Interphase cytogenetics on paraffin-embedded sections of ovary for detection of genomic constitution in a patient with Turner's syndrome and chromosomal mosaicism

The difficulty of detecting sex chromosome mosaicism cytogenetically hinders the finding of an acceptable explanation for phenotypic-genotypic discrepancy amongst those patients. Fluorescence in situ hybridization (FISH) permits the genomic identification of patients with mosaic karyotypes in interphase nuclei by utilising an X chromosome-specific DNA probe (interphase cytogenetics). We evaluated the efficiency of interphase cytogenetics in the detection of the genomic constitution of the ovary from a patient with Turner's syndrome having mosaicism (46,XX/45,X0) previously established by blood lymphocyte karyotyping. We used a biotin-labelled alphoid repetitive sequence, pBAMX5, specific for the centromeric region of the human X chromosome. Although examination of ovarian sections and blood lymphocytes by FISH showed the presence of both 46,XX and 45,X0 cell lines, the genomic constitution of the germ cells/oocytes in ovarian primordial follicles was shown to be normal (46,XX). Our results (1) show the high applicability of interphase cytogenetics on paraffin sections, (2) indicate the possibility of genomic screening of different tissues that are otherwise not amenable to routine cytogenetic investigation and (3) offer a reliable methodological approach to defining accurate by the percentage of abnormal karyotypes in mosaicism of different organs and non-dividing tissues.     

Formation of long-wavelength chlorophyllide (Chlide695) is required for the assembly of Photosystem II in etiolated barley leaves

Chlorophyll(ide) spectroscopic properties and Photosystem II assembly, monitored by 77 K variable fluorescence, were studied in etiolated barley leaves as a function of the extent of protochlorophyllide photoreduction by a single millisecond light flash of different intensities. Variable fluorescence, measured 2 hours after the flash, was only detected when the extent of phototransformation was higher than a threshold value of 0.4. Its development paralleled the formation of a chlorophyll emission component at 685 nm, which itself derived from long-wavelength chlorophyllide with an emission maximum at 695 nm. At low flash intensities, short-wavelength chlorophyllide forms preferentially accumulated and no Photosystem II fluorescence was detected after 2 hours. Chlorophyllide esterification was independent of the extent of phototransformation. These results suggested that the formation of long-wavelength chlorophyllide was essential for further assembly of Photosystem II. This interpretation was strengthened by the observed inhibition of both long-wavelength chlorophyllide formation and of variable fluorescence development in leaves treated with -aminolevulinic acid or in untreated leaves subjected to repeated flashes of low intensity.     

Optimization of the bare platinum electrode as an oxygen measurement system in photosynthesis

This paper is concerned with the definition of the standard conditions required for optimum operation of the bare platinum electrode with photosynthetic samples. Experimental evidence shows the following: 1) Polarization circuits should have zero resistance; 2) The electrolyte layer between the electrodes should have a conductance higher than 54×10^{–6 –1} per mm² of platinum electrode area; 3) The electrodes should be polarized just before taking the measurements. All these facts can be interpreted in terms of phenomena occurring on the electrode: The adsorption of hydrogen on the electrode imposes the need for low resistances in the system, and oxygen consumption by the electrode is minimized by polarizing the electrodes as late as possible. This investigation increases the reliability of the bare platinum electrode and gives a basis for a comparison of the results from different experiments. Demonstrations of the pertinence of these conditions are made in our lab with the algae Dunaliella Tertiolecta.     

Evidence for a linear variation of the miss and single hit S-state probabilities with the flash number,measured by oxygen evolution in Dunaliella tertiolecta

Oxygen evolution in Dunaliella tertiolecta under flashing light was measured with a bare electrode, at a 10 Hz frquency. The sigma coefficients of the oxygen evolution recurrence law (Thibault (1978) J Theor Biol 73, 271) were determined using groups of nine consecutive points. The S-state transition probabilities were computed from the sigma coefficients and plotted as a function of the flash number of the first of the points used. Low standard deviations over the sigma coefficients resulted from the use of our system (Meunier & Popovic (1988) Rev Sci Instr 59, 486). We observed a linear lowering of the miss probability with time, and a linear rise of the single-hit probability with the same absolute value of the slope. The hypothesis that the slopes were zero was statistically tested and was rejected with a 99.9% confidence interval. Our work demonstrates that, to be accurate, an oxygen evolution model has to take the variations in the properties of S-states into account.International Journal of Fracture 76 (1995) R37     

Determinants of LV diastolic function during atrial fibrillation: beat-to-beat analysis in acute dog experiments

