S-adenosylhomocysteine hydrolase activity in erythrocytes from HIV-infected patients.
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AIDS-Related Complex↗
Biomedical subjects
R Strom
Publications and source records attributed to R Strom.
Membrane alterations in G6PD- and PK-deficient erythrocytes exposed to oxidizing agents.
After in vitro treatment of normal, glucose-6-phosphate dehydrogenase-deficient or pyruvate kinase-deficient human erythrocytes with three different oxidizing agents, the extent of lipid peroxidative degradation and the alterations of membrane proteins were evaluated. Exposure to tert-butylhydroperoxide induced, most markedly in G6PD- and PK-deficient erythrocytes, a reduction of protein bands 1, 2, 2.1, 3, 4.1, 4.2, and 5, with the appearance of high-molecular-weight aggregates and of "new" polypeptide components in the 29- to 23-kDa region and with a marked increase of membrane-bound globin. Malonyldialdehyde production was highest in G6PD-deficient cells and relatively low in PK-deficient ones. Methylene blue, which had similar but less relevant effects on lipid peroxidation, in G6PD-deficient erythrocytes caused a conspicuous appearance of high-molecular-weight aggregates and a simultaneous relevant decrease of bands 1 and 2 and of membrane-bound globin; it brought about an almost opposite effect in PK-deficient red cells. Acetylphenylhydrazine, which under our conditions appeared the mildest agent, failed, in normal and PK-deficient erythrocytes, to increase malonyldialdehyde production or to alter membrane proteins, whereas it caused, in G6PD-deficient cells, a slight decrease of bands 1 and 2, a more pronounced decrease of band 3, and a marked increase of bands 4.5 and 4.9.
Erythrocyte Membrane↗
Some molecular properties of Citrobacter diversus beta-lactamases.
Citrobacter diversus ULA-27, a clinical isolate showing a broad resistance pattern towards both penicillins and cephalosporins, produces chromosome encoded beta-lactamases. However, the strain remains susceptible to some cephamycins, imipenem, ceftazidime and tetracyclines. Crude bacterial extracts analyzed by isoelectric focusing on polyacrylamide gels, revealed the presence of two main isoforms and some "satellite" bands focusing in the pH range 5.7-7.2. The isoform showing the pIs 6.8 and 6.2 were characterized as class "A" beta-lactamases (according to Ambler's classification) based on the rate of interaction of beta-iodopenicillanate and the amino acid sequence around the active site serine. The substrate specificity of the Citrobacter diversus beta-lactamases explains the resistance phenomenon of this bacterium to penicillins and cephalosporins.
Cephamycins↗
S-adenosylhomocysteine hydrolase and adenosine deaminase activities in human red cell ageing.
The enzyme activities of S-adenosylhomocysteine hydrolase, adenosine deaminase and pyruvate kinase were determined in normal human erythrocytes subpopulations of different ages separated by centrifugation on a discontinuous Percoll:NaCl density gradient. The levels of S-adenosylhomocysteine hydrolase activity were found to undergo a sharp decrease with red cell ageing. Adenosine deaminase activities were, however, less critically dependent on erythrocyte age.
Adenosine Deaminase↗
Raising expectations for grandparents: a three generational study.
Previous research resulted in the nation's first curriculum for grandparents. To determine the program benefits, 210 experimental subjects received instruction. Each of these persons chose one son or daughter and one grandchild to help evaluate changes in grandparent attitudes and behavior. All three generations completed separate versions of the Grandparent Strengths and Needs Inventory prior to the classes, at the end of intervention, and three months later. Posttesting of grandparents revealed significant improvement. These gains were corroborated by parents and grandchildren. Multivariate analyses identified the impact of eleven independent variables on grandparent performance. A control group of 185 subjects made no improvement.
Adolescent↗
In vitro methylation of CpG-rich islands.
CpG islands are distinguishable from the bulk of vertebrate DNA for being unmethylated and CpG-rich. Since CpG doublets are the specific target of eukaryotic DNA methyltransferases, CpG-rich sequences might be expected to be good methyl-accepting substrates in vitro, despite their unmethylated in vivo condition. This was tested using a partially purified DNA-methyltransferase from human placenta and several cloned CpG-rich or CpG-depleted sequences. The efficiency of methylation was found to be proportional to the CpG content for CpG-depleted regions, which are representative of the bulk genome. However, methylation was much less efficient for CpG frequencies higher than 1 in 12 nucleotides, reaching only 60% of the expected level. That suggests that the close CpG spacing typical of CpG-islands somehow inhibits mammalian DNA methyltransferase. The implications of these findings on the in vivo pattern of DNA methylation are discussed.
Base Sequence↗
Use of bispecific hybrid antibodies for the development of a homogeneous enzyme immunoassay.
