Platelet release of beta-thromboglobulin within the coronary circulation during cold pressor stress

Cold stress by increasing circulating catecholamines may sensitize blood platelets to aggregate and release their constituents. This study investigates the effect of cold stress on the release of the platelet-specific protein beta-thromboglobulin into the coronary venous blood of 12 subjects with atherosclerotic coronary artery disease (CAD) and 7 subjects with angiographically normal coronary arteries (NCA). Cold pressor stress caused a greater increase in systolic arterial pressure in patients with CAD than in subjects with NCA (p less than 0.05). There was no significant difference between the platelet counts in the arterial or coronary venous blood either before or during cold stress. Arterial beta-thromboglobulin was higher in the group with CAD (77 +/- 18 ng/ml) than in subjects with NCA (49 +/- 12 ng/ml, p less than 0.01). Although there was no arteriovenous difference of beta-thromboglobulin at rest in either group, during cold stress, coronary venous beta-thromboglobulin increased in both the NCA (53 +/- 16 to 95 +/- 26 ng/ml, p less than 0.05) and CAD groups (76 +/- 13 to 117 +/- 53 ng/ml, p less than 0.025) despite no change in arterial beta-thromboglobulin. Release of beta-thromboglobulin, although not related to the presence of angiographic arterial disease, correlated with the systolic arterial pressure during cold stress (r = 0.66) and inversely with the platelet's ability to generate cyclic adenosine monophosphate (r = 0.69). The release of platelet constituents in the coronary circulation is provoked by cold stress and may play a role in stress-induced acute coronary occlusion in patients with atherosclerotic disease and in those with apparently normal vessels.     

Blood donation leads to a decrease in natural killer cell activity: a study in normal blood donors and cancer patients

Transfusion-induced immunosuppression has long been known to be beneficial for organ transplantation patients, but recent retrospective studies suggest that blood transfusions may be detrimental for patients with cancer. If autologous blood is used to avoid immunosuppression, the assumption is that the procedure, involving blood donation, is immunologically neutral. In the present study, this assumption was evaluated by monitoring 33 normal blood donors and 16 colorectal cancer patients before and after donation of 1 (500 mL) and 2 units of blood, respectively. The cancer patients belonged to the autologous arm of a randomized trial in which the effects of allogeneic versus autologous blood on cancer prognosis were studied. The patients donated 2 units of blood with an interval of 3 to 4 days between donations. Flow cytometric analysis revealed that blood donation by normal donors and cancer patients had no effect on the proportion of B, T, and natural killer (NK) cells. Only the total number of lymphocytes was significantly decreased in the normal donors on Day 12 after donation. Blood donation had no significant effect on T-cell function assessed by phytohemagglutinin stimulation in normal donors or in cancer patients donating 2 units of blood. A significant depression of NK cell function (88% and 74% of predonation levels) was observed in normal donors on Days 2 and 5 after donation; on Day 12, the activity was again normal. Colorectal cancer patients had a significantly depressed NK cell activity (54% of predonation activity) on Day 12 after the first donation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Australian Experience with VAD as a Bridge to Paediatric Cardiac Transplantation

The Royal Children's Hospital, Melbourne is the National Paediatric Heart Transplant Centre of Australia. A variety of ventricular assist devices (VADs) have been used effectively as a bridge to heart transplantation in adult patients, however, the experience in the paediatric population is limited. We present our initial experience using the Thoratec and Medos VAD systems as a bridge to heart transplantation in the designated centre for paediatric cardiac transplantation in Australia.The medical records of all patients supported with a Thoratec or Medos VAD at the RCH from July 2005 to July 2007 were retrospectively reviewed.Seven patients between 5 and 16 years of age were supported with the Thoratec or Medos VAD during the period of study. All of the patients were supported with a left sided ventricular assist device (LVAD). The length of time supported ranged from 6 to 230 days, with a median of 22 days. Co-morbidities included surgical re-exploration for bleeding, cannula site wound infections and thromboembolic events. Two patients died before a donor heart became available.From our limited experience, the use of a VAD as a bridge to heart transplantation is a feasible option for children with end stage cardiac failure.     

A trade-off in replication in mosquito versus mammalian systems conferred by a point mutation in the NS4B protein of dengue virus type 4

An acceptable live-attenuated dengue virus vaccine candidate should have low potential for transmission by mosquitoes. We have identified and characterized a mutation in dengue virus type 4 (DEN4) that decreases the ability of the virus to infect mosquitoes. A panel of 1248 mutagenized virus clones generated previously by chemical mutagenesis was screened for decreased replication in mosquito C6/36 cells but efficient replication in simian Vero cells. One virus met these criteria and contained a single coding mutation: a C-to-U mutation at nucleotide 7129 resulting in a Pro-to-Leu change in amino acid 101 of the nonstructural 4B gene (NS4B P101L). This mutation results in decreased replication in C6/36 cells relative to wild-type DEN4, decreased infectivity for mosquitoes, enhanced replication in Vero and human HuH-7 cells, and enhanced replication in SCID mice implanted with HuH-7 cells (SCID-HuH-7 mice). A recombinant DEN4 virus (rDEN4) bearing this mutation exhibited the same set of phenotypes. Addition of the NS4B P101L mutation to rDEN4 bearing a 30 nucleotide deletion (Delta30) decreased the ability of the double-mutant virus to infect mosquitoes but increased its ability to replicate in SCID-HuH-7 mice. Although the NS4B P101L mutation decreases infectivity of DEN4 for mosquitoes, its ability to enhance replication in SCID-HuH-7 mice suggests that it might not be advantageous to include this specific mutation in an rDEN4 vaccine. The opposing effects of the NS4B P101L mutation in mosquito and vertebrate systems suggest that the NS4B protein is involved in maintaining the balance between efficient replication in the mosquito vector and the human host.     

