Search PubMed⌕ Search

Biomedical subjects

G Testa

Publications and source records attributed to G Testa.

At least 19 recordsLinked to original sources
PubMed1992

Long-term effects of time, medical treatment and pregnancy in 176 hyperprolactinemic women.

The changes in plasma prolactin (PRL) concentrations were studied in 176 hyperprolactinemic women over periods of 6-180 months, to evaluate the independent effects of time, drugs and pregnancy on the evolution of prolactinemia. CT scans showed pituitary adenoma in 87 (9 macroadenoma), the clinical presentations for 110 patients there amenorrhea, for 37 abnormal cycles and 29 had anovulatory sterility as an isolated symptom. 107 women underwent 191 cycles of dopaminergic treatment and 73 had pregnancies (86), either spontaneously or as a consequence of the treatment. Changes in prolactin induced by medical treatment and pregnancy were recorded and the spontaneous changes in prolactin in 38 patients (17 with adenoma) were followed over periods of 6-72 months. Final mean PRL concentrations were lower than basal though not significantly, in both 'functional' (54.4 vs. 79.2 ng/ml) and prolactinoma patients (87.3 vs. 116.4 ng/ml). Separate calculation of changes in prolactin after the course of medical treatment, pregnancies or 'just waiting' periods showed mean PRL concentrations to be significantly lower only for 'functional' patients after pregnancy. On the other hand, PRL variations in individual patients revealed that: (1) spontaneously, PRL rarely becomes lower over a few years; (2) dopaminergic treatment was associated with normalization of PRL in 13% of women; and (3) pregnancy normalized prolactin concentrations in 29% of the patients. Chi-square analysis of the PRL-lowering frequencies in functional patients showed a high cure rate for pregnancy (P less than 0.0001) and a lesser but still significant effect of drugs (P less than 0.025).

Adult↗
PubMed1989

Ethosuximide alters intrathalamic and thalamocortical synchronizing mechanisms: a possible explanation of its antiabsence effect.

Effects of systemic administration of a single dose (50 mg/kg) of ethosuximide (ESM) on extracellularly recorded thalamic (nucleus centralis lateralis, CL; nucleus reticularis, RE) and cortical neurons and on cortical EEG activity of acute cats, have been studied. In intact animals ESM led to: (a) desynchronization of cortical EEG activity; (b) reduction of cortical recruiting responses to 6 Hz stimulation of nucleus centralis medialis (CeM); (c) increased firing rate of CL units; and (d) reduction of incremental responses (IRs) of CL neurons to CeM stimulation. In midbrain reticular formation (MRF)-lesioned animals, ESM induced: (a) reduction of cortical spindle waves; (b) increment of their intraburst frequency; (c) reduction of the IR of CL neurons to 3 and 6 Hz CeM stimulation; (d) shortening of the inhibitory period following each response; and (e) no increment of spontaneous firing rate of CL units. Moreover, ESM led to important changes in the spontaneous activity of RE neurons: spike barrages, typical of these neurons in MRF-lesioned animals, became less frequent and of longer duration, being also constituted by longer interspike intervals. However, responses of RE neurons to low frequency CeM stimulation, when present, did not show any incremental phenomenon and appeared unchanged after ESM. Responses of cortical neurons to paired stimuli, applied with different interstimulus intervals, to nucleus ventralis posterolateralis or in animals with isolated cortex, to subcortical white matter, disclosed a reduction of the cortical inhibitory period following the response to the conditioning stimulus. These data suggest that ESM exerts a moderate diffuse anti-inhibitory action at both cortical and thalamic levels and an activating effect on MRF, which could also be accomplished through disinhibition. The reduction of the inhibitory phases in thalamic nuclei would alter spontaneous intrathalamic synchronizing mechanisms, leading to a decreased effectiveness of thalamocortical volleys, which are believed to be fundamental for the appearance of cortical spike and wave discharges. This hypothesis would therefore explain the specific efficacy of ESM against absence seizures.

Animals↗
PubMed1988

Dehiscence of intestinal anastomoses and anaesthesia.

This study, carried out in 62 patients undergoing surgery under general anaesthesia, has evaluated the nestigmine effects on tone and motility of the muscular rectal wall, by recording compliance and manometric values. An increase of intrarectal pressure values in patients antagonized with neostigmine has been evidenced. This finding is related to contracture and increased motility of muscular rectal wall, induced by anticholinesterase agent. In patients eligible for intestinal anastomoses, rapidly eliminated myoneural blocker such as atracurium besylate or vecuronium, should be preferred. These agents allow a spontaneous reversal of the myoneural block, without pharmacologic antagonism.

Adult↗
PubMed1987

On the intracortical activity during recruiting responses: an analysis of laminar profiles before and after topical application of GABA to the cortex.

