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T Tomas

Publications and source records attributed to T Tomas.

18 recordsLinked to original sources
PubMed1992

A comparison of changes in spontaneous (EEG) and evoked brain activity induced by chlorphenvinphos and physostigmine in rats and rabbits.

The effects of single i.p. injections of two cholinesterase inhibitors, chlorphenvinphos (CVP) and physostigmine, on hippocampal and cortical EEG and flash evoked potentials in occipital cortex were compared in rabbits and rats. A comprised method of spectral analysis was employed for evaluation of changes in EEG. The obtained results showed that in both species the changes in hippocampal and cortical EEG after administration of CVP were relatively small or negligible in comparison with those after physostigmine administered in doses resulting in comparable (or even lesser) inhibition of blood cholinesterase (ChE). Neither CVP nor physostigmine resulted in significant changes in the morphology of the flash evoked potentials. The data do not confirm the suggestion that brain electrical activity is the most sensitive index of neurotoxicity resulting from exposure to organophosphate ChE inhibitors.

Animals↗
PubMed1991

Changes in brain bioelectrical activity (EEG) after repetitive exposure to an organo-phosphate anticholinesterase. II. Rat.

Effects of repetitive exposure (ten times in a period of two weeks) to chlorphenvinphos (CVP), at daily doses of 0.5 and 1.0 mg/kg, i.p., were studied in adult male Wistar rats of imp-DaK stock. It was found that 3 hrs after the last exposure, the cholinesterase (ChE) activity in the blood and brain was close to 50% of the control value in the 0.5 mg/kg group and less than 50% in the 1.0 mg/kg group. In both groups, normalization of ChE activity in plasma took less time than in erythrocytes, and the normalization of ChE activity in erythrocytes proceeded faster than in the majority of the brain areas studied. Electrophysiological investigations revealed a retardation of age-related epileptic-like cortical activity. This effect, however, was present only in the 1.0 mg/kg group, and only in the period of decreased ChE activity in the brain. Spectral analysis revealed an increase in 1-4 Hz activity in the cortical EEG of the 0.5 mg/kg group and heightened theta activity (4-7 and 7-9 Hz bands) in the hippocampal EEG of the 1.0 mg/kg group. The later effects were detected after a time sufficient for full normalization of ChE activity and manifested themselves most clearly in the presence of an acoustic stimulus associated with pain. The above results are in agreement with earlier observations on rabbits exposed repetitively to CVP. Data from both species suggest that, in the case of repetitive exposure to CVP, neither plasma nor erythrocyte ChE activity is a reliable indicator of toxicity, and that such exposure to this OP may lead to changes in EEG outlasting the period of lowered ChE activity in the blood and brain.

Animals↗
PubMed1989

Changes in physiological and electrophysiological parameters in rabbits after single exposure to chlorphenvinphos.

In order to evaluate some of the central effects of an organophosphorus pesticide--chlorphenvinphos (CVP), the time course of changes in the activity of blood cholinesterase (ChE), body temperature and hippocampal EEG were compared in rabbits after acute i.p. exposure. The pesticide was administered twice at an interval of 80-90 days. The Deichmann-LeBlanc scheme of dosing (one animal/one dose) was adopted starting with 22 mg/kg. CVP resulted in a dose-dependent decrease in plasma and erythrocyte ChE activity, a decrease in body temperature ranging from 0.7 degrees to 3.5 degrees C, and in an increase in content of the immobility-related, rhythmic slow activity (I-RSA) in the hippocampal EEG. Changes in body temperature appeared at lower doses than those in the hippocampal EEG. Contrary to the changes in ChE activity, which lasted 4-30 days, those in body temperature and in hippocampal EEG disappeared within 24 hours after the injection. CVP administered at the same dose 80-90 days after the first injection, resulted again in an inhibition of ChE activity, but the effect on the hippocampal EEG was less clear, and that on body temperature was variable; no effect, an increase or a decrease appeared. The data suggest that: i) body temperature is a more sensitive index of a central action of CVP administered for the first time than the hippocampal EEG; ii) the brain cholinergic mechanisms are relatively resistant to the acute action of the OP and undergo fast adaptive changes; iii) even single exposure to CVP may produce some long-lasting functional changes in the brain of some subjects, which has been proven by the changed response to the second exposure.

