The variable success of in vitro maturation: can we do better?

The efficiency of in vitro assisted reproductive technologies, consisting of the transfer of embryos obtained in vitro through in vitro maturation, in vitro fertilization and early embryo culture is still limited. The quality of the oocytes is pivotal for assisted reproductive efficiency and the maturation of the oocyte represents the first key limiting step of the in vitro embryo production system. At the time of removal from the antral follicles, the oocyte is still completing the final growth and differentiation steps, needed to provide the so-called developmental competence, i.e. the machinery required to sustain fertilization and embryo development. In mono-ovular species only one oocyte per cycle is available for procreation, therefore the current assisted reproduction techniques strive to overcome this natural boundary. However, the success is still limited and overall the effectiveness does not exceed the efficiency achieved in millions of years of mammalian evolution. One of the problems lies in the intrinsic heterogeneity of the oocytes that are subjected to in vitro maturation and in the lack of dedicated in vitro approaches to finalize the differentiation process. In this review we will try to overview some of the salient aspects of current practices by emphasizing the most critical and fundamental features in oocyte differentiation that should be carefully considered for improving current techniques

The variable success of in vitro maturation: can we do better?

The efficiency of in vitro assisted reproductive technologies, consisting of the transfer of embryos obtained in vitro through in vitro maturation, in vitro fertilization and early embryo culture is still limited. The quality of the oocytes is pivotal for assisted reproductive efficiency and the maturation of the oocyte represents the first key limiting step of the in vitro embryo production system. At the time of removal from the antral follicles, the oocyte is still completing the final growth and differentiation steps, needed to provide the so-called developmental competence, i.e. the machinery required to sustain fertilization and embryo development. In mono-ovular species only one oocyte per cycle is available for procreation, therefore the current assisted reproduction techniques strive to overcome this natural boundary. However, the success is still limited and overall the effectiveness does not exceed the efficiency achieved in millions of years of mammalian evolution. One of the problems lies in the intrinsic heterogeneity of the oocytes that are subjected to in vitro maturation and in the lack of dedicated in vitro approaches to finalize the differentiation process. In this review we will try to overview some of the salient aspects of current practices by emphasizing the most critical and fundamental features in oocyte differentiation that should be carefully considered for improving current techniques(AU)

Control of oocyte maturation

Oocyte maturation is a complex process involving nuclear and cytoplasmic maturation. The nuclear maturation is a chromosomal segregation and the cytoplasmic maturation involves the reorganization of the cytoplasmic organelles, mRNA transcription and storage of proteins to be used during fertilization and early embryo development. The mechanism of oocyte maturation in vivo and in vitro still are not totally understood. However it is generally accepted that the second messenger cyclic adenosine monophosphate (cAMP) plays a critical role in the maintenance of meiotic blockage of mammalian oocytes. A relative increase in the level of cAMP within the oocyte is essential for maintaining meiosis block, while a decrease in cAMP oocyte concentration allows the resumption of meiosis. The oocyte cAMP concentration is regulated by a balance of two types of enzymes: adenylate cyclase (AC) and phosphodiesterases (PDEs), which are responsible for the synthesis and degradation of cAMP, respectively. After being synthesized by AC in cumulus cells, cAMP are transferred to the oocyte through gap junctions. Thus, specific subtypes PDEs are able to inhibit or attenuate the spontaneous meiotic maturation of oocytes with PDE4 primarily involved in the metabolism of cAMP in granulosa cells and PDE3 in the oocyte. Although the immature oocytes can resume meiosis in vitro, after being removed from antral follicles, cytoplasmic maturation seems to occur asynchronously with nuclear maturation. Therefore, knowledge of the oocyte maturation process is fundamental for the development of methodologies to increase the success of in vitro embryo production and to develop treatments for various forms of infertility. This review will present current knowledge about the maintenance of the oocyte in prophase arrest, and the resumption of meiosis during oocyte maturation, focusing mainly on the changes that take place in the oocyte.

