Biomedical subjects
Publications and source records attributed to M Vlad.
A ratchet-type average velocity is shown to appear for test particles moving in a stochastic potential and a magnetic field that is space dependent. This is a possible explanation for impurity behavior in tokamak plasmas.
The importance of the sinus node as the cardiac pacemaker is well known. The aim of the present study was to investigate the microangioarchitecture at the level of the sinus node. Ten human adult hearts were injected with India ink in the initial segments of the coronary arteries. Pieces were drawn and diaphanized. The results of the study can be summarized: (1) the sinus node is rather an irregularly shaped structure, with peripheral strands intermingling with strands of the atrial myocardium; at this level two vascular patterns can be recognized: (a) the myocardial capillary networks that parallels the muscular bundles, and (b) the peripheral nodal networks built upon dichotomizing arterioles; (2) it seems that while the thick and large sinus node artery does not branch in the nodal tissue, the blood supply of this tissue is ensured by the peripheral nodal networks; (3) characteristically, in the periphery of the nodal tissue are largely present glomeruli made by capillaries with pericellular dispositions. The results strongly suggest that the nodal tissue is mainly supplied from its periphery and the sinus node artery is rather a scaffold than a supplier of that tissue.
The aim of the present study was to bring macroscopic and microscopic evidence on the left papillary muscles blood supply in human hearts. For the study were used human adult hearts from patients without clinically known cardiac ischemic history. Ten hearts were used for injecting China ink in the coronary arteries and other twenty hearts were dissected to evidence the characteristics of the main arteries of the left papillary muscles. Pieces - left papillary muscles - were drawn from the injected hearts and diaphanised. In all dissected hearts the left anterolateral papillary muscles were supplied by the left coronary system: anterior interventricular artery, second diagonal branch and left (obtuse) marginal artery. In 70% the left posteromedial papillary muscles were supplied by the right coronary system (posterior interventricular artery, left retroventricular artery) and in 30% by the left coronary system (circumflex artery). The left papillary muscles were supplied each by one or two main arteries that penetrated the muscles longitudinally. The ventricular wall attaching the papillary muscles was supplied by the subepicardial vessel sending the main arteries of the papillary muscles but also by neighbor subepicardial vessels distributed in that wall. The mural vessels were finer than the papillary muscles main arteries. Injected papillary muscles presented each with two systems of blood perfusion: one represented by segmental centers of arterial branching and distribution of the main arteries of the muscle and other represented by capillary extensions of the mural networks at that level. From the segmental branching centers were perfused the neighbor segments of the papillary muscles and intrasegmental anastomoses were recognized. The microvascular study of the left papillary muscles proves the usual overlapping of sources for segmental supply; this overlapping is reinforced by the high capillary density to ensure the vascularisation of the papillary muscles.
We derive the equation governing the asymptotic stationary states generated by decaying turbulence in two-dimensional plasma and planetary atmosphere. These fluids may be described by the Charney-Hasegawa-Mima equation and their relaxation states show a high degree of organization in vortical flows, similar to the Euler fluid. We develop a field-theoretical framework and show that these systems attain at stationarity the extremum of an energy functional corresponding to self-dual fields.
Using the method of positions of the complex singularities, we identify a class of new, exact solutions of the Flierl-Petviashvili equation. The solutions are periodic and have the geometry of the zonal flow. We examine the physical properties and find that the solution can reproduce data from experimental observations and numerical simulations.
The states of asymptotic relaxation of two-dimensional fluids and plasmas present a high degree of regularity and obedience to the sinh-Poisson equation. We find that by embedding the classical fluid description into a field-theoretical framework, the same equation appears as a manifestation of the self-duality.
The transport of collisional particles in stochastic magnetic fields is studied using the decorrelation trajectory method. The nonlinear effect of magnetic line trapping is considered together with particle collisions. The running diffusion coefficient is determined for arbitrary values of the statistical parameters of the stochastic magnetic field and of the collisional velocity. The effect of the magnetic line trapping is determined. New anomalous diffusion regimes are found.
