol. Of other neurotransmitters tested, histamine caused glial cell proliferation, norepinephrine and gamma-aminobutyric acid were ineffective, while serotonin and glutamate inhibited basal or serum-stimulated proliferation.

Acetylcholine↗
PubMed1996

Inhibition of muscarinic receptor-stimulated glial cell proliferation by ethanol.

Acetylcholine and other muscarinic agonists stimulate the proliferation of rat cortical astrocytes and 132 1N1 human astrocytoma cells by activating muscarinic m3 cholinergic receptors. Ethanol was a potent inhibitor of carbachol-stimulated proliferation, measured by [3H]thymidine incorporation, with an IC50 of 10 mM. On the other hand, basal and serum-stimulated proliferation of astrocytes and astrocytoma cells was inhibited by ethanol with lower potency (IC50 = 200-250 mM). Concentration-response experiments with carbachol, in the presence of 10 mM ethanol, suggested that inhibition of proliferation by the alcohol was of the noncompetitive type. Experiments with acetaldehyde and with the alcohol dehydrogenase inhibitor 4-methylpyrazole suggested that the inhibitory effect of alcohol was due to ethanol itself and not to its metabolite acetaldehyde. Proliferation of astrocytoma cells induced by carbachol and the inhibitory effects of ethanol were also confirmed by flow cytometry using the 5-bromodeoxyuridine-Hoechst 33258 method. Ethanol (10 mM) had no effect on proliferation induced by 50 micrograms/ml insulin and 100 ng/ml platelet-derived growth factor BB; on the other hand, the mitogenic effect of 1 mM histamine, 100 U/ml interleukin-1, and 100 ng/ml 12-O-tetradecanoylphorbol 13-acetate were inhibited by approximately 50%. These results indicate that proliferation of glial cells induced by muscarinic agonists is especially sensitive to the inhibitory effect of ethanol. This action of ethanol may be relevant to its developmental neurotoxicity, particularly microencephaly, which is one of the common features of the fetal alcohol syndrome.

Acetaldehyde↗
PubMed1995

Cloning of a new FRTL5-derived cell line stably expressing active human thyroid peroxidase.

A full-length cDNA clone for human thyroid peroxidase inserted into the mammalian cell expression vector pECE was stably transfected into the rat thyroid cell line FRTL5. Clones expressed immunologically and enzymatically assessed human thyroid peroxidase protein. Methimazole (25 microM) inhibited the thyroid peroxidase activity dose-dependently and this effect was completely antagonised by 100 microM NaI. Ethylenethiourea, metabolite of dithiocarbamate pesticides, inhibited the enzyme at 50 microM. Thus, we have obtained thyroidal cells stably expressing enzymatically active human thyroid peroxidase which can be pharmacologically modulated and studied.

Animals↗
PubMed1995

Effect of 25-hydroxycholesterol, 26-hydroxycholesterol and its analogue, 26-aminocholesterol, on protein content, protein synthesis and LDH leakage in mouse epidermal cells.

The cytotoxicity of 25-hydroxycholesterol, 26-hydroxycholesterol and its analogue, 26-aminocholesterol was investigated in murine epidermal cell line, HEL-30. Lactate dehydrogenase (LDH) leakage, protein synthesis and protein content were determined after exposure of cell monolayers to the compounds ranging from 0.1-200 microM for 2, 6, or 24 h. 26-Aminocholesterol affected all the parameters studied time and concentration dependently; 25-hydroxycholesterol and 26-hydroxycholesterol were not toxic for HEL-30 cells. The cellular target for 26-aminocholesterol was primarily the membrane, since the LDH leakage was already detectable 10 min after exposure. On the other hand, for the other two oxysterols a protective role on this structure might be postulated. In fact 25-hydroxycholesterol and 26-hydroxycholesterol decreased the natural LDH leakage due to the ageing of the culture. In addition, 20 microM 25-hydroxycholesterol reversed the effect of moderately lytic doses of 26-aminocholesterol and Triton X-100, but not of sodium dodecyl sulfate.

Analysis of Variance↗
PubMedDate not supplied

Mixtures of benomyl, pirimiphos-methyl, dimethoate, diazinon and azinphos-methyl affect protein synthesis in HL-60 cells differently.

Dimethoate, azinphos-methyl, diazinon and pirimiphos-methyl, widely used organophosphorous insecticides, and benomyl, a benzimidazole fungicide, induce different cytotoxic effects on the human leukemia cell line HL-60. Among the insecticides tested, only azinphos and diazinon induced a dose-related inhibition of protein synthesis in HL-60 cells at 24 h, at 60 and 40 micrograms/ml medium, respectively. Dimethoate and pirimiphos were not active up to 100 micrograms/ml. Benomyl strongly inhibited protein synthesis at 50 micrograms/ml and the polymerisation of actin to give cytoskeletal microfilaments (F-actin) at 30 micrograms/ml. Mixtures of benomyl-pirimiphos and dimethoate azinphos-diazinon were also investigated. Pirimiphos, when present in equal concentration, antagonized the inhibitory effect of benomyl on protein synthesis at 4 h, but not at 24 h. The effect of the other insecticide mixture on the same parameter was greater than that of the two active components, diazinon and azinphos given singly.

Actins↗