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Biomedical subjects

A Blank

Publications and source records attributed to A Blank.

At least 55 records · Page 3Linked to original sources
PubMed1993

Six Colombian patients with adult T-cell leukemia/lymphoma.

Six Colombian patients with adult T-cell leukemia/lymphoma (ATL) are presented. The clinical and hematological features, the familial clusters of human T lymphotropic virus type 1 (HTLV-I) carriers and the prognoses of the Colombian ATL patients were similar to those previously reported for Japanese ATL patients. The only difference was the mean age of onset, which was more than 20 years younger than in Japanese patients. Three patients with ATL were suffering from strongyloidiasis. In one patient it was suggested that ATL developed after horizontal transmission from his wife. In addition, there was a familial case of ATL and HAM/TSP. It seems that in some areas of Colombia, not only HTLV-I infection and HAM/TSP but also ATL are highly endemic.

Adolescent↗
PubMed1991

Isolation of temperature-sensitive DNA polymerase III from Saccharomyces cerevisiae cdc2-2.

DNA polymerase III of the yeast Saccharomyces cerevisiae has been reported to be encoded at the CDC2 locus based on two observations. First, the CDC2 gene has homology to known DNA polymerase genes [Boulet et al. (1989) EMBO J. 8, 1849-1854], and second, the mutants cdc2-1 and cdc2-2 yield little or no DNA polymerase III activity in vitro [Boulet et al. (1989); Sitney et al. (1989) Cell 56, 599-605]. We describe here the isolation of temperature-sensitive DNA polymerase III from cdc2-2 strains. Our results provide direct experimental confirmation of the previously inferred gene/enzyme relationship and verify the conclusion that DNA polymerase III is required to replicate the genome. We isolated DNA polymerase III from two cdc2-2 strains, one containing the wild-type allele for DNA polymerase I (CDC17) and the other a mutant DNA polymerase I allele (cdc17-1). Yields from cdc2-2 cells of both DNA polymerase III activity and an associated 3'-5'-exonuclease activity [exonuclease III; Bauer et al. (1988) J. Biol. Chem. 263, 917-924] were decreased relative to yields from CDC2 cells. DNA polymerase III activity from cdc2-2 strains is thermolabile, displaying at least a 4-fold reduction in half-life at 44 degrees C. The activity is also labile at 37 degrees C, a temperature which is restrictive for growth of cdc2-2 but not CDC2 strains. At 23 degrees C, a temperature which is permissive for growth of both cdc2-2 and CDC2 strains, the mutant and wild-type DNA polymerase III activities display equal stability. These observations provide a demonstrable biochemical basis for the thermosensitive phenotype of cdc2-2 cells.

Alleles↗
PubMed1991

Three RNases in Senescent and Nonsenescent Wheat Leaves : Characterization by Activity Staining in Sodium Dodecyl Sulfate-Polyacrylamide Gels.

We have described three RNases in wheat leaves (Triticum aestivum L. cv Chinese Spring) and developed assays for measuring each RNase individually in crude leaf extracts. We initially used activity staining in sodium dodecyl sulfate-polyacrylamide gels to characterize RNases in extracts of primary and flag leaves. We thus identified acid RNase (EC 3.1.27.1, here designated RNase WL(A)), and two apparently novel enzymes, designated RNases WL(B) and WL(C). RNase WL(B) activity displays a distinctive isozyme pattern, a molecular mass of 26 kilodaltons (major species), a broad pH range with an optimum near neutrality, insensitivity to EDTA, and stimulation by moderate concentrations of KCl and by MgCl(2). RNase WL(C) activity exhibits a molecular mass of 27 kilodaltons, a neutral pH optimum, insensitivity to EDTA, and inhibition by KCl, MgCl(2), and tri-(hydroxymethyl)aminomethane. Based on distinctive catalytic properties established in gels, we designed conventional solution assays for selective quantitation of each RNase activity. We used the assays to monitor the individual RNases after gel filtration chromatography and native gel electrophoresis of extracts. In accompanying work, we used the assays to monitor RNases WL(A), WL(B), and WL(C), which are present in senescent and nonsenescent leaves, during the course of leaf senescence.

Journal Article↗
PubMed1991

Expression of Three RNase Activities during Natural and Dark-Induced Senescence of Wheat Leaves.

