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Biomedical subjects

R Strom

Publications and source records attributed to R Strom.

159 records · Page 9Linked to original sources
PubMedDate not supplied

A possible role of chromatin and tightly-bound chromatin proteins on enzyme-catalyzed methylation of DNA.

Upon extensive digestion with DNAaseI of placenta chromatin matrix, previously "stripped" from its loosely-bound components by high-salt extraction, a fraction is obtained that contains almost no endogenous DNA methylase activity but whose DNA, if still included in this whole fraction--not if it has been purified to a protein-free condition--is a good substrate for externally added enzyme. This chromatin matrix can even cause a significant stimulation of methylation of single-stranded Micrococcus luteus DNA by placental methylase. In vivo, this phenomenon may have possible counterparts in the existence of highly-methylated regions of chromatin loops that appear to be protected by tightly-bound protein components from digestion of the "stripped loops" with DNAaseI.

5-Methylcytosine↗
PubMedDate not supplied

Humoral immunity factors in cynomolgus macaques (Macaca fascicularis) serum: immunoglobulins and total light chains in nursing dams.

This study was aimed at the identification of variations in humoral immunity parameters during the lactation period in macaque females, a recognized model in reproductive physiology and pathology. The importance of such evaluation is evidenced in particular by the central role played by the maternally transferred immunity to the progeny. The trends of serum immunoglobulins and light chains were characterized by immunonephelometry during the 6-months of lactation. The levels attained by nursing females were evaluated against a control group. The main modifications induced by lactation were in the IgM class, whose levels remained constantly lower than in the control group; the other Igs, even if showing different trends, returned to levels comparable to the control group by the end of the sixth month. Light chains quantification evidenced a significant decrease in Kappa levels; Lambda chains showed a similar trend. The variation of the Kappa/Lambda ratio was therefore minimal.

Analysis of Variance↗
PubMedDate not supplied

Strengths and needs of black grandparents.

This study was conducted to identify ethnic differences in grandparent performance and effectiveness so that an educational program called Becoming A Better Grandparent could be adapted to maximize its relevance for Black families. MANOVA procedures were used to compare perceptions of 204 Anglo grandparents and 204 Black grandparents as well as 175 Anglo and 295 Black grandchildren. Black grandparents perceived themselves more favorably than did Anglos on every subscale of the Grandparent Strengths and Needs Inventory. Black grandchildren assigned grandparents significantly more favorable ratings for teaching and overall success, whereas Anglo grandchildren assigned their grandparents higher scores for coping with difficulty, managing frustration, and meeting information needs. Analyses of grandparent responses revealed significant main effects for age of grandparent, age of grandchild, time spent together, and geographical proximity. Grandchildren responses yielded significant main effects for age of grandchild and time spent together. Findings showed interaction effects for ethnicity by age of grandparent, ethnicity by age of grandchild, and ethnicity by distance. Implications for modifying the program to fit Black grandparents were identified.

Aged↗
PubMedDate not supplied

Natural killer cells and gamma/delta T cells in synovial fluid and in peripheral blood of patients with psoriatic arthritis.

OBJECTIVE: NK surface markers and gamma/delta TCR antigen are involved in non-MHC-restricted cytotoxicity, which represents a major effector mechanism of the cell-mediated immune response. We evaluated in PsA patients SF and PB lymphocytes expressing these cellular subsets in order to obtain information on the possible role played by them in the disease. METHODS: We studied 29 PsA and 27 RA patients, as well as 27 healthy controls. In 17 PsA and 16 RA patients with knee joint effusion, analysis of SF was performed. SF and PB lymphocyte analysis was performed by direct dual immunofluorescence flow cytomettry using anti-CD3, anti-CD4, anti-CD8, anti-CD19, anti-TCR-gamma/delta-1 and anti-CD16 and anti-CD56 monoclonal antibodies. RESULTS: PsA and RA patients had, with respect to controls, lower values (both as percentages and in absolute numbers) of PB T cells expressing gamma/delta TCR. SF Iymphocytes of PsA and RA patients were characterised, as compared to PB lymphocytes, by lower numbers (both in absolute numbers and in relative terms) of NK and NK-T cells. Considering the absolute numbers of the various lymphocyte subsets, a strong correlation was found in PsA SF between gamma/delta T cells and NK (p < 0.0007) or NK-T cells (p < 0.0003), as well as between NK and NK-T cells (p < 0.0019). There was instead no statistically significant correlation among the different SF or PB lymphocytes and the most relevant clinical or serological parameters. CONCLUSION: This study, analyzing the impairment of different subsets involved in non-MHC-restricted cytotoxicity, suggests that this component of the cell-mediated immune response seems to play a pivotal role in the development of PsA.

Adolescent↗
PubMedDate not supplied

The inactivation of beta-lactamase I from B. Cereus by dicloxacillin: effect of buffer composition on the kinetic characteristics of the modified enzyme.

Buffer composition affects the pattern of inactivation of B. cereus beta-lactamase I by dicloxacillin. At pH 7.0, in the presence of phosphate ions, dicloxacillin appears to cause essentially an irreversible inactivation of the catalytic site of the enzyme, while in a tris-cacodylate buffer the inactivation process appears to affect essentially the substrate-binding site. Buffer ions act presumably by interacting themselves with either the catalytic or the substrate-binding site of the enzyme, thus modifying the affinity of these sites for the halogenated isoxazolyl-penicillins.

Bacillus cereus↗
PubMedDate not supplied

Do intermolecular association phenomena occur in B. cereus beta-lactamase I?

Although at fixed enzyme concentration the hydrolysis of cephaloridine by B. cereus beta-lactamase I followed apparently classical Michaelis-Menten steady-state kinetics, the values of kcat and of Km depended linearly, in the absence of added non-enzymatic proteins, on the absolute enzyme concentration. In the presence of gelatin, this dependence was abolished; under these conditions, however, the pseudo-first order kinetic rate constants of inactivation by Zn2+ ions exhibited a direct dependence on enzyme concentration and an inverse one on Zn2+ ions concentration. These results can be interpreted as indicating that intermolecular association phenomena play a role in determining the catalytic properties of the enzyme.

Bacillus cereus↗
PubMedDate not supplied

Pentose phosphate pathway alterations in multi-drug resistant leukemic T-cells: 31P NMR and enzymatic studies.

31P NMR studies were carried out on the parental drug-sensitive human T-lymphoblastoid cell line CCRI-CEM (CEM) and its multi-drug-resistant (MDR) CEM-VBL100 variants, to assess the role of the pentose phosphate (PP) in MDR expression. CEM and CEM-VBL100 were incubated in the presence of 2-deoxyglucose, as recently proposed by our group (Clin. Chim. Acta 208: 39, 1992). Accumulation of 2-deoxyglucose 6-phosphate was much lower in the drug-resistant than in sensitive cells, indicating PP shunt activation in the MDR variants. This result was confirmed by enzymatic analyses, which demonstrated that, with respect to the parental line, the MDR variant was characterized by a) unaltered hexokinase activity; b) higher glucose 6-phosphate dehydrogenase activity; c) increased levels of reduced glutathione and marked increase of glutathione peroxidase activity after cell exposure to an oxidizing agent (tert-butylhydroperoxide). These results support the view that cell detoxification mechanisms mediated by the pentose phosphate pathway may contribute to the expression of MDR in tumours.

ATP Binding Cassette Transporter, Subfamily B, Mem↗