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In the present study, the distribution and dynamic expression of serotonin and dopamine in the nervous system and ovary of the sea cucumber, Holothuria scabra, during different ovarian stages were investigated. We found that serotonin-immunoreactivity was more intense in the neurons and neuropils of the outer ectoneural part, the inner hyponeural part, and the wall of hyponeural canal of radial nerve cord during the mature stages of ovarian cycle, whereas dopamine-immunoreactivity was detected at a higher intensity in these tissues during the early stages. Both neurotransmitters were detected in the ectoneural part of the nerve ring. In the ovary, serotonin intensity was more intense in the cytoplasm of late oocytes, while dopamine-immunoreactivity was more intense in the early stages. The changes in the levels serotonin in the radial nerve cord and oocytes are incremental towards the late stages of ovarian maturation. In contrast, dopamine levels in the nervous tissues and oocytes were more intense in early stages and became decremental towards the late stages. These findings suggest that serotonin and dopamine may have opposing effects on ovarian development in this sea cucumber species. [ABSTRACT FROM AUTHOR]

Tropomyosins (Tm) in humans are expressed from four distinct genes and by alternate splicing >40 different Tm polypeptide chains can be made. The functional Tm unit is a dimer of two parallel polypeptide chains and these can be assembled from identical (homodimer) or different (heterodimer) polypeptide chains provided both chains are of the same length. Since most cells express multiple isoforms of Tm, the number of different homo and heterodimers that can be assembled becomes very large. We review the mechanism of dimer assembly and how preferential assembly of some heterodimers is driven by thermodynamic stability. We examine how in vitro studies can reveal functional differences between Tm homo and heterodimers (stability, actin affinity, flexibility) and the implication for how there could be selection of Tm isomers in the assembly on to an actin filament. The role of Tm heterodimers becomes more complex when mutations in Tm are considered, such as those associated with cardiomyopathies, since mutations can appear in only one of the chains. [ABSTRACT FROM AUTHOR]

In this study, we aimed to detect morphological and biochemical changes in developing germ cells (Gc), testicular sperm (Tsp), and spawned sperm (Ssp) using capacitation-associated characteristics. Gradual changes in the profiles of two membrane proteins, namely NaCl- and detergent-extractable proteins, were observed as compared Gc with Tsp and Tsp with Ssp. These membrane modifications were accomplished mostly through the introduction of new protein sets, both peripheral and integral, into Tsp and Ssp membranes. Activation of serine proteases, particularly in Ssp detergent-extracted proteins with the molecular masses of 38–130 kDa was evident and marked a major difference between Ssp and Tsp. An increase in the level of tyrosine phosphorylation of the proteins ranging from 15 to 20 kDa was noted in Tsp and remained constant in Ssp. Specifically, these three capacitation-associated characteristics could be detected in Ssp, possessing full fertilizing capacity. The lack of an activated proteolytic activity in Tsp resulted in a delayed fertilization, but not affected fertilizing ability. We believe that these characteristics should be advantageous in predicting abalone sperm fertilizing capability, particularly in cases when isolated germ cells or purified Tsp are used in place of spawned sperm in abalone aquaculture. [ABSTRACT FROM AUTHOR]

We have investigated the cellular characteristics, especially chromatin condensation and the basic nuclear protein profile, during spermiogenesis in the common tree shrew, Tupaia glis. Spermatids could be classified into Golgi phase, cap phase, acrosome phase, and maturation phase. During the Golgi phase, chromatin was composed of 10-nm and 30-nm fibers with few 50-nm to 60-nm knobby fibers. The latter were then transformed into 70-nm knobby fibers during the cap phase. In the acrosome phase, all fibers were packed into the highest-order knobby fibers, each about 80–100 nm in width. These chromatin fibers became tightly packed in the maturation phase. In a mature spermatozoon, the discoid-shaped head was occupied by the acrosome and completely condensed chromatin. H3, the core histone, was detected by immunostaining in all nuclei of germ cell stages, except in spermatid steps 15–16 and spermatozoa. Protamine, the basic nuclear protein causing the tight packing of sperm chromatin, was detected by immunofluorescence in the nuclei of spermatids at steps 12–16 and spermatozoa. Cross-immunoreactivity of T. glis H3 and protamine to those of primates suggests the evolutionary resemblance of these nuclear basic proteins in primate germ cells. [ABSTRACT FROM AUTHOR]