We have monitored the activities of RNases WL(A), WL(B), and WL(C) (A Blank, TA McKeon [1991] Plant Physiol 97: 1402-1408) during leaf senescence in wheat (Triticum aestivum L. cv Chinese Spring). When seedlings were induced to senesce in darkness, protein loss from primary leaves began immediately. RNase WL(B) activity was unchanged for 2 days and then rose linearly, reaching a sixfold elevation in 7 days. RNase WL(C) activity declined for 2 days and then rose linearly, reaching a twofold elevation in 7 days. RNase WL(A) activity declined in the first 2 days and was unchanged thereafter. Although differentially expressed, these RNase activities may respond to a common regulatory mechanism(s) which, at 2 days of darkness, signals progression into a more advanced stage of senescence. The RNase activities were also differentially expressed during light-induced recovery, returning to normal levels in dissimilar patterns. In flag leaves of greenhouse-grown wheat, the three RNase activities increased during the early postanthesis period when protein content was stable and underwent further, accelerated accumulation during senescence. RNase WL(B) activity showed the largest overall senescence-associated elevation (sixfold), followed by RNase WL(C) (fourfold) and RNase WL(A) (threefold).

Journal Article↗
PubMed1990

Comparison of the electrophysiological pattern of fatigue between athletes required to perform explosive and endurance sports.

The electrophysiological behavior of an isometric contraction sustained to fatigue, was examined in 6 long distance runners and 9 athletes involved in explosive (burst) sports, by on line computer analysis of the electrical activity of vastus medialis, rectus femoris and vastus lateralis. The experiments were carried out with a counterload of 50% of the maximal strength of the muscle. The duration of spike increased and the frequency decreased in the 3 examined muscles, in both types of sport. In the burst sports the changes of value of both parameters were statistically significant in the 3 muscles. In endurance sports the variations of duration were not significant and the changes of frequency were statistically significant only in the vastus lateralis. These results could be explained by the gradual activation of motor units of more strikingly different sizes in burst sports. Thus it may be speculated that prolonged training in burst sports may result in the automatic mobilization of higher number of small motor units, for the initiation of contraction while in endurance sports the onset of contraction is more gradual and carried out by large motor units.

Adolescent↗
PubMed1989

Single-strand-preferring nuclease activity in wheat leaves is increased in senescence and is negatively photoregulated.

Single-strand-preferring nucleases (EC 3.1.30.1) selectively cleave internucleotide bonds in single-stranded regions of predominantly duplex DNA and DNA.RNA hybrids and extensively degrade denatured DNA and RNA. The functions of single-strand-preferring nuclease in plants are unknown. We have monitored this nuclease activity in flag leaves of wheat (Triticum aestivum L. cv. Chinese Spring) undergoing natural senescence and in primary leaves of wheat seedlings undergoing dark-induced senescence. In falg leaves, nuclease activity remained at basal levels during the first 2 weeks after anthesis, while chlorophyll content increased to a maximum. Nuclease activity then rose in concert with a decline in chlorophyll, reaching a 16-fold elevation at 5 weeks post-anthesis, when 53% of the chlorophyll had been lost. When 8-day-old wheat seedlings were induced to senesce by placing them in darkness, nuclease activity rose without apparent lag, reaching a 13-fold elevation in 7 days, when 61% of the chlorophyll had been lost. The increase in nuclease activity was reversible upon reexposure of seedlings to light, a decline beginning without apparent lag. Reversibility was complete for plants that had been held in darkness for 5 days, with activity returning to the control level in 2 days. These senescence-related changes in nuclease activity, measured in conventional assays, were consistent with concomitant analysis by activity staining of sodium dodecyl sulfate/polyacrylamide gels. We conclude that an increase in single-strand-preferring nuclease activity is closely associated with wheat leaf senescence and that nuclease activity is subject to negative photoregulation.

Journal Article↗
PubMed1988

Differences in glycosylation pattern of human secretory ribonucleases.

