Effect of purine antagonists on the cAMP level in lymphocytes and bone marrow lymphoblasts

The effect of the purine receptor ligands N-ethylcarboxamide adenine and adenosine and of the purine antagonists mercaptopurine and azathioprine on the intracellular cAMP content in human peripheral blood lymphocytes and bone marrow lymphoblasts was studied. All preparations tested induced an increase in the cAMP level in peripheral blood lymphocytes. The selective immunosuppressive effect of adenosine antagonists may be due to their ability to modulate the activity of adenylate cyclase in lymphoid cells. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o . 3, pp. 294–296, March, 1995     

Control of the expression of the ADE2 gene of the yeast Saccharomyces cerevisiae

The ADE2 gene encodes AIR-carboxylase which catalyzes the sixth step of the purine biosynthetic pathway in Saccharomyces cerevisiae. We have analyzed the effect of deletions in the promoter region of this gene on the expression of the enzyme using a fusion of the ADE2 gene promoter to the bacterial lacZ gene. Adenine added to the growth medium repressed the expression of the fusion at the level of mRNA. The ADE2-lacZ fusion expression can be slightly activated in response to amino-acid starvation, but only in Gcn4 ⁺ strains and in an adenine-supplemented medium. In the absence of adenine in the medium ADE2 gene expression is derepressed, and neither starvation for histidine nor a gcd1 general control regulatory mutation leads to additional derepression. Our experiments indicate that the ADE2 gene of the purine biosynthetic pathway is under both specific adenine control and the general amino-acid control system. The cis-acting promoter elements mediating both modes of regulation overlap each other and are located around the proximal TGACTC sequence.     

Role of ATP as a sympathetic nervous system transmitter in the smoothing of rapid arterial pressure changes

Arterial pressure lability and its variations were examined in unrestrained rats following selective elimination of adrenergic or purinergic sympathetic influences on the circulatory system. Both the α₁-andrenoceptor blocker prazosin and the nonselective α-adrenoceptor blocker phentolamine lowered the arterial pressure without affecting its lability. When P_2x purine receptors were desensitized with α,β-methyleneATP, the resulting pronounced hypotension was accompanied by a two-fold increase in the lability of mean arterial pressure. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N^no 11, pp. 461–464, November, 1995 Presented by I. P. Ashmarin, Member of the Russian Academy of Medical Sciences     

Genetic evidence for the essential role of PfNT1 in the transport and utilization of xanthine, guanine, guanosine and adenine by Plasmodium falciparum

The malaria parasite, Plasmodium falciparum, is unable to synthesize the purine ring de novo and is therefore wholly dependent upon purine salvage from the host for survival. Previous studies have indicated that a P. falciparum strain in which the purine transporter PfNT1 had been disrupted was unable to grow on physiological concentrations of adenosine, inosine and hypoxanthine. We have now used an episomally complemented pfnt1Delta knockout parasite strain to confirm genetically the functional role of PfNT1 in P. falciparum purine uptake and utilization. Episomal complementation by PfNT1 restored the ability of pfnt1Delta parasites to transport and utilize adenosine, inosine and hypoxanthine as purine sources. The ability of wild-type and pfnt1Delta knockout parasites to transport and utilize the other physiologically relevant purines adenine, guanine, guanosine and xanthine was also examined. Unlike wild-type and complemented P. falciparum parasites, pfnt1Delta parasites could not proliferate on guanine, guanosine or xanthine as purine sources, and no significant transport of these substrates could be detected in isolated parasites. Interestingly, whereas isolated pfnt1Delta parasites were still capable of adenine transport, these parasites grew only when adenine was provided at high, non-physiological concentrations. Taken together these results demonstrate that, in addition to hypoxanthine, inosine and adenosine, PfNT1 is essential for the transport and utilization of xanthine, guanine and guanosine.     

An addition to the chromosome map of Schizosaccharomyces pombe: the localization of gua genes

Summary The gua1 and gua2 genes, encoding enzymes for the biosynthesis of guanylic acid (GMP) in Schizosaccharomyces pombe, were found to be located on chromosomes II and I respectively, and the sites of these genes were precisely determined on the chromosome maps. With this additional finding, the order of all the genes involved in the biosynthesis of purine nucleotides in S. pombe has now been established.     

