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Pituitary adenylate cyclase-activating polypeptide (PACAP) releases LH and FSH from anterior pituitary cells. Although this effect is relatively weak, it has a strong sensitizing action on GnRH-induced gonadotropin secretion. Here we investigated the possibility that ovarian steroids, which are well-known modulators of LH secretion, interact with PACAP and GnRH in pituitary gonadotrophs. Rat pituitary cells were treated for 48 h with vehicle, 1 nmol/l estradiol, 1 nmol/l estradiol + 100 nmol/l progesterone or 48 h with 1 nmol/l estradiol and 4 h with 100 nmol/l progesterone. The cells were stimulated for 3 h with 1 nmol/l GnRH or 100 nmol/l PACAP. Estradiol treatment alone enhanced basal as well as GnRH- or PACAP-stimulated LH secretion. LH release was facilitated by additional short-term progesterone treatment. Long-term treatment with estradiol and progesterone led to reduced LH responses to GnRH and PACAP. Neither treatment paradigms affected cAMP production. However, estradiol treatment led to enhanced cAMP accumulation in quiescent or GnRH-stimulated cells. PACAP-induced increases of cAMP production were inhibited by estradiol treatment. After 7-h preincubation with 10 nmol/l PACAP, cells responded with enhanced LH secretion to GnRH stimulation. When steroid pretreatment was performed the responsiveness of gonadotrophs to low concentrations of GnRH was still increased. In contrast, at high concentrations of GnRH the sensitizing action of PACAP on agonist-induced LH secretion was lost in steroid-treated cells. There were no significant differences between the steroid treatment paradigms. It is concluded that estradiol but not progesterone acts as a modulator of adenylyl cyclase in gonadotrophs. The stimulatory effect of estradiol is thought to be involved in its sensitizing action on agonist-induced LH secretion. The inhibitory effect of estradiol on PACAP-stimulated adenylyl cyclase activities seems to be responsible for the loss of its action to sensitize LH secretory responses to GnRH.

A cycle-by-cycle analysis of HC emissions from each cylinder of a four-stroke V-6, 3.3 L production engine was made during cold start. The HC emissions were measured in the exhaust port using a high frequency flame ionization detector (FID). The effect of the initial startup position of the piston and valves in the cycle on combustion and HC emissions from each cylinder was examined. The mass of fuel injected, burned and emitted was calculated for each cycle. The equivalence ratio of the charge in the firing cycles was determined. The analysis covered the first 120 cycles and included the effect of engine transients on HC emissions.

The modern spark ignition automotive engine, though fundamentally similar to those having diverse nonautomotive applications, is distinct with respect to many details. The distinct features of automotive engines reflect characteristics of their duty cycle which impose a unique set of design constraints. It is within the realm of these design constraints that this treatment of the subject of valve events is based. Throughout this discussion the term “valve event” denotes the creation of flow area in a phased relationship with piston motion through which the gas exchange process is conducted. This is a general term which includes the timing, lift and size of engine valves.

Die Kinetik der Pyrolysereaktion von 0F, wird in einem Monel-Stromungsapparat mit Durchmischung bei Temperaturen zwischen 330 und 431°C untersucht.

A cooperative sea ice remote sensing experiment was conducted in the eastern Beaufort Sea and Mould Bay area during the freeze-up period in October 1981. Airborne millimeter-wave imagery at 90, 140, and 220 GHz, and nadir microwave radiometric measurements at 19, 22, and 31 GHz, were made from a U. S. Naval Research Laboratory aircraft, while the Canadian Atmospheric Environment Service conducted an extensive concurrent surface measurement program. This study demonstrates for the first time the high-resolution capability of 90 GHz to investigate detailed ice morphology and to define ice types. The 140 and 220 GHz imagery is the first ever made of sea ice at these high frequencies. Emissivities are determined for young ice, second-year ice (SY), multiyear ice (MY), new ice, old shorefast ice, and open water. The young ice exhibits the emissivity typical of first-year (FY) ice types, i.e., near unity and independent of frequency. The emissivities of new ice and open water increase with frequency, and that of MY ice decreases with frequency. Those of SY ice and old shorefast ice, measured here for the first time, also decrease with frequency but are larger in value than the MY emissivity. Ice type discrimination is optimum at 90 GHz, i.e., the spread in microwave signature between FY ice and old ice (SY and MY) is greatest at 90 GHz. The MY emissivity is lower than that of open water at both 90 and 140 GHz. The measurements presented here provide a basis for development of algorithms to exploit the potential of the Mission Sensor Microwave/Imager (SSM/I) to be launched on a Defense Meteorological Satellite in 1985 and, in particular, the 85.5-GHz SSM/I channels for ice type, concentration, and edge determination.