The major secretory ribonuclease (RNase) of human urine (RNase HUA) was isolated and sequenced by automatic Edman degradation and analysis of peptides and glycopeptides. The isolated enzyme was shown to be free of other urine RNase activities by SDS/polyacrylamide-gel electrophoresis and activity staining. It is a glycoprotein 128 amino acids long, differing from human pancreatic RNase in the presence of an additional threonine residue at the C-terminus. It differs from the pancreatic enzyme in its glycosylation pattern as well, and contains about 45 sugar residues. Each of the three Asn-Xaa-Ser/Thr sequences (Asn-34, Asn-76, Asn-88) is glycosylated with a complex-type oligosaccharide chain. Glycosylation at Asn-88 has not been observed previously in mammalian secretory RNases. Preliminary sequence data on the major RNase of human seminal plasma have revealed no difference between it and the major urinary enzyme; their similarities include the presence of threonine at the C-terminus. The glycosylation pattern of human seminal RNase is very similar to that of the pancreatic enzyme. The structural differences between the secretory RNases from human pancreas, urine and seminal plasma must originate from organ-specific post-translational modifications of the one primary gene product. Detailed characterization of peptides and the results of gel filtration of tryptic and tryptic/chymotryptic digests of performic acid-oxidized RNase have been deposited as Supplementary Publication SUP 50146 (4 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1988) 249, 5.

Amino Acid Sequence↗
PubMed1986

An RNA polymerase mutant with reduced accuracy of chain elongation.

A new Escherichia coli RNA polymerase mutant was isolated which exhibited reduced accuracy of chain elongation in vivo and in vitro. The novel isolation procedure consisted of simultaneous selection for rifampicin resistance and screening for increased leakiness of an early, strongly polar nonsense mutation of lacZ, one of a special class of mutations whose leakiness reflects mainly transcriptional rather than translational errors. The spontaneous mutant thus isolated displayed a 3-4-fold increase in the leakiness of two different lacZ mutations of this class. Transduction analysis indicated that a single mutation, mapping in or very near the rpoB gene for the beta subunit of RNA polymerase, conferred both rifampicin resistance and increased nonsense leakiness. In an in vitro fidelity assay, homogeneous RNA polymerases from the mutant and parent strains exhibited error rates of 1/0.90 X 10(5) and 1/2.0 X 10(5), respectively, for the poly[d(A-T)] X poly[d(A-T)]-directed misincorporation of noncomplementary GMP. These error rates were verified by product analyses which further revealed that GMP was misincorporated in place of AMP in the synthesis of poly[r(A-U)]. The error rate of wild-type K12 RNA polymerase from a different source was 1/2.0 X 10(5), while that of a hybrid RNA polymerase, containing mutant core enzyme and wild-type sigma subunit, was 1/0.64 X 10(5). These error rates confirmed the selection of a transcriptional accuracy mutant. The error frequencies observed are much lower than those reported in other in vitro assays. The safeguards used to avoid artifactually enhanced misincorporation, and to thereby quantitate lower error rates, are discussed.

DNA-Directed RNA Polymerases↗
PubMed1984

Efficacy of ACTH 4-9 analog, methylphenidate, and placebo on attention deficit disorder with hyperkinesis.

The present study compared the efficacy of ACTH 4-9 analog, methylphenidate, and placebo on attention deficit disorder with 30 (HK) children with attention deficit disorder and psychometric measurements. HK children were randomly placed into three groups, according to body weight, and treated with placebo, methylphenidate, and adrenocorticotropic hormone fractions (ACTH 4-9 analog). The results revealed that HK children on methylphenidate manifested a significantly greater vasomotor reactivity, behavioral improvement, and learning receptivity than HK children taking ACTH 4-9 analog and/or placebo. Future research implications with ACTH 4-9 and HK children are discussed.

Adrenocorticotropic Hormone↗
PubMed1984

Effect of exercise of the lower limbs on the non-exercised biceps brachii muscle.

The electrophysiological pattern of fatigue of the biceps brachii (BB) muscle before and after bicycle leg exercise (LE), was evaluated in 12 healthy volunteers. In healthy people, the onset of isometric contraction is initiated by smaller motor units with briefer durations and higher spike frequencies. With the progression of contraction and muscular fatigue, electromyographic decrease in frequency and an increased spike duration occur. In our study, these findings were presented in subjects at the Final Value (FV) of electromyography before and after LE. In 8 subjects, the Initial Value (IV) of spike duration was longer after LE and a decrease in the frequency of electromyography was found in 9 of the 12 subjects. The changes in these two parameters at the onset of the BB contraction after LE may be due to the existence of an electrophysiological transfer effect. Eight subjects sustained the isometric BB contraction longer after LE than before LE. This may be explained by a diverting activity or other factors. Venous lactic acid was measured in 7 subjects and showed an increase after LE. No definite correlation between electromyographic changes and lactic acid was found.

