Nitric oxide participates in the intestinal pathology associated with murine syngeneic graft-versus-host disease

Syngeneic graft-versus-host disease (SGVHD) develops following lethal irradiation, reconstitution with syngeneic bone marrow, and treatment with a short course of cyclosporin A (CsA) therapy. The disease is characterized by the development of a T helper cell type 1-like cytokine response [interleukin (IL)-12, interferon-gamma (IFN-gamma), and tumor necrosis factor alpha], and macrophage activation is central to development of the syndrome. It has been shown that nitric oxide (NO) participates significantly in the development of allogeneic GVHD. Studies were initiated to determine if NO participates in the pathology associated with SGVHD. Significant increases in inducible NO synthase (iNOS) mRNA and circulating NO were found in the tissues of SGVHD versus control animals. Treatment of SGVHD animals with the iNOS inhibitor aminoguanidine (AG) reversed the pathology associated with this disease. Furthermore, AG treatment reduced the production of IL-12 and IFN-gamma mRNA in the colons of CsA-treated mice. These studies demonstrate that NO participates in the pathological processes that are associated with the development of murine SGVHD.     

The Lipopolysaccharide of Bordetella bronchiseptica Acts as a Protective Shield against Antimicrobial Peptides

Resistance profiles of the two Bordetella species B. bronchiseptica and B. pertussis against various antimicrobial peptides were determined in liquid survival and agar diffusion assays. B. bronchiseptica exhibited significantly higher resistance against all tested peptides than B. pertussis. The most powerful agents acting on B. bronchiseptica were, in the order of their killing efficiencies, cecropin P > cecropin B > magainin-II-amide > protamine > melittin. Interestingly, for B. bronchiseptica, the resistance level was significantly affected by phase variation, as a bvgS deletion derivative showed an increased sensitivity to these peptides. Tn5-induced protamine-sensitive B. bronchiseptica mutants, which were found to be very susceptible to most of the cationic peptides, were isolated. In two of these mutants, the genetic loci inactivated by transposon insertion were identified as containing genes highly homologous to the wlbA and wlbL genes of B. pertussis that are involved in the biosynthesis of lipopolysaccharide (LPS). In agreement with this finding, the two peptide-sensitive mutants revealed structural changes in the LPS, resulting in the loss of the O-specific side chains and the prevalence of the LPS core structure. This demonstrates that LPS plays a major role in the resistance of B. bronchiseptica against the action of antimicrobial peptides and suggests that B. pertussis is much more susceptible to these peptides due to the lack of the highly charged O-specific sugar side chains.     

Coeliac disease, adenocarcinoma of jejunum and in situ squamous carcinoma of oesophagus

The development of both adenocarcinoma of the jejunum and in situ squamous carcinoma of the oesophagus in an adult coeliac patient is described. Good evidence that adenocarcinoma of jejunum occurs more frequently in patients with coeliac disease has recently become available though this association has been suggested for some time. While oesophageal carcinoma has long been associated with coeliac disease, in situ carcinoma of oesophagus has not been previously described in these circumstances. We feel that the risk of this complication, as calculated from published series, warrants a screening programme for oesophageal malignancy in adult coeliacs.     

Granulocyte-macrophage colony-stimulating factor (GM-CSF) but not granulocyte colony-stimulating factor (G-CSF) induces plasma membrane expression of proteinase 3 (PR3) on neutrophils in vitro

The theoretical risk of triggering vasculitis resulting from administration of G-CSF and GM-CSF to patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV), such as Wegener's granulomatosis (WG), who develop agranulocytosis due to cytotoxic therapy, is unknown. Since there is strong evidence that activation of polymorphonuclear neutrophils (PMN) induced by binding of ANCA to PR3 or myeloperoxidase (MPO) expressed on their plasma membrane is involved in the pathogenesis of systemic vasculitides (SV), we studied the surface expression of PR3 and MPO on PMN from healthy donors in response to G-CSF and GM-CSF in vitro by flow cytometric analysis. Increasing doses of G-CSF did not alter PR3 expression on either untreated or tumour necrosis factor-alpha (TNF-alpha)-primed donor PMN significantly. In contrast, GM-CSF significantly increased PR3 membrane expression on both intact PMN and neutrophils primed with TNF-alpha. MPO expression was not significantly altered by either G-CSF or GM-CSF. In summary, these data demonstrate that GM-CSF, but not G-CSF, induces plasma membrane expression of PR3 on PMN in vitro. Since in AAV accessibility of the antigen (PR3 or MPO) to the antibody (ANCA) on the plasma membrane of PMN is thought to be essential for neutrophil activation by ANCA, the results of the present study suggest that administration of GM-CSF to patients with WG with neutropenia implies a definite theoretical risk of deterioration of vasculitis via this mechanism.     

