Heterochromatin protein HP1Hsβ(p25β) and its localization with centromeres in mitosis

Some autoimmune sera containing anticentromere autoantibodies also recognize a doublet of Mr 23 000 (p23) and 25 000 (p25) in addition to CENP (centromere protein)-A (Mr 19 000), -B (Mr 80 000), and -C (Mr 140 000). A p25 antigen (HP1^Hsα) has been shown to be a human homolog of Drosophila HP1 (heterochromatin protein 1). We have isolated a cDNA clone encoding another form of p25 (HP1^Hsβor p25β) from a λZap HepG2 library using human autoimmune serum. The deduced amino acid sequence of the clone contained a conserved chromodomain (chromatin modifier domain) in the N-terminal region and a heterochromatin binding domain in the C-terminal region. In immunofluorescence experiments, only affinity purified antibodies reactive with the C-terminal (amino acids 70–185) domain showed nucleoplasmic and heterochromatin staining, whereas N-terminal (amino acids 1–115) specific antibodies were nonreactive. In metaphase chromosome spreads, the C-terminal domain antibody was also localized to the centromeric regions of chromosomes. Association with centromeres was most prominent at anaphase and changed to a more generalized association with whole chromosomes in telophase. The cooccurrence of autoantibodies to centromere proteins and HP1 in certain autoimmune diseases might be a reflection of coordinated immune responses to these closely associated sets of proteins. Received: 8 August 1996; in revised form: 4 December 1996 / Accepted: 17 December 1996     

Grazing impact of microzooplankton on a diatom bloom in a mesocosm as estimated by pigment-specific dilution technique

To investigate the impact of microzooplankton grazing on phytoplankton bloom in coastal waters, an enclosure experiment was conducted in Saanich Inlet, Canada during the summer of 1996. Daily changes in the microzooplankton grazing rate on each phytoplankton group were investigated with the growth rates of each phytoplankton group from the beginning toward the end of bloom using the dilution technique with high-performance liquid chromatography (HPLC). On Day 1 when nitrate and iron were artificially added, chlorophyll a concentration was relatively low (4.3 μg l⁻¹) and 19′-hexanoyloxyfucoxanthin-containing prymnesiophytes were predominant in the chlorophyll biomass. However, both the synthetic rates and concentrations of 19′-hexanoyloxyfucoxanthin declined before bloom, suggesting that 19′-hexanoyloxyfucoxanthin-containing prymnesiophytes weakened. Chlorophyll a concentration peaked at 23 μg l⁻¹ on Day 4 and the bloom consisted of the small chain-forming diatoms Chaetoceros spp. (4 μm in cell diameter). Diatoms were secondary constituents in the chlorophyll biomass at the beginning of the experiment, and the growth rates of diatoms (fucoxanthin) were consistently high (>0.5 d⁻¹) until Day 3. Microzooplankton grazing rates on each phytoplankton group remarkably increased except on alloxanthin-containing cryptophytes after the nutrient enrichments, and peaked with >0.6 d⁻¹ on Day 3, indicating that >45% of the standing stock of each phytoplankton group was removed per day. Both the growth and mortality rates of alloxanthin-containing cryptophytes were relatively high (>1 and >0.5 d⁻¹, respectively) until the bloom, suggesting that a homeostatic mechanism might exist between predators and their prey. Overall, microzooplankton grazing showed a rapid response to the increase in phytoplankton abundance after the nutrient enrichments, and affected the magnitude of the bloom significantly. High grazing activity of microzooplankton contributed to an increase in the abundance of heterotrophic dinoflagellates with 7-24 μm in cell size, the fraction of large-sized (>10 μm) chlorophyll a, and stimulated the growth of larger-sized ciliates after the bloom.     

Differences in the release of cholesterol from taurocholate versus taurochenodeoxycholate micellar solutions

The maximal micellar solubility, distribution and apparent monomer activity of cholesterol in taurine-conjugated cholate and chenodeoxycholate micellar solutions were studied to clarify the different modulating effect of these bile salt species on cholesterol uptake in an intestinal lumen. The maximal micellar solubility was significantly greater in taurochenodeoxycholate. The intermicellar cholesterol monomer concentration was not significantly different between the two kinds of micellar solution. However, the apparent cholesterol monomer activity determined using an artificial organic phase (polyethylene disc) was significantly higher in taurocholate than that in taurochenodeoxycholate. A linear relationship between the intermicellar cholesterol concentration and the apparent cholesterol monomer activity was found, with the slope depending upon the bile salt species. It is concluded that the difference in partitioning of cholesterol from taurocholate and taurochenodeoxycholate micelles into a fixed organic phase may contribute in part to the different regulating effects of these bile salts on the uptake of cholesterol in the intraluminal phase.     

