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Biomedical subjects

T Shibata

Publications and source records attributed to T Shibata.

At least 1,099 records · Page 61Linked to original sources
PubMed1979

Single strands induce recA protein to unwind duplex DNA for homologous pairing.

Single-stranded DNA, whether homologous or not, stimulates purified Escherichia coli recA protein to unwind duplex DNA. This helps to explain how recA promotes a search for homology in genetic recombination. As oligodeoxynucleotide also stimulate unwinding, a common mechanism may relate the function of recA protein in recombination to other functions (SOS) induced by oligonucleotides.

Adenosine Triphosphate↗
PubMed1979

Mapping of genes determining nonpermissiveness and host-specific restriction to bacteriophages in Bacillus subtilis Marburg.

Bacillus subtilis Marburg is nonpermissive for the multiplication of bacteriophages SP10 and phi NR2. A permissive mutant was derived from the Marburg strain, and the genetic determinants of non-permissiveness were analyzed by PBS1 transduction. The simultaneous presence of two genes as mutant alleles, nonA and nonB, was necessary for permissiveness. The gene nonA is linked very closely to rfm (cotransfer: 95%); nonB is located between dal and purB (cotransfer of nonB and purB6 : 48%). The genetic determinant of host-specific restriction intrinsic to the Marburg strain (hsrM) was found to be identical or very closely linked to nonB. The segregation on nonB and hsrM has never been observed in the course of transduction analysis. The mutation, hsrM1, diminishes the restriction activity, but not the host-controlled modification.

Bacillus subtilis↗
PubMed1979

Host-controlled modification and restriction in Bacillus subtilis: Bsu 168-system and BsuR-system in B. subtilis 168.

A Bsu168-specific restriction deficient (r168-) mutant of Bacillus subtilis Marburg 168 was transformed to be BsuR-specific restriction proficient (rR+) with B. subtilis R DNA as efficiently as the Bsu 168-specific restriction proficient (r168+) parental strain (hsrM+, hsdR-). We constructed rR+ mR+ r168+ m168+ strain (ISMR 4), rR+ mR+ r168- m168+ strain (ISR 11) and rR+ mR+ r168- m168- strain (ISR 6) from strain 101 (r168+ m168+), strain 1012 (r168- m168+) and strain RM125 (r168- m168-), respectively by transformation with B. subtilis R DNA, and tested their restriction and modification activities on phage phi 105C. The results show that the sites recognized by Bsu168-specific restriction and modification enzymes and the sites recognized by BsuR-specific ones are not overlapping. We conclude that the Bsu168-modification and restriction system and the BsuR-modification and restriction system are controlled independently by two distinct sets of genes in the rR+ mR+ transformant of r168+ m168+ strain B. subtilis 168.

Bacillus subtilis↗
PubMed1979

Homologous pairing in genetic recombination: complexes of recA protein and DNA.

recA protein, which is essential for general genetic recombination in Escherichia coli, promotes the homologous pairing of single-stranded DNA with double-stranded DNA to form a D loop. The amount of recA protein required for the reaction was directly proportional to the amount of single stranded DNA and was unaffected by similar variations in the amount of double-stranded DNA. The ATP analog, adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), which was not rapidly hydrolyzed by recA protein, blocked the formation of D loops but promoted the formation of stable complexes of recA protein and single-stranded DNA. These complexes, in turn, bound homologous or heterologous double-stranded DNA and partially unwound it. Because ATP gamma S competitively inhibited the ATPase activity of recA protein (Km/Ki approximately 300), we infer that ATP gamma S binds at a site that overlaps the site for ATP and that the functional complexes formed in the presence of the analog probably represent partial steps in the overall reaction. If the complexes formed in the presence of ATP gamma S reflect natural intermediates in the formation of D loops, recA protein must promote homologous pairing either by moving juxtaposed single-stranded and double-stranded DNA relative to one another or by forming and dissociating complexes reiteratively until a homologous match occurs.

Adenosine Triphosphatases↗
PubMed1979

Purified Escherichia coli recA protein catalyzes homologous pairing of superhelical DNA and single-stranded fragments.

