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P Geck

Publications and source records attributed to P Geck.

At least 37 records · Page 2Linked to original sources
PubMed1991

Identification of ATGCAT sequence at sites of SmuC I restriction endonuclease by computer and physical mapping of adenovirus type 1 DNA.

Physical mapping of adenovirus type 1 DNA was carried out in order to analyze the recognition sequence of a novel Streptococcus restriction endonuclease. In addition to the new map and homology data on this poorly analyzed serotype, the result offers the definite evidence for the ATGCAT recognition sequence on adenovirus DNA and the physical map of cleavage points.

Adenoviridae↗
PubMed1990

Expression of collagenlike sequences by a tumor virus, herpesvirus saimiri.

Sequencing demonstrates that the oncogenic regions of a group A strain and a group C strain of herpesvirus saimiri are nonhomologous. A bicistronic viral mRNA from this region is transcribed in tumor cells transformed by a highly oncogenic group C virus. The first open reading frame is homologous to collagen; no such sequences were found in group A or B strains. This is the first report that a virus encodes for sequences similar to those of a connective tissue protein.

Base Sequence↗
PubMed1989

Arrangement of repetitive sequences in the genome of herpesvirus Sylvilagus.

Herpesvirus sylvilagus is a lymphotropic (type gamma) herpesvirus of cottontail rabbits (Sylvilagus floridanus). Analysis of virion DNA of herpesvirus sylvilagus has revealed that the genome consists of one stretch of about 120 kilobase pairs of internal, unique DNA flanked by a variable number of 553-base-pair tandem repeats. The G + C content of the repetitive DNA is extremely high (83%), as determined by sequencing. The organization of the herpesvirus sylvilagus genome is, therefore, similar to that of the primate lymphotropic viruses herpesvirus saimiri and herpesvirus ateles.

Base Sequence↗
PubMed1989

Herpesvirus saimiri strains from three DNA subgroups have different oncogenic potentials in New Zealand white rabbits.

Herpesvirus saimiri is a primate tumor virus that induces acute T-cell lymphomas in New World monkeys. Strains of this virus have been previously classified into three groups on the basis of extreme DNA variability of the rightmost region of unique L-DNA. To compare the oncogenic potentials of various strains, we inoculated New Zealand White rabbits with viruses representing groups A, B, and C of herpesvirus saimiri. The results showed that a group C strain were highly oncogenic in New Zealand White rabbits; however, group A or B viruses were not oncogenic in these rabbits. Analysis of DNAs of tumor tissues and lymphoid cell lines established from tumors showed that the viral genome exists in circular episomal form. To identify which part of the genome of the group C strain is responsible for the highly oncogenic phenotype, group B-C recombinant strains were constructed by an efficient drug selection technique. Two group B recombinant strains in which the right-end 9.2 kilobase pairs of unique DNA is replaced by group C virus DNA were oncogenic in rabbits, indicating that the rightmost sequences contribute to the oncogenic properties of the group C strain. Oncogenicity of herpesvirus saimiri has been traditionally evaluated in New World monkeys; infection of rabbits with group C strain 484-77 offers a much more accessible animal model to study the mechanism of oncogenicity of this virus.

Animals↗
PubMed1988

Density-related changes of potassium (86Rb) uptake by amphibian endothelial cells.

Potassium influx has been investigated in XTH-2 cells, a line derived from tadpole heart endothelia. In this line, the density at which the cultures become confluent is clearly separated from the density at which growth arrest takes place. Density-related changes in K+ influx were monitored by determining the uptake of 86Rb into well adhering cells kept in culture medium. The main observations were 1) 86Rb uptake is highest in single cells, and on confluency it reaches a low level, which is kept constant at higher cell density regardless of whether the cultures are stationary or still in logarithmic growth phase; 2) the relative amount of 86Rb taken up via the Na+ -K+ -2Cl- cotransport pathway and via the Na+/K+ pump changes from low cell density to confluent cultures; 86Rb uptake of single cells is nearly insensitive to ouabain, a maximum of ouabain sensitivity is reached around confluency, whereas piretanide-sensitive 86Rb uptake is highest in single cells and seems to reach a minimum at the onset of confluency; 3) the variations in Na+/K+ pumping rate reflect neither differences in the amount of enzyme present nor changes in enzyme repartition between apical and basolateral plasma membranes; they seem to result from either "masking" or "unmasking" of the enzyme; 4) no alterations in K+ uptake occur that would be characteristic of the "stationary growth phase." The only changes that seem to be related to arrest of proliferation are concerned with the Na+/K+-ATPase, which achieves an extraordinary susceptibility to stimulation by monensin and exhibits an increase in PNPPase activity.

