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Biomedical subjects

S Govoni

Publications and source records attributed to S Govoni.

At least 73 records · Page 4Linked to original sources
PubMed1996

Peripheral cells as an investigational tool for Alzheimer's disease.

A number of abnormalities in metabolic and biochemical processes have been found in cultured skin fibroblasts derived from patients affected by Alzheimer's disease (AD). An example of the successful use of peripheral cells to examine a cell biological abnormality in AD are the studies on transduction systems and on APP metabolism, mostly performed on fibroblasts from AD donors. In fact, some of the described alterations mirror events that have also been demonstrated to occur in the AD brain. Within this context data obtained using peripheral cells may help to identify and to test hypotheses on the primary pathophysiological mechanisms leading to AD. In perspective, the identification of peripheral biological markers could provide a useful aid in AD and could allow identification of stages of of the disease or subgrouping of patients, possibly helping to predict the response to treatment.

Alzheimer Disease↗
PubMed1996

Non-virally mediated gene transfer into human central nervous system precursor cells.

Lipofectamine-based transfection was used as a method of choice to deliver the bacterial beta-galactosidase gene into human central nervous system (CNS) precursor cells. We achieved a transfection efficiency of 7.4%. beta-Galactosidase expressing cells were shown to display both neuronal and glial phenotypes. We also delivered the temperature sensitive allele of SV40 Large-T antigen and obtained a high level of expression of the immortalizing oncoprotein in the cells. Colonies of Large-T antigen immunoreactive cells were indeed visible 10 days after transfection.

Cation Exchange Resins↗
PubMed1996

Functional impairment in protein kinase C by RACK1 (receptor for activated C kinase 1) deficiency in aged rat brain cortex.

Several laboratories have reported a lack of protein kinase C (PKC) activation in response to various stimuli in the brain of aged rats. It has been suggested that changes in lipid membrane composition could be related to this functional deficit. However, recent evidence has indicated that the translocation of PKC to the different subcellular compartments is controlled by protein-protein interactions. Recently, a class of proteins, termed receptors for activated C kinase (RACKs), have been described that bind PKC. The present study was conducted to determine whether alterations in RACK1, the best-characterized member of RACKs, were associated with changes in translocation and expression of PKC. Quantitative immunoblotting revealed that RACK1 content was decreased by approximately 50% in aged rat brain cortex, compared with that in adult and middle-aged animals. The levels of calcium-independent PKC delta and epsilon, interacting with RACK1, and related calcium-independent PKC activity were not modified by the aging process. By comparison, phorbol ester-stimulated translocation of this activity and of PKC delta and epsilon immunoreactivity was absent in cortex from aged animals, as well as the translocation of the calcium-dependent PKC beta, also known to interact with RACK1. These results indicate that a deficit in RACK1 may contribute to the functional impairment in PKC activation observed in aged rat brain.

Aging↗
PubMed1996

Fibroblasts of patients affected by Down's syndrome oversecrete amyloid precursor protein and are hyporesponsive to protein kinase C stimulation.

The present study investigates the ability of the pharmacologic activation of protein kinase C (PKC) to modulate amyloid precursor protein (APP) secretion in human skin fibroblasts from patients affected by Down's syndrome (DS). We assessed DS subjects at the Hospital Institute of Sospiro, Cremona, and at the Alzheimer's Disease Unit of the Sacred Heart Hospital in Brescia, and we subdivided them into nondemented (NDS) and demented (DDS) patients. All DS patients were trisomy 21 karyotype. DS fibroblasts had an increased content of APP immunoreactive material as revealed by immunocytochemistry analysis. The basal secretion of soluble APP was higher (+94.6%) in Down's cells with respect to controls. The observation on the fibroblasts prepared from DS is consistent with these patients' possessing an extra copy of the APP gene (mapped on chromosome 21) leading to increased APP expression. Phorbol-12,13-dibutyrate (PdBu, 9 to 150 nM) treatment promoted a dose-dependent increase of secreted APP in the conditioned medium of control fibroblasts. The peak response (+102.2%) was attained using 150 nM PdBu. In Down's fibroblasts, PdBu stimulated APP secretion already maximally at low concentrations (9 nM), but the peak response, due to the higher basal release, was lower on a percentage basis (+16.4%) than in control fibroblasts. The results indicate that in Down's fibroblasts the mechanisms controlling APP release are at least quantitatively altered. In addition, these results suggest caution when using information obtained from Down's patients to model Alzheimer's disease biochemical defects.

