High-resolution myocardial perfusion mapping in small animals in vivo by spin-labeling gradient-echo imaging.

An ECG and respiration-gated spin-labeling gradient-echo imaging technique is proposed for the quantitative and completely noninvasive measurement and mapping of myocardial perfusion in small animals in vivo. In contrast to snapshot FLASH imaging, the spatial resolution of the perfusion maps is not limited by the heart rate. A significant improvement in image quality is achieved by synchronizing the inversion pulse to the respiration movements of the animals, thereby allowing for spontaneous respiration. High-resolution myocardial perfusion maps (in-plane resolution=234 x 468 microm2) demonstrating the quality of the perfusion measurement were obtained at 4.7 T in a group of seven freely breathing Wistar-Kyoto rats under isoflurane anesthesia. The mean perfusion value (group average +/- SD) was 5.5 +/- 0.7 ml g(-1)min(-1). In four animals, myocardial perfusion was mapped and measured under cardiac dobutamine stress. Perfusion increased to 11.1 +/- 1.9 ml g(-1)min(-1). The proposed method is particularly useful for the study of small rodents at high fields.     

Identification of Risk Factors for Postoperative Nausea and Vomiting in the Perianesthesia Adult Patient

Postoperative nausea and vomiting (PONV) is a common and potentially debilitating complication of surgery. The preoperative assessment of PONV using established risk assessment tools enables the identification of patients at risk and potentially decreases the incidence of PONV in adult surgical patients. The identification of risk factors associated with PONV and the factors that are independent predictors of PONV preoperatively can facilitate the effective prophylactic treatment and management of PONV in adult surgical patients.     

Emergence of rifampin-resistant Rhodococcus equi with several types of mutations in the rpoB gene among AIDS patients in northern Thailand

The antimicrobial susceptibilities of 30 Rhodococcus equi isolates obtained from 30 patients between 1993 and 2001 in northern Thailand were investigated. The MICs showed a tendency toward resistance to various antibiotics but sensitivity to imipenem, minocycline, vancomycin, and teicoplanin (MICs, /=64 micro g/ml) to rifampin. PCR amplification and DNA sequencing of the rpoB gene and molecular typing by pulsed-field gel electrophoresis (PFGE) were performed for eight R. equi isolates from eight AIDS patients with pneumonia or lung abscess caused by R. equi between 1998 and 2001, including one low- and three high-level rifampin-resistant isolates. As a result, two high-level rifampin-resistant strains with PFGE pattern A had a Ser531Trp (Escherichia coli numbering) mutation, and one high-level rifampin-resistant strain with PFGE pattern B had a His526Tyr mutation, whereas one low-level rifampin-resistant strain with PFGE pattern C had a Ser509Pro mutation. Four rifampin-susceptible strains with PFGE patterns D and E showed an absence of mutation in the rpoB region. Our results indicate the presence of several types of rifampin-resistant R. equi strains among AIDS patients in northern Thailand.     

Six-month multicenter study on invasive infections due to Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis in Argentina

During a 6-month period, 95 invasive infections due to Streptococcus pyogenes and group C or group G Streptococcus dysgalactiae subsp. equisimilis were recorded from 40 centers of 16 cities in Argentina. We describe here epidemiologic data available for 55 and 19 patients, respectively, associated with invasive infections due to S. pyogenes and S. dysgalactiae subsp. equisimilis. The associated isolates and 58 additional pharyngeal isolates were genotyped and subjected to serologic and/or antibiotic susceptibility testing. Group A streptococcal emm type distribution and strain association with toxic shock appeared to differ somewhat from results found within the United States; however, serologic characterization and sof sequence typing suggested that emm types found in both countries are reflective of shared clonal types.     

