minibrain: a new protein kinase family involved in postembryonic neurogenesis in Drosophila

The development of the adult central nervous system of Drosophila requires a precise and reproducible pattern of neuroblast proliferation during postembryonic neurogenesis. We show here that mutations in the minibrain (mnb) gene cause an abnormal spacing of neuroblasts in the outer proliferation center (opc) of larval brain, with the implication that mnb opc neuroblasts produce less neuronal progeny than do wild type. As a consequence, the adult mnb brain exhibits a specific and marked size reduction of the optic lobes and central brain hemispheres. The insufficient number of distinct neurons in mnb brains is correlated with specific abnormalities in visual and olfactory behavior. The mnb gene encodes a novel, cell type-specific serine-threonine protein kinase family that is expressed and required in distinct neuroblast proliferation centers during postembryonic neurogenesis. The mnb kinases share extensive sequence similarities with kinases involved in the regulation of cell division.

Epidemiologically closely related viruses from hemophilia B patients display high homology in two hypervariable regions of the HIV-1 env gene

The diversity of human immunodeficiency virus type 1 (HIV-1) is mainly caused by mutations that affect the gene encoding the gp120 envelope protein. Isolates differ to a large extent in the hypervariable regions of gp120. This study was undertaken to determine the degree of variation of HIV-1 env genes isolated from seven individuals with hemophilia B who became infected in association with administration of a suspected clotting factor lot. Two hypervariable regions and part of a constant region from proviral DNA of the peripheral blood leukocytes of these patients were amplified and the products of the polymerase chain reactions were sequenced. The sequences derived from five of the individuals displayed 100% sequence homology, 1 had two and 1 had six deviations from the consensus sequence. The alignment of the amino acid sequence so deduced revealed no comparable homology to any of these two hypervariable regions from a number of published isolates. The genetic variability of HIV-1 seems to be limited, at least in the early phase of infection, allowing the determination of close relationships between epidemiologically related strains.

Comparison of different methods for detecting human immune deficiency virus in human immunodeficiency virus-seropositive hemophiliacs

Since the detection of antibodies against the human immune deficiency virus (HIV) does not definitely prove HIV infection in hemophiliacs, virus detection was attempted by virus isolation from the peripheral blood monocytes (PBL), by demonstration of p24 antigen and decline of p24 antibody, and by detection of viral DNA by the polymerase chain reaction (PCR). Virus isolation was optimized by immediate coculture of PBL and by replacement of the reverse transcriptase test by the p24 antigen test, whereas the elimination of CD8+ lymphocytes proved to be unnecessary. Virus detection was dependent on the clinical stage of the illness. Virus isolation in 70 of 211 patients (33%) was more sensitive than detection of p24 antigen or decline of p24 antibody. PCR was performed in 25 patients and indicated infection in all of 15 isolation-positive cases and in 6 of 10 patients from whom virus was not isolated. Changes from negative to positive virus culture and from a weakly fusiogenic to a highly fusiogenic isolate were often accompanied by a progression of the disease. The results suggest that reactivation of HIV occurs when immune deficiency has become manifest. Apparently virus isolation detects only the virus already reactivated in vivo, whereas the PCR may also detect latent virus.

Structure of the voltage-dependent potassium channel is highly conserved from Drosophila to vertebrate central nervous systems

Voltage-sensitive potassium channels are found in vertebrate and invertebrate central nervous systems. We have isolated a rat brain cDNA by cross-hybridization with a probe of the Drosophila Shaker gene complex. Structural conservation of domains of the deduced protein indicate that the rat brain cDNA encodes a voltage-sensitive potassium channel. Of the deduced amino acid sequence, 82% is homologous to the Drosophila Shaker protein indicating that voltage-sensitive potassium channels have been highly conserved during evolution. Selective pressure was highest on sequences facing the intracellular side and on proposed transmembrane segments S4-S6, suggesting that these domains are crucial for voltage-dependent potassium channel function. The corresponding rat mRNA apparently belongs to a family of mRNA molecules which are preferentially expressed in the central nervous system.

Immunoglobulin biosynthesis in myeloma-associated and casein- and endotoxin-induced murine amyloidosis

Amyloidosis was induced in C57BL mice by daily injections of casein and in BALB/c mice by daily injections of endotoxin. There was no obvious disorder of immunoglobulin biosynthesis by spleen lymphocytes in these mice either before, during the development of, or in the amyloidotic stage. The pattern of immunoglobulin synthesis, assembly, and secretion was unaltered, the relative amount of heavy and light chains produced was normal, and there was an absence of immunoglobulin polypeptide chain fragments. Small amounts of amyloid were present in only 1 of 19 BALB/c and C3H mice (the IgG2a producing MOPC 173 tumor) bearing immunoglobulin-producing myeloma tumors and variants of these tumors. There was no relationship between excess light chain production by tumor plasma cells or spleen lymphocytes and the development of amyloidosis and there were no light chain fragments demonstrable. Antiserum prepared against casein-induced amyloid cross-reacted by immunofluorescence with the amyloid present in the MOPC 173 tumor-bearing mice, indicating the presence of common antigenic determinants in these two forms of amyloid. Attempts to study the biosynthesis of amyloid with incorporation of radioactively labeled amino acids were unsucessful.