Additional observations on the sporozoite transmission of Plasmodium knowlesi to monkeys

Saimiri boliviensis monkeys were infected by the intravenous injection of 50 sporozoites of the H strain of Plasmodium knowlesi dissected from the salivary glands of Anopheles dirus mosquitoes; prepatent periods were 11, 12, 13, 13, 13, and 16 days. Sporozoites of P. knowlesi stored frozen for 7 days, 53 days, 20 mo, 7 yr and 7 mo, and 11 yr and 5 mo induced infections in Macaca mulatta monkeys with prepatent periods of 7, 6, 8, 10, and 7 days, respectively. After frozen storage for 11 yr and 5 mo, infections were induced in S. boliviensis with prepatent periods of 10-13 days.     

Past and recent physical activity and bone mineral density in college-aged women

Low bone mineral density (BMD) has been determined as an independent factor of osteoporosis. The purpose of this study was to assess physical activity's effect on BMD in college-aged women. Bone density measurements were obtained. A survey was administered to assess past and recent physical activity levels. Logistic regression revealed high school sports participation and lean tissue were significant predictors of femoral BMD, whereas present physical activity and lean tissue were significant predictors of spinal BMD. Women in the present study who did not participate in high school sports were 7 times more likely to have low BMD than were those who participated. This study revealed a protective effect of past and present physical activity on BMD in college-aged women. Children and young adults should be encouraged to participate in physical activity because it helps reduce their risk factors for osteoporosis later in life.     

Cellular chromium enhances activation of insulin receptor kinase

Chromium has been recognized for decades as a nutritional factor that improves glucose tolerance by enhancing in vivo insulin action, but the molecular mechanism is unknown. Here we report pretreatment of CHO-IR cells with chromium enhances tyrosine phosphorylation of the insulin receptor. Different chromium(III) compounds were effective at enhancing insulin receptor phosphorylation in intact cells, but did not directly activate recombinant insulin receptor kinase. The level of insulin receptor phosphorylation in cells can be increased by inhibition of the opposing protein tyrosine phosphatase (PTP1B), a target for drug development. However, chromium did not inhibit recombinant human PTP1B using either p-nitrophenyl phosphate or the tyrosine-phosphorylated insulin receptor as the substrate. Chromium also did not alter reversible redox regulation of PTP1B. Purified plasma membranes exhibited insulin-dependent kinase activity in assays using substrate peptides mimicking sites of Tyr phosphorylation in the endogenous substrate IRS-1. Plasma membranes prepared from chromium-treated cells had higher specific activity of insulin-dependent kinase relative to controls. We conclude that cellular chromium potentiates insulin signaling by increasing insulin receptor kinase activity, separate from inhibition of PTPase. Our results suggest that nutritional and pharmacological therapies may complement one another to combat insulin resistance, a hallmark of type 2 diabetes.     

Linkage disequilibrium inflates type I error rates in multipoint linkage analysis when parental genotypes are missing

OBJECTIVES: Describe the inflation in nonparametric multipoint LOD scores due to inter-marker linkage disequilibrium (LD) across many markers with varied allele frequencies. METHOD: Using simulated two-generation families with and without parents, we conducted nonparametric multipoint linkage analysis with 2 to 10 markers with minor allele frequencies (MAF) of 0.5 and 0.1. RESULTS: Misspecification of population haplotype frequencies by assuming linkage equilibrium caused inflated multipoint LOD scores due to inter-marker LD when parental genotypes were not included. Inflation increased as more markers in LD were included and decreased as markers in equilibrium were added. When marker allele frequencies were unequal, the r2 measure of LD was a better predictor of inflation than D'. CONCLUSION: This observation strongly supports the evaluation of LD in multipoint linkage analyses, and further suggests that unaccounted for LD may be suspected when two-point and multipoint linkage analyses show a marked disparity in regions with elevated r2 measures of LD. Given the increasing popularity of high-density genome-wide SNP screens, inter-marker LD should be a concern in future linkage studies.     

Mechanisms of statin-mediated inhibition of small G-protein function

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been reported to reduce the risk of Alzheimer disease. We have shown previously that statins inhibit a beta-amyloid (Abeta)-mediated inflammatory response through mechanisms independent of cholesterol reduction. Specifically, statins exert anti-inflammatory actions through their ability to prevent the isoprenylation of members of the Rho family of small G-proteins, resulting in the functional inactivation of these G-proteins. We report that statin treatment of microglia results in perturbation of the cytoskeleton and morphological changes due to alteration in Rho family function. Statins also block Abeta-stimulated phagocytosis through inhibition of Rac action. Paradoxically, the statin-mediated inactivation of G-protein function was associated with increased GTP loading of Rac and RhoA, and this effect was observed in myeloid lineage cells and other cell types. Statin treatment disrupted the interaction of Rac with its negative regulator the Rho guanine nucleotide dissociation inhibitor (RhoGDI), an interaction that is dependent on protein isoprenylation. We propose that lack of negative regulation accounts for the increased GTP loading. Isoprenylation of Rac is also required for efficient interaction with the plasma membrane, and we report that statin treatment dramatically reduces the capacity of Rac to interact with membranes. These results suggest a mechanism by which statins inhibit the actions of Rho GTPases and attenuate Abeta-stimulated inflammation.     

