The unique headpore of Monospilus dispar (Cladocera,Chydoridae) is not lonesome: new record of minute lateral pores

The headshield of Monospilus dispar (Cladocera, Chydoridae, Aloninae) was characterized by the presence of a unique headpore. Scanning Electron Microscopy shows the occurrence of minute pores close to the main headpore. The intimate structure of the main headpore is formed by concentric lamellae. This new information leads to new considerations about phylogeny.     

Primary sequence and functional expression of a novel ouabain-resistant Na,K-ATPase. The beta subunit modulates potassium activation of the Na,K-pump.

In order to understand the molecular mechanism of ouabain resistance in the toad Bufo marinus, Na,K-ATPase alpha and beta subunits have been cloned and their functional properties tested in the Xenopus laevis oocyte expression system. According to sequence comparison between species, alpha 1, beta 1, and beta 3 isoforms were identified in a clonal toad urinary bladder cell line (TBM 18-23). The sequence of the alpha 1 isoform is characterized by two positively charged amino acids (Arg, Lys) at the N-terminal border of the H1-H2 extracellular loop and no charged amino acid at the C terminus, a pattern distinct from the ouabain-resistant rat alpha 1 isoform. The coexpression of alpha 1 beta 1 or alpha 1 beta 3 TBM subunits in the Xenopus oocyte resulted in the expression of identical maximum Na,K-pump currents with identical inhibition constant for ouabain (Ki) (alpha 1 beta 1: 53 +/- 3 microM; n = 7 vs. alpha 1 beta 3: 57 +/- 3.0 microM; n = 8) but distinct potassium half activation constant (K1/2) (alpha 1 beta 1: 0.87 +/- 0.08 mM, n = 16; alpha 1 beta 3: 1.29 +/- 0.07 mM, n = 17; p less than 0.005). We conclude that (i) the TBM alpha 1 isoform is necessary and sufficient to confer the ouabain resistant phenotype; (ii) the beta 3 or beta 1 subunit can associate with the alpha 1 equally well without affecting the ouabain-resistant phenotype; (iii) some specific sequence of the beta subunit can modulate the activation of the Na,K-pump by extracellular potassium ions.     

Inhibition of glycosylphosphatidylinositol anchor formation by mannosamine.

Many eucaryotic cell surface proteins are anchored to the plasma membrane via a glycosylphosphatidylinositol (GPI), of which the core region is highly conserved from protozoa to mammalian cells. Previous studies (Lisanti, M. P., Field, M. C., Caras, I. W., Menon, A. K., and Rodiguez-Boulan, E. (1991) EMBO J. 10, 1969-1977) showed that mannosamine blocked the expression of a recombinant GPI-anchored protein in Madin-Darby canine kidney cells and converted this protein to an unpolarized secretory product. In the present study, we examined the effect of mannosamine on the formation of the glycan portion of the GPI anchor precursors. This amino sugar inhibited the incorporation of mannose into the glycan portion, and the inhibition was dose-dependent. Mannosamine was shown to be incorporated into the glycan as mannosamine, probably mostly in the second mannose position and thereby to block the further addition of mannose and other anchor components. The products formed in the presence of this drug were characterized by gel filtration and high resolution TLC both before and after deamination with nitrous acid and dephosphorylation by HF. Galactosamine and trehalosamine were inactive in this system, whereas glucosamine also inhibited mannose incorporation into GPI intermediates.     

Filarial infection of the breast. Report of a case with diagnosis by fine needle aspiration cytology.

The breast is not a frequent site of filarial infection. We report a case of fine needle aspiration cytologic diagnosis of filariasis of the breast, not previously reported.     

The effect of infra-red radiation on rectal temperature and respiration rate of unacclimated female new zealand white rabbits

1. 1.|An experiment was carried out to examine the effects of various levels of infra-red (i.r.) radiation on rectal temperature (RT) and respiration rate (RR) in New Zealand While rabbits.

2. 2.|A 4 × 3 × 6 factorial design was employed in which the factors were: four intensities of i.r. radiant heating of 0.0, 1.9, 2.1 and 2.4 MJ/m²/h, three replicates and six rabbits.

3. 3.|rectal temperature differed (P < 0.05) between treatments and were highest at the “high” level of i.r. radiation (1°C higher than for controls). At the “medium” and “low” levels of i.r. heating RTs were respectively 0.3 and 0.2°C higher than in controls.

