The effect of a depot injection of recombinant bovine somatotropin on follicular development and embryo yield in superovulated Holstein heifers

Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P 0.63), but it was negatively correlated with progesterone (P 相似文献   

Source of an egg kairomone for Trissolcus basalis, a parasitoid of Nezara viridula

Abstract. The eggs of the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), are successfully attacked by Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae) and are recognized as hosts by a secretion applied to the egg chorion. This secretion is produced by the follicular cells in the proximal region of the ovariole of the female pentatomid and functions as an adhesive for attaching the eggs to the oviposition substrate. The adhesive and kairomone activity could be partially removed with water. This water extract elicited host recognition behaviour in T. basalis when applied to glass beads which stuck together as the extract dried. The adhesive and kairomonal activity was removed completely with acetone since acetone-washed host eggs were not recognized by T. basalis. Application of the acetone extract to glass beads stimulated ovipositional probes by T. basalis. The adhesive appeared to be composed of a mucopolysaccharide–protein complex.     

MyoD induced cell cycle arrest is associated with increased nuclear affinity of the Rb protein.

In studying the mechanism through which the myogenic determination protein MyoD prevents entry into the S phase of the cell cycle, we have found a relationship between MyoD and the retinoblastoma (Rb) tumor suppressor protein. By direct needle microinjection of purified recombinant MyoD protein into quiescent fibroblasts, which were then induced to proliferate by serum, we found that MyoD arrested progression of the cell cycle, in agreement with studies utilizing expression constructs for MyoD. By studying temporal changes in cells injected with MyoD protein, it was found that MyoD did not prevent serum induced expression of the protooncogene c-Fos, an event that occurs in the G0 to G1 transition of the cycle. Injection of the MyoD protein as late as 8 h after the addition of serum still caused an inhibition in DNA synthesis, suggesting that MyoD inhibits the G1 to S transition as opposed to the G0 to G1 transition. MyoD injection did not prevent the expression of cyclin A. However MyoD injection did result in a block in the increase in Rb extractibility normally seen in late G1 phase cells. As this phenomenon is associated with the hyperphosphorylation of Rb at this point in the cell cycle and is correlated with progression into S phase, this provides further evidence that MyoD blocks the cycle late in G1.     

Effect of ultrasonically-guided follicle aspiration on estrous cycle and follicular dynamics in Holstein cows

Two experiments were conducted to test the effect of ultrasonically-guided follicle aspiration on estrous cycle and follicular dynamics in Holstein cows. The objective of the first experiment was to determine if aspiration of all visible follicles would influence the estrous cycle. All visible follicles > or = 5 mm in diameter were punctured and the oocytes aspirated once during the second and fourth cycle, with no aspirations occurring during Cycles 1, 3 and 5 in 4 Holstein cows. Between aspirations the follicles were scanned ultrasonically every 2 to 3 d to monitor follicular waves. Estrus was monitored twice daily and plasma progesterone concentrations were measured daily. The inter-estrus periods were significantly longer when aspiration was performed than in the 3 cycles in which aspiration did not occur (25.0 vs 21.1 d; P < 0.01). To determine the maximum number of follicles harvestable on a continuing basis, a second experiment was conducted to contrast unstimulated cows subjected to ultrasonically-guided oocyte collection twice-weekly with animals from which oocytes were collected once a week after gonadotrophin stimulation. All visible follicles of multiparous Holstein cows were aspirated every 3 or 4 d (unstimulated group, n = 4), and the total number of follicles was compared with the number of follicles in cows that were aspirated weekly after 400 mg FSH were administered over 2 d (stimulated, n = 6). The study continued for 8 consecutive weeks. The weekly mean number of follicles available for aspiration in the unstimulated cows was 15.7 +/- 3.3 (mean +/-SEM), which was not different from the 14.2 +/- 1.9 follicles available for aspiration from the FSH-stimulated cows. Within the unstimulated cows, there was an increased number of follicles available for aspiration over time during the period of study (P < 0.001). The number of follicles available for aspiration from the stimulated cows did not change, but plasma concentrations of progesterone increased over time as persistent luteal tissue developed on the ovaries.     