Left ventricular (LV) diastolic function during atrial fibrillation (AF) remains poorly understood due to the complex interaction of factors and beat-to-beat variability. The purpose of the present study was to elucidate the physiological determinants of beat-to-beat changes in LV diastolic function during AF. The RR intervals preceding a given cardiac beat were measured from the right ventricular electrogram in 12 healthy open-chest mongrel dogs during AF. Doppler echocardiography and LV pressure and volume beat-to-beat analyses were performed. The LV filling time (FT) and early diastolic mitral inflow velocity-time integral (E(vti)) were measured using the pulsed Doppler method. The LV end-diastolic volume (EDV), peak systolic LV pressure (LVP), minimum value of the first derivative of LV pressure curve (dP/dt(min)), and the time constant of LV pressure decay (tau) were evaluated with the use of a conductance catheter for 100 consecutive cardiac cycles. Beat-to-beat analysis revealed a cascade of important causal relations. LV-FT showed a significant positive linear relationship with E(vti) (r = 0.87). Importantly, there was a significant positive linear relationship between the RR interval and LV-EDV in the same cardiac beat (r = 0.53). Consequently, there was a positive linear relationship between LV-EDV and subsequent peak systolic LVP (r = 0.82). Furthermore, there were significant positive linear and negative curvilinear relationships between peak systolic LVP and dP/dt(min) (r = 0.95) and tau (r = -0.85), respectively, in the same cardiac beat. In addition, there was a significant negative curvilinear relationship between dP/dt(min) and tau (r = -0.86). We have concluded that the determinants of LV diastolic function in individual beats during AF depend strongly on the peak systolic LVP. This suggests that the major benefit of slower ventricular rate appears related to lengthening of LV filling interval, promoting subsequent higher peak systolic LVP and greater LV relaxation.     

Population density of Diabrotica virgifera virgifera LeConte beetles in Serbian first year and continuous maize fields

A 5‐year field survey examined western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) beetle density in Serbia from 2002 to 2006. First‐, second‐, third‐, fourth‐ and fifth‐year maize fields were sampled; they represented 64.61%, 21.66%, 9.45%, 3.53% and 0.75% of all sampled fields respectively. Results showed that the mean WCR beetle population density from 794 maize fields differed depending on cropping history. Minimum mean WCR/trap/day was 0.0 in the first‐year maize fields in 2002 and 2006. Maximum mean WCR/trap/day was registered in the fourth‐year and the fifth‐year maize fields (27.8 and 21.2 respectively). Mean population density of WCR adults increased with the number of years of continuous maize from 1.17, 4.61, 6.41, 10.30 up to 13.53 WCR/trap/day for first‐fifth‐year maize fields respectively. Mean WCR/trap/day ± SE exceeded the economic population threshold of >6 WCR/trap/day in third‐year continuous maize fields. Out of 794 maize fields, 697 (87.78%) registered a mean population density below the <6 beetles/trap/day threshold. In only 97 fields was WCR population density >6 beetles/trap/day, a finding that predicts a risk of economic damage to a subsequent maize planting. These data are representative of the Serbian situation from 2002 to 2006; they indicate that WCR are well dispersed across commercial maize fields in Serbia. These results provide new insight into the current low WCR population densities in maize fields managed by crop rotation, a finding that can help in creating long‐term management strategy.     

Kinetics of proton transport into influenza virions by the viral M2 channel

M2 protein of influenza A viruses is a tetrameric transmembrane proton channel, which has essential functions both early and late in the virus infectious cycle. Previous studies of proton transport by M2 have been limited to measurements outside the context of the virus particle. We have developed an in vitro fluorescence-based assay to monitor internal acidification of individual virions triggered to undergo membrane fusion. We show that rimantadine, an inhibitor of M2 proton conductance, blocks the acidification-dependent dissipation of fluorescence from a pH-sensitive virus-content probe. Fusion-pore formation usually follows internal acidification but does not require it. The rate of internal virion acidification increases with external proton concentration and saturates with a pK(m) of ～4.7. The rate of proton transport through a single, fully protonated M2 channel is approximately 100 to 400 protons per second. The saturating proton-concentration dependence and the low rate of internal virion acidification derived from authentic virions support a transporter model for the mechanism of proton transfer.     

Robot-based methodology for a kinematic and kinetic analysis of unconstrained,but reproducible upper extremity movement

Although arm movements play an important role in everyday life, there is still a lack of procedures for the analysis of upper extremity movement. The main problems for standardizing the procedure are the variety of arm movements and the difficult assessment of external hand forces. The first problem requires the predefinition of motions, and the second one is the prerequisite for calculation of net joint forces and torques arising during motion. A new methodology for measuring external forces during prespecified, reproducible upper extremity movement has been introduced and validated. A robot-arm has been used to define the motion and 6 degrees of freedom (DoF) force sensor has been attached to it for acquiring the external loads acting on the arm. Additionally, force feedback has been used to help keeping external loads constant. Intra-individual reproducibility of joint angles was estimated by using correlation coefficients to compare a goal-directed movement with robot-guided task. Inter-individual reproducibility has been evaluated by using the mean standard deviation of joint angles for both types of movement. The results showed that both inter- and intra-individual reproducibility have significantly improved by using the robot. Also, the effectiveness of using force feedback for keeping a constant external load has been shown. This makes it possible to estimate net joint forces and torques which are important biomechanical information in motion analysis.