Control of oocyte maturation

Oocyte maturation is a complex process involving nuclear and cytoplasmic maturation. The nuclear maturation is a chromosomal segregation and the cytoplasmic maturation involves the reorganization of the cytoplasmic organelles, mRNA transcription and storage of proteins to be used during fertilization and early embryo development. The mechanism of oocyte maturation in vivo and in vitro still are not totally understood. However it is generally accepted that the second messenger cyclic adenosine monophosphate (cAMP) plays a critical role in the maintenance of meiotic blockage of mammalian oocytes. A relative increase in the level of cAMP within the oocyte is essential for maintaining meiosis block, while a decrease in cAMP oocyte concentration allows the resumption of meiosis. The oocyte cAMP concentration is regulated by a balance of two types of enzymes: adenylate cyclase (AC) and phosphodiesterases (PDEs), which are responsible for the synthesis and degradation of cAMP, respectively. After being synthesized by AC in cumulus cells, cAMP are transferred to the oocyte through gap junctions. Thus, specific subtypes PDEs are able to inhibit or attenuate the spontaneous meiotic maturation of oocytes with PDE4 primarily involved in the metabolism of cAMP in granulosa cells and PDE3 in the oocyte. Although the immature oocytes can resume meiosis in vitro, after being removed from antral follicles, cytoplasmic maturation seems to occur asynchronously with nuclear maturation. Therefore, knowledge of the oocyte maturation process is fundamental for the development of methodologies to increase the success of in vitro embryo production and to develop treatments for various forms of infertility. This review will present current knowledge about the maintenance of the oocyte in prophase arrest, and the resumption of meiosis during oocyte maturation, focusing mainly on the changes that take place in the oocyte. (AU)

EMPREGO DO SISTEMA SPOM NA UTILIZAÇÃO DE MODULADORES DE AMPc DURANTE MATURAÇÃO OOCITÁRIA IN VITRO NA PRODUÇÃO DE EMBRIÕES BOVINOS

Adenosina monofosfato cíclica (AMPc) é uma molécula importante na transdução de sinal dentro da célula, que funciona como um segundo mensageiro celular da estimulação de gonadotrofinas.Um dos principais obstáculos para o sucesso total da produção in vitro de embriões (PIVE) é reproduzir adequadamente in vitro os eventos que ocorrem na maturação oocitária.Quando o oócito é liberado mecanicamente do folículo para a PIVE, os níveis intra-oocitários de AMPc diminuem, dando início a chamada maturação nuclear espontânea, levando a uma perda de sincronia com a maturação citoplasmática. Muitos estudos demonstraram que níveis mais elevados de AMPc antes da MIV melhoram a competência do oócito, levando a benefícios subsequentes no desenvolvimento embrionário. Dentre as diversas abordagens já descritas e propostas com a modulação dos níveis de AMPc, a aplicação do sistema bifásico " Simulated Phisiological Oocyte Maturation" (SPOM) ganhou bastante notoriedade, - apresentando reflexos positivos na produção de embriões - e atraiu considerável atenção ao longo dos anos. No entanto, por não sustentar os resultados positivos sempre que aplicado, teve sua credibilidade questionada e foi considerada ineficaz sob condições variadas. Considerando seus efeitos positivos e a possibilidade de otimização da etapa de MIV com seu uso, o objetivo deste estudo foi compreender as variáveis envolvidas na eficácia do sistema de maturação SPOM e buscar adaptações que permitam a sua utilização de forma bem sucedida, de maneira que isso se reflita na produção de embriões bovinos.Para isto, form realizados três estudos apresentados em tres capítulos experimentias. No primeiro capítulo, foi avaliado o efeito de uma adaptação no tempo de duração do sistema na produção de embriões bovinos, considerando parâmetros de qualidade; e os resultados observaram um efeito positivo da adaptação sobre a produção dos embriões que não afetou os parâmetros de qualidade observados.Já no segundo capítulo, testou-se a possibilidade de reprodução do sistema fora do meio base de maturação comercial em que ele foi desenvolvido quando proposto, e o possível efeito dessa mudança sobre a qualidade e o metabolismo dos embriões produzidos. Observou-se que o sistema pode ser empregado fora do meio de origem sem influência nas taxas de produção ou qualidade dos embriões, mas parece afetar negativamente a atividade metabólica dos embriões. E por fim, o terceiro capítulo compilou os estudos envolvendo o sistema para compreensão de sua evolução e pontuou os possíveis motivos para falhas através de comparações com o estudo original. Concluiu-se que embora extremamente delicado, o sistema é capaz de responder positivamente a alterações e pode ser reproduzido fora do meio de maturação de origem. No entanto, os resultados sugerem que as diferentes suplementações no meio de MIV podem constituir uma variável de importância em sua eficácia e demonstram que o sucesso envolvido em sua adequada aplicação está diretamente relacionada a protocolos laboratoriais utilizados pelo grupo de pesquisa responsável por sua idealização.

