Effects of transforming growth factors and activin-A on in vitro porcine oocyte maturation

Growth factors are known to regulate ovarian function. In the present study, effects of these growth factors, TGF-α, TGF-β, and activin-A were tested on spontaneous porcine oocyte maturation. Cumulus-oocyte complexes (COC) were cultured in the presence of TGF-α, TGF-β, and activin-A for 48 hr. Stages of meiotic maturation were assessed by staining with acetic orcein. Among these factors, only TGF-α significantly enhanced the maturation rate, whereas TGF-β suppressed the spontaneous maturation rate. The site of action of TGF-α on COC and the interaction between TGF-α and EGF receptor was also examined. Denuded oocytes, alone or in coculture with cumulus cells, were cultured in the presence of TGF-α for 48 hr. TGF-α did not have any significant effect on denuded oocyte maturation. Heptanol was employed to investigate the role of gap junctions on TGF-α-induced oocyte maturation in COC. Although heptanol did not have any significant effect in the control medium, heptanol reversed the stimulatory effect of TGF-α on porcine oocyte maturation. TGF-α was able to displace ¹²⁵I-EGF binding on COC. In conclusion, TGF-α enhances the spontaneous maturation of porcine oocytes by generating positive signal(s) in cumulus cells that are transferred to the oocyte via gap junctions. TGF-α shares the same receptor with EGF on porcine COC. TGF-β, in contrast, inhibits porcine oocyte maturation. © 1994 Wiley-Liss, Inc.     

Effect of circumferential heterogeneity of wood maturation strain, modulus of elasticity and radial growth on the regulation of stem orientation in trees

Active mechanisms of re-orientation are necessary to maintain the verticality of tree stems. They are achieved through the production of reaction wood, associated with circumferential variations of three factors related to cambial activity: maturation strain, longitudinal modulus of elasticity (MOE) and eccentric growth. These factors were measured on 17 mature trees from different botanical families and geographical locations. Various patterns of circumferential variation of these factors were identified. A biomechanical analysis based on beam theory was performed to quantify the individual impact of each factor. The main factor of re-orientation is the circumferential variation of maturation strains. However, this factor alone explains only 57% of the re-orientations. Other factors also have an effect through their interaction with maturation strains. Eccentric growth is generally associated with heterogeneity of maturation strains, and has an important complementary role, by increasing the width of wood with high maturation strain. Without this factor, the efficiency of re-orientations would be reduced by 31% for angiosperms and 26% for gymnosperms. In the case of angiosperms, MOE is often larger in tension wood than in normal wood. Without these variations, the efficiency of re-orientations would be reduced by 13%. In the case of gymnosperm trees, MOE of compression wood is lower than that of normal wood, so that re-orientation efficiency would be increased by 24% without this factor of variations.     

Effect of follicular fluid collected from various diameter follicles on the progression of nuclear maturation and developmental competence of pig oocytes

Supplementing in vitro maturation medium with porcine follicular fluid (FF) improves maturation rate, male pronucleus formation, and monospermic fertilization of pig oocytes. This study examined, (1) if there are differences in FF derived from large follicles (LF, 5–6 mm in diameter) and small follicles (SF, 3–4 mm in diameter) on the effect of supplementing the maturation medium with FF on the progression of nuclear maturation, fertilization rate, and developmental competence of porcine oocytes; (2) whether the FF source influences the effect of the FF on the maturation medium on the survival rate and proliferation rate of cumulus cells (CCs) and the expansion of cumulus-oocyte-complexes (COCs); (3) whether the oocyte source (oocytes collected from LFs or SFs) influences the effect of FF on the progression of the nuclear maturation of oocytes; (4) whether the factors in the FF that affect the kinetics of nuclear maturation are proteins, and the range of the molecular weight of the FF factors.

