BACKGROUND
Chromatin configuration of the germinal vesicle (GV) and quality of the cytoplasm are critical factors in achieving oocyte meiotic and developmental capacity during folliculogenesis. ...Besides gaining new insights into the timing and cellular mechanisms associated with the acquisition and regulation of GV oocyte competence, the domestic cat model was used to examine (i) the relation between GV chromatin configuration and oocyte functionality during folliculogenesis and (ii) the role of the cytoplasmic environment on the GV competence and stability.
METHODS
Structural and functional properties of GV oocytes were characterized after isolation from different follicle stages of non-stimulated cat ovaries. GV transfers, artificial chromatin compaction and oocyte vitrification were used to demonstrate the respective roles of GV and cytoplasm on the oocyte functionality.
RESULTS
GVs acquired the intrinsic capability to resume meiosis during the pre-antral follicle stage, whereas the capacity to support embryo development occurred while the antrum started to form. Chromatin configuration of the GV did not undergo extensive modification during the acquisition of competence or during the arrest of transcriptional activity at the large antral follicle stage. However, the quality and quantity of the cytoplasm regulated and enhanced GV functionality. This finding also held for GVs transferred from incompetent or subpar oocytes into the cytoplasm of good quality oocytes or when chromatin was artificially modified or vitrified.
CONCLUSIONS
The cat model provides a new insight into GV oocyte structure and function during folliculogenesis while challenging current concepts about oocyte quality criteria based on the GV morphology. This suggests alternative evaluative approaches for oocytes from other species too, including humans. Cat GVs also appear competent at an early follicle stage and are resilient to perturbations which designate this organelle as an attractive target for developing novel fertility preservation tactics.
A major challenge to retaining viability of frozen gametes and reproductive tissues is to understand and overcome species-specificities, especially because there is substantial diversity in ...cryobiological properties and requirements among cell types and tissues. Systematic studies can lead to successful post-thaw recovery, especially after determining: 1) membrane permeability to water and cryoprotectant, 2) cryoprotectant toxicity, 3) tolerance to osmotic changes, and 4) resistance to cooling and freezing temperatures. Although species-dependency ultimately dictates the ability of specific cells and tissues to survive freeze-thawing, there are commonalities between taxa that allow a protocol developed for one species to be useful information for another. This is the reason for performing comparative cryopreservation studies among diverse species. Our laboratory has compared cellular cryotolerance, especially in spermatozoa, in a diverse group of animals—from corals to elephants—for more than 30 yrs. Characterizing the biophysical traits of gametes and tissues is the most efficient way to develop successful storage and recovery protocols, but, such data are only available for a few laboratory, livestock, and fish species, with virtually all others (wild mammals, birds, reptiles, and amphibians) having gone unstudied. Nonetheless, when a rare animal unexpectedly dies, there is no time to understand the fundamentals of biophysics. In these emergencies, it is necessary to rely on experience and the best data from taxonomically-related species. Fortunately, there are some general similarities among most species, which, for example, allow adequate post-thaw viability. Regardless, there is a priority for more information on biophysical traits and freezing tolerance of distinctive biomaterials, especially for oocytes and gonadal tissues, and even for common, domesticated animals. Our colleague, Dr John Critser was a pioneer in cryobiology, earning that moniker because of his advocacy and devotion to understanding the differences (and similarities) among species to better store living genetic material.
Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up a significant fraction of urban volatile organic compound (VOC) emissions that ...contribute to the formation of secondary organic aerosol (SOA). Benzene is one of the most abundant species emitted from vehicles, biomass burning and industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed at the Jülich Plant Atmosphere Chamber as part of a series of experiments examining benzene oxidation by OH under high- and low-NOx conditions, where a range of organic oxidation products were detected. The nitrate scheme detects many oxidation products with high masses, ranging from intermediate volatile organic compounds (IVOCs) to extremely low volatile organic compounds (ELVOCs), including C12 dimers. In comparison, very few species with C≥6 and O≥8 were detected with the iodide scheme, which detected many more IVOCs and semi-volatile organic compounds (SVOCs) but very few ELVOCs and low volatile organic compounds (LVOCs). A total of 132 and 195 CHO and CHON oxidation products are detected by the iodide ToF-CIMS in the low- and high-NOx experiments respectively. Ring-breaking products make up the dominant fraction of detected signal and 21 and 26 of the products listed in the Master Chemical Mechanism (MCM) were detected. The time series of highly oxidised (O≥6) and ring-retaining oxidation products (C6 and double-bond equivalent = 4) equilibrate quickly, characterised by a square form profile, compared to MCM and ring-breaking products which increase throughout oxidation, exhibiting sawtooth profiles. Under low-NOx conditions, all CHO formulae attributed to radical termination reactions of first-generation benzene products, and first-generation auto-oxidation products are observed. Several N-containing species that are either first-generation benzene products or first-generation auto-oxidation products are also observed under high-NOx conditions. Hierarchical cluster analysis finds four clusters, of which two describe photo-oxidation. Cluster 2 shows a negative dependency on the NO2/NOx ratio, indicating it is sensitive to NO concentration and thus likely to contain NO addition products and alkoxy-derived termination products. This cluster has the highest average carbon oxidation state (OSC‾) and the lowest average carbon number. Where nitrogen is present in a cluster member of cluster 2, the oxygen number is even, as expected for alkoxy-derived products. In contrast, cluster 1 shows no dependency on the NO2/NOx ratio and so is likely to contain more NO2 addition and peroxy-derived termination products. This cluster contains fewer fragmented species, as the average carbon number is higher and OSC‾ lower than cluster 2, and more species with an odd number of oxygen atoms. This suggests that clustering of time series which have features pertaining to distinct chemical regimes, for example, NO2/NOx perturbations, coupled with a priori knowledge, can provide insight into identification of potential functionality.
