Studies on the role of oxytocin in late pregnancy in the pregnant rhesus monkey: plasma concentrations of oxytocin in the maternal circulation throughout the 24-h day and the effect of the synthetic oxytocin antagonist [1-beta-Mpa(beta-(CH2)5)1,(Me(Tyr2, Orn8] oxytocin on spontaneous nocturnal myometrial contractions

Previous observations have demonstrated that under several different circumstances the pregnant rhesus monkey myometrium shows a spontaneous shift in activity from contractures to contractions around the beginning of the hours of darkness. Preliminary studies were conducted to demonstrate that the competitive oxytocin antagonist ([1-beta-Mpa(beta-(CH2)5)1,) Me)Tyr2, Orn8] oxytocin was effective in vivo in inhibiting oxytocin induced contraction type myometrial activity in the pregnant rhesus monkey in the last third of gestation. Four pregnant and one fetectomized rhesus monkey (98-141 days gestation) received one intra-arterial dose of oxytocin antagonist to study its ability to inhibit myometrial contractions occurring spontaneously around the onset of prevailing nighttime. In three pregnant monkeys (105-121 days gestation) maternal arterial plasma oxytocin levels were measured at 4-h intervals for a period of 48 h. Maternal plasma oxytocin concentration was maximal during the early hours of darkness and demonstrated a significant 24-h rhythm. From the combined results of both experiments it may be concluded that circulating oxytocin and/or a change in one of the many potential regulatory sites for oxytocin function plays a role in the switch from contractures to contractions that occurs around the beginning of the hours of darkness.     

Identification of a kinesin-like microtubule-based motor protein in Dictyostelium discoideum.

Dictyostelium discoideum, a unicellular eukaryote amenable to both biochemical and genetic dissection, provides an attractive system for studying microtubule-based transport. In this work, we have identified microtubule-based motor activities in Dictyostelium cell extracts and have partially purified a protein that induces microtubule translocation along glass surfaces. This protein, which sediments at approximately 9S in sucrose density gradients and is composed of a 105 kd polypeptide, generates anterograde movement along microtubules that is insensitive to 5 mM NEM (N-ethyl-maleimide) but sensitive to 200 microM vanadate, and has similar nucleotide-dependent microtubule binding properties to those of kinesins purified from mammals, sea urchin and Drosophila. This kinesin-like molecule from Dictyostelium, however, is immunologically distinct from bovine and squid neuronal kinesins and supports microtubule movement on glass at four-fold greater velocities (2.0 versus 0.5 microns/sec). Furthermore, AMP-PNP (adenylyl imidodiphosphate), which promotes attachment of previously characterized kinesins to microtubules, decreases the affinity of the Dictyostelium kinesin homolog for microtubules. Thus, an AMP-PNP-induced rigor binding may not be a characteristic of kinesins from lower eukaryotes.     

Rapid changes in the expression of inhibin alpha-, beta A-, and beta B-subunits in ovarian cell types during the rat estrous cycle

Distributions of inhibin alpha-, beta A-, and beta B-subunits in different ovarian compartments were studied in cycling female rats by in situ hybridization with complementary RNA probes and using immunohistochemical localization with antibodies selective for each inhibin subunit. Consistent with earlier studies showing inhibin production by granulosa cells of maturing follicles, we also detected mRNAs for inhibin alpha-, beta A-, and beta B-subunits in granulosa cells of these follicles. However, based on immunohistochemistry and in situ hybridization, we found that inhibin alpha- is not only expressed in granulosa cells of mature follicles but in follicles at all stages of maturation, including primary to tertiary follicles. A number of primordial follicles also contained alpha mRNA and immunodetectable alpha-subunit. Interestingly, theca interna and interstitial gland cells contained inhibin alpha mRNA and alpha-subunit. Low levels of inhibin alpha immunoreactivity as well as specific hybridization to the complementary inhibin alpha mRNA probe were observed in newly formed luteal tissue. beta-Subunits, on the other hand, were detected exclusively in granulosa cells of healthy tertiary follicles. The changes in expression of inhibin alpha-, beta A-, and beta B-subunits were more pronounced during the follicular phase of the cycle: inhibin alpha reached its highest level in granulosa cells, theca interna, and interstitial gland cells a few hours after the LH/FSH surge, while at the same time the beta-subunits decreased dramatically in granulosa cells of mature follicles. Immediately before ovulation (estrus 0200 h), the alpha-subunit sharply declined in preovulatory follicles and was present mainly in granulosa cells from nonovulatory follicles at various stages of maturation. At that time, the beta A- and beta B-subunits could not be detected in preovulatory follicles but were localized mainly in small tertiary follicles (less than 300 microns). Unlike for the alpha- and beta B-subunits, beta A mRNA and immunoreactivity was present in large tertiary follicles (approximately 600 microns) immediately before ovulation. The present findings support the hypothesis that a decrease in inhibin production could be responsible for the secondary FSH surge observed early on estrus. This could be initiated by a change in the ratios of activin-inhibin production by decreasing first, the levels of beta-subunits, second, the levels of alpha-subunit, and third, by a resurgence of activin A produced mainly by granulosa cells from large tertiary follicles.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bacterial flagellar diversity and significance in pathogenesis