Action Potentials↗
PubMed1983

Detection of enzymatic activities in sodium dodecyl sulfate-polyacrylamide gels: DNA polymerases as model enzymes.

Recent techniques for detecting the catalytic activity of enzymes in sodium dodecyl sulfate (SDS)-polyacrylamide gels have been hampered by lack of reproducibility associated with variability in commercial SDS preparations. Simple expedients which facilitate reproducible detection of DNA polymerase activity and which appear to be widely applicable to detection of other enzymes are reported here. It was observed that reproducibility of a reported procedure for DNA polymerase detection (Spanos, A., Sedgwick, S. G., Yarranton, G. T., Hübscher, U., and Banks, G. R. (1981) Nucl. Acids Res. 9, 1825-1839) depends on the SDS used for electrophoresis, and that sensitivity is markedly reduced if currently available SDS is substituted for the discontinued product specified by Spanos et al. A modified procedure yielding sensitivity with contemporary commercial SDS, which exceeds the sensitivity observed when using the protocol and the SDS originally specified, is described. The modifications employed, which presumably promote renaturation of enzymes, are (1) embedding fibrinogen in gels and (2) washing detergent from gels with aqueous isopropanol after electrophoresis. These expedients permit detection of picogram amounts of Escherichia coli DNA polymerase 1 and its Klenow fragment and nanogram amounts of calf thymus alpha and rat liver (Novikoff hepatoma) beta polymerases. Finally, it is shown that sensitivity of DNA polymerase detection is reduced by lipophilic contaminants in contemporary commercial SDS, and that the expedients employed here mitigate the deleterious effect of these impurities.

Acrylic Resins↗
PubMed1983

A comparative study of the efficacy of ACTH4-9 analog, methylphenidate, and placebo on attention deficit disorder with hyperkinesis.

The present study compared the behavioral performance of 30 children with attention deficit disorder with hyperkinesis (HK) on electrophysiological, biochemical, behavioral, and psychometric measurements. HK children were partitioned into cells of 10 and were then treated with placebo, methylphenidate, and adrenocorticotropic hormone fractions (ACTH4-9 analog), respectively, in a double-blind randomized cell sequence according to body weight. The results revealed that HK children on methylphenidate manifested a significantly greater vasomotor reactivity, behavioral improvement, and learning receptivity than did HK children taking ACTH4-9 analog and/or placebo. Future research implications with ACTH4-9 and HK children are discussed.

Adrenocorticotropic Hormone↗
PubMed1983

Electrically elicited blink reflex in children.

Blink reflex was studied in 12 neurologically intact infants and children aged 2 weeks to 3 years. A coaxial needle electrode inserted in the outer lower quadrant of the orbicularis oculi muscle was used for recording. Responses were elicited by a 50-100V current delivered through a stimulating electrode placed on the supraorbital groove. Absence of contralateral R2 response was a consistent finding. Ipsilateral R2 responses were elicited in 50% of the cases. R1 response was present in all instances and showed latency values similar to adults. The amplitudes of both R1 and R2 were lower than reported in adult population. The blink reflex may be an indication of the degree of myelination of the brain stem, facial and trigeminal pathways in children.

Age Factors↗
PubMed1983

[The tendon test of the tibial nerve in Hansen's disease].

Seventeen patients, presenting Hansen's disease, were studied by the Tendon-test. Nine presented pathological answers and 4 did not answer at all, probably due to serious damage. So the amount of pathological answers reached to 76.5% (13 patients). On the other hand, the answer of two patients was considered within the limits and they were classified with the normal answering patients that reached to 23.5% (4 patients). In order to find out if the tibial nerves are also injured simultaneously wit the ulnar and the median ones, it is advisable to employ this method in a larger number of patients and in a different social-geographical environment.

Adult↗