Vascular endothelial growth factor receptor signaling is required for cardiac valve formation in zebrafish.

Vascular endothelial growth factor-receptors (VEGF-Rs) are pivotal regulators of vascular development, but a specific role for these receptors in the formation of heart valves has not been identified. We took advantage of small molecule inhibitors of VEGF-R signaling and showed that blocking VEGF-R signaling with receptor selective tyrosine kinase inhibitors, PTK 787 and AAC 787, from 17-21 hr post-fertilization (hpf) in zebrafish embryos resulted in a functional and structural defect in cardiac valve development. Regurgitation of blood between the two chambers of the heart, as well as a loss of cell-restricted expression of the valve differentiation markers notch 1b and bone morphogenetic protein-4 (bmp-4), was readily apparent in treated embryos. In addition, microangiography revealed a loss of a definitive atrioventricular constriction in treated embryos. Taken together, these data demonstrate a novel function for VEGF-Rs in the endocardial endothelium of the developing cardiac valve.     

A Dynamic Morphometric Model of the Normal Lung for Studying Expiratory Flow Limitation in Mechanical Ventilation

A nonlinear dynamic morphometric model of breathing mechanics during artificial ventilation is described. On the basis of the Weibel symmetrical representation of the tracheobronchial tree, the model accurately accounts for the geometrical and mechanical characteristics of the conductive zone and packs the respiratory zone into a viscoelastic Voigt body. The model also accounts for the main mechanisms limiting expiratory flow (wave speed limitation and viscous flow limitation), in order to reproduce satisfactorily, under dynamic conditions, the expiratory flow limitation phenomenon occurring in normal subjects when the difference between alveolar pressure and tracheal pressure (driving pressure) is high. Several expirations characterized by different levels of driving pressure are simulated and expiratory flow limitation is detected by plotting the isovolume pressure–flow curves. The model is used to study the time course of resistance and total cross-sectional area as well as the ratio of fluid velocity to wave speed (speed index), in conductive airway generations. The results highlight that the coupling between dissipative pressure losses and airway compliance leads to onset of expiratory flow limitation in normal lungs when driving pressure is increased significantly by applying a subatmospheric pressure to the outlet of the ventilator expiratory channel; wave speed limitation becomes predominant at still higher driving pressures.     

Cytokine production pathway in the elderly

It is well known that aging is associated with various alterations in lymphoid cell functions, particularly with a progressive decline in immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Many studies have been focused on the mechanisms of the immunologic features of aging. This review describes our results of studies performed to determine the influence of age on the capacity to produce interleukin-2 (IL-2), interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-6 (IL-6) and tumor necrosis factor (TNF). Mitogen-stimulated cultures of mononuclear cells (MNC) from human beings were assessed for cytokine-producing capacity. A significant decrease in IFN-γ and IL-2 production by MNC cultures from elderly individuals was observed. No significant difference was instead observed between cultures from elderly individuals and those from young ones as regards TNF-α, IL-4 and IL-6 production. Mitogen or antigen-stimulated cultures of MNC from aged mice also displayed a significant decrease in IFN-γ and IL-2 production as well as TNF-β. Instead IL-4 and IL-5 production significantly increased in these cultures. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in the elderly, i.e. a normal or increased humoral response (including autoimmune responses) in face of a low T cell immune responsiveness.     

Effects of combined renovascular hypertension and diabetes mellitus on myocardial cells,non-vascular interstitium and capillaries: a stereological study on rat hearts

