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Biomedical subjects

A Feher

Publications and source records attributed to A Feher.

9 recordsLinked to original sources
PubMed2000

Cell cycle function of a Medicago sativa A2-type cyclin interacting with a PSTAIRE-type cyclin-dependent kinase and a retinoblastoma protein.

In plants multiple A-type cyclins with distinct expression patterns have been isolated and classified into three subgroups (A1-A3), while in animal somatic cells a single type of cyclin A is required for cell-cycle regulation from the S to M phases. We studied the function of an A2-type cyclin from Medicago sativa (Medsa;cycA2) which, in contrast to animal and most plant A-type cyclins, was expressed in all phases of the cell cycle. Using synchronized alfalfa cell cultures and anti-Medsa;CycA2 polyclonal antibodies, we showed that while the mRNA level increased steadily from the late G1 to the G2-M phase, the protein level after a rapid increase in S-phase reached a plateau during the G2 phase. In the yeast two-hybrid system, the Medsa;CycA2 protein interacted with the PSTAIRE-motif-containing cyclin-dependent kinase Cdc2MsA and with the maize retinoblastoma protein. Unexpectedly, the CycA2-associated kinase activity was biphasic: a first activity peak occurred in the S phase while the major one occurred during the G2/M transition, with no apparent dependence upon the actual levels of the Medsa;CycA2 and Cdc2MsA proteins. Immunohistological localization of the cyclin A2 protein by immunofluorescence and immunogold labelling revealed the presence of Medsa;CycA2 in the nucleus of the interphase and prophase cells, while it was undetectable thereafter during mitosis. Together these data suggest that Medsa;CycA2 plays a role both in the S phase and at the G2/M transition.

Amino Acid Sequence↗
PubMed1999

Attention-based texture segregation.

Luminance- or color-defined +/- 45 degrees-oriented bars were arranged to yield single-feature or double-conjunction texture pairs. In the former, the global edge between two regions is formed by differences in one attribute (orientation, or color, or luminance). In the color/orientation double-conjunction pair, one region has +45 degrees red and -45 degrees green textels, the other -45 degrees red and +45 degrees green textels (the luminance/orientation double-conjunction pair is similar); such a pair contains a single-feature orientation edge in the subset of red (or green) textels, and a color edge in the subset of +45 degrees (or -45 degrees) textels. We studied whether edge detection improved when observers were instructed to attend to such subsets. Two groups of observers participated: in the test group, the stimulus construction was explained to observers, and they were cued to attend to one subset. The control group ran through the same total number of sessions without explanations/cues. The effect of cuing was week but statistically significant. Feature cuing was more effective for color/orientation than for luminance/orientation conjunctions. Within each stimulus category, performance was nearly the same no matter which subset was attended to. On average, a global performance improvement occurred over time even without cuing, but some observers did not improve with either cuing or practice. We discuss these results in the context of one-versus two-stage segregation theories, as well as by reference to signal enhancement versus noise suppression. We conclude that texture segregation can be improved by attentional strategies aimed to isolate specific stimulus features.

Adolescent↗
PubMed1996

Active site-directed thrombin inhibitors: alpha-hydroxyacyl-prolyl-arginals, new orally active stable analogues of D-Phe-Pro-Arg-H.

D-alpha-Hydroxyacyl-prolyl-arginals, a new type of analogues of D-Phe-Pro-Arg-H (R1), have been prepared and evaluated. Unlike R1, whose terminal group is NH2, the new analogues with a terminal OH group are stable, as are the N-substituted derivatives of R1, that is, D-MePhe-Pro-Arg-H (R2), the highly potent and selective thrombin inhibitor, and Boc-D-Phe-Pro-Arg-H (R3), the much less favorable analogue. The most notable of the new analogues corresponds to the general formula D-Xaa-Pro-Arg-H, wherein Xaa means the acyl residue of mandelic acid (Man, 1), diphenyllactic acid (Dpl, 2), hexahydrophenyllactic acid (Hpl, 3), or hexahydromandelic acid (Hma, 4). In plasma clotting assays, 1 to 4 appeared to inhibit thrombin as well as some other clotting enzymes involved in thrombin generation, whereas R1 and R2 seemed to produce anticoagulation through inhibition of thrombin only. In the fibrin plate assay, 1 to 4 possessed even more moderate antifibrinolytic activities than R2. In in vivo evaluation in rats and rabbits, 2 to 4 proved to be potent anticoagulants/antithrombotics even on oral administration in a dose of 5 mg/kg. In view of these findings with the alpha-hydroxyacyl-prolyl-arginals, it is very likely that the less favorable biologic properties of Boc-D-Phe-Pro-Arg-H are due to the hydrophobicity and bulkiness of the terminal Boc-NH rather than its neutrality.

Administration, Oral↗
PubMed1996

Interactions of monocular and cyclopean components and the role of depth in the Ebbinghaus illusion.

A study of size interactions of objects in three-dimensional space is reported. The canonical form of the Ebbinghaus illusion-test circles surrounded by large or small inducers-was used. Both monocularly visible (M) and purely cyclopean (C) objects were displayed stereoscopically to isolate the monocular and cyclopean components of the illusion. The results of two experiments indicate that: (i) depth plays a significant role when the test circles are cyclopean, but not when they are monocularly visible; and (ii) the size of C objects is affected equally by C and M inducers, but the size of M objects is affected much more strongly by M than by C inducers. In conclusion, possible explanations are offered for the main trends in the data, the most interesting of which is that cyclopean tests seem to be interacting only with the cyclopean component of monocularly visible inducers.

Adult↗
PubMed1996

Flow limitation in normal infants: a new method for forced expiratory maneuvers from raised lung volumes.

Forced expiratory maneuvers generated by rapid thoracic compression have been used to assess airway function in infants. It remains unclear whether flow limitation can be achieved in healthy infants because low pressure transmission across the chest wall and inspiratory effort may limit the maximum transpulmonary pressure developed during the maneuver. We have found that several rapid inflations to a lung volume set at an airway pressure of 30 cmH2O (V80) briefly inhibit respiratory effort and allow forced expiration to proceed from V80 to residual volume. We used a water-filled esophageal catheter to measure isovolume pressure-flow curves in seven healthy infants (3-88 mo). Forced vital capacity (FVC) was defined as the volume between V80 and residual volume. Pressure transmission between the compression jacket and the esophagus decreased with decreasing lung volume and averaged 60 and 37% at 50 and 75% of expired FVC, respectively. Subjects demonstrated plateaus in their isovolume pressure-flow curves at 50% of expired FVC and lower lung volumes. We conclude that this new methodology enables forced expiratory maneuvers to achieve flow limitation in healthy infants over at least the lower portion of their lung volume.

Child Development↗
PubMed1992

The radial forearm flap in intraoral reconstruction after a pull-through operation.

Free fasciocutaneous forearm flaps, based on the radial artery, were used to replace the tissue defect caused by pull-through operations for cancer of the floor of the mouth in 11 patients. There was no total or partial flap failure. The greatest advantage of the method is that restriction of the tongue movement is less when compared with the results of other methods. The thin forearm flaps are adaptable and pliable. The newly developed lower alveolar crest and the sublingual sulcus make prosthetic rehabilitation possible.

Adult↗