Adult↗
PubMed1995

Defective phorbol ester-stimulated secretion of beta-amyloid precursor protein from Alzheimer's disease fibroblasts.

The present study shows that cultured fibroblasts from sporadic Alzheimer's disease patients are deficient in protein kinase C-regulated secretion of amyloid precursor protein. In particular, Alzheimer fibroblasts show a reduced basal secretion and a reduced response at low concentrations of phorbol-12,13-dibutyrate, with an EC50 twofold higher than control fibroblasts. Furthermore, we observed that such defective regulation of the amyloid precursor secretion can possibly be correlated to a specific defect in protein kinase C alpha in fibroblasts from Alzheimer patients.

Aged↗
PubMed1995

High affinity and selectivity on 5-HT1A receptor of 1-aryl-4-[1-tetralin)alkyl]piperazines. 2.

Several 4-alkyl-1-arylpiperazines that present a tetralin moiety on the terminal part of the side chain were synthesized in order to increase the selectivity on the 5-HT1A versus D-2, alpha 1, sigma, and other 5-HT receptors. Many changes have been effected on previous structures of type 3(1-aryl-4-[3-(1,2-dihydronaphthalen-4-yl)-n-propyl]piperazines). Several synthetic procedures were followed to obtain the final products, depending on the presence or absence of a double bond, as well as of a heteroatom on the side chain. In the first case versatile use of Grignard reaction was made, whereas in the second one usual synthetic ways were applied. Final compounds were evaluated for in vitro activity on dopamine D-1 and D-2, serotonin 5-HT1A, 5-HT1B, 5-HT1C, and 5-HT2, alpha 1 adrenergic, and sigma receptors by radioreceptor binding assay. For the 2-MeO-Ph, 2-pyridyl, and unsubstituted phenyl N-piperazine derivatives, low IC50 values (0.3 nM) on 5-HT1A receptors and high selectivity values were observed.

Animals↗
PubMed1995

Gene dose of the epsilon 4 allele of apolipoprotein E and disease progression in sporadic late-onset Alzheimer's disease.

A strong association has been described in cross-sectional studies between the epsilon 4 allele of the apolipoprotein E and late-onset Alzheimer's disease (LOAD). This study addresses the relationship between disease progression and the epsilon 4 allele in 62 sporadic LOAD (onset at age 70 and over) patients. Disease progression was estimated retrospectively with the Mini-Mental State Examination (MMSE) amounting to 4.7, 3.8, and 2.2 points per year (sex-adjusted test for trend: p = 0.01) and with the Clinical Dementia Rating (CDR) to 0.76, 0.67, and 0.42 units per year (p = 0.03) in -/-, epsilon 4/-, and epsilon 4/epsilon 4 patients. The proportion of patients with fast progression decreased (p < or = 0.005) and with slow progression increased (p = 0.002) with increasing epsilon 4 gene dose. These findings were confirmed in a smaller sample of 28 patients for whom longitudinal assessments of MMSE were available and when nonlinear progression of the disease was accounted for in a stratified analysis. These data suggest that disease duration might be longer in epsilon 4 carriers and that this might at least partly account for the cross-sectional association between the epsilon 4 allele and LOAD.

Age of Onset↗
PubMed1994

Protein kinase C activation and anti-amnesic effect of acetyl-L-carnitine: in vitro and in vivo studies.