Cyclic adenosine monophosphate (cAMP) is an important molecule in signal transduction within the cell, functioning as a second cell messenger of gonadotrophin stimulation. One of the main obstacles for the full success of the in vitro embryo production is to reproduce properly in vitro the events that occur on the oocyte maturation. When the oocyte is mechanically released from the follicle to IVP, the intraoocyte levels of cAMP decrease, and a non-physiologically meiotic resumption begins leading to a loss of synchrony with cytoplasmic maturation. Many studies have shown that higher levels of cAMP prior to IVM improve oocyte competence, leading to benefits in embryonic development. Among the several approaches already described regarding the cAMP levels modulation, the biphasic system "Simulated Physiological Oocyte Maturation" (SPOM) had a lot of notoriety, - with positive repercussions on embryo production- and attracted considerable attention over the years. However, by failing to sustain positive results whenever applied, it was considered ineffective under different conditions. Considering its positive effects and its possibility of optimizing the IVM stage, the aim of this study was to understand the variables involved in the effectiveness of the SPOM and to seek adaptations that allow its use in a successful way. In the first chapter, it was evaluated the effect of an adaptation in the SPOM IVM duration on the bovine embryo production considering quality parameters; and the results showed a positive effect on embryo production that did not affect their quality. In the second chapter, the possibility of reproducing the system without the IVM commercial medium was tested through the quality and metabolism of produced embryos. It was observed that the system can be used without the commercial medium without influencing the production rates or embryo quality, however, the embryos metabolic activity appears to be negatively affected. Finally, the third chapter compiled the studies involving the system to understand its evolution and pointed out possible reasons for failures through comparisons with the original study. It was concluded that although extremely delicate, the system is able to respond positively to changes and can be reproduced without the IVM original medium use. However, the results suggest that the excess of supplements in the IVM medium can be a variable of importance in its effectiveness and demonstrate that the success involved in its application is directly related to laboratory protocols used by the research group responsible for its development .

A proposal of a diagnostic protocol for isolation of Corynebacterium ulcerans from cow's milk

Background: Literature about presence Corynebacterium ulcerans in milk samples from cows with mastitis is rare and in the literature there are only a few reports. In this study the isolation and identification of Corynebacterium ulcerans from mastitis in dairy cows were done. Also, optimization of diagnostic protocols to identify Corynebacterium ulcerans was performed. Materials, Methods & Results: The investigation was performed at the cattle farm that is characterized by closed housing system diary Holstein-Friesian cows during an outbreak of acute mastitis. Milk samples from 298 lactating cows were collected in sterile sampling tubes. Before the collection of quarter milk samples, the udder was thoroughly cleaned with soap and water and rubbed to dry. All collected milk samples were examined for mastitis using California mastitis test, which was carried out by the method first described by Schalm and Noorlander. Equal volumes (5 mL) of commercial CMT reagent and quarter milk were mixed and the changes in milk fluidity and viscosity were observed. Sample portions (0.1 mL each) were inoculated on 10% sheep blood agar, Endo agar and Sabouraud agar as well as on thioglycolate medium and nutrient broth. Primary plates were incubated for 3 days at 37ºC in aerobic conditions. Cultural, morphological and conventional biochemical testing was done. The survey was complemented by double CAMP and plasma coagulation tube test. All 14 isolates developed a synergistic haemolysis with Rhodococcus equi (ATCC 6939) and inverse CAMP phenomenon with Staphylococcus aureus and coagulated rabbit plasma. Final diagnosis was confirmed using API Coryne V 2.0 and software program by BioMerieux1, revealing an identity rate of 99.9%, accuracy rate T = 1, test count = 0. Discussion: The first fourteen isolates of Corynebacterium ulcerans have been identified in our country, on the basis of a diagnostic protocol that is proposed in this paper. In our experience double CAMP test, rabbit plasma coagulation, catalase, oxidase tests and selected biochemical parameters, are sufficient as a diagnostic minimum. In the diagnostics of bacterial agents in cow mastitis, the attention of a bacteriologist is mostly limited to most widespread agents of mastitis, the isolation of which is mandatory pursuant to national legislation (Staphylococcus aureus and Streptococcus agalactiae). A more important reason for "missing" Corynebacterium ulcerans in the diagnosis is its colonial morphology that could resemble organisms of the genus Staphylococcus. Complex and expensive diagnostic procedure that is not available to most laboratories is also responsible for the small number of reports of isolation C. ulcerans. Furthermore, in routine work C. ulcerans could be misidentified with Staphylococcus intermedius, because of cultural similarity, positive plasma coagulation tube test and absence of manitol fermentation of both species. This paper is a report on isolation and identification of Corynebacterium ulcerans from milk of cows with mastitis, as well as a suggestion of a diagnostic protocol available for routine work in most veterinary microbiology laboratory. Therefore we suggest as the diagnostic protocol double CAMP test to be used as a complementary method to rabbit plasma coagulation tube test.