One of the most significant challenges in the recovery of threatened species is the ability to maintain genetic diversity, avoid inbreeding and sustain population health and reproduction. Assisted ...reproductive techniques, including artificial insemination (AI), have been touted for decades as approaches that could contribute to the demographic and genetic management of rare species. Here, we report the first successful integration of AI with frozen semen into a formal recovery program and the positive impact on genetic diversity for the critically endangered black‐footed ferret Mustela nigripes. Techniques developed in the taxonomically related domestic ferret Mustela putorius furo and Siberian polecat Mustela eversmannii were applied over time to selected black‐footed ferrets, including semen banking from six of the last 18 survivors. After evaluation, processing and storage in liquid nitrogen (−196°C/−321°F), for as long as 20 years, sperm samples were thawed and transabdominally inseminated into the uterine horns of female conspecifics. Eight black‐footed ferret offspring were produced using thawed sperm samples (including after two decades of cryopreservation) with inseminates containing as few as 3.4 × 10⁶ motile spermatozoa. The incorporation of these offspring and/or their descendants into the ex situ breeding program prevented heterozygosity loss in the population and actually enhanced gene diversity (GD) significantly by 0.2% and lowered measures of inbreeding by 5.8%. This study demonstrates the utility and genetic diversity benefits of applying AI with cryopreserved spermatozoa 20 generations removed from the contemporary population for a wild animal revival program.
The present study examined the influences of the physical and hormonal microenvironment on in vitro growth and steroidogenesis of dog follicles. Follicles were enzymatically isolated and individually ...encapsulated in 0.5% (w/v; n=17) or 1.5% (n=10) alginate and cultured with 0.5 IU/ml equine chorionic gonadotropin for 192 h. In a separate experiment, follicles were encapsulated in 0.5% alginate and cultured with 0 (n=22), 1 (n=23), 10 (n=20) or 100 (n=21) μg/ml FSH for 240 h. Follicle diameter and steroid production were assessed every 48 h in both studies. Follicles encapsulated in the 0.5% alginate grew faster (P<0.05) than those cultured in the 1.5% concentration. Oestradiol (E₂) and progesterone (P₄) increased consistently (P<0.05) over time, and follicles in the 1.5% alginate produced more (P<0.05) P₄ than those in the 0.5% solution. Follicles cultured in the highest FSH concentration (100 μg/ml) increased 100% in size after 240 h compared with 50 to 70% in lower dosages. E₂ concentration remained unchanged over time (P>0.05) across FSH dosages. However, P₄ increased (P<0.05) as culture progressed and with increasing FSH concentration. Results demonstrate that dog follicles cultured in alginate retain structural integrity, grow in size and are hormonally active. Lower alginate and increasing FSH concentrations promote in vitro follicle growth. However, the absence of an E₂ rise in follicles cultured in FSH alone suggests the need for LH supplementation to support theca cell differentiation and granulosa cell function.
The oocyte of the domestic dog is unique from that of other mammalian species studied to date. Ovulation occurs either once or twice per year, with the oocyte released at the germinal vesicle stage, ...and then completing nuclear and cytoplasmic maturation within the oviduct under the influence of rising circulating progesterone.
