Seminal inhibin--prospects for immunocontraception.

Passive immunization of adult rats, hamsters and marmosets with rabbit anti-seminal inhibin resulted in complete or partial block of fertility. The antiserum treatment presumably neutralized endogenous inhibin resulting in an unopposed rise in circulating FSH. This probably led to a refractoriness of the testes to FSH resulting in complete spermatogenic arrest. Nevertheless, there was no change in the mating behaviour of the animals. The antibodies also affected the epididymal spermatozoa by causing large scale agglutination.     

Configuration of PKCα-C2 Domain Bound to Mixed SOPC/SOPS Lipid Monolayers

X-ray reflectivity measurements are used to determine the configuration of the C2 domain of protein kinase Cα (PKCα-C2) bound to a lipid monolayer of a 7:3 mixture of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1-stearoyl-2-oleoyl-sn-glycero-3-phosphoserine supported on a buffered aqueous solution. The reflectivity is analyzed in terms of the known crystallographic structure of PKCα-C2 and a slab model representation of the lipid layer. The configuration of lipid-bound PKCα-C2 is described by two angles that define its orientation, θ = 35° ± 10° and φ =210° ± 30°, and a penetration depth (=7.5 ± 2 Å) into the lipid layer. In this structure, the β-sheets of PKCα-C2 are nearly perpendicular to the lipid layer and the domain penetrates into the headgroup region of the lipid layer, but not into the tailgroup region. This configuration of PKCα-C2 determined by our x-ray reflectivity is consistent with many previous findings, particularly mutational studies, and also provides what we believe is new molecular insight into the mechanism of PKCα enzyme activation. Our analysis method, which allows us to test all possible protein orientations, shows that our data cannot be explained by a protein that is orientated parallel to the membrane, as suggested by earlier work.     

Changes in vegetation patterns on the margins of a constructed wetland after 10 years

Summary A constructed urban wetland in Adelaide was surveyed 18 months and 10 years after construction to see how shoreline vegetation, soil electrical conductivity (EC), texture and pH changed over time and to provide data for future site management. Multivariate analysis detected four plant associations at 18 months: salt‐tolerant taxa on conductive clays; a weed‐dominated community on lower EC soil; and two smaller waterlogged, low EC clusters dominated by Common Reed (Phragmites australis) and Sea Club‐Rush (Bolboschoenus caldwellii), respectively. At 10 years, site cover and heterogeneity was higher, with the margins dominated by Phragmites and salt‐tolerant species. EC was much lower and more uniform, and the soils were heavier and more alkaline. Managed storm water flushing apparently lowered soil EC, but possibly also disturbed the shoreline. However, weeds were still common, and the potential for domination by Phragmites at the expense of other native shoreline species means that ongoing monitoring and hydrological and vegetation management are essential to maintain site habitat diversity.     

Seasonal Variation in Human Salivary Cortisol Concentration

Measurement of cortisol concentration can contribute important information about an individual's ability to adjust to various environmental demands of both physical and psychosocial origin. However, one uncertainty that affects the possibilities of correctly interpreting and designing field studies is the lack of observations of the impact of seasonal changes on cortisol excretion. For this reason, the month‐to‐month changes in diurnal cortisol concentration, the awakening cortisol response (ACR), maximum morning concentration, and fall during the day were studied in a group of 24 healthy men and women 32 to 61 yrs of age engaged in active work. On one workday for 12 consecutive months, participants collected saliva at four time points for determination of cortisol: at awakening, +30 min, +8 h, and at 21:00 h. Data were analyzed by a repeated measures design with month (12 levels) and time‐of‐day (4 levels) as categorical predictors. Cortisol concentrations were analyzed on a log scale. The diurnal pattern of cortisol was similar across months (interaction between month and time of day: p>0.4). The main effects of month and time‐of‐day were statistically significant (p <0.001). Highest concentrations were observed in February, March, and April, and lowest concentrations were observed in July and August. There were no statistically significant effects in any of the other measures, or between men and women. In conclusion, a seasonal variation in salivary cortisol concentrations was detected in an occupationally active population. Thus, seasonal variation needs to be taken into account when designing and evaluating field studies and interventions and when making comparisons across studies.     

Helix nucleation kinetics from molecular simulations in explicit solvent

We study the reversible folding/unfolding of short Ala and Gly-based peptides by molecular dynamics simulations of all-atom models in explicit water solvent. A kinetic analysis shows that the formation of a first alpha-helical turn occurs within 0.1-1 ns, in agreement with the analyses of laser temperature jump experiments. The unfolding times exhibit Arrhenius temperature dependence. For a rapidly nucleating all-Ala peptide, the helix nucleation time depends only weakly on temperature. For a peptide with enthalpically competing turn-like structures, helix nucleation exhibits an Arrhenius temperature dependence, corresponding to the unfolding of enthalpic traps in the coil ensemble. An analysis of structures in a "transition-state ensemble" shows that helix-to-coil transitions occur predominantly through breaking of hydrogen bonds at the helix ends, particularly at the C-terminus. The temperature dependence of the transition-state ensemble and the corresponding folding/unfolding pathways illustrate that folding mechanisms can change with temperature, possibly complicating the interpretation of high-temperature unfolding simulations. The timescale of helix formation is an essential factor in molecular models of protein folding. The rapid helix nucleation observed here suggests that transient helices form early in the folding event.     

