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Biomedical subjects

V Pollak

Publications and source records attributed to V Pollak.

At least 19 recordsLinked to original sources
PubMed1998

Expression and regulation of the thrombopoietin receptor variants MPLP and MPLK in PBMC.

The human c-mpl proto-oncogene encodes the receptor for thrombopoietin (TPO), which plays a central role in magakaryopoiesis and platelet production. Recent results showed that c-mpl mRNA expression is restricted to CD34(+) cells, megakaryocytes, and platelets. The authors analysed mRNA expression by reverse transcription and PCR (RT-PCR) of the transmembrane Mpl variants, MPLK and MPLP, in magakaryocytic cell lines, peripheral blood mononuclear cells (PBMC), lymphocytes, and monocytes. Transcription of both Mpl variants was detected in freshly isolated PBMC and the megakaryocytic cell line, DAMI, whereas none could be detected in the megakaryocytic cell line Meg-01. The cytokines TPO, interleukin 11 (IL-11), erythropoietin (EPO), and stem cell factor (SCF), which are known stimulators of megakaryopoiesis, but not interleukin3 (IL-3), increased MPLP mRNA detection in PBMC during 96 h of incubation. However, concomitantly the detection of MPLK transcripts decreased in these cells. MPLP was also detected in monocytes, B-lympocyte and T cell populations. In contrast, MPLK mRNA expression was low in monocytes, B and T cells, and no clear increase in transcription detection was observed during stimulation of these cells.

B-Lymphocytes↗
PubMed1989

Hemisphere asymmetry of alpha burst sequential organization in depression.

A new quantitative EEG index based on the sequential variability of the frequency of occurrence of alpha bursts (alpha-BVI) was utilized for investigating the respective role of the two hemispheres in depression and their relationship with two clinical dimensions of this illness: psychomotor retardation and blunted affect. The EEG (at P3 and P4 referred to Fz) was recorded during rest periods in two groups of patients selected according to their scores on various clinical scales: one consisted of 12 patients characterized by psychomotor retardation (PMR group), the other of 9 patients characterized by blunted affect (BA group). A control group of 12 normal subjects was recorded in the same conditions. All subjects were dextral. The following main results were obtained: (1) in both groups of patients the right and the left alpha-BVI were, before treatment, significantly lower than those of the controls. (2) In controls, the sequential alpha burst variability was identical on both hemispheres. (3) In patients, before treatment, the right hemisphere alpha-BVI was significantly lower than the left. (4) Electro-clinical correlations were also observed: (A) in the BA group, before treatment, (a) between the degree of blunted affect and the decrease of the right alpha-BVI, (b) between ideoverbal retardation and the decrease of the left alpha-BVI (these correlations disappeared after treatment); (B) in the PMR group, ideoverbal retardation was, on the contrary, correlated to a right alpha-BVI decrease, this correlation persisting after treatment. These results are discussed according to the role of each hemisphere in depression.

Adult↗
PubMed1981

High tension surface EMG.

This paper considers the relationship between various averages of the high interference EMG and these parameters and the resulting tension. Isometric contraction and static conditions are assumed. At first it is assumed that only motor units belonging to a single type are present. In this case muscle tension is proportional to the extrapolated expression for the low interference EMG. Proportionality between tension and spike frequency, reported by some investigators, is obtained if the twitch tension of recently recruited motor units increases with advancing recruitment only very slowly. Proportionality between tension and r.m.s. EMG is obtained, if the twitch of newly recruited unit increases approximately proportionally with tension. The relation between force and EMG parameters changes in the region of the highest voluntary forces, where all available motor units are recruited and the only mechanism for controlling force is the firing frequency. At high interference levels integrated and r.m.s. EMG are intrinsically proportional to one another. In the final paragraph it is shown, that the conclusions obtained apply also to inhomogeneous muscles.

Electromyography↗
PubMed1975

An experimental high-performance photodensitometer for quantitative chromatography. I. Design and construction.

A new and experimental photodensitometer designed for quantitative chromatography is described. The principal features of the instrument were based upon the results of an extensive theoretical analysis and incorporate a mechanical arrangement for the production fo a flying spot and an optical path in which two beams of light are separated after interaction with the medium. The device is constructed so as to be suitable for operation in the three principal modes; in reflectance measurements only the ratio of the beam signals is formed, whilst in transmittance measurements the ratio is converted to logarithmic form, in the fluorescence mode only a single beam is used. The spectral range of the instrument extends from the red end of the visible spectrum to the medium ultraviolet, and quartz optics are utilized in most of the optic elements. A quartz halogen lamp and a xenon-mercury lamp may be used alternatively as the light source. Changeable interference filters are employed to determine the spectral position of the light beams and semiconductor photo-diodes with sensitivities extending into the ultraviolet are used as photo-detectors. In the determination of the sensitivity limits of the device the photo-diodes were replaced by photomultipliers and the apparatus was shown to fulfil most of the calculated thoeretical predictions.

Biomedical Engineering↗