The loss of poliovirus 1 infectivity in marine waters

The loss of infectivity (LOI) of poliovirus 1 in marine water from the Gulf of Mexico was studied. Typically, three logs of infectivity were lost in 5–6 days at 24°C. Experiments described in this report suggested that this LOI was not a result of container adsorption or virion aggregation: nor was a resistant component within the stock virus found that would have explained the two-component curves often observed with the virus loss. Viral infectivity loss occurred in raw, filter-sterilized, and autoclaved marine water. Loss was also observed when the virus was suspended in artificial seawater of 1, 10 and 20 g kg⁻¹ salinity. No explanation for the LOI other than true inactivation of the virion was found. The specific component(s) of marine water responsible for virion inactivation remains to be ascertained.     

Calibrating multibody ulno-humeral joint cartilage using a validated finite element model

Correct prediction of contact characteristic in multibody models is a challenging issue, which requires both employing an appropriate contact model and choosing its corresponding contact parameters. This study employed two subject specific multibody models of the ulno-humeral joint where the humerus cartilage was discretized and interacted with the ulna cartilage through a deformable contact. Parameters for the deformable contact were optimized by matching the maximum predicted contact pressure in the multibody models with contact pressures predicted in identical finite element models under axial 110 N compressive load. The performance of the optimized contact parameters and employed approach was evaluated under two other loading conditions of 80 and 140 N. Moreover, the effect of discretized element size on the contact prediction was also addressed. After optimization of the contact parameters, the difference between the multibody and FE models in terms of peak and average contact pressure, and contact area was significantly reduced (more than a factor of 10). Smaller discretization size of the humerus cartilage in the multibody models resulted in better predictions especially on highly curved regions. However, the optimized parameters of our study were different between the two elbows. This indicates that optimized contact parameters can be different not only among different joints, but also among different specimens and optimization conditions. Therefore, in order to improve contact predictions, separate contact optimization should be performed for each subject.     

Electromyography of the reticulum, abomasum and duodenum in dairy cows with left displacement of the abomasum

Electromyographic (EMG) recordings of the reticulum, abomasal corpus, pyloric antrum and duodenum of six dairy cows with left displacement of the abomasum (LDA) were made in order to substantiate abomasal atony as a prerequisite to abomasal displacement. EMG recordings were made when LDA was present as well as when absent. Mean values were determined in five of six cows for the maximum peak or amplitude, mean peak values, peak-to-peak interval and count of the electrical response activity (ERA) for each 15 min segment of the waveform recordings. Segments containing phase III migrating myoelectric activity were not analysed. LDA positive periods were compared to LDA negative periods in each cow. The 6 h period (transition period) prior to the diagnosis of LDA was analysed separately. Paired t-tests were applied to group values with statistical significance established at the P = 0.05 level. There was a significant decrease in the ERA count during the LDA positive periods in the abomasal corpus (-1.40% to -7.88%, P = 0.0217) and in the pyloric antrum (-2.05% to -11.98%, P = 0.0430). A corresponding significant increase occurred in the peak-to-peak interval. During the transition period spike activity in the duodenum increased 0.5% to 48.31% (P = 0.0474) and the peak-to-peak interval was significantly decreased. No extended periods of atony were observed in the abomasum during this study.     

Intraoperative enteroscopy. Indications and techniques

This article reviews the role on intraoperative enteroscopy (IOE) in the management and evaluation of patients with chronic transfusion-dependent gastrointestinal bleeding who have not responded to standard diagnostic and therapeutic techniques. Intraoperative enteroscopy may be performed with a standard or pediatric colonoscope, push enteroscope, or a sonde enteroscope at the time of laparotomy. IOE techniques as well as indications, diagnostic and therapeutic capabilities, and complications of this procedure are discussed.     

