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At least 253 records · Page 14Linked to original sources
PubMed1994

Nucleoside transport sites in a cultured human retinal cell line established by SV-40 T antigen gene.

Adenosine, an important neuromodulatory compound in the brain and retina, is a potent vasodilator in most vascular beds throughout the body. Its actions are potentiated by inhibitors of nucleoside transport into cells. Knowledge of the existence of specific adenosine uptake systems in mammalian retina and the inhibition of the uptake by nitrobenzylthioinosine (NBMPR), a potent inhibitor of nucleoside transport, raises the possibility that the associated nucleoside transport system may be of pharmacological importance in retinal function. We have characterized the binding of the nucleoside transporter probe, [3H]NBMPR, to a cultured human retinal cell line established by transfection of SV-40 T antigen plasmid-DNA. The binding was specific, saturable and reversible. Scatchard analysis of the saturation data revealed that NBMPR binds to a homogeneous population of high affinity binding sites (KD = 0.65 +/- 0.22 nM; Bmax = 466 +/- 157 fmol/mg protein) characteristically similar to the binding sites in human retinal tissue (KD = 0.32 +/- 0.01 nM; Bmax = 292 +/- 41 fmol/mg protein). Selected compounds inhibited the binding in the cell line and retinal tissue with the same rank order of potency, suggesting that the transporters in the cell line and retinal tissue are similar. The data showed that the cell line is a useful model for the study of nucleoside transporter function in human retina.

Adenosine↗
PubMed1989

SV-40 large-T immortalization of embryonic bone cells: establishment of osteoblastic clonal cell lines.

Cells derived from embryonic rat calvariae were immortalized by retroviral delivery of cDNA for the SV-40 large T antigen and the bacterial neomycin resistance gene. After selection with G418, cells were cloned by limiting dilution and screened for expression of osteoblast characteristics. One clone (RCT-3), derived from cells collected during the third period of enzymatic digestion, showed high constitutive expression of alkaline phosphatase (ALP), synthesized type I collagen in the virtual absence of type III and exhibited a parathyroid hormone (PTH)-responsive adenylate cyclase (EC50, 10 nM). Messenger RNAs for osteonectin and osteopontin were present in RCT-3 cells and osteopontin mRNA was enhanced by 1,25 (OH)2 vitamin D3 treatment. The other cell line (RCT-1), derived from cells released during the first 10 min of digestion, expressed osteoblast features only after 3 d treatment with 1 microM retinoic acid (RA). ALP activity increased from 0.003 to 0.25 mumole/min/mg protein, there was a substantial increase in the steady-state level of type I collagen mRNA and a dose-dependent and saturable response to PTH was induced (EC50, 10 nM). Osteopontin mRNA was induced by 1,25 (OH)2D3. This study has provided two new cell lines which may be useful models for studies of differentiation-related gene expression in bone cells.

Animals↗
PubMed1984

The synthesis of 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives.

Two series of new semisynthetic rifamycin SV derivatives have been prepared. One of them bears a quaternary ammonium salt at C3 (1-5), and the other a pyridoimidazo system condensed at C3 and C4 (6-11). While compounds 1-5 had poor antibacterial activity in vitro, compounds 6-11 were found to be highly active in vitro but poorly absorbed in vivo. They could thus have potential as agents in the therapy of intestinal infections. The synthesis and the 1H NMR structure determination of these new compounds are reported.

Magnetic Resonance Spectroscopy↗
PubMedDate not supplied

Alteration of the cytoplasmic endonuclease cleavage pattern of SV-40 deoxyribonucleic acid in the presence of ATP, actinomycin D and ethidium bromide.

Endonuclease activities of cytoplasmic extracts of BSC-1 (E1) and BHK-21-cl 13 (E2) cells were assayed with SV-40 as a substrate and analysed by velocity sedimentation in alkaline and neutral sucrose gradients. Endonucleases were found to require Mg2+ ions for their activity. E1 endonuclease generated linear 6 S DNA fragments, pointing to non-random double-strand cleavage of DNA ; the action of E2 endonuclease resulted in double-strand DNA cleavage to fragments heterogeneous in size. Both endonucleases were inhibited by ATP. The inhibitory effect of actinomycin D (AD) was proportional to the AD/DNA molar ratio. AD+ATP association as well as the presence of ethidium bromide altered the cleavage pattern of E1 towards the predominance of single-strand breaks.

