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Biomedical subjects

M Kalman

Publications and source records attributed to M Kalman.

14 recordsLinked to original sources
PubMed1998

Implementing teleradiology in a private radiology practice: lessons learned.

The private practice of radiology deals with the delivery of high quality, timely service to referring physicians. Technology offers the promise of supporting this objective through faster reading of studies through electronic imaging and the delivery of results in a fast, efficient manner. In order to be successful, the practice must clearly define its objectives, understand its fundamental business processes and select a technology solution that is proven to meet those objectives.

Contract Services↗
PubMed1995

Heat-tolerant methanotrophic bacteria from the hot water effluent of a natural gas field.

Methanotrophic bacteria were isolated from a natural environment potentially favorable to heat-tolerant methanotrophs. An improved colony plate assay was developed and used to identify putative methanotrophic colonies with high confidence. Fourteen new isolates were purified and partially characterized. These new isolates exhibit a DNA sequence homology of up to 97% with the conserved regions in the mmoX and mmoC genes of the soluble methane monooxygenase (MMO)-coding gene cluster of Methylococcus capsulatus Bath. The copper regulation of soluble MMO expression in the same isolates, however, differs from that of M. capsulatus Bath, as the new isolates can tolerate up to 0.8 microM copper without loss of MMO activity while a drastic reduction of MMO activity occurs already at 0.1 microM copper in M. capsulatus Bath. The isolates can be cultivated and utilized at elevated temperatures, and their copper- and heat-tolerant MMO activity makes these bacteria ideal candidates for future biotechnological use.

Amino Acid Sequence↗
PubMed1994

Effect of phytohaemagglutinin on CD45 in T cells.

In this study the effect of PHA activation on the phosphatase activity of CD45 has been investigated in human leukemic T-cell lines. It has been found that in vivo activation of the cells with PHA resulted in 2-4-fold increase in enzyme activity. Addition of PHA to the postnuclear supernatant of cell lysates also resulted in elevation of phosphatase activity. Elevation of enzyme activity resulted from an increase in the amount of antigen in the immunoprecipitates. Elevation of the quantity was not the result of a de novo protein synthesis since the presence of cycloheximide, a protein synthesis inhibitor, did not modulate the effect of PHA. The effect of PHA was specific since ConA, that also bound to the CD45 molecules, or crosslinking of the antigen by antibody did not affect CD45. Since direct binding of PHA to CD45 molecules was shown in immunoblotting analysis, we suggest that the effect of PHA is a consequence of a PHA-induced conformational change of CD45 that results in up-regulation of the analyzed CD45 epitopes.

Humans↗
PubMed1992

The nucleotide sequence of recG, the distal spo operon gene in Escherichia coli K-12.

A gene is identified in the Escherichia coli K-12 spo operon as recG. Previously identified genes in the spo operon were spoS, alias rpoZ, encoding the omega (omega) subunit of RNA polymerase, as well as the spoT gene encoding the major cellular source of guanosine 3',5'-bispyrophosphate hydrolase activity. The gene order within the spo operon is: spoS (rpoZ), spoT, spoU, recG. A convergent gltS gene is present beyond the spo operon. Mutants bearing recG deletion-insertion alleles display mild sensitivities to both ultraviolet irradiation and to mitomycin C, which is expected to be due to a known recG insertion allele. Deletion-insertion mutations in upstream operon genes (spoT and spoU) show polar effects on these assays of recG function. The deduced 693-amino acid (aa) RecG sequence shows a weak, but significant, relatedness to aa sequence motifs previously reported for putative helicases involved in replication, recombination, and DNA repair.

Amino Acid Sequence↗
PubMed1991

Residual guanosine 3',5'-bispyrophosphate synthetic activity of relA null mutants can be eliminated by spoT null mutations.

It was known previously that 1) the relA gene of Escherichia coli encodes an enzyme capable of guanosine 3',5'-bispyrophosphate (ppGpp) synthesis, 2) an uncharacterized source of ppGpp synthesis exists in relA null strains, and 3) cellular degradation of ppGpp is mainly due to a manganese-dependent ppGpp 3'-pyrophosphohydrolase encoded by the spoT gene. Here, the effects of spoT gene insertions and deletions are compared with analogous alterations in neighboring genes in the spo operon and found to be lethal in relA+ strains as well as slower growing in relAl backgrounds than delta relA hosts. Cells with null alleles in both the relA and spoT genes are found no longer to accumulate ppGpp after glucose exhaustion or after chelation of manganese ions by picolinic acid addition; the inability to form ppGpp is reversed by a minimal spoT gene on a multicopy plasmid. Strains apparently lacking ppGpp show a complex phenotype including auxotrophy for several amino acids and morphological alterations. We propose that the SpoT protein can either catalyze or control the alternative pathway of ppGpp synthesis in addition to its known role as a (p)ppGpp 3'-pyrophosphohydrolase. We favor the possibility that the SpoT protein is a bifunctional enzyme capable of catalyzing either ppGpp synthesis or degradation.