Animals↗
PubMed1989

Effects of single exposure to chlorphenvinphos, an organophosphate insecticide, on electrical activity (EEG) of the rat brain.

The effect of a single exposure to an agricultural insecticide, chlorphenvinphos (CVP), an organophosphorus anticholinesterase, on neocortical seizure activity induced or promoted by cardiazol, and on hippocampal and neocortical EEG was studied in rats. It was found that CVP, given intraperitoneally in doses of 1.0 and 3.0 mg/kg, resulted in no changes in the number and in the duration of epileptic bursts occurring spontaneously, as well as in the content of the hippocampal theta rhythm. The effect of cardiazol (12.5 mg/kg, i.p.) was slightly diminished when the drug was given 3 hours, but not 14 days, after the injection of CVP. I.p. injection of a carbamate cholinesterase inhibitor, physostigmine, in a dose of 1.0 mg/kg resulted in a dramatic increase of the theta content in the hippocampal EEG, and in the total disappearance of the spontaneous seizures. Determination of cholinesterase activity in blood and in the brain in a separate group of subjects showed that after injection of physostigmine (1.0 mg/kg), the inhibition of this enzyme does not exceed the inhibition after injecting CVP in the doses used. It has been suggested that the differences between CVP and physostigmine in their potential to reduce spontaneous epileptic activity and to induce the hippocampal theta rhythm may be due to somewhat antagonistic action of CVP on cholinergic postsynaptic receptors.

Animals↗
PubMed1985

[Decrease in the respiration rate in mice as an indicator of the irritating effects of chemical substances on the upper respiratory tract].

A method of measuring a decrease in the respiration rate as an index of chemical substances irritating effects upon mice's upper respiratory tract has been checked and adopted. A dose of irritating substances resulting in the respiration rate decrease by 50%--RD50 has been determined, as related to exposure to chlorine, ammonia and acrolein. The RD50 values for chlorine and acrolein approximated those quoted by Alarie Y., whereas for ammonia exposure this value differed.

Acrolein↗
PubMed1983

[Evaluation of the workload of weavers based on the analysis of cardiac function and changes in heart rate].

The paper is aimed at an analysis of the dependences between occupational work performance and heart rate. The examinations covered weavers working on two different types of looms, using a telemetric measurement of pulse rate with a simultaneous precise analysis of the structure activities performed. The results indicated statistically significant differences in pulse rate mean values and in the duration of activities performance. It was also demonstrated that the structure of activities significantly affects the workload, as evidenced by the heart rate.

Adult↗
PubMed1975

ADH release from cut pituitary stalk and intact pituitary gland during amygdala stimulation at various frequencies in rats.

Changes in antidiuretic substance (i.e., vasopressin) release from the cut pituitary stalk and the intact pituitary gland were observed during electrical stimulation of amygdala medial nucleus. Electrical pulses of 4 or 36 cycles per second (cps) were used and in both cases the same energy (about 2.160 nanowatt seconds) per 1.5 sec-train of electrical pulses remained constant. Antidiuretic substance release from the hypothalamic end of the cut pituitary stalk and from the intact pituitary gland increased during the 36-cps electrical stimulation of amygdala medial nucleus, however the 4-cps electrical stimulation of this structure did not produce any changes in these processes. The results obtained indicate that the medial nucleus of amygdala is able to change the function of the hypothalamo-hypophysial system and can be motivated with high frequency stimulating pulses.

Amygdala↗
PubMedDate not supplied

Sliding flap of conjunctival limbus to prevent recurrence of pterygium.

BACKGROUND: Several techniques have been advocated for the excision of a pterygium: bare sclera, conjunctival flaps, free conjunctival graft, and labial mucous membrane graft. METHODS: Twenty eyes were treated with a sliding flap of limbal conjunctiva into the scleral bed of the excised pterygium, using 7-0 and 8-0 Vicryl sutures. Corticosteroids and tear substitutes were administered postoperatively. RESULTS: There was one recurrence in the 20 eyes performed with 1 year follow up. CONCLUSIONS: Recurrence was limited to that of 5% (1 case out of 20). Postoperative inflammatory reaction was minimal.

Adult↗
PubMedDate not supplied

Tomas hook.

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Humans↗