In experiment 1, adding FF from LFs (LFF) significantly accelerated nuclear maturation and improved the fertilization rate; the developmental ratio was comparable with those of adding FF from SFs (SFF). In experiment 2, adding LFF, but not SFF, improved the CC survival rate, although the FF source did not affect the proliferation rate. Expansion of COCs was greater with SFF than LFF. In experiment 3, LFF promoted nuclear maturation of oocytes collected from only LFs. There was a significant interaction between the FF source and the oocyte source in the effect on nuclear maturation stages at 36 h of maturation. In experiment 4, treatment of FF with heat or trypsin diminished the difference between the effect of LFF and SFF on the progression of nuclear maturation. In addition, the predominant effect of LFF compared to that of SFF on nuclear maturation was not affected by ultrafiltration of the FF with a 30-kDa filter, but was diminished by ultrafiltration with a 100-kDa filter. The present study suggests that some proteins present in LFF that range in molecular weight from 30 to 100 kDa improve the developmental competence of oocytes probably via progression of nuclear maturation and cumulus cells viability.     

Application of the model system of hormonal stimulation of the sturgeon oocyte maturation and ovulation in vitro for solving some fundamental and applied problems

The author summarizes the results of many-year application of the model of in vitro sturgeon oocyte maturation for different purposes, such as comparison of gonadotropic activities of different preparations, selection of females for breeding, and studying the effects of different factors in order to improve the breeding technology. Special attention is paid to factors that can affect the results of experiments on hormonal stimulation of in vitro oocyte maturation and ovulation and their interpretation. Two other phenomena are discussed: the inhibitory effect of gonadotropic pituitary hormones on the progesterone-induced in vitro oocyte maturation and the non-hormonal induction of oocyte maturation, further studies of which can elucidate the mechanisms underlying the hormonal regulation of oogenesis in sturgeons.     

Requirements for Cu(A) and Cu-S center assembly of nitrous oxide reductase deduced from complete periplasmic enzyme maturation in the nondenitrifier Pseudomonas putida

Bacterial nitrous oxide (N(2)O) reductase is the terminal oxidoreductase of a respiratory process that generates dinitrogen from N(2)O. To attain its functional state, the enzyme is subjected to a maturation process which involves the protein-driven synthesis of a unique copper-sulfur cluster and metallation of the binuclear Cu(A) site in the periplasm. There are seven putative maturation factors, encoded by nosA, nosD, nosF, nosY, nosL, nosX, and sco. We wanted to determine the indispensable proteins by expressing nos genes from Pseudomonas stutzeri in the nondenitrifying organism Pseudomonas putida. An in silico study of denitrifying bacteria revealed that nosL, nosX (or a homologous gene, apbE), and sco, but not nosA, coexist consistently with the N(2)O reductase structural gene and other maturation genes. Nevertheless, we found that expression of only three maturation factors (periplasmic protein NosD, cytoplasmic NosF ATPase, and the six-helix integral membrane protein NosY) together with nosRZ in trans was sufficient to produce catalytically active holo-N(2)O reductase in the nondenitrifying background. We suggest that these obligatory factors are required for Cu-S center assembly. Using a mutational approach with P. stutzeri, we also studied NosA, the Cu-containing outer membrane protein previously thought to have Cu insertase function, and ScoP, a putative membrane-anchored chaperone for Cu(A) metallation. Both of these were found to be dispensable elements for N(2)O reductase biosynthesis. Our experimental and in silico data were integrated in a model of N(2)O reductase maturation.     

A review of the current (1992) state of our knowledge concerning reproduction in open thelycum Penaeid shrimp with emphasis on Penaeus vannamei

Summary

The current state of knowledge relating to the reproduction of the commercially important open thelycum shrimps (Crustacea: Penaeidae) is reviewed with particular reference to Penaeus vannamei. Industry standard procedures for the breeding of shrimps in captivity are reviewed against a background of knowledge concerning the maturation processes in males and females. The factors controlling maturation are not completely understood, and it is not clear whether maturation of females is size-or age-dependent. Although unilateral eyestalk ablation is routinely used to induce maturation, the physiological mechanism of this operation is not properly understood. Further research on environmental conditions for successful maturation is required. Nutrition is an important component in successful artificial breeding programs that still rely on the provision of natural foods (squid and polychaeta). The processes of oocyte formation, mating, spawning and hatching are discussed in relation to observations made at the Gulf Coast Research Laboratory.     