Alleles↗
PubMed1991

Characterization of the Escherichia coli K12 gltS glutamate permease gene.

The gltS gene is known to encode a sodium-dependent, glutamate-specific permease. We have localized the Escherichia coli K12 gltS gene with respect to the spoT gene, sequenced it, and recombined a null insertion-deletion allele into the chromosome without loss of viability. The gltS null allele gives a Glt- phenotype, i.e. it abolishes the ability of a gltCc host to grow on glutamate as sole carbon and nitrogen source and also confers alpha-methylglutamate resistance. A multicopy plasmid expressing the gltS gene can reverse the Glt- phenotype of gltS- or wild-type strains while other plasmids show host-dependent complementation patterns. Induction of gltS gene overexpression under control of isopropyl-beta-D-thiogalactoside (IPTG)-inducible promoters severely inhibits growth. The GltS protein is deduced to be a 42425 dalton hydrophobic protein with 2 sets of 5 possible integral protein domains, each flanking a central hydrophilic, flexible region.

Alleles↗
PubMed1991

Conversion of single-stranded oligonucleotides into cloned duplexes and its consecutive application to short artificial genes.

A general method to convert single-stranded, chemically synthesized oligonucleotides into cloned duplexes is described. Oligonucleotides supplied with 3'-terminal extensions that are complementary to 3'-protruding ends obtained by certain restriction enzymes can be cloned either directly or with the help of an adapter molecule into double-stranded vectors. Two methods have also been developed for consecutive cloning applications. According to these methods, the synthetic oligonucleotides (and their enzymatically prepared complementary strands) are joined, one after the other, inside a cloning vector, each joining requiring one cloning step. Synthetic genes are thus built up from oligonucleotides corresponding to only one strand of the DNA. The sequential assembly of the cloned duplex takes place in the 5' to 3' direction. Each oligonucleotide is supplied with a four-nucleotide-long 3'-terminal extension, but this sequence is eliminated when the joining takes place, leaving no limiting sequence between the oligonucleotides. The two consecutive cloning methods, the adapter and the polycloning site methods, are illustrated by the assembly of short artificial genes.

Amino Acid Sequence↗
PubMed1991

rhlB, a new Escherichia coli K-12 gene with an RNA helicase-like protein sequence motif, one of at least five such possible genes in a prokaryote.

A newly recognized gene we name rhlB, after RNA helicase-like genes, has been found in the 85-minute region of the Escherichia coli chromosome. This gene encodes protein sequence motifs similar to those known for "D-E-A-D box" gene products. Proteins in this gene family occur in eukaryotes as well as prokaryotes, and, as far as tested, have been found to participate in ATP-dependent RNA helicase or RNA-dependent ATPase activities. The functions of these enzymes are poorly understood. In yeast, mutant phenotypes of various D-E-A-D genes suggest that they function in RNA splicing, processing, or translation. We find that rhlB is necessary for viability only in some genetic backgrounds. Conditional rhlB lethality is not complemented by another E. coli RNA helicase-like gene (srmB). Using primers with homology to consensus sequences in D-E-A-D box proteins, we have recovered DNA fragments amplified from E. coli genomic DNA by polymerase chain reactions. Sequence analysis of these fragments suggests that E. coli possesses at least five RNA helicase-like (rhl) D-E-A-D box genes at widely separated chromosomal locations. The multiplicity of such genes in a prokaryote raises the possibility of important roles for the corresponding class of biologically widespread proteins.

Amino Acid Sequence↗
PubMed1989

Characterization of the spoT gene of Escherichia coli.

