The effects of class IA antiarrhythmic drug on the common type of atrial flutter in combination with pacing therapy

In 11 patients with common type of atrial flutter (common AF), rapid atrial pacing from the high right atrium was performed before and/or after class Ia antiarrhythmic drug administration, confirming transient entrainment by decreasing the pacing cycle length by 10 ms. In 10 patients before the drug administration, common AF was not interrupted although the pacing cycle length was decreased to 200 ms in 5 patients, accelerated atrial flutter or atrial fibrillation was induced in 4 patients, and common AF was converted into sinus rhythm in only 1 patient. After the drug administration common AF was converted into sinus rhythm in 5 out of 6 patients. The class Ia antiarrhythmic drug prolonged the common AF cycle length (255 +/- 12 ms vs. 298 +/- 37 ms, p less than 0.005) and widened the entrainment zone (64 +/- 7 ms vs. 90 +/- 20 ms, p less than 0.05). The widening of the entrainment zone and the prolongation of the common AF cycle length facilitate the successful conversion of common AF at a longer pacing cycle length, which would not precipitate atrial fibrillation or accelerated atrial flutter. The combination therapy of rapid atrial pacing and the class Ia antiarrhythmic drug is thought to be useful in the therapy of common AF.

Erythrocyte enzyme activities in myelodysplastic syndromes: elevated pyruvate kinase activity

The erythrocyte enzyme activities in twenty-six cases of myelodysplastic syndromes were determined. There were remarkably abnormal levels in seven cases; namely, four cases showed increased hexokinase activity, three cases showed increased pyruvate kinase activity, and two cases showed increased adenosine deaminase activity. Among these, one case with elevated pyruvate kinase activity showed the novel expression of M2-type pyruvate kinase activity, in addition to the R-type pyruvate kinase activity normally found in erythrocytes. Southern blotting of peripheral leucocyte DNA revealed only an amplified PK-LR genome, which derived from the chromosomal abnormality of a 1;7 translocation. The mechanism responsible for switching M2-type to R-type during erythroid maturation was considered to be partially disrupted in this case.

Human M2-type pyruvate kinase: cDNA cloning, chromosomal assignment and expression in hepatoma

Two overlapping clones, covering the entire coding sequence of human M2-type pyruvate kinase (PK) cDNA, were isolated and sequenced. Nucleotide sequencing results showed that they contained the 109-bp 5'-untranslated region, the 1593-bp coding region and the 585-bp 3'-untranslated region. Nucleotide sequence homology was 90% and 69% with rat M2-type and L-type PK cDNA, respectively. In situ hybridization using the human M2-type PK cDNA probe disclosed that the gene for M2-type PK is located at band q22 on chromosome 15. Northern blot analysis with RNA from human hepatoma demonstrated that M2-type PK was predominantly expressed in hepatoma cells, whereas L-type PK was preferentially expressed in the non-tumor portion of the liver.

Cytogenetic study of chronic lymphocytic leukemia in ten Japanese patients with a case of the same chromosome abnormality both in T and B cells

Peripheral blood lymphocytes from ten patients with chronic lymphocytic leukemia (CLL) stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM), Epstein-Barr virus (EBV), and T-cell growth factor were studied cytogenetically. Eight of ten cases were clinically and immunologically B-cell CLL, and two cases were T-cell CLL. Chromosome analysis revealed that one patient, diagnosed as B-cell CLL, had a clonal abnormality in the leukemic cells. The abnormal karyotype was 46,XY,+3,-15,t(10;19)(q22;p13),t(11;14) (q13;q32),13q+,17q-. The frequencies of the abnormal cell stimulated with PHA, PWM, and EBV were 50%, 13%, and 100%, respectively. Finding the same clonal abnormality after stimulation with three different mitogens suggests that the factor responsible for the development of CLL might affect the stem cell common to T-cell and B-cell lymphocytes. In cells with this abnormal karyotype, chromosome 13q+ seems to have a homogeneous staining region. In the present series of B-cell CLL, no trisomy 12 known to be the specific chromosome abnormality was observed.

