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Biomedical subjects

K Matsubara

Publications and source records attributed to K Matsubara.

At least 577 records · Page 32Linked to original sources
PubMed1975

Isolation and properties of Escherichia coli mutants which are nonpermissive for the growth of phage lambda.

By selecting survivors of lambda phage infection, mutants of Escherichia coli K12 that block reproduction cycle of the phage have been isolated. Fourteen of these phage-tolerant mutants (lam mutants) were chosen and characterized biochemically and genetically. It was shown that these mutants were tolerant to infection by all the lambdoid phages, except for few cases, but they were susceptible to infection by a non-lambdoid temperate phage (phi299), P1 or T phages. The mutants can be divided into at least three groups: (1) A mutant (lam 16) strain that seems to block normal penetration of phage DNA: (2) Three mutant (lam 64, lam 67 and lam 71) strains that block an "early" step(s) of phage growth, including phage DNA synthesis: (3) Six mutant (lam 24, lam 25, lam 26, lam 27, lam 646 and lam 6) strains that block normal functioning of the gene E products and produce unusual head structures. Some lambdoid phages and lambda mutants that overcome the interference by the lam mutations have been obtained, and were used as tools for characterizing the host mutations. Two (lam 12 and lam 13) mutant strains and one (lam 1) mutant were inferred as affecting the expression of "late" genes, and early gene, respectively, by this test.

Coliphages↗
PubMed1975

In vitro construction of different oligomeric forms of lambdadv DNA and studies of their transforming activities.

Plasmid lambdadv1, which is in a dimeric form, was converted to a linear monomer duplex by the action of EcoRI restriction endonuclease that incises at a unique site in this plasmid genome. The resulting products were then joined by Escherichia coli DNA ligase to produce molecules with various oligomeric forms, and from these monomeric, dimeric, or trimeric circular molecules were purified. By transformation of cells with these DNAs, clones were obtained that carried lambdadv1 in a monomeric or dimeric form. The former type of clones have not been generated in vivo, except for one in a different host strain, and carriers of timeric or tetrameric lambdadv1's have not been obtained so far. It was observed that a considerable fraction of these oligomeric circular DNAs were converted to lower oligomers (e.g., from trimer to dimer) during transformation. The characteristics of the monomeric lambdadv1 carriers obtained were compared with those of dimeric lambdadv1 carriers. The stabilities of the plasmids of the two forms were the same. However, the monomeric plasmid carriers were less tolerant to lambdavir phage infection and perpetuated about 30% less plasmid genomes in monomer units. Furthermore, dimeric plasmid carriers appeared spontaneously and accumulated in cultures of the monomeric lambdadv1 carriers.

Coliphages↗
PubMed1975

Intramitochondrial dense bodies in the goblet cells of the ileum of muscular dystrophic mice.

Mitochondrial osmiophilic bodies were found in the goblet cells of the small intestine in a group of muscular dystrophic mice. They were not found in any littermate normal control mice. The dense bodies were uniformly round in shape but variable in size, approximately 0.2-0.4 mu in diameter. A limiting membrane encircled a dense content. Mitochondria with such dense bodies were distributed throughout the goblet cells. Adjacent absorbing epithelial cells had none of such mitochondrial bodies. Though the site of formation of the mitochondrial bodies remains to be investigated, the Golgi complex did not appear to be involved in the transportation of the dense bodies. Digestion of sections with ether-chlorofolm (1:1) slightly decreased the density of the mitochondrial body. Ruthenium red staining was not visible over the dense bodies but trace of Ru was detected by X-ray microanalysis. X-ray microanalysis indicated very few, if any, amounts of P and Ca, and it was not probable that phospholipid and calcium binding protein were the main constitution of these dense bodies.

Animals↗
PubMed1974

[Replicon].

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Bacteria↗
PubMed1974

Preparation of plasmid lambda dv from bacteriophage lambda: role of promoter-operator in the plasmid replicon.

A technique has been described for selection of bacteria carrying plasmid lambdadv. With this technique, the effects of mutations in the promoter-operators were compared on the production and perpetuation of the plasmid. It was found that "left" promoter-operator that controls leftward gene expressions can be deleted from the plasmid genome. Some mutations of "right" promoter-operator (pRoR) that controls expression of genes tof, O, and P affect the stability of the plasmid. However, the plasmid genome accomodates a variety of pRoR mutations within a reasonable but different degree of constitutivity. Some new promoter mutations that allow bypass of the pRoR cannot be carried in the plasmid genome. From these findings it was proposed that the plasmid replicon has one indispensable promoter-operator that controls expression of all the genes related to its own replication, although a variety of constitutive mutations can be accommodated in the pRorR.

Coliphages↗
PubMed1974

Interference in bacteriophage growth by a resident plasmid lambda dv. II. Role of the promoter-operator.

The susceptibilities to interference by lambdadv of a set of lambda phages differing in the genetic structure of their right promoter-operator (pRoR) were compared. For this purpose mutant phages were added to lambdadv-carrier cells at various multiplicities, and abilities to escape from interference, as represented by percentages of infected complexes to produce progeny phages, were compared. It was observed that phages that carry strongly constitutive pRoR were able to escape from interference at a low multiplicity of infection, whereas phages with weakly constitutive pRoR were able to escape only when a large number of these genomes entered into a cell. Several mutations in the pRoR were arranged in order of their constitutivity, or ability to escape from interference. Next, the abilities of a set of lambdadv plasmids differing in their pRoR to cause interference were compared. The results showed that interference increased with increase in constitutivity of the pRoR in the plasmid genome. These observations are thought to reflect a regulatory system of the plasmid replicon, and a possible mechanism for the system is discussed.

Coliphages↗
PubMed1973

Isolation of circular DNA molecules from whole cellular DNA by use of ATP-dependent deoxyribonuclease.

A technique is described for isolation of plasmid DNA in closed and open circular double-stranded forms from bacterial cells, by use of ATP-dependent deoxyribonuclease purified from Micrococcus luteus. This DNase, acting only upon linear DNA molecules, degrades all bacterial chromosomal DNA extracted in the linear form. Circular plasmid DNAs are left intact, and are then separated by sedimentation through a sucrose gradient. Unlike previous techniques for analysis of plasmid DNA, this technique can be used to isolate not only closed circular DNA but also open circular DNA. Several plasmids, such as those from phage (lambdadv1 and lambdadv21), a colicinogenic factor (Col E2), a sex factor (F(8)' gal), and "minicircles" in Escherichia coli 15, in both the open and closed circular forms, were well separated from chromosomal DNA by this technique.

Adenosine Triphosphate↗