Antioxidant properties of thiamine

Thiamine (10⁻⁴–10⁻⁶ M) inhibits lipid peroxidation in rat liver microsome and free radical oxidation of oleic acidin vitro. Thiamine interacts with free radicals and hydroperoxides and is oxidized to thiochrome and thiamine disulfide. The antioxidant effect of thiamine is probably related to sucessive transfer of 2H⁺ from the NH₂ group of the pyrimidine ring and H⁺ from the thiazole ring (after its opening) to reactive substrates. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 303–305, September, 2000     

Antioxidant properties of thiamine

Thiamine (10⁻⁴–10⁻⁶ M) inhibits lipid peroxidation in rat liver microsome and free radical oxidation of oleic acidin vitro. Thiamine interacts with free radicals and hydroperoxides and is oxidized to thiochrome and thiamine disulfide. The antioxidant effect of thiamine is probably related to sucessive transfer of 2H⁺ from the NH₂ group of the pyrimidine ring and H⁺ from the thiazole ring (after its opening) to reactive substrates. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 303–305, September, 2000     

Effects of isoproterenol and suphan on the concentration of free calcium ions in isolated cardiomyocytes: a comparative study

Isoproterenol and suphan, two cardioactive drugs with different mechanisms of action, are studiedin vitro for their effects on calcium homeostasis in myocardial cells. Isoproterenol lowers the basal Ca²⁺ level in resting cardiomyocytes and potentiates its rise in these cells after their induction. Suphan stimulates reversible elevation of the diastolic Ca²⁺ concentration, causing increased calcium accumulation in the sarcoplasmic reticulum of cardiomyocytes. In anin vitro model of hypoxia, the Ca response to isoproterenol is significantly reduced, whereas that to dibutyryl cAMP is retained. The effect of suphan on the Ca²⁺ content of cardiomyocytes exposed to “chemical” hypoxia is 30–50% higher than its effect on the Ca²⁺ content of intact cells. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 8 pp. 170–172, August, 1996     

Changed count of CD4+ T-lymphocytes in the bone marrow of aggressive CBA mice

Enhanced immune response of aggressive CBA mice after 10 daily confrontations in sensory contact on day 4 after immunization with sheep red blood cells (5×10⁸) is paralleled by an increase in the count of CD4⁺ T-cells in the bone marrow. Aggressive behavior, weight of the spleen, and count of CD4⁺ T-helpers in the bone marrow (which is increased only in aggressors with a history of at least 3 victories) are correlated. The effect of aggressive behavior on immunity can be caused by changes of the neurochemical status of the brain and determined by an increase in the CD4⁺ T-helper count. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 11, pp. 544–546, November, 1997     

Binding of3H-diazepam in rat brain eleven months after termination of corazole kindling

Binding of³H-diazepam in rat cerebellum decreases by 14% (p<0.05) 11 months after termination of kindling and one day after injection of a test dose of corazole (30 mg/kg), while it increases by 19.5% after a single injection of a convulsive dose of corazole (50–75 mg/kg). No changes are found in the cortex. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 2, pp. 135–137, February, 1994 Presented by G. N. Kryzhanovskii, Member of the Russian Academy of Medical Sciences     

Correction of testosterone-induced changes in a population of hemopoietic precursors by a bone-marrow inhibitor of the proliferative activity of a hemopoietic stem cell

A factor inhibiting the proliferation of splenic colony-forming units, injected bothin vivo and after preincubation of mouse bone marrow cellsin vitro, had a dose-dependent effect on the increased proliferative activity of splenic colony-forming units from the bone marrow of mice treated with testosterone propionate. This was associated with a reduction in the number of early hemopoietic precursors of mouse bone marrow. The counts of clonogenic granulocytic-macrophagal and macrophagal colony-forming units decreased and that of burst-forming units in murine bone marrow increased after exposure to the hormone. Testosterone propionate promoted a decrease of the repopulating potential of bone marrow cells, which recovered after their preincubation with the factor inhibiting the proliferation of splenic colony-forming units. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 10, pp. 394–397, October, 1995     

Ultrastructure and proliferation of gastric epitheliocytes during exposure to ultraviolet laser

Local exposure to ultraviolet laser in a dose of at least 4 J/cm² decreases the epitheliocyte labeled nuclei index in the fundal portion of the stomach, the decrease being the greatest for actively proliferating cervical cells. It involves a decrease in the amount of parietal microorganisms and alteration of epitheliocytes. The latter phenomenon was most expressed after a dose of 6 J/cm². Changes caused by UV laser were observed 24 h after exposure. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 5, pp. 583–586, May, 1998     

