Ultrastructural features of preovulatory oocyte maturation in superovulated cattle

Cows and heifers were induced to superovulate by treatment with PMSG or FSH. The ultrastructural features of the oocytes were related to the time of the LH peak and the progesterone/oestradiol-17 beta ratios in the follicular fluid. At 0-2 h after the LH peak the perivitelline space developed; at 9-12 h there was disconnection of the junctions between cumulus cell projections and oolemma, and the concomitant breakdown of the oocyte nucleus; at approximately 15 h there were spatial rearrangements in the ooplasm of (a) mitochondrial clusters from a peripheral to an even distribution and (b) vesicles from an even distribution to a more central location; at approximately 19 h there was abstriction of the first polar body with dislocation of mitochondrial clusters and vesicles towards the site of polar body formation; at 21-22 h there was migration of cortical granules to solitary positions along the oolemma and decrease in the sizes of Golgi complexes and, on some occasions, the smooth endoplasmic reticulum. These ultrastructural changes were accompanied by an increase in progesterone/oestradiol ratios in the follicular fluids. It is concluded that preovulatory oocyte maturation in gonadotrophin-stimulated cattle comprises nuclear as well as cytoplasmic changes accompanied by steroidogenic changes in the follicle, each of which are closely related to the time of the LH peak. However, some variation existed between animals, between follicular and oocyte maturation and even within oocytes between nuclear and cytoplasmic maturation.     

Wildlife detector dogs and camera traps: a comparison of techniques for detecting feral cats

A major challenge in controlling overabundant wildlife is monitoring their populations, particularly as they decline to very low density. Camera traps and wildlife detector dogs are increasingly being used for this purpose. We compared the cost-effectiveness of these two approaches for detecting feral cats (Felis catus) on two pastoral properties in Hawke's Bay, North Island, New Zealand. One property was subject to intensive pest removal, while the other had no recent history of pest control. Camera traps and wildlife detector dogs detected cats at similar rates at both sites. The operating costs of each method were also comparable. We identify a number of advantages and disadvantages of each technique, and suggest priorities for further research.     

LONG-TERM EFFECTS OF TEFLUTIXOL ON THE SYNTHESIS AND ENDOGENOUS LEVELS OF MOUSE BRAIN CATECHOLAMINES

—The long term effects on accumulation of ¹⁴C-labelled dopamine and noradrenaline after [¹⁴C]tyrosine administration and on the endogenous levels of catecholamines in mouse brain were studied after treatment with a new potent thioxanthene neuroleptic, teflutixol. The drug was given as a single dose (5 mg/kg i.p.), as repeated daily doses (1·25 mg/kg p.o.), or as a single dose of the palmitic ester in Viscoleo® (20 mg/kg s.c). After a single dose, teflutixol increased catecholamine synthesis (100%). Noradrenaline synthesis rapidly returned to normal, whereas decreased dopamine synthesis was seen from the third to sixth day, after which it was normal. When the receptors were continuously exposed to teflutixol, either by daily dosage or by the depot preparation, catecholamine synthesis was increased for the first few days but then returned to normal, indicating development of tolerance. Endogenous concentrations of catecholamines were only decreased during the first few days, when the increase in synthesis was greatest. The findings are in accordance with results obtained by Møller Nielsen & Christensen (1975), who found that receptor blockade was followed by receptor supersensitivity after treatment with a neuroleptic compound. The receptor blockade may activate a feedback mechanism that induces increased nervous firing with increased amine synthesis as a consequence. The resulting supersensitivity, if sufficiently great, may lead to reduced nervous firing, followed by slowing of dopamine synthesis.     

Effects of neuroleptics on 3H-haloperidol and 3H-cis(Z)-flupenthixol binding and on adenylate cyclase activity in vitro.

The subcellular localization of dopamine-sensitive adenylate cyclase was studied in rat brain striatum and compared to the distribution of dopamine binding sites. The highest specific activity of adenylate cyclase activities sensitive to dopamine was associated almost exclusively with synaptic membranes (mithchondrial fraction; P₂). Using [³H] haloperidol and [³H] apomorphine as markers for the dopamine receptor, specific binding was observed in both the mitochondrial (P₂) and microsomal (P₃) fractions. Data for the mitochondrial fraction revealed a heterogeneity of binding sites. Two saturable sites for [³H] haloperidol were observed with K_d values of 2.5nM and 12.5nM respectively. Overall, the localization of multiple binding sites in the crude synaptosomal fraction correlates well with the localization of dopamine-sensitive adenylate cyclase in this fraction.     

