Biomedical subjects

R Strom

Publications and source records attributed to R Strom.

At least 37 records · Page 2Linked to original sources

PubMed1997

Expression of receptors for native and chemically modified low-density lipoproteins in brain microvessels.

Despite the importance of cholesterol metabolism in the central nervous system, only relatively few studies have dealt with the cerebral uptake and transport of lipids into the brain compartment. These functions are mediated by the endothelium of brain microvessels, which forms the anatomical basis of the blood-brain barrier. By a reverse transcriptase PCR study of messenger RNA expression we could show, in bovine brain microvessels, the presence of transcripts of native low-density lipoprotein receptor and of both type I and II scavenger receptors. Brain microvessels therefore appear to play an active role in the uptake of native and modified low-density lipoproteins.

Animals↗

PubMed1997

Developmental study of ultrastructural and biochemical changes in isolated chick brain microvessels.

The morphology of the endothelial junctions, the expression of the alkaline phosphatase (ALKP) and gamma-glutamyltranspeptidase (GGT) activities, and the transport systems for neutral amino acids (NAA) and for d-glucose were studied in parallel in isolated microvessels from the brains of 9-, 12-, and 21-day chick embryos and 30-day chickens using freeze-fracturing and biochemical techniques. In the 9-day embryos, the endothelium junctional plasma membranes show alignments of discrete intramembrane particles (Imps) on the replica P-faces. In the 12-day embryos, the junctional membranes show short fibrils of loosely interconnected fused Imps. In the 21-day embryos, the junction is characterized by simple networks, and in the 30-day chickens, by very dense meshworks of continuous, fibrillary strands. In early embryonic life, the ALKP activity is expressed at high levels, more markedly in the microvessels than in the whole brain. ALKP progressively declines in later embryos and even more in adulthood, when the activity is fivefold higher in the microvessels than in the whole brain. No GGT activity is expressed in either embryonic or adult microvessels. The transport systems for NAA and for d-glucose are most active in 12-day embryonic microvessels, and progressively less expressed by the 21st day and in the adult. The results taken as a whole suggest a close relationship between the morphological and the metabolic maturation of the endothelial barrier of cerebral vessels.

Alkaline Phosphatase↗

PubMed1997

Contribution of factor VII genotype to activated FVII levels. Differences in genotype frequencies between northern and southern European populations.

The relationship between coagulation factor VII (FVII) levels in plasma and FVII genotypes, determined by three polymorphisms (5'F7, IVS7, and 353R/Q), were studied in 500 control subjects enrolled in European multicenter study. The selection of particular FVII genotypes and the analysis of variance clearly indicated the independent contribution of a single 5'F7 insertion (A2) or 353Q (M2) allele to lowering plasma levels of activated FVII (FVIIa) (by a mean 25%). The M2 allele alone was found to make a major contribution to the genetically determined component of the FVIIa levels. Genotypes associated with low FVII levels were significantly rarer in the northern part of Europe (Oslo) than in the southern part (Rome, Murcia). The contribution made by the FVII genotype to the total variance of FVIIa levels was higher (30%) than that made to either FVII activity (25%) or FVII antigen (12%). Subjects with different FVII genotypes showed up to fivefold differences in mean FVIIa values, thus allowing attribution of a substantial part of the considerable interindividual variation to genetic variation, which may be of assistance in the interpretation of FVIIa levels on an individual basis. When FVII levels were adjusted by age and by triglyceride levels, the contribution of FVII genotypes to the FVII phenotypic variance was virtually unchanged. Taken together, these data indicate that in healthy control subjects the FVII genotype is a major predictor of plasma FVIIa levels and would support further study on the role of FVII genetic components in the development of cardiovascular disease.

Adult↗

PubMed1997

Building a theory of grandparent development.

A theory of grandparent development is described that includes the formulation of assumptions, goals for guiding instruction, curriculum design, and a measurement tool to assess learning needs and evaluate the effects of educational intervention. Cultural considerations are illustrated by a three generational study of African-American (n = 777), Caucasian (n = 1086), and Hispanic (n = 672) subjects who were administered the Grandparent Strengths and Needs Inventory. Perceptions of each generation about the attitudes and behaviors of grandparents were examined with multivariate analysis of variance and post-hoc comparisons to analyze the scores, confirm results, and facilitate interpretation of findings. Results showed significant differences between generations and within cultures. Each generation identified elements of grandparent success as well as issues that deserve consideration in building educational programs.

