Contribution of prostaglandins in hypoxia-induced vasodilatation in isolated rabbit hearts. Relation to adenosine and KATP channels

The mechanism of hypoxia-induced coronary vasodilatation was studied in isolated, saline-perfused rabbit hearts under constant flow conditions. Reduction in the perfusion solution PO₂ (from 520±6 to 103±9 mm Hg) under control conditions halved the coronary resistance and was accompanied by a significant release of the prostaglandin (PG) 6-keto-PGF₁ (from 1.8±0.3 to a maximum of 4.4±0.9 pmol min^–1 g^–1). The cyclooxygenase inhibitor, diclofenac (1 M), blocked the release of PGI₂ and reduced hypoxia-induced vasodilatation (from 47±8% to 25±5%, P<0.05). The relative contribution of adenosine, prostaglandins, and adenosine triphosphate (ATP)-sensitive K⁺ channel (K_ATP channel) activation in hypoxia-induced vasodilatation was assessed by comparing the differential change (control response minus response after treatment) in coronary perfusion pressure (CPP) during infusion of 8-phenyltheophylline (8-PT), diclofenac, and glibenclamide, respectively. The differential change in CPP with 8-PT and diclofenac given together (–48 ±7%) was found to be equivalent to the sum of their respective effects (–24±7 and –19±4%, respectively). Glibenclamide (0.3 M) reduced significantly hypoxia-induced vasodilatation (differential change in CPP of –27±6%) as well as the dilator response to 10 M adenosine and to the stable PGI₂-analogue, iloprost. Forskolin-induced coronary vasodilatation in arrested hearts was slightly, but significantly, reduced by glibenclamide. Our results suggest that both cyclooxygenase products and adenosine, acting independently and concomitantly, contribute to the dilator response of coronary resistance vessels to hypoxia, in part through the activation of K_ATP channels. K_ATP channel activation by prostacyclin and adenosine may involve both cyclic adenosine monophosphate-dependent and independent pathways.     

Cruzipain induces both mucosal and systemic protection against Trypanosoma cruzi in mice

Cruzipain, the major cysteinyl proteinase of Trypanosoma cruzi, is expressed by all developmental forms and strains of the parasite and stimulates potent humoral and cellular immune responses during infection in both humans and mice. This information suggested that cruzipain could be used to develop an effective T. cruzi vaccine. To study whether cruzipain-specific T cells could inhibit T. cruzi intracellular replication, we generated cruzipain-reactive CD4(+) Th1 cell lines. These T cells produced large amounts of gamma interferon when cocultured with infected macrophages, resulting in NO production and decreased intracellular parasite replication. To study the protective effects in vivo of cruzipain-specific Th1 responses against systemic T. cruzi challenges, we immunized mice with recombinant cruzipain plus interleukin 12 (IL-12) and a neutralizing anti-IL-4 MAb. These immunized mice developed potent cruzipain-specific memory Th1 cell responses and were significantly protected against normally lethal systemic T. cruzi challenges. Although cruzipain-specific Th1 responses were associated with T. cruzi protective immunity in vitro and in vivo, adoptive transfer of cruzipain-specific Th1 cells alone did not protect BALB/c histocompatible mice, indicating that additional immune mechanisms are important for cruzipain-specific immunity. To study whether cruzipain could induce mucosal immune responses relevant for vaccine development, we prepared recombinant attenuated Salmonella enterica serovar Typhimurium vaccines expressing cruzipain. BALB/c mice immunized with salmonella expressing cruzipain were significantly protected against T. cruzi mucosal infection. Overall, these data indicate that cruzipain is an important T. cruzi vaccine candidate and that protective T. cruzi vaccines will need to induce more than CD4(+) Th1 cells alone.     