The Escherichia coli spoT gene encodes a guanosine-3',5'-bispyrophosphate (ppGpp) 3'-pyrophosphohydrolase known to be responsible for cellular (ppGpp) degradation. The DNA sequence of the spoT region is presented. The spoT gene is deduced to be 702 codons long, with a probable UUG initiation codon, and a deduced mass of 79,342 daltons. Two spoT mutations (spoT202 and spoT203) have been localized to an open reading frame by complementation of function as well as by genetic marker rescue. The ability to overexpress the spoT gene is limited, but enough ppGppase activity can be made to reverse ppGpp accumulation during the stringent response to amino acid starvation. The spoT gene is located within a larger spo operon and is flanked by two smaller genes. The first gene in the operon encodes omega, a protein that copurifies with RNA polymerase (Gentry, D. R., and Burgess, R. R. (1986) Gene (Amst.) 48, 33-40). The spoT gene is the second gene in the operon; it is followed by a third open reading frame deduced to encode a protein with a mass of 25,343 daltons. Insertion of a kanamycin resistance gene in the omega gene reduces spoT gene expression as judged by lowered ppGppase activity, relA-dependent reduction of growth rate, and abolition of spoT mutant complementation activity. These effects are reversed by expression of the spoT gene, but not the omega gene, in trans. Transcription of the spo operon occurs in a clockwise direction on the E. coli chromosome and is probably directed by at least two promoters.

Alleles↗
PubMed1989

[3H]naloxone binding in the brain of the domestic chick (Gallus domesticus) determined by in vitro quantitative autoradiography.

The distribution of [3H]naloxone binding sites was investigated in the brains of one-day-old domestic chicks using quantitative receptor autoradiography. Among the forebrain regions, the greatest levels of opiate binding were found in hyperstriatum dorsale, hyperstriatum ventrale, hyperstriatum intercalatum supremum and neostriatum. Intermediate levels were found throughout the paleostriatal regions, septum, thalamus, archistriatum, hyperstriatum accessorium and area parahippocampalis whilst in hippocampus and ectostriatum the density of [3H]naloxone binding sites was low. In the hindbrain, high levels of opiate binding were found in optic tectum whereas in cerebellum the density of binding sites was barely above background. The greatest densities of opiate binding appear to coincide with regions found to be involved in sensory processing and memory storage.

Animals↗
PubMed1988

Synthesis, cloning and expression in Escherichia coli of artificial genes coding for biologically active elongated precursors of the vasoactive intestinal polypeptide.

Synthetic genes coding for elongated precursors of the vasoactive intestinal polypeptide (VIP) were synthesized and cloned in a highly efficient Escherichia coli expression vector. The synthetic genes code for VIP with its methionine (at position 17) replaced by leucine and elongated at the C-terminus by Gly (vasoactive intestinal polypeptide-Gly, i.e. VIPa) or by Gly-Lys-Arg (vasoactive intestinal polypeptide-Gly-Lys-Arg, i.e. VIPb). The synthetic genes fused to the N-terminal part of the E. coli beta-galactosidase gene were expressed to yield high amounts of fusion proteins reaching upon induction at least 60% of the total cellular protein. The fusion proteins of 314 and 316 amino acids carrying in their C-terminal portion either the 29 or 31 amino acids long VIP precursor polypeptide were shown to be immunoreactive with VIP antisera and were further purified and cleaved by CNBr. The resulting purified peptide precursors (VIPa and VIPb) were recognized by VIP receptors in rat liver plasma membranes and by antibodies to porcine VIP in a radioimmunoassay. Both precursors activated adenylate cyclase in rat liver membranes and stimulated pancreatic secretion in the cat. The affinity and potency of the cloned precursors is close to that of VIP purified from porcine intestine, suggesting that the elongated VIP precursors may act even without being converted into the C-terminal amide form of the peptide. The elongated VIP precursors expressed in E. coli may provide a cheap, large-scale source of experimental material for studies on VIP actions.

Amino Acid Sequence↗
PubMed1988

Quantitative autoradiographic analysis of the distribution of [3H]muscimol binding to GABA receptors in chick brain.

Quantitative receptor autoradiography was used to investigate the distribution of high-affinity GABA receptors (GABAA) in left and right hemispheres of the brains of 3-week-old chicks. The receptors were labelled with the potent GABA agonist [3H]muscimol. High levels of [3H]muscimol labelling were found throughout the fore-, mid-, and hindbrain, though considerable variation was found in different regions. In the telencephalon the highest concentration of specific binding was found in the hyperstriatum ventrale followed by the neostriatum, and then the lobus parolfactorius of the paleostriatal complex, whilst in the diencephalon highest levels of labelling were present in the infundibulum. In the midbrain distinct lamination was observed in the high levels of [3H]muscimol binding in the optic tectum and in the hind brain the highest density of labelling occurred in the granular layers of the cerebellum. Levels of labelling were generally low in the brainstem regions. The distribution of [3H]muscimol binding in the optic tectum and in the hind brain the highest density of labelling occurred in the granular layers of the cerebellum. Levels of labelling were generally low in the brainstem regions. The distribution of [3H]muscimol binding sites is in good agreement with our previous work on the distribution of GABA-immunoreactivity in the chick brain.

Animals↗