Blockade of acid sensing ion channels attenuates the exercise pressor reflex in cats

Although thin fibre muscle afferents possess acid sensing ion channels (ASICs), their contribution to the exercise pressor reflex is not known. This lack of information is partly attributable to the fact that there is no known selective in vivo antagonist for ASICs. Although amiloride has been shown to antagonize ASICs, it also has been shown to antagonize voltage-gated sodium channels, thereby impairing impulse conduction in sensory nerves. Our aim was to test the hypothesis that lactic acid accumulation in exercising muscle acted on ASICs located on thin fibre muscle afferents to evoke the metabolic component of the exercise pressor reflex. To test this hypothesis, we determined in decerebrate cats if amiloride attenuated the pressor and cardioaccelerator responses to static contraction, to tendon stretch and to arterial injections of lactic acid and capsaicin. We found a dose of amiloride (0.5 μg kg⁻¹; i.a .) that attenuated the pressor and cardioaccelerator responses to both contraction and lactic acid injection, but had no effect on the responses to stretch and capsaicin. A higher dose of amiloride (5 μg kg⁻¹, i.a. ) not only blocked the pressor and cardioaccelerator responses to lactic acid and contraction, but also attenuated the responses to stretch and to capsaicin, manoeuvers in which ASICs probably play no significant role. In addition, we found that the low dose of amiloride (0.5 μg kg⁻¹) had no effect on the responses of muscle spindles to tendon stretch and to succinylcholine, whereas the high dose (5 μg kg⁻¹) attenuated the responses to both. Our data suggest the low dose of amiloride used in our experiments selectively blocked ASICs, whereas the high dose blocked ASICs and impulse conduction in muscle afferents. We conclude that ASICs play a role in the metabolic component of the exercise pressor reflex.     

Gastrointestinal haemorrhage from a jejunal gangliocytic paraganglioma.

A case of jejunal gangliocytic paraganglioma is reported in a 54 year old woman who presented with brisk melaena. The tumour was not encapsulated, involved the mucosa and submucosa, and was composed of epithelial nests, spindle cells, and ganglion cells. These cells were mixed, giving carcinoid-like, paraganglioma-like, and ganglioneuroma-like patterns in different areas of the tumour. The lesion was excised locally and recovery was uneventful. Only four previous cases have been reported at this site.     

T cell developmental defects in 'viable motheaten' mice deficient in SHP-1 protein-tyrosine phosphatase. Developmental defects are corrected in vitro in the presence of normal hematopoietic-origin stromal cells and in vivo by exogenous IL-7

Defects in the gene that encodes SHP-1 protein tyrosine phosphatase result in multiple hematopoietic abnormalities and generalized autoimmunity in viable motheaten (me(v)) mice. These mice also exhibit early thymic involution and abnormalities in T cell development. Here, we describe the use of fetal thymic organ culture (FTOC) and bone marrow adoptive transfer to study the effects of SHP-1 deficiency on thymocyte development. Chimeric FTOC established with normal bone marrow placed onto deoxyguanosine-treated fetal thymic lobes or onto scid fetal thymic lobes generated T cells. Bone marrow from SHP-1-deficient me(v)/ me(v) mice generated decreased numbers of T cells in chimeric FTOC established using deoxyguanosine-treated thymi but generated normal numbers in chimeric FTOC established using scid thymi. However, scid fetal thymi seeded with me(v)/ me(v) bone marrow also exhibited morphological abnormalities and contained elevated numbers of macrophages. Addition of IL-7 to me(v)/ me(v) bone marrow-seeded scid FTOC led to increased cell numbers, particularly of macrophages. Intrathymic injection of IL-7 partially restored the ability of progenitor cells in me(v)/ me(v) bone marrow to populate the thymus of adoptive recipients. We conclude that abnormal T cell development in me(v)/ me(v) mice may in part be due to defects in the ability of bone marrow-derived accessory cells to provide bioavailable IL-7 to developing thymocytes.     

Entrainment of Intestinal Slow Waves with Electrical Stimulation Using Intraluminal Electrodes

The aim of this study was to investigate whether the intestinal stimulation would be feasible using a less invasive method: intraluminal electrodes. The study was performed in nine healthy hound dogs (15–26 kg). Four pairs of electrodes were implanted on the serosa of the jejunum at an interval of 5 cm with the most proximal pair 35 cm beyond the pylorus. An intestinal fistula was made 20 cm beyond the pylorus. Simultaneous recordings of intestinal myoelectrical activity were made for 2 h in the fasting state from both intraluminal and serosal electrodes. Various pacing parameters were tested. The frequency of the intestinal slow wave recorded from the intraluminal electrodes was identical to that from the serosal electrodes , p < 0.001), and so was the percentage of normal 17–22 cycles/min waves (95.8±33.9% vs 98.16±1.33%, r=0.96, p<0.01).p < 0.01). A complete entrainment of the intestinal slow wave was achieved in every dog with electrical stimulation using intraluminal ring electrodes. The effective pacing parameters were pulse width of 70 ms, amplitude of 4 mA and frequency of 1.1 IF (intrinsic frequency). The time required for the entrainment of the intestinal slow wave with intraluminal pacing was 25.0±2.1s. The maximum driven frequency was found to be 1.43±0.01 IF. The results reveal that intraluminal pacing is an effective and efficient method for the entrainment of intestinal slow waves. It may become a potential approach for the treatment of intestinal motor disorders associated with myoelectrical abnormalities. © 2000 Biomedical Engineering Society. PAC00: 8754Dt, 8719Ff, 8717Nn     

Isolation of the equine granulocytic ehrlichiosis agent, Ehrlichia equi, in tick cell culture.