A proposal of a diagnostic protocol for isolation of Corynebacterium ulcerans from cows milk / A proposal of a diagnostic protocol for isolation of Corynebacterium ulcerans from cows milk

Background: Literature about presence Corynebacterium ulcerans in milk samples from cows with mastitis is rare and in the literature there are only a few reports. In this study the isolation and identification of Corynebacterium ulcerans from mastitis in dairy cows were done. Also, optimization of diagnostic protocols to identify Corynebacterium ulcerans was performed.Materials, Methods & Results: The investigation was performed at the cattle farm that is characterized by closed housing system diary Holstein-Friesian cows during an outbreak of acute mastitis. Milk samples from 298 lactating cows were collected in sterile sampling tubes. Before the collection of quarter milk samples, the udder was thoroughly cleaned with soap and water and rubbed to dry. All collected milk samples were examined for mastitis using California mastitis test, which was carried out by the method first described by Schalm and Noorlander. Equal volumes (5 mL) of commercial CMT reagent and quarter milk were mixed and the changes in milk fluidity and viscosity were observed. Sample portions (0.1 mL each) were inoculated on 10% sheep blood agar, Endo agar and Sabouraud agar as well as on thioglycolate medium and nutrient broth. Primary plates were incubated for 3 days at 37o C in aerobic conditions. Cultural, morphological and conventional biochemical testing was done. The survey was complemented by d

Background: Literature about presence Corynebacterium ulcerans in milk samples from cows with mastitis is rare and in the literature there are only a few reports. In this study the isolation and identification of Corynebacterium ulcerans from mastitis in dairy cows were done. Also, optimization of diagnostic protocols to identify Corynebacterium ulcerans was performed.Materials, Methods & Results: The investigation was performed at the cattle farm that is characterized by closed housing system diary Holstein-Friesian cows during an outbreak of acute mastitis. Milk samples from 298 lactating cows were collected in sterile sampling tubes. Before the collection of quarter milk samples, the udder was thoroughly cleaned with soap and water and rubbed to dry. All collected milk samples were examined for mastitis using California mastitis test, which was carried out by the method first described by Schalm and Noorlander. Equal volumes (5 mL) of commercial CMT reagent and quarter milk were mixed and the changes in milk fluidity and viscosity were observed. Sample portions (0.1 mL each) were inoculated on 10% sheep blood agar, Endo agar and Sabouraud agar as well as on thioglycolate medium and nutrient broth. Primary plates were incubated for 3 days at 37o C in aerobic conditions. Cultural, morphological and conventional biochemical testing was done. The survey was complemented by d

Involvement of G proteins and cAMP in the production of chitinolytic enzymes by Trichoderma harzianum

The effect of G protein modulators and cyclic AMP (cAMP) on N-acetylglucosaminidase (NAGase) production was investigated during 84 h of growth of a Trichoderma harzianum strain in chitin-containing medium. Caffeine (5 mM), N6--2'-O-dibutyryladenosine 3'5'-cyclic monophosphate sodium salt (dBcAMP) (1 mM) and 3-isobutyl-1-methylxanthine (IBMX) (2 mM) decreased extracellular NAGase activity by 80%, 77% and 37%, respectively. AlCl3/KF (100 µM/10 mM and 200 µM/ 20 mM) decreased the activity by 85% and 95%, respectively. Cholera (10 µ/mL) and pertussis (20 µ/mL) toxins also affected NAGase activity, causing a decrease of approximately 75%. Upon all treatments, protein bands of approximately 73 kDa, 68 kDa and 45 kDa had their signals diminished whilst a 50 kDa band was enhanced only by treatment with cholera and pertussis toxins. N-terminal sequencing analysis identified the 73 kDa and 68 kDa proteins as being T. harzianum NAGase in two different truncated forms whereas the 45 kDa band comprised a T. harzianum endochitinase. The 50 kDa protein showed sequence similarity to Coriolus vesicolor cellobiohydrolase. The above results suggest that a signaling pathway comprising G-proteins, adenylate cyclase and cAMP may be involved in the synthesis of T. harzianum chitinases.