Effects of hypoxia on contractile responses of rabbit aortic strips to transmural electrical stimulation

To clarify the effects of hypoxia on adrenergic transmission, we examined the contractile responses of isolated rabbit aortic strips to electrical stimulation, the concentration-response relationships for noradrenaline and KCl, and the electrical stimulation-evoked overflows of total [3H] and [3H]noradrenaline from strips preloaded with [3H]noradrenaline in media equilibrated with gas mixtures containing various concentrations of O2. Contractile responses to electrical stimulation were completely inhibited by tetrodotoxin and alpha-adrenoceptor antagonists such as phentolamine and phenoxybenzamine, but were not affected by indomethacin. When the concentration of O2 in the gas mixture was decreased from 95% to 20%, the contractile responses to electrical stimulation remained unchanged, but as the concentration of O2 was further decreased, the responses were inhibited concentration-dependently. At 0% O2, the response was inhibited by about 80% when compared with control values obtained at 95% O2, and the electrical stimulation-evoked overflows of total [3H] and [3H]noradrenaline into the superfusates were decreased by about 55%. At 0% O2, the concentration-response curve for exogenous noradrenaline was shifted to the right about 50-fold and the maximum response was decreased by 25%. The maximum contractile responses of aortic strips from animals pretreated with reserpine or 6-hydroxydopamine to high KCl were decreased slightly (about 15%). These results suggest that inhibition of adrenergic transmission under hypoxic conditions is mainly the result of a decrease in the stimulus-evoked release of noradrenaline and of a decrease in the affinity of alpha-adrenoceptor for noradrenaline and/or inhibition of signal transduction mechanisms, although hypoxia also causes a slight decrease in the contractility of vascular smooth muscle.

Genetic analysis of adenosine deaminase expression in adult T-cell leukemia

We investigated the genetic basis for the increased adenosine deaminase (ADA) expression in adult T-cell leukemia (ATL). We found a correlation between the levels of ADA-specific mRNA and ADA immunoreactive protein in ATL. Southern blot analysis revealed no gene amplification or rearrangement of the ADA gene. These findings indicate that increased ADA expression in ATL cells reflects increased transcriptional activity for the ADA gene or increased stability of ADA mRNA.

The use of enzymopathic human red cells in the study of malarial parasite glucose metabolism

The in vitro growth of Plasmodium falciparum malaria parasites was assayed in mutant red cells deficient in either diphosphoglycerate mutase (DPGM) or phosphoglycerate kinase (PGK). In addition, cDNA probes developed for human DNA sequences coding for these enzymes were used to examine the parasite genome by means of restriction endonuclease digestion and Southern blot analysis of parasite DNA. In both types of enzymopathic red cells, parasite growth was normal. In infected DPGM deficient red cells, no DPGM activity could be detected, and in normal red cells, DPGM activity declined slightly in a manner suggestive of parasite catabolism of host protein. However, in infected PGK deficient red cells, there was a 100-fold increase in PGK activity, and in normal red cells, a threefold increase in PGK activity was observed. Parasite PGK could be recovered from isolated parasites, and a marked increase in heat instability of parasite PGK as compared with the host cell enzyme was noted. Neither cDNA probe was found to cross-react with DNA sequences in the parasite genome. It is concluded that the parasite has no requirement for DPGM, and probably has no gene for this enzyme. On the other hand, the parasite does require PGK, (an adenosine triphosphate [ATP] generating enzyme) and synthesizes its own enzyme, which must have been encoded in the parasite genome. The parasite PGK gene most likely lacks sufficient homology to be detected by a human cDNA probe. Enzymopathic red cells are useful tools for elucidating the glycolytic enzymology of parasites and their co-evolution with their human hosts.

Molecular analysis of Lesch-Nyhan syndrome found in Japan

Molecular analysis of four unrelated patients with Lesch-Nyhan (L-N) syndrome was performed. All four cases had typical clinical features of L-N syndrome, and the activities of hypoxanthine-guanine phosphoribosyltransferase (HPRT) were absent. No structural gene abnormalities were found by Southern blot analysis in all cases, and a decrease of HPRT mRNA was not detected by dot blot analysis in two of the four cases. However, HPRT enzyme proteins were detected by Western blot analysis in all cases. Our results showed that the production of immunologically reactive but enzymatically inactive mutant HPRT protein was pathogenic for all four patients.

Regional difference in the kinetics of choline acetyltransferase in brains of neurologically normal elderly people and those with Alzheimer-type dementia

In order to clarify the biochemical changes which occur in the brains of patients suffering from Alzheimer-type dementia (ATD), the kinetics of choline acetyltransferase (ChAT) were measured in 8 or 11 regions of post-mortem brains of 6 patients with non-neurological diseases (control subjects) and 8 patients with ATD. In the control subjects, Michaelis constants (Km) of ChAT for choline were lower in the caudate nucleus and putamen than in other regions examined, whereas Km values for acetyl-CoA in these two regions were higher. Maximal velocities (Vmax) for the control subjects were higher in the caudate nucleus and putamen than in the other regions studied. Km values for choline of ATD patients were higher than those of control subjects in all regions except the amygdala and substantia innominata (innominate); however, Km values for acetyl-CoA of ATD patients were higher than those of control subjects only in the caudate nucleus, putamen and thalamus. Vmax values of ATD patients were lower than those of control subjects in all the regions of brains with ATD. These results suggest that the binding site of ChAT for choline is sensitive to the pathological process of ATD, whereas the binding site for acetyl-CoA is resistant. Based on the presence or absence of variations of Km values, we have classified brain regions into 3 types: highly sensitive, somewhat sensitive or resistant to the pathological process of ATD.

