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A Michalski

Publications and source records attributed to A Michalski.

63 records · Page 4Linked to original sources
PubMedDate not supplied

Processing of form and motion in area 21a of cat visual cortex.

Extracellular recordings from single neurons have been made from presumed area 21a of the cerebral cortex of the cat, anesthetized with N2O/O2/sodium pentobarbitone mixture. Area 21a contains mainly a representation of a central horizontal strip of contralateral visual field about 5 deg above and below the horizontal meridian. Excitatory discharge fields of area 21a neurons were substantially (or slightly but significantly) larger than those of neurons at corresponding eccentricities in areas 17, 19, or 18, respectively. About 95% of area 21a neurons could be activated through either eye and the input from the ipsilateral eye was commonly dominant. Over 90% and less than 10% of neurons had, respectively, C-type and S-type receptive-field organization. Virtually all neurons were orientation-selective and the mean width at half-height of the orientation tuning curves at 52.9 deg was not significantly different from that of neurons in areas 17 and 18. About 30% of area 21a neurons had preferred orientations within 15 deg of the vertical. The mean direction-selectivity index (32.8%) of area 21a neurons was substantially lower than the indices for neurons in areas 17 or 18. Only a few neurons exhibited moderately strong end-zone inhibition. Area 21a neurons responded poorly to fast-moving stimuli and the mean preferred velocity at about 12.5 deg/s was not significantly different from that for area 17 neurons. Selective pressure block of Y fibers in contralateral optic nerve resulted in a small but significant reduction in the preferred velocities of neurons activated via the Y-blocked eye. By contrast, removal of the Y input did not produce significant changes in the spatial organization of receptive fields (S or C type), the size of the discharge fields, the width of orientation tuning curves, or direction-selectivity indices. Our results are consistent with the idea that area 21a receives its principal excitatory input from area 17 and is involved mainly in form rather than motion analysis.

Animals↗
PubMedDate not supplied

The role of ipsilateral and contralateral inputs from primary cortex in responses of area 21a neurons in cats.

Neuronal responses in cat visual area 21a were analyzed when the primary visual cortex (areas 17 and 18) was deactivated by cooling. Ipsilateral and contralateral cortices were deactivated separately. Results established that (1) cooling the ipsilateral primary cortex diminished the activity of all area 21a cells and, in 30%, blocked responsiveness altogether, and (2) cooling the contralateral primary cortex initially increased activity in area 21a cells but, with further cooling, reduced it to below the original level although only 9% of cells ceased responding. These findings were then compared to earlier results in which bilateral deactivation of the primary cortex greatly reduced and, in most cases, blocked the activity of area 21a cells (Michalski et al., 1993). Despite the response attenuation following cooling of the primary visual cortex (either ipsilateral or contralateral), neurons of area 21a retained their original orientation specificity and sharpness of tuning (measured as the half-width at half-height of the orientation tuning curve). Direction selectivity also tended to remain unchanged. We concluded that for area 21a cells (1) the ipsilateral primary cortex provides the main excitatory input; (2) the contralateral primary cortex supplies a large inhibitory input; and (3) the nature of orientation specificity, sharpness of orientation tuning, and direction selectivity are largely unaffected by removal of the ipsilateral hemisphere excitatory input or the contralateral hemisphere inhibitory input.

Animals↗
PubMedDate not supplied

Accuracy of t-PA, u-PA, PAI-1 and PAI-2 estimation in human bile by ELISA kits.

UNLABELLED: The aim of this study was to establish the accuracy of determination of fibrinolytic proteins in human bile using commercial kits. MATERIAL AND METHOD: Gall bladder bile was obtained from patient undergoing laparoscopic cholecystectomy. The concentrations of tissue plasminogen activator (tPA), urokinase (uPA) and plasminogen activator inhibitor-1 (PAI-1) and inhibitor-2 (PAI-2) in bile were measured by enzyme linked immunoassay. Afterwards we conducted so called 'recovery test'. RESULTS: Recovery percents of t-PA, u-PA, PAI-1, PAI 2 were very high i.e. 91.94, 94.07, 93.95, 91.2. We concluded that human fibrinolytic proteins in bile could be detected very accurately using commercial kits.

Bile↗
PubMedDate not supplied

Plasminogen activators (t-PA and u-PA) and plasminogen activators inhibitors (PAI-1 and PAI-2) in some myeloproliferative syndromes.

INTRODUCTION: Clinical observations and laboratory data indicate that patients with myeloproliferative syndrome (MPS) have hemostasis disorders that manifest with haemorrhagic diathesis or thrombotic disease. The role of fibrinolytic system is not clear in the pathomechanism of the disorders. In the study we aimed to evaluate fibrinolysis system in blood plasma of the patients with selected myeloproliferative syndromes on the basis of examinations of plasminogen activators (tissue--t-PA and urokinase-type--u-PA) and type 1 and type 2 plasminogen activator inhibitors (PAI-1 and PAI-2). MATERIAL AND METHODS: Forty-two patients (F/M 28/14) aged 36-78 years (average age--54 years) were enrolled into the study. Among the patients were 20 individuals with chronic myeloid leukaemia (CML), 17 with essential thrombocytemia (ET) and 5 with myelofibrosis (MF) treated in Provincial Haematological Outpatient Clinic in Bydgoszcz. Forty healthy volunteers (F/M 30/10) aged 24-65 (average 53) were included in control group. In citrate venous blood, the following parameters were determined: concentrations of antigen t-PA, u-PA, PAI-1, PAI-2, concentration of plasmin-alpha-2-antiplasmin complexes (PAP) determined with the use of ELISA technique, PAI-1 activity with amidolytic method, euglobulin lysis time (ELT) according to Kowarzyk-Buluk and fibrinogen/fibrin degradation products (FDP) concentration with the use of Merskey's method. RESULTS: Performed evaluations show that besides normal ELT elevated concentrations of FDP and PAP complexes occur in the blood of patients with myeloproliferative syndromes (MPS.). In studied myeloproliferative syndromes, high concentration of PAI-1 Ag and very low activity of PAI-1 were observed. In the patients with MPS intensified plasminogenesis and increased fibrin degradation were demonstrated. The role of granulocyte elastase is considered in activation of fibrinolysis system.

Adult↗
PubMedDate not supplied

Thrombomodulin--endothelial thrombin receptor in blood of patients with unstable angina pectoris.

BACKGROUND: Thrombomodulin (TM) a membrane receptor for thrombin generated in blood in vivo, is present on the surface of vascular endothelium cells. The aim of our work was the determination of thrombomodulin in the blood of patients with unstable angina pectoris. MATERIAL AND METHODS: In the study took part 87 patients with unstable angina pectoris (40 women and 47 men) at age 41-79 years. Thrombomodulin was determined in citrated blood plasma with the use of enzyme immunoassay ELISA with the diagnostic kit manufactured by American Diagnostica. RESULTS: Statistically significant higher thrombomodulin concentration (sTM) was found in the patients when compared with the values recorded in control group. Elevated sTM levels depended on patients age and they were significantly higher in patients over 50 years old. There were no statistically significant differences with respect to patients gender and coexistent risk factors such as arterial hypertension, diabetes or smoking, but significantly higher sTM concentration was observed in patients with high serum cholesterol level. CONCLUSION: Elevated sTM concentrations result from the damage to vascular endothelium cells by the atheromatous process manifested in unstable angina pectoris.

Adult↗