Virus transmission through compromised synthetic barriers: part I--effect of unsteady driving pressures

Although synthetic membranes such as gloves, condoms, and instrument sheaths are used in environments with highly time-varying stresses, their effectiveness as barriers to virus transmission is almost always tested under static conditions. In this paper it is shown how a previously developed mathematical model can be used to transform information from static barrier tests into predictions for more realistic use conditions. Using a rate constant measured for herpes adsorption to latex in saline, and an oscillatory trans-membrane pressure representative of coitus, the amount of virus transmitted through a hole (2 microm diameter) in a condom is computed. Just beyond the exit orifice of the pore, transport is dominated by the rapidly dissipating viscous jet of virus suspension, which results in an accumulation of viruses roughly 20 pore radii from the barrier surface during each cycle. Due to virus adsorption to the barrier surfaces, the simulations reveal a gradual decrease in virus flow with increasing number of cycles, and thus a slow divergence from predictions based upon steady-state conditions. Still, over the 500 cycles simulated, steady-state predictions approximate the net number of viruses transmitted to within 25 percent error.

Virus transmission through compromised synthetic barriers: part II--influence of pore geometry

When stressed during normal use, synthetic barriers such as gloves and condoms can develop tears that are undetectable by the user. It is of considerable public-health importance to estimate the quantity of virus transmitted through the tear, in the event of viral contamination of the fluid medium. A mathematical model that accounts for virus adsorption to the barrier material was used to compute the quantity of virus transmitted through defects of various geometries. Slits were modeled as cylinders of elliptic cross section, and upper and lower bounds for the transmission rate of HIV and Hepatitis B virus (HBV) were calculated for barrier-use scenarios such as coitus and gripping of surgical instruments. For a 1-microm high slit, HIV transmission was found to be negligible for all likely use scenarios. HIV transmission became potentially significant for a 5-microm slit. Due to its high titer, HBV transmitted at potentially important levels even through the 1-microm slit. The dependence of the transmission rate upon pore aspect ratio was determined and found to be very strong for high-adsorption situations and near-circular pores. Numerical predictions of virus transport through a laser-drilled hole in a condom matched experimental measurements well, even when the tapered nature of the geometry is ignored.

Diverse developmental programs of Xenopus laevis metamorphosis are inhibited by a dominant negative thyroid hormone receptor

Metamorphosis of anuran tadpoles is controlled by thyroid hormone (TH). Here we demonstrate that transgenic Xenopus laevis tadpoles expressing a dominant negative form of TH receptor-alpha are resistant to a wide variety of the metamorphic changes induced by TH. This result confirms that TH receptors mediate both early and late developmental programs of metamorphosis as diverse as growth in the brain, limb buds, nose and Meckel's cartilage, remodeling of the intestine, and death and resorption of the gills and tail.

Nosocomial infections due to Acinetobacter baumannii in a neurosurgery ICU

Invasive infections caused by Acinetobacter baumannii in a post-operative neurosurgery ICU were studied. Sixty one patients admitted during a span of 11 months were culture positive for acinetobacter species from blood and/or CSF samples. They were followed up prospectively for evidence of infection and clinical outcome. 40 cases had clinical evidence of infection due to acinetobacter species while in 21 patients, the isolation of the organism was considered a contaminant. Acinetobacter baumannii was the most common organism associated with invasive infections. Respiratory tract was found to be the most common primary source of infection in patients with bacteraemia or meningitis. The age, sex and pre-operative hospital stay were not significantly different in the two groups (p>0.05), while post-operative hospital stay and mortality was significantly higher in patients with invasive infection (p<0.05). Acinetobacter baumannii was isolated from multiple sites (p<0.05) and repeatedly from the same site (p<0.001) in a significantly higher number of patients with invasive infections. Mortality was high in the patients infected with Acinetobacter baumannii. Even amongst the infected group, the patient shaving meningitis showed a higher mortality as compared to the patients having bacteraemia.

