Guanylate cyclase in human brain tumors: regulation of cellular growth.
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Biomedical subjects
Publications and source records attributed to L Frattola.
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Lymphocytes from 13 myasthenic patients were incubated in vitro with membranes enriched in nicotinic cholinergic receptor obtained from Torpedo marmorata electric organ. When autologous serum was present in the incubation medium, the lymphocytes were highly stimulated. In contrast, no stimulation occurred when lymphocytes were cultured in presence of AB serum. These results suggest that an immune response against the Ach cholinergic receptor is present in myasthenic patients and give further support to the hypothesis that an autoimmune response against muscular receptors may be involved in Myasthenia Gravis pathogenesis.
The authors tested the effects of 2-Br-ergocriptine (bromocriptine, CB-154), a drug which exerts a mixed agonist-antagonist activity on the dopaminergic receptors, in 12 patients with Huntington Chorea in a double-blind crossover trial. This treatment significantly reduced the abnormal involuntary movements and the disease severity in most of the patients. Subjects who were slightly disabled showed a better response than the ones with more severe degrees of disability.
Histochemical, biochemical and electromyographic studies were performed in a case of carnitine deficiency in serum and in muscle. Clinical features include proximal muscle weakness, predominant type I fiber impairment, excess of triglycerides and moderate glycogen accumulation in muscle. No abnormalities of palmityl CoA synthetase, carnitine palmityl transferase, carnitine acetyl transferase and lipase were evidenced. An interesting EMG decremental pattern was recorded. Correlations between electromyographic and biochemical findings are considered. A clinical improvement, a normal plasma carnitine level and a normal response at EMG repetitive stimulation were found after carnitine treatment.
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Several reports have suggested that cylcic guanosine 3'-5' monophosphate (cGMP) and cyclic 3'-5' adenosine monophosphate (cAMP) are involved in the regulation of cellular proliferation. Following our previous reports on the cAMP system in human brain tumors, we decided to investigate the cGMP system in the same pathological tissues by studying the activity of guanylate cyclase and cGMP-phosphodiesterase (cGMP-PDE). We found that the activity of both enzymes is lower in neurinomas and glioblastomas than in meningiomas or in normal cerebral cortex. Furthermore, the subcellular distribution of guanylate cyclase in human cerebral cortex differs from that of neurinomas and glioblastomas. On the basis of such observations we have discussed the possibility that the regulatory mechanism of the enzymes related to the cyclic nucleotide metabolism is altered in brain tumors.
Adenyl cyclase (AC) and cyclic nucleotide phosphodiesterase (PDE) have been studied in muscle from patients affected with muscular and neuromuscular diseases as well as in muscle of rats after experimental denervation. A diminution of AC was observed in Duchenne's dystrophy, in neurogenic atrophies, in inflammatory forms, in myasthenia and myotonia. PDE was diminished in Duchenne's dystrophy and increased in all other diseases considered. Both enzymes were increased in rat muscle after nerve transection. The possible mechanism underlying the biochemical alterations observed are discussed including unmasking of extra-activity due to changed metabolic environment, tissue destruction and activation of lysosomal activity.
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