DNA evidence of Borrelia lonestari in Amblyomma americanum (Acari: Ixodidae) in southeast Missouri

Amblyomma americanum collected near Lake Wappapello, Missouri, tested positive for Borrelia lonestari using polymerase chain reaction and sequence analyses of B. lonestari 16S rRNA and flagellin (flaB) genes. Twelve pools containing a total of 214 nymph or adult ticks contained evidence of infection with B. lonestari (minimum prevalence 5.6%). These data suggest that persons in southeast Missouri are at risk for exposure to B. lonestari after A. americanum tick bite, a possible cause of erythema migrans-like rash illness in this region. Derivation of the complete coding sequence for B. lonestari flaB is also reported.     

Staphylococcal accessory regulator (sar) in conjunction with agr contributes to Staphylococcus aureus virulence in endophthalmitis.

Previous studies showed that an agr mutant strain of Staphylococcus aureus was partially attenuated in virulence compared to a parental strain in experimental endophthalmitis. The purpose of this study was to determine whether the sar locus, either alone or through interactions with agr, contributes to the regulation of virulence in S. aureus endophthalmitis. Experimental endophthalmitis was established by the midvitreous injection of approximately 30 CFU of S. aureus RN6390 or the isogenic attenuated strains RN6911 (agr mutant), ALC136 (sar mutant), and ALC135 (agr sar double mutant). Unexpectedly, the rate of reduction in electroretinographic B-wave amplitude in eyes infected with strain ALC136 (sar mutant) was not significantly different from the parental strain on postinfection day (PID) 5 (10% retention). In contrast, ALC135 (agr sar double mutant)-infected eyes retained 73% of preoperative B-wave amplitude on PID 5. Therefore, unlike agr, a mutation in the sar locus alone does not alter the overall virulence of wild-type S. aureus in experimental endophthalmitis. However, the combined effect of insertional mutations in both the sar and agr global regulators leads to near-complete attenuation of virulence.     

Web-Based Virtual Microscopy of Digitized Blood Slides for Malaria Diagnosis: An Effective Tool for Skills Assessment in Different Countries and Environments

BackgroundMorphological examination of blood films remains the reference standard for malaria diagnosis. Supporting the skills required to make an accurate morphological diagnosis is therefore essential. However, providing support across different countries and environments is a substantial challenge.ObjectiveThis paper reports a scheme supplying digital slides of malaria-infected blood within an Internet-based virtual microscope environment to users with different access to training and computing facilities. The feasibility of the approach was established, allowing users to test, record, and compare their own performance with that of other users.MethodsFrom Giemsa stained thick and thin blood films, 56 large high-resolution digital slides were prepared, using high-quality image capture and 63x oil-immersion objective lens. The individual images were combined using the photomerge function of Adobe Photoshop and then adjusted to ensure resolution and reproduction of essential diagnostic features. Web delivery employed the Digital Slidebox platform allowing digital microscope viewing facilities and image annotation with data gathering from participants.ResultsEngagement was high with images viewed by 38 participants in five countries in a range of environments and a mean completion rate of 42/56 cases. The rate of parasite detection was 78% and accuracy of species identification was 53%, which was comparable with results of similar studies using glass slides. Data collection allowed users to compare performance with other users over time or for each individual case.ConclusionsOverall, these results demonstrate that users worldwide can effectively engage with the system in a range of environments, with the potential to enhance personal performance through education, external quality assessment, and personal professional development, especially in regions where educational resources are difficult to access.     

Determination of optimal cryoprotectants and procedures for their addition and removal from human spermatozoa

The objective was to test the hypothesis that the optimal cryoprotective agent for cryopreservation of human spermatozoa would be a solute for which cells have the highest plasma membrane permeability, resulting in the least amount of volume excursion during its addition and removal. To test this hypothesis, theoretical simulations were performed using membrane permeability coefficients to predict optimal procedures for the addition and removal of a cryoprotectant. Simulations were performed using data from four different cryoprotectants: (i) glycerol, (ii) dimethyl sulphoxide, (iii) propylene glycol and (iv) ethylene glycol. Thermodynamic formulations were applied to determine approaches for the addition and removal of 1 M and 2 M final concentrations of cryoprotectant, allowing the spermatozoa to maintain a cell volume within their osmotic tolerance limits. Based on these data, ethylene glycol was predicted to be optimal for minimizing volume excursions among the solutes evaluated. These predictions were then experimentally tested using glycerol as the control cryoprotectant and ethylene glycol as the experimental cryoprotectant. The results indicate that there was a higher (P < 0.05) recovery of motile spermatozoa after cryopreservation when using 1 M ethylene glycol than with 1 M glycerol, supporting the hypothesis that use of the cryoprotectant for which the cell has the highest permeability will result in higher cell survival.