Purified Escherichia coli recA protein catalyzed ATP-dependent pairing of superhelical DNA and homologous single-stranded fragments. The product of the reaction: (i) was retained by nitrocellulose filters in 1.5 M NaCl/0.15 M Na citrate at pH 7, (ii) was dissociated at pH 12.3 but was not dissociated by heating at 55 degrees C for 4 min or by treatment with 0.2% sodium dodecyl sulfate and proteinase K, (iii) contained covalently closed circular double-stranded DNA (form I DNA), (iv) contained single-stranded fragments associated with replicative form (RF) DNA, and (v) contained a significant fraction of D-loops as judged by electron microscopy. Linear and nicked circular double-stranded DNA did not substitute well for superhelical DNA; intact circular single-stranded DNA did not substitute well for single-stranded fragments. Homologous combinations of single-stranded fragments and superhelical DNA from phages phiX174 and fd reacted, whereas heterologous combinations did not. The reaction required high concentrations of protein and MgCl2. The ATPase activity of purified recA protein was more than 98% dependent on the addition of single-stranded DNA. In 1 mM MgCl2, the ability of superhelical DNA to support the ATPase activity was two-thirds as good as that of single-stranded DNA.

Adenosine Triphosphatases↗
PubMed1978

Analgesia by enkephalins injected into the nucleus reticularis gigantocellularis of rat medulla oblongata.

Methionine-enkephalin (0.2--20 microgram/rat) and leucine-enkephalin (1--20 microgram/rat) produced a dose-related and naloxone-antagonizable analgesia in the tail-pinch test, when microinjected into the nucleus reticularis gigantocellularis (NRGC) and nucleus reticularis paragigantocellularis (NRPG) of the medulla oblongata of the rat. The median analgesic doses were 1.4 and 4.8 microgram/rat for methionine- leucine-enkephalin, respectively. The possibility that the endogenous enkephalins play a part as pain control substances or modulators in the NRGC and NRPG was discussed.

Analgesics↗
PubMed1978

CT in evaluation of the circle of Willis.

The method of visualizing the circle of Willis intentionally on contrast-enhanced CT scan was studied. The incidence of circle of Willis in our series was 86%. Only mild side effects were observed, in 7.5% of cases. CT of 60 proven cerebral aneurysms were reviewed and aneurysm was detected in 57%. This method has the potential to be a noninvasive screening procedure for evaluation of suspected cerebral aneurysm, as well as evaluation of marked arteriosclerosis, occlusion of major arteries, and mass effect of parasellar tumors.

Cerebral Angiography↗
PubMed1978

Isolation and characterization of a new rubella variang with DNA polymerase activity.

A rubella variant (HPV-RV) was isolated from high passage rubella virus preparations propagated at 37 degrees C in baby hamster kidney BHK21/WI-2 cells. HPV-RV formed clear plaques in HeLa cells and primary cells of the Rhesus monkey kidney although wild type rubella virus did not produce plaques in these cells. Cells persistently infected with rubella virus were insensitive to infection by HPV-RV at both 34 degrees and 39.5 degrees C. HPV-RV agglutinated one day old chick, human group O and sheep erythrocytes. This hemagglutinating activity was inhibited by anti-BHK latent virus serum but not by anti-rubella virus serum. The plaque forming ability of HPV-RV was neutralized by anti-BHK latent virus serum although the same antiserum did not affect the plaque forming ability of wild type rubella virus. Furthermore, HPV-RV was found to have the complement fixation antigen of rubella virus and DNA polymerase activity. From these findings, it is concluded that HPV-RV is a hybrid between rubella virus and a latent virus of BHK21/WI-2 cells.

Antigens, Viral↗
PubMed1978

A study on the melanin-laden dendritic cell (melanocyte) in ovarian cystic teratoma.

To confirm the existence and to analyse the distribution of the melanocyte in cystic teratoma of the ovary, 51 cases were collected, among which 47 were found suitable for gross and histological examinations. The tissue components of cystic teratoma where the melanocyte was seen more or less associating were; the squamous, cuboidal and columnar cell epithelia especially the epidermal epithelium, the brain tissue principally the leptomeninx, and the interstitium. The frequency of melanocytes' association in the respective tissue was shown and compared between each other. One thing which was quite interesting for us was the relationship between the existence of brain tissue and the development of melanocyte in cystic teratoma. The melanocyte appeared in the above tissues, especially the interstitium, of cystic teratoma more frequently when the brain tissue was coexisting in the same tumor. These findings seem to be of meaningful suggestions concerning the melanocytogenesis not only of cystic teratoma of the ovary, but also in a physiological condition in man.

Adolescent↗