Prostaglandin F-2 alpha receptors in corpora lutea of pregnant rats and relationship with induction of 20 alpha-hydroxysteroid dehydrogenase

Luteal receptors for PGF-2 alpha in the pregnant rat were characterized. No changes in the Kd were found during pregnancy, whereas capacity increased to a maximum on Day 19, decreasing thereafter. The decrease in binding sites seen from Days 20 to 22 may be due to down regulation of the receptor by its ligand, since it was prevented by inhibition of PG synthesis by indomethacin treatment. Likewise, in-vivo treatment with PGF-2 alpha reduced the apparent number of PG binding sites. PG receptor concentration seems to be modulated by oestrogens since an increment was found on Day 19, associated with the known increase in plasma oestradiol concentrations, and since receptor concentration on Day 16 was significantly increased by oestradiol benzoate. The uterus also had a negative influence on the appearance of the PG receptor, since hysterectomy on Day 16 increased the number of binding sites on Day 18. However, receptor concentration and 20 alpha-hydroxysteroid dehydrogenase induction by hysterectomy was not affected by indomethacin, indicating that these events are probably not related to prostaglandin withdrawal. However, treatment with hCG, which diminishes enzyme induction by hysterectomy, did not produce changes in receptor concentration. The present results suggest that PGF-2 alpha, acting through a specific receptor site, is the physiological luteolytic signal. The consequence of its receptor binding seems to be the blockade of a gonadotrophic stimulus, which in turn determines (1) the decrease in progesterone synthesis and (2) the induction of 20 alpha-hydroxysteroid dehydrogenase.     

Three new Ecuadorian species of Axinaea (Melastomataceae)

Three new Ecuadorian species of Axinaea (Melastomataceae) are described: Axinaea flava, A. glauca, and A.lawessonii. All three species are endemic to southern Ecuador. Axinaea flava and A.glauca grow in the transition zone between montane forest and pbramo. They share characters such as shrubby habit, dense to moderate pubescence and coriaceous, rigid, erect leaves, which may be related to their high altitude habitat. Axinaea flava is the only species of the genus with a yellow corolla. Axinaea glauca, a shrub less than 1 m high, is the smallest Axinaea species known. Field observations show that these two species have a restricted habitat and their known populations are small, probably less than 100 individuals. The third species, A.lawessonii, grows in wet montane forests. It can grow as a shrub or a slender tree and its leaves are glabrous and less rigid than those of A.flava and A.glauca, characters which are probably a consequence of the more humid and benign habitat. Axinaea lawessonii is the only species of the genus in which the leaf margins have uncinate teeth. The species is rather frequent in southern Ecuador and has been collected in a dozen localities, most of which are within the Podocarpus National Park.     

Cell-free synthesis of proteins related to sn-glycerol-3-phosphate transport in Escherichia coli.

An Escherichia coli periplasmic protein (GlpT) related to sn-glycerol-3-phosphate transport was synthesized in a cell-free system directed by hybrid plasmic ColE1-glpT DNA. The in vitro product cross-reacted with antisera against the purified protein. The ColE1-glpT DNA-directed cell-free system was induced by sn-glycerol-3-phosphate and phosphonomycin and was dependent on cyclic AMP. The in vitro-synthesized protein showed the characteristics of a multimeric protein, as did the purified periplasmic protein. The main proportion of the newly synthesized product had a higher molecular weight than the mature protein found in the periplasm of cells and showed a more positive charge in two-dimensional gel electrophoresis. Thus, a proportion of this protein is presumed to be synthesized in vitro as a precursor. The cell-free system yielded a second protein that is likely to be also coded for by the glpT operon. This protein had a molecular weight of approximately 33,000 in sodium dodecyl sulfate-acrylamide gel electrophoresis and behaved like an intrinsic membrane protein.     

The Use of “Use Value”: Quantifying Importance in Ethnobotany

Economic Botany - The Use of “Use Value”: Quantifying Importance in Ethnobotany. Use value (UV) is an index widely used to quantify the relative importance of useful plants. It combines...     

Comparing predictive validity of four ballistic swing phase models of human walking

It is unclear to what extent ballistic walking models can be used to qualitatively predict the swing phase at comfortable walking speed. Different study findings regarding the accuracy of the predictions of the swing phase kinematics may have been caused by differences in (1) kinematic input, (2) model characteristics (e.g. the number of segments), and (3) evaluation criteria. In the present study, the predictive validity of four ballistic swing phase models was evaluated and compared, that is, (1) the ballistic walking model as originally introduced by Mochon and McMahon, (2) an extended version of this model in which heel-off of the stance leg is added, (3) a double pendulum model, consisting of a two-segment swing leg with a prescribed hip trajectory, and (4) a shank pendulum model consisting of a shank and rigidly attached foot with a prescribed knee trajectory. The predictive validity was evaluated by comparing the outcome of the model simulations with experimentally derived swing phase kinematics of six healthy subjects. In all models, statistically significant differences were found between model output and experimental data. All models underestimated swing time and step length. In addition, statistically significant differences were found between the output of the different models. The present study shows that although qualitative similarities exist between the ballistic models and normal gait at comfortable walking speed, these models cannot adequately predict swing phase kinematics.     

Validity of the Pedar Mobile system for vertical force measurement during a seven-hour period

Objective measurement of weight bearing during a long-term period can give insight into the postoperative loading of the lower extremity of orthopedic patients to avoid complications. This study investigated the validity of vertical ground reaction force measurements during a long-term period using the Pedar Mobile insole pressure system, by comparing it with a Kistler force platform. In addition, the validity of a new sensor drift correction algorithm to correct for offset drift in the Pedar signal was evaluated. Ground reaction force data were collected during dynamic and static conditions from five healthy subjects every hour for 7 h. A mean offset drift of 14.6% was found after 7 h. After applying the drift correction algorithm the Pedar system showed a high accuracy for the second peak in the ground reaction force-time curve (1.1 to 3.4% difference, p>0.05) and step duration (-2.0 to 4.4% difference, p>0.05). Less accuracy was found for the first peak in the ground reaction force-time curve (5.2 to 12.0% difference; p<0.05 for the first 3 h, p>0.05 for the last 4 h) and, consequently, in the vertical force impulse (5.5 to 11.0% difference, p>0.05). The Pedar Mobile system appeared to be a valid instrument to measure the vertical force during a long-term period when using the drift correction program described in this study.