Hybrid bispecific monoclonal antibodies reacting with carcinoembryonal antigen (CEA) and with the E. coli enzyme beta-galactosidase (GZ) were produced by fusion of hybridomas or chemical linkage of half-antibodies. Since the original anti-GZ antibody used in these experiments was capable of protecting GZ from thermal denaturation, it was possible, by hybridizing it with two different non-competitive anti-CEA antibodies, to design a homogeneous enzyme immunoassay for quantitation of CEA. In fact, a mathematical analysis of the reaction indicates that, under appropriate concentrations of the reactants, circular complexes can be formed which contain the two hybrid antibodies, the GZ enzyme and the CEA antigen. The stability of these complexes can be expected to be substantially greater than that of the more labile CEA-free GZ-antibody complexes, prompting a significant increase in the amount of enzyme molecules which are bound to antibody and are consequently protected from thermal denaturation. These expectations were supported by experimental results: under appropriate conditions, heat-resistant enzyme activity was indeed proportional to concentration of CEA in the range up to 75 ng/ml. As predicted by theory, however, in the presence of excess CEA - in fact at CEA concentrations which are higher than those of possible clinical relevance - circular complexes tended to open up, leading to a marked prozone effect.
Antibodies, Monoclonal↗
Chemiluminescent assays in the study of purine metabolism.
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Gout↗
Somatostatin infused during acute pancreatitis retains its biological activity.
Somatostatin (SST) is used in the treatment of acute pancreatitis (AP) to inhibit pancreatic exocrine secretion, which represents one of the goals of medical treatment in this disease. Its therapeutic efficacy, however, is poor. One hypothesis, which has not yet been investigated, is that i.v. SST might be broken down by blood proteolytic enzymes. In order to evaluate the structural integrity and biological activity of infused SST, somatostatin-like immunoreactivity (SLI) and levels of pancreatic enzymes were monitored in the blood stream during the infusion of SST-14 (3,5 micrograms/kg/h for 48 h) in eight patients with severe acute pancreatitis. SLI was measured by both radioimmunoassay (RIA) and high-pressure liquid chromatography (HPLC). The results indicate that SLI levels increase promptly after the beginning of infusion, with a slower increase between 6 and 36 h, and a rapid increase again at 48 h. HPLC analysis shows a single peak of SLI with the same retention time as standard SST-14. Total amylase, lipase, and trypsinogen significantly decreased compared with pretreatment values (48, 63.1, and 77.4%, respectively) after 24 h of SST infusion, while a decrease in elastase 1 (62.6%) was observed later at 48 h. These results indicate that in severe AP, somatostatin recovered in plasma retains its biological activity: it inhibits pancreatic circulating enzymes, an action not influenced by breakdown of the peptide, as demonstrated by HPLC of the SLI measured in plasma.
Acute Disease↗
Evaluating the success of deaf parents.
Nineteen parent-child pairs completed the Parental Strengths and Needs Inventory (PSNI) and were interviewed about their relationships. Parent and child scores on the PSNI were above average, with parents expressing high interest in information about childrearing. Interviews revealed issues specific to deaf parents, such as using children as interpreters and frustration when children had poor sign language skills. Children with good sign language skills said they were generally willing to interpret for their parents, except during conflict situations. Children also reported advantages to having deaf parents: they enjoyed being bilingual and their parents tolerated noise and loud music. Study results underscore the importance of triangulation strategies in cross-cultural research.
Adolescent↗
Grandparents and learning.
The educational needs of grandparents have been overlooked. They deserve access to a curriculum that can help them adjust to their changing role and illustrate how to build satisfying family relationships. In order to identify appropriate topics and instructional procedures for grandparent education, weekly meetings were held for a semester with 400 grandmothers and grandfathers. The resulting program includes experiences in sharing feelings and ideas with peers; listening to the views of younger people; studying lifespan growth and adjustment; acquiring intergenerational communication skills; and focusing self-evaluation. A fieldtest involving several hundred participants, equally divided into experimental and control groups, is underway to determine the worthwhileness of this approach to family development.
Age Factors↗
Localization, in human placenta, of the tightly bound form of DNA methylase in the higher order of chromatin organization.
In human placenta, the DNA of all subfractions of the third level of chromatin organization exhibits similar values of the methylcytosine-to-cytosine ratio. The tightly bound form of DNA methyltransferase is mostly recovered in the 'stripped loop' fraction, although, on the basis of the DNA content, the 'stripped loops' and the 'stripped matrix' appear to possess a similar amount of the enzyme. DNA methyltransferase activity is instead totally absent from the 'digested matrix', i.e., from the fraction remaining after digestion of the 'stripped matrix' with DNAase I. Upon addition of exogenous DNA methyltransferase, however, the DNA of this fraction, which is only 1% (in weight) of the total chromatin DNA and which has a length of approx. 9 kbp, can readily undergo methylation.
5-Methylcytosine↗
Citrobacter diversus ULA-27 beta-lactamases. Improved purification and general properties.
Two chromosome-encoded beta-lactamases have been purified from Citrobacter diversus ULA-27. They exhibited slightly different isoelectric points (6.8 and 6.2) and very similar Mr values (congruent to 29,000). Their specificity spectrum was rather wide, since they hydrolysed some cephalosporins with kcat: values similar to those observed with the best penicillin substrates. Cloxacillin, methicillin and imipenem were hydrolysed very slowly. Hydrolysis of azthreonam could not be detected.