Summary The effects of combined renovascular hypertension and diabetes mellitus on the rat heart were investigated in order to detect possible synergistic effects of the two conditions. Hypertensive diabetic and hypertensive non-diabetic animals were compared to diabetic and non-diabetic controls. Hypertension was established for 12 weeks by a surgical stenosis of the left renal artery; diabetes mellitus was maintained for 8 weeks by a single intraperitoneal injection of 60 mg/kg streptozotocin. Light microscopic stereology did not reveal significant divergences between diabetic hypertensives and non-diabetic hypertensives. Hypertension induced a focal perivascular and interstitial fibrosis with increased volume densities of non-vascular interstitium and fibrosis (P<0.001). Capillary density (Q_A) was decreased in transverse sections (P<0.01) and increased in longitudinal sections (P<0.01). This indicates a three-dimensional remodelling of the capillary bed with an increased number of obliquely running capillaries. At least the length density (L_V) of capillaries (mm/mm³) tends to be normalized in long-term renovascular hypertension. At the ultrastructural level, a synergism of hypertension and diabetes mellitus was observed: the volume ratio of mitochondria to myofibrils was significantly decreased in hypertensive diabetics, but not in non-diabetic hypertensives or in diabetics. This may enhance the risk of cardiac deterioration. We conclude that the primary target of the synergistic damage in hypertensive diabetic heart muscle disease is the myocardial cell and not the cardiac interstitium.Preliminary results of this study have been published in: Mall G (1991) Morphometric study on the rat heart in combined renovascular hypertension and diabetes mellitus. In: Nagano N, Dhalla NS (eds) The diabetic heart. Raven Press, New York, pp 115–124Dedicated to Prof. Dr. med. G. Seifert on the occasion of his 70th birthday     

Prevalence of transmitted HIV-1 drug resistance and the role of resistance algorithms: data from seroconverters in the CASCADE collaboration from 1987 to 2003

OBJECTIVES: To examine factors influencing the rate of transmitted drug resistance (TDR) among seroconverters, with particular emphasis on 3 widely used genotypic drug resistance algorithms. METHODS: The study used data from CASCADE (Concerted Action on Seroconversion to AIDS and Death in Europe), a collaboration of seroconverter cohorts in Europe and Canada. Genotypic resistance data were derived within 18 months of the last seronegative test or date of laboratory evidence of acute infection and before the initiation of antiretroviral therapy. The Stanford algorithm was used to analyze each individual's nucleotide sequence. A multivariate logistic model was used to assess independent relationships between the presence of TDR and exposure category, sex, age at seroconversion, and year of seroconversion. The paper also describes 3 alternative definitions of resistance: the Stanford algorithm, the key resistance mutations defined by the International AIDS Society, and the Agence Nationale de Recherches sur le Sida (ANRS) algorithm. RESULTS: Forty-five of 438 patients (10.3%) seroconverting between 1987 and 2003 were infected with a drug-resistant HIV-1 variant. Forty patients (9.1%) showed resistance mutations to only 1 class of antiretroviral drugs, 2 (0.5%) to 2 classes, and 3 (0.7%) to 3 classes of antiretroviral therapy. It was suggested that individuals seroconverting later in calendar time were more likely to have TDR (relative risk 3.89 and 95% CI: 0.84 to 18.02, and relative risk 4.69 and 95% CI: 1.03 to 21.31, for 1996-1999 and 2000-2003, respectively, compared with pre-1996; P trend = 0.08). This trend was apparent regardless of the definition of TDR used. The total estimated proportion of individuals with TDR varied between 10.3% and 15.5% according to which definition was used. CONCLUSIONS: Evidence was found for the rise of TDR over time. A specific definition of what constitutes TDR rather than a simple list of mutations is needed.     

Trypanosoma cruzi antigen that interacts with the beta1-adrenergic receptor and modifies myocardial contractile activity

Previously, we have demonstrated that plasma membranes from the parasite Trypanosoma cruzi (T. cruzi) recognize and adhere to host cells through parasite surface attachment molecules that have affinity for beta(1)-adrenergic receptors (beta(1)-ARs) on target organs. In this report we identify a parasite protein that not only interacts with beta(1)-ARs, but also displays beta-agonist-like activity. We demonstrate that a recombinant maltose binding protein fusion of Tc13 Tul (MBP-Tc13 Tul), a member of the T. cruzi antigen 13 family of surface antigen proteins, competes for binding sites with the beta-adrenergic receptor antagonist [125I]-CYP on membranes purified both from CHO cells expressing human beta(1)-ARs and from rat atria. The competition is prevented by pre-treating MBP-Tc13 Tul with antibodies directed against the EPKSA repeat domain of Tc13 Tul, implicating this portion of the molecule in binding to the beta(1)-AR. Furthermore, MBP-Tc13 Tul activates rat myocardial beta(1)-ARs, resulting in synthesis of cyclic adenosine monophosphate (cAMP) and an increase in cardiac contractility. These biological effects are selectively suppressed by the beta(1)-AR antagonist atenolol, by a synthetic peptide corresponding to the second extracellular loop of the human beta(1)-AR, and by the anti-EPKSA repeat antibodies. These results imply that the Tc13 Tul cell-surface antigen of T. cruzi plays a central role in misregulating the beta(1)-AR following parasite infection, and may be a causative factor of dysautonomic syndrome described in Chagas' disease.     

