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1

Molecular aspects of muscle development

100%

Cieslak D.

Biotechnologia

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1999

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issue 1

59-66

EN

An exceptional muscle development in some meat-producing animals is due to the increase in the number of muscle fibers (hyperplasia) or increase in their individual diameter (hypertrophy). The genetic mechanism of the former is well known. It results from mutation in the myostatin gene. The determination of muscular hypertrophy is poorly understood. In pigs this phenomenon is associated with muscular hypermetabolism and contraction induced by stress. Muscle development is controlled by genes called muscular regulatory factors. Four genes belong to this family: myogenin, myf-3, myf-5 and MRF4. While myf-3 and myf-5 are responsible for establishment and maintenance of skeletal myoblasts, myogenin and MRF4 control differentiation of myoblasts into myotubes. Their activity is influenced by other genes and physiological factors. Understanding of the mechanisms involved in myogenesis would provide a useful tool for controlling meat production in farm animals.

2

Activation of mammalian oocytes in vitro

63%

Cieslak D., Lechniak D.

Biotechnologia

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1998

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issue 3

52-60

EN

Parthenogenesis is a phenomenon accompanying the in vitro oocyte culture. It is stimulated by a variety of physical and chemical factors which oocytes are facing in vitro. As a consequence of artificial activation, a few different types of parthenones can be formed. Commonly observed are homogenous haploid parthenogenones but also mosaic haploids and diploids can arise. The karyotype of parthenones is not stable and can undergo modifications during further development. Mammalian parthenones do not usually develop beyond the blastocyst stage. Up to now, only one experiment carried out on sheep parthenones has demonstrated their developmental competence up to the 26th day of gestation. Usually, most parthenones die shortly after activation because of damages caused by the activating factors and decreased developmental potential. Moreover, the rate of parthenogenetic development, compared to IVF embryos, is delayed. Since the mechanism of parthenogenesis in mammals still remains unclear, the problem needs further studies.

3

Morphology and developmental potential of bovine parthenotes after spontaneous activation in vitro

51%

Lechniak D., Cieslak D., Sosnowski J.

Journal of Applied Genetics

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1998

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vol. 39

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issue 2

193-198

EN

Spontaneous parthenogenetic activation of bovine oocytes in an in vitro maturation and fertilization system (IVM/IVF) is described. Altogether, 1403 follicular oocytes, collected by the aspiration method, were matured in vitro and then cultured without insemination in the same conditions as a group of inseminated oocytes. After 48-72 h of additional culture, 141 oocytes (10%) were found to be spontaneously activated. Morphological evaluation revealed that the number of blastomeres within parthenotes ranged from 2 to 16 cells, with a minority (15.7%) comprising of 9-16 blastomeres. According to a cytogenetic analysis, only 1.2% of the analysed parthenotes consisted of more than 9 cells. Parthenotes may not be distinguished from embryos produced in vitro and spontaneous parthenogenetic activation in an IVM/IVF system indicates suboptimal culture conditions. A group of non-inseminated oocytes should be included in each experiment to serve as a control. Spontaneously activated bovine parthenotes only occasionaly developed beyond the 8-blastomere stage in a common IVM/IVF system. The incidence of parthenotes interferes with the efficiency of in vitro embryo production but it is doubtful whether it lowers the pregnancy rate after transfer of IVF embryos.

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2 Biotechnologia

1 Journal of Applied Genetics

1 1999

2 1998

3 Cieslak D.

2 Lechniak D.

1 Sosnowski J.

Molecular aspects of muscle development

Activation of mammalian oocytes in vitro

Morphology and developmental potential of bovine parthenotes after spontaneous activation in vitro