Search PubMed⌕ Search

Biomedical subjects

A Michalski

Publications and source records attributed to A Michalski.

At least 37 records · Page 2Linked to original sources
PubMed1998

Novel environment as a stress-inducing factor. An event-related potentials study.

The effect of stress induced by the novelty of a situation was evaluated by means of event-related potentials (ERPs). Potentials, recorded with Fz, Cz and Pz electrodes, were evoked by flashing red and yellow LED diodes. A standard "odd ball" procedure was used, in which flashes of one color were mentally counted (target stimuli). ERPs evoked by target and non-target stimuli recorded in the first session of the experiment were compared with those recorded at least 40 min later. The early waves and P200 components indicated the increased responsiveness during the initial sessions. Amplitudes of both components were significantly larger. Latencies of the early waves were also significantly shorter. The effects were present in responses to both target and non-target stimuli. In contrast, the latency of P300 wave was significantly elongated during the first recording. Grand-averaged curves indicated also a reduction of P300 amplitude, but when individual waves were analyzed, the effect did not reach the level of statistical significance. It was suggested that the novel situation could be employed as a model of relatively pure stress, useful in the interpretation of other results such as the effects of pain.

Adult↗
PubMed1996

[The effect of hypervolemia on electrolyte level and and level of volume regulating hormones in patients with autosomal dominant polycystic kidney disease].

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequent autosomal dominant diseases. Apart from kidneys it also includes alimentary system, nervous system, cardiovascular system. ADPKD is associated with endocrinal disorders of the hormones regulating volume, arterial blood pressure and water and electrolyte balance such as: ARO, AVP, Aldo. 24 patients with ADPKD (12 with normal renal function-gr. III, 12 with advanced renal insufficiency-gr. IV) and 15 healthy subjects to compare with-gr. I and 16 patients with advanced renal insufficiency of other origin than ADPKD-gr. II were examined. In all groups the levels of Aldo, AVP and ARO in blood and Na+, K+ and creatinine concentrations in blood serum were examined Also an excretion of Na, K, creatinine with urine and clearances: CNa, CK, CKrea and filtration fractions: FENa and FEK were determined. Arterial blood pressure was measured in all groups. The above described parameters were studied in standard conditions in patients in supine position and fasting-survey I; directly after intravenous infusion of 1000 ml 0.16 M NaCl at 16.7 ml/min for 1 h-survey II and two hours after intravenous infusion-survey III. Isotonic intravenous infusion of natrium chloride increased central blood volume in the examined patients (induced hypervolemia). The received results were compared among groups in standard conditions (before infusion) as well as reaction of all groups to increased central volemia was compared. On the basis of the received results it was observed that the patients with ADPKD with normal renal function (gr III) show a significant increase of ARO, AVP, arterial blood pressure what differs them from healthy individuals (gr. I). The increased values of the above mentioned parameters were typical for the patients with chronic renal insufficiency regardless to a cause of the failure (gr. II). Consequently, patients with ADPKD showed some hormonal disorders typical for patients with advanced renal insufficiency despite fairly big difference in creatinine level and renal function condition among groups. Comparing the groups with advanced renal insufficiency (gr. II and gr. IV) it was shown that despite the same creatinine and electrolytes level in blood serum they exhibited different renine activity of serum and arterial blood pressure. These parameters were higher in the group with ADPKD. After volume expansion by 1000 ml 0.16 M NaCl infusion no significant differences between renal response to induced hypervolemia in patients with ADPKD and control groups were observed. The received results show that the patients with ADPKD exhibit disorders in hormonal regulation, water and electrolyte balance and in value of arterial blood pressure regardless to a degree of renal function. Thus genetic disease alone predisposes to the above mentioned disorder. Nevertheless, patients with ADPKD show normal mechanisms of renal volemic regulation in volume expansion conditions that can be compared to control groups. It also means that renal response to induced hypervolemia is similar in all the examined groups and is independent of renal function degree.

Adult↗
PubMed1995

The effects of glutamate iontophoresis on single cell responses and inter-neuronal interactions in the kitten visual cortex.

We studied the effect of glutamate (Glu) micro-iontophoresis on visual responses (PSTHs) and cross-correlograms of neurones recorded simultaneously in the cortex of 4-6 weeks old kittens. PSTHs and cross-correlograms were tested before, during and after Glu injections and compared with adult cats data from previous experiment. Before the injection cross-correlogram shapes and numbers did not differ in young and adult cats, whereas PSTHs differed dramatically. Glu iontophoresis typically elevated background PSTHs levels rather than peak responses in young kittens. In adult animals the opposite effect predominated. After the termination of iontophoresis visual responses were enhanced in 21% of kitten neurones. In adult cats this effect was not observed. In kittens, a clear increase of cross-correlogram strength was recorded in one neuronal pair (3.6%) after the injection terminated. In adult cats similar effect was also found in 3% of pairs.

