Measurements of Strong-Interaction Effects in Kaonic-Helium Isotopes at Sub-eV Precision with X-Ray Microcalorimeters.

We have measured the 3d→2p transition x rays of kaonic ^{3}He and ^{4}He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We determined the energies to be 6224.5±0.4(stat)±0.2(syst) eV and 6463.7±0.3(stat)±0.1(syst) eV, and widths to be 2.5±1.0(stat)±0.4(syst) eV and 1.0±0.6(stat)±0.3(stat) eV, for kaonic ^{3}He and ^{4}He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.

Rb plays a role in survival of Abl-dependent human tumor cells as a downstream effector of Abl tyrosine kinase.

The retinoblastoma (Rb) gene product is a tumor suppressor that is mutated or inactivated in many types of human cancers. Although Rb is known to be an upstream negative regulator of Abl protein tyrosine kinase, we propose here that Rb also functions as a downstream effector of Abl that plays a positive role in survival of Abl-dependent human tumor cells, including Bcr/Abl-positive chronic myelogenous leukemia (CML). We show that Rb is constitutively phosphorylated at tyrosine in Abl-dependent tumor cells, and that Abl phosphorylates Rb specifically at Y805 within the C-terminal domain of the molecule. We also show that ectopic expression of Rb induces apoptosis in Abl-dependent tumor cells by inhibiting the Abl tyrosine kinase activity, and that Rb-induced apoptosis is compromised by Abl-catalysed phosphorylation of Rb at Y805. Furthermore, the silencing of endogenous Rb by RNA interference induced apoptosis in Abl-dependent tumor cells. Thus, our findings suggest that Abl-catalysed tyrosine phosphorylation of Rb is necessary for survival of Abl-dependent human tumor cells, and raises the possibility that this phosphorylated Rb can be a molecular target for cancer therapy aimed at inducing apoptosis of Abl-dependent tumor cells, such as Bcr/Abl-positive CML.

Differential scanning calorimetric study of the effect of intercalators and other kinds of DNA-binding drugs on the stepwise melting of plasmid DNA.

The effect of intercalating drugs (the anthracycline group of antibiotics, ethidium bromide, actinomycin D) on stepwise melting of DNA was studied by differential scanning calorimetry (DSC). The DSC DNA melting profile of plasmid pJL3-TB5 DNA (5277 base-pairs in length) consists of seven peaks, and all the intercalators caused shifting of these peaks, particularly those formed at the high temperature ranges, to the higher temperature ranges in a characteristic manner depending upon the binding strength of the drug. The analysis of the anthracycline group of antibiotics, such as aclacinomycin A, daunomycin, adriamycin and pyrarubicin, indicates that the difference in binding is due to the sugar moiety at position O-7 of the chromophore in these antibiotics. Analysis on the basis of the helix-coil transition theory suggests that the anthracycline group of antibiotics interact preferentially with the 5'-CG-3' sequences. The effect of various DNA-binding drugs other than intercalators on stepwise melting of DNA was then studied by DSC. The representative drugs examined were distamycin A, peplomycin, cis-dichlorodiamine-platinum(II) (cis-DDP or cis-Platin) and mitomycin C, which differ in their mode of interaction with DNA; namely, minor groove binding, strand cleavage and intrastrand or interstrand cross-linking. Distamycin A caused shifting of the DSC peaks at the low temperature ranges to a higher temperature range, whereas peplomycin and cis-DDP caused shifting of all the DSC peaks to form a broad peak at a lower temperature range, suggesting that the DSC DNA melting profiles are affected in a characteristic manner depending upon the interaction mode of the drug.

Development of a new inhibitor of glucosylceramide synthase.

Analogs of the potent inhibitor of glucosylceramide (GlcCer) synthase, D-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (P4), based on substitutions in the palmitoyl group were made by means of a stereo-selective synthetic method in order to elucidate the role of the hydrophobic portion in both the inhibitory action toward the enzyme and the biological effects. While P4 strongly inhibited GlcCer synthase with an IC(50) of 0.5 microM in vitro, it also inhibited cell growth by 50% at the concentration of 7 microM. The shorter N-acyl chain analogs including decanoyl, octanoyl, and hexanoyl groups showed similar IC(50) values for GlcCer synthase (around 2 microM) but the hexanoyl analog exhibited only a slight inhibitory effect on cell growth, showing the dissociation between GlcCer depletion and cell growth. Several compounds which exhibit similar hydrophobicity to the hexanoyl analog of P4 were subsequently designed. We found that D-threo-1-phenyl-2-benzyloxycarbonylamino-3-pyrrolidino-1-pr opanol (PBPP) was a most potent inhibitor, showing an IC50 of 0.3 microM. In cultured cells, PBPP was able to deplete glycosphingolipids without affecting cell growth or the ceramide level.

A craniocervical injury-induced syringomyelia caused by central canal dilation secondary to acquired tonsillar herniation. Case report.

The authors report on a 19-year-old man with an acquired tonsillar herniation caused by a craniocervical junction injury in which serial magnetic resonance (MR) images demonstrated patent and isolated segments of the central canal participating in the dilation and then formation of a cervical syrinx. The patient was involved in a motor vehicle accident; he developed tonsillar herniation as a complication of subarachnoid and epidural hemorrhage, predominantly observed around the cisterna magna and upper cervical canal. Repeated MR images obtained over an 11-month period indicated the for mation and acute enlargement of the syrinx. Ten months after the accident, the patient presented with sensory disturbance in both upper extremities and spasticity due to syringomyelia. He underwent craniocervical decompressive surgery and doraplasty, which reduced the size of syringomyelia. The authors postulate that the patent central canal may play a role in determining the location of a syrinx remote from a focus of cerebrospinal fluid obstruction.