The space-uniform amplitude envelope of the ion-temperature-gradient driven turbulence is unstable to small perturbations and evolves to nonuniform, solitonlike modulated profiles. The induced poloidal asymmetry of the transport fluxes can generate spontaneous poloidal spin-up of the tokamak plasma.
A systematic method is proposed for the determination of the statistical properties of a field consisting of a coherent structure interacting with turbulent linear waves. The explicit expression of the generating functional of the correlations is obtained, performing the functional integration on a neighborhood in the function space around the soliton. The results show that the non-Gaussian fluctuations observed in the plasma edge can be explained by the intermittent formation of nonlinear coherent structures.
Particle transport in two-dimensional divergence-free stochastic velocity fields with constant average is studied. Analytical expressions for the Lagrangian velocity correlation and for the time-dependent diffusion coefficients are obtained. They apply to stationary and homogeneous Gaussian velocity fields.
Proteins immunologically related to intermediate filaments have been identified in the sperm fibrous sheath but remain uncharacterized. We isolated and characterized a novel intermediate filament-related protein (FS39) localized to the fibrous sheath of the sperm tail. We used Northern blot analysis to establish that FS39 is transcribed predominantly in the testis of mice >18-20 days old. At this age, spermatogenesis has proceeded to the development of the first round haploid spermatids. In situ hybridization revealed that FS39 mRNA is first detectable in late step 3 spermatids, is at its highest level during steps 9 and 10, and diminishes in steps 13 and 14. Western blot analysis identified a single protein of 39 kDa in mouse and rat testis and epididymis, suggesting the protein is conserved in rodents. Indirect immunofluorescence localized FS39 to the fibrous sheath of the sperm tail, and in testis sections expression was detected from step 13 and step 14 spermatids onward, indicating FS39 is under translational control. Southern blot analysis showed FS39 to be a single copy gene, and hybridization to human genomic DNA suggested that a human equivalent gene is present. These results demonstrate that FS39 is transcribed in testis tissue during the haploid phase of spermatogenesis, is present in mature sperm, and codes for a novel 39-kDa intermediate filament-related protein of the fibrous sheath.
The issue discusses the case of a young male patient (35 years old), with bilateral retinal vein thrombosis. The onset of the ocular disease was eight years ago, in the left eye, with decreased visual acuity and complicated with neovascular glaucoma; with an adequate treatment, anatomical and functional evolution was good. A new retinal vein thrombosis, this time in the right eye, make us to concentrate our efforts on the etiology of the disease. Thus, we found a blood hyperviscosity syndrome, caused by a congenital deficiency of protein "S" and resistance at the activated protein "C", which may produce recurrent venous thrombosis.
The statistical properties of the turbulent field consisting of drift waves randomly interacting with a coherent structure are investigated. By using a nonperturbative method (analogous to the "semiclassical" approach in quantum mechanics), we calculate explicitly the generating functional of the correlations.
Magnesium (Mg) and calcium (Ca) concentrations were determined in the abdominal aorta of 28 patients who died by acute myocardial infarction (AMI), of 52 by ischemic heart disease (IHD) and of 26 subjects deceased by accidents or from causes other than atherosclerosis. Mg concentration in the fibrous and calcareous plaques, was significantly lower than in controls. The lowest Mg values were found in those who died by AMI. Calcium concentration, especially in the calcareous plaques, was enormous as against the controls. The four-seven times decreases of Mg/Ca ratio compared with the controls imply an alteration of the arterial wall cells. Magnesium deficit in the arterial wall probably plays a certain role in this process.