Increased gelsolin expression and retarded collagen lattice contraction with smooth muscle cells from Crohn's diseased intestine

Intestinal smooth muscle cells (SMC) produce the fibrotic tissue, strictures, that characterize Crohn's disease. These SMC change their phenotype from a contractile muscle form to an inflammation-responsive form that migrates and synthesizes a collagen matrix. It is postulated that the inflammatory responsive SMC form associates differently with its surrounding collagen matrix compared to the normal SMC form. SMC derived from Crohn's diseased and uninvolved bowel were sustained in cell culture. Cultured SMC incorporated in collagen lattices have the capacity to reduce the size of that lattice, referred to as lattice contraction. At day 2, Crohn's SMC-populated collagen lattices were reduced to 21% of their initial area, while non-Crohn's SMC collagen lattices were reduced to 8%. Crohn's SMC demonstrate retarded lattice contraction compared to non-Crohn's SMC. When grown in monolayer culture, Crohn's-derived SMC cover 30% more area than non-Crohn's SMC. By Western blot analysis Crohn's SMC express more gelsolin, an actin-binding protein found elevated in cells exhibiting increased cell motility. Was the increased expression of gelsolin related to retarded collagen lattice contraction? Intracellular levels of gelsolin were elevated by the electroporation of plasma gelsolin protein into suspended non-Crohn's SMC. When incorporated in collagen lattices, gelsolin loaded cells showed retarded lattice contraction compared to SMC loaded with albumin. Crohn's SMC show increased expression of gelsolin, which may be associated with a diminished capacity to reorganize collagen fiber bundles. It is suggested that increased concentrations of gelsolin in Crohn's SMC is consistent with enhanced cell migration as a consequence of the inflammatory state of Crohn's diseased intestine.     

Binding characteristics of [3H]17beta-estradiol in the hypothalamus of juvenile rainbow trout, Oncorhynchus mykiss

Gonadal steroids in the salmonid brain, acting through cellular receptors, may be responsible for the modulation of neuronal activity and organization of reproductive behaviors. We report our findings on the use of [3H]17beta-estradiol (E2) to identify intracellular estrogen receptors (ERs) in the hypothalamus of juvenile rainbow trout, Oncorhynchus mykiss. Specific binding (B(SP)) of [3H]E2 was tissue dependent between 0.5 and 2.25 hypothalamus equivalents for cytosol and nuclear extract preparations, respectively. B(SP) in cytosol fractions increased with time and reached maximum levels (4.18 nM) at 2.5 h incubation; by contrast, B(SP) in nuclear extract increased with time to achieve maximum levels (3.9 nM) by 2 h incubation. The association rate constants (k(+1)) for cytosol and nuclear extract preparations were 1.10 +/- 0.02 x 10(8) M(-1) min(-1) and 1.27 +/- 0.04 x 10(8) M(-1) min(-1), respectively. Equilibrium bound B(SP) dissociated from cytosol preparations with a half life (t1-2) of 42 min and a dissociation rate constant (k(-1)) of 1.01 +/- 0.03 min(-1). B(SP) dissociated from nuclear extract preparations with a t1-2 = 45 min and k(-1)= 0.92 +/- 0.01 min(-1) x B(SP) was saturable in both extract preparations with a calculated equilibrium dissociation constant (Kd) of 1.46 +/- 0.1 nM (cytosol) and 2.37 +/- 0.2 nM (nuclear), and a maximum number of binding sites (B(MAX)) of 50.85 +/- 3.2 fmol mg(-1) protein and 61.74 +/- 2.65 fmol mg(-1) protein, respectively. In both preparations, B(SP) was differentially displaced by structurally similar compounds with a rank order of potency of E2 > estrone > estriol > 17alpha-ethynyl estradiol > testosterone > progesterone = tamoxifen > cortisol > dexamethasone > > beta-sitosterol. These properties of specifically bound [3H]E2 suggest the presence of an ER in the hypothalamus of juvenile rainbow trout comparable with ERs identified in salmonid liver.     

Transgenic plants as factories for biopharmaceuticals

Plants have considerable potential for the production of biopharmaceutical proteins and peptides because they are easily transformed and provide a cheap source of protein. Several biotechnology companies are now actively developing, field testing, and patenting plant expression systems, while clinical trials are proceeding on the first biopharmaceuticals derived from them. One transgenic plant-derived biopharmaceutical, hirudin, is now being commercially produced in Canada for the first time. Product purification is potentially an expensive process, and various methods are currently being developed to overcome this problem, including oleosin-fusion technology, which allows extraction with oil bodies. In some cases, delivery of a biopharmaceutical product by direct ingestion of the modified plant potentially removes the need for purification. Such biopharmaceuticals and edible vaccines can be stored and distributed as seeds, tubers, or fruits, making immunization programs in developing countries cheaper and potentially easier to administer. Some of the most expensive biopharmaceuticals of restricted availability, such as glucocerebrosidase, could become much cheaper and more plentiful through production in transgenic plants.