Ethanol, not fat accumulation per se, increases free radical production in a low-flow, reflow liver perfusion model

Twenty-seven diarrheagenic Escherichia coli (DEC) strains from five closely related, genetically distinct clones (DEC 3, 4, 8, 9, and 10), representing serotypes commonly associated with Shiga-like toxin production, i.e., O15:H-, O26:(H11, H-), O111:(H8, H11, H-), and O157:H7, were evaluated for colicinogeny on Luria agar or Luria agar containing 0.25 microgram/ml mitomycin C to induce colicin production. Ten (37%) of the DEC strains tested were colicinogenic. One of 11 serotype O157:H7 strains, DEC strain 4E, produced a colicin identified as Col D. DEC strains 8B, 9D, and 10B produced Col E1, whereas DEC strain 10A produced Col E2. DEC strains 8A, 8E, 10C, 10E, and 10F produced "untypable" colicins that killed almost all Pugsley Colicin Reference Set strains and the other DEC strains tested. To aid with further characterization of the colicins, plasmids extracted from each colicin-producing (Col+) DEC strain were used to transform E. coli strain DH5 alpha. All Col+ DH5 alpha transformants contained one plasmid ranging in size from 1.3 to 10 kb. Some transformants were stable colicin producers whereas others were unstable. The inhibitory activity and colicin sensitivity and insensitivity profiles of the Col+ transformants were similar to those of the corresponding Col+ donor DEC strains. It appears that the untypable colicins are novel and, thus, warrant further study. Colicin production by some of the DEC strains evaluated partly explains why they were insensitive to standard colicins in a previous study.     

Rapid degeneration of cultured human brain pericytes by amyloid beta protein

Amyloid beta protein (A beta) deposition in the cerebral arterial and capillary walls is one of the major characteristics of brains from patients with Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Vascular A beta deposition is accompanied by degeneration of smooth muscle cells and pericytes. In this study we found that A beta 1-40 carrying the "Dutch" mutation (HCHWA-D A beta 1-40) as well as wild-type A beta 1-42 induced degeneration of cultured human brain pericytes and human leptomeningeal smooth muscle cells, whereas wild-type A beta 1-40 and HCHWA-D A beta 1-42 were inactive. Cultured brain pericytes appeared to be much more vulnerable to A beta-induced degeneration than leptomeningeal smooth muscle cells, because in brain pericyte cultures cell viability already decreased after 2 days of exposure to HCHWA-D A beta 1-40, whereas in leptomeningeal smooth muscle cell cultures cell death was prominent only after 4-5 days. Moreover, leptomeningeal smooth muscle cell cultures were better able to recover than brain pericyte cultures after short-term treatment with HCHWA-D A beta 1-40. Degeneration of either cell type was preceded by an increased production of cellular amyloid precursor protein. Both cell death and amyloid precursor protein production could be inhibited by the amyloid-binding dye Congo red, suggesting that fibril assembly of A beta is crucial for initiating its destructive effects. These data imply an important role for A beta in inducing perivascular cell pathology as observed in the cerebral vasculature of patients with Alzheimer's disease or HCHWA-D.     

Impact of severity of coronary artery stenosis and the collateral circulation on the functional outcome of dyssynergic myocardium after revascularization in patients with healed myocardial infarction and chronic left ventricular dysfunction

The inferoposterior region of the triangle of Koch is hypothesized to be the location of the atrial insertion of the slow atrioventricular (AV) nodal pathway. However, the actual site of conduction slowing in the slow AV nodal pathway is unknown. Entrainment mapping during AV nodal reentry can localize the reentrant pathway as follows: the AH interval measured from the mapping catheter = A'H (where A' is the exit site of the reentrant circuit) minus A'A (the conduction time from A' to the site of mapping); the SH interval during entrainment = SA' (the conduction time from stimulus into the reentry circuit) plus A'H. Thus, in all cases, the SH interval should be greater than or equal to the AH interval, and the deltaAH-SH should increase as distance and conduction time (SA' and A'A) from the reentry circuit increases. Fourteen patients with typical AV nodal reentry (cycle length 346 +/- 62 ms) and 1 with fast-slow (cycle length 430 ms) underwent activation and entrainment mapping from 8 to 12 sites in the triangle of Koch and coronary sinus. Pacing was performed at 2 to 3 mA above threshold, at a cycle length 10 ms shorter than tachycardia. A mapping site was defined as being in close proximity to the circuit if the deltaAH-SH was within 120% of the shortest 20th percentile deltaAH-SH value from all measured sites. In the 14 typical cases, 45 of 83 sites (54%) in the anatomic slow pathway region fulfilled criteria for close proximity to the reentry circuit compared with 13 of 50 sites (26%) outside of this region (p = 0.005). For these patients, the shortest SH interval measured from any entrainment site was 294 +/- 58 ms (89 +/- 10% of tachycardia cycle length, range 70% to 119%), indicating that the site of slow conduction in the slow pathway during AV nodal reentrant tachycardia was distal to all mapped sites. Thus, during typical AV nodal reentry, the "slow" pathway does not conduct slowly, and its insertion is located at or within the inferoposterior or midseptal regions in most cases.     