Adenosine Triphosphate↗
PubMed1978

Visualization of mouse DNA transcriptional complexes in mouse kidney cells infected with SV 40 virus.

Electron microscopic studies of transcribed cellular deoxynucleoprotein (DNP) fibers from mouse kidney cells abortively infected with Simian Virus 40 (SV 40) revealed two types of transcriptional complexes. Tandemly repeating units representing ribosomal transcriptional events, although few in number because of the procedure employed, clearly confirmed results of other techniques which revealed the unusually long length of the untranscribed spacer intercepts in mouse nucleolar chromatin. In non-nucleolar arrays the density of the ribonucleoprotein (RNP) fibrils varied, as did the length and configuration of the associated DNP fibers. A statistical correlation between a "smooth" appearance of a transcribed portion of a DNP fiber and a high density of nascent RNP fibrils was observed.

Animals↗
PubMed1979

Responses of immune and nonimmune adult rhesus macaques (Macaca mulatta) to adenovirus SV-20.

Adenovirus SV-20 (ASV-20) was inoculated subcutaneously into adult rhesus macaques (Macaca mulatta), and various immunologic parameters were studied. Similar changes were observed in macaques that had anti-ASV-20 serum-neutralizing antibodies prior to inoculation and in those lacking detectable antibodies. There were absolute decreases in numbers of peripheral blood lymphocytes (PBL), erythrocyte-rosetting lymphocytes, complement-receptor lymphocytes, and Fc-receptor lymphocytes. These changes were most significant (P less than 0.05) on postinoculation days (PID) 3 and 7. Mitogenic responsiveness to concanavalin A, phytohemagglutinin, and pokeweed mitogen in cultured PBL from immune and nonimmune macaques was depressed on PID 3, 7, and 14. Ultraviolet-inactivated ASV-20 caused moderate suppression of phytohemagglutinin-induced mitogenesis when viral particles and lectin were added simultaneously to PBL cultures. Plasma cortisol (hydrocortisone) values were not significantly altered following inoculation of ASV-20. High titers of anti-ASV-20 antibody developed by PID 7 in nonimmune macaques, and previously immune macaques showed a booster effect in the same time period. Antibody titers were still increased 120 days after inoculation. There was no clinical evidence of an adverse effect of ASV-20 infection in these macaques.

Adenoviridae↗
PubMedDate not supplied

[Comparison of the conformation of RNA from phage MS2 and 16S rRNA. Accessibility to nucleases S1 and SV specific to secondary structure and thermal stability].

The hydrolysis of E. coli 16S rRNA by nucleases specific to the secondary structure elements (S1 and SV), the melting of the RNA after partial hydrolysis by nuclease S1 and the electrophoretic mobility of hydrolysis products after denaturation-renaturation of RNA were studied. It was shown that the sensitivity of 16S rRNA to nuclease S1 depends on Zn or Mg ions concentration. The melting curves after partial hydrolysis by nuclease S1 were characterized by a decrease of the hyperchromic effect (by approximately 15%) and by a increase of Tm (by 3 degrees). After RNA denaturation followed by slow or fast renaturation the electrophoretic patterns of the hydrolysis products were not changed, as in the case of phage MS2 RNA. It was supposed, that the rRNA molecule has a stable "nucleus" (or "nuclei"), which is organized as an intramolecular association of parallelly oriented double-stranded fragments of this RNA. Previously, such a mode of the spatial organization was proposed by us for phage MS2 RNA.

Coliphages↗
PubMed1989

Structure-activity relationships in 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives.

New 4-deoxyhalogenopyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives (V-VIII) have been prepared as an extention of a program which led to the synthesis of analogous pyrido- and alkylpyrido compounds (I-IV) displaying a low level of g.i. absorption. The new compounds give comparatively much lower ED50 p.o./s.c. ratios showing a recovery in the extent of oral absorption. XPS, N.M.R., and HPLC data rationalize this activity in hydrophilicity due to the electron-withdrawing inductive effect of the halogen atoms bound to the pyridoimidazo system. This effect is exerted in particular on the negatively charged N(2'), and is the opposite as that exerted by the alkyl groups present in (I-III).

Bacteria↗
PubMed1985

Characterization and identification of the hyaluronate binding site from membranes of SV-3T3 cells.

