Embryo transfer in two-year-old donor mares

Embryos were collected from two-year-old donor mares and transferred surgically during 1983 and 1984. The overall embryo recovery rate from two-year-old donors was 36.3%. Over both years, 71.4% of the donors ($\text{30}\text{42}$) provided at least one embryo. There was a trend both years for slightly higher embryo recovery rates prior to August 1 (47.7%), as compared to after August 1 (31.1%). Pregnancy rates in recipient mares after surgical embryo transfer were not affected by month of the breeding season. However, there was a trend for improved pregnancy rates when embryos were transferred after August 1 (87.5%), as compared to before August 1 (70.0%). There was a 8.3% incidence of fetal loss between Days 15 and 35 of gestation in recipients. The incidence of fetal loss between Days 35 and 60 of gestation was 2.7%. Based on these data, the chance of obtaining a pregnancy from a two-year-old mare is 28.2% (36.3% recovery × 77.7% pregnancy rate). Thus embryo transfer may prove to be a beneficial tool for obtaining foals from two-year-old donor mares.     

Vegetation succession on the dunes near Oostvoorne,The Netherlands,since 1934, interpreted from air photographs and vegetation maps

The vegetation succession on the dunes near Oostvoorne, The Netherlands has been followed by means of a novel combination of repeated large-scale vegetation mapping and air photograph interpretation. Vegetation units have been discerned on the formation level because these could be distinguished fairly easily on the photographs and because the rates of change are appropriate to the time interval chosen. Nineteen formations were distinguished. Five 1:6250 maps were constructed, reflecting the formation pattern in 1934, 1943, 1959, 1972 and 1980. An overlay with 2736 grid points at 25 m field distance was used to quantify changes in the formation pattern.The results suggest a pronounced multiple pathway succession with nevertheless three principal trajectories of succession from pioneer to woodland vegetation. The outer dunes, which have originated since 1910, are distinct in successional characteristics from the inner dunes, which already existed but were released from heavy grazing pressure in 1910. The rate of change in the outer dunes was high in the beginning and is slowly decreasing eversince. In the inner dunes it went the other way around. Through visual extrapolation the likely formation patterns in 1910 and in 2000 were estimated.Transition frequencies proved highly variable for most formations. Moreover, strong spatial dependence was found. Limitations in the use of Markov models in cases of long-term succession in heterogeneous environments are discussed.Nomenclature follows the same sources as in van der Maarel et al. (1984).Field work carried out 1980–1981 when the authors were at the Division of Geobotany, University of Nijmegen. We thank Jos Rijntjes, Nijmegen, for his cooperation in the field. Vegetation maps were prepared and calculations performed at Uppsala. We thank the Foundation Het Zuid-Hollands Landschap, Rotterdam, for providing facilities and a grant for fieldwork as well as additional means to reproduce the vegetation maps. Two reviewers gave useful comments.     

On the Recovery of [3H]Noradrenaline from Different Metabolic Compartments of Rat Brain with Respect to the Role of Catechol-O-Methyltransferase

Abstract: Rats were treated with reserpine, desmethylimipramine, or carrier, either alone or in combination with tropolone. Either 10 min (t₁) or 1 h (t₂) after intraventricular injection of [³H]noradrenaline, they were decapitated. The total ³H activity and the recovery of [³H]noradrenaline were determined in tissue extracts from various brain regions. Maximum total ³H activity was measured at t₁ in all tropolone-treated rats; the mean sum of these results served as an estimate of the initial tissue concentration of [³H]noradrenaline. At t₁, 40–50% of the sum of [³H]noradrenaline and its metabolites was recovered unchanged in normal rats; reserpine and DMI reduced the recovery to 18–27%. In all groups, the decline of [³H]noradrenaline was retarded after t₁. Inhibition of catechol-O-methyltransferase by tropolone caused consistently elevated [³H]noradrenaline levels, but did not affect the metabolic rate after t₁ when compared with similarly pretreated, but tropolone-free rats. Thus, if catechol-O-methyltransferase was inhibited during the injection of [³H]noradrenaline, a higher percentage of the amine had been taken up into spaces with a slow noradrenaline turnover. The maximum increase was seen when the neuronal uptake, was inhibited by desmethylimipramine. This supported the hypothesis that an additional extraneuronal space exists, in addition to the known intraneuronal and extraneuronal compartments, which has a slow noradrenaline turnover. The tropolone effect on the noradrenaline recovery possibly shows that there might be a saturable “methylating system,” similar to that described for the periphery, in which catechol-O-methyltransferase is linked to the extraneuronal uptake₂. By affecting the access of noradrenaline to non-neuronal cells it might influence the rate of noradrenaline elimination from the intercellular space.     