Animals↗
PubMed1994

Correlated activity of lateral geniculate neurones in binocularly deprived cats.

Pairs of single neurones were recorded simultaneously from lateral geniculate nucleus of adult cats binocularly deprived of pattern vision by rearing in masks. Receptive fields of cells in laminae A and A1 were highly abnormal with unusually small proportion of Y-type fields and some neurones characterized by ON/OFF type of responses. In spite of these changes all crosscorrelogram patterns between spontaneous firing of these cells were similar to those previously observed in normal cats.

Animals↗
PubMed1993

[Bleeding time in patients with chronic liver diseases].

In 105 patients with chronic liver diseases, bleeding time was studied by Ivy method. A statistically significant difference was found in the bleeding time between patients with chronic hepatitis and controlled cirrhosis and patients with uncontrolled cirrhosis. In 10 out of 26 patients with prolonged bleeding time with platelet count over 100,000/mcl and prothrombin index value over 60%, clinical signs of haemorrhagic diathesis were observed. We believe that the evaluation of platelet function by measuring the bleeding time by Ivy method should enter the set of routine laboratory tests in patients with chronic liver disease.

Chronic Disease↗
PubMed1993

The effect of reversible cooling of cat's primary visual cortex on the responses of area 21a neurons.

1. Responses of sixty-four neurons in cortical area 21a were studied with areas 17 and 18 reversibly deactivated by cooling. From anatomical studies, most of area 21a input in the cat originates from these primary areas with no input from the A laminae of the lateral geniculate nucleus. 2. Both responses and spontaneous activity of all sixty-four area 21a neurons were markedly reduced when primary areas were cooled. In sixteen cells the responses were totally blocked. Temperatures of primary cortex required to produce total blockade varied between 25 and 4.5 degrees C. 3. The effect of cooling the primary visual cortex on the shape of orientation tuning curves was analysed in thirteen neurons from area 17 and in fifty-eight neurons from area 21a. In both areas, the width of the curve, when measured at its half-height, was preserved even when spike activity was reduced to below 10% of the original level. All neurons also retained their original directional preferences during cooling of the primary visual cortex. 4. The responsiveness of forty-seven neurons from area 21a was tested after rewarming of primary cortex. All but one neuron recovered their initial responsiveness within half an hour of restoring physiological temperature of primary visual cortex. 5. The results of the present study give an indication of the extent to which area 21a is sequentially related to the primary visual cortex in the processing of information.

Action Potentials↗
PubMed1992

Combination chemotherapy with vincristine, epirubicin and cyclophosphamide in small cell lung carcinoma. Polish Lung Cancer Cooperative Group.

The aim of this prospective study was to assess the activity of a combination of vincristine, epirubicin and cyclosphosphamide (VEC) in previously untreated patients with limited small cell lung carcinoma (SCLC) and to delineate the feasibility of dose escalation for epirubicin in this regimen. The chemotherapy schedule included cyclophosphamide, 1000 mg/m2, vincristine, 1 mg/m2 and escalating doses of epirubicin: 50 mg/m2, 70 mg/m2 and 90 mg/m2; respectively in three consecutive groups of patients. Drug cycles were repeated every 3 weeks. 118 patients from eight institutions were enrolled in this study between February 1986 and March 1989. Objective tumour response was observed in 81 of 116 evaluable patients (70%) including 25 patients (22%) who achieved a complete remission. Responding patients received thoracic radiation after the fourth cycle of chemotherapy. The median duration of response was 30 weeks and the median duration of survival was 52 weeks. There were no significant differences in treatment results between the consecutive groups of patients. The regimen was well tolerated for all doses of epirubicin. The main toxicities included alopecia (96%), nausea and vomiting (81%) and leukopenia (44%). Grade 4 haematological toxicity was observed in 3 patients (2.6%). No significant epirubicin dose-dependent side effects, except for mucositis were observed.

Adult↗
PubMed1992

Effects of selective pressure block of Y-type optic nerve fibers on the receptive-field properties of neurons in the striate cortex of the cat.