Previous research has shown that binding sites for hyaluronate are present on the surfaces of a number of different cell types. To further characterize these binding sites, membranes were prepared from SV-3T3 cells and dissolved in a solution of sodium deoxycholate. Hyaluronate binding activity was detected by mixing the sodium deoxycholate extract with [3H]hyaluronate and then adding an equal volume of saturated (NH4)2SO4, which precipitated the binding protein and any [3H]hyaluronate associated with it, but left free [3H]hyaluronate in solution. Following partial purification by hydroxylapatite chromatography, the binding site was examined by molecular sieve chromatography and by rate-zonal centrifugation, which revealed that it has a Stokes radius of 6.5 nm and a sedimentation coefficient of 4.8 S. From these values, it was possible to calculate that the sodium deoxycholate-solubilized binding site has a frictional coefficient of 1.87 and a molecular weight of 132,000. Since this latter value applies to the complex of both detergent and protein, the binding protein by itself must have a molecular weight lower than 132,000. To determine the molecular weight of the hyaluronate binding site itself, the protein was purified by the sequential application of hydroxylapatite chromatography, molecular sieve chromatography, rate-zonal centrifugation, and finally lectin-affinity chromatography on concanavalin A-agarose. Analysis of the purified material by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed an 85,000 Mr protein which has been identified as the binding site. This protein was also detected on nitrocellulose blots which had been specifically stained for concanavalin A binding material, suggesting that the binding site is a glycoprotein.

Animals↗
PubMed1987

[Biosynthesis and secretion of collagen in normal and SV-40 virus-transformed human embryonal fibroblasts].

The biosynthesis and secretion of collagen proteins was studied in cultures of normal human embryo fibroblasts at different passages and growth stages as well as in cultures of human embryo fibroblasts transformed by oncogenic virus SV-40. It was found that normal fibroblasts maintain at a constant level the collagen synthesis throughout 20 passages, which is typical of proliferating and resting cells. Virus-transformed cells produce 3-4 times less collagen proteins on a per cell count. Normal and transformed fibroblasts do not differ in terms of total protein synthesis. Secretion of collagen and non-collagen proteins in transformed cell cultures appeared to be much lower than in normal cell cultures. Study of synthesized proteins by polyacrylamide gel electrophoresis showed that both types of cells secrete collagen proteins predominantly as polymers containing interchain S-S bonds of 3-helix molecules. Study of the protein-synthesizing activity of two polysomal fractions, i.e. membrane bound and free polysomes, isolated from the cells of both types in a cell-free system showed that membrane-bound polysomes from transformed fibroblasts synthesize collagen much less actively in comparison with normal cells. However, in transformed cells free polysomes, in contrast with normal cells, are active participants of a cell-free collagen protein synthesis.

Cell Line↗
PubMed1987

[Preclinical research on drug forms containing rifamycin SV intended for intramammary use].

It was established, that LD50 of rifamycin SV--sodium salt, produced by the Research Institute on Microbiological Industry--Razgrad (People's Republic of Bulgaria)--RM, at p.o. applying on albino mice, albino rats and broilers is correspondingly greater than 4100.0 mg/kg m., greater than 5740.0 mg/kg m. and 1951.6 (1355.5 divided by 2810.1) mg/kg m. and at s. c. introducing into albino mice--815.9 (756.9 divided by 879.9) mg/kg m. From the prepared on the basis of RM-4 intramammary medicaments--RM-1, RM-2 and RM-3 for lactating cows and RM-4 for cows in the dry period, a good bearing have RM-1, RM-3 and RM-4. RM-1, RM-2 and RM-3, applied intracisternally a single time on lactating cows, and RM-4 on cows in the dry period, create antimicrobial levels with duration correspondingly 168, 72 and 48 h, and 35 days. RM almost does not penetrate in the neighbouring not treated quarters. Appropriate medicament for the lactating cows with average duration of emission is RM-3 (term of action 96 h) and for cows in the dry period RM-4 when applied 35 days before the calving.

Animals↗
PubMed1985

A study of structure-activity relationships in 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives by electron spectroscopy for chemical analysis and 1H NMR.

A new class of rifamycins, 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives, has been synthesized. They are potent antibacterial agents and are not absorbed at the gastrointestinal level and can therefore probably be used as antibacterial intestinal disinfectants. From the present X-ray, electron spectroscopy for chemical analysis, and 1H NMR study, it appears that this peculiar pharmacokinetic behavior is mainly to be attributed to the fact that the pyridoimidazo system exists in these compounds in a mesomeric betaine form, bearing one positively and one negatively charged nitrogen. If it is assumed that rifamycins are generally absorbed by passive diffusion, the presence of the two oppositely charged nitrogens, together with the presence of the phenolic hydroxyls, means that these molecules are ionized at all pH values encountered along the gastrointestinal tract, which thus prevents their absorption. These molecules also display a strong tendency to self-associate both in solution and in the solid state, and the increase in molecular size may also play a role in preventing their absorption.