Intracortical activity during recruiting responses (RRs) has been studied by recording laminar profiles of intracortical field potentials during repetitive stimulation, at 6 Hz, of nucleus centralis lateralis (CL) and nucleus centralis medialis (NCM) in lightly anesthetized cats, before and after topical application to the cortex of 1% GABA solution. The data obtained underwent current source density analysis (CSD) which disclosed that in the pre-GABA condition, there are two almost simultaneous sinks, one in the most superficial layer and the other in mid-cortical layers. After GABA application, a single large sink was present in mid-cortical layers. Extracellular single cortical unit activity was recorded in different animals, through a microelectrode tangentially inserted into the cortex, during repetitive stimulation of CL or NCM, both before and after GABA application. In 75% of these units there was, after GABA, a mean reduction of about 50% of firing probability while in the remaining 25% there was an increased activity. Topical application of 1% Manganese sulfate to the cortical surface appeared to completely inactivate the whole thickness of the cortex where it was applied, making evident the contribution to RRs of the potentials generated in the cortex buried in the adjacent sulci. Finally, a reciprocal facilitating effect of RRs and augmenting responses (ARs), which was studied by combined stimulation of nucleus ventralis posterolateralis (VPL) and NCM, appeared to be dependent upon an intracortical mechanism. All these data suggest that: RRs are the result of a simultaneous activation of superficial and mid-cortical layers; RRs are contaminated by a volume conducted potential arising from the cortex buried in the sulci; a superficial inhibition following the initial excitation seems to be an usual component of the response; ARs and RRs probably share a similar intracortical mechanism for incrementing the response.

Animals↗
PubMed1986

Laminar field potentials and unit activity in the cortex during visual evoked potentials in feline generalized penicillin epilepsy.

Modifications of the visual evoked potential during generalized epilepsy were investigated in feline generalized penicillin epilepsy. Visual evoked potentials and their intracortical profiles were averaged during intraburst periods and during the wave of the spike and wave complex to a fixed latency from the preceding spike. During interburst periods, the evoked potentials showed an increase in the amplitude of the early positive peak and the appearance after a variable latency period of a second consistent peak during the late phase of the evoked potential. Laminar profiles of visual evoked potentials and their current source density analysis compared with the activity of single cortical units suggested an early excitation of neuronal populations at layers II, III and IV, as seen before penicillin, followed by a variable inhibitory period and by a subsequent rebounded excitation at those same levels. In evoked potentials recorded during the wave of the spike and wave complex, the early phase was unchanged and the late positive peak and the corresponding deep sink were greatly reduced or nonexistent, although the rebounded activation of cortical units was still evident. These data support the conclusion that during feline generalized penicillin epilepsy a larger number of cortical neurons are activated and a sequence of excitation-inhibition-excitation, probably involving also subcortical structures, is brought about. Moreover, the inhibitory phase of the spike and wave complex is soon disrupted whenever a consistent sensory stimulus arrives at the cortex.

Action Potentials↗
PubMed1985

Involvement of cortical, thalamic and midbrain reticular formation neurons in spike and wave discharges: extracellular study in feline generalized penicillin epilepsy.

Extracellular activity of single units, simultaneously recorded in cortex, thalamus, and midbrain reticular formation was investigated during feline generalized penicillin epilepsy. The firing activity of neurons recorded in the cortex was invariably and consistently enhanced in coincidence with the positive peak and the positive-negative transient of the "spike" of the spike and wave complex, and it was greatly decreased during the wave. In the nonspecific thalamic nuclei three classes of neurons were identified according to their patterns of activity during the spike and wave complex: (i) neurons behaving like cortical units, (ii) neurons with enhanced firing activity during the wave and a decreased activity during the "spike," and (iii) unmodified neurons. In the nucleus lateralis posterior neurons of the third class were not found. Most midbrain reticular neurons could be classified in the same three classes of the nonspecific thalamic nuclei; however, 11% of those units increased their activity 20 to 30 ms earlier than did the cortical units (class IV). Investigation of the activities of all these neuronal populations immediately prior to a spike and wave discharge showed that the rhythmic cycle of excitation-inhibition commenced earlier in the cortical neurons than in any other subcortical neuron. Moreover, there were some nonspecific thalamic neurons of class II with an inhibitory phase exactly coincident with the activation of class IV midbrain reticular neurons. These data suggest (i) a leading role of cortical neurons in initiating and maintaining a spike and wave burst; (ii) the involvement of a corticothalamocortical circuit in timing the bursts, and (iii) an accessory reticulothalamic loop also involved in regulating the intraburst frequency of the spike and wave complex.

Action Potentials↗
PubMed1985

Effects of GM1 ganglioside in cerebrovascular diseases: a double-blind trial in 40 cases.

A randomized, double-blind trial on the effects of GM1 ganglioside in cerebrovascular diseases was done on 40 patients; the treatment (40 mg/day i.m. injection) began after the acute phase and lasted 6 weeks. 18 cases took the drug and 16 the placebo. The evaluation of the cases was made by graduating the severity of the clinical signs, and some neurophysiological and morphological parameters, i.e., EEGs, flash-evoked potentials and computer tomography scans. We found that the drug, in comparison with the placebo treatment, improved the clinical signs and also the neurophysiological parameters, whereas it was ineffective for the morphological damage. These data seem of some interest in relation to the action of GM1 ganglioside in the processes of neurotransmission and neuronal plasticity as described in the experimental animal.

Adult↗