Optimization of solvation models for predicting the structure of surface loops in proteins

A novel procedure for optimizing the atomic solvation parameters (ASPs) sigma(i) developed recently for cyclic peptides is extended to surface loops in proteins. The loop is free to move, whereas the protein template is held fixed in its X-ray structure. The energy is E(tot) = E(FF)(epsilon = nr) + summation operator sigma(i)A(i), where E(FF)(epsilon = nr) is the force-field energy of the loop-loop and loop-template interactions, epsilon = nr is a distance-dependent dielectric constant, and n is an additional parameter to be optimized. A(i) is the solvent-accessible surface area of atom i. The optimal sigma(i) and n are those for which the loop structure with the global minimum of E(tot)(n, sigma(i)) becomes the experimental X-ray structure. Thus, the ASPs depend on the force field and are optimized in the protein environment, unlike commonly used ASPs such as those of Wesson and Eisenberg (Protein Sci 1992;1:227-235). The latter are based on the free energy of transfer of small molecules from the gas phase to water and have been traditionally combined with various force fields without further calibration. We found that for loops the all-atom AMBER force field performed better than OPLS and CHARMM22. Two sets of ASPs [based on AMBER (n = 2)], optimized independently for loops 64-71 and 89-97 of ribonuclease A, were similar and thus enabled the definition of a best-fit set. All these ASPs were negative (hydrophilic), including those for carbon. Very good (i.e., small) root-mean-square-deviation values from the X-ray loop structure were obtained with the three sets of ASPs, suggesting that the best-fit set would be transferable to loops in other proteins as well. The structure of loop 13-24 is relatively stretched and was insensitive to the effect of the ASPs.

Cytogenetic toxicity of vincristine

The anticancer drugs vincristine sulphate (VCR) and cyclophosphamide (CTX) were tested for their cytogenetic effects in the bone marrow cells of Swiss mice. The end points investigated were chromosomal aberrations and mitotic index at 24 hours posttreatment and micronuclei (MN) at 30 hours posttreatment in bone marrow cells of male and female mice after a single intraperitoneal exposure. The doses tested were VCR 0.25, 0.5, and 1.0 mg/kg and CTX 40 mg/kg b.w. of mice. Significant percentages of chromosomal aberrations and significant numbers of micronuclei per thousand polychromatic erythrocytes (PCEs) that were induced were recorded from bone marrow of each of the VCR-treated groups of mice. There were no significant differences between the percentages of dividing cells in the VCR-treated group and the vehicle control groups of mice. Peculiarly, in the chromosomal aberration study, the male mice were found to be more responsive to VCR than the females, and the aberrations per hundred metaphases were found to be decreased when the dose of VCR was increased. The percentage of dividing cells was also higher with the lowest dose of VCR tested. However, there was a dose-dependent, but nonlinear, increase in MN per thousand PCEs. The results were compared with the already available fragmentary and self-contradictory data on the genotoxicity of VCR in mice and in other mammalian test systems.

Evaluation of low back pain risks in a beef skinning operation

The low back pain risks in a beef skinning operation at a high stand kill floor workstation was evaluated. The increases in compressive forces at lower back (L5/S1) between normal slump (back angle 25 degrees, measured in the sagittal plane) and severe (45 degrees ) and between normal slump and very severe (70 degrees ) bent back postures were 387 N or 28% and 616 N or 45%, respectively. The high spine load coupled with high level of repetition can have a high probability of fatigue failure in the spine structural members. Non-neutral back posture for a large portion of the total work time can be a low back pain risk factor. The videotape analysis showed that the times involved during the task performance for the bent back (more than 25 degrees ) and severe bent back (more than 45 degrees ) were 48.4 and 33.5% of the total cycle time, respectively. The upper limit from OWAS (Ovako Working Posture Analysis System) for bent back posture is 30% of the total cycle time. The bent and twisted back posture (both more than 25 degrees ) time was 10.4% compared to OWAS limit of 5%. This indicated that actions are needed in the near future to alleviate the risk of low back pain. Ergonomics redesign of the workstation was recommended for the operation.

Killing of cutaneous microbial species by photodynamic therapy

BACKGROUND

Photodynamic therapy (PDT) utilizes photosensitizers and light. Whereas PDT use in cancer treatment has been widely accepted, antimicrobial PDT (APDT) is still in its early stages of development.

