Expression of Escherichia coli ribosomal protein and RNA polymerase genes cloned on plasmids

Fragments of lambda drifd 18 DNA with different end-points within the set of structural genes of ribosomal proteins L11 (RPLK), Li (rplA), L10 (rplJ) and L12 (rplL) as well as the beta (rpoB) ANd beta' (rpoC) subunits of RNA polymerase have been cloned on plasmids. These plasmids were transformed in host cells which were mutant for each of the genes, enabling expression of both wild-type (plasmid-borne) and mutant (chromosomal) genes to be differentiated. On the basis of these results we propose the following genetic structure for the region: rplK and rplA are in one operon; rplL, rpoB and rpoC are in a second. Our data suggest the possibility that rplJ is by itself in an operon situated between the other two.

Cell-free synthesis of proteins coding for mobilisation functions of ColE1 and transposition functions of Tn3

A hybrid plasmid, pJC74, carrying the large (3.35 Md) EcoRI-PstI fragment of ColE1, the 1.3 and 1.8 Md PstI fragments of plasmid R1 drd19 (containing a part of Tn3 and known to specify transpostion functions), and a part of gamma bacteriophage DNA carrying the fused cohesive ends of gamma (cos) was constructed. Supercoiled DNA of pJC74 and a series of deletions (series pJC75) were used in a cell-free coupled transcription-translation system. Analysis of the proteins produced allowed the identification of a 28 to 30 kd protein and/or a 3 kd protein responsible for mobilisation of the plasmids in sex-factor-promoted conjugation. Furthermore, three protein bands of 12, 12.5 and 13 kd were correlated with the presence of a portion of the Tn3 transposon previously shown to code for transposition functions which can complement in trans. These latter and the 30 kd beta-lactamase were the only proteins identified as Tn3-specific by comparison of ColE1 with RSF2124.

Altered DNA-protein relaxation complex in a replication mutant of plasmid ColE1

Approximately 200,000 clones of Escherichia coli carrying mutagen-treated colicinogenic plasmid E1 (ColE1) were examined for irreversible loss of the plasmid at 43 degrees. Thirty of these clones that appeared to be most defective in plasmid DNA replication at the non-permissive temperature were selected for the study of: (a) the kinetics of plasmid and chromosomal DNA replication during a temperature shift in either the presence or absence of chloramphenicol; (b) the temperature stability of the plasmid DNA-protein relaxation complex; and (c) the temperature effect on F-promoted conjugal transfer. Two mutant plasmids, pJC307 and pJC301, showed defects in their relaxation complex. The relaxation complex of pJC307 exhibited an altered temperature stability in vitro. Reversion to temperature resistant replication resulted in four out of five cases in a concomitant change in the temperature stability of the relaxation complex. Conjugal mobility of this mutant was not markedly reduced at the permissive or non-permissive temperature. Plasmid pJC301 could not be isolated in the form of a relaxation complex and it was very poorly mobilized in an F'-promoted conjugation. These results indicate that the ColE1 plasmid codes for at least one of the proteins of the relaxation complex and that the relaxation complex is involved in ColE1 DNA replication. In addition, the properties of the mutant plasmid pJC301 are consistent with a role for the complex in the mobilization of ColE1 during conjugation.

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.

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.

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.

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.

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.

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.

A single radial haemolysis technique for the measurement of antibody to Mycoplasma bovis in bovine sera

A single radial haemolysis in gel technique is described for assaying antibody to Mycoplasma bovis (M agalactiae subsp bovis) in bovine sera. The test, which should be particularly useful for screening large numbers of serum samples, is sensitive, simple to perform and highly reproducible.

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.

Plasmid ColE1 DNA replication in Escherichia coli strains temperature-sensitive for DNA replication

Mutants of the dnaA, dnaC, dnaD, polC, dnaF and dnaG gene loci were tested for their capacity for colicinogenic plasmid E1 (ColE1) replication at a non-permissive temperature. It was found that ColE1 replication was independent of the dnaA gene function and dependent on dnaC, D, F and G. ColE1 replication in the polC mutant E486 continued for several hours but at a greatly reduced rate. No effect was found of the dnaG mutation on thymine-deprivation-induced "priming" of ColE1 replication at the non-permissive temperature. The mutants also were tested for aberrant replication intermediates of plasmid DNA as well as a temperature sensitive supercoiled DNA-protein relaxation complex. RNA-containing supercoils were found to accumulate in a poIC mutant also blocked for protein synthesis.