O efeito de cAMP e de moduladores de proteínas G sobre a produção de N-acetilglicosaminidase (NAGase) foi investigado durante o crescimento de Trichoderma harzianum em meio contendo quitina. Cafeína (5 mM), dBcAMP (1mM) e IBMX (2 mM) provocaram diminuições na atividade extracelular de NAGase em 80%, 77% e 37%, respectivamente. Por outro lado, a presença de AlCl3/KF nas concentrações de 100 µM/10 mM e 200 µM/ 20 mM causou decréscimo na atividade em 85% e 95%, respectivamente. A toxina do cólera (10 µ/mL) e a toxina pertussis (20 µ/mL) também afetaram a atividade de NAGase, causando um decréscimo de aproximadamente 75%. Análises eletroforéticas mostraram que todos os tratamentos citados causaram diminuição no sinal de bandas correspondendo a polipeptídios de 73 kDa, 68 kDa e 45 kDa, enquanto uma banda de 50 kDa foi intensificada apenas com tratamento com as toxinas do cólera e pertussis. Análises de sequenciamento N-terminal permitiram a identificação das proteínas de 73 kDa e 68 kDa como sendo NAGase de T. harzianum em duas formas diferentemente processadas enquanto a banda de 45 kDa correspondeu a uma endoquitinase de T. harzianum. A proteína de 50 kDa mostrou similaridade de sequência com uma celobiohidrolase de Coriolus vesicolor. Os resultados sugerem que uma via de sinalização composta por proteínas G, adenilato ciclase e cAMP possa estar envolvida na produção de quitinases T. harzianum.

A proposal of a diagnostic protocol for isolation of Corynebacterium ulcerans from cows milk / A proposal of a diagnostic protocol for isolation of Corynebacterium ulcerans from cows milk

Background: Literature about presence Corynebacterium ulcerans in milk samples from cows with mastitis is rare and in the literature there are only a few reports. In this study the isolation and identification of Corynebacterium ulcerans from mastitis in dairy cows were done. Also, optimization of diagnostic protocols to identify Corynebacterium ulcerans was performed.Materials, Methods & Results: The investigation was performed at the cattle farm that is characterized by closed housing system diary Holstein-Friesian cows during an outbreak of acute mastitis. Milk samples from 298 lactating cows were collected in sterile sampling tubes. Before the collection of quarter milk samples, the udder was thoroughly cleaned with soap and water and rubbed to dry. All collected milk samples were examined for mastitis using California mastitis test, which was carried out by the method first described by Schalm and Noorlander. Equal volumes (5 mL) of commercial CMT reagent and quarter milk were mixed and the changes in milk fluidity and viscosity were observed. Sample portions (0.1 mL each) were inoculated on 10% sheep blood agar, Endo agar and Sabouraud agar as well as on thioglycolate medium and nutrient broth. Primary plates were incubated for 3 days at 37o C in aerobic conditions. Cultural, morphological and conventional biochemical testing was done. The survey was complemented by d

Background: Literature about presence Corynebacterium ulcerans in milk samples from cows with mastitis is rare and in the literature there are only a few reports. In this study the isolation and identification of Corynebacterium ulcerans from mastitis in dairy cows were done. Also, optimization of diagnostic protocols to identify Corynebacterium ulcerans was performed.Materials, Methods & Results: The investigation was performed at the cattle farm that is characterized by closed housing system diary Holstein-Friesian cows during an outbreak of acute mastitis. Milk samples from 298 lactating cows were collected in sterile sampling tubes. Before the collection of quarter milk samples, the udder was thoroughly cleaned with soap and water and rubbed to dry. All collected milk samples were examined for mastitis using California mastitis test, which was carried out by the method first described by Schalm and Noorlander. Equal volumes (5 mL) of commercial CMT reagent and quarter milk were mixed and the changes in milk fluidity and viscosity were observed. Sample portions (0.1 mL each) were inoculated on 10% sheep blood agar, Endo agar and Sabouraud agar as well as on thioglycolate medium and nutrient broth. Primary plates were incubated for 3 days at 37o C in aerobic conditions. Cultural, morphological and conventional biochemical testing was done. The survey was complemented by d