The equine granulocytic ehrlichiosis agent, Ehrlichia equi, is closely related or identical to the human granulocytic ehrlichiosis (HGE) agent. Both are suspected of being transmitted by ticks. We have successfully isolated E. equi in a cell line, IDE8, derived from a putative vector, the tick Ixodes scapularis. Peripheral blood leukocytes from an experimentally infected horse were inoculated onto IDE8 monolayers. Cultures were incubated in a candle jar at 34 degrees C in tick cell culture medium with NaHCO3 and an organic buffer [3-(N-morpholino)-propanesulfonic acid] (MOPS). Within 2 weeks, infected cells were detected in Giemsa-stained culture samples, and the organisms subsequently spread to uninfected cells in the cultures. E. equi was passaged serially by transferring a portion of an infected culture to new cell layers every 2 to 3 weeks. The identity of the organisms was confirmed by PCR using oligonucleotide primers specific for E. equi and the HGE agent and by immunocytology. Homologous equine antibodies and human anti-HGE convalescent serum recognized E. equi grown in tick cell culture. Electron microscopy revealed electron-lucent and -dense ehrlichia-like forms developing within host cell endosomes. E. equi passaged twice in tick cell culture retained infectivity and pathogenicity for the equine host, as demonstrated by intravenous inoculation of a suspension of infected tick cells and subsequent reisolation from peripheral blood, in fulfillment of Koch's postulates. The horse developed severe clinical signs, i.e., fever, inappetence, thrombocytopenia, icterus, and limb edema, typical of granulocytic equine ehrlichiosis, within 1 week.     

Cytogenetics as an aid in the diagnosis of lymphomas

Multiple classifications of lymphomas are available. Generally, distinctions are made to identify low, intermediate, and high-risk groups. Histopathologic differentiation is at times difficult. The revised European-American lymphoma classification (REAL) uses histology, clusters of differentiation markers, histochemistry, and cytogenetics for definitive identification. This work reviews the karyotypic and FISH (fluorescent in situ hybridization) findings in some common lymphomas. B-Cell lymphomas, which make up approximately 85-90% of lymphomas, are associated with cytogenetic changes of +12, 13q14, 14q32, 2p11, and 22q13. Translocations help to support the diagnosis of follicular cell lymphoma t(14;18),(q32;q21), mantle cell lymphoma t(11;14)(q13;q32), and Burkitt's lymphoma t(2;8),t(8;14) and t(8;22). T-Cell lymphomas may show changes in 14q11,7p or 7q. Many of the lymphomas are characterized by complex karyotypic changes. Specific FISH probes are useful in determining characteristic or identifying marker chromosomes. Cytogenetic and FISH studies aid in the diagnosis, correct classification, and evaluation of therapy for a variety of lymphomas.     

Interleukin-2 directly increases albumin permeability of bovine and human vascular endothelium in vitro.

The direct effects of interleukin-2 (IL-2) on albumin permeability of cultured bovine pulmonary artery endothelial cell (BPAEC) and human arterial endothelial cell (HAEC) monolayers were studied. BPAEC were exposed to IL-2 (500 to 25,000 U/ml) for 4 h. The steady-state transfer rate of [125I]albumin across the BPAEC monolayer was 3.3 +/- 0.4%/h (n = 10) in control BPAEC (diluent alone), was significantly increased in BPAEC exposed to 500 U/ml of IL-2 (72 +/- 3% above control values, n = 6, P less than 0.02), and further increased in BPAEC exposed to 5,000 U/ml (60 +/- 2% increase above 500 U/ml values, n = 5, P less than 0.02). No further increase was noted after exposure to 25,000 U/ml of IL-2. Additionally, no further increase in [125I]albumin transfer rates was noted in BPAEC exposed to 5,000 U/ml of IL-2 for 24 versus 4 h. Similar changes were found using HAEC. Preincubation of HAEC with an anti-IL-2 low-affinity receptor antibody (anti-IL-2R alpha) inhibited the IL-2-induced permeability increase. Expression of IL-2R alpha receptors in HAEC incubated with 5,000 U/ml of IL-2 for 4 h was also found. Thus, IL-2 appears to have a direct effect on cultural arterial endothelial monolayers not requiring the presence of other cell types or serum proteins. IL-2-induced increases in endothelial macromolecular permeability may play an important role in the pathogenesis of the IL-2-induced vascular leak syndrome seen in vivo.     

The pathogenesis of Yersinia enterocolitica infection in gnotobiotic piglets

Yersinia enterocolitica is an important cause of enteritis and mesenteric adenitis in many countries. However the pathogenesis of the disease caused by this organism has not been fully elucidated. Most isolates from clinical material possess two independent properties associated with virulence whose relative contribution to the development of disease is not known. These are the ability to penetrate the intestinal wall, which is thought to be controlled by a plasmid gene, and the production of heat-stable enterotoxin, which is controlled by a chromosomal gene. In this study, we infected neonatal gnotobiotic piglets with strains of Y. enterocolitica expressing these two properties in various combinations. The suitability of the piglet model was shown in experiments in which piglets fed virulent Y. enterocolitica serogroup O3 developed a clinical illness related to the size of the inoculum, which was accompanied by intestinal lesions similar to those reported in naturally and experimentally infected people and animals. The results confirmed the key role of a 47 X 10(6)-mol. wt plasmid in the pathogenicity of Y. enterocolitica, but suggested that penetration of the intestinal wall may be governed by chromosomal rather than plasmid-borne genes. No role for enterotoxin in the pathogenesis of yersiniosis was shown, although there was evidence that enterotoxin may promote intra-intestinal proliferation of Y. enterocolitica, thus favouring increased shedding of bacteria and encouraging their spread between hosts.