Morphological characteristics of lymphocyte-hepatocyte contacts in various periods of liver regeneration in mice

The histo-and ultrastructure of regenerating murine liver is studied after excision of 2/3 of its tissue. Counts of leukocytes and lymphocytes are found to be increased in the intertrabecular spaces after the operation. Lymphocytes come in close contact with hepatocytes and reticuloendotheliocytes forming microtunnels at the sites of contact. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 2, pp. 176–179, February, 1994     

The ade4 gene of Schizosaccharomyces pombe: cloning,sequence and regulation

We report the isolation and sequence of the Schizosaccharomyces pombe ade4 gene which encodes the glutamine phosphoribosylpyrophosphate amidotransferase, the first enzyme of the purine nucleotide de-novo biosynthetic pathway. The enzyme contains 533 amino acids and its sequence exhibits homologies to the corresponding enzymes of Saccharomyces cerevisiae, Escherichia coli, Bacillus subtilis, chicken, rat, and human. In contrast to the situation in S. cerevisiae, adenine does not repress ade4 expression at the mRNA level and also other nutritional signals seem not to affect its expression.     

Effect of AA-2414, a thromboxane A2 receptor antagonist, on airway inflammation in subjects with asthma

Background: Asthma is a chronic inflammatory disease of the airways. The chemokines are potent chemoattractants for eosinophils and other types of cells associated with allergic inflammation. AA-2414, a new thromboxane A₂ receptor antagonist, reduces bronchial hyperresponsiveness in asthmatic subjects, but its mechanism of action is unclear. Objective: We tested the hypothesis that the beneficial effects of AA-2414 in asthma result from reduction in the number of inflammatory cells infiltrating the airway associated with inhibition of chemokine release. Methods: We studied bronchial biopsy specimens from 31 asthmatic subjects before and after oral treatment with AA-2414 (80 mg/day) or matched placebo for 4 months in a double-blind manner. Biopsy specimens were examined by immunohistochemistry. Each subject recorded symptom score and peak expiratory flow (PEF). Lung function and bronchial responsiveness to methacholine were measured before and after treatment. Results: After treatment, significant improvements in symptom score (P < .05), PEF (P < .01), diurnal variation of PEF (P < .01), and bronchial responsiveness (P < .01) were observed in the AA-2414 group compared with the placebo group. These improvements were accompanied by a significant decrease in the number of submucosal EG2⁺ eosinophils (P < .05). There was also a reduction in the number of cells expressing RANTES (P < .05) and macrophage inflammatory protein (MIP)-1α (P < .05) in the epithelium and of cells expressing monocyte chemotactic protein-3 (P < .01), RANTES (P < .05), MIP-1α (P < .01), and eotaxin (P < .01) in the submucosa in the AA-2414 treatment group. A significant correlation was found between the number of EG2⁺ eosinophils and numbers of monocyte chemotactic protein-3⁺ (r_s = 0.52, P < .005), MIP-1α⁺ (r_s = 0.34, P < .05), and eotaxin⁺ cells (r_s = 0.47, P < .01) in the submucosa. There was a significant negative correlation between the increase in bronchial responsiveness and the change in number of submucosal EG2⁺ cells (r_s = –0.65, P < .001). Conclusions: These findings suggest that AA-2414 treatment of patients with asthma may inhibit activated eosinophil infiltration in part by modulating the expression of chemokines in bronchial tissues. (J Allergy Clin Immunol 1999;103:1054-61.)     

Promoter Methylations of p16 and p14 Genes in Early and Advanced Gastric Cancer. Correlations of the Modes of Their Occurrence with Histologic Type