Attitude↗

PubMed1996

AZT-induced hypermethylation of human thymidine kinase gene in the absence of total DNA hypermethylation.

Genome-wide DNA hypermethylation induced by 3'-azido-3'-deoxythymidine (AZT) has been suggested to be involved in the development of AZT resistance. We used a CD4 T-lymphoblastoid CEM line and its AZT-resistant MT500 variant with reduced thymidine kinase activity. Evaluation of total DNA methylation, after AZT treatment, failed to show an increase in the 5-methylcytosine level in both parental and AZT-resistant cells. The effect was instead observed at a more specific gene level, on the three HpaII sites present in exon 1 of the human thymidine kinase gene. These results suggest that AZT treatment can induce site-specific hypermethylation, even in the absence of a more general DNA hypermethylating effect.

5-Methylcytosine↗

PubMed1996

H1-H1 cross-linking efficiency depends on genomic DNA methylation.

Oligonucleosomal DNA preparations from condensed-inactive chromatin were examined, before and after artificial methylation by bacterial SssI methylase, for their ability to allow cooperative H1-H1 interactions under conditions of different ionic strength. Our results support the conclusion that, within the highly methylated genomic DNA, there are some CpG's whose unmethylated state is critical for chromatin folding. Circular dichroism spectra indicate that artificial overmethylation of native oligonucleosomal DNA reduces its efficiency in inducing an ordered conformation of H1 histone. Temperature melting profiles confirm on the other hand that the native and the artificially overmethylated forms of oligonucleosomal DNA are both able to bind H1 histone.

Circular Dichroism↗

PubMed1996

Different effects of histone H1 on de novo DNA methylation in vitro depend on both the DNA base composition and the DNA methyltransferase.

We have characterized the inhibition exerted by histone H1 on the activity of human placenta DNA (cytosine-5-)-methyltransferase. Our experiments demonstrate that the extent of inhibition depends on the DNA base composition, AT-rich substrates being more severely affected than GC-rich substrates and CpG-rich islands. With bacterial SssI methylase, the effect is completely reversed since its activity on AT-rich substrates undergoes a 4-5-fold stimulation upon the addition of H1. Poly(L-lysine) mimicks H1 effects, suggesting an essential role of lysine residues in both the inhibitory and stimulatory effects of H1. By comparison of the different behaviors of the two enzymes, the inhibitory effect over the eukaryotic enzyme might be accounted for by hypothesizing a competition between minor groove-binding motifs (SPKK-like) present in placenta methylase as well as in histone H1.

Base Composition↗

PubMed1996

Specific inhibitory effect of H1e histone somatic variant on in vitro DNA-methylation process.

H1e and H1c histone variants were purified from mouse L929 fibroblasts using a reverse phase HPLC, and their effect on in vitro DNA methylation was investigated, together with their ability to bind unmethylated or methylated CpG-rich 44bp oligonucleotides. In a "physiological" range of H1:DNA ratios only H1e, at variance from H1c, was found to cause a marked inhibition of in vitro enzymic DNA methylation. It was also shown that both variants have a similar affinity in binding a methylated CpG-rich oligonucleotide, but that the binding to the same oligonucleotide in the unmethylated form occurs preferentially with H1e rather than with H1c. H1e is therefore likely to be directly involved in maintaining CpG-rich sequences in the unmethylated state.

Animals↗

PubMed1996

Serum kappa and lambda light immunoglobulin chains in cynomolgus macaques (Macaca fascicularis) during the first twenty months of age.

Growth is coupled to physiological modifications of the immune system which reaches the functional capabilities according to age-related milestones. Few data are available on the circulating immunoglobulin levels and no data exist on total immunoglobulin light chains in infant macaques. Therefore we studied by a nephelometric assay, the age-dependent variations of kappa and lambda serum light chains in the experimental animal model Macaca fascicularis during the first 20 months of age. Both kappa and lambda showed a marked increase in their concentrations during the first 7-8 months of life. Infants' light chain levels were anyhow significantly lower than those of the nursing dams and of the control group, never attaining, even at the 20th month, the same concentration as the adult, although the value of the kappa/lambda ratio was apparently the same.

Age Factors↗

PubMed1996

Erythrocyte glutathione determination in the diagnosis of glucose-6-phosphate dehydrogenase deficiency.