Independence of F replication and chromosome replication in Escherichia coli

Data are presented which show that F replication is not coupled to any stage of the replication cycle of the host chromosome or to cell division, and is probably not related to surface area. It is also shown that the initiation mass of F increases progressively as the growth rate increases, the number of copies of F per unit of mass falling by half between doubling times of 0.8 and 2.7 generations per hour. It is further shown that the presence of an F particle does not influence the initiation mass of the chromosome.

Presence of a dialysable fraction in normal bovine whey capable of killing several species of bovine mycoplasmas

Most normal bovine whey samples contain a fraction that survives heating at 56 degrees C. for 30 min., passes through a dialysis membrane and kills a maximum of seven out of ten of the different bovine mycoplasma species tested. Some whey samples appear more active than other but not all affect the same strains of mycoplasma indicating some specificity in their action. Absorption of the active factor from whey by heterologous and homologous mycoplasmas and by erythrocytes was observed. Binding of the factor to mycoplasmas appears to be temperature-dependent and non-specific, but subsequent mycoplasmacidal action shows some specificity.

Assessment of the world food situation-present and future

The widespread bad harvests of 1972 in various regions of the world, the consequent reduction in grain reserves, the rapid rise in food prices almost everywhere and its impact on inflation, all have served to draw renewed attention to the problem of hunger which affects millions of human beings in the world today. During the 1974 United Nations World Food Conference many important matters relating to this problem were debated: the creation of international grain reserves; problems concerning world trade of foodstuffs; the current difficulties with certain key agricultural production factors, such as fertilizers; the necessity for organizing a worldwide information system on the situation; and prospects of various harvests and threats of famine in underdeveloped countries. It is often the case that discussion of the hunger problem does not correspond to the gravity of the crisis; true causes of the present situation are not examined, and measures are not adopted that will once and for all--for the first time--abolish hunger. In view of the prospect that the real issues are often ignored, the Transnational Institute provides this analysis in an attempt to clarify what must be done to abolish hunger in the belief that this is within the reach of humanity when and if we are determined to end the irrationalities of the present economic system and the relations of domination which some individuals and countries seek to continue.

Analysis of traditional strategies to combat world hunger and their results

The traditional strategies proposed for development of the agricultural production of the underdeveloped countries are examined in this article. It is shown that the application of these strategies in the past has proven insufficient to eliminate world hunger. The limitations of these strategies are discussed and proposals are made for achieving the agricultural development in the underdeveloped world that will be necessary to eliminate hunger in the near future.

Serological comparison and haemagglutinating activity of Mycoplasma dispar

A comparison of twelve strains of Mycoplasma dispar by the metabolism inhibition and indirect haemagglutination tests has shown them to form a serologically homogeneous group of micro-organisms. The twelve strains vary in their haemagglutinating activity against erythrocytes from different animal species, and certain of the strains can be distinguished by the erythrocytes they agglutinate. Haemagglutination may thus provide a method by which certain strains can be typed. The erythrocyte receptor site does not appear to contain sialic acid and is not sensitive to proteolytic enzymes. On the mycoplasma cell two attachment sites have been demonstrated. One, by which it attaches to sheep and bovine erythrocytes, is a protein or contains a protein moiety. The chemical nature of the other attachment site, by which M. dispar attaches to rabbit erythrocytes, is unknown.

Arrhythmias following cardiac valve replacement

A prospective study of 50 consecutive patients undergoing cardiac valve replacement was designed to determine the incidence, types, and predisposing factors to postoperative arrhythmias. Patients were monitored continuously for the first 7 days following surgery.

Thirty-seven patients (74%) experienced a total of 66 episodes of arrhythmia. Supra-ventricualr arrhythmias were the most common (43 of 66; 65%). The most frequent specific arrhythmia was atrial fibrillation (21 of 66; 32%). Arrhythmias occurred 77% of the time within the first 48 hours of surgery.

Of 25 factors evaluated preoperatively in each patient, only two were found to predispose to postoperative arrhythmias. These were: (1) previous cardiac surgery; and (2) elevated blood urea nitrogen.

There were four hospital deaths, representinig a hospital mortality of 8%. No deaths were due to a primary arrhythmia.

It is concluded that whereas arrhythmias are a very common complication of cardiac valve replacement, early detection and treatment has lessened their significance as a cause of postoperative mortality and morbidity.