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At least 19 recordsLinked to original sources
PubMed1991

Large inversion in Escherichia coli K-12 1485IN between inversely oriented IS3 elements near lac and cdd.

A companion study has shown that the inversion carried by strain 1485IN has one terminus between lac and proC and the other between his and cdd of the normal strain. Starting with this mapping data, we have done molecular work demonstrating that the inversion occurred by recombination between inversely oriented two IS3 elements, one present near lac and the other near the cdd locus; i.e., the inversion is IN(is3B-is3E). Evidence supporting this conclusion includes: (i) Normal and inversion strains share two short regions with identical restriction maps. One of these regions is near lac and the other near cdd. (ii) IS3 homology was detected in each of the terminus regions of both the normal and inversion strains. (iii) The sequence on one side of the original IS3 element near lac has been exchanged with the sequence on one side of the IS3 near cdd. Whether the inversion has occurred by one event of homologous recombination between the two IS3 elements or has been caused by involvement of IS3 elements on an F factor is discussed. Another rearrangement, probably related to inversion and deletion, was detected between the IS3 and cdd of the inversion strain.

Base Sequence↗
PubMed1989

Cardiorespiratory and hemodynamic responses to inversion and inversion with sit-ups.

Eighteen men were studied during 15 minutes of inversion to determine the effects of 4 sit-ups per minute for 5 minutes on the cardiorespiratory system. Systolic blood pressure, diastolic blood pressure, ventilation, oxygen uptake, and METS increased significantly from preinversion/standing (A) to inversion (B). Arterial blood pressure increased from 122/81 mmHg to 142/99 mmHg during the first 5 minutes of inversion. Oxygen uptake increased from 341 ml.min-1 to 456 ml.min-1. Heart rate decreased significantly from (A) to (B). Double product, frequency of breaths, and tidal volume were not significantly changed from (A) to (B). Blood pressure, double product, ventilation, frequency of breaths, oxygen uptake, and METS increased significantly from the first 5 minutes of inversion (B) to the second 5 minutes of inversion with sit-ups (C). Arterial blood pressure increased from 142/99 mmHg (B) to 163/104 mmHg (C). The diastolic value remained significantly increased following the muscle strengthening exercise. Double product increased from 104 (B) to 126 (C), and oxygen uptake increased from 456 ml.min-1 (B) to 565 ml.min-1 (C). Following inversion/sit-ups (C), oxygen uptake decreased significantly during the third 5 minutes of inversion (D). Systolic blood pressure was also significantly decreased at (D) following the sit-ups. Upon returning to the standing position (E) versus the third 5 minutes of inversion (D), arterial blood pressure decreased significantly from 151/108 mmHg (D) to 123/84 mmHg (E). The postinversion/standing (E) blood pressure was nonsignificantly different from the preinversion/standing (A) blood pressure as was also the case with heart rate, double product, and tidal volume. Ventilation, frequency of breaths, oxygen uptake, and METS were still significantly increased during (E) versus (A). These data illustrate the influence of muscular exercise on the cardiorespiratory system during full -90 degree inversion. The increase in blood pressure is no cause for concern, and the assumed dangerous effects of full inversion have been overestimated.

Adolescent↗
PubMed1989

Recombination between homologies in direct and inverse orientation in the chromosome of Salmonella: intervals which are nonpermissive for inversion formation.

Sequences placed in inverse order at particular chromosome sites (permissive) recombine to generate an inversion; the same sequences, placed at other sites (nonpermissive) interact recombinationally but do not form the expected inversion recombinants. We have investigated the events that occur between sequences at nonpermissive sites. Genetically marked lac operons in inverse order were placed at nonpermissive sites in a single chromosome and Lac+ recombinants were selected. No inversions were formed. The Lac+ recombinants recovered include double-recombinant types in which information appears to have undergone a nonreciprocal information exchange; one mutant copy is repaired with no alteration of the other copy. Recombination within the lac operon is stimulated more than 100-fold by the presence of extensive homology (antenna sequences) outside of the region for which recombination is selected. Sequences placed in direct order at the ends of the same noninvertible chromosome segment recombine to form all the expected recombinant types including those in which a reciprocal exchange has generated a duplication. All the detected recombinant types can be accounted for by recombination between sister chromosomes. These results are discussed in terms of two alternative models. One explanation of the failure to detect inversion of some intervals is that particular inversions are lethal, despite the fact that no essential sequences are disrupted. Another explanation is that chromosome topology prevents sequences at nonpermissive sites in a single chromosome from engaging in the direct interaction required for inversion formation, but allows the sister strand exchanges that can generate the recombinant observed.

Base Sequence↗
PubMed1986

DNA inversion in bacteriophage Mu: characterization of the inversion site.