The INK4a/ARF locus encodes two cell cycle-regulatory proteins, p16^INK4a and p14^ARF. These share an exon using different reading frames, and act through Rb and p53 pathways. Recently, it has been found that silencing of p16^INK4a and p14^ARF expressions by aberrant methylation of the CpG islands in the promoter regions is an alternative mechanism that inactivates possible tumor suppressor functions in various tumors. To clarify the features of gastric cancers with promoter methylation of p16^INK4a and p14^ARF, we investigated the methylation status in gastric cancer cell lines and primary gastric cancers using methylation-specific PCR (MSP), and correlated the methylation status with microsatellite instability (MSI), DNA ploidy pattern, p53 immunohistochemistry, and various clinicopathologic factors, paying attention to the correlations with the histologic types. Of 10 cell lines studied, silencing of the expression of p16^INK4a and p14^ARF due to promoter methylation was detected by MSP and RT-PCR in six (60%) and two (20%) cell lines, respectively. p14^ARF silencing was detected only in cell lines derived from gastric cancer of the diffuse type, while p16^INK4a silencing was found in cell lines derived from both diffuse and intestinal types. In 59 primary gastric cancers, promoter methylation of p16^INK4a and p14^ARF was found in 10 (17%) and 14 (24%) of the tumors independently, there being an association with DNA diploidy, but not with p53 immunohistochemistry. p16^INK4a methylation was found irrespective of tumor stages and histology. Whereas p14^ARF methylation was found more frequently in intestinal type cancers in an early stage and in diffuse type cancers in an advanced stage, MSI tended to be related especially to p14^ARF methylation in cancers of the intestinal type. Thus, the significance of p14^ARF methylation differed between intestinal and diffuse types, while such a difference was not observed in p16^INK4a methylation.     

Effect of recombinant human erythropoietin on the rate of Na+,H+-exchange in erythrocytes from patients with chronic renal failure on hemodialysis

The study explores the effect of recombinant human erythropoietin and the rate of Na⁺,H⁺-exchange in erythrocytes from patients with chronic renal failure undergoing hemodialysis. The rate of Na⁺,H⁺-exchange in erythrocytes from patients was higher than in the control and remained unchanged after 24 months of treatment with erythropoietin. Therapy with recombinant human erythropoietin does not normalize the Na⁺,H⁺-exchange mechanism. It is concluded that factors underlying disturbances of ion transport in erythrocytes from uremic patients cannot be corrected with erythropoietin. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 12, pp. 613–615, December, 1997     

The effect of various incorporated doses of131I on immunological reactions of the organism

Administration of radioisotope¹³¹I at 148 kBq/g body weight results in an inhibition of the primary immune response and in a decrease of proliferating activity of mouse lymphocytes in response to alloantigen stimulation. The number of antibody-producing spleen cells for immunization of mice with sheep erythrocytes diminished after administration of¹³¹I at 74 kBq/g animal weight. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 6, pp. 664–666, June, 1996     

Effect of cytochromec on the necrosis zone in transitory myocardial ischemia

The cardioprotector effect of cytochromec during a 15-min complete blocking of the anterior descending branch of the left coronary artery was studied in rat experiments. Cytochromec in a dose of 20 mg/kg was found to noticeably reduce the necrosis zone 4 h after transitory ischemia. The protective effect of a single injection of cytochromec was virtually undetectable after 72, h, this pointing to the need for a course of treatment. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o , 4, pp. 439–440, April, 1994     

An abnormal cell division cycle in an AIR carboxylase-deficient mutant of the fission yeast Schizosaccharomyces pombe

Summary Adenine-requiring mutant strains of S. pombe enter the stationary phase after depleting a culture medium of adenine or its analogues. Stationary phase cells of six mutants defective at different stages of the purine nucleotide synthetic pathway were examined for cell volume and DNA content, and then compared in these respects with those of a prototrophic wild-type strain. The cell cycle of the wild-type strain was arrested in the G₂ phase (2C state) in the nitrogen rich medium, as is evident from DNA content per cell (0.0425 pg) and cell volume (47.7 m³). An AIR carboxylase-deficient (ade6) mutant strain was found to have an unusual cell volume (307.4 m³) and DNA content (0.1187 pg). By DAPI fluorescence microscopy, each mutant cell was seen to contain only one enlarged nucleus, which indicates the absence of cell populations containing cells in the 4C state of the S phase following nuclear division. It then follows that in ade6 mutant cells, DNA synthesis occurs in the absence of a completed nuclear division. Thus in S. pombe cells, the completion of nuclear division is not necessarily required for the next cycle initiation of DNA synthesis under certain physiological conditions.Abbreviation AIR aminoimidazole ribonucleotide - DAPI 4,6-diamidino-2-phenylindole - PCA perchloric acid - DABA 3,5-diaminobenzoic acid