Bacterial flagella are structurally diverse, ranging from the thoroughly investigated model examples found in Escherichia coli and Salmonella typhimurium to the more exotic sheathed flagella of, for example, Helicobacter pylori, and the complex multi-flagellin endoflagella found in many spirochaetes. We summarize some of the emerging structural and genetic findings relating to these more novel flagellar types, and outline their possible significance in the pathogenicity of some medically important bacteria.     

Oxytocin potentiates the ACTH-releasing activity of CRF(41) but not vasopressin

The effects of CRF(41), oxytocin (OT), and arginine vasopressin (AVP) on ACTH secretion were studied alone and in combination in an in vitro system of superfused rat hemipituitaries. CRF(41) (10(-9)M) and AVP (10(-8)M) alone produced a significant increase in ACTH secretion while OT (10(-8)M) alone had no effect. However the same concentration of OT markedly potentiated the ACTH response to CRF(41) while having no effect on the ACTH response to AVP. The data support a physiologic role for OT in the regulation of ACTH secretion.     

Synthetic human pancreatic growth hormone releasing factor (GRF) stimulates growth hormone secretion in the domestic fowl (Gallus domesticus)

Synthetic human pancreatic Growth Hormone-Releasing Factor (hpGRF) elevated the plasma concentration of growth hormone (GH) in young and adult domestic fowl. This in vivo effect of hpGRF appeared to be largely similar for both the 32 amino-acid (hpGRF 1-32) or 40 amino-acid (hpGRF 1-40) polypeptide, although the effect of hpGRF 1-32 was more prolonged than that of hpGRF 1-40 in adult domestic fowl. The increase in plasma GH concentrations following hpGRF administration (10 micrograms/kg) was somewhat greater in young than adult chickens (the increase in plasma concentration of GH being 230 ng/ml at 1 week old, 282 ng/ml at 6 week old, 241 ng/ml at 10 weeks and 150 ng/ml in adults). In the adult domestic fowl hpGRF stimulated a greater increase in the plasma concentration of GH than did thyrotropin-releasing hormone (TRH). However in the young chicks TRH was more active. The in vitro release of GH from dispersed chicken pituitary cells was elevated by hpGRF (1-32) and hpGRF (1-40).     

Nomograms for Calculation of Heat Loss

Two nomograms are presented. The first enables the mean surface and body temperatures and the body heat content of a patient of given weight to be determined from measurements of skin temperature at three sites and of the core (rectal) temperature. The second enables the change in heat content of such a patient to be determined from the change in mean body temperature.     

Molecular architecture of adult locust cuticle at the electron microscope level

It is shown that locust adult endocuticle consists of a daily alternation of two types of chitin-protein architecture: (i) non-lamellate day layers with microfibrils oriented in a preferred direction, traversed by pore canals whose shape resembles an untwisted ribbon, (ii) lamellate night layers with helicoidally oriented microfibrils traversed by pore canals shaped like regularly twisted ribbons. Uncoupling the circadian clock which normally controls the timing of these two types leads to growth of cuticles which are organized like one or the other throughout. We can thus experimentally change the architecture of the microfibrils which in turn changes the pore canals.     

Inhibin secretion during the rat estrous cycle: relationships to FSH secretion and FSH beta subunit mRNA concentrations

Serum inhibin and FSH and FSH beta subunit mRNA levels were measured at 3h intervals throughout the 4 day estrous cycle in female rats and hourly between 1000 and 2400 h of proestrus. On proestrus, serum inhibin concentrations fell during the late morning-early afternoon, then increased transiently during the late afternoon gonadotropin surges. Inhibin levels decreased during the late evening of proestrus, coincident with the FSH surge-related rise in FSH beta mRNA levels. Serum inhibin remained relatively stable during estrus and early metestrus, but rose during the late evening of metestrus and remained elevated until early diestrus. FSH beta mRNA levels were elevated on late estrus and early metestrus and declined during the evening of metestrus as serum inhibin levels increased. These data show that concentrations of serum inhibin change during the estrous cycle and that a general inverse relationship exists between serum inhibin and FSH levels and FSH beta mRNA concentrations in the pituitary. This suggests that inhibin may inhibit FSH beta gene expression and FSH secretion during the 4 day cycle in female rats.