Gin-mediated site-specific recombination promotes inversion of the G segment of phage Mu. The crossover takes place between two 34 bp-long inverted repeat sequences flanking the G segment. We have characterized the inversion site, the target for the site-specific recombination mechanism. An artificial invertible segment was constructed which consists of parts of the invertible segments of Mu and phage P1, which in this respect are largely homologous. Upon inversion of this hybrid segment the crossover site could be located, by DNA sequencing, in the ACCT sequence of the centre of symmetry in the inverted repeat in Mu. The hybrid Mu-P1 segment inverts at a lower frequency than its parental invertible segments probably because of the mismatches between the inverted repeats of Mu and P1. This suggests that base pairing between the inverted repeats is an intermediate step in recombination. Plasmids with subcloned G segments lacking the adjacent beta region of Mu or the corresponding region in P7, a relative of P1, are deficient in inversion. By analysis through site-specific mutagenesis of Mu DNA, an enhancer element with multiple recognition sites was identified which is necessary for efficient inversion. This component of the inversion site was located in a 170 bp segment within the Mu beta region, 30 bp to the right of the inverted repeat sequence, but can be separated from the crossover site by a 1200 bp insertion without losing its effect.

Bacteriophage mu↗
PubMed1985

[Inversion polymorphism in the malaria mosquito Anopheles messeae. VI. Local selection and 3-dimensional differentiation of the inversion gene complexes for fertility].

A field experiment was carried on with the view of compulsory change of the frequency of chromosomal inversion (2R1) in the population of Anopheles messeae from the centre of the area. Quick return of the population to the original structure was observed. This confirmed that the local differentiation of chromosomal polymorphism is supported by natural selection. The fertility of the females was shown to be connected with the inversion polymorphism. The females with inversion complexes of genes of the "northern" type (with homozygotes 2R1) had higher fertility and lower dispersion of the fertility, in comparison with those having gene complexes which prevailed in the south part of the area.

Animals↗
PubMed1985

Oxygen and sulfur esters of "inverse substrates": different responses of amidinophenol and amidinothiophenol in the activation of the rate of tryptic hydrolysis of the inverse esters.

Kinetic parameters for the trypsin-catalyzed hydrolysis of the oxygen and sulfur "inverse substrates," p-amidinophenyl and p-amidinothiophenyl acetates and trimethylacetates, have been compared. The results suggest that both series of compounds are hydrolyzed via an identical pathway. Appreciable differences, however, were observed in the efficiency of the acylation process in both series, possibly reflecting the spatial requirements of the enzyme's active site toward these substrates. As reported previously, acceleration in deacylation by a positively charged molecule is a characteristic feature of trypsin-catalyzed hydrolysis of "inverse substrates." In the present investigation, it was shown that p-amidinothiophenol is ineffective as an activator, whereas its oxygen counterpart behaves as a potent activator toward oxygen and sulfur substrates. It is assumed that some ionic interaction between the enzyme and the ligand molecule could prevent the rate enhancement.

Acetates↗
PubMed1991

Gd-DTPA-enhanced short repetition time and short inversion time inversion recovery magnetic resonance imaging. Experimental and clinical assessment.

To suppress both water and fat signal while retaining the high signal of Gd-DTPA enhancement, magnetic resonance imaging (MRI) of phantoms and 28 patients with mass lesions was done using short repetition time (TR) and short inversion time inversion recovery (STIR) sequences. Optimal STIR pulse sequences of 500 to 1000/80-100/20-30 (TR/TI/TE) were determined by an experimental study. In most instances, a signal bandwidth of +/- 8 kHz was used to increase the signal-to-noise ratio. The authors measured image contrast between lesions and adjacent fatty tissue and compared postcontrast STIR and T1-weighted spin-echo (T1-W SE) images. When the signal intensity of a lesion is 80% of adjacent fatty tissue on postcontrast T1-W SE, short TR STIR images provide better tumor delineation.

Contrast Media↗
PubMed1976

Familial pericentric inversion of chromosome 19, inv(19) (p13q13) with a note on genetic counseling of pericentric inversion carriers.

An inmate of a hospital for the mentally retarded was found during a cytogenetic screening programme to have karyotype 46,XY,inv(19)(p13q13)mat. Clinical, cytogenetic and family findings are presented and it is concluded that the chromosomes abnormality was probably not the cause of the patient's retardation. The problem of genetic counseling of inversion carriers is examined in some detail and estimates of risk are given.

Adolescent↗
PubMed1978

[Inversion polymorphism in the malarial mosquito, Anopheles messeae. III. The temporal dynamics of the inversion frequencies in the population of the center of a geographic range].

The karyotypic structure of the studied population shows the clear temporal differentiation. The frequencies of the homozygotes IIR/IIR, IIIR1/IIIR1 and IIIL/IIIL increase to the middle of the reproductive period. This homozygotes are initial gene arrangements in the phylogenetic sense and their adaptive value is evidently higher than the alternative homozygotes during the population flowering. Inter-year correlations of the dynamic frequencies of several gene arrangements appears to be due to density-dependent selection. The population karyotypic structure is characterised by a high dynamics during the season. However, no directional displacement of the inversion frequencies was observed. This stability is explained by homeostasis of the population genetic structure.

Animals↗
PubMed1991

Generalizing Long's inversion of the matrix form of Prentice's equation and the concept of generalized inverse dioptric power.

The concept of generalized inverse dioptric power is introduced. Its use is illustrated in solving Long's matrix generalization of Prentice's equation for the decentration required to produce a specified prismatic effect. The solution holds in all cases for which a solution exists, including for the pure cylinder, and the result gives all solutions when more than one exists.

Eyeglasses↗