Ionic processes underlying the decrease in osmotic potential of Chara L-cell fragments in dilute electrolyte solutions

Movements of ions are considered to be governed by the electroneutrality rule. Therefore, a cation moving across the cell membrane into the cell either passively or actively should move together with its counterion, an anion, in equal amounts of charge or in exchange for another cation inside the cell. This means that the net influx of the cation in question should be affected by the permeability of its counterion and/or another cation inside the cell. To examine osmotic and ionic regulation in Chara cells, cell fragments of Chara having a lower osmotic pressure than normal (L-cell fragments) were prepared. The L-cell fragments were individually put into various dilute electrolyte solutions and their osmotic potentials were measured with a turgor balance. Concentrations of K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^?, NO^?₃. and SO^2?₄. in the external electrolyte solutions in which L-cells had been incubated were also analysed by ion chromatography. The results showed that in 0.5 mM KCL + 0.1 mM CaCl₂ solution, Chara L-cell fragments absorbed K⁺ and Cl^? to maintain electroneutrality and then regained their osmotic potential very rapidly. When the anion was Cl, the cation absorbed at the highest rate was K⁺ On the other hand, when the cation was K, the anion absorbed at the highest rate was Cl, Other ions Ca²⁺, SO^2?₄ and NO^?₃ showed much less permeability than K⁺ and Cl ^?for the Chara plasma membrane. The conclusion from these findings was that due to the constraint of electroneutral transport, the uptake rate of a salt into L-cells is limited by the permeability of the least permeable ion.     

Locations of crossover breakpoints within the CMT1A-REP repeat in Japanese patients with CMT1A and HNPP

We have used human β2 and β4 cDNA probes to map the genes encoding two isoforms of the regulatory β subunit of voltage-activated Ca²⁺ channels, viz. CACNB2 (β2) and CACNB4 (β4), to human chromosomes 10p12 and 2q22-q23, respectively, by fluorescence in situ hybridization. The gene encoding the β2 protein, first described as a Lambert-Eaton myasthenic syndrome (LEMS) antigen in humans, is found close to a region that undergoes chromosome rearrangements in small cell lung cancer, which occurs in association with LEMS. CACNB2 (β2) and CACNB4 (β4) genes are members of the ion-channel gene superfamily and it should now be possible to examine their loci by linkage analysis of ion-channel-related disorders. To date, no such disease-related gene has been assigned to 10p12 and 2q22-q23. Received: 5 February 1997 / Accepted: 4 April 1997     

Induction of Manganese Superoxide Dismutase by Cytokines and Lipopolysaccharide in Cultured Mouse Astrocytes

Abstract: To determine whether cytokines or lipopolysaccharide (LPS) are involved in the induction of superoxide dismutase (SOD) in the nervous system, we examined the effects of these substances on the levels of SOD in cultured mouse astrocytes. Treatment of astrocytes with 10² to 10⁴ U/ml tumor necrosis factor-α for 3 days increased the levels of Mn SOD in a dose- and time-dependent manner to as much as six times the level under nontreated conditions. Treatment with 1.0 µg/ml LPS for 3 days elicited a fourfold increase in levels of Mn SOD, and the effect of LPS was also dose dependent. Furthermore, Mn SOD in astrocytes was induced by a 3-day exposure to interleukin-1α at concentrations of 10² or 10³ U/ml. However, these stimuli had no effect on levels of copper-zinc SOD (Cu/Zn SOD) in astrocytes. By contrast, interferon-γ did not change the levels of either Mn or Cu/Zn SOD in the cells. The results indicate that the selective induction of Mn SOD by cytokines and LPS, which has been observed in nonnervous tissues, may also occur in nervous tissues. The induction of Mn SOD may represent a mechanism for protection of cells from oxidative stress.     