In an aseptic operation under surgical anesthesia, one optic nerve of a cat was exposed and subjected to pressure by means of a special cuff. The conduction of impulses through the pressurized region was monitored by means of electrodes which remained in the animal after the operation. The pressure was adjusted to selectively eliminate conduction in the largest fibers (Y-type) but not in the medium-size fibers (X-type). The conduction block is probably due to a demyelination and remains complete for about 3 weeks. Within 2 weeks after the pressure-block operation, recordings were made from single neurons in the striate cortex (area 17, area V1) of the cat anesthetized with N2O/O2 mixture supplemented by continuous intravenous infusion of barbiturate. Neurons were activated visually via the normal eye and via the eye with the pressure-blocked optic nerve ("Y-blocked eye"). Several properties of the receptive fields of single neurons in area 17 such as S (simple) or C (complex) type of receptive-field organization, size of discharge fields, orientation tuning, direction-selectivity indices, and end-zone inhibition appear to be unaffected by removal of the Y-type input. On the other hand, the peak discharge rates to stimuli presented via the Y-blocked eye were significantly lower than those to stimuli presented via the normal eye. As a result, the eye-dominance histogram was shifted markedly towards the normal eye implying that there is a significant excitatory Y-type input to area 17. In a substantial proportion of area 17 neurons, this input converges onto the cells which receive also non-Y-type inputs. In one respect, velocity sensitivity, removal of the Y input had a weak but significant effect. In particular, C (but not S) cells when activated via the normal eye responded optimally at slightly higher stimulus velocities than when activated via the Y-blocked eye. These results suggest that the Y input makes a distinct contribution to velocity sensitivity in area 17 but only in C-type neurons. Overall, our results lead us to the conclusion that the Y-type input to the striate cortex of the cat makes a significant contribution to the strength of the excitatory response of many neurons in this area. However, the contributions of Y-type input to the mechanism(s) underlying many of the receptive-field properties of neurons in this area are not distinguishable from those of the non-Y-type visual inputs.

Animals↗
PubMed1992

Effects of selective pressure block of Y-type optic nerve fibers on the receptive-field properties of neurons in area 18 of the visual cortex of the cat.

Recordings were made from single neurons in area 18 of anesthetized cats (N2O/O2 mixture supplemented by continuous intravenous infusion of barbiturate) in which one optic nerve had been pressure blocked to selectively block conduction in the largest (Y-type) fibers. Cortical neurons were stimulated visually via the normal eye or via the eye with the pressure-blocked optic nerve ("Y-blocked eye"). Several properties of the receptive fields such as their spatial organization (S or C cells), orientation tuning, and the presence and strength of end-zone inhibition appear to be unaffected by removal of the Y input. By contrast, the removal of the Y input resulted in a small but significant reduction in the size of the discharge field and in the direction-selectivity index. In three respects, peak response discharge rate, eye dominance, and velocity sensitivity, removal of the Y input had strong and highly significant effects. Thus, the mean peak discharge frequency of responses evoked by the stimulation of binocular neurons via the Y-blocked eye was significantly lower than that of responses evoked by the stimulation via the normal eye. Accordingly, the eye-dominance histogram was shifted markedly towards the normal eye (more so than in the homologous experiment conducted on area 17-Burke et al., 1992). Finally, the mean preferred velocity of responses of cells activated via the normal eye was in the vicinity of 145 deg/s, whereas for cells activated via the Y-blocked eye the value was about 35 deg/s. Overall, the results of the present study imply that (1) apart from Y-type excitatory input there are significant excitatory non-Y-inputs to area 18; these inputs at least partially consist of indirect X-type input relayed via area 17; (2) in neurons of area 18 that receive both Y-type and non-Y-type excitatory inputs, the Y-type input has a major influence on strength of the response and velocity sensitivity and a lesser influence on the direction selectivity and size of the discharge fields; and (3) area 18 contains mechanisms determining such receptive-field properties as S- or C-type organization, orientation tuning, and direction selectivity which can be accessed either by the Y input or by non-Y input.

Afferent Pathways↗
PubMed1992

Area 21a in the cat and the detection of binocular orientation disparity.

Visual response properties were examined in 115 cells, recorded in area 21a of the cerebral cortex of anaesthetized and paralysed adult cats. Cells were binocular and had receptive fields consisting of a single uniform discharge region which fired with composite ON/OFF responses to stationary flashing stimuli. Most cells were sharply tuned for orientation, but this was unaffected by changes in stimulus length. This result is consistent with a model in which the cells of area 21a receive their input from C cells of the striate cortex. Evidence for this was obtained by studying the decline in the responsiveness in area 21a that accompanied the cooling of areas 17 and 18. There was little indication that the cells of area 21a were effective detectors of spatial disparity, but their sharp monocular orientation tuning and differences in the preferred orientation of ipsilateral and contralateral eyes hinted at a role in the detection of binocular orientation disparity. Our results, however, showed that the recorded binocular disparity curves could be accounted for by summing the two monocular contributions and there was no apparent novel binocular component.