In vivo meiotic maturation of the bitch oocyte is completed within 48–72
h after ovulation, which is longer than 12–36
h required for oocytes from most other mammalian species. Due to these inherently novel traits,
in vitro culture systems developed for maturing oocytes of other species have been found inadequate for maturation of dog oocytes. On average, only 15–20% of ovarian oocytes achieve the metaphase II stage after 48–72
h of
in vitro culture. Thus far, no offspring have been produced in the dog (or other canids) by transferring embryos derived from
in vitro matured oocytes. This review addresses current knowledge about dog reproductive physiology, specifically those factors influencing
in vitro developmental competence of the oocyte. This summary lays a foundation for identifying the next steps to understanding the mechanisms regulating meiotic maturation and developmental competence of the dog oocyte.
Parents of infants treated with beta-blockers for infantile haemangioma are often concerned about the long-term aesthetic outcome. This cross-sectional study assessed the influence on the long-term ...aesthetic outcome of characteristics of the infantile haemangioma, the beta-blocker treatment, and the infant. The study included 103 children aged 6–12 years, treated with beta-blockers (propranolol or atenolol) for infantile haemangioma during infancy (age at treatment initiation ≤1 year) for ≥6 months. Dermatologists and parents scored the Patient Observer Scar Assessment Scale, and the child scored a visual analogue scale. Dermatologists identified whether telangiectasia, fibrofatty tissue, and atrophic scar tissue were present. The long-term aesthetic outcome of infantile haemangioma was judged more negatively by dermatologists and parents in case of a superficial component, ulceration, older age at treatment initiation, higher cumulative dose, and/or shorter follow-up time. According to children, infantile haemangioma located on the head had better aesthetic outcome than infantile haemangioma located elsewhere. Close monitoring, particularly of infantile haemangioma with a superficial component, is essential for early initiation of treatment, and to prevent or treat ulceration. These outcome data can support parental counselling and guide treatment strategy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Contents
The culture of ovarian follicles is an important tool for understanding the mechanisms controlling follicle development and differentiation of the oocyte. The benefit of recovering ...meiotically and developmentally competent oocytes from early stage follicles (primordial, primary, pre‐antral and early antral) also would be significant, ranging from rescue of genomes from endangered species to preserving fertility in women facing cancer treatments. This research field is at an early stage of scientific discovery. To‐date, live offspring from cultured primordial follicles that produced fertilizable oocytes has occurred only in the mouse. Progress in other more complex species has been limited because larger animals have longer durations of natural folliculogenesis, thereby requiring more culture time to generate fully grown follicles and oocytes. We believe the dog and cat are excellent models for understanding more about folliculogenesis in vitro. This review highlights what is known about this topic for these two species as well as future priorities. We have discovered that it is more challenging to maintain viability of primordial follicles within ovarian tissues in vitro in the dog than the cat. Nonetheless, it is possible to grow both isolated cat and dog pre‐antral follicles in culture. Although the follicles of both species have the capacity to increase in size and produce steroids, only cat oocytes appear morphologically normal. The reason for this striking difference between these two species is an area of high research priority. While much more fundamental data are required, we envision advanced technology that will allow harvesting oocytes from the vast, unused follicle stores sequestered within carnivore ovaries. These gametes have utility for reproducing genetically valuable dogs and cats that are ‘companions’ or biomedical models for investigating human disorders as well as for salvaging the genomes of rare canid and felid species that die before contributing to genetic management programs.
Contents
Matrix metalloproteinase (MMP) has been implicated as having roles in ovarian folliculogenesis. Here, we determined the expression pattern of six MMPs (MMP1, MMP2, MMP3, MMP7, MMP9 and ...MMP13) and their endogenous tissue inhibitor, TIMP1, during cat follicle growth. Different developmental stage follicles were mechanically isolated and gene expression analysed by real‐time qPCR while MMP1, 2, 9 and 13 localization was determined by immunohistochemistry. With the exception of MMP13, the amount of MMP mRNA was lowest in primordial follicles and increased thereafter. Peak levels were detected in early antral follicles for MMP1 (72.2‐fold increase above primordial follicle amount), MMP2 (10‐fold), MMP3 (57‐fold) and MMP9 (2.8‐fold). MMP7 transcripts increased 2‐fold by the primary follicle stage and then plateaued. MMP13 mRNA peaked in primary follicles (2.5‐fold) and was lower in more advanced counterparts. TIMP1 sharply increased (6‐fold) in secondary follicles and gradually declined in the later stages. MMP1 and MMP9 expression were expressed in the granulosa cells of all follicle stages. MMP2 was immunoreactive in early and antral follicles, especially at granulosa cells adjacent to the antral cavity. By contrast, the MMP13 was weakly detected in primary follicles onward. In summary, there are distinctive and consistent changes in MMPs and TIMP1 expression during follicle development, suggesting that these enzymes play one or more roles in cat folliculogenesis. In particular, high mRNA and protein expression levels of MMP1 and MMP2, especially at the antral stage, indicate that these enzymes likely are involved in antrum formation and expansion.
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