Drugs belonging to different chemical classes having the ability to improve behavioral performance in animal learning and memory tests may share the common ability to stimulate protein kinase C activity in rat brain cortex. In vitro acetyl-L-carnitine (100 nM) promoted in rat brain cortex slices a significant increase in particulate activity associated with lower soluble protein kinase C activity and produced a direct stimulation of the enzyme in both the cortex and hippocampus. In vivo a significant increase in particulate protein kinase C activity was observed in the group of rats treated with 60 mg/kg acetyl-L-carnitine, a dose shown to be effective in improving the cognitive deficits induced by scopolamine in the Morris maze test. The results suggest that acetyl-L-carnitine increases particulate protein kinase C activity in the cortex both in vitro and in vivo. This effect in the in vivo experiments seems to be observed only with doses that are effective in improving the performance of rats in a spatial learning task.

Acetylcarnitine↗
PubMed1994

Expression and regulation of calcium-independent protein kinase C in NG 108-15 cell differentiation.

Protein, mRNA and activity levels of the calcium-independent protein kinase C (nPKC) isoenzymes were examined in NG108-15 cells. Western blot analyses reveal that proliferating NG 108-15 cells express the delta, epsilon, and eta, but not the theta species. The atypical species PKC zeta was also detected. Differentiation of these cells with dibutyryl cAMP was associated with increase in the levels of PKC epsilon, with no significant changes in its steady-state mRNA levels. The levels of the other isoforms were not altered by the differentiated state. Similarly, no changes in nPKC activity were discerned in either the soluble or particulate fractions when histone or other proteins were used as substrates. These data suggest that the PKC epsilon isoform may be important for the production and maintenance of the differentiated state in NG 108-15 cells.

Animals↗
PubMed1994

Regulation of protein kinase C in NG108-15 cell differentiation.

The involvement of PKC in NG108-15 cell differentiation was investigated. Differentiation with dBcAMP was associated with a decrease in total cellular phorbol ester binding. The histone-directed PKC activity was decreased in the soluble fraction. Northern and Western blotting revealed the presence of only PKC alpha but not PKC beta and PKC gamma among the calcium-dependent isoforms. Differentiation induced a decrease of cytosolic PKC alpha immunoreactivity, with no changes of mRNA content or appearance of PKC beta and PKC gamma isoforms. The low levels of PKC alpha in the soluble fraction suggest that the mRNA for this species is less efficiently translated in differentiated NG108-15 cells. The data suggest that down-regulation of PKC alpha protein and kinase activity are associated with induction of neuronal morphology in NG108-15 cells.

Animals↗
PubMed1994

PKC activity in rat C6 glioma cells: changes associated with cell cycle and simvastatin treatment.

The parallel effects of simvastatin on cell cycle and PKC activity in rat C6 glioma cells were investigated. Simvastatin, 2.5 microM, for 24 h resulted in cell growth arrest in early G1 phase of the cell cycle and in a significant increase of total PKC activity (283 +/- 42 vs 470 +/- 61 pmoles/min/mg protein p = 0.002 for control cells and simvastatin-treated cells, respectively). The effect of simvastatin was fully prevented by mevalonate. A time dependent increase of PKC activity was observed in control exponentially free-growing C6 cells approaching confluency: a highly significant negative correlation (r = -0.91 p < 0.0001) between PKC activity and growth rate was calculated. PKC activity was high in cells arrested in G0 by serum starvation (0.4%). Following addition of complete medium (17.5% serum) the PKC activity progressively decreased and reached a minimum when cells traversed the G2/M phase, as determined by DNA analysis distribution. PKC activity dropped 30% in simvastatin-arrested early G1 cells; 44% in hydroxyurea-arrested cells at the G1/S boundary; and 73% in Colcemid mitosis-blocked cells. The results show that C6 glioma cell PKC activity is maximal in a G0 quiescent state and varies at different points of the cell cycle.

Animals↗