Biomedical subjects
Publications and source records attributed to M Vlad.
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 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.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effect of Cuprofilin, a newly synthesized C.(II)-chlorophyll complex, was assessed in rats with experimental atherosclerosis. The study was focused on changes in serum cholesterol, lipids, and triglycerides concentration as well as on serum and abdominal aorta Cu and Zn values. It has been ascertained that after 90 d in animals fed a rich lipid diet there was a statistically significant increase in serum cholesterol, triglycerides, and lipid concentration (p < 0.01). A significant augmentation of serum Cu values (p < 0.01) accompanied by a marked lowering of the same element in abdominal aorta (p < 0.01) was also found, as compared to the results registered in the control group. However, Cuprofilin, administered for 90 d in the group of animals with experimental atherosclerosis, significantly decreased the serum cholesterol, triglycerides, and serum lipid values (p < 0.01), increased copper content in aortic tissue (p < 0.01) and lowered serum copper concentration (p < 0.01) as compared to the untreated group. Moreover, in the aorta of administered animals the lipid infiltration has been demonstrated to be significantly diminished vs the untreated group.
Explore the source record for details and available documents.
The Cu, Zn, Cr, Fe, and Ni concentrations from the atherosclerotic plaques in the abdominal aorta obtained from 40 patients who died of coronary heart disease (CHD) were measured. In 32 of them the clinical and anatomical diagnosis was ischemic heart disease (IHD) and in 8 of them it was acute myocardial infarction (AMI). Concomitant determinations of the concentrations of the above trace elements were determined in 16 normal aortas from subjects who died in accidents or from causes other than atherosclerosis (C). The determinations were done by means of a Perkin-Elmer atomic absorption spectrophotometer, Model 300. The results are expressed in mg/kg of dried tissue. The Cu, Zn, and Cr concentrations were significantly lower (p < 0.01) in the atherosclerotic plaques of abdominal aorta of the deceased patients with IHD and AMI than in the control group. Iron had the tendency to rise but not significantly. The nickel level in the atherosclerotic plaques from abdominal aorta did not change significantly as compared to the controls. We attribute the low values of copper in the atherosclerotic aortic tissue in IHD and AMI to a shift of copper from aortic tissue into the blood. At present, there is no explanation for the low concentration of zinc and chromium in atherosclerotic aortic tissue.
Serum copper concentration increases significantly (p < 0.01) in rats with experimental atherosclerosis compared to a control group. The serum zinc, the zinc, and copper concentration in abdominal aorta and in liver decreases significantly (p < 0.05) compared to the control group. Administration of copper sulfate for 100 d in these animals induces a significant increase of serum copper (p < 0.01), decrease of serum cholesterol (p < 0.05) and increase of liver copper concentration as compared with the group fed only a high cholesterol diet. In the aorta of these animals the copper concentration increases and edema and lipid infiltration are considerably less than in the group of animals fed only a high lipid diet.
Explore the source record for details and available documents.
Observed differences in the sizes of lampbrush nucleolus organizers in Plethodon cinereus have been shown by in situ hybridization to reflect true molecular differences in the numbers of ribosomal cistrons located at these organizers. Likewise, from in situ hybridization experiments on lampbrush and spermatocyte chromosomes it has been shown that animals may be, and indeed usually are, heterozygous with respect to the numbers of ribosomal cistrons on each half of the nucleolus bivalent. Filter hybridizations carried out on 33 males from a New Jersey population and 20 males from a Connecticut population have shown a 7.5-fold range in the numbers of ribosomal cistrons per diploid cell in the New Jersey population, and a 2.5-fold range in the Connecticut population. In view of the general heterozygosity of nucleolus organizers in these animals, the actual range in nucleolus organizer sizes in the New Jersey population is estimated to be at least 15-fold.
The proportion of the genome that is complementary to 18 and 28 s has been determined for 12 species of amphibians. The group of species chosen for the experiment includes 5 related species belonging to the same genus (Plethodon) as well as species belonging to distant taxonomic groups whose C-values range from 3 to 62 pg. Hybridization of rRNA (18 S + 28 S) to whole chromosomal DNA to saturation level indicates that the proportion of rDNA decreases with increasing DNA content. The results presented in this paper do not support the hypothesis of Nardelli, Amaldi & Lava-Sanchez that the number of ribosomal cistrons in various amphibians can always be expressed as a power of 2.
The amplification of ribosomal genes has been studied in oocytes from Salmo irideus. In situ nucleic acid hybridization showed that the synthesis of nucleolar DNA begins in oogonium and proceeds slowly through leptotene and zygotene when a small amount of extrachromosomal nucleolar DNA is produced. In early pachytene there is a rapid build-up of nucleolar DNA demonstrable by rapid incorporation of tritiated thymidine. Synthesis stops completely in early diplotene when nucleolar DNA becomes dispersed over the inner surface of the nuclear envelope in the form of small Feulgen-positive granules. Photometric measurements of Feulgen stained nuclei showed that the final amount of amplified nucleolar DNA synthesized in each oocyte is approximately 20 mug. The amplified DNA does not form a heterochromatic mass. The buoyant density of the amplified nucleolar DNA calculated from analytical centrifuge tracings in relation to DNA from Micrococcus luteus (rho = 1.731 g cm-3) is 1.715 g cm-3 and corresponds to a G+C content of 57%. There are indications that the buoyant density of the somatic nucleolar DNA is lower than that of amplified nucleolar DNA. Similarities and differences between ribosomal gene amplifications in oocytes of Salmo irideus and the corresponding process in Xenopus are discussed.