Magnetic Resonance Spectroscopy↗
PubMedDate not supplied

The effect of pyrogen induced fever on pharmacokinetics of rifamycin SV.

The fever was evoked in rabbits by single iv injection of pyrogen-standard from E. coli, and rifamycin SV was administered at the peak of the fever (T = 1.7 degrees C). The rifamycin blood level was determined during the fever stability and changes of kinetics of the antibiotic were investigated. It was found that distribution and elimination of rifamycin were decreased during fever. The consequence of the inhibition of the antibiotic elimination was the increase of its level in blood and tissue compartments.

Animals↗
PubMedDate not supplied

Effect of some peptides on distribution of rifamycin SV in rabbits.

The effect of insulin, glutathione, trypsin and somatotropin on processes of distribution and elimination of rifamycin SV were investigated using pharmacokinetic analysis. It was found that the peptides, especially glutathione and trypsin, enhance the distribution of rifamycin in rabbits and cause an increase of amount of this antibiotic in the central compartment.

Animals↗
PubMed1979

[Mechanisms of detecting organic cholephilic anions in man: comparative studies on plasma depuration of rifamycin-SV. Interference of nicotinic acid and phenobarbital].

We have studied plasmatic half-life of R-SV administered alone and in association with nicotinic acid, before and after treatment with phenobarbital, in 10 normobilirubinaemic subjects and in 10 patients Gilbert's syndrome, used like controls. Ouer results confirm the existence of some alterations of drug-metabolism produced by associated administration of other drugs, in both healthy and hyperbilirubinaemic subjects, and in these one even more.

Adolescent↗
PubMed1979

[Influence of phenobarbital on hyperbilirubinemia caused by nicotinic acid and rifamycin--SV in healthy subjects].

Ten healthy subjects have been given before and after treatment with phenobarbital the following intravenous charges: a) nicotinic acid; b) rifamicyn-SV; c) simultaneous administration of the two drugs. Along with confirmatory evidence of the wellknown increase in bilirubinaemia (prevalently unconjugated), we have observed phenobarbital to attempts partially yet significantly that effect. On the base of direct experience on rat liver, we hypothise phenobarbital to increase the pool of the Y protein carrying cholephilic organic anions into the hepatocytes.

Adult↗
PubMedDate not supplied

[Preliminary results of the use of a new derivative of rifamycin SV in the treatment of sarcoidosis].

Seven patients with advanced forms of mediastino-pulmonary sarcoidosis (involvement of the pulmonary parenchyma, and restrictive respiratory syndrome), confirmed by histopathologic investigation, have been treated with a new SV-rifamycin derivative, 1246-EH, or "Reprimum" without any other association. Reprimun was given in daily doses of 10 mg/kg of body weight for a period of two weeks, then, for another 4-5 weeks, the drugs was given intermittently in doses of 15 mg/kg of body weight twice weekly. Between two cycles of therapy a period of 14 days was free of drug administration. In all patients the treatment with the new derivative was well tolerated. The treatment was not followed by adrenal deficiencies, neither was noted obesity, bone decalcification, gastric ulcers, etc., which are commonly associated with prolonged corticoid therapy. The treatment with "Reprimun" efficient for all patients. A clear clinical and X-ray improvement was noted after the first three months of treatment with the new drug. Respiratory function, as well as clinical and radiological signs improved, the serum immunologic parameters, and the biochemical ones were also significantly improved (Ig, C3 total serum proteins and gammaglobulins). All parameters which were tested were finally improved and became normal. In only two of the seven patients the radiological aspects of the lung suggested the presence of sequellae at the end of the treatment. In these two patients there was a persistant reduction in the respiratory volume, as well as a discret hypoxemia. However, both these patients had a more advanced form of the disease, with extensive pulmonary fibrosis, and in these cases prolonged corticoid therapy which had previously been applied had failed. Reprimun had an immunological-modulatory effect in all patients, resulting in normal levels of IgG, IgA, and C3 in the first three months of therapy. There was a direct correlation between the normalization of immunological indicators and the good evolution of the diseases, a fact which suggests once again the existence of some immune mechanisms involved in the maintenance of sarcoidosis.

Adult↗