4. 4.|At different levels of radiation RR were different (P < 0.05), with the highest (422.7 ± 218.1 breaths/min) at 2.4 MJ/m²/h i.r. radiant heating. This RR was almost 2.5 times that in controls, while at the “low” and “medium” i.r. levels RR values were respectively 1.5 and 2 times those of controls.

Associations of Escherichia coli K-12 OmpF trimers with rough and smooth lipopolysaccharides.

The associations of both rough and smooth lipopolysaccharides (LPS) with the OmpF porin of Escherichia coli K-12 were examined in galE strains deleted for ompC. Transformation with pSS37 and growth with galactose conferred the ability to assemble a Shigella dysenteriae O antigen onto the core oligosaccharide of E. coli K-12 LPS. The association of LPS with OmpF trimers was assessed by staining, autoradiography of LPS specifically labeled with [1-14C]galactose, and Western immunoblotting with a monoclonal antibody specific for OmpF trimers. These techniques revealed that the migration distances and multiple banding patterns of OmpF porin trimers in sodium dodecyl sulfate-polyacrylamide gels were dictated by the chemotype of associated LPS. Expression of smooth LPS caused almost all of the trimeric OmpF to run in gels with a slower mobility than trimers from rough strains. The LPS associated with trimers from a smooth strain differed from the bulk-phase LPS by consisting almost exclusively of molecules with O antigen.     

Chemical dependency and drug testing in the workplace.

Urine testing for drug use in the workplace is now widespread, with the prevalence of positive drug tests in the work force being 0% to 15%. The prevalence of marijuana use is highest, and this can be reliably tested. Though it is prudent to rid the workplace of drug use, there is little scientific study on the relationship of drug use and workplace outcomes, such as productivity and safety. Probable-cause testing and preemployment testing are the most common applications. Random testing has been less accepted owing to its higher costs, unresolved legal issues, and predictably poor test reliability. Legal issues have focused on the right to policy, discrimination, and the lack of due process. The legal cornerstone of a good program is a policy that is planned and agreed on by both labor and management, which serves both as a contract and as a procedure in which expectations and consequences are known. The National Institute on Drug Abuse is certifying laboratories doing employee drug testing. Testing methods when done correctly are less prone to error than in the past, but screening tests can be defeated by adulterants. Although the incidence of false-positive results is low, such tests are less reliable when the prevalence of drug abuse is also low.     

Dynamic changes of microtubule and actin structures in CV-1 cells during electrofusion

To study the involvement of the cytoskeletal system in the fusion of animal cells, we examined the dynamic changes of cytoskeletal proteins during the various stages of cell fusion. CV-1 cells were fused by applying a radio-frequency electrical pulse. Structural changes of microtubules (MTs) and F-actin were monitored simultaneously by double-label fluorescence microscopy. It was observed that in a few minutes after the initiation of cell fusion, MT bundles began to extend into the cytoplasmic bridges which were formed by fusing the membranes of neighboring cells. Later, a network of parallel MT bundles appeared between the adjacent nuclei of the fusing cells; such MT bundles may provide the mechanical links that are responsible for nuclear aggregation. The structural changes of F-actin during cell fusion were more complicated. We observed many different patterns of actin distribution in the fusing cells, including some giant, ring-shaped structures. Reorganization of actin is unlikely to be involved in the nuclear aggregation process. Instead, actin bundles condensed at the cell edges may help to widen the cytoplasmic bridges to allow merging of cellular contents between the fusing cells.     

Effects of spaceflight on the proliferation of jejunal mucosal cells

The mitotic indices, villus heights, and crypt depths were determined in each of three jejunal regions (proximal, middle, and distal) for five animals each in the flight, vivarium, and synchronous groups. Because of the rapid turnover of intestinal mucosal cells and the delay in recovering the flight animals, it is not known whether the proliferation of jejunal mucosal cells is affected by microgravity conditions associated with spaceflight. However, since there were no consistent differences between animals in the flight group and those in the synchronous and vivarium control groups, it appears that any effects of microgravity on the turnover of jejunal mucosal cells are short-lived. Thus, this study represents an initial step in determining the effects of microgravity on the proliferation and turnover of intestinal mucosal cells.