Evaluation of mitotic activity in tapetal cells of grapevine (Vitis L.)

The knowledge with reference to the grapevine tapetum has been centered on its anatomy/morphology and hardly anything at all is known about its mitotic activity throughout the microsporogenesis. The aim of this study was to ascertain the mitotic activity in tapetal cells of some grapevines (Vitis L.) broadening knowledge about this tissue and simultaneously corroborating the viability of its use as an alternative tissue for further cytogenetic studies. Young buds of 12 grapevine varieties at different meiotic stages were squashed and tapetal cells a prometaphase/metaphase scored in each meiotic stage. Mitotic activity was observed since the beginning of microsporogenesis, where it was more intense, decreasing toward tetrad. Polyploid tapetal cells arose through endomitosis while the microsporogenesis advanced. Two types of polyploid cells were evidenced, those with two or more individualized diploid chromosome groups and those with only one polyploid group. The percentage of diploid cells and of polyploid cells with two or more individualized diploid groups was higher during the first stage of microsporogenesis, though decreasing and giving way to cells with one large polyploid group as microsporogenesis moved toward tetrad. The nucleolus number was scored at interphase at different stages. Two and four nucleoli prevailed in tapetal cells at all stages except at tetrad where one large nucleolus was seen. The results showed that despite of the squashing technique applied, grapevine tapetum has a substantial amount of cells with mitotic activity with a satisfactory chromosome spreading therefore establishing an interesting alternative and promising tissue for later cytomolecular studies.

Primary Cardiac Burkitt Lymphoma Presenting with Abdominal Pain

We describe the case of a 44-year-old woman with primary Burkitt lymphoma of the heart who presented with abdominal bloating and epigastric discomfort secondary to tamponade physiology caused by a large pericardial effusion. The pericardial fluid contained a large number of highly atypical lymphocytes with moderate basophilic cytoplasm, rare punched-out vacuoles, a vesicular nuclear chromatin, large nucleolus, and marginated chromatin that by FISH were positive for the 8;14 translocation. She had no other sites of disease. She was treated with four alternating cycles of modified CODOX-M and IVAC in combination with rituximab and remains in remission more than 5 years since diagnosis.

Ultrastructure of spermatogenesis in the free-living marine nematode Pontonema vulgare (Enoplida, Oncholaimidae)

Spermatogenesis in testes of the free-living marine nematode Pontonema vulgare was studied with electron microscopy. The nucleus of spermatocytes has a large nucleolus; the cytoplasm is filled with numerous ribosomes, mitochondria, cisternae of the rough endoplasmic reticulum (RER), Golgi bodies, and flattened osmiophilic cisternae, which are interpreted as the modified membranous organelles (MO) of the spermatozoa of other nematodes studied. After completion of the second meiotic telophase, the nucleus is surrounded by a newly formed nuclear envelope. Further nucleus transformation includes condensation of the chromatin and shrinkage of the nuclear envelope. The deep infoldings of the nuclear envelope give a starlike shape to the nuclei. The cytoplasm of the early spermatids contains the same organelles as in the late spermatocytes, including MO. Many of the latter assume a cuplike or pocketlike shape. During spermatogenesis the peripheral cytoplasm containing the ribosomes, RER, Golgi bodies, and transparent vesicles moves to one pole of the cell forming the residual body. The main cell body of the late spermatid includes the nucleus, mitochondria, and MO embedded in a dense filamentous matrix. The fibrous bodies (FB) of a paracrystalline structure occur in spermatids throughout their developmental transformations. The central part of the spermatozoa contains a starlike nucleus with a nuclear envelope. The filamentous cytoplasm of the spermatozoa includes mitochondria and MO. The spermatozoa extracted from the testes form numerous long filopodia. The dense filamentous cytoplasm of the spermatozoa is continuous with the content of the filipodia. The reconstitution of the nuclear envelope and separate development of MO and FB described in P. vulgare spermatogenesis are the special characters of enoplid nematodes. The reduced character of FB development and simplified structure of MO differentiate P. vulgare from other nematodes studied.

TheDrosophila melanogastergenebrain tumornegatively regulates cell growth and ribosomal RNA synthesis

The regulation of ribosome synthesis is likely to play an important role in the regulation of cell growth. Previously, we have shown that the ncl-1 gene in Caenorhabditis elegans functions as an inhibitor of cell growth and ribosome synthesis. We now indicate that the Drosophila melanogaster tumor suppressor brain tumor (brat) is an inhibitor of cell growth and is a functional homolog of the C. elegans gene ncl-1. The brat gene is able to rescue the large nucleolus phenotype of ncl-1 mutants. We also show that brat mutant cells are larger, have larger nucleoli, and have more ribosomal RNA than wild-type cells. Furthermore, brat overexpressing cells contain less ribosomal RNA than control cells. These results suggest that the tumorous phenotype of brat mutants may be due to excess cell growth and ribosome synthesis.