The levels of reduced glutathione in severe glucose-6-phosphate dehydrogenase deficient red blood cells, were found, when assayed immediately after blood withdrawing, almost equal to those of normal human erythrocytes. On the contrary, if the blood samples were stored at 4 degrees C for 4 days (or more) either as whole blood or as washed erythrocytes with or without glucose, the glutathione concentration of the enzyme-deficient cells decreased to half the initial value. After a mild t-butylhydroperoxide (t-BHP) treatment, only glucose-6-phosphate dehydrogenase deficient red cells exhibited a drastic decrease of glutathione, the normal ones being almost unaffected. If t-BHP-treated erythrocytes were incubated in the presence of glucose or of oxidized glutathione, a full recovery of the inital glutathione concentration was detected only in normal samples. Glucose could not be replaced by any other sugar. When the oxidative stress was induced by addition of methylene blue (MB), the behaviour was similar but less marked, it was however impossible, in this case, to restore the normal glutathione levels, through a subsequent incubation of the MB-treated erythrocytes with oxidized glutathione. This discrepancy can be explained by the finding that a marked inhibition of glutathione reductase was observed in MB-treated erythrocytes, while t-BHP exposure had no direct effect on this enzyme.

Erythrocytes↗

PubMed1996

Grandparents in Taiwan: a three-generational study.

Grandparents in the Republic of China want to remain influential, but social policy has not provided them with education to fulfill their changing role. The performance of grandparents was examined to determine suitable content for an intervention program. A sample of 751 non-consanguineous participants from urban and rural Taiwan included 234 grandparents, 241 parents, and 276 grandchildren. Each generation was administered a separate version of the Grandparent Strengths and Needs Inventory that was translated into Mandarin. Respondents identified favorable qualities of grandparents as well as aspects of their relationships in which growth was necessary. Multivariate analysis of variance, univariate analysis of variance, Scheffé and t-tests were used to analyze scores, confirm results, and facilitate interpretation. All three generations described aspects of grandparent success and specific realms of learning they should acquire to become more effective. Significant main effects that influenced responses about grandparent performance were generation, gender of grandchild, age of grandchild, frequency of grandchild care by grandparent, generations living together, and amount of time grandparent and grandchild spent together. Considerations were recommended to improve behavior of grandparents and guide the development of educational programs for them.

Aged↗

PubMed1996

Black grandparents: curriculum development.

The performance of Black grandparents was examined to determine the most suitable content for an educational program intended to assist them in their role. A sample of 626 non-consanguineous subjects included 204 grandparents, 128 parents, and 294 grandchildren. Each generation group completed a separate version of the Grandparent Strengths and Needs Inventory to identify the favorable qualities of grandparents and aspects of their relationships in which further growth was necessary. A combination of multivariate analysis of variance procedures, univariate analysis of variance tests, and t-tests were used to analyze scores, confirm results, and assist with interpretation of data. All groups described aspects of grandparents success and made known specific realms of learning that grandparents should acquire in order to become more effective. Analysis of the responses revealed significant main effects for generation, gender of grandchild, age of grandchild, and amount of time that grandparent and grandchild spent together. Considerations were identified for improving grandparent influence and guiding the development of grandparent education programs.

Adolescent↗

PubMed1996

Simultaneous myogenin expression and overall DNA hypomethylation promote in vitro myoblast differentiation.

Two clones of the L5 myoblast line (M6 and the fusion-defective M12) were examined for the expression of myogenin, one of the regulatory genes involved in the regulation of differentiation to myofibers after treatment with 3-deazaadenosine, a metabolic inhibitor of methyl transfer reactions. Cultures treated with 3-deazaadenosine showed, using Northern blot hybridization, a conspicuous increase in myogenin expression, which in clone M6 correlated to the extent of cell differentiation under fusing conditions but was evident also in growth medium, although the drug was unable to start the myogenic program. We also tested the extent of total DNA methylation to verify whether the activation of the regulatory cascade could be correlated to the decrease of the overall number of 5-methylcytosines present in the genome. The results show that the loss of 5-methylcytosine from newly synthesized DNA, but not from preexisting DNA, is evident in fusing conditions and enhanced by 3-deazaadenosine. It appears that there is a positive correlation between the passive demethylation of newly synthesized DNA, the activation of the myogenin gene by demethylation, and the differentiation of myoblasts. However, in fusing conditions, the defective clone M12, although it is able to express myogenin and its DNA is hypomethylated, fuses only in the presence of 3-deazaadenosine, suggesting some alternative way of induction.

Animals↗

PubMed1995

DNA binding and methyl transfer catalysed by mouse DNA methyltransferase.