Reproductive seasonality in female Iberian red deer (Cervus elaphus hispanicus)

This study characterized the seasonal pattern of luteal cyclicity in Iberian red deer (n=16), by measuring plasma progesterone concentrations in hinds (female red deer) twice per week from calving (May and June) 1996 until May 1997. In eight of these hinds we also examined plasma prolactin profiles to assess seasonal responses to photoperiod. Plasma progesterone concentration in the 16 hinds studied indicated that the reproductive pattern is seasonal, and lasts for 5.73 +/- 0.27 months. After calving, progesterone levels remained basal (no luteal activity) for several months, except in a hind that lost her calf just after calving, and thus did not have to suckle it. This hind showed two consecutive estrus cycles in the month following calving, which suggests that suckling has an inhibiting effect on the resumption of ovarian activity. These results also showed that as long as the hinds do not become pregnant, they show between 5 and 10 estrus cycles per reproductive season (8.06 +/- 0.35), ranging between 105 and 249 days from onset of the first cycle to end of the last one. Uninterrupted cycling lasted for 3.5-6.4 months (mean, 4.6 +/- 0.24). Cyclic luteal activity was found from October to February in all hinds, with a smaller, but notable proportion in September (56.25%) and March (68.8%), whereas it was negligible in the remaining period. Our results show a reproductive season similar to or longer than that recorded by other authors. Prolactin plasma concentrations showed a yearly trend following that of photoperiod, with peak concentrations from April to July, a decrease in August, minimal concentrations from September to February and a sharp increase in March.     

Determination of cortisol in human saliva using liquid chromatography-electrospray tandem mass spectrometry

The aim of this work was to develop a method for determination of cortisol in saliva by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Saliva was sampled on Salivette tubes. These were centrifuged, deuterium-labeled cortisol was added as internal standard and the proteins precipitated by acetonitrile. The supernatant was evaporated, dissolved in methanol acidified with acetic acid and analyzed by LC-MS-MS. The with-in run precision, tested by pooling saliva samples from volunteers and then analyzing these in a single run, was found to be 7% at 0.7 microgram l(-1). The between-run precision was tested by analysis of the same samples at different days and found to be 11% at 2.5 microgram l(-1). The limit of quantification was 0.5 microgram l(-1). The method was applied for analysis of saliva samples from three volunteers during their last week before vacation and the first and second week on vacation. In addition, the method was compared to analysis by an immunological method. The values from the immunological method were 2.7 times higher than the LC-MS-MS results.     

Milk intake and production curves and allosuckling in captive Iberian red deer, Cervus elaphus hispanicus

In two experiments, we compared milk intake (assessed by weighing calves before and after suckling) and milk production (by hand milking hinds) in Iberian red deer both when calves sucked their mothers together (group-suckling experiment) and when mother and offspring were isolated (isolation-suckling experiment). In both experiments, the general lactation curve for calves increased to a peak and then decreased (type I, standard lactation curve in mammals), whereas the curve for hinds decreased from the start (type II). However, in the experiment on group suckling, calves ingested 17.2% more milk than that produced by their mothers from weeks 6 to 20. In both isolation- and group-suckling experiments, hinds showed an overproduction of milk decreasing from weeks 1 to 5. This decreasing overproduction coincides with a similar trend in calf mortality reported in the literature and might thus be aimed at ensuring calves have sufficient nutrients when mortality is highest. In addition, allosuckling observations in the group-suckling experiment showed an inverse relationship between milk production and percentage of allosucking attempts. Allosucking attempts were also more frequent after the milk overproduction period. Both findings suggest that allosuckling is a response to compensate for a reduced maternal milk supply. Copyright 2000 The Association for the Study of Animal Behaviour.     

Effect of trehalose and EDTA on cryoprotective action of ram semen diluents

To obtain better ram semen extenders for artificial insemination (AI), we developed effective trehalose-containing hypertonic diluents. The cryoprotective action of trehalose has been explained by its dehydrating activity and interaction with cell membranes. Accordingly, we tested the cryopreserving capacity of different combinations of a Salamon's modified plus trehalose extender with EDTA. Evaluations were based on the percentage of motile spermatozoa and acrosome integrity, measured after thawing and after a 4-h post-thaw resistance test at 37 degrees C. We conclude that the combination of trehalose plus EDTA confers the highest cryopreserving activity tested, not only for freeze-thawing but also for post-thawing resistance, possibly by removing calcium from the medium thereby preventing cation competition with trehalose for membrane-binding sites.