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Biomedical subjects

A Michalski

Publications and source records attributed to A Michalski.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1983

Interactions between cat striate cortex neurons.

A series of simultaneous recordings from several striate cortex neurons were made in paralyzed, anesthetized cats. Recordings were obtained with one or two bundles of extra fine wires and originated from one and two cortical orientation columns. Standard PST histograms and, in some cases, response planes were used to analyse the neuronal receptive fields. Functional connectivity between neurons was assessed by cross-correlation of their spike trains. It was found that 61% of neuronal pairs found within a column shared the same input, either excitatory or inhibitory, Even if neurons in a pair belonged to two different columns separated by 1mm lateral distance, 40% of pairs still exhibited shared input coordination. This type of coordination could also encompass all combinations of simple and complex fields in the pair. Direct connections between neurons were found almost exclusively within columns: excitatory connections were found in 20% of cases and inhibitory in 8%. Direct connections were often accompanied by the other types of interactions. Only one example of excitatory and one of inhibitory direct connections were found between columns. In both cases preferred orientations were almost identical.

Animals↗
PubMed1983

Responses of area 17 neurons in cats binocularly deprived by rearing in hoods.

Responses of single units of area 17 were recorded in cats binocularly deprived by rearing in hoods. Neurons were recorded in pairs or in three-neuron groups with multichannel microelectrodes. Of 131 units recorded 22 percent were not visually excitable. The rest were predominantly monocularly driven. Response strength defined as the PST peak-to-background ratio was lower than 10 in 90 percent of cells. The orientation selectivity defined as the ratio of response strengths for the preferred and null stimulus orientations was lower than 5 in 79 percent of neurons. Directional selectivity was detected in 22 percent of units. The aim of this paper is to show that, considering the electrophysiological effects in cortica1 area 17, rearing in hoods can be used instead of eyelid suturing. This paper describes the standard parameters of units that were subsequently used for the analysis of interneuronal connectivity in visually deprived cortex (10).

Adaptation, Physiological↗
PubMed1981

Diminution of cortical visually evoked potentials during the following eye-movement in the cat.

Six cats with brainstem transection at the pretrigeminal level were used. Visually evoked potentials (VEPs) to a diffused flash were recorded in the marginal, suprasylvian, ectosylvian and sigmoid gyri under three situations: the eyes were motionless in the position of rest, the eyes followed a moving object, and the eyes moved spontaneously. In the marginal and ectosylvian gyri the VEPs were smaller in the second situation, compared to the first and third. It is concluded that the VEP reduction is not produced by the eye-movement itself, but by the process of selective attention to the followed stimulus.

Animals↗