Comparative analyses of human immunodeficiency virus type 1 (HIV-1) and HIV-2 Vif mutants.

Virion infectivity factor (vif), a gene found in all lentiviruses, plays an essential role in virus replication in certain target cells. We examined the replication competence of the human immunodeficiency virus type 2 (HIV-2) vif mutant in different T-cell lines and primary cells in comparison with that of the HIV-1 vif mutant. Both mutant viruses were unable to replicate in peripheral blood-derived mononuclear cells but replicated with wild-type efficiency in certain T-cell lines, such as SupT1 and MOLT-4/8. These results confirm the importance of vif in the infection of relevant target cells and imply that some cellular factor(s) could compensate for vif function. However, HIV-1 and HIV-2 vif mutant viruses also show differential replications in other cell lines, suggesting either different threshold requirements for the same cellular factor(s) or the involvement of different factors to compensate for vif-1 and vif-2 functions. By cross complementation experiments, we showed that vif-1 and vif-2 have similar functions. Our studies further indicate the existence of two kinds of nonpermissive cells: H9 is unable to complement HIV-1 delta vif but is susceptible to a one-round infection with HIV-1 delta vif produced from permissive cells. In contrast, U937 is nonpermissive for HIV-2 delta vif produced from permissive cells but, once infected, is able to complement the delta vif function. In both types of nonpermissive cells, a step prior to proviral DNA synthesis is affected.     

Immunofluorescence microscopic demonstration of vimentin filaments in asteroid bodies of sarcoidosis. A comparison with electron microscopic findings

Asteroid bodies in multinucleate giant cells from sarcoid granulomas were investigated by immunofluorescence and electron microscopy. The following points have been established: 1. Asteroid bodies are made up of individual components of the so-called cytoskeleton, predominantly vimentin filaments. Microtubules are involved in smaller amounts in the formation of the asteroid bodies. 2. They arise within the area of the cytosphere. The body of the asteroid includes the centrioles while the arms of the asteroid usually extend into the Golgi area and occasionally up to the cell nuclei. 3. Asteroid bodies result from aggregation of the flexible filamentous and microtubular systems of the centrosphere. The processes of aggregation probably result from local fluid shifts and sol-gel transformations. 4. The stellate form of the aggregations is determined by the preexistent radial arrangement of the elements of the cytosphere. 5. The prevailing specific environment of the underlying granulomatous disease, together with the internal characteristics of the structure and function of the giant cells, in particular in states of exhaustion may play a part in their development.     

Five novel locations of Neocentromeres in human: 18q22.1, Xq27.1∼27.2, Acro p13, Acro p12, and heterochromatin of unknown origin

Since the first report in 1993, an ectopic centromere, i.e. neocentromere formation, has been reported in more than 100 small supernumerary marker chromosomes (sSMC), in 7 instances of centromere repositioning, and in about a dozen cases with more complex chromosomal rearrangements. Here we report 2 new cases with centromere repositioning and 3 neocentric sSMC consisting exclusively of heterochromatic material. Yet, no centromere formation was reported for the regions 18q22.1 and Xq27.1～27.2 as it was observed in the 2 cases with centromere repositioning here; in both cases, cytogenetically an inversion was suggested. Two of the 3 neocentric sSMC were derived from a short arm of an acrocentric chromosome. The remainder neocentric sSMC case was previously reported and was stainable only by material derived from itself.     

Parameter estimation for discretely observed linear birth‐and‐death processes

Birth‐and‐death processes are widely used to model the development of biological populations. Although they are relatively simple models, their parameters can be challenging to estimate, as the likelihood can become numerically unstable when data arise from the most common sampling schemes, such as annual population censuses. A further difficulty arises when the discrete observations are not equi‐spaced, for example, when census data are unavailable for some years. We present two approaches to estimating the birth, death, and growth rates of a discretely observed linear birth‐and‐death process: via an embedded Galton‐Watson process and by maximizing a saddlepoint approximation to the likelihood. We study asymptotic properties of the estimators, compare them on numerical examples, and apply the methodology to data on monitored populations.     

