STRUCTURAL PARAMETERS OF AQUEOUS COLLOIDAL DISPERSIONS OF FULLERENE C60

Two types of fullerene C60 water dispersions were investigated by a small-angle X-ray and neutron scattering. As a result, structural parameters of fullerene aggregates were obtained. The water dispersions were obtained by the solvent-exchange technique and by huge dilution of initial C60/Nmethylpyrrolidone solution. The structure organization of water dispersions is considered in respect to their technique preparation. It was shown that fullerene aggregates were characterized by highly polydispersity in size for all dispersions. In the case of son/nC60 dispersion it was found that fullerenes formed aggregates with a dense nucleus (namely a surface fractal) with a radius of 58 ± 1 nm and a fractal dimension of 2.3. In turn, the nmp/nC60 system was characterized by the branched aggregates with fractal dimension 1.5 and bimodal particle size distribution.

“Crack, Reduce, and Implant”: A Safe Phaco Technique in a Case with Hard Brown Cataract

This report describes two maneuvers in different steps of phaco surgery in a case with hard cataract, which provide debulking of the central dense nucleus and prevents posterior capsule rupture (PCR). In the current case, clear corneal incisions were created, and anterior chamber was filled with ophthalmic viscosurgical device (OVD). Anterior capsule was punctured, and capsulorhexis was completed. Nucleus was cracked into two halves following vertical groove formation. Core nucleus was hollowed sideward bilaterally in the capsular bag. Nuclear halves were removed from capsular bag, and each one was pushed to one side on the iris plane. Capsular bag was inflated with OVD, and intraocular lens (IOL) was implanted. Nuclear halves were removed in confidence. The presented maneuvers initially reduce dense nucleus load in the safe zone and allow surgeon to use IOL as a barrier to protect floppy posterior capsule from early steps of the surgery.

Spermatogenesis and sperm morphology in Trophon geversianus (Gastropoda: Muricidae)

The ultrastructure of spermatogenesis, the euspermatozoa and paraspermatozoa, is investigated in Trophon geversianus. Spermatogenesis follows the general developmental pattern of caenogastropods. Paraspermatid development is characterized by elongation of the cell, concurrent with the appearance of a cytoplasmic elongation at the apex of the cell and the breakdown of the nucleus into small round fragments (caryomerites). Euspermatozoa consist of: a tall, conical acrosomal vesicle (with a invagination); a rod-shaped, highly electron-dense nucleus with an internal axoneme; an elongate midpiece consisting of the axoneme sheathed by helical mitochondrial elements; an elongate glycogen piece; and a short free-tail region. Paraspermatozoa of T. geversianus are vermiform. They contain approximately 12–16 axonemes arranged peripherally, numerous oblong dense vesicles, numerous less dense (round) vesicles, and scattered mitochondria. Most of the euspermatozoal features of T. geversianus are also observed in many neogastropods. However, the presence of the axoneme continuously located inside of the nucleus has not been reported before, and may prove to be a diagnostic feature of the Muricidae.

A New Dynamical Parameter for the Study of Sticky Orbits in a 3D Galactic Model

A 3D dynamical model is used to study the motion in the central parts of an elliptical galaxy, hosting a massive and dense nucleus. Our aim is to investigate the regular or chaotic character of the motion, with emphasis in the different chaotic components, as well as the sticky regions of the dynamical system. In order to define the character of the motion in the 2D system, we use the classical method of the Poincaré x − p

Ultrastructure of spermatogenesis and the mature spermatozoon of Haplobothrium globuliforme Cooper, 1914 (Cestoda: Haplobothrioidea)

The process of spermatogenesis and the structure of the mature spermatozoon of Haplobothrium globuliforme Cooper, 1914 were examined using transmission electron microscopy. Spermatogonia have a low cytoplasmic to nuclear volume ratio, and contain numerous free ribosomes and few mitochondria. Quaternary spermatogonia have a rosette appearance with the eight nuclei surrounding a central cytoplasmic cytophore. Spermatocytes, the largest of the developing sperm cells, contain free ribosomes and several mitochondria with pronounced cristae. No synaptonemal complexes and few endoplasmic reticulum formations were seen. Early spermatids show a regular arrangement of the nucleus, Golgi apparatus, and mitochondria. This regularity is disrupted as spermiogenesis commences, with the formation of the zone of differentiation, a conical indentation of the spermatid cytoplasm. This zone of differentiation is bordered by microtubules. Within the zone develop two interconnected basal bodies with their respective flagellar rootlets. From each basal body arises an axoneme with the 9 + "1" microtubular configuration. The axonomes elongate, eventually fusing with a cytoplasmic extension of the zone of differentiation, and the condensed nucleus migrates into the sperm body. The mature spermatozoon is elongate (30 μm long) and slender, and possesses an electron-dense nucleus, two lateral axonemes, α and β glycogen, and peripheral microtubules. The importance of sperm ultrastructure with respect to phylogeny is discussed.

The comparative ultrastructure of spermatozoa from Bothrimonus sturionis Duv. 1842 (Pseudophyllidea), Pseudanthobothrium hanseni Baer, 1956 (Tetraphyllidea), and Monoecocestus americanus Stiles, 1895 (Cyclophyllidea)

The mature spermatozoa from Bothrimonus sturionis (Pseudophyllidea), Pseudanthobothrium hanseni (Tetraphyllidea), and Monoecocestus americanus (Cyclophyllidea) were examined using transmission electron microscopy. Transverse sections of the sperm of B. sturionis indicate that the number of sperm axonemes varies from one to eight, with approximately one-third of the sperm containing two axonemes. Likewise, the number of peripheral microtubules lying just within the external plasma membrane varies from 12 to 20. The nucleus is electron lucent and fibrous in appearance. The spermatozoa of B. sturionis show great variation in the material examined and the majority of them are believed to be aberrant. The spermatozoon of P. hanseni contains a single axoneme with the nucleus wrapped in a crescent around it in the anterior region of the sperm. The posterior portion of the spermatozoon is characterized by a helical flange which projects from the main body of the sperm. The spermatozoon of M. americanus is elongate and slender, containing a single axoneme with an electron-dense nucleus coiled around it in the anterior one-third of the sperm. Electron-opaque bodies, which may be glycogen, fill the cytoplasm. The spermatozoa of all three species contain neither an acrosome nor mitochondria. The flagella of all the spermatozoa have a 9 + "1" arrangement of microtubules. The importance of the ultrastructure of spermatozoa in the phylogeny and taxonomy of cestodes is discussed.

THE RABBIT ZYGOTE

The formation of the blastomere nucleus was examined in the rabbit zygote with the electron microscope. In late anaphase the chromosomes are bare and vesicles of the smooth endoplasmic reticulum are numerous in the vicinity of the chromosomes. In early telophase individual chromosomes attain their own nuclear envelope and they are called karyomeres. The envelope of the karyomeres contains small gaps within it at several places where the chromatin is exposed to the cytoplasm. Nuclear pores are also observed. In the cytoplasm short annulate lamellae appear adjacent to the karyomeres, and clusters of punctate substance are also present. From early telophase onward the karyomeres extend pseudopod-like structures, called karyopods, which extend toward other karyomeres or karyopods, and consequently fuse together and serve as chromosomal bridges. Eventually all of the karyomeres fuse into a dense nucleus and decondensation of the chromosomes occurs.