Comparative study of astrocytes in human and rabbit retinae

Immunohistochemical location of Glial Fibrillary Acidic Protein (GFAP) was used to compare the morphology of astrocytes in vascularized and partially vascularized retinae (human and rabbit, respectively). Astrocytes in human and rabbit retinae were found in the same regions as the blood vessels. These cells in partially vascularized retinae differed from those in vascularized retina in several respects. Firstly, there were six morphological types in rabbit retina and only two in human retina. Secondly, in rabbit retinae there were astrocytes only related to blood vessels called "perivascular astrocytes" which were absent in human retinae. Thirdly, the astrocytes were located in the nerve fiber layer and ganglion cell layer in both types of retinae, but in human retinae these cells could also be seen in the internal nuclear layer. These observations demonstrate that there are many differences between astrocytes in human and rabbit retina, suggesting that rabbit retina could be used with caution as an experimental model in comparative studies with human retina.     

Blockade of the CD40-CD40 ligand pathway potentiates the capacity of donor-derived dendritic cell progenitors to induce long-term cardiac allograft survival

BACKGROUND: Failure of costimulatory molecule-deficient donor dendritic cells (DCs) to induce indefinite allograft acceptance may be a result of the 'late" up-regulation of these molecules on the DCs after interaction with host T cells. Ligation of CD40 on antigen-presenting cells by its cognate ligand CD40L is thought to induce expression of CD80 (B7-1) and CD86 (B7-2). We examined the influence of anti-CD40L monoclonal antibody (mAb) on the capacity of donor-derived DC progenitors to induce long-term allograft survival. METHODS: High purity DC progenitors were grown from B10 (H2b) mouse bone marrow in granulocyte-macrophage colony-stimulating factor and transforming growth factor beta1 (TGFbeta1). Mature DC were propagated in granulocyte-macrophage colony-stimulating factor and interleukin-4. Their phenotype was characterized by flow cytometric analysis and their function by mixed leukocyte reactivity. Anti-donor cytotoxic T lymphocyte activity in grafts and spleens of vascularized heart allograft recipients was also assessed. RESULTS: The TGFbeta3-cultured cells were (1) DEC 205-positive, MHC class II-positive, CD80dim, CD86dim, and CD40dim, (2) poor stimulators of naive allogeneic T-cell proliferation, and (3) able to prolong significantly B10 cardiac allograft survival in C3H (H2k) recipients when given (2 x 10[6] i.v.) 7 days before organ transplantation (median survival time [MST] 26 days vs. 12 days in controls, and 5 days in interleukin-4 DC-treated animals). Their allostimulatory activity was further diminished by addition of anti-CD40L mAb at the start of the mixed leukocyte cultures. Anti-CD40L mAb alone (250 microg/mouse, i.p.; day -7) did not prolong cardiac graft survival (MST 12 days). In contrast, TGFbeta-cultured DCs + anti-CD40L mAb extended graft survival to a MST of 77 days, and inhibited substantially the anti-donor cytotoxic T lymphocyte activity of graft-infiltrating cells and host spleen cells assessed 8 days after transplant. CONCLUSIONS: The CD40-CD40L pathway appears important in regulation of allogeneic DC-T-cell functional interaction in vivo; its blockade increases markedly the potential of costimulatory molecule-deficient DCs of donor origin to induce long-lasting allograft survival.     

Imaging of delta- and mu-opioid receptors in temporal lobe epilepsy by positron emission tomography