The Effects of “Immunosympathectomy” on Blood Pressure and Vascular “Reactivity” in Normal and Spontaneously Hypertensive Rats

Newborn litters of spontaneously hypertensive rats (SHR) and normotensive control rats (NCR) were identically treated with sympathetic nerve growth factor antiserum (Wellcome) which markedly interferes with adrenergic cardiovascular control (Zaimis 1967). Blood pressure, measured intermittently during 8 months, was in treated SHR (SHR_is) about 25 % higher than in NCR_is, their respective pressures being about 40 % and 25 % lower than those of sham-treated SHR and NCR.–The hindquarters of one SHR_is, or NCR_is, were then perfused at constant flow in parallel with those of ordinary NCR. Starting from maximal vasodilatation, resistance increases were induced by graded noradrenaline (NA) infusions, from “threshold” to maximal pressor responses. Compared to NCR_is, SHR_is showed an increased resistance at maximal dilatation, an increased slope of the NA dose-response curve and an increased maximal pressor response, while their NA “thresholds” did not differ significantly. Thus, the structurally determined hemodynamic differences between ordinary SHR and NCR (Folkow et al. 1970 b) characterize also SHR_is and NCR_is, though to a reduced extent. Even when comparing SHR_is with ordinary- NCR, which exhibited similar “resting” pressures, these differences partly remain, suggesting that the SHR resistance vessels might, for genetic reasons, be more prone to adapt structurally to pressure loads than those of NCR.     

Fetal development in experimental uremia

Summary Uremic women on hemodialysis with metabolic bone disease (hyperparathyroidism, osteomalacia resulting from defective vitamin D metabolism) and anemia (erythropoietin deficiency) are known to give birth to infants without bone disease or anemia. Therefore, skeletal development (enchondral and desmal bone formation) and hepatic erythropoiesis were evaluated in fetuses of uremic rats. These fetuses failed to show defective mineralisation or evidence of bone disease. Bolus injection of high doses of exogenous PTH into the maternal or fetal organism did not affect fetal bone histology. In addition, no apparent defect of bone mineralisation or bone formation was found in fetuses of ricketic rats. Normal mineralisation in the offspring of uremic rats may be explained by fetal hyperphosphatemia and/or insensitivity of fetal (woven) bone mineralisation to vitamin D.Absence of fetal anemia (normal hematocrits, normal density of hematopoietic cells in the liver) in the presence of maternal anemia is presumably due to the insensitivity of fetal erythropoiesis to erythropoietin.With the support of Deutsche Forschungsgemeinschaft     

Clonal differentiation of uropathogenic Escherichia coli isolates of serotype O6:K5 by fimbrial antigen typing and DNA long-range mapping techniques

Escherichia coli isolates of serotype O6:K5 are the most common causative agents of cystitis and pyelonephritis in adults. To answer the question, as to whether strains of this particular serotype represent one special clonal group, out of a collection of 34 serotype O6:K5 isolates [Zingler et al. (1990) Zentralbl. Bakteriol Mikrobiol Hyg [A] 274:372–381] 15 strains were selected and analyzed in detail. The flagellar (H) antigen and the outer membrane protein (OMP) pattern were determined. Further serum resistance properties and the genetic presence and expression of other virulence factors, including hemolysin, aerobactin, P fimbriae, S/F1C fimbriae and type 1 fimbriae was evaluated. In addition the Xba-Imacrorestriction pattern of ten representative isolates was elaborated and the fimbrial (F) antigen type of the P fimbriae was determined, to obtain the complete O:K:H:F pattern. These analyses could clearly show that the O6:K5 isolates do not represent one clonal group. The XbaI-macrorestriction profiles were heterogeneous and marked differences in the hybridization patterns, using virulence-associated gene probes in Southern hybridization of long-range-separated genomic DNA, were observed among the strains. However, some of strains showed similarities in the genomic profiles, arguing for clonal groupings among the O6:K5 isolates. Interstingly the strains grouped together exhibited the same fimbrial F type that many indicate a coincidence of this phenotypic trait with clonality.In memoriam of Prof. G. Naumann