Intraparenchymal meningioma in an infant--case report.

A 1-year and 10-month-old girl presented with an intraparenchymal meningioma in the left frontal lobe manifesting as grand-mal seizures. Computed tomography and magnetic resonance images revealed a round, well-demarcated mass in the left frontal lobe which was homogeneously enhanced. Angiography showed the feeding arteries of the tumor from the middle cerebral artery. The preoperative diagnosis was an intraaxial tumor. At operation, the lesion was totally embedded in the frontal lobe without any connection to the overlying dura or the ventricular system. Some small feeders from the middle cerebral artery were coagulated and the tumor was totally removed. The histological diagnosis was fibroblastic meningioma. Her postoperative course was uneventful. She was doing well 2 years after surgery. Intraparenchymal meningiomas may be seen more frequently than expected in children. Absence of dural attachment is characteristic of pediatric meningiomas.

New turbidimetric device for measuring cell concentrations in thick microbial suspensions.

A photoelectric turbidimeter is described for use in measuring cell concentrations in thick suspensions. Its sample cuvette provides a path length continuously adjustable between 0.01 and 20.00 mm. By reducing the path length, it is possible to measure the optical density in thick cell suspensions without dilution. Moreover, the method described is rapid and simple, and only small amounts (less than 1 ml) of cell suspensions are required. The method is applicable to cell concentrations ranging up to 10(9)/ml for yeast.

Resistance of Pseudomonas aeruginosa to cefsulodin: modification of penicillin-binding protein 3 and mapping of its chromosomal gene.

Spontaneous cefsulodin-resistant mutants of Pseudomonas aeruginosa PAO4089 were isolated on agar impregnated with 3 mg/l of cefsulodin. This strain does not produce any chromosomal beta-lactamase. The MICs of cefsulodin for the parent and its mutants were 0.78 and 12.5 mg/l, respectively. Complete cross-resistance between cefsulodin and seven other antipseudomonal beta-lactams was noted in the mutants. The mutant gene, designated as pbpB, was mapped by FP5 plasmid-mediated conjugation and found to be near to cys-59 on the PAO chromosome, the gene order being pur-67, oruI, pbpB and cys-59. There were no detectable differences between the parent and its mutants in their outer membrane protein profiles. Penicillin-binding protein assay, by the competition method, with cefsulodin or carbenicillin showed a significant reduction in affinity of PBP3 for these beta-lactams. This PBP is the primary target for cefsulodin in P. aeruginosa. The genetic mechanism by which the cefsulodin-resistant clinical isolates of P. aeruginosa have emerged is discussed.

Physical properties of cell water in partially dried Saccharomyces cerevisiae.

The equilibrium vapor pressure, the heat of vaporization, the dielectric increment, and the NMR spectra of partially dried cells were studied in Saccharomyces cerevisiae with water contents varying in the range from 25 to 0.8%. The comparative study of those physical properties suggests that physical states of the microbe can be classified into four regions in accordance with the states of the cell water: the solution region, the gel region, the mobile adsorption region, and the localized water region. Much difference in the physiological properties is found between the cells in the solution region and those in the gel region, whereas the pattern changes in physical properties take place when the cells in the gel region are dried to a further extent into the mobile or the localized region. The various modes in the molecular motion of the cell water reflected in those physical properties of the cell seem to give some insight into the biological functions of the molecule in the native as well as the dried states of the cell.

Structure of a covalently cross-linked form of core histones present in the starfish sperm.

The post-translational modification of core histones plays an essential role in chromatin remodeling processes. We recently reported the occurrence of a novel histone modification, involving a epsilon-(gamma-glutamyl)lysine cross-link between a glutamine residue of histone H2B and a lysine residue of histone H4 in the testis of the starfish, Asterina pectinifera[Shimizu, T., Hozumi, K., Horiike, S., Nunomura, K., Ikegami, S., Takao, T., and Shimonishi, Y. (1996) Nature 380, 32]. In order to determine the complete structure of the modified histone heterodimer, p28 from both testis and sperm was purified. p28 was digested with Achromobacter lyticus protease I or Staphylococcus aureus V8 protease to give proteolytic fragments that were separated by HPLC. Amino acid analysis, sequencing, and mass spectrometric analysis of the fragments showed that the amino acid sequences of these fragments are identical to those of both histones H2B and H4, except for two NH2-terminal peptides obtained by digestion with A. lyticus protease I. One of the peptides, K8, was identical to that reported previously, and the other was a here-to-fore unidentified peptide, which was designated K10. Amino acid and positive-ion FAB-MS/MS analyses of K10 showed that it to be a fragment, derived from Gly8-Lys10 of histone H2B and Gly9-Lys16 of histone H4. The yields of K8 and K10 were calculated to be 47 and 42%, respectively, expressed as the percent of the total amount of p28 used in the experiment. Based on these data, the structure of p28 was determined to be a heterodimer, composed of histones H2B and H4, formed through a transglutaminase-catalyzed acyl transfer reaction between Gln9 of histone H2B and Lys5 or Lys12 of histone H4.

A Novel Modification of the Lysine Residue at Position 12 of Histone H4 in Starfish Sperm.

Post-translational modification of core histones is essential in processes requiring chromatin remodeling. We report here a novel modification in histones of the sperm of the starfish, Asterina pectinifera, which involves an ε-(γ-glutamyl)lysine cross-link between the glutamine residue at position 9 of histone H2B and the lysine residue at position 12 of histone H4.