Role of Radial Glia in Transformation of the Primitive Lumen to the Central Canal in the Developing Rat Spinal Cord

In the last quarter of the embryonic development of rat and shortly after a termination of neurogenesis, the transformation of the spinal cord primitive lumen (pL) to the central canal (CC) occurs. In this work, we show that this phenomenon is not an insignificant event but it is directly associated with the processes of gliogenesis. Using a light microscopy and immunohistochemistry, we monitored the development of the rat embryonic spinal cord from the end of the neurogenesis on the embryonic day 17 until the maturation of the spinal cord during the first postnatal weeks. Our observations demonstrate the importance of the transformation of the pL to the CC and its connection with gliogenesis, and the mechanism of this transformation is proposed. It is found that a segregation of the glutamate transporter (GLAST) immunopositive cells from the alar plates and transformation of the radial glial cells to the fibrous and protoplasmic astrocytes play presumably a key role in the diminution of the ventricular zone. Results indicate that the very transformation and migration of the radial glial cells during gliogenesis could result in a transformation of the pL to the CC.     

Immunochemical studies on blood groups. The combining site specificities of mouse monoclonal hybridoma anti-A and anti-B

Mouse monoclonal hybridomas, five anti-blood group A, three anti-B, and one anti-AB, produced by various methods of immunization, have been characterized by quantitative precipitin tests and the fine structures of their combining sites have been mapped by oligosaccharide inhibition assays. The combining sites of antibodies of each specificity differed among themselves. Three of the five monoclonals were specific for difucosyl and two for monofucosyl A determinants. All but the anti-AB were strictly specific for blood group A or blood group B erythrocytes; all of the anti-A monoclonals gave essentially equivalent titers in hemagglutination tests with A1 and A2 erythrocytes except for a monoclonal anti-A prepared by immunization with a human gastric cancer cell line. The data provide additional evidence for the heterogeneity of the antibody response to the different antigenic determinants present on blood A and B substances and emphasize the importance of difucosyl determinants which comprise most of the determinants on the water-soluble blood group substances.     

Different effects of eubacterial and eukaryotic DNA topoisomerase II inhibitors on chloroplasts ofEuglena gracilis

Inhibitors of eubacterial and eukaryotic DNA topoisomerases type II exhibited different effects on chloroplasts of the flagellateEuglena gracilis. Antibacterial agents (cinoxacin, nalidixic and oxolinic acids, ciprofloxacin, enoxacin, norfloxacin and ofloxacin) from the group of quinolones and coumarins (coumermycin A₁, clorobiocin and novobiocin) — all inhibitors of prokaryotic DNA topoisomerase II — were very potent eliminators of chloroplasts fromE. gracilis. In contrast, antitumor drugs (adriamycin, etoposide, teniposide and mitoxantrone) — antagonists of the eukaryotic counterpart — did not affect these semiautonomous photosynthetic organelles. These findings point out again the close evolutionary relationships between eubacteria and chloroplasts and are in agreement with the hypothesis of an endosymbiotic origin of chloroplasts.     

Characterization of a novel murine leukemia virus-related subgroup within mammals.

The murine leukemia virus (MuLV)-related retroviruses are one of seven genera which together constitute the family Retroviridae. They are widespread as both endogenous and exogenous agents within vertebrates and have been associated with a variety of malignancies and other disorders. We isolated and characterized 12 endogenous representatives of this genus from a number of mammalian hosts. Subsequent sequence analysis revealed that the isolated viruses cluster into two clearly distinct groups. All of the exogenous MuLV-related retroviruses which have been isolated to date, as well as several endogenous examples, fall into the first group, whereas the second group is represented solely by endogenous representatives, including human endogenous retrovirus type E (HERV.E). The two groups are widespread within mammals, with both often present within one animal species. Despite this, there is no evidence to date that recombination between members of the different groups has occurred. Genetic distances and several other properties of the HERV.E genome suggest that if exogenous members of this subgroup exist, they are likely to have biological properties different from those of the other exogenous viruses of this genus. Several of these viruses are known to have been integrated within their hosts' genomes for a long period of time, and a most recent divergence date for the MuLV and HERV.E subgroups can thus be proposed. This date, approximately 30 million years ago, is the most recent date possible, and it is probable that the actual period of time since their divergence is significantly longer.     