Animals↗
PubMed1987

Elimination of non-specific nucleases from restriction endonuclease preparations by different binding on free DNA ligand.

In the purification of a novel restriction endonuclease (an AvaIII isoschizomer, isolated in this laboratory) standard methods were insufficient to eliminate non-specific nuclease contaminations. Taking advantage of the specific site recognition and binding of the restriction endonuclease on DNAs, a method is described for the simple extraction of non-specific nucleases. DNA substrates without recognizable sites do not bind the restriction endonuclease, while non-specific nucleases are absorbed to, and eliminated with, the DNA via gel filtration chromatography under special conditions.

Binding, Competitive↗
PubMed1986

Inhibition of ion transport in Ehrlich cells by muzolimine.

The influence of muzolimine on the transport of Na+, K+ and Cl- was studied in Ehrlich cells to test whether the diuretic inhibits the furosemide-sensitive Na+-K+-2 Cl-(-)cotransport or transport via the ouabain-sensitive Na+/K+-pump. It was shown that between 10(-5) M and 10(-3) M muzolimine pump-flux decreases with increasing drug concentration (IC50 about 0.5 mM), in contrast to the unaffected cotransport. This reduction in pump rate is only seen with respiring cells, but not during glycolytic ATP-production. Therefore, muzolimine seems to inhibit the Na+/K+-pump not directly but indirectly by interference with energy metabolism resulting in decreased ATP concentration. This reduction in ATP-level is at least partially due to activation of an ATP-consuming process of unknown nature. Whether muzolimine also inhibits respiration was not tested.

Adenosine Triphosphate↗
PubMed1986

New aspects of cellular thallium uptake: Tl+-Na+-2Cl(-)-cotransport is the central mechanism of ion uptake.

Cellular uptake mechanisms of 201Tl+ were studied in Ehrlich mouse ascites tumor cells. 201Tl+ passes the cell membrane of tumor cells using three transport systems: the ATPase, the Tl+-Na+-2Cl(-)-cotransport, and the Ca++-dependent ion channel. In the case of 201Tl+ the main route for entering the cells was the cotransport, its importance increasing with the age of the cells; in parallel, the ATPase activity was reduced. In contrast, the transport capacities of the ATPase and the cotransport were of the same magnitude in the case of 42K+ and 86Rb+. This change in ion distribution was not brought about by varying velocity relations but by changing the number of transport systems in the cell membrane. There was no relationship between transport rates and diameters of the ions. 201Tl+ distribution is proportional to that of K+ with a higher intracellular concentration of about 30%. Under physiological conditions the cotransport was reversible suggesting the ability to regulate steady state during varying extracellular ion concentrations. Cells and medium were two compartments, kinetically seen. Due to the significant difference of transport capacities between the three systems with the respective ions the term "potassium-thallium-analogy" may be misleading as it erroneously assumes identical uptake conditions.

Adenosine Triphosphatases↗
PubMed1985

Na+ + K+ + 2Cl- cotransport in animal cells--its role in volume regulation.

Cell membranes of various vertebrate cells catalyze a Na+ + K+ + 2Cl- cotransport specifically inhibitable by furosemide and other high ceiling diuretics. The energetics of this process is not elucidated unequivocally. It was clearly shown that cotransport is no ATP-consuming process. We assume that transport is secondary active functionally coupled to the operation of the electrogenic Na+-K+ pump. The role of this transport system in transepithelial ion movement is that it serves as flux amplifier, doubling from 6 to 12 the number of osmotically active particles transported per ATP hydrolyzed. In concert with Na+-K+ pump, cotransport provokes net uptake of KCl into the cell and therefore cellular swelling. This process is regulated by a feedback control system for cell volume; if actual volume reaches reference value, cotransport is switched off to prevent further swelling. How cell volume is measured is not known, nor is the nature of the signal generated to switch cotransport from the operating to the nonoperating state or vice versa. cAMP-level or intracellular Ca2+ play no role as signals or as part of the volume-sensoring mechanism. Theophylline, other alkylxanthines, and some purine ribosides influence cotransport indirectly by reducing reference volume. The role of cytoskeleton in volume regulation is obscure. While high Concentrations of cytochalasin B and of colchicin do not influence cell volume, it is reduced by vinblastine and also by lectins, for example concanavalin A. Volume reduction is accompanied by reduction in cellular KCl content. The observation that during hypertonic incubation protein synthesis is inhibited can be traced back to a correlation between cell volume and protein synthesis and not to elevation of osmolarity per se. Reduction in cell volume under isotonic conditions by varying K+ and/or Cl- concentration or by furosemide inhibition of cotransport is strongly correlated to inhibition of protein synthesis. The reason for this correlation is not yet clarified. Not all cells showing furosemide-sensitive cotransport are able to regulate it, for example lymphocytes. For mammalian erythrocytes drastic species differences exist; while cells from man, rabbit, rat, and mouse all show cotransport, only cells from rat (and mouse?) are able to regulate cotransport.