Corona radiata density as a non-invasive marker of bovine cumulus-corona-oocyte complexes selected for in vitro embryo production

The density of the corona radiata as a marker for the quality of cumulus-corona-oocyte complexes (CCOC's) for in vitro embryo production was tested. The CCOC's in which the corona radiata appeared as a dark rim surrounding the zona pellucida (Group 1) and CCOC's in which the corona had the same density as the rest of the cumulus investment (Group 2) were assessed with respect to nuclear ultrastructure, corona-cumulus expansion and capacity for sustaining embryonic development in vitro. An intermediate Group 3 with characteristics between Groups 1 and 2 was also assessed for in vitro development capacity. The CCOC's in Group 1 were typically meiotically unactivated and presented a nonundulating nuclear envelope. More than half of the CCOC's in Group 2 showed some degree of meiotic activation, and those that were nonactivated displayed "holes" in the nuclear envelope or dilatations of the perinuclear cisterna. The CCOC's in Group 2 were characterized by partial corona-cumulus expansion already at collection. The CCOC's from Groups 1 and 3 sustained embryonic development in vitro at a significantly higher rate than CCOC's from Group 2. It is concluded that CCOC's in which the corona radiata has the same density as the rest of the cumulus investment are less competent candidates for in vitro embryo production.     

H-Type Bovine Spongiform Encephalopathy: Complex Molecular Features and Similarities with Human Prion Diseases

We previously reported that some cattle affected by bovine spongiform encephalopathy (BSE) showed distinct molecular features of the protease-resistant prion protein (PrP^res) in Western blot, with a 1–2 kDa higher apparent molecular mass of the unglycosylated PrP^res associated with labelling by antibodies against the 86–107 region of the bovine PrP protein (H-type BSE). By Western blot analyses of PrP^res, we now showed that the essential features initially described in cattle were observed with a panel of different antibodies and were maintained after transmission of the disease in C57Bl/6 mice. In addition, antibodies against the C-terminal region of PrP revealed a second, more C-terminally cleaved, form of PrP^res (PrP^res #2), which, in unglycosylated form, migrated as a ≈ 14 kDa fragment. Furthermore, a PrP^res fragment of ≈7 kDa, which was not labelled by C-terminus-specific antibodies and was thus presumed to be a product of cleavage at both N- and C-terminal sides of PrP protein, was also detected. Both PrP^res #2 and ≈7 kDa PrP^res were detected in cattle and in C57Bl/6 infected mice. These complex molecular features are reminiscent of findings reported in human prion diseases. This raises questions regarding the respective origins and pathogenic mechanisms in prion diseases of animals and humans.Key Words: prion, BSE, Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, Western blot, amyloid     

Host origin of plastid solute transporters in the first photosynthetic eukaryotes

Background  

It is generally accepted that a single primary endosymbiosis in the Plantae (red, green (including land plants), and glaucophyte algae) common ancestor gave rise to the ancestral photosynthetic organelle (plastid). Plastid establishment necessitated many steps, including the transfer and activation of endosymbiont genes that were relocated to the nuclear genome of the 'host' followed by import of the encoded proteins into the organelle. These innovations are, however, highly complex and could not have driven the initial formation of the endosymbiosis. We postulate that the re-targeting of existing host solute transporters to the plastid fore-runner was critical for the early success of the primary endosymbiosis, allowing the host to harvest endosymbiont primary production.     

Sheep prions with molecular properties intermediate between classical scrapie,BSE and CH1641–scrapie

Efforts to differentiate bovine spongiform encephalopathy (BSE) from scrapie in prion infected sheep have resulted in effective methods to decide about the absence of BSE. In rare instances uncertainties remain due to assumptions that BSE, classical scrapie and CH1641–a rare scrapie variant–could occur as mixtures. In field samples including those from fallen stock, triplex Western blotting analyses of variations in the molecular properties of the proteinase K resistant part of the disease‑associated form of prion protein (PrP^res) represents a powerful tool for quick discrimination purposes. In this study we examined 7 deviant ovine field cases of scrapie for some typical molecular aspects of PrP^res found in CH1641‑scrapie, classical scrapie and BSE. One case was most close to scrapie with respect to molecular mass of its non-glycosylated fraction and N-terminally located 12B2‑epitope content. Two cases were unlike classical scrapie but too weak to differentiate between BSE or CH1641. The other 4 cases appeared intermediate between scrapie and CH1641 with a reduced molecular mass and 12B2‑epitope content, together with the characteristic presence of a second PrP^res population. The existence of these 2 PrP^res populations was further confirmed through deglycosylation by PNGaseF. The findings indicate that discriminatory diagnosis between classical scrapie, CH1641 and BSE can remain inconclusive with current biochemical methods. Whether such intermediate cases represent mixtures of TSE strains should be further investigated e.g. in bioassays with rodent lines that are varying in their susceptibility or other techniques suitable for strain typing.