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Biomedical subjects

A Pop

Publications and source records attributed to A Pop.

At least 19 recordsLinked to original sources
PubMed2006

Cis-regulatory evolution of chalcone-synthase expression in the genus Arabidopsis.

The contribution of cis-regulation to adaptive evolutionary change is believed to be essential, yet little is known about the evolutionary rules that govern regulatory sequences. Here, we characterize the short-term evolutionary dynamics of a cis-regulatory region within and among two closely related species, A. lyrata and A. halleri, and compare our findings to A. thaliana. We focused on the cis-regulatory region of chalcone synthase (CHS), a key enzyme involved in the synthesis of plant secondary metabolites. We observed patterns of nucleotide diversity that differ among species but do not depart from neutral expectations. Using intra- and interspecific F1 progeny, we have evaluated functional cis-regulatory variation in response to light and herbivory, environmental cues, which are known to induce CHS expression. We find that substantial cis-regulatory variation segregates within and among populations as well as between species, some of which results from interspecific genetic introgression. We further demonstrate that, in A. thaliana, CHS cis-regulation in response to herbivory is greater than in A. lyrata or A. halleri. Our work indicates that the evolutionary dynamics of a cis-regulatory region is characterized by pervasive functional variation, achieved mostly by modification of response modules to one but not all environmental cues. Our study did not detect the footprint of selection on this variation.

Acyltransferases↗
PubMed2001

Molecular motions within self-assembled dimeric capsules with tetraethylammonium cations as guest.

Hydrogen-bonded, dimeric capsules of calix[4]arenes substituted at the wide rim by four urea functions show unprecedented dynamic features when a tetraethylammonium cation is included as a guest. The seam of hydrogen bonds C=O...(HN)2C=O in the equatorial region which holds the two calixarene counterparts together changes its directionality fast (at 25 degrees C), while the dimer itself is kinetically stable on the NMR time scale. An energy barrier of deltaG++ = 49.9 kJmol(-1) (Tc 276 K) was estimated for this reorientation from variable-temperature (VT) NMR measurements. Lowering the temperature to about -50 degrees C restricts also the rotation of the encapsulated tetraethylammonium cation around a pseudo C2-symmetry axis in the equatorial plane of the capsule, while its rotation around the C4 axis is still fast. As a result of this restriction two ethyl groups of the tetraethylammonium cation point towards the "poles" of the capsule, while the other pair lies in the "equator" region. Variable-temperature 1H NMR experiments led to a barrier of deltaG++=54.8kJ mol(-1) (Tc 306 K) for the exchange of these different ethyl groups. Studies with the ternary complex formed by a C2v-symmetrical tetraurea proved that both processes, reorientation of the hydrogen bonds and rotation of the guest, take place independently. Molecular dynamics simulations suggest that the capsule is strongly expanded by the larger tetraethylammonium cation in comparison with benzene as guest. Thus, on average only one N-H...O hydrogen bond is formed per urea function and the interaction energy between the two tetraurea calixarenes is less favorable by about 15 kcal mol(-1). This is overcompensated by an energy gain of about 36 kcal mol(-1) due to cation-pi interactions. These results provide a rationale to understand the high stability of the complex inspite of the mobility of the hydrogen-bonded belt.

Calixarenes↗
PubMed1999

Fifteen years later: colonoscopic retroflexion revisited.

OBJECTIVE: Retroflex views of the rectal vault are included in the teaching of colonoscopic technique but are not pervasive in clinical practice. The utility of adding a retroflex maneuver at the end of colonoscopy has yet to be determined. The aim of this study was to evaluate the additional benefit of a retroflex view of the rectal vault at the completion of colonoscopic examination. METHODS: A prospective study of consecutive colonoscopies performed by a single physician was conducted. The rectal vault was first visually inspected upon withdrawal of the colonoscope. The endoscope was then readvanced into the rectum and retroflexed to view the vault. Endoscopic findings on both views were recorded along with demographic patient information. The six groups of findings sought on the two views were: retained stool, abnormal hemorrhoids, erosions/ulcerations, polyps, masses, and normal examinations. A determination on whether retroflex views influenced patient diagnosis was recorded by the endoscopist. RESULTS: There were 453 patients enrolled: 182 (40.2%) male and 271 (59.8%) female, consisting of 216 African-Americans, 232 Caucasians, and five Asians. The retroflex maneuver was performed successfully in 445 of 453 patients. In all but nine cases, the retroflex view did not produce additional information. The nine findings included three inflammatory pseudopolyps, five hyperplastic polyps, and one case of erosions/ulcerations. CONCLUSIONS: In the majority of cases, retroflexing the endoscope does not produce additional information compared with the thorough examination in straight view. The retroflex view may be of benefit if there is suspicion of pathology upon insertion or withdrawal of the colonoscope.

