Suppressors of cdc25p overexpression identify two pathways that influence the G2/M checkpoint in fission yeast

Checkpoints maintain the order of cell-cycle events. At G2/M, a checkpoint blocks mitosis in response to damaged or unreplicated DNA. There are significant differences in the checkpoint responses to damaged DNA and unreplicated DNA, although many of the same genes are involved in both responses. To identify new genes that function specifically in the DNA replication checkpoint pathway, we searched for high-copy suppressors of overproducer of Cdc25p (OPcdc25(+)), which lacks a DNA replication checkpoint. Two classes of suppressors were isolated. One class includes a new gene encoding a putative DEAD box helicase, suppressor of uncontrolled mitosis (sum3(+)). This gene negatively regulates the cell-cycle response to stress when overexpressed and restores the checkpoint response by a mechanism that is independent of Cdc2p tyrosine phosphorylation. The second class includes chk1(+) and the two Schizosaccharomyces pombe 14-3-3 genes, rad24(+) and rad25(+), which appear to suppress the checkpoint defect by inhibiting Cdc25p. We show that rad24Delta mutants are defective in the checkpoint response to the DNA replication inhibitor hydroxyurea at 37 degrees and that cds1Delta rad24Delta mutants, like cds1Delta chk1Delta mutants, are entirely checkpoint deficient at 29 degrees. These results suggest that chk1(+) and rad24(+) may function redundantly with cds1(+) in the checkpoint response to unreplicated DNA.     

Pollutant transport during a regional O3-episode in the mid-Atlantic states

Ozone (O3) concentrations in the Baltimore-Washington (B-W) metropolitan area frequently exceed the National Ambient Air Quality Standard (NAAQS) in the summer months. The most extreme O3 events occur in multi-day high O3 episodes. These events can be regional in scale, with O3 concentrations exceeding the NAAQS at numerous locations along the eastern U.S. seaboard, and are typically associated with slow-moving or stagnant high pressure systems. In the B-W region, the most extreme events typically occur with surface high pressure overhead or just west of the region and an upper air high-pressure area (ridge) to the west or northwest. Besides providing conditions conductive to local O3 production (subsidence and strong low-level inversions, weak horizontal winds, little cloud cover), this weather pattern may also result in transport of O3 and its precursors from heavily industrialized areas west and north of the B-W region. In this paper, observations and back trajectories made during the severe regional O3 event of July 12-15, 1995, are used to confirm the hypothesis that significant regional-scale transport of O3 and its precursors occur during extreme O3 events of the standard type in the B-W area.     

Thermal noise and bit error rate limits in nanoscale memories

Analysis of the effects of thermal noise in nanoscale memories is presented. A theoretical analysis of thermal noise is used to predict the number of bit errors per year caused by thermal noise.     

Peer and parental influences on male adolescent drinking

Using data from males aged 16-19 in Buffalo, NY, the present study examines two social mechanisms by which parents and peers influence adolescent drinking--behavioral and attitudinal transmission--and compares the patterns of behavioral and attitudinal transmission for parents and for peers. The study also assesses the relative importance of parents and peers in accounting for adolescent alcohol behavior. The findings indicate that both alcohol behavior and attitudes of parents and peers are significant predictors of adolescent drinking. However, the prediction patterns are reversed. Parental attitudes are more important than parental alcohol behavior, while peer alcohol behavior is more important than peer attitudes. Overall, peers have more influence on adolescent drinking than parents. There is a significant interaction of parental alcohol-related attitudes and age, which indicates that parental alcohol-related attitudes exert a greater effect on younger (i.e., age 16-17) males' alcohol use.     

Impact of multiple antenatal doses of betamethasone on growth and development of mice offspring

OBJECTIVE: Our purpose was to determine in a randomized, placebo-controlled manner whether multiple antenatal doses of betamethasone affect long-term growth and development of exposed mouse offspring. STUDY DESIGN: Sixty pregnant CD-1 mice received either two, four, or eight antepartum doses of 0.1 mg betamethasone or placebo. Perinatal outcomes, growth, and development of the offspring were compared in a blinded manner. Variables were compared by analysis of variance or chi 2 testing. RESULTS: Betamethasone-exposed subjects gained less weight during pregnancy and were delivered of fewer live pups, with fewer male survivors and lower birth weights. These trends were dose related. Growth measurements were similar after the neonatal period. No differences in functional development and physical maturation in the offspring were noted. The reproductive capability, perinatal outcomes, and growth and development of the second-generation offspring were unaffected by betamethasone exposure. CONCLUSION: Multiple antenatal dosings of betamethasone, reaching toxic levels, did not have an impact on the long-term growth and development of the surviving mouse offspring.     

Structure, subunit topology, and actin-binding activity of the Arp2/3 complex from Acanthamoeba

The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actin-related proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of approximately 13 x 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 microM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actin-rich regions of Acanthamoeba.     