Structural organization of the neutrophil NADPH oxidase: phosphorylation and translocation during priming and activation

The reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is part of the microbicidal arsenal used by human polymorphonuclear neutrophils (PMNs) to eradicate invading pathogens. The production of a superoxide anion (O2-) into the phagolysosome is the precursor for the generation of more potent products, such as hydrogen peroxide and hypochlorite. However, this production of O2- is dependent on translocation of the oxidase subunits, including gp91phox, p22phox, p47phox, p67phox, p40phox, and Rac2 from the cytosol or specific granules to the plasma membrane. In response to an external stimuli, PMNs change from a resting, nonadhesive state to a primed, adherent phenotype, which allows for margination from the vasculature into the tissue and chemotaxis to the site of infection upon activation. Depending on the stimuli, primed PMNs display altered structural organization of the NADPH oxidase, in that there is phosphorylation of the oxidase subunits and/or translocation from the cytosol to the plasma or granular membrane, but there is not the complete assembly required for O2- generation. Activation of PMNs is the complete assembly of the membrane-linked and cytosolic NADPH oxidase components on a PMN membrane, the plasma or granular membrane. This review will discuss the individual components associated with the NADPH oxidase complex and the function of each of these units in each physiologic stage of the PMN: rested, primed, and activated.     

Characteristics of the transport of oxalate and other ions across rabbit proximal colon

In order to characterize oxalate handling by the P2 segment of the rabbit proximal colon, the fluxes of [¹⁴C]oxalate, ²²Na⁺, and ³⁶Cl^– were measured in vitro using conventional short-circuiting techniques. In standard buffer the proximal colon exhibited net secretion of Na⁺ (–2.31±0.64 equiv cm^–2 h^–1), negligible net Cl^– transport, and net secretion of oxalate (–12.7±1.6 pmol cm^–2 h^–1). Replacement of buffer Na⁺ or Cl^– abolished net oxalate secretion, while HCO ₃ ^– -free media revealed a net absorption of oxalate (19.3±4.2 pmol cm^–2 h^–1) and stimulated NaCl absorption. Mucosal amiloride and dimethylamiloride (1 mM) significantly reduced the unidirectional fluxes of oxalate and enhanced sodium secretion by decreasing J _ms ^Na . The anion exchange inhibitor 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS; 0.1 mM, both sides) reduced the unidirectional fluxes of oxalate and chloride. Serosal epinephrine (50 M) stimulated oxalate absorption (21.3±6.3 pmol cm^–2 h^–1) and sodium absorption (5.71±1.20 equiv cm^–2 h^–1), whereas dibutyryl-cAMP enhanced oxalate secretion (–43.4±6.9 pmol cm^–2 h^–1) and stimulated chloride secretion (–7.27 ±0.64 equiv cm^–2 h^–1). These results indicate that the P2 segment of the proximal colon possesses (a) secretory as well as absorptive capacities, (b) oxalate fluxes that are mediated by pathways involving Na⁺, Cl^–, HCO ₃ ^– transport and (c) a net oxalate flux that is sensitive to absorptive and secretory stimuli.     

Calmodulin loss in vascular smooth muscle following Triton X-100 or saponin skinning

The calmodulin (CaM) content of intact and chemically skinned strips of rat caudal artery was measured using a¹²⁵I-CaM radioimmunoassay. The total CaM measured following homogenization of arterial tissue with EGTA and EGTA/Triton X-100 was 2.58 mol/kg wet tissue. Based on a smooth muscle volume of 40%, this value corresponds to a cellular CaM concentration of 6.5 M. Approximately 97% of total CaM was soluble and approximately 3% was EGTA-nonextractable. Permeabilization of the plasmalemma with 0.15 mg/ml saponin or 0.5% Triton X-100 caused significant detergent-dependent loss of CaM. At the end of a 1 h skinning period, tissues exposed to saponin lost 30% of total CaM. By comparison, tissues skinned under the same conditions with Triton X-100 lost 50%. During a subsequent 4h exposure to relaxing solution, total tissue CaM continued to decline. The exponential loss over the 5h period was described by a first order model having diffusible and nondiffusible CaM components. The diffusible CaM component of saponin skinned tissue (59%) was significantly less than the diffusible component of those skinned with Triton X-100 (88%); however, the rate coefficients for CaM diffusion (0.78 h^–1 and 0.91 h^–1, respectively) did not statistically differ. The nondiffusible component of CaM was significantly larger in saponin treated strips (42%) than in Triton X-100 permeabilized tissue (12%). Arterial strips skinned with Triton X-100, which were subsequently exposed to relaxing solution for up to 22 h, lost significantly more CaM than those retained in Triton X-100 skinning solution for a comparable duration These studies demonstrate the diffusion of CaM from detergent skinned arterial strips and characterize the time course of that loss.