Induction of Haploid Callus from Isolated Microspores of Peony in vitro

The in vitro culture of isolated microspores of two cultivarsof Paeonia, P. lactiflora cv. "Kumoinotsuru" (2n=10) and cv."Toyonoakari" (2n = 10), was attempted. With both cultivars,some cultured microspores (3–6%) began to divide afterfive to seven days of culture. Those of "Kumoinotsuru" grewinto calli, whereas the others degenerated. Cytological examinationof the callus developed from a microspore revealed haploids,diploids or a mixture of both. No direct embryo formation frommicrospores was observed in this experiment. (Received December 1, 1980; Accepted January 16, 1981)     

Hydrocephalus in suckling rats infected intracerebrally with mouse hepatitis virus, MHV-A59

After intracerebral inoculation of mouse hepatitis virus, MHV-A59 strain, into 3- to 5-day-old Wistar rats, some survivors at 14 days postinoculation (p.i.) were found to lack the cerebral cortex and to have an accumulation of considerable amount of cerebrospinal fluid. The virus titer in the brain increased exponentially after inoculation, reaching a maximum 4 to 6 days p.i. when immunofluorescence revealed virus-specific antigen within neurons in the cerebral cortex. A small amount of infectious virus was also detectable 14 days p.i. when the cerebral anomaly was evident. This brain malformation causing hydrocephalus was due to cerebral damage by viral infection.     

Differences between surface antigenic determinants of polar monotrichous flagella of Vibrio parahaemolyticus and of related species

Polar monotrichous flagella (M-flagella) of Vibrio parahaemolyticus have antigens in common with those of various species of Vibrio including V. cholerae and V. anguillarum, and of Beneckea, revealed by gel diffusion tests with flagelli monomers. However, antiserum against M-flagellin of V. parahaemolyticus did not agglutinate cells of V. cholerae and V. anguillarum, although it did agglutinate cells of V. parahaemolyticus. Agglutination tests after absorption of the antiserum with purified M-flagellar filaments or flagellin monomers and H-agglutination inhibition tests demonstrated that there are two different antigenic determinants in M-flagella as in lateral flagella. One is on the surface of the M-flagella (surface antigenic determinant, SA) and disappears or is buried in dissociated monomers. The other is inside the flagella (internal antigenic determinant, IA) and is exposed when the flagella are dissociated to flagellin monomers. SA of V. parahaemolyticus is different from those of V. cholerae and V. anguillarum, whereas the three species have a common IA.     

Studies on the effects of vinblastine and colchicine on Trypanosoma gambiense

Vinblastine and colchicine induce the anucleate form of Trypanosoma gambiense. Light microscopic studies indicated that the anucleate form was not always produced as a result of inhibition of nuclear duplication, but was formed as a result of delay or inhibition of separation of the two nuclei after completion of nuclear division. Studies showed that vinblastine and colchicine caused disorder in arrangement of axonemal microtubules of the extracellular flagella and increased formation of both protofilaments and the axoneme composed of protofilaments in trypanosomes. Moreover, treatment with colchicine resulted in disintegration of previously existing pellicular microtubules and formation of cytoplasmic projections that appeared as protrusions from a small part of the surface membrane.     

MCPIP1 ribonuclease antagonizes dicer and terminates microRNA biogenesis through precursor microRNA degradation

MicroRNAs (miRNAs) are versatile regulators of gene expression and undergo complex maturation processes. However, the mechanism(s) stabilizing or reducing these small RNAs remains poorly understood. Here we identify mammalian immune regulator MCPIP1 (Zc3h12a) ribonuclease as a broad suppressor of miRNA activity and biogenesis, which counteracts Dicer, a central ribonuclease in miRNA processing. MCPIP1 suppresses miRNA biosynthesis via cleavage of the terminal loops of precursor miRNAs (pre-miRNAs). MCPIP1 also carries a vertebrate-specific oligomerization domain important for pre-miRNA recognition, indicating its recent evolution. Furthermore, we observed potential antagonism between MCPIP1 and Dicer function in human cancer and found a regulatory role of MCPIP1 in the signaling axis comprising miR-155 and its target c-Maf. These results collectively suggest that the balance between processing and destroying ribonucleases modulates miRNA biogenesis and potentially affects pathological miRNA dysregulation. The presence of this abortive processing machinery and diversity of MCPIP1-related genes may imply a dynamic evolutional transition of the RNA silencing system.     

Dietary supplementation with docosahexaenoic acid,but not with eicosapentaenoic acid,reduces host resistance to fungal infection in mice

The effect of dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on host resistance to Paracoccidioides brasiliensis infection was investigated. Mice fed palm oil supplemented with DHA showed reduced antifungal activity in the spleen and liver, as compared with mice fed palm oil or soybean oil without supplementation with DHA. Mice fed DHA-supplemented soybean oil also showed reduced antifungal activity in the liver, but the extent of reduction was less profound. This reduction in antifungal activity was not observed with EPA-supplemented palm or EPA-supplemented soybean oil. These results suggest that two factors, DHA and palm oil in combination, are involved in reducing the host resistance. DHA-enriched palm oil was also responsible for an increase in DHA concentration and a marked decrease in arachidonic acid content in the spleen and liver. However, this group did not show elevated spleen and liver phospholipid hydroperoxide levels compared with the other groups, excluding the possibility that the reduction in antifungal activity observed with DHA-enriched palm oil is due to acceleration of in vivo lipid peroxidation. Greater infection-induced increases in spleen and serum interferon-gamma concentrations were observed in mice fed DHA-enriched palm oil compared with the other groups.     