Diurnal K+ and Anion Transport in Phaseolus Pulvinus

Diurnal movement of Phaseolus leaf is caused by deformationof the laminar pulvinus located at the joint of the leaf bladeand the petiole. The plants were cultured in solutions withvarious ion compositions, and changes of K⁺, Na⁺, Ca²⁺, Mg²⁺,Cl^–, NO₃– and P₁ concentrations both in the upperand lower parts of the laminar pulvinus were measured. Culturein 10 mM KCl solution caused an increase in K⁺ and Cl^–concentrations both in the upper and lower parts without anysignificant change in the concentration of NO₃^–; culturein 10 mM KNO₃ solution caused an increase in K⁺ and NO₃^–concentration without any significant change in the concentrationof Cl^–; and culture in 10 mM KH₂PO₄ solution caused anincrease in K⁺ and P₁ concentrations without any significantchange in the concentrations of NO₃- and Cl^–. K⁺ moved from the upper to lower parts or from the lower toupper parts diurnally in all plants cultured in any solutionmentioned above. The main inorganic anion that accompanied thisK⁺ movement was Cl^– in KCl solution, and NO₃^– inKNO₃ solution. When the seedlings were cultured in distilledwater or in KH₂PO₄ solution, neither Cl^– NO₃^– norP₁ accompanied this K⁺ movement. In these cases, mainly H⁺ and/ororganic anions are supposed to move in exchange for and/or incombination with K⁺ movement. (Received November 8, 1982; Accepted June 13, 1983)     

Influence of External Osmotic Pressure on Water Permeability and Electrical Conductance of Chara Cell Membrane

Water permeability of the plasma membrane of a Characean internodalcell decreased with an increase in the osmotic pressure of theoutside of the cell, suggesting that the equivalent pore radiusof the water-filled pores becomes smaller with an increase inthe osmotic pressure. In contrast, the apparent membrane resistancedid not increase with an increase in the external osmotic pressure.These facts suggest that ions pass through the membrane mainlyvia pores other than those for bulk water flow. (Received October 22, 1986; Accepted May 22, 1987)     

Clinical usefulness of urine-based enzyme-linked immunosorbent assay for detection of antibody to Helicobacter pylori: a collaborative study in nine medical institutions in Japan

Background. A urine-based enzyme-linked immunosorbent assay (ELISA) kit for detection of antibody to Helicobacter pylori has been developed in Japan. Urine samples can be obtained noninvasively and are easier and safer to handle than are serum samples. The aim of this study was to examine the clinical usefulness of this urine-based ELISA kit.
Materials and Methods. A pair of random, single-void urine and serum samples was collected from each of 1,061 subjects, including 238 patients with gastroduodenal disease. The sensitivity and specificity of the urine-based ELISA was compared with those of three commercially available serum-based ELISA kits. For those patients with gastroduodenal disease, the urine- and serum-based ELISA results were also compared with those for other diagnostic methods using endoscopic biopsy specimens, such as culture, histology, and rapid urease tests.
Results. Based on the three serum-based ELISA results, the sensitivity, specificity, and accuracy of the urine-based ELISA were 97.7%, 95.6%, and 96.8%, respectively. On the basis of the biopsy test results, the sensitivity (96.2%), specificity (78.9%), and accuracy (91.0%) of the urine-based ELISA were almost equivalent or superior to all three serum-based ELISAs tested. In addition, 10 of the 12 false-positive cases for urine-based ELISA were confirmed to be true positives for antibodies to H. pylori by Western blot analysis and inhibition ELISA.
Conclusions. The urine-based ELISA (URINELISA H. pylori Antibody) is very accurate and should be useful as an alternative to serum-based ELISAs for screening of H. pylori infection.     

Computational analysis of full-length mouse cDNAs compared with human genome sequences

Although the sequencing of the human genome is complete, identification of encoded genes and determination of their structures remain a major challenge. In this report, we introduce a method that effectively uses full-length mouse cDNAs to complement efforts in carrying out these difficult tasks. A total of 61,227 RIKEN mouse cDNAs (21,076 full-length and 40,151 EST sequences containing certain redundancies) were aligned with the draft human sequences. We found 35,141 non-redundant genomic regions that showed a significant alignment with the mouse cDNAs. We analyzed the structures and compositional properties of the regions detected by the full-length cDNAs, including cross-species comparisons, and noted a systematic bias of GENSCAN against exons of small size and/or low GC-content. Of the cDNAs locating the 35,141 genomic regions, 3,217 did not match any sequences of the known human genes or ESTs. Among those 3,217 cDNAs, 1,141 did not show any significant similarity to any protein sequence in the GenBank non-redundant protein database and thus are candidates for novel genes. Received: 18 January 2001 / Accepted: 17 May 2001