Invasive tall annual willowherb (<Emphasis Type="Italic">Epilobium brachycarpum</Emphasis> C. Presl) in Central Europe originates from high mountain areas of western North America

Identification of the source population of biological invasions has important consequences for the effective control and management of the invader. Tall annual willowherb (Epilobium brachycarpum) is a relatively recent and rapidly spreading neophyte in Europe that was first detected in 1978. Populations of tall annual willowherb from Germany and northern France were analysed by AFLP fingerprinting together with samples from five different localities in its native range in western North America. Three genetically different groups were found corresponding to different altitude zones in the native range. The F_ST is high among all samples indicating a strong genetical separation of the three groups. Invasive populations showed much lower genetic diversity than the native population. Additionally invasive populations revealed genetic affinities to North American specimens originating particularly from high mountain areas. The two large German populations and the population from northern France are genetically distinct while the individuals within the populations are genetically uniform. This suggests multiple introduction events rather than one introduction with consequent spreading across Europe. A third small German population from Treis-Karden in the Mosel valley clusters with North American lowland populations but suffers from frost damage and its permanent establishment is doubtful.     

Nucleotide and translated amino acid sequences of cDNA coding for the variable regions of the light and heavy chains of mouse hybridoma antibodies to blood group A and B substances

This is the first report of nucleotide and translated amino acid sequences of the variable region light (VL) and heavy (VH) chains of mouse monoclonal hybridoma anti-blood group A and B substances, the combining sites of which have been mapped. Monoclonal hybridoma anti-A and anti-B produced in BALB/c mice by immunization with A or B blood group substances, with A1 erythrocytes, and water-soluble blood group A substance or with synthetic B determinants coupled to bovine serum albumin or to O erythrocytes have been characterized immunochemically. To relate the immunochemical properties of the monoclonals to their primary structures, we have cloned and sequenced cDNAs of variable regions of light and heavy chains of two anti-A and two anti-B. The anti-A hybridomas have very similar combining site specificities and have almost identical VH sequences belonging to the J558 germ-line family, but their VL are from different germ-line VK gene families. The two anti-B hybridomas have different combining site specificities and use the same VL which differs completely from the anti-A VL; their VH are derived from different VH germ-line genes belonging to the J606 family. The results suggest that the heavy chains play a major role in determining the specificities of the antibody combining sites, with only minor contribution of VL. Additional sequence data on monoclonal antibodies of defined specificity for blood group substances are needed for further insights into the genetic and structural basis for their specificities.     

Typing of core and backbone domains of mucin-type oligosaccharides from human ovarian-cyst glycoproteins by 500-MHz 1H-NMR spectroscopy

Human blood-group A active glycoproteins from ovarian-cyst fluid were subjected to Smith degradation and subsequent beta-elimination. The resulting oligosaccharide-alditols represent the core and backbone domains of the O-linked carbohydrate chains. Nine of these, ranging in size from disaccharides to hexasaccharides, were investigated by 1H-NMR spectroscopy. Their primary structures could be adequately characterized. In particular, the core types, i.e. the substitution patterns of N-acetylgalactosaminitol (GalNAc-ol) as well as the types of backbone, i.e. the linkage types of alternating Gal-GlcNAc sequences, were unambiguously identified. The core type GlcNAc beta(1-3)GalNAc-ol is described for the first time as occurring in ovarian-cyst glycoprotein.     

Genetic Structure of Rauscher Spleen Focus-Forming Virus

Rauscher spleen focus-forming virus contains functional gag and pol genes and a partially deleted env gene which is structurally related to the env genes of dual tropic murine leukemia viruses.