Primary Amebic Meningoencephalitis Due to Naegleria fowleri in a South American Tapir

Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are known to cause fatal central nervous system (CNS) disease in human beings. N. fowleri causes acute, fulminating primary amebic meningoencephalitis (PAM), which generally leads to death within 10 days. Acanthamoeba spp. and B. mandrillaris cause chronic granulomatous amebic encephalitis, which may last for 8 weeks. Acanthamoeba spp. and B. mandrillaris also cause CNS disease in animals. N. fowleri, however, has been described only in human beings. This report is the first of PAM in an animal, a South American tapir. Dry cough, lethargy, and coma developed in the animal, and its condition progressed to death. At necropsy, lesions were seen in the cerebrum, cerebellum, and lungs. The CNS had severe, suppurative meningoencephalitis with many neutrophils, fibrin, plasma cells, and amebas. Amebas were 6.5 μm to 9 μm in diameter and had a nucleus containing a large nucleolus. Amebas in the sections reacted with a monoclonal antibody specific for N. fowleri in the immunofluorescent assay and appeared bright green.

Gall development and fine structure of the nutritive cells of Myopites blotii (Diptera, Tephritidae) on Inula salicina

The tephritid fly Myopites blotii attacks the flower head of Inula salicina at the outset of anthesis. Their larvae tunnel through tubular florets, achenes, and vertically through the swollen, densely vascularized floral receptacle. The goal of the mining larvae is the large vascular bundles at the base of the bracts. The tunneling larvae cut a number of vascular bundles irrigating the florets and the resulting cavity is always open to the outside. Cell walls and cell remnants are continuously agglomerated by the larvae along the entrance channel, forming a black layer. Small patches of nutritive cells appear near severed vascular bundles that end in the larval cavity. The nutritive cells are activated to a high level of RNA and proteosynthesis. The cells have a dense cytoplasm and a large lobed nucleus with a large nucleolus. The long, flexuous plastids form a perinuclear crown. Numerous mitochondria and peroxisomes attest to intense respiration in these cells. The nutritive cells provide proteins and nucleoproteins to the larvae that also feed directly on the vascular bundles ending in the larval cavities. The more sedentary, nearly mature larvae concentrate their feeding activity toward the bottom of the larval cavity where a nutritive layer differentiates. A sclerenchyma layer forms that isolates the larval cavity from the vascular bundles of the floral receptacle. Key words: gall, nutritive tissue, floral receptacle, Tephritidae, Inuleae, Asteraceae.

Absence of rDNA amplification in the uninucleolate oocyte of the cockroach Blattella germanica (Oorthoptera: Blattidae).

Amplification of the genes coding for ribosomal RNA oocurs in the oocytes of a wide variety of organisms. In oocytes of various species of crickets (Orthoptera: Gryllidae) the amplified DNA is contained in a large extrachromosomal DNA body. Multiple nucleoli form about the periphery of the DNA body during the diplotene stage of meiosis I. In contrast to the general pattern of orthopteran oocytes, oocytes of the cockroach Blattella germanica demonstrate a single large nucleolus instead of many nucleoli. In order to determine whether the genes coding for rRNA are amplified in the oocytes of B. germanica, the relative amount of rDNA in oocytes was compared with the rDNA content of spermatocytes and somatic cells. An extrachromosomal DNA body similar to that present in crickets is not present in B. germanica. A satellite DNA band which contains nucleotide sequences complementary to rRNA accounts for approximately 3-5% of the total DNA in somatic and in male and female gametogenic tissues. Female cells contain approximately twice as much rDNA as do male cells. An XX-XO sex-determining mechanism is operative in B. germanica. In situ hybridization with rRNA indicates that the nucleolar organizer is located on one end of the X chromosome and that oocytes do not contain more than twice the amount of rDNA found in spermato cytes. The data indicate that rDNA is not amplified in the uninucleolate oocyte of B germanica.

Germinal differentiation of the stem cell in Hydra fusca: a model system

The consecutive stages in the differentiation of the stem cell to the spermatozoon were characterized based on time of appearance, cytology, volumes, and spatial distribution. In the first few days the stem cells (128 μ3) enlarged and entered a phase of intense mitosis. In these cells or primary spermatogonia (220–1140 μ3), the cytoplasm was intensely basophilic, the DNA dispersed as a fine meshwork, and a large nucleolus was present. In secondary spermatogonia (123 μ3), noted after 14 days, the DNA was organized in small granules and the nucleolus reduced in size. The primary spermatocyte (122 μ3) was seen by 16 days; its cytoplasm was weakly basophilic, the nuclear DNA appeared granular, and a nucleolus was absent. After meiosis I, the secondary spermatocyte (60 μ3) immediately entered meiosis II. The spermatids (31 μ3), noted by 18 days, lacked a nucleolus and had dense irregular masses of DNA scattered throughout the nucleus. Spermatozoa, seen after 20 days, consisted of a cone-shaped head, a middle piece containing four large mitochondria, and a long flagellum. All these cell types were distributed sequentially within the testis according to their chronological order of appearance. The use of spermatogenesis as a model system to study cell differentiation and control requires further methodological developments and biochemical information.