Assembly and nuclear export of pre-ribosomal particles in budding yeast

The ribosome is responsible for the final step of decoding genetic information into proteins. Therefore, correct assembly of ribosomes is a fundamental task for all living cells. In eukaryotes, the construction of the ribosome which begins in the nucleolus requires coordinated efforts of >350 specialized factors that associate with pre-ribosomal particles at distinct stages to perform specific assembly steps. On their way through the nucleus, diverse energy-consuming enzymes are thought to release assembly factors from maturing pre-ribosomal particles after accomplishing their task(s). Subsequently, recruitment of export factors prepares pre-ribosomal particles for transport through nuclear pore complexes. Pre-ribosomes are exported into the cytoplasm in a functionally inactive state, where they undergo final maturation before initiating translation. Accumulating evidence indicates a tight coupling between nuclear export, cytoplasmic maturation, and final proofreading of the ribosome. In this review, we summarize our current understanding of nuclear export of pre-ribosomal subunits and cytoplasmic maturation steps that render pre-ribosomal subunits translation-competent.     

Participation of the cyclase system in the molecular mechanisms of differentiation control of immunocompetent cells

The effects of polypeptide thymic and bone marrow factors on the cyclase system of rat thymus and spleen lymphocytes were studied. It was shown that the induction of maturation of rat T-lymphocyte precursors into immunocompetent T-cells under effects of the thymic factor is accompanied by the activation of the adenylate cyclase system and the elevation of the cAMP/cGMP ratio. The observed increase in the cGMP level in splenic lymphocytes suggests the presence of cAMP- and cGMP-dependent steps of in the reaction of T-lymphocyte maturation. The bone marrow factor causes an elevation of the cAMP level only in splenic lymphocytes, which points to differences in the lymphocyte subpopulations that are sensitive to thymus and bone marrow factors. Impairments in T-lymphocyte maturation in patients with immunodeficiencies are concomitant with shifts in the isoenzyme spectrum of lactate dehydrogenase in peripheral blood lymphocytes as well as with changes in the sensitivity of the cAMP system to the thymic factor and isoproterenol. These disturbances are relieved by administration of the thymic factor. The roles of the cyclase system and polypeptide thymic and bone marrow factors in the molecular mechanisms of immunocompetent cell maturation are discussed.     

The importance of social dimension and maturation stage for the probabilistic maturation reaction norm in Poecilia reticulata

Maturation is an important event in an organism's life history, with important implications on dynamics of both wild and captive populations. The probabilistic maturation reaction norm (PMRN) has emerged as an important method to describe variation in maturation in wild fish. Because most PMRNs are based on age and size only, it is important to understand limitations of these variables in explaining maturation. We experimentally assessed (i) the sensitivity of age‐ and size‐based PMRNs to unaccounted sources of plasticity, (ii) the role of social environment on maturation and (iii) the significance of estimating PMRNs early and late in the maturation process (initiation and completion of maturation, respectively). We reared male guppies (Poecilia reticulata) under laboratory conditions, subjected to two food levels and three different social cues. We found that growth and social environment affected the maturation in a way that could not be accounted for by their effect on age and size. PMRNs estimated for the initiation stage were less plastic (growth differences and social cues influenced the PMRN shape only little) than those for completion. The initiation of maturation is probably closer to the maturation ‘decision’ and allows determining factors influencing maturation decision most accurately.     

Growth factors--the new regulators of reproduction

Experimental data on the role of growth factors in the processes of oocyte maturation and of proliferation and differentiation in the mammalian ovaries are reviewed. Evidence is provided that theca and granulosa cells can synthesize epidermal, fibroblast, insulin-like and transforming growth factors and have receptors to all of them. The regulation of oocyte maturation induction by the growth factors is analysed. A possible physiological influence of growth factors and inhibin on regulation of folliculogenesis and gametogenesis and also on selection of the dominant follicle in the mammalian ovaries is discussed.     