By using a purified fraction of mouse DNA methyltransferase we have shown, by gel-retardation analysis, that the enzyme forms a low-affinity complex preferentially with hemimethylated DNA; the complexes formed with unmethylated or with fully methylated DNA are of even lower affinity, and only very weak interaction occurs with DNA lacking CG dinucleotides. Interaction is inhibited by N-ethylmaleimide. Methyl transfer from S-adenosyl-methionine is associated with the release of the fully methylated product from the complex. Complexes formed with the intact enzyme are extremely large, but limited trypsin treatment allows a major complex to enter the gel. DNA binding is not inhibited by this limited proteolysis of the native enzyme.

Animals↗

PubMed1995

Does hypomethylation of linker DNA play a role in chromatin condensation.

The inhibitory effect that H1 histone exerts on the in vitro DNA methylation process, catalysed by mammalian DNA methyltransferase, together with the relative hypomethylation of linker DNA in eukaryotic cells chromatin, suggest that this hypomethylated state of linker DNA can be of importance in allowing or regulating H1-dependent chromatin condensation. In native oligonucleosomes (olnu), i.e., in chromatin fragments consisting of 5-20 nucleosomes each, there was a correlation between the effects of H1 on the DNA ellipticity at 280 nm and the in vitro assayed methyl-accepting ability. The same was true in H1-depleted or in H1-reconstituted preparations. Artificial methylation caused olnu DNA to lose its ability to allow cooperative H1-H1 interactions under ionic strength conditions similar to those known to affect the transition of the 10-nm filament to the 30-nm chromatin fiber. These results suggest that hypomethylation of linker DNA plays a role in the H1-H1 interactions that are needed for solenoid condensation.

Animals↗

PubMed1995

Specific variants of H1 histone regulate CpG methylation in eukaryotic DNA.

Upon HPLC fractionation of human placenta or calf thymus H1 histone preparations, only some fractions enriched in the H1e-c variants were able to exert a severe inhibition on in vitro enzymatic DNA methylation. These fractions, though similar to the other variants in interacting with genomic DNA, were also the only ones which could bind CpG-rich ds-oligodeoxyribonucleotides (oligos). Both the 6-CpG ds-oligo and the DNA purified from chromatin fractions enriched in 'CpG islands' were good competitors for the binding of H1e-c to the 6meCpG ds-oligo. This ability to bind any DNA sequence and to suppress the enzymatic methylation in any sequence containing CpG dinucleotides suggests, for these particular H1 variants, a possible role in maintaining CpG island DNA and linker DNA at low methylation levels.

Animals↗

PubMed1995

Binding of histone H1e-c variants to CpG-rich DNA correlates with the inhibitory effect on enzymic DNA methylation.

Within the H1 histone family, only some fractions enriched in the H1e-c variants are effective in causing a marked inhibition, in vitro, of enzymic DNA methylation and, in gel retardation and Southwestern blot experiments, in binding double-stranded (ds) CpG-rich oligonucleotides. Both the 6-CpG ds-oligonucleotide and the DNA purified from chromatin fractions enriched in 'CpG islands' are good competitors for the binding of H1e-c to 6-meCpG ds-oligonucleotide. Because of their ability to bind any DNA sequence and to suppress the enzymic methylation in any sequence containing CpG dinucleotides, these particular H1 variants could play some role in maintaining linker DNA at low methylation levels and even in preserving the unmethylated state of the CpG-rich islands which characterize the promoter regions of housekeeping genes.

Animals↗

PubMed1995

Grandparents in Japan: a three-generational study.

Grandparents in Japan believe that their status in the family is eroding. They want to be influential but social policy has not included education for their changing role. The purpose of this study was to identify strengths and needs of Japanese grandparents as perceived by three generations. Each generation completed a separate version of the Grandparent Strengths and Needs Inventory. Multivariate analysis of variance procedures were used to compare perceptions of 239 grandparents, 266 parents, and 274 school-age grandchildren from cities and small towns. Grandparents reported more satisfaction, greater success, and more extensive involvement in teaching than was observed by parents and grandchildren. Grandparents experienced greater difficulty, more frustration, and felt less informed to carry out their role than was reported by parents and grandchildren. Significant main effects that influenced responses about grandparent performance were generation, gender of grandchild, age of grandchild, generations living together, frequency of grandchild care by grandparent, and amount of time they spent together. Considerations were identified to improve grandparent behavior and guide the development of educational programs for them.

Aged↗