Colonoscopy↗
PubMed1998

Community periodontal index and treatment needs values (CPITN) in a factory worker group in Cluj-Napoca, Romania.

The aim of the study was to determine the prevalence of periodontal disease and the treatment needs in a population of 214 factory workers in Romania. Of those examined, 9.34 per cent were in periodontal health (code 0), 21.49 per cent had gingival bleeding (code 1), 18.69 per cent had supra- or subgingival calculus (code 2), 32.71 per cent presented with pathological pockets 4-5 mm deep (code 3) and 17.76 per cent had pathological pockets 6 mm or deeper (code 4). The distribution of these subjects among the treatment need categories revealed that 30.83 per cent would need improvement in personal oral hygiene (I), 51.40 per cent from the subjects would need treatment (I) + scaling (II) and 17.76 per cent would need treatment (I + II) + complex treatment (III).

Adolescent↗
PubMed1983

Suppression in strabismus and the hemiretinal trigger mechanism.

A perimeter and a modified Lees screen were used to determine the area of visual field that is suppressed in strabismus. Strabismic patients without fusion suppress the whole area of the visual field of the deviating eye that could have correspondence with the dominant eye. In the monofixation syndrome, suppression only involves the fovea and the diplopic point of the deviating eye. Diplopia, if present, is appreciated throughout the visual field shared by the two eyes, except for the blind spots. No evidence of hemiretinal suppression was found in any type of horizontal strabismus, including exotropia. However, there is a hemiretinal trigger mechanism for suppression. Once suppression has been triggered by this mechanism, it involves the whole visual field of the deviating eye, except for the monocular temporal crescent.

Adolescent↗
PubMed1983

Immunochemical studies on Brucella abortus lipopolysaccharides.

The antigenic-toxic complex of B. abortus isolated in the phenol phase of phenol/water system, is a lipopolysaccharide (LPS)-protein macromolecule. The specific side chain was isolated from this complex by means of pronase treatment and mild HCl cleavage, followed by fractionation on Sephadex. The side chain thus isolated lost its capacity to coat erythrocytes but not that of neutralizing antibodies, as shown in the hemagglutination inhibition test. Esterification of the side chain with lauryl sulfat restored its erythrocyte coating capacity. In view of transforming this haptene into an immunogen, it was attached to S. minnesota Re cells. Immunization of rabbits with this conjugate engendered the formation of antibodies that agglutinated B. abortus and B. melitensis cells as well. As the side chain could only be isolated from the smooth strain, it proves that a defect in the synthesis of this moiety gave rise to the rough Brucella mutant. In the latter fraction glucose, mannose and quinovosamine were identified. Fraction II separated on Sephadex was identified as the core polysaccharide, present in the preparation obtained from smooth and rough strain. In the core region 2-keto-3-deoxy-octonate, glucose, glucosamine (from the smooth but not from the rough strain) and protein were identified. Following the mild HCl hydrolysis, the lipid-protein moiety i.e. region 3, is also split off but without precipitating and, during the fractionation on Sephadex, it adsorbs onto the gel. The absence of beta-hydroxymyristic acid and glucosamine in Brucella lipid dissociates it from the enteric lipid A. In the LPS-protein's toxicity a major role has the protein present only in the smooth strain.

Animals↗
PubMed1975

Biochemical basis of the serological cross-reactions between Brucella abortus and Yersinia enterocolitica serotype O:9.

A method based on the inhibition of agglutination is described that may be used for the differential serological diagnosis between B. abortus and Y. enterocolitica serotype O:9. An antigen with high immunological capacity was isolated from Brucella. This antigen inhibited both homologous and heterologous agglutination by Brucella antiserum, but only the heterologous agglutination by Yersinia antiserum. It proved to be constitued of a polysaccharide (N-acetylglucosamine, glucose, mannose and 2-keto-3-deoxyoctonic acid), a protein and a phosphoglycerid moiety. Lipid A was absent from the Brucella antigen. Incomplete polysaccharide synthesis of the Brucella antigen, with concomitant loss of serological specificity by the rough mutant has been described. Oligosaccharides containing N-acetylgalactosamine, glucose and galactose were isolated from the specific side chain of Yersinia lipopolysaccharide. Lipid A constituents were also identified in the latter.

Acetylglucosamine↗