A new glucose-6-phosphate dehydrogenase variant (G6PD Tsukui) associated with congenital hemolytic anemia

A new glucose-6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was found in a 20-year-old Japanese male who showed mild hemolysis after an upper respiratory tract infection. The patient had been noted to have jaundice and reticulocytosis several times before this episode. The enzyme activity of the variant was 1.5% of normal. The enzymatic characteristics were slow anodal electrophoretic mobility, high Km G6P, normal Km NADP, decreased heat stability, and a normal pH optimum. From these results, the enzyme was considered to be a new class 1 variant and was designated G6PD Tsukui.

Thyroxine surge in metamorphosing flounder larvae

The tissue concentration of thyroxine (T4) in larval flounder (Paralichthys olivaceus) was studied at various stages of their metamorphosis using a specific radioimmunoassay developed for samples obtained by quantitative extraction of the hormone from fish eggs and larvae. T4 concentrations were below the limit of detection in extracts of fertilized eggs and larvae until the end of prometamorphosis. Several dorsal fin rays continued growing from premetamorphosis until the end of prometamorphosis. The hormone became detectable at the onset of metamorphic climax when the elongated dorsal fin rays stopped growing. A sharp increase in tissue T4 concentration was observed in midclimax of metamorphosis, and the high level of T4 (11-13 ng/g body weight) was maintained until the end of the climax. The period of elevated T4 levels coincided with resorption of the elongated dorsal fin rays. The right eye completed translocation from the right to the left side of the body during metamorphic climax. The tissue T4 level declined to about a half of the peak value during postclimax, and then increased moderately in later adult-type juveniles. The results of an additional experiment, in which fertilized eggs and newly hatched larvae were treated with T4 and/or thiourea, suggested the presence of negative feedback regulation of pituitary-thyroid axis, implying an involvement of thyroid hormones even in early premetamorphic larvae. These results suggest that metamorphic climax is induced by a surge of thyroid hormone, and that thyroid hormone may also regulate development before and after the metamorphosis.

Elevated erythrocyte adenosine deaminase activity in a patient with primary acquired sideroblastic anemia

We report a case of primary acquired sideroblastic anemia (PASA) associated with elevated erythrocyte adenosine deaminase (ADA) activity. The patient was an 85-year-old Japanese male. Analysis of the peripheral blood revealed pancytopenia, and the bone marrow findings showed marked ringed sideroblasts and chromosomal deletion (46XY, 11q-). The erythrocyte ADA activity was 17 times higher than that of normal control, the leukocyte ADA activity was within the normal range, and the plasma ADA activity was 2 times higher than the normal mean. The adenine nucleotides in the patient's erythrocytes were within normal range. According to starch gel electrophoresis, ADA isozyme of the patient was ADA 1. Western blotting showed an increased amount of ADA protein in the patient's erythrocytes. Southern blotting revealed no gene amplification or large structural change. Dot blot analysis of the reticulocyte mRNA showed no increase in the amount of ADA mRNA in the patient's reticulocytes compared with those of reticulocyte-rich controls. We considered that the mechanism of elevated ADA activity in this acquired defect was similar to that found in hereditary hemolytic anemia associated with ADA overproduction.

Human liver type pyruvate kinase: complete amino acid sequence and the expression in mammalian cells

Pyruvate kinase (PK) has four isozymes (L, R, M1, M2) that are encoded by two different genes. Among these isozymes, abnormalities of liver (L)-type PK is considered to be associated with hereditary nonspherocytic hemolytic anemia in humans. We isolated and determined the full-length sequence of human L-type PK cDNA. The cDNA contains 1629 base pairs encoding 543 amino acids, 68 base pairs of 5'-noncoding sequence, and 734 base pairs of 3'-noncoding sequence. The similarity between human and rat L-type PK was 86.9% at the nucleotide sequence level and 92.4% at the amino acid sequence level. The full-length L-type PK cDNA was placed under the promoter of simian virus 40 and introduced into monkey COS cells. Human L-type PK activity was detected in the extract of COS cells by the classical PK electrophoresis method.