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J Collins

Publications and source records attributed to J Collins.

At least 415 records · Page 23Linked to original sources
PubMed1978

The expression of tetracycline resistance after insertion of foreign DNA fragments between the EcoRI and HindIII sites of the plasmid cloning vector pBR 322.

In vitro recombination techniques were used to construct hybrid plasmids between pBR 322 and different DNA fragments derived from pML 21 and the E. coli chromosome. Some of the resulting hybrid plasmids express the tetracycline resistance gene of pBR 322, depending on the DNA fragment which has been ligated into the HindIII-site of pBR 322. From these studies we could conclude the direction of transcription of the kanamycin resistance gene in plasmid pML 21 with respect to the SalI, SmaI, HincII, KpnI, EcoRI and HindIII restriction sites. The replacement of the small HindIII-EcoRI-fragment in pBR 322 by other DNA fragments from the E. coli chromosome and selection for tcr-phenotypes showed that this system may be very useful for screening and analysis of promotor-containing DNA fragments.

DNA, Bacterial↗
PubMed1978

A ribosomal RNA gene, rrnC, of Escherichia coli, mapped by specialized transducing lambdadilv and lambda drbs phages.

Specialized transducing phages carrying segments of the Escherichia coli chromosome from the rbs-ilv region including rrn genes have been isolated. These phages carry rrn transcription units coding for 16S and 23S rRNA with the direction of transcription clockwise towards the ilv operon. While one of the phages (lambdad279rbs) appears to carry the genuine rrn gene, denoted rrnC, located between rbs and ilv at 82 min on the E. coli chromosome another one isolated as an ilv transducing phage, lambda5ilv, carries a hybrid rrn gene, denoted rrnX, which has originated from a recombinational cross-over between the rrnC and one of the other rrn genes.

Chromosome Mapping↗
PubMed1978

Plasmids useable as gene-cloning vectors in an in vitro packaging by coliphage lambda: "cosmids".

A plasmid which contains a cos site of lambda and can be packaged into lambda bacteriophage particles is termed a "cosmid". Such plasmids can be used as gene cloning vectors in conjunction with an in vitro packaging system. The properties of a new series of cosmids based on the ColE1 replicon are described, including small temperature-sensitive plasmids which have lost mobilisation functions and carry no IS sequences. Amongst these plasmids are vectors for XmaI, BglII, BamHI, HindIII, PstI, KpnI, SalI and EcoRI. It is demonstrated that by using cosmids in particular size ranges these plasmids provide a high efficiency cloning system which yields essentially only hybrid clones without resort to a second selection or screening step, and without prior modification (e.g. phosphatase) treatment of the DNA. Attempts were made to optimise the cloning properties of the cosmid system. An Escherichia coli "gene bank" was obtained with an efficiency of 5 . 10(5) clones per microgram of E. coli DNA, and in which any particular unselected marker may be found in about one out of every 400 clones. It was demonstrated that deletion of mobilisation functions leads to loss of ability to form relaxation-complex without affecting copy number or segregation properties of the temperature-sensitive derivatives. The vectors are amplifiable in chloramphenicol to make up about 50% of the total cellular DNA.

Coliphages↗
PubMed1978

Cosmids: a type of plasmid gene-cloning vector that is packageable in vitro in bacteriophage lambda heads.

Evidence is presented that ColE1 hybrid plasmids carrying the cohesive-end site (cos) of lambda can be used as gene cloning vectors in conjunction with the lambda in vitro packaging system of Hohn and Murray [(1977) Proc. Natl. Acad. Sci. USA 74, 3259--3263]. Due to the requirement for a large DNA molecule for efficient packaging, there is a direct selection for hybrids carrying large sections of foreign DNA. The small vector plasmids do not contribute a large background in the transduced population, which is therefore markedly enriched for large hybrid plasmids (over 90%). The efficiency of the in vitro packaging system is on the order of 10(5) hybrid clones per microgram of foreign DNA for hybrids in the 20--30 million dalton range.

Coliphages↗
PubMed1977

On the structure of the deo operon of Escherichia coli.

A characterization of a specialized transducing lambda phage for the deo operon (lambdaddeo), and some composite colE1-deo plasmids is given in this paper. This includes localization of the RSmaI, RHind/III, RBamI, and REcoRI sensitive sites. The deo genes have been localized by construction of composite colE1-deo plasmids. Using the DNA fragments, obtained by digestion with REcoRI and RHindIII, respectively, as templates in an in vitro protein synthesizing system, it has been possible to give the direction of transcription and the exact location of the deo genes, relative to the endonuclease sites. Furthermore, the cytO,P and deoO,P regions have been mapped relative to the structural genes. Supercoiled co1E1-deo DNA has been used as template in the in vitro system; this DNA gives essentially the same results as the endonuclease-fragmented DNA. The use of the different types of templates is discussed.

Coliphages↗
PubMed1977

Diabetes mellitus in an urbanized, isolated Polynesian population. The Funafuti survey.

An epidemiologic study of diabetes in the urbanized Polynesian population of Funafuti has established a prevalence of 8 per cent in subjects aged 10 years and over. Of these, 0.9 per cent were known diabetics, and the remainder were diagnosed on the basis of a plasma glucose level of at least 160 mg./100 ml. two hours after a 75 gm. glucose load. A further 5.9 per cent had borderline diabetes as judged by a two-hour postload plasma glucose of 140-159 mg./100 ml. In those aged 20 years and over, the prevalence of diabetes was 10.1 per cent, similar to that reported in other acculturated Polynesian groups. The prevalence of both borderline diabetes and frank diabetes was twice as high in the females as in males. This difference appeared to be related to the greater degree of obesity in the females, but the prevalence was not related to parity. The increase in frequency of diabetes among these islanders coincides with a change of traditional island life style to that of urbanized Western populations. The results suggest that there may be 10 times the actual number of known diabetics in some Pacific populations.

Adolescent↗
PubMed1976

A case of asthma.

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Adolescent↗
PubMed1976

Interaction of Mycoplasma dispar and Mycoplasma agalactiae subsp. bovis with bovine alveolar macrophages and bovine lacteal polymorphonuclear leukocytes.

Mycoplasma dispar and Mycoplasma agalactiae subsp. bovis survived or grew in cultures of bovine lacteal polymorphonuclear leukocytes or bovine alveolar macrophages. In the presence of specific bovine antibody, macrophages and polymorphonuclear leukocytes appeared to kill both species of mycoplasma. Specific rabbit antisera also promoted the killing of these mycoplasmas by bovine macrophages but had no demonstrable activity for bovine polymorphonuclear leukocytes. It is suggested that phagocytosis of these mycoplasmas by bovine cells occurs only in the presence of specific antibody. The experiments also indicate that differences exist between bovine polymorphonuclear leukocytes and macrophages with regard to their receptor sites for immunoglobulins.

Animals↗