The modulating influence of the fluidity of cell membrane on excision repair of DNA in UV-irradiated Escherichia coli

When the extent of liquid holding recovery (LHR) was measured as a function of the temperature at the time of liquid holding and the Arrhenius plot was made, two distinctive phases for the LHR were demonstrated in UV-irradiated RecA- derivative of E. coli ole28E1, which are unable to synthesize and degrade unsaturated fatty acids. The inflection temperatures were 17-18 degrees C, 23-24 degrees C and 28-30 degrees C for linoleate-, oleate- and elaidate-grown cells, respectively. These temperatures well corresponded to the phase transition temperatures of the cell membrane supplemented with the fatty acid. It is therefore concluded that at least a component involved in in vivo excision repair in E. coli is associated with cell membrane.     

Effects of water stress on the chlorophyll content,nitrogen level and photosynthesis of leaves of two maize genotypes

The dynamics of leaf chlorophyll level, nitrogen content, photosynthesis and stomatal conductance were followed in detail in two cultivars of maize (Zea mays) during a short period of water stress, applied at tasseling, and during the subsequent recovery phase. Plants used in the experiment were grown in sand-nutrient solution culture under field weather conditions. Water stress reduced chlorophyll levels, stomatal conductance and photosynthesis, but the nitrogen content of the leaves was not affected. It is concluded that the stress-induced loss of chlorophyll is not mediated by a lack of nitrogen. Considerable differences were observed between genotypes in the rate of post-stress recovery of chlorophyll level. Recovery, upon rewatering, of stomatal conductance and photosynthesis preceded that of chlorophyll level. Losses of up to 40% of leaf chlorophyll content were insufficient to affect rates of photosynthesis measured at mid-day.     

Protection by Desferrioxamine Against Histopathological Changes of the Liver in the Post-Oligaemic Phase of Clinical Haemorrhagic Shock in Dogs: Correlation with Improved Survival Rate and Recovery

Haemorrhagic shock was produced in anaesthetized dogs, by rapid arterial bleeding to mean arterial blood pressure 35 mmHg, and maintained oligaemic for 4 h followed by return of withdrawn blood(R0WB). Dogs were observed for 72 h after ROWB for survival and recovery, and, for histopathological (HP) studies on liver, dogs were sacrificed 2 h after ROWB in non-survival experiments. Desferrioxamine mesylate (25mg/kg) was administered intra-muscularly at 2,3 and 4h after blood loss in survival experiments and for HP studies the drug was given at 4 h in one group and at 2 h plus 4 h after blood loss in the second group. With the drug given at 3 or 4h, survival was 70% and 100% while in the 2h and the untreated groups it was 50%. Recovery was rapid in all the drug treated survivors, few became conscious within 30min. showed slight activity by 4-6 h, all were almost normally active by 24 and fully so by 72 h after ROWB. All the 5 control survivors remained unconscious/drowsy upto 24 h; 3 were sluggish at 72 h. By group analysis, serum iron elevation during the oligaemic and at the end of the post-oligaemic phase was less in the drug-treated animals. HP changes of shock in the liver studied by light microscopy, were markedly reduced in severity and were less prevalent in the drug-treated dogs. The salutory effects of desferrioxamine may be due to inhibition of iron catalyzed free-radical production and tissue damage, through its strong iron chelating action. It may have a therapeutic advantage in this emergency condition without the disadvantages of toxicity inherent in prolonged use.     

Modelling Mediterranean pasture dynamies

Pasture vegetation in an open woodland of Quercus rotundifolia subjected to periodic ploughing was sampled in spring during 8 consecutive years. The frequency of herbaceous species was recorded in a total of 69 permanent plots located on 5 adjacent sites with similar lithology, slope and orientation but differing in age since previous ploughing.Vegetation dynamics expressed as trajectories of permanent plots in a non-metric multidimensional scaling space has been modelled in terms of evironmental variables. By fitting a generalized linear model, the dynamics are shown to be related to years since last ploughing, geographical location of plots, total annual rainfall and November rainfall. Meteorological patterns of the sampling period are also described.Abbreviations GLM = Generalized Linear Model - NMDS = Non-metric Multi-Dimensional Scaling - UPGMA = Unweighted Pair-Group Method using Arithmetic Averages     

Buried seed populations on the volcano Mt. Usu,northern Japan,ten years after the 1977–78 eruptions

In 1987, a study on buried seed populations was conducted in the crater basin of Mt. Usu, a volcano located in northern Japan, where the vegetation had beeen almost completely destroyed by eruptions in 1977 and 1978. The former vegetation had consisted of grassland and broad-leaved forest. In the areas formerly occupied by this grassland and forest, 2128.0 and 1985.3 seeds per square meter, respectively, were extracted from 12 blocks of the former topsoil using a floattion method. This revealed that many seeds were still viable even after ten years of burial under thick volcanic deposits. The seeds were distributed more in sandy soil than in rocky soil of the former topsoil. Twenty-five species, most of which favored grassland, were detected in both the former grassland and forest. From comparison of α-and β-diversities between the grassland and forest, the structure of the buried seed population was considered likely to have been more diverse in the forest than in the grassland. The determinants of composition of the buried seed populations were discussed with reference to the former vegetation and soil characteristics.