Biomedical subjects
Publications and source records attributed to P Mainardi.
A simple method for the determination of the proportion of true GABA within labeled "GABA" used for membrane binding assay is presented. The method is intended for the assessment of the integrity of refrigerator (+4 degrees C) stored labeled neurotransmitter. Its application allows a precise determination of the binding parameters.
An electrophoretic method for the separation of gamma-aminobutyric acid (GABA) from its metabolites after GABA-transaminase attack is presented. The method is based on the fact that at neutral pH GABA has no net electrical charge, whereas its major metabolites, succinic acid and Krebs cycle intermediates, are negatively charged. The method appears to be especially suitable for evaluation of true-labeled neurotransmitter within the radioactivity which is found in synaptosomes after labeled GABA-uptake studies.
A parenteral penicillin model of epilepsy in the rat was investigated with the aim of evaluating its reliability. Behavioral and EEG patterns were strongly variable in a group of 100 rats injected with 1,000,000 IU/kg of penicillin i.p. Gross counts of spikes were Fourier transformed and grouped into two time windows in 24 out of the 100 rats. Analysis of variance applied to compare the two time windows showed a sufficient suitability of the phenomenon for antiepileptic drug testing purposes. Five subsequent injections of penicillin performed in 8 rats showed that a spontaneous decrease of the response takes place, preventing a crossover design in pharmacological analyses. Evans Blue studies demonstrated that there was not a breakdown of the blood-brain barrier; this model can be used for testing anticonvulsants unable to penetrate the blood-brain barrier.
In the sural nerve of a 62-year-old woman with impaired glucose tolerance test and polyneuropathy, many intra-axonal polyglucosan bodies were observed. Polyglucosan bodies have been described in spontaneously or alloxan-diabetic rats, but are not usually observed in human diabetic neuropathy. Since intra-axonal polyglucosan bodies can occur in the sural nerve in various diseases and in aging, they are considered as non-specific changes. Their presence is probably related to a primary axonal neuropathy.
The effect of a suspension of GABA and phosphatidylserine (PS), phosphatidylcholine, or phosphatidylethanolamine was studied on penicillin-induced epileptic activity in rats. GABA-PS significantly reduced the number of spikes, in comparison with either the other phospholipid compounds or normal saline. No effect was observed after GABA or PS administration alone. We suggest that the different effects probably depend on extracellular and intracellular factors.
Spontaneous rupture of a pancreatic pseudocyst into the portal vein is described. This has been previously reported in only five cases. Diagnosis was made by computed tomography (CT) and was confirmed by CT-guided transhepatic portography.
The interaction of the negatively-charged phosphatidylserine (PS) and gamma-Aminobutyric acid (GABA) is examined in black lipid membranes (BLM) and inverse micelles. GABA does not permeate through PS membranes and, in concentrations of 10(-5)-10(-4) M, it reduces the negative potential at the membrane-aqueous solution interface. The effect is owing to the adsorption of the GABA cationic species and the consequent decrease of the negative surface charge density of the membrane. When the intrinsic pH of the membrane-solution interface is considered, the Gouy-Chapman-Stern theory describes the GABA screening effect and makes it possible to calculate the GABA-PS binding constant. This value is compared with that obtained measuring the partition of 14C-GABA between an organic phase containing PS and the aqueous solution. The results presented strongly suggest that the electrostatic force plays a major role in GABA-PS interaction.
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Sprague-Dawley rats with interictal and ictal spike activity induced by intraperitoneally injected isoniazid (INH) were treated, 5 min before or 30 min later, with liposome-entrapped gamma-aminobutyric acid (GABA) (LEG) or GABA or phosphatidylserine. Crossover injections were given in random sequence and INH alone ws also injected in every animal as a control. LEG inhibited either seizures or interictal spikes in both groups. No decrease of epileptogenic activity was seen after GABA or phosphatidylserine treatment alone. It is suggested that LEG could contribute to the reconstitution of the GABA pool decreased by INH.
Synaptosomes were prepared from rat brain by a discontinuous Ficoll gradient method and used for studying the uptake of labelled GABA. Two GABA uptake components were evidenced, a high (Km = 3.13 microM) and a low (Km = 92.4 microM) affinity one. Preincubation of synaptosomes with two different activators of protein kinase C, phorbol 12, 13-diacetate (PDAc) and oleyl-acetyl glycerol (OAG), resulted in a change of GABA uptake. In particular, the low affinity component increased its Vmax by 58-74%, with no change in the Km. No statistically significant modification was detected for the high affinity component.
We report a series of 10 papillary cystic neoplasms of the pancreas evaluated in our institution. The lesions are analyzed in retrospect to define the existence of eventual specific imaging patterns as well as to point out the existing problems of differential diagnosis versus other pancreatic tumors.
Bronchogenic cysts, unlike the other mediastinal cysts, exhibit a high incidence of complications, which makes their resection advisable even if no symptoms are present. The correct diagnosis should thus be made with the available imaging modalities. We reviewed our series of 11 bronchogenic cysts, all of them studied with conventional radiology (CR), as well as with such newer imaging modalities as CT and/or MRI. All mediastinal lesions had fluid density at CT and were homogeneously hyperintense on T2-weighted MR images. On the contrary, on T1-weighted images, some lesions were hypointense and some hyperintense, probably because of their rich protein content. In contrast, hilar or pulmonary lesions had air inside, except for one case--characterized by multiple localizations--in which the hilar lesion exhibited the same fluid density as the mediastinal lesions. The CT or MR finding of a lesion with fluid content below the carina permits a nearly unquestionable diagnosis of bronchogenic cyst since the other cystic lesions involve this region very rarely. In all the other cases, other types of mediastinal or hilar-pulmonary lesions cannot be ruled out. In particular, in case of cysts in paraesophageal site, no imaging modality permits to differentiate bronchogenic from enteric cysts; in some cases, the differential diagnosis may be impossible even with histology of the resected specimen.
We report a series of 10 papillary cystic neoplasms of the pancreas evaluated in our institution. The lesions are analyzed in retrospect to define the existence of eventual specific imaging patterns as well as to point out the existing problems of differential diagnosis versus other pancreatic tumors.