Direct evidence for the interaction between papaverine and alpha 2-adrenergic receptors in canine platelets

The effects of papaverine on specific [3H]-yohimbine binding to canine platelet alpha 2-adrenergic receptors and on the platelet aggregation were assessed and compared with those of verapamil. Both compounds concentration-dependently inhibited [3H]-yohimbine binding with KI values for respective compounds of 0.39 +/- 0.05 microM (n = 3) and 15 +/- 0.19 microM (n = 3). In the presence of either compound KD values in Scatchard analysis of the equilibrium ligand binding increased in concentration-dependent manner, whereas Bmax did not change, indicating competitive inhibition of the ligand binding by these compounds. (-)-Epinephrine (3 microM) potentiation of adenosine diphosphate (ADP, 0.1 microM) aggregation was inhibited by papaverine with IC50 of 11 +/- 3.6 microM (n = 4). In the same experiments verapamil inhibited the platelet aggregation with lower IC50 (3.1 +/- 0.87 microM, n = 4) in comparison with that for papaverine. These results suggest that papaverine, like verapamil, inhibits physiological response of canine platelets through alpha-adrenergic receptor stimulation by direct interaction with the receptors.     

Comparison of the inhibitory effects of mexiletine and lidocaine on the calcium current of single ventricular cells

Effects of mexiletine and lidocaine on inward calcium current (ICa) of single ventricular myocytes from guinea pigs were studied using tight seal whole cell clamp method. Mexiletine at the concentrations of 10, 30 and 100 microM decreased ICa by 23.0, 28.9 and 55.4%, respectively, while lidocaine decreased it by 8.9, 16.8 and 25.2%. At all concentrations tested, a potency for ICa inhibition in mexiletine was significantly greater than that in lidocaine (p less than 0.05). The results suggest that mexiletine has, at therapeutic concentrations, a considerable blocking action on the Ca channels other than well-known action on the Na channels.     

Glycosylation affects translocation of integrin, Src, and caveolin into or out of GEM

Endogenous GM3 synthesis and full N-glycosylation in membrane receptors occurred in "4-epimerase-less" ldlD (Krieger's CHO mutant) cells cultured in Gal-containing medium, whereby components of detergent-insoluble, low-density, buoyant membrane fraction, termed "glycolipid-enriched microdomain (GEM)," varied significantly by translocation into or out of GEM. Integrins alpha3 and alpha5 were translocated into GEM in the presence of 0.5 or 0.25% Triton X-100, particularly in the absence of Gal, whereby integrins are underglycosylated and GlcCer is the major glycolipid component in GEM. Src family kinase was translocated into and enriched in GEM fractions when prepared in 0.5 or 0.25% Triton X-100 from cells grown in Gal-containing medium, whereby GM3 synthesis is induced. In contrast, caveolin is highly enriched in GEM when GM3 synthesis does not occur, and is translocated into high-density membrane fraction when GM3 synthesis occurs. The results suggest that levels of key molecules controlling cell adhesion and signaling are defined by translocation into or out of GEM, which depends on glycosylation state.     

Enantioselectivity of bunitrolol 4‐hydroxylation is reversed by the change of an amino acid residue from valine to methionine at position 374 of cytochrome P450‐2D6

The enantioselectivity of 4‐hydroxylation of bunitrolol (BTL), a β‐adrenoceptor blocking drug, was studied in microsomes from human liver, human hepatoma (Hep G2) cells expressing CYP2D6, and lymphoblastoid cells expressing CYP2D6. Kinetics in human liver microsomes showed that the Vmax value for (+)‐BTL was 2.1‐fold that of (−)‐BTL, and that the Km value for (+)‐BTL was lower than that for the (−)‐antipode, resulting in the intrinsic clearance (Vmax/Km) of (+)‐BTL being 2.1‐fold over its (−)‐antipode. CYP2D6 (CYP2D6‐met) expressed in Hep G2 cells had a methionine residue at position 373 of the amino acid sequence and a rat‐type N‐terminal peptide (MELLNGTGLWSM) instead of the human‐type (MGLEALVPLAVIV), and showed enantioselectivity of [(+)‐BTL < (−)‐BTL] for the rate of BTL 4‐hydroxylation. In contrast, enantioselectivity [(+)‐BTL > (−)‐BTL] for Hep G2‐CYP2D6 (CYP2D6‐val) with a human‐type N‐terminal peptide that had a valine residue at 374, which corresponds to the methionine of the CYP2D6‐met variant, was the same as that for human liver microsomes. We further confirmed that CYP2D6‐met and CYP2D6‐val expressed in human lymphoblastoid cells, both of which have methionine and valine, respectively, at position 374 and a human‐type N‐terminal peptide, exhibited the same enantioselectivities as those obtained from CYP2D6‐met and CYP2D6‐val expressed in the Hep G2 cell system. These results indicate that the amino acid at 374 of CYP2D6 is one of the key factors influencing the enantioselectivity of BTL 4‐hydroxylation. Chirality 11:1–9, 1999. © 1999 Wiley‐Liss, Inc.