OBJECTIVES

To study microbial killing in vitro using APDT.

METHODS

We used a combination of methylene blue and visible light, and a range of microbial species representative of those encountered on the skin in health and disease. Using standard light intensity conditions (slide projector, 25 cm distance from target, 42 mW cm(-2)) and methylene blue dye at 100 microg mL(-1), kill rates and subsequent D-values were determined against Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, Corynebacterium minutissimum, Propionibacterium acnes and Candida albicans.

RESULTS

D-values for these species were 72, 66, 48, 120, 30 and 660 s, respectively. The effects of light intensity on the killing of S. epidermidis showed the kill rate to be proportional to the light intensity. A high rate of cell kill was also obtained using natural sunlight.

CONCLUSIONS

Overall, these results indicate that APDT of the skin may represent a useful alternative to conventional antimicrobial treatment.

Computer supported studies on design and evaluation of solid dispersions of carbamazepine

The main advantages of solid dispersions (the drug could be maintained in a bioavailable form, dosage reduction and cleaner manufacturing conditions) provide scope for the continued interest in field. Additionally, their use in providing a sustained or controlled release of drugs has only been tentatively examined. In the present study, Carbamazepine has been used to develop a dosage form which will provide a booster amount followed by sustained release of the drug for effective control of epileptic seizures while keeping the serum level of the drug at minimum. Enteric polymers CAP and CAT have been used to retard the release till the formulation reaches the intestine. Either individually or combined fractions of the formulations may be used in the therapy of epilepsy.

Computational fluid dynamic studies of leukocyte adhesion effects on non-Newtonian blood flow through microvessels

The study of the effect of leukocyte adhesion on blood flow in small vessels is of primary interest to understand the resistance changes in venular microcirculation. Available computational fluid dynamic studies provide information on the effect of leukocyte adhesion when blood is considered as a homogeneous Newtonian fluid. In the present work we aim to understand the effect of leukocyte adhesion on the non-Newtonian Casson fluid flow of blood in small venules; the Casson model represents the effect of red blood cell aggregation. In our model the blood vessel is considered as a circular cylinder and the leukocyte is considered as a truncated spherical protrusion in the inner side of the blood vessel. The cases of single leukocyte adhesion and leukocyte pairs in positions aligned along the same side, and opposite sides of the vessel wall are considered. The Casson fluid parameters are chosen for cat blood and human blood and comparisons are made for the effects of leukocyte adhesion in both species. Numerical simulations demonstrated that for a Casson fluid with hematocrit of 0.4 and flow rate Q = 0.072 nl/s, a single leukocyte increases flow resistance by 5% in a 32 microns diameter and 100 microns long vessel. For a smaller vessel of 18 microns, the flow resistance increases by 15%.

Maximum reach envelope for the seated and standing male and female for industrial workstation design

Maximum reach envelopes for the 5th, 50th and 95th percentile reach lengths of males and females in seated and standing work positions were determined. The use of a computerized potentiometric measurement system permitted functional reach measurement in 15 min for each subject. The measurement system captured reach endpoints in a dynamic mode while the subjects were describing their maximum reach envelopes. An unbiased estimate of the true reach distances was made through a systematic computerized data averaging process. The maximum reach envelope for the standing position was significantly (p<0.05) larger than the corresponding measure in the seated position for both the males and females. The average reach length of the female was 13.5% smaller than that for the corresponding male. Potential applications of this research include designs of industrial workstations, equipment, tools and products.

Multicopy molecular dynamics simulations suggest how to reconcile crystallographic and product formation data for camphor enantiomers bound to cytochrome P-450cam