Stereognostic coordination chemistry 4 the design and synthesis of a selective uranyl ion complexant

A new approach to ligand design for the sequestration of metal-oxo cations has been called stereognostic coordination chemistry, in that the ligand incorporates a traditional Lewis base coordination to the metal center and a hydrogen bond donor to interact with the oxo group. This paper reports the synthesis of ligands that are more rigid and sterically predisposed to bind the targeted UO₂²⁺ cation. These are the tripod ligands tris-N,N′,N′′-[2-(2-carboxy-phenoxy)ethyl]-1,4,7-triazacyclononane bis-hydrochloride (ETAC · 2HCl) and tris-N,N′,N′′-[2-(2-carboxy-4-decyl-phenoxy)ethyl]-1,4,7-triazacyclononane tris-hydrochloride (DETAC · 3HCl), which chelate uranyl with a tris-carboxylate coordination sphere and provide a hydrogen bond donor through a protonated amine on the triazacyclononane macrocycle to interact with one uranyl oxo atom. Structural models predict that upon uranyl binding the hydrogen bond donor must point directly towards the oxo atom, enforcing a stereognostic interaction. Both ETAC and DETAC chelate the uranyl ion; DETAC is a powerful extractant and will quantitatively extract uranyl into an organic phase at pH 1.9 and above. The extraction coefficient is estimated to be 10¹⁴ in neutral aqueous conditions. Vibrational spectra of ¹⁸O labeled UO₂²⁺ have been used to probe the stereognostic coordination to uranyl utilizing hydrogen bonding.     

Breeding success and chronology of Wood Storks Mycteria americana in northern and central Florida, U.S.A.

The breeding success and chronology of Wood Storks Mycteria americana were studied at eight colonies in northern and central Florida during 1981–1985. Mean ± s.d. clutch size for all colony-years was 3.07 ± 0.56 (n = 2694 nests), with three-egg clutches (72%) most frequent. Mean clutch size among all colonies and years ranged from 2.73 ± 0.55 to 3.41 ± 0.61. Many colonies exhibited significant negative trends in clutch size with, hatching date because of a proportional decrease in four-egg clutches later in the season. Mean colony clutch size was not correlated with nest numbers, nesting density or mean hatching date within most years. Mean ± s.d. number of fledglings for all colonies and years was 1.29 ± 1.16 fledglings per nest (n = 2812 nests). Mean annual fledging rates in colonies ranged from 0 (colony failed) to 2.66 fledglings per nest. Most breeding failure occurred prior to egg hatching, and the second highest mortality occurred between hatching and 2 weeks of age. Four-egg clutches fledged more storks than three-egg clutches, which in turn were more successful than two-egg clutches. However, all clutch sizes showed similar fledgling per egg rates. The seasonal decline in productivity was associated proportionally with smaller clutch sizes later in the breeding season. An increase in mean hatching date was correlated with an increase in latitude. There was greater within-year breeding synchrony among colonies than interyear breeding synchrony within each colony. Breeding synchrony was not correlated with mean hatching date, latitude, longitude, nest numbers or nesting density.     

A New Malaria Parasite Plasmodium (Sauramoeba) heischi in Skinks (Mabuya striata) from Nairobi, with a Brief Discussion of the Distribution of Malaria Parasites in the Family Scincidae

ABSTRACT. A new species of malaria parasite, Plasmodium (Sauramoeba) heischi , is described from African skinks (Mabuya striata). Eleven individuals of 90 specimens collected in Nairobi were found to be infected. The new parasite is a large species, characterized by spindle-shaped gametocytes, the female often with a subterminal nucleus. The schizonts produce up to 65 nuclei and cause great hypertrophy and distortion of the host cell. Although similar to P. (Sauramoeba) giganteum in dimensions and merozoite numbers, P. heischi is easily distinguished by gametocyte and schizont shapes.     

The Spontaneous Formation of Antheridia in Onoclea is not Blocked by Light

Onoclea sensibilis gametophytes were grown from spores on ashedsoil and agar to determine if the spontaneous formation of antheridiacan be blocked by light. Under most conditions, dark-grown gametophytesformed antheridia later than or at the same time as gametophytesgrown in the light. Under no circumstances was there a rapidonset of maleness in the dark. These results contradict thehypothesis that, in Onoclea, antheridiogen is required to inducemaleness because light inhibits the formation of antheridia.In the light, antheridia formed on heart-shaped thalli. In darkness,antheridia formed on filamentous gametophytes. The timing ofonset of maleness was affected by temperature and the presenceof sucrose. The effect of sucrose on the comparison betweenlight and dark treatments depended on both substrate and temperature Onoclea sensibilis, L., sensitive fern, fern gametophytes, sexuality, light-induced block