Sleep in seasonal affective disorder patients in forced desynchrony: an explorative study

The majority of winter-type seasonal affective disorder (SAD) patients complain of hypersomnia and daytime drowsiness. As human sleep is regulated by the interaction of circadian, ultradian and homeostatic processes, sleep disturbances may be caused by either one of these factors. The present study focuses on homeostatic and ultradian aspects of sleep regulation in SAD. Sleep was recorded polysomnographically in seven SAD patients and matched controls subjected to a 120-h forced desynchrony protocol. In time isolation, subjects were exposed to six 20-h days, each comprising a 6.5-h period for sleep. Patients participated while being depressed, while remitted after light therapy and in summer. Controls were studied in winter and in summer. In each condition, the data of each subject were averaged across all recordings. Thus, the influence of the effects of the circadian pacemaker on sleep was excluded mathematically. The comparison of patients with controls and with themselves in the various conditions revealed no abnormalities in homeostatic parameters: sleep stage variables, relative power spectra and time courses of power in various frequency bands across the first three non-rapid eye movement-rapid eye movement (NREM-REM) cycles showed no differences. The data suggest that homeostatic processes are not involved in the disturbance of sleep in SAD.     

Dietary mannan-oligosaccharides and their effect on chicken caecal microflora in relation to Salmonella Enteritidis colonization

This study first investigates the effects of mash diet, or mash supplemented with either 2.5% mannose-oligosaccharide (MOS) or palm kernel meal (PKM), on the microflora of the hen caecal contents. Second, it investigates the effect of caecal contents of hens (HCC) fed mash or mash supplemented with MOS or PKM on the major microflora groups of chicks, and their inhibitory effect on Salmonella enterica serovar Enteritidis (PT4) colonization. Finally, this study investigates the effect over time of diets supplemented with MOS or PKM on S. Enteritidis colonization and the microflora of chicks. In hens, supplemented diets increased Bifidobacterium spp., while decreasing members of Enterobacteriaceae and Enterococcus spp., compared with the mash diet. Chicks dosed with the HCC showed, on average, increased numbers of anaerobes, while the numbers of aerobes decreased including coliforms and S. Enteritidis compared with controls without HCC. In chicks fed the MOS-supplemented or PKM-supplemented diets, S. Enteritidis colonization decreased over time, compared with mash alone. Four-week-old PKM birds showed an increase in Bifidobacterium spp. and Lactobacillus spp., with a decrease in S. Enteritidis compared with week 2. Generally, the HCC and diets supplemented with MOS or PKM affected the birds intestinal microflora by increasing the Bifidobacterium spp. and Lactobacillus spp., while decreasing the Enterobacteriaceae groups. They also reduced susceptibility in young chickens to colonization by S. Enteritidis.     

Glutamine synthetase is essential in early mouse embryogenesis.

Glutamine synthetase (GS) is expressed in a tissue-specific and developmentally controlled manner, and functions to remove ammonia or glutamate. Furthermore, it is the only enzyme that can synthesize glutamine de novo. Since congenital deficiency of GS has not been reported, we investigated its role in early development. Because GS is expressed in embryonic stem (ES) cells, we generated a null mutant by replacing one GS allele in-frame with a beta-galactosidase-neomycine fusion gene. GS(+/LacZ) mice have no phenotype, but GS(LacZ/LacZ) mice die at ED3.5, demonstrating GS is essential in early embryogenesis. Although cells from ED2.5 GS(LacZ/LacZ) embryos and GS(GFP/LacZ) ES cells survive in vitro in glutamine-containing medium, these GS-deficient cells show a reduced fitness in chimera analysis and fail to survive in tetraploid-complementation assays. The survival of heavily (>90%) chimeric mice up to at least ED16.5 indicates that GS deficiency does not entail cell-autonomous effects and that, after implantation, GS activity is not essential until at least the fetal period. We hypothesize that GS-deficient embryos die when they move from the uterine tube to the harsher uterine environment, where the embryo has to catabolize amino acids to generate energy and, hence, has to detoxify ammonia, which requires GS activity.     

Direct comparison of umbilical cord blood versus bone marrow-derived endothelial precursor cells in mediating neovascularization in response to vascular ischemia.