Structural,energetic, and functional analysis of a protein-protein interface at distinct stages of affinity maturation

Due to a paucity of studies that synthesize structural, energetic, and functional analyses of a series of protein complexes representing distinct stages in an affinity maturation pathway, the biophysical basis for the molecular evolution of protein-protein interactions is poorly understood. Here, we combine crystal structures and binding-free energies of a series of variant superantigen (SAG)-major histocompatibility complex (MHC) class II complexes exhibiting increasingly higher affinity to reveal that this affinity maturation pathway is controlled largely by two biophysical factors: shape complementarity and buried hydrophobic surface. These factors, however, do not contribute equivalently to the affinity maturation of the interface, as the former dominates the early steps of the maturation process while the latter is responsible for improved binding in later steps. Functional assays reveal how affinity maturation of the SAG-MHC interface corresponds to T cell activation by SAGs.     

No single way to explain cytoplasmic maturation of oocytes from prepubertal and cyclic gilts

The objective of this study was to evaluate selected aspects of cytoplasmic maturation in oocytes from prepubertal and cyclic crossbred gilts before and after in vitro maturation. For this purpose, cortical granule redistribution, mitochondrial DNA content and mitochondria translocation were analyzed. Moreover, for the first time the fatty acid profiles in follicular fluid (FF) of both gilt categories was evaluated. The nuclear maturation (the percentage of metaphase II oocytes was 83% in prepubertal gilts compared with 87% in cyclic gilts), cortical granule relocation from the cortex to peripheral ooplasm (98.7% vs. 98.8% of oocytes, respectively) and mitochondrial DNA content (227 543 vs. 206 660, respectively) was not affected by sexual maturity of the donor gilt. However, the redistribution of active mitochondria during in vitro maturation was observed only in the oocytes of cyclic gilts. With regard to FF analysis, saturated, unsaturated, and monounsaturated fatty acids were significantly more abundant in the FF of prepubertal females. In particular, stearic (C18:0) and palmitic (C16:0) fatty acids had significantly higher concentrations in the FF of prepubertal gilts. In conclusion, although the oocytes of prepubertal gilts matured in vitro at a rate similar to those of cyclic gilts, they differed with respect to the selected factors attributed to cytoplasmic maturation. We suggest that the higher content of particular fatty acids, which is known to have a negative influence on oocyte maturation, as well as impaired mitochondria redistribution are factors limiting the maturation potential of oocytes from prepubertal gilts.     

Effects of recombinant multi-CSF, GM-CSF, G-CSF and M-CSF on the proliferation and maturation of human AML in vitro

To investigate the relative role of the individual hematopoietic growth factors in stimulating AML cell growth we compared the effects of recombinant (r) Multi-CSF (IL-3), rGM-CSF, rG-CSF and rM-CSF on DNA synthesis of AML blasts in culture. In order to establish the interrelationship between the proliferative effects exerted by these CSFs on AML cells, the ability of these factors to induce progressive monocytic or granulocytic maturation in AML blasts was also assessed. The studies were conducted in 25 cases of AML. They show that AML blasts often are responsive to at least one of the physiologic regulators but the patterns of response reveal a considerable heterogeneity among patients with AML. Although the cells react to these factors, they are usually inert in their capacity to mature, which indicates their intrinsic maturation defect.     

Cytoplasmic factors that control nuclear behavior in mammalian oocytes: a re-evaluation of studies performed as a student of Yoshio Masui

Studies performed by the author in the laboratory of Dr Yoshio Masui are reviewed and interpreted in the light of subsequent findings. The first series of studies indicated that that chromosome condensation during meiotic maturation of mouse oocytes is controlled initially by a stable protein that decays during maturation and subsequently by an unstable protein synthesized after germinal vesicle breakdown. Cyclin B is present in immature oocytes, becomes partially degraded near metaphase I and then re-accumulates, suggesting that this may be protein whose activity was inferred from the original results. The second series of experiments indicated that factors which appear in the oocyte cytoplasm during maturation are able to remodel the sperm into metaphase-like chromosomes, and that the supply of these factors is limited. Recent work indicates that these factors are required for the assembly of histones onto the sperm DNA, and has identified two molecular species, mNAP-1 and NPM-3, known to promote replication-independent chromatin assembly in somatic cells, that are expressed in oocytes.     