Preventing perinatal transmission of HIV--costs and effectiveness of a recommended intervention

OBJECTIVE: To calculate the national costs of reducing perinatal transmission of human immunodeficiency virus through counseling and voluntary testing of pregnant women and zidovudine treatment of infected women and their infants, as recommended by the Public Health Service, and to compare these costs with the savings from reducing the number of pediatric infections. METHOD: The authors analyzed the estimated costs of the intervention and the estimated cost savings from reducing the number of pediatric infections. The outcome measures are the number of infections prevented by the intervention and the net cost (cost of intervention minus the savings from a reduced number of pediatric HIV infections). The base model assumed that intervention participation and outcomes would resemble those found in the AIDS Clinical Trials Group Protocol 076. Assumptions were varied regarding maternal seroprevalence, participation by HIV-infected women, the proportion of infected women who accepted and completed the treatment, and the efficacy of zidovudine to illustrate the effect of these assumptions on infections prevented and net cost. RESULTS: Without the intervention, a perinatal HIV transmission rate of 25% would result in 1750 HIV-infected infants born annually in the United States, with lifetime medical-care costs estimated at $282 million. The cost of the intervention (counseling, testing, and zidovudine treatment) was estimated to be $ 67.6 million. In the base model, the intervention would prevent 656 pediatric HIV infections with a medical care cost saving of $105.6 million. The net cost saving of the intervention was $38.1 million. CONCLUSION: Voluntary HIV screening of pregnant women and ziovudine treatment for infected women and their infants resulted in cost savings under most of the assumptions used in this analysis. These results strongly support implementation of the Public Health Service recommendations for this intervention.     

A placebo-controlled study of liposome-mediated gene transfer to the nasal epithelium of patients with cystic fibrosis

The crystal structure of bovine neurophysin-II in its liganded state (Chen et al. [1991] Proc. Natl. Acad. Sci. USA 88, 4240-4244) indicates that the 1-6 sequence has a disordered conformation, lacks noncovalent contacts to other regions of the protein and is distant from the monomer-monomer interface. Cleavage of the 1-6 sequence by Staphylococcus protease V8 yielded a protein that, for the first time, crystallized in both liganded and unliganded states. Insights into the role of the 1-6 sequence in the unliganded state were obtained by NMR and related biophysical comparisons of the native and des-1-6 proteins. NMR spectra demonstrated that the environment and/or conformation of residues in the 1-6 sequence differed in liganded and unliganded states. Additionally, the unliganded des-1-6 protein exhibited a dimerization constant four to five times that of the native protein, potentially accounting for the observation that its peptide affinity was also increased. NMR studies further indicated that the increased dimerization constant of the des-1-6 protein correlated with the presence in the native protein of two isoenergetic forms of the monomer, in contrast to only a single form in the des-1-6 protein, as evidenced by signals from an internal dimerization-sensitive alpha-proton. Thus, the 1-6 sequence reduces the dimerization constant by stabilization of an alternative monomer conformation. A second product of Staphylococcus protease V8 digestion of the native protein was identified as the des-1-6 protein with an internal clip after binding site residue Glu-47, the clip presumably breaking the short 3,10 helix that most directly connects the interface to the interface to the binding site. This product, although unable to bind peptide, retained the dimerization constant of the des-1-6 protein, suggesting a lack of importance of the helix in dimerization and contrasting with the effects of the 1-6 sequence. A model is proposed in which the 1-6 sequence stabilizes the second conformation of the unliganded monomer via interactions affecting the loop region that separates the two neurophysin domains and which has been shown to influence neurophysin self-association.     

The role of stromal cell heparan sulphate in regulating haemopoiesis

Intimate contact between haemopoietic progenitor cells and elements of the bone marrow stroma is required for progenitor cell proliferation and differentiation. It is believed that the stroma provides particular niches for the development of haemopoietic cells of different lineages. Cytokines, stromal cell surface molecules and molecules of the stromal extracellular matrix all contribute to defining these microenvironmental niches. Data obtained using an in vitro model of haemopoiesis support the view that progenitor cell adhesion to stroma is mediated by multiple receptor-ligand interactions. The possibility of a tethering step, mediated by the engagement of stromal cell heparan sulphate with its ligands on the progenitor cells, preceding stable cell adhesion is discussed. The role of stromal cell heparan sulphate is likely to include cytokine presentation to progenitors as well as the tethering of progenitors to stroma. It is proposed that intracellular signals induced by progenitor cell adhesion to stroma act in association with cytokine induced signals to regulate progenitor cell proliferation and differentiation.