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Biomedical subjects

L Caro

Publications and source records attributed to L Caro.

At least 37 records · Page 2Linked to original sources
PubMed1985

The influence of consanguinity on fertility and infant mortality in Sanabria (Zamora, Spain).

"The effects of consanguinity on fertility and infant mortality are studied in the population of the Sanabria Valley (Zamora province, Spain). The sample is made up of 965 complete families, 100 couples being first cousins (FC), 172 second cousins (SC) and 693 non-related (NR). There appears little difference in the fertility of consanguineous and unrelated couples but infant mortality rates (endogenous and exogenous) are higher among the offspring of consanguineous couples."

Biology↗
PubMed1984

Overinitiation of chromosome and plasmid replication in a dna Acos mutant of Escherichia coli K12. Evidence for dnaA-dnaB interactions.

The dnaAcos mutations are phenotypic suppressors of dnaAts46 that are co-transduced with dnaA, render the cell cold sensitive, and cause an excess of chromosome replication relative to cell mass when the cells are shifted from 42 degrees C to 32 degrees C. We have used pulse labelling and DNA-DNA hybridization to follow the effect of a temperature shift on the replication of the chromosome and of the plasmids pSC101, RTF-Tc, and lambda dv in such strains. After a shift of a dnaAcos strain from 42 degrees C to 32 degrees C (non-permissive temperature), initiation of the chromosome and replication of the plasmid pSC101 are stimulated, while the dnaA-independent plasmid RTF-Tc is not affected. The presence of pSC101 does not affect the level of overinitiation of the chromosome. The presence of lambda dv suppresses the cold sensitivity of dnaAcos mutants and allows the cells to grow at both 32 degrees C and 42 degrees C. The presence of lambda dv suppresses the overinitiation of chromosome and of pSC101 replication at 32 degrees C. Previous reports had shown that these suppressions involve an interaction between the dnaA product and the lambda P protein, which is also known to interact with dnaB. We show here that the mutant prophage P1 bac-crr, which produces high levels of a dnaB analogue, suppresses the dnaAcos phenotype, while wild type P1 does not. These results suggest that initiation involves interactions between the dnaA and dnaB products.

Chromosomes, Bacterial↗
PubMed1984

Replication functions encoded by the plasmid pSC101.

We describe the mapping of several genetic loci involved in the replication of the pSC101 plasmid. These include the origin of replication and a short segment of DNA that encodes a pSC101 incompatibility function. This short segment lies within the origin region. Flanking the incompatibility segment are two loci, repA and repB, which are required for replication. The product of the repA locus is shown to be trans-acting.

Bacterial Proteins↗
PubMed1984

Detection of displacement ("D") loops with the properties of a replicating intermediate synthesized by a DNA/membrane complex derived from the low-copy-number plasmid RK2.

A significant fraction of the plasmid DNA extracted from an RK2 miniplasmid DNA/membrane complex after incubation in vitro with appropriate substrates and cofactors contains "D" or displacement loops in one of at least three loci in the genome. These include the origin of replication and two transposon regions that code for kanamycin and tetracycline resistance. The relationship of these loops to early replicating intermediates for plasmid and transposon replication is discussed.

DNA Replication↗
PubMed1983

Plasmid pSC101 replication mutants generated by insertion of the transposon Tn1000.

A derivative of pSC101, pLC709, was constructed by ligation of the HincII-A fragment of pSC101 to the mini-colEI plasmid pVH51 and to a DNA fragment encoding resistance to the antibiotics streptomycin and spectinomycin. Insertions of the transposon Tn1000 (gamma-delta) into the pSC101 replication region of pLC709 were isolated following cotransfer of the plasmid with the sex factor F. The sites of insertion of the transposon were determined by restriction enzyme analysis and the replication and incompatibility properties of the insertion plasmids and DNA fragments cloned from them were analysed. The insertion mutations defined a locus, inc, of approximately 200 base-pairs that is responsible for pSC101-specific incompatibility. Two mutations adjacent to this region inactivate pSC101 replication but can be complemented in trans by a wild-type pSC101 plasmid, and thus define a trans-acting replication function, rep. The inc locus is within a larger region of some 450 base-pairs that is essential for pSC101 replication and that includes the origin of replication. This 450 base-pair segment can replicate in the presence of a helper plasmid that supplies the rep function in trans.

DNA Replication↗
PubMed1983

The nucleotide sequence of replication and maintenance functions encoded by plasmid pSC101.

The nucleotide sequence of 1100bp around the origin of replication of the pSC101 plasmid has been determined. This segment of DNA is capable of replication in the presence of a helper plasmid. The sequence data reveal similarities between pSC101 and several other replicons. The origin of replication contains three direct repeats of an 18bp sequence associated with a segment exceptionally rich in A-T base pairs. A promotor that probably directs transcription of a gene encoding an essential plasmid replication function is associated with a region of extensive potential secondary structure. The sequence presented here includes the sequence of the par region involved in partitioning of plasmids at cell division.