Application of the Model System of Hormonal Stimulation of the Sturgeon Oocyte Maturation and Ovulation in vitro for Solving Some Fundamental and Applied Problems

The author summarizes the results of many-year application of the model of in vitro sturgeon oocyte maturation for different purposes, such as comparison of gonadotropic activities of different preparations, selection of females for breeding, and studying the effects of different factors in order to improve the breeding technology. Special attention is paid to factors that can affect the results of experiments on hormonal stimulation of in vitro oocyte maturation and ovulation and their interpretation. Two other phenomena are discussed: the inhibitory effect of gonadotropic pituitary hormones on the progesterone-induced in vitro oocyte maturation and the nonhormonal induction of oocyte maturation, further studies of which can elucidate the mechanisms underlying the hormonal regulation of oogenesis in sturgeons.     

The aged nonhematopoietic environment impairs natural killer cell maturation and function

Natural killer (NK) cells are critical in eliminating tumors and viral infections, both of which occur at a high incidence in the elderly. Previous studies showed that aged NK cells are less cytotoxic and exhibit impaired maturation compared to young NK cells. We evaluated whether extrinsic or intrinsic factors were responsible for the impaired maturation and function of NK cells in aging and whether impaired maturation correlated with functional hyporesponsiveness. We confirmed that aged mice have a significant decrease in the frequency of mature NK cells in all lymphoid organs. Impaired NK cell maturation in aged mice correlated with a reduced capacity to eliminate allogeneic and B16 tumor targets in vivo. This could be explained by impaired degranulation, particularly by mature NK cells of aged mice. Consistent with impaired aged NK cell maturation, expression of T‐bet and Eomes, which regulate NK cell functional maturation, was significantly decreased in aged bone marrow (BM) NK cells. Mixed BM chimeras revealed that the nonhematopoietic environment was a key determinant of NK cell maturation and T‐bet and Eomes expression. In mixed BM chimeras, NK cells derived from both young or aged BM cells adopted an ‘aged’ phenotype in an aged host, that is, were hyporesponsive to stimuli in vitro, while adopting a ‘young’ phenotype following transfer in young hosts. Overall, our data suggest that the aged nonhematopoietic environment is responsible for the impaired maturation and function of NK cells. Defining these nonhematopoietic factors could have important implications for improving NK cell function in the elderly.     

Structure of a eukaryotic cytoplasmic pre‐40S ribosomal subunit

Final maturation of eukaryotic ribosomes occurs in the cytoplasm and requires the sequential removal of associated assembly factors and processing of the immature 20S pre‐RNA. Using cryo‐electron microscopy (cryo‐EM), we have determined the structure of a yeast cytoplasmic pre‐40S particle in complex with Enp1, Ltv1, Rio2, Tsr1, and Pno1 assembly factors poised to initiate final maturation. The structure reveals that the pre‐rRNA adopts a highly distorted conformation of its 3′ major and 3′ minor domains stabilized by the binding of the assembly factors. This observation is consistent with a mechanism that involves concerted release of the assembly factors orchestrated by the folding of the rRNA in the head of the pre‐40S subunit during the final stages of maturation. Our results provide a structural framework for the coordination of the final maturation events that drive a pre‐40S particle toward the mature form capable of engaging in translation.     

The simultaneous antagonistic effects of a T cell hybridoma product on the growth and the maturation of activated lymphocytes

Lymphocyte maturation and growth are two antagonistic events; therefore, successful antibody synthesis accompanied by clonal expansion, as seen in most humoral immune responses, must be the result of a delicate quantitative balance between maturation and growth factors. On the basis of this hypothesis, it should be feasible to search for a T cell product that alters this equilibrium and favors either B cell growth or maturation. In an attempt to isolate T cell hybridomas producing these activities, we fused BW5147 thymoma cells with Con A-activated spleen cells. One of the hybridomas obtained constitutively produces a product (or products) that selectively inhibits mitogen-induced replication but not maturation of normal but not transformed B lymphocytes. More importantly, the same product(s) supports Ig synthesis but not growth of LPS blasts, which suggests that we are dealing with a B cell maturation factor. The effect of this supernatant can be completely abrogated by the B cell mitogen DxS. In addition, the proliferative response of B cells to this ligand is unaffected by the hybridoma product. The implications of our results for understanding the mechanism of B cell triggering are discussed.