Animals↗
PubMed1989

Chronic renal failure in methylmalonic acidaemia.

The renal function of 12 patients with non vitamin B12 responsive methylmalonic acidaemia has been investigated. Eight patients had reduced glomerular filtration rates, but the plasma creatinine concentration was only raised in those with values of less than 40 ml/min per 1.73 m2 surface area. The reduction in glomerular filtration was a function of the age and the severity of the disease. Plasma urate concentrations were increased in four patients but this may be secondary to the renal disease rather than its cause.

Biopsy↗
PubMed1989

Modulation of single cell responses and neuronal interactions produced by iontophoresis of glutamate in adult cat visual cortex.

Single neuron responses and interneuronal coordinations after microiontophoretic injections of L-glutamic acid (glutamate) were examined in cats striate cortex with an aid of multielectrode extracellular recording and crosscorrelation analysis. The effects of 15 min long stimulation with glutamate were compared with spontaneous mutability observed within at least 1.5 h. A mutability coefficient was suggested for quantitative data analysis. Spontaneous changes were analyzed in 144 neuronal pairs in two anesthetized and seven pretrigeminal cats. Differences in spontaneous mutability between these groups were not significant. Fluctuations of crosscorrelograms were smaller than fluctuations of poststimulus time histograms (PST). The type of correlogram and receptive field preferred orientation and direction never changed. The effect of glutamate injection was studied in 157 neuronal pairs in four anesthetized and eight pretrigeminal cats. Excitatory responses were observed in 69% of neurons, inhibitory in 18%. The excitatory response to glutamate was accompanied with enhanced visual response in 47% of cases and with reduced visual response in 18%. Crosscorrelogram strength was reduced in 43% of pairs with excitatory response to glutamate and increased only in 23%. After the termination of iontophoresis a persistent increase of the shared input coordination was observed in two pairs in anesthetized animals and in three pairs in pretrigeminal cats. The appearance of direct excitatory coordination was found in one case in pretrigeminal cats. Alterations of PST histograms did not exceed the range of spontaneous mutability. We infer that in a small percent of neuronal pairs the short glutamate stimulation can affect interneuronal links even in adult cat.

Animals↗
PubMed1986

Spatiotemporal receptive field structure of neurons in the lateral geniculate nucleus of binocularly deprived cats.

Twelve cats were binocularly deprived of pattern vision from the time of eye opening by rearing in masks. Six cats were raised in masks for 5 to 7 months until an acute experiment (group D) and 6 others were additionally trained in visual pattern discrimination for 2 to 5 months following the initial deprivation period (group DV). In all cats the receptive fields (RFs) of neurons in lateral geniculate nucleus were analyzed with three-dimensional computer plots (response planes). The percentage of neurons encountered with homogeneous RFs (Y cells) was 7 perecent in D cats and 16 percent in DV cats. Both values are much lower than in normal cats. Y-type neurons had weakly developed surrounds of their RFs and more phasic responses than normal. Surrounds of heterogeneous (X cell) RFs were also weak or absent. X-type receptive field centers were enlarged in both D and DV animals when compared to a sample from normal cats. They were also larger in D than in DV cats, particularly within 8 degrees of eccentricity. The late components of the response patterns of X cells were weak or absent. Seven percent of neurons found in the middle of the A laminae in DV cats had an atypical (ON-OFF like) structure of their receptive field which might indicate that they were like immature X or Y neurons.

Animals↗
PubMed1984

Crosscorrelation analysis of intracolumnar neuronal connectivity in area 17 of binocularly deprived cats.

Eight cats were binocularly deprived of pattern vision by rearing in masks from the time of eye opening. Twenty five groups of 3 neurons and 28 neuronal pairs were studied in visual orientation columns of their striate cortices. The crosscorrelograms of neuronal discharges were analyzed and the inference of underlying interneuronal connectivity was made. The results were compared with the normal cats data obtained earlier in an identical experiment. Total number of existing interactions was only slightly reduced: from 95010 of analyzed pairs in normal cats to 90 percent in deprived animals. The most pronounced effect of visual deprivation was the reduction of the percentage of neuronal pairs that shared the same source of input from 61 to 34 percent. The proportion of direct excitatory connections was not affected, while an increase in the number of inhibitory correlations was found.

Animals↗