Tilidine does not affect human sphincter of Oddi motility--a randomized, controlled study

AIM: To investigate the effects of intravenous pentazocine and tilidine on sphincter of Oddi motility. METHODS: Twenty patients with suspected sphincter of Oddi dysfunction were enrolled in a prospective, double-blind study. Sphincter of Oddi motility was assessed by means of endoscopic manometry after injection of 0.9% saline, as well as after randomized dosing with either 30 mg pentazocine i.v. (n = 10) or 50 mg tilidine i.v. (n = 10). RESULTS: Pentazocine significantly increased the sphincter of Oddi baseline pressure from 32 +/- 21 mmHg (saline) to 41 +/- 19 mmHg (P = 0.002), whereas tilidine did not alter the sphincter baseline pressure (34 +/- 15 mmHg saline vs. 36 +/- 16 mmHg tilidine, P = 0.16). Furthermore, pentazocine increased the phasic sphincter contraction amplitude (108 +/- 16 mmHg saline vs. 121 +/- 18 mmHg pentazocine, P = 0.004), but tilidine was without any effect (125 +/- 24 mmHg saline vs. 125 +/- 21 mmHg tilidine, P = 0.93). The phasic sphincter of Oddi contraction frequency and duration were not influenced either by pentazocine or by tilidine. CONCLUSION: In contrast to 30 mg of pentazocine, 50 mg of tilidine does not affect sphincter of Oddi motility. Therefore, tilidine can be used during endoscopic manometry and for analgesia in pancreatobiliary disease.     

Post-hoc Rasch analysis of optimal categorization of an ordered-response scale

The purpose of this study was to determine the optimal categorization of a self-efficacy ordered-response scale using the Rasch analysis and compare the performance of the Rasch statistics and parameter estimates with conventional statistics. A 50-item scale to measure psychomotor self-efficacy was administered to a total of 2,022 children, including 1,009 boys and 1,013 girls. The data analysis started by collapsing the original five adjacent categories into two, three, and four categories, and a total of 14 data sets were derived. Each of these data sets, including the original one, was analyzed using the Rasch rating scale model, and a set of Rasch model-data fit, category, and separation statistics and parameter estimates, as well as three conventional statistics, were computed and compared. It was found that, instead of the five-category construct designed, the best order of category meanings of the scale in respondents' perceptions was a three-category construct. The Rasch threshold estimates were sensitive indexes in determining the order of the categorization, and that item separation statistics were useful in determining the optimal categorization after its order was confirmed. The commonly used coefficient alpha was found not helpful at all in determining the optimal categorization. The Rasch analysis was demonstrated to be a useful post-hoc analytic approach in determining the optimal categorization of an ordered-response scale.     

Assessment of cerebral blood flow and CO2 reactivity after controlled cortical impact by perfusion magnetic resonance imaging using arterial spin-labeling in rats

We measured CBF and CO2 reactivity after traumatic brain injury (TBI) produced by controlled cortical impact (CCI) using magnetic resonance imaging (MRI) and spin-labeled carotid artery water protons as an endogenous tracer. Fourteen Sprague-Dawley rats divided into TBI (CCI; 4.02 +/- 0.14 m/s velocity; 2.5 mm deformation), sham, and control groups were studied 24 hours after TBI or surgery. Perfusion maps were generated during normocarbia (Paco2 30 to 40 mm Hg) and hypocarbia (PaCO2 15 to 25 mm Hg). During normocarbia, CBF was reduced within a cortical region of interest (ROI, injured versus contralateral) after TBI (200 +/- 82 versus 296 +/- 65 mL.100 g-1.min-1, P < 0.05). Within a contusion-enriched ROI, CBF was reduced after TBI (142 +/- 73 versus 280 +/- 64 mL.100 g-1.min-1, P < 0.05). Cerebral blood flow in the sham group was modestly reduced (212 +/- 112 versus 262 +/- 118 mL.100 g-1.min-1, P < 0.05). Also, TBI widened the distribution of CBF in injured and contralateral cortex. Hypocarbia reduced cortical CBF in control (48%), sham (45%), and TBI rats (48%) versus normocarbia, P < 0.05. In the contusion-enriched ROI, only controls showed a significant reduction in CBF, suggesting blunted CO2 reactivity in the sham and TBI group. CO2 reactivity was reduced in the sham (13%) and TBI (30%) groups within the cortical ROI (versus contralateral cortex). These values were increased twofold within the contusion-enriched ROI but were not statistically significant. After TBI, hypocarbia narrowed the CBF distribution in the injured cortex. We conclude that perfusion MRI using arterial spin-labeling is feasible for the serial, noninvasive measurement of CBF and CO2 reactivity in rats.