The authors report the postoperative magnetic resonance (MR) imaging findings in 36 patients with advanced Parkinson's disease who underwent unilateral microelectrode-guided posteroventral pallidotomy. The lesions were placed within 1 mm of the ventral border of the globus pallidus internus (GPi) to include pallidothalamic outflow pathways. Sequential MR studies were obtained within 1 to 3 days postoperatively and at 6-month follow-up examination. Thirty-four (94%) of the 36 patients enjoyed sustained moderate or marked improvement of their parkinsonian symptoms 6 months postoperatively. Transient side effects occurred in five patients (14%), but there were no persistent complications. The pallidal radiofrequency lesions were prolate spheroid shaped and were composed of three concentric zones in the early postoperative studies. The mean volume of the middle zone, corresponding to the area of hemorrhagic coagulation necrosis, was 44.4 +/- 17.6 mm3; the mean lesion volume as defined by the outer zone, corresponding to perilesional edema, was 262.2 +/- 111.6 mm3. Additional edema spreading to the internal capsule was noted in 32 of 34 cases and to the optic tract in 11 of 34 cases. In two patients small ischemic infarctions involving the corona radiata were found, and in one a venous infarction was detected. Ischemic infarction resulted in mild transient Broca's aphasia in one patient, but there was no detectable neurological deficit in the other two. The mean volume of late-phase (6 months) lesions was 22 +/- 28.8 mm3. In three patients no lesion was identified despite sustained clinical improvement. The lesion was located in the posteroventral GPi in all cases except in one patient in whom it was confined to the GP externus (GPe). This 49-year-old woman did not experience sustained benefit. The authors found no consistent correlations between lesion size and location and clinical outcome as measured by a global outcome score, the Unified Parkinson's Disease Rating Scale motor, activities of daily living, and bradykinesia "off" scores or rating of dyskinesias. Lesioning of pallidal and subpallidal pathways may contribute to the sustained clinical benefit in this series. Magnetic resonance imaging analysis showed that intraoperative microelectrode recording facilitated accurate placement of the lesion in this critical area.     

Risk factors for adverse drug reactions during thiacetazone treatment of pulmonary tuberculosis in human immunodeficiency virus infected adults

It is well established that many continuously distributed traits have a heritable component. However, it is often difficult to communicate to the general public the meaning of quantitative estimates of heritability. To address this problem, the present paper introduces a heuristic for communicating heritability to nonscientific audiences. This heuristic involves adopting an extremely simplified model of inheritance and artificially (and somewhat arbitrarily) defining a cutoffs of "low environmental risk" and "affectation status." Using body weight and obesity as an example, we present a table which gives estimates of the proportion of obese persons who are "genetically obese" assuming varying levels of "environmental risk" for obesity and relative body weight scores for defining obesity. The resulting statistic may prove useful for lay audiences in understanding a heritability estimate.     

Troponin T mRNA and protein isoforms in the human left ventricle: pattern of expression in failing and control hearts

We and others have previously cloned several cDNAs of human cardiac troponin T (cTnT), demonstrating the multiplicity of cTnT isoforms in the human heart. Four of them named cTnT1, 2, 3 and 4 result from a combinatorial alternative inclusion of 30- and 15-nucleotides in the 5' coding region of the cDNAs. In failing human ventricles, increased expression of cTnT4 has been reported at the protein level. More recent RT-PCR experiments showed increased expression of fetal-type splicing products in the 5' region, one of them corresponding to cTnT1. To clarify this issue, we examined the accumulation of the 4 cTnT mRNA and protein species in left ventricular specimens at the time of heart transplantation, and in control left ventricular samples using RNase protection and Western blotting. In all samples, cTnT3 was the major mRNA isoform, cTnT4 a minor isoform while cTnT1 and cTnT2 mRNAs were present but barely detectable. At the protein level, cTnT3, 4 and 1 were detected with the same relative abundance as that seen at the mRNA level. In addition, we detected a fourth TnT species of very low abundance corresponding either to a skeletal or to a "short" cardiac TNT isoform. Compared to controls, increased levels of cTnT4 mRNA and protein were detected in only half the failing ventricles independently of the cause of failure, suggesting that this increase may not be a general characteristic of left ventricular failure but instead could be related to stress. Unexpectedly, we found a decrease in cTnT1 protein expression in all failing ventricular samples studied, compared to controls.     

Effects of Si,Mn, and water vapour on the microstructure of protective scales grown on Fe–20Cr in CO2 gas

Abstract

Model alloys Fe–20Cr–0.5Si and Fe–20Cr–2Mn (wt-%) were exposed to Ar–20CO₂ and Ar–20CO₂–20H₂O at either 818 or 650°C. In dry gas, protective scales on Fe–20Cr–0.5Si consisted of an outer Cr₂O₃ layer and an inner SiO₂ layer. In wet gas, additional chromia whiskers were formed on top of the duplex scale. Chromia grains formed in wet gas were much smaller than those in dry gas. A TEM analysis revealed that phase constitutions of the protective scale on Fe–20Cr–2Mn were not uniform: Mn₃O₄ and MnCr₂O₄ above alloy grain boundaries and Mn₃O₄, Cr₂O₃ and MnCr₂O₄ on alloy grains. Formation of different oxides and morphologies are discussed in terms of changes in diffusion paths and thermodynamics caused by the presence of carbon and hydrogen.