Seasonal prevalence and intensity of follicular atresia in Baltic cod Gadus morhua callarias L.

In the present study, 307 ovaries of eastern Baltic cod Gadus morhua callarias sampled during the prespawning and spawning season 2000 were analysed histologically to estimate the seasonal prevalence and intensity of atresia. The number of atretic oocytes per ovary was estimated using a combination of the physical disector method and volume fraction (Delesse principle). Atretic oocytes were observed in 32% of the ovaries. Prevalence of atresia was independent of female size, but increased significantly with declining female condition from prespawning and through the spawning stages. The relative intensity of atresia, i.e. number of atretic oocytes in relation to normally developed vitellogenic oocytes, was low amounting to 1·4% on average. Similar to prevalence, relative intensity of atresia differed significantly between maturity stages and increased with decreasing female condition. The population egg loss due to atresia amounted to 4·6% indicating that Baltic cod was performing close to maximum productivity, i.e. potential egg production.     

Large-conductance calcium-activated potassium channel activity is absent in human and mouse neutrophils and is not required for innate immunity

Large-conductance Ca²⁺-activated K⁺ (BK) channels are reported to be essential for NADPH oxidase-dependent microbial killing and innate immunity in leukocytes. Using human peripheral blood and mouse bone marrow neutrophils, pharmacological targeting, and BK channel gene-deficient (BK^–/–) mice, we stimulated NADPH oxidase activity with 12-O-tetradecanoylphorbol-13-acetate (PMA) and performed patch-clamp recordings on isolated neutrophils. Although PMA stimulated NADPH oxidase activity as assessed by O₂^– and H₂O₂ production, our patch-clamp experiments failed to show PMA-activated BK channel currents in neutrophils. In our studies, PMA induced slowly activating currents, which were insensitive to the BK channel inhibitor iberiotoxin. Instead, the currents were blocked by Zn²⁺, which indicates activation of proton channel currents. BK channels are gated by elevated intracellular Ca²⁺ and membrane depolarization. We did not observe BK channel currents, even during extreme depolarization to +140 mV and after elevation of intracellular Ca²⁺ by N-formyl-L-methionyl-L-leucyl-phenylalanine. As a control, we examined BK channel currents in cerebral and tibial artery smooth muscle cells, which showed characteristic BK channel current pharmacology. Iberiotoxin did not block killing of Staphylococcus aureus or Candida albicans. Moreover, we addressed the role of BK channels in a systemic S. aureus and Yersinia enterocolitica mouse infection model. After 3 and 5 days of infection, we found no differences in the number of bacteria in spleen and kidney between BK^–/– and BK^+/+ mice. In conclusion, our experiments failed to identify functional BK channels in neutrophils. We therefore conclude that BK channels are not essential for innate immunity. killing assay; reactive oxygen species; BK-deficient mice; mice infection     

Role of the fusogenic peptide sequence in syncytium induction and infectivity of human immunodeficiency virus type 2.

Syncytium induction is a characteristic feature of infection by human immunodeficiency virus (HIV) in vitro. The hydrophobic amino terminus of the transmembrane glycoprotein of HIV type 1 is an essential determinant of virus entry into the target cell population and the formation of syncytia in cell culture. To define the role of the HIV type 2 fusion peptide during infection and syncytium formation, we introduced 8 amino acid substitutions into the hydrophobic amino terminus of gp41, changing either the hydrophobicity, the charge, or the polarity of the amino acid. Viruses containing the envelope mutations were analyzed for their syncytium-inducing capacities, levels of infectivity, and envelope processing and expression. Mutations that increased the hydrophobic nature of the fusion peptide increased syncytium formation, whereas mutations which increased the charge and the polarity and/or decreased the hydrophobicity of the fusion domain severely reduced the capacity of the virus to induce syncytia. However, viruses severely compromised for syncytium formation exhibit only slightly lower levels of infectivity.