Amino Acids↗
Tightly-bound non-histone proteins in different nucleosome-like subpopulations from pig kidney chromatin.
By differential sucrose gradient centrifugation of pig kidney chromatin in the presence or absence of Na-EDTA and under varying ionic strength conditions, three nucleosome-like subpopulations with different buoyant densities can be obtained. These particles, on the basis of their histones and HMG protein pattern, of the 5-methylcytosine level of their DNA and of the RNA polymerase activity associated with them, can be considered as originating from chromatin fractions differently involved in gene expression. Two-dimensional electrophoresis of the tightly-bound non-histone proteins shows a distinct pattern for each subpopulation, such protein components being notably present in restricted numbers but in high amounts in the subpopulation which was apparently derived from condensed heterochromatin.
Animals↗
Uptake of amino acids by brain microvessels isolated from rats with experimental chronic renal failure.
The neurological disorders seen in patients with chronic renal failure and liver cirrhosis are analogous. Previous in vivo studies have shown that the impaired blood-brain amino acid transport seen in rats with chronic renal failure is similar to that of rats with portocaval anastomosis. To elucidate whether a comparable underlying pathogenic mechanism plays a role in both pathological conditions, blood and brain amino acid levels together with amino acid transport by isolated brain microvessels have been studied in rats with chronic renal failure and in sham-operated rats. Brain microvessels isolated from rats with experimental chronic renal failure showed that the uptake of labeled large neutral amino acid, i.e., leucine or phenylalanine, but not of lysine or alpha-methylaminoisobutyric acid, was significantly increased with respect to sham-operated rats; conversely, the uptake of glutamic acid in rats with chronic renal failure was significantly lower compared with values in controls. Kinetic analysis indicated that this was mainly due to increased exchange transport activity (Vmax) of the L-system, rather than to changes in the affinity (Km) of the carrier system for the relative substrate. These data, together with the significant rise of brain glutamine levels and an increased brain-to-plasma ratio of the sum of large neutral amino acids, are analogous to what was previously observed in rats with portocaval anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine Triphosphate↗
Immunochemical and biological characteristics of a human autoantibody to human chorionic gonadotropin and luteinizing hormone.
Anti-hCG/LH autoantibodies were found in the serum of an infertile woman a few days after an abortion which occurred after 46 days of amenorrhea. The antibody titer increased for approximately 4 more weeks, and then declined to low levels during a 14-month anovulatory period, after which regular menses resumed. Immunoglobulins isolated from a pool of serum obtained during the postabortion period neutralized the activity of both hCG and LH in an in vivo bioassay, and the binding affinity of the antibodies toward both hormones was high. When menses were resumed, there was a considerable reduction of the affinity toward LH. The variations in antibody titers and/or affinities can explain the sequence of fertilization, abortion, anovulatory period, and normalization of menses.
Abortion, Spontaneous↗
Do tightly-bound chromatin proteins play a role in DNA methylation?
When chromatin matrix, "stripped" from its loosely-bound components by extraction with 3 M NaCl, is extensively digested with DNAase I, a fraction is obtained, which carries no endogenous DNA methyltransferase activity but which is a good substrate for externally added enzyme. Under the same conditions, protein-free DNA isolated from this fraction can instead hardly be methylated, this different behaviour pointing to a role of DNA-tightly-bound proteins in favoring or promoting the catalytic action of the enzyme. A similar stimulation of enzymatic methylation could also be shown when, in the presence of this same fraction, single stranded Micrococcus luteus DNA was incubated with placental methyltransferase, using S-adenosylmethionine as a methyl donor. This finding can be correlated to the existence, in chromatin loops, of small regions which resist digestion by DNAase I also after high-salt removal of their loosely-bound components (presumably because of the presence of tightly-bound proteins) and whose DNA is characterized by high methylation levels and, at the same time, by high relative content of thymine.
Binding Sites↗
Inactivation of de novo DNA methyltransferase activity by high concentrations of double-stranded DNA.
The activity of eukaryotic DNA methyltransferase diminishes with time when the enzyme is incubated with high concentrations (200-300 micrograms/ml) of unmethylated double-stranded Micrococcus luteus DNA. Under similar conditions, single-stranded DNA induces only a limited decrease of enzyme activity. The inactivation process is apparently due to a slowly progressive interaction of the enzyme with double-stranded DNA that is independent of the presence of S-adenosyl-L-methionine. The inhibited enzyme cannot be reactivated either by high salt dissociation of the DNA-enzyme complex or by extensive digestion of the DNA. Among synthetic polydeoxyribonucleotides both poly(dG-dC).poly(dG-dC) and poly(dA-dT).poly(dA-dT), but not poly(dI-dC).poly(dI-dC), cause inactivation of DNA methyltransferase. This inactivation process may be of interest in regulating the 'de novo' activity of the enzyme.
DNA↗