Endothelial precursor cells (EPCs) cultured from adult bone marrow (BM) have been shown to mediate neovasculogenesis in murine models of vascular injury. We sought to directly compare umbilical cord blood (UCB)- and BM-derived EPC surface phenotypes and in vivo functional capacity. UCB and BM EPCs derived from mononuclear cells (MNC) were phenotyped by surface staining for expression of stromal (Stro-1, CXCR4, CD105, and CD73), endothelial (CD31, CD146, and vascular endothelial [VE]-cadherin), stem cell (CD34 and CD133), and monocyte (CD14) surface markers and analyzed by flow cytometry. The nonobese diabetic/severe combined immunodeficiency murine model of hind-limb ischemia was used to analyze the potential of MNCs and culture-derived EPCs from UCB and BM to mediate neovasculogenesis. Histologic evaluation of the in vivo studies included capillary density as a measure of neovascularization. Surface CXCR4 expression was notably higher on UCB-derived EPCs (64.29%+/-7.41%) compared with BM (19.69%+/-5.49%; P=.021). Although the 2 sources of EPCs were comparable in expression of endothelial and monocyte markers, BM-derived EPCs contained higher proportions of cells expressing stromal cell markers (CD105 and CD73). Injection of UCB- or BM-derived EPCs resulted in significantly improved perfusion as measured by laser Doppler imaging at days 7 and 14 after femoral artery ligation in nonobese diabetic/severe combined immunodeficiency mice compared with controls (P<.05). Injection of uncultured MNCs from BM or UCB showed no significant difference from control mice (P=.119; P=.177). Tissue samples harvested from the lower calf muscle at day 28 demonstrated increased capillary densities in mice receiving BM- or UCB-derived EPCs. In conclusion, we found that UCB and BM-derived EPCs differ in CXCR4 expression and stromal surface markers but mediate equivalent neovasculogenesis in vivo as measured by Doppler flow and histologic analyses.     

Advection and Diffusion of Substances in Biological Tissues With Complex Vascular Networks

For highly diffusive solutes the kinetics of blood–tissue exchange is only poorly represented by a model consisting of sets of independent parallel capillary–tissue units. We constructed a more realistic multicapillary network model conforming statistically to morphometric data. Flows through the tortuous paths in the network were calculated based on constant resistance per unit length throughout the network and the resulting advective intracapillary velocity field was used as a framework for describing the extravascular diffusion of a substance for which there is no barrier or permeability limitation. Simulated impulse responses from the system, analogous to tracer water outflow dilution curves, showed flow-limited behavior over a range of flows from about 2 to 5 ml min^–1 g^–1, as is observed for water in the heart in vivo. The present model serves as a reference standard against which to evaluate computationally simpler, less physically realistic models. The simulated outflow curves from the network model, like experimental water curves, were matched to outflow curves from the commonly used axially distributed models only by setting the capillary wall permeability–surface area (PS) to a value so artifactually low that it is incompatible with the experimental observations that transport is flow limited. However, simple axially distributed models with appropriately high PSs will fit water outflow dilution curves if axial diffusion coefficients are set at high enough values to account for enhanced dispersion due to the complex geometry of the capillary network. Without incorporating this enhanced dispersion, when applied to experimental curves over a range of flows, the simpler models give a false inference that there is recruitment of capillary surface area with increasing flow. Thus distributed models must account for diffusional as well as permeation processes to provide physiologically appropriate parameter estimates. © 2000 Biomedical Engineering Society. PAC00: 8719-j, 8710+e     

Clonal chromosomal changes in juxta-articular myxoma

 Cytogenetic analysis of a juxta-articular myxoma revealed two distinct cytogenetically abnormal cell populations: inv(2)(p15q36) and +7, t(8;22)(q11–12; q12–13). These clonal chromosomal changes, the first to be reported in this tumour type, suggest that at least some juxta-articular myxomas are neoplastic rather than reactive in nature. Received: 8 June 1998 / Accepted: 17 August 1998