Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Apoptosis in Etiolated Wheat Seedlings: 1. Ultrastructure of the Apoptotic Cell

We studied the process of apoptosis in etiolated wheat (Triticum aestivum L.) seedlings. As a result, an integral pattern of the apoptotic plant cell ultrastructure was established. In the apoptotic cells of the coleoptile, we observed chromatin condensation and margination, an increased density and specific cytoplasm fragmentation accompanied by the appearance of unusual cytoplasmic vesicles containing subcellular organelles, mitochondria in particular, in the vacuoles.     

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Chromatin folding in human spermatozoa. I. Dynamics of chromatin remodelling in differentiating human spermatids

Changes in chromatin structure at different stages of differentiation of human spermatids were studied. It was shown that, in nuclei of early spermatids, chromatin is loosely packed and its structural element is an 8-nm fiber. This “elementary” fiber is predominant at the initial stages of differentiation; in the course of maturation, it is replaced by globular elements approximately 60 nm in diameter. In intermediate spermatids, these globules start to condense into fibrillar aggregates and reduce their diameter to 30–40 nm. At all stages of spermatid maturation, except the final stages, these globules are convergence centers for elementary fibers. This remodelling process is vectored and directed from the apical (acrosomal) to the basal pole of the nucleus. In mature spermatids, the elementary 8-nm fibers are almost absent and the major components are 40-nm fibrillar aggregates. The nuclei of mature spermatids are structurally identical with the nuclei of spermatozoa with the so-called “immature chromatin,” which are commonly found in a low proportion in sperm samples from healthy donors and may prevail over the normal cells in spermiogenetic disorders. The cause of this differentiation blockade remains unknown. Possibly, the formation of intermolecular bonds between protamines, which are required for the final stages of chromatin condensation, is blocked in a part of spermatids. The results of this study are discussed in comparison with the known models of nucleoprotamine chromatin organization in human spermatozoa.     

Apoptosis in the Initial Leaf of Etiolated Wheat Seedlings: Influence of the Antioxidant Ionol (BHT) and Peroxides

Apoptosis was observed in the initial leaf of 5-8-day-old etiolated wheat seedlings. A condensation of cytoplasm in apoptotic cells, formation of myelin-like structures, specific fragmentation of cytoplasm, appearance in vacuoles of specific vesicles containing subcellular organelles, condensation and margination of chromatin in the nucleus, and internucleosomal fragmentation of nuclear DNA are ultrastructural features of apoptosis in the initial wheat leaf. Single-membrane vesicles detected in vacuoles of the leaf cells resemble in appearance the vacuolar vesicles in the coleoptile apoptotic cells described earlier (Bakeeva, L. E., et al. (1999) FEBS Lett., 457, 122-125); they contain preferentially plastids but not mitochondria as was observed in coleoptile. The vacuolar vesicles are specific for the apoptotic plant cells. Thus, apoptosis in various tissues is an obligatory element of plant (wheat) growth and development even in the early stages of ontogenesis. Contrary to strong geroprotecting action in coleoptile, the known antioxidant BHT (ionol, 2.27·10^–4 M) does not prevent in the leaf cells the apoptotic internucleosomal DNA fragmentation and appearance of specific vacuolar vesicles containing subcellular organelles. Therefore, the antioxidant action on apoptosis in plants is tissue specific. Peroxides (H₂O₂, cumene hydroperoxide) stimulated apoptosis (internucleosomal DNA fragmentation) in coleoptile and induced it in an initial leaf when apoptosis in a control seedling leaf was not yet detected. Thus, apoptosis that is programmed in plant ontogenesis and controlled by reactive oxygen species (ROS) can be modulated by anti- and prooxidants.     

An Examination of the Association between 5-HTTLPR,Combat Exposure,and PTSD Diagnosis among U.S. Veterans

Objective

To examine the association between the 5-HTTLPR polymorphism of the serotonin transporter (SLC6A4) gene, combat exposure, and posttraumatic stress disorder (PTSD) diagnosis and among two samples of combat-exposed veterans.

Method

The first sample included 550 non-Hispanic Black (NHB) combat-exposed veterans. The second sample included 555 non-Hispanic White (NHW) combat-exposed veterans. Participants were genotyped for the 5-HTTLPR/rs25531 variants of the SLC6A4 gene. A structured clinical interview was used to diagnose PTSD. Combat and civilian trauma exposure were assessed with validated self-report instruments. Logistic regression was used to test for main effects of 5-HTTLPR on PTSD diagnosis as well as gene x environment (GxE) interactions after adjusting for sex, ancestry proportion scores, civilian trauma exposure, and combat exposure.

Results

Within the NHB sample, a significant additive effect was observed for 5-HTTLPR (OR = 1.502, p = .0025), such that the odds of having a current diagnosis of PTSD increased by 1.502 for each additional S’ allele. No evidence for an association between 5-HTTLPR and PTSD was observed in the NHW sample. In addition, no evidence for combat x 5-HTTLPR effects were observed in either sample.

Conclusion

The present study suggests that there may be an association between 5-HTTLPR genotype and PTSD diagnosis among NHB veterans; however, no evidence for the hypothesized 5-HTTLPR x combat interaction was found.