Base Composition↗
PubMed1983

The repA2 gene of the plasmid R100.1 encodes a repressor of plasmid replication.

We have constructed two miniplasmids, derived from the resistance plasmid R100.1. In one of these plasmids 400 bp of R100.1 DNA have been replaced by DNA from the transposon Tn1000 (gamma-delta). This substitution removes the amino-terminal end of the repA2 coding sequence of R100.1 and results in an increased copy number of the plasmid carrying the substitution. The copy number of the substituted plasmid is reduced to normal levels in the presence of R100.1. The repA2 gene thus encodes a trans-acting repressor function involved in the control of plasmid replication.

DNA Replication↗
PubMed1983

Role of the sfiA-dependent cell division regulation system in Escherichia coli.

Several authors have suggested that the SOS-associated (sfiA-dependent) system of division inhibition, normally induced by perturbations of DNA replication, also regulates steady-state (unperturbed) cell division. The present work shows that mean cell mass is identical in sfiA+ and sfiA mutant cultures during steady-state growth, that mass adjustment is identical after shift up, that sfiA expression is not induced by shift up, and that a sfiA mutation does not cause aberrant chromosome segregation.

Bacterial Proteins↗
PubMed1982

Isolation of the kanamycin resistance region (Tn2350) of plasmid R1drd-19 as an autonomous replicon.

We have isolated a circular form of Tn2350, an IS1-flanked kanamycin resistance transposon forming part of the plasmid R1drd-19. This circle (pTn2350::9.6 kilobases) contains a single IS1 element and probably arises by recombination between the two directly repeated Is1 sequences of Tn2350. It can be used to transform Escherichia coli to kanamycin resistance. It is capable of autonomous replication but is not maintained stably in dividing cells and segregates under nonselective conditions. Cloning of a segment of pTn2350 on a conditional plasmid vector allowed us to assign the replication functions of this plasmid to a 1.6-kilobase restriction fragment. The plasmid R1drd-19 can thus be considered as a cointegrate between two replicons separated by IS1 sequences.

Base Sequence↗
PubMed1981

The structure of R1drd19: a revised physical map of the plasmid.

We have analyzed derivatives of the plasmid R1drd19 carrying the transposon Tn10 by electron microscopy following denaturation and renaturation of the molecules, and by digestion with various restriction enzymes, gel electrophoresis and Southern blotting. We show: 1) that the published restriction map of R1drd19 is inconsistent with our results. We present a modified map which is consistent with our data. 2) that R1drd19 carries a single resident copy of the element IS10 which is normally associated with Tn10 as an inverted repeat, and 3) that R1drd19 carries three copies of the insertion element IS1 in the resistance determinant region.

DNA Restriction Enzymes↗
PubMed1981

The initiation of chromosome replication in a dnaAts46 and a dnaA+ strain at various temperatures.

The regulation of chromosome replication initiation was studied at various temperatures with an E. coli dnaA46 strain and its dnaA+ parent. We find that, in both strains, the "initiation mass" varies depending upon growth temperature while the replication time remains constant relative to the cell doubling time. In the permissive temperature range, the initiation mass of the dnaA46 mutant strain is larger by a constant factor than that for a dnaA+ strain. We conclude that, even at temperatures permissive for growth of the dnaA46 strain, the activity of the dnaA46 product is lower than that of the wild-type protein. The dnaA gene product, therefore, plays an important role in regulating initiation.

DNA Replication↗
PubMed1981

Genetical and structural analysis of a group of lambda ilv and lambda rho transducing phages.

Eight lambda ilv C transducing phages generated from E. coli K12 secondary site lysogens have been analysed genetically and physically. Two of them carry, in addition, the rho gene and its promotor region, but not the cya gene. The ilv O 603 mutation has been located between ilv G and ilv E. Electrophoretic analysis of the proteins synthesized by these phages in a system of UV irradiated cells allowed us to assign molecular weights of 55000 and 66000 daltons to the ilv C and the ilv D gene products, respectively, and to show that an ilv G-encoded polypeptide of 60000 daltons is made from an ilv O- but not from an ilv O+ phage. The expression of the ilv G gene is discussed in the light of the recent finding of a promoter-attenuator region lying upstream to ilv G. Finally, we have found that one of the lambda ilv phages does not have the classical structure of a transducing phage.

Amino Acids, Branched-Chain↗
PubMed1981

[Correlation of pancreatic function and structure. Evaluation of the secretin test and retrograde cholangiopancreatography].

We have made an analysis of correlation between Secretin Test and Retrograde pancreatography in 25 patients. Using Secretin Test, in these comparative evaluation we confirmed the predictive values of normality or pathological alteration of the gland obtained through functional exploration of the pancreon. In consequence it's correct to use this test as a first mean of establishing the presence of pancreatic pathologies.

Adult↗