Multiple ligand binding modes are possible in many enzyme active sites; their presence in cytochrome P450cam (P450cam) is evident from crystallographic studies of the binding of thiocamphor and phenylimidazoles. Here, we use multicopy molecular dynamics simulations to compare the binding modes of (1R)- and (1S)-camphor in the active site of P450cam. Simulations with (1R)-camphor, the natural substrate, serve to calibrate our protocol: 19 out of 20 copies of (1R)-camphor converged to coordinates very close to those observed for (1R)-camphor in its crystallographic complex with P450cam during the simulations. Simulations with the (1S)-camphor enantiomer showed greater mobility of the substrate, consistent with spectroscopic data, and resulted in 3 major binding modes. One of these is similar to the major conformation (of the two conformations assigned) in a recently determined crystal structure, but this conformation is not correctly oriented for regiospecific hydroxylation at C-5. The simulations, however, provide evidence for reorientation of (1S)-camphor upon formation of the reactive Fe-O intermediate to an orientation suitable for hydroxylation. The simulations thus permit rationalisation of the apparent inconsistency between the crystal structure and the reaction products.

Isometric pull and push strengths of paraplegics in the workspace: 1. Strength measurement profiles

The isometric strength profiles of male and female paraplegics were determined for pull and push strengths in the normal, maximum, and extreme working reach envelopes. A computerized isometric strength measurement system was designed and constructed for the purpose. The strongest pull location was at extreme reach vertically above the shoulder and the strength values for males and females were 473 and 318 newtons (N), respectively. The strongest push location was at maximum reach, at vertical (phi) angle of 45 degrees and at horizontal (theta) angle of 45 degrees for males and at 0 degrees for women and the strength values were 235 and 172 N, respectively. The nature of the strength profiles was found to be similar for both the sexes. The pull and push strengths of the female were 77 and 68% that of the male, respectively.

Isometric pull and push strengths of paraplegics in the workspace: 2. Statistical analysis of spatial factors

The effect of reach levels, horizontal angles, and vertical angles on isometric pull and push strengths of male and female was determined. Highly significant increases in men's push strength were found between extreme to maximum reaches, and from extreme to normal reaches. However, for women's push strength, a significant increase was found only between extreme to maximum reach. Significant or highly significant increases were found in men's and women's pull strength between the horizontal angle (theta) sagittal through the active shoulder (90 degrees ) and other angles (0, 45, and 135 degrees ). However, for men's push strength, highly significant increases were found between the horizontal angle 45 degrees from the frontal plane, and other angles. For women's push strength, significant or highly significant increases were found between the horizontal angles 0 degrees and angles of 90 and 135 degrees. For men's and women's pull strength, significant or highly significant increases were found between the vertical angle (phi), 90 degrees, and other angles (-20, 0, and 45 degrees ). Similar increases were found for women's push strength between the 45 degrees angle and other angles. In the design of a workstation for paraplegics that requires pull and push forces, consideration must be given to the spatial factors.

Cytochrome c methyltransferase, Ctm1p, of yeast

Cytochromes c from plants and fungi, but not higher animals, contain methylated lysine residues at specific positions, including for example, the trimethylated lysine at position 72 in iso-1-cytochrome c of the yeast Saccharomyces cerevisiae. Testing of 6,144 strains of S. cerevisiae, each overproducing a different open reading frame fused to glutathione S-transferase, previously revealed that YHR109w was associated with an activity that methylated horse cytochrome c. We show here that this open reading frame, denoted Ctm1p, is specifically responsible for trimethylating lysine 72 of iso-1-cytochrome c. Unmethylated forms of cytochrome c but not other proteins or nucleic acids are methylated in vitro by Ctm1p produced in S. cerevisiae or Escherichia coli. Iso-1-cytochrome c purified from a ctm1-Delta strain is not trimethylated in vivo, whereas the K72R mutant form, or the trimethylated Lys-72 form of iso-1-cytochrome c, are not significantly methylated by Ctm1p in vitro. Like apocytochrome c, but in contrast to holocytochrome c, Ctm lp is located in the cytosol, consistent with the view that the natural substrate is apocytochrome c. The ctm1-Delta strain lacking the methyltransferase did not exhibit any growth defect on a variety of media and growth conditions, and the unmethylated iso-1-cytochrome c was produced at the normal level and exhibited the normal activity in vivo. Ctm1p and cytochrome c were coordinately regulated during anaerobic to aerobic transition, a finding consistent with the view that this methyltransferase evolved to act on cytochrome c.