PURPOSE: Our purpose was to determine the ratio of protamine 1 to protamine 2 in human spermatozoa and relate it to in vitro fertilization rates (IVF) and standard semen parameters. METHODS: Couples who had been clinically diagnosed as having male-factor infertility and had undergone IVF treatment were grouped according to IVF rates and pregnancy outcome. Protamines were extracted and separated on acid urea polyacrylamide gels. The P1/P2 ratio correlation with semen parameters and IVF rates was investigated using nonparametric analysis. RESULTS: The P1/P2 ratio ranged from 0.55 to 1.29 in the control group of patients, who had fertilization rates > or = 50% and had achieved a pregnancy in one IVF cycle. Of the test patients with IVF < 50%, three (14%) had P1/P2 ratios outside the range exhibited by the control group and their sperm possessed large heads. CONCLUSIONS: P1/P2 ratios were statistically negatively correlated with IVF rates in the control group and with progressive motile sperm concentration in the test group. We do not think that altered P1/P2 ratios are the primary cause of reduced fertilization.
Spermatogenesis is a complex differentiation process in which diverse stage-specific proteins are co-ordinately expressed. Previously, subtractive hybridization and differential hybridization have been used in the identification of differentially expressed mRNAs. Although these techniques have been successfully used they require large amounts of RNA and are time consuming. To overcome these problems we have made use of the recently described mRNA differential display technique. The technique is an effective method which can identify and separate cDNAs that are differentially expressed between various cell-types. By comparing RNA from testes of mature (> 60 days old) and prepubertal (15-16 days old) mice we have identified nine differential cDNA bands expressed in mature testes. The differential display cDNA band DDC8 was used screen a testis cDNA library and the full length cDNA was isolated and sequenced. DDC8 cDNA is 1965 bp with an open reading frame of 533 amino acids which codes for a predicated hydrophilic protein with a calculated molecular weight of 62.04 kDa. RNase protection assays indicate DDC8 to be expressed during the postmeiotic stages of spermatogenesis and database searches using both nucleotide and amino acid sequences show DDC8 to have similarities to structural, cytoskeletal and associated proteins.
The incidence of infant methemoglobinemia reported in three counties of Transylvania, Romania, was evaluated from medical records, field visits, and interviews. Well water was the main source of nitrate for induction of acquired infant methemoglobinemia, which occurred post-breast-feeding when the infants consumed nitrate-contaminated water used in mixing formula. The average age of reported infants with methemoglobinemia was 39 days, supporting earlier observations that infants less than 4 months old are the most susceptible segment of the population. Vitamin C, rather than methylene blue, was the main medical intervention in the Transylvania region. The mean incidence rates of methemoglobinemia in the three counties (Saut-Mare, Mures, and Bistrita-Nasaud) ranged from 24 to 363 per 100,000 live births over a five-year period (1990-1994). These rates are below earlier reported incidence rates of up to 13% (13,000 per 100,000 live births). Three selected case reports are presented to describe hospital/clinic data, well-water data, and infant feeding practices. Recommendations for appropriate intervention programs are described. The significances of possible physical and neuropsychological effects on the development of children following methemoglobinemia are discussed and the need for further investigations is outlined.
A study was undertaken to evaluate the effect on nuclei number in human embryos cultured in vitro with primary cell lines of human Fallopian tube epithelium. The development of 203 surplus human embryos, cultured in standard culture medium (Earle's balanced salt solution + 15% A5) with or without ampullary cells, was observed from day 2 to day 5.5 post-insemination. The expanded blastocysts in both culture conditions were analysed for nuclei numbers per blastocyst. Embryos transferred to co-culture at the 2-cell stage had an average of 120.7 nuclei per blastocyst, which was significantly higher than the average of 62.9 nuclei per blastocyst (P = 0.023) for the embryos transferred to co-culture at the 4-cell stage. The embryos cultured in the control medium had an average of 42.1 nuclei per blastocyst, which was significantly less than co-cultured embryos (P = 0.04). Severely fragmented embryos (grades 3 and 4) did not show recovery in co-culture. Our results show that when human embryos are transferred to co-cultures before the 4-cell stage, the blastulation rate and the cell number per embryo increase significantly compared to the embryos cultured in standard culture medium. The possible effect of co-culture on embryonic gene expression is discussed.