Ultrastructural evaluation of oocytes during atresia in rat ovarian follicles

Mammalian females are born with a finite number of ovarian oocytes, the vast majority of which ultimately undergo degeneration by atresia. The overall process of ovarian follicular atresia has been morphologically well described only in large antral follicles. Additionally, little attention has been focused on ultrastructural changes in the oocyte. Furthermore, most such morphological studies were performed prior to identification of apoptosis as a mechanism of physiological cell death. Therefore, the purpose of this study was to use electron microscopy to compare the process of atretic oocyte degradation in ovarian follicles of female Fischer 344 rats (38 days old) with ultrastructural characteristics of apoptosis. Examination of ovarian follicles revealed that nucleolar segregation, cytoplasmic or nuclear condensation, apoptotic body formation, and chromatin margination along the nuclear membrane are never observed in atretic oocytes during the degenerative process. Instead, early morphological changes in atretic oocytes include retraction of granulosa cell- and oocyte-derived microvilli and condensation of mitochondria and loss of cristae. These occurrences coincide with initiation of granulosa cell apoptosis. After most granulosa cells are lost, more severe changes occur, including segmentation of the oocyte and cytoplasmic vacuolization as atresia progresses. Thus, these results suggest that, during atresia, oocytes are removed by physiological oocyte cell death, a method that does not involve classically described apoptosis.     

Characterization of the antigenic domains of the major core protein (p26) of equine infectious anemia virus.

A panel of recombinant trpLE-gag fusion proteins and synthetic peptides was used in Western immunoblot and enzyme-linked immunosorbent assays to identify segments of the major core protein (p26) of equine infectious anemia virus that are antigenic in horses during experimental and natural infections with the virus. The predominant humoral immune response was directed toward a highly immunogenic domain composed of 83 amino acids from the carboxy terminus of p26. The observed immunogenicity of p26 resembled that reported for p24 of human immunodeficiency virus type 1, suggesting the conservation of structural motifs in the lentiviral core proteins which are responsible for their observed immunogenicity during persistent lentivirus infections.     

A single ancient origin of brood parasitism in African finches: implications for host-parasite coevolution

Robust phylogenies for brood-parasitic birds, their hosts, and nearest nesting relatives provide the framework to address historical questions about host-parasite coevolution and the origins of parasitic behavior. We tested phylogenetic hypotheses for the two genera of African brood-parasitic finches, Anomalospiza and Vidua, using mitochondrial DNA sequence data from 43 passeriform species. Our analyses strongly support a sister relationship between Vidua and Anomalospiza, leading to the conclusion that obligate brood parasitism evolved only once in African finches rather than twice, as has been the conventional view. In addition, the parasitic finches (Viduidae) are not recently derived from either weavers (Ploceidae) or grassfinches (Estrildidae), but represent a third distinct lineage. Among these three groups, the parasitic finches and estrildids, which includes the hosts of all 19 Vidua species, are sister taxa in all analyses of our full dataset. Many characters shared by Vidua and estrildids, including elaborate mouth markings in nestlings, unusual begging behavior, and immaculate white eggs, can therefore be attributed to common ancestry rather than convergent evolution. The host-specificity of mouth mimicry in Vidua species, however, is clearly the product of subsequent host-parasite coevolution. The lineage leading to Anomalospiza switched to parasitizing more distantly related Old World warblers (Sylviidae) and subsequently lost these characteristics. Substantial sequence divergence between Vidua and Anomalospiza indicates that the origin of parasitic behavior in this clade is ancient (approximately 20 million years ago), a striking contrast to the recent radiation of extant Vidua. We suggest that the parasitic finch lineage has experienced repeated cycles of host colonization, speciation, and extinction through their long history as brood parasites and that extant Vidua species represent only the latest iterations of this process. This dynamic process may account for a significantly faster rate of DNA sequence evolution in parasitic finches as compared to estrildids and other passerines. Our study reduces by one the tally of avian lineages in which obligate brood parasitism has evolved and suggests an origin of parasitism that involved relatively closely related species likely to accept and provide appropriate care to parasitic young. Given the ancient origin of parasitism in African finches, ancestral estrildids must have been parasitized well before the diversification of extant Vidua, suggesting a long history of coevolution between these lineages preceding more recent interactions between specific hosts and parasites.     