Control of intramolecular interactions between the pleckstrin homology and Dbl homology domains of Vav and Sos1 regulates Rac binding

Vav and Sos1 are Dbl family guanine nucleotide exchange factors, which activate Rho family GTPases in response to phosphatidylinositol 3-kinase products. A pleckstrin homology domain adjacent to the catalytic Dbl homology domain via an unknown mechanism mediates the effects of phosphoinositides on guanine nucleotide exchange activity. Here we tested the possibility that phosphatidylinositol 3-kinase substrates and products control an interaction between the pleckstrin homology domain and the Dbl homology domain, thereby explaining the inhibitory effects of phosphatidylinositol 3-kinase substrates and stimulatory effects of the products. Binding studies using isolated fragments of Vav and Sos indicate phosphatidylinositol 3-kinase substrate promotes the binding of the pleckstrin homology domain to the Dbl homology domain and blocks Rac binding to the DH domain, whereas phosphatidylinositol 3-kinase products disrupt the Dbl homology/pleckstrin homology interactions and permit Rac binding. Additionally, Lck phosphorylation of Vav, a known activating event, reduces the affinities between the Vav Dbl homology and pleckstrin homology domains and permits Rac binding. We also show Vav activation in cells, as monitored by phosphorylation of Vav, Vav association with phosphatidylinositol 3,4,5-trisphosphate, and Vav guanine nucleotide exchange activity, is blocked by the phosphatidylinositol 3-kinase inhibitor wortmannin. These results suggest the molecular mechanisms for activation of Vav and Sos1 require disruption of inhibitory intramolecular interactions involving the pleckstrin homology and Dbl homology domains.

The role of nuclear cap binding protein Cbc1p of yeast in mRNA termination and degradation

The cyc1-512 mutation in Saccharomyces cerevisiae causes a 90% reduction in the level of iso-1-cytochrome c because of the lack of a proper 3'-end-forming signal, resulting in low levels of eight aberrantly long cyc1-512 mRNAs which differ in length at their 3' termini. cyc1-512 can be suppressed by deletion of either of the nonessential genes CBC1 and CBC2, which encode the CBP80 and CBP20 subunits of the nuclear cap binding complex, respectively, or by deletion of the nonessential gene UPF1, which encodes a major component of the mRNA surveillance complex. The upf1-Delta deletion suppressed the cyc1-512 defect by diminishing degradation of the longer subset of cyc1-512 mRNAs, suggesting that downstream elements or structures occurred in the extended 3' region, similar to the downstream elements exposed by transcripts bearing premature nonsense mutations. On the other hand, suppression of cyc1-512 defects by cbc1-Delta occurred by two different mechanisms. The levels of the shorter cyc1-512 transcripts were enhanced in the cbc1-Delta mutants by promoting 3'-end formation at otherwise-weak sites, whereas the levels of the longer cyc1-512 transcripts, as well as of all mRNAs, were slightly enhanced by diminishing degradation. Furthermore, cbc1-Delta greatly suppressed the degradation of mRNAs and other phenotypes of a rat7-1 strain which is defective in mRNA export. We suggest that Cbc1p defines a novel degradation pathway that acts on mRNAs partially retained in nuclei.

Isolation and characterization of human breast adenocarcinoma cells made resistant to alpha-difluoromethylornithine

Human breast adenocarcinoma cells MCF-7 were selected for resistance to ornithine decarboxylase (ODC) inhibitor, alpha-difluoromethylornithine (DFMO). Stepwise increments of the concentration of DFMO resulted in selection of MCF-7 cells that were capable of growing in the presence of 1.0 mM DFMO. This capacity was associated with a 10-fold increase in ODC activity and marked enhancement in the synthesis rate of ODC protein as verified by a 2-hr [35S]methionine labeling of cellular proteins followed by immunoprecipitation and SDS-PAGE. The resistant cells had much higher concentration of putrescine, spermidine, and spermine than the control cells. A 25-fold increase in ED50 (effective dose causing 50% inhibition) for the antiproliferative action of DFMO in these resistant cells was observed. The susceptibility of wild-type and resistant cell lines to other inhibitors of the polyamine biosynthetic pathway and adriamycin is also reported.