Improvement in ischemic myocardial blood flow following a new calcium antagonist

The effect of FR 7534, a new dihydropyridine CA2+ antagonist, nitroglycerin, and dipyridamole have been compared on coronary collateral function in pentobarbital-anesthetized open-chest dogs following acute ligation of the left anterior descending coronary artery. Measurements of tissue blood flow using radioactive microspheres were made 60 min postligation after low and high doses of each drug and at the higher dose with methoxamine added to to return mean aortic pressure. FR 7534 treatment increased subepicardial, subendocardial, and transmural tissue flow by 100% in the central ischemic zone when perfusion pressure was controlled by methoxamine. Nitroglycerin also increased ischemic tissue flow, but to a lesser degree, 18% transmurally. Dipyridamole produced no significant change. Tissue flow in normal myocardium was similarly increased by FR 7534 and dipyridamole but slightly reduced by nitroglycerin. FR 7534 and nitroglycerin also increased retrograde coronary pressure when aortic presure was maintained constant. FR 7534, but not nitroglycerin, increased ischemic contractile force. In this model, FR 7534 may produce greater effects than nitroglycerin in increasing blood supply to ischemic myocardium delivered by endogenous collaterals especially when aortic perfusion pressure was controlled.     

Enterotoxigenic Escherichia coli in central Canada.

During epidemiological studies carried out in urban and rural areas of the midwestern Canadian province of Manitoba, we cultured enterotoxigenic Escherichia coli (ETEC) from 16 (1.7%) of 945 diarrheal stools and 4 (0.3%) of 1,282 normal stools. ETEC was found in not more than 2.3% of diarrheal stools obtained from any population during any season. Diarrhea associated with ETEC persisted for a mean of 9 days. Two children were dehydrated and required intravenous fluid therapy, and one adult suffered a cholera-like syndrome. Half of the children required hospitalization for management of their diarrhea. Two adults and two children who harbored ETEC were completely asymptomatic. The pattern of toxin production correlated with serotype and the serotypes encountered were (with a few exceptions) similar to those found in other areas. We conclude that ETEC is an uncommon cause of diarrhea, both in rural and urban areas of central Canada. However, the possibility that ETEC might cause severe sporadic cases or epidemics of gastroenteritis remains.     

Threshold pressure for the pressure-dependent renin release in the autoregulating kidney of conscious dogs

1. The effect of varying renal artery pressure between 160 and 40 mm Hg on renal blood flow and renin release was studied in seven conscious foxhounds under β-adrenergic blockade receiving a normal sodium diet (4.1 mmol/kg/day). Pressure was either increased by bilateral common carotid occlusion or reduced in steps and maintained constant by a control-system using an inflatable renal artery cuff. Carotid occlusion itself had no influence on renal blood flow and renin release when renal artery pressure was kept constant and the β-receptors in the kidney were blocked.
2. Between 160 mm Hg and resting pressure there was no change in renal blood flow; between resting blood pressure and the lower limit of autoregulation (average 63.9 mm Hg) renal blood flow increased slightly (average 7%) indicating a high efficiency of renal blood flow autoregulation.
3. The relationship between renal artery pressure and renin release could be approximated by two linear sections:a low sensitivity to a pressure change (average slope: ?0.69 ±0.26ng AI/min/mm Hg) was found above a threshold pressure (average: 89.8±3.3 mm Hg) and a high sensitivity to a pressure change (average slope: ?64.4±20.8 ng AI/ min/mm Hg) was observed between threshold pressure and 60 mm Hg. There was no further increase of renin release between 60 and 40 mm Hg.
4. It is concluded that within the autoregulatory plateau the kidney of a conscious β-blocked dog receiving a normal sodium diet releases only negligible amounts of renin until renal artery pressure falls below a threshold pressure of 90 mm Hg which is close to the animals resting systemic pressure. Since beyond that a decrease of systemic pressure by as little as 1.3 mm Hg below threshold can raise resting renin release (84.8±29.8 ng/min) by 100%, it is suggested that systemic blood pressure tends to stabilize at a level at which renin release is minimal.

     

Differentiation between mouse-virulent and -avirulent strains of Toxoplasma gondii by a monoclonal antibody recognizing a 27-kilodalton antigen.

Using a murine monoclonal antibody, we were able to differentiate between mouse-virulent and -avirulent strains of Toxoplasma gondii. Monoclonal antibody TB6G5 was reactive with eight clinical mouse-avirulent isolates but not with mouse-virulent laboratory strains RH and BK. The antibody-reactive antigen was identified by indirect immunofluorescence and immunoblot as a 27-kDa cytoplasmic protein expressed by tachyzoites as well as by bradyzoites.     

Neutrophil Migration in Opposing Chemoattractant Gradients Using Microfluidic Chemotaxis Devices

Neutrophils migrating in tissue respond to complex overlapping signals generated by a variety of chemotactic factors (CFs). Previous studies suggested a hierarchy between bacteria-derived CFs and host-derived CFs but could not differentiate neutrophil response to potentially equal host-derived CFs (IL-8 and LTB₄). This paper reports neutrophil migration in conflicting gradients of IL-8 and LTB₄ using a microfluidic chemotaxis device that can generate stable and well-defined gradients. We quantitatively characterized the movement of cells from time-lapse images. Neutrophils migrate more efficiently toward single IL-8 gradients than single LTB₄ gradients as measured by the effective chemotactic index (ECI). In opposing gradients of IL-8 and LTB₄, neutrophils show obvious chemotaxis toward a distant gradient, consistent with previous reports. When an opposing gradient of LTB₄ is present, neutrophils show less effective chemotaxis toward IL-8 than when they are in a gradient of IL-8 alone. In contrast, the chemotactic response of neutrophils to LTB₄ is not reduced in opposing gradients as compared to that in a single LTB₄ gradient. These results indicate that the presence of one host-derived CF modifies the response of neutrophils to a second CF suggesting a subtle hierarchy between them.This revised version was published online in May 2005 with corrected author affiliations