Identification, Purification, and Characterization of Iminodiacetate Oxidase from the EDTA-Degrading Bacterium BNC1

Microbial degradation of synthetic chelating agents, such as EDTA and nitrilotriacetate (NTA), may help immobilizing radionuclides and heavy metals in the environment. The EDTA- and NTA-degrading bacterium BNC1 uses EDTA monooxygenase to oxidize NTA to iminodiacetate (IDA) and EDTA to ethylenediaminediacetate (EDDA). IDA- and EDDA-degrading enzymes have not been purified and characterized to date. In this report, an IDA oxidase was purified to apparent homogeneity from strain BNC1 by using a combination of eight purification steps. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single protein band of 40 kDa, and by using size exclusion chromatography, we estimated the native enzyme to be a homodimer. Flavin adenine dinucleotide was determined as its prosthetic group. The purified enzyme oxidized IDA to glycine and glyoxylate with the consumption of O₂. The temperature and pH optima for IDA oxidation were 35°C and 8, respectively. The apparent K_m for IDA was 4.0 mM with a k_cat of 5.3 s⁻¹. When the N-terminal amino acid sequence was determined, it matched exactly with that encoded by a previously sequenced hypothetical oxidase gene of BNC1. The gene was expressed in Escherichia coli, and the gene product as a C-terminal fusion with a His tag was purified by a one-step nickel affinity chromatography. The purified fusion protein had essentially the same enzymatic activity and properties as the native IDA oxidase. IDA oxidase also oxidized EDDA to ethylenediamine and glyoxylate. Thus, IDA oxidase is likely the second enzyme in both NTA and EDTA degradation pathways in strain BNC1.     

CSF distribution of morphine, methadone and sucrose after intrathecal injection

The lumbar to cisternal CSF distribution of morphine and methadone were compared to C-14 sucrose, a standard marker of CSF bulk flow, after lumbar subarachnoid injections in a sheep preparation. Morphine appeared and peaked simultaneously with C-14 sucrose in cisternal CSF at 90 to 190 minutes. The mean peak cisternal CSF morphine concentrations were sustained for 30-40 minutes, and averaged 148 ng/ml, representing 0.3% of the administered dose. Methadone was not detectable in cisternal CSF up to 240-300 minutes after lumbar subarachnoid administration. The C-14 sucrose/morphine ratio was increased an average of 6.7 times in cisternal CSF as compared to the ratio of the two compounds injected into the lumbar subarachnoid space. These studies demonstrate that morphine, a hydrophilic opioid, given intrathecally moves rostrally and appears in cisternal CSF by bulk flow. Furthermore the rostral redistribution of morphine is associated with the clearance of morphine from CSF. Methadone, a lipophilic opioid, appears to be completely cleared from CSF before it reaches the cisterna magna. These pharmacokinetic studies support a contribution of supraspinal sites to the analgesic and adverse effects produced by morphine given by spinal routes of administration. In contrast methadone appears to exert its effects predominantly at spinal sites.     

Global climate drives southern right whale (Eubalaena australis) population dynamics

Sea surface temperature (SST) time-series from the southwest Atlantic and the El Ni?o 4 region in the western Pacific were compared to an index of annual calving success of the southern right whale (Eubalaena australis) breeding in Argentina. There was a strong relationship between right whale calving output and SST anomalies at South Georgia in the autumn of the previous year and also with mean El Ni?o 4 SST anomalies delayed by 6 years. These results extend similar observations from other krill predators and show clear linkages between global climate signals and the biological processes affecting whale population dynamics.     

The role of transmembrane AMPA receptor regulatory proteins (TARPs) in neurotransmission and receptor trafficking (Review)

AMPA receptors (AMPAR) mediate the majority of fast excitatory neurotransmission in the central nervous system (CNS). Transmembrane AMPAR regulatory proteins (TARPs) have been identified as a novel family of proteins which act as auxiliary subunits of AMPARs to modulate AMPAR trafficking and function. The trafficking of AMPARs to regulate the number of receptors at the synapse plays a key role in various forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). Expression of the prototypical TARP, stargazin/TARPγ2, is ablated in the stargazer mutant mouse, an animal model of absence epilepsy and cerebellar ataxia. Studies on the stargazer mutant mouse have revealed that failure to express TARPγ2 has widespread effects on the balance of expression of both excitatory (AMPAR) and inhibitory receptors (GABA_A receptors, GABAR). The understanding of TARP function has implications for the future development of AMPAR potentiators, which have been shown to have therapeutic potential in both psychological and neurological disorders such as schizophrenia, depression and Parkinson's disease.