Adenosine Triphosphate↗
PubMed1984

Alterations of 86Rb+ fluxes in poliovirus-infected HeLa cells and their dependence on virus replication.

Components of the 86Rb+ influx were investigated subsequent to poliovirus infection in the presence and absence of guanidine-HCl, both under normal steady-state conditions and after Na+ preloading of the cells. Measurements of the ouabain-sensitive 86Rb+ uptake indicated a biphasic change in the activity of the Na+, K+ pump in the course of virus infection: a transient increase in the second hour postinfection, that was detectable only after Na+ preloading and inhibition after 3 hr. The enhanced activity of the Na+, K+ pump was not affected, while the decrease later was fully prevented by the antiviral agent guanidine-HCl. The piretanide-sensitive 86Rb+ uptake due to the Na+, K+, 2 Cl- cotransport system also became strongly inhibited beginning in the second hour postinfection. The inhibition of this transport system was partially antagonized by guanidine-HCl. The remaining 86Rb+ influx in the presence of ouabain and piretanide increased in the third hour postinfection. The latter change in 86Rb+ influx, indicating an increased permeability to monovalent cations was completely abolished by guanidine-HCl.

Biological Transport, Active↗
PubMed1984

A reduction in the activity of the Na+, K+-pump in dimethylsulfoxide-treated Friend erythroleukemia cells is not due to partial inactivation of the Na+, K+-ATPase.

Treatment of Friend-erythroleukemia cells with 1.5% dimethylsulfoxide (DMSO) caused a decrease in ouabain sensitive 86Rb+-uptake beginning six to seven hours after DMSO addition indicating a reduced function of the Na+, K+-pump. However, analysis of the ouabain sensitive 86Rb+-uptake after Na+-preloading of the cells as well as measurements on the Na+, K+-ATPase activity in isolated membrane fragments revealed that no inhibition of the Na+, K+-ATPase occurred during the first 12 hours. On the contrary the Na+, K+-ATPase activity was initially enhanced and then returned to control levels during the early phase of induction by DMSO. On the other hand, 22Na+-transport into DMSO-treated cells was reduced similar to the ouabain sensitive 86Rb+ uptake in cells without Na+ preloading. The piretanide sensitive 86Rb+-uptake, due to the Na+, K+, 2Cl - cotransport system was inhibited after seven hours exposure to DMSO. Some three hours after DMSO addition the incorporation of 35S-methionine into proteins began to decrease, which was accompanied with or followed by a reduction in the methionine uptake of DMSO treated cells. Membrane-potential-dependent tetraphenylphosphonium cation uptake was not altered relative to the controls in the first 12 hours following DMSO addition. These results suggest that the reduced activity of the Na+, K+-pump in Friend cells after DMSO exposure is not due to inhibition of the Na+, K+-ATPase, but most probably due to a smaller Na+-influx, which results from inhibition of Na+-cotransport processes (amino acid uptake, Na+, K+, 2Cl - cotransport system).

Animals↗
PubMed1983

Concentrated, digestible DNA after hydroxylapatite chromatography with cetylpyridinium bromide precipitation.

A method for the direct extraction of the DNA from the unfavorable phosphate eluant of hydroxylapatite chromatography is described. The DNA--reversibly precipitated with the cationic detergent cetylpyridinium bromide--can be subjected to further enzymatic manipulations within minutes. This method is applied to the rapid separation of pBR322 plasmid from the chromosomal DNA.

Cetylpyridinium↗
PubMed1983

Possible causes of the loss of specific pBR322-Ad h 1 DNA recombinants following transfection.

Characteristics of pBR322/Ad h 1 DNA recombinants were studied which had been cloned using HindIII restriction endonuclease in a single "shot-gun" experiment. Both oxytetracycline and ampicillin resistance of the clones were found to be heterogeneous. Ad h 1 DNA fragments HindIII-A, and -C could be cloned only in combination with other fragments. Among the possible reasons of the loss of recombinants upon transfection the impairment of pBR322-specific gene functions by the inserts is discussed in addition to the increased tetracycline resistance, and the tertiary structure of recombinant DNA.

Adenoviruses, Human↗