The role of interferon regulatory factor-1 in cytokine-induced mRNA expression and cell death in murine pancreatic beta-cells

Combinations of cytokines, including interleukin-1beta (IL-1beta) and interferon-gamma (IFN-gamma), induce nitric oxide (NO) production and cell death in pancreatic islet cells. We have previously shown that these events are preceded by increased expression of the transcription factor interferon regulatory factor-1 (IRF-1). We utilized an IRF-1 knockout mouse (IRF-1-/-) to investigate the role of IRF-1 in cytokine-induced islet- and beta-cell gene expression and cell death. For this purpose, pancreatic islets or FACS-purified beta-cells were isolated from wild type (wt) or IRF-1-/- mice. These cells were exposed for different time points to IL-1beta (50 U/mI), IFN-gamma (1,000 U/ml) and/or TNF-alpha (1,000 U/ml) before being harvested for determination of viability (by nuclear dyes) and mRNA expression (by RT-PCR with specific primers). Following a 24 hours exposure to IL-1beta or IL-1beta + IFN-gamma, pancreatic islets isolated from IRF-1-/- mice presented a 30-50% reduction in medium nitrite accumulation and inducible NO-synthase (iNOS) expression. Interestingly, both wt and IRF-1-/- purified beta-cells failed to produce NO in response to IL-1beta alone, but presented a similar increase in nitrite accumulation and iNOS expression following exposure to IL-1beta + IFN-gamma. The basal expression of MHC class I mRNA was lower in IRF-1-/- islet cells (30% reduction), but there was a similar 2-4 fold-increase in MHC expression in islet cells from both strains following cytokine exposure. IL-1beta induced serine protease inhibitor-3 (SPI-3; a putative cellular "defense" protein) mRNA expression in both wt and IRF-1-/- islets or beta-cells. IFN-gamma decreased the IL-1beta-induced SPI-3 expression in wt islets or beta-cells, but induced a 5-fold increase in the expression of this mRNA in IRF-1-/- islets cells, suggesting that IRF-1 mediates an inhibitory effect of IFN-gamma on SPI-3 expression. Treatment of whole islets for 3 days with IL-1beta + IFN-gamma induced significantly more islet cell death in wt than in IRF-1-/- mice (respectively 85 +/- 3% versus 31 +/- 4% dead cells). On the other hand, prolonged exposure (3-9 days) of FACS-purified beta-cells to the same cytokines, or a combination of 3 cytokines, led to a similar increase in cell death in both IRF-1-/- and wt islets. In conclusion, IRF-1 contributes to cytokine-induced islet iNOS expression and cell death. These effects are absent in purified beta-cells, suggesting that IRF-1 may mediate its effects on whole islets via activation of non-endocrine cells (e.g. macrophages and ductal cells) present in these preparations.

Donor-site morbidity comparison between endoscopically assisted and traditional harvest of free latissimus dorsi muscle flap

Endoscopically assisted harvest of free latissimus dorsi muscle flaps is being used more frequently in reconstructive microsurgery because it requires a smaller incision and leaves a more acceptable scar in the donor site. Donor-site morbidity was compared between groups of 22 latissimus dorsi muscles harvested using the endoscopically assisted technique and 26 using the traditional technique. The results revealed no statistically significant differences in the amount of intraoperative bleeding, the incidence of postoperative hematoma and seroma, and the incidence of donor-site wound infection as assessed by the surgeon. However, a patient questionnaire revealed that even though it did not reach a statistically significant difference, endoscopically assisted harvest of the latissimus dorsi muscle had less pain and allowed earlier and better movement of the upper extremity of the donor site. The patients' attitudes and feelings about the scar and overall satisfaction were also higher in the endoscopic group, which demonstrated a statistically significant difference.

Membrane permeabilization by small hydrophobic nonstructural proteins of Japanese encephalitis virus

Infection with Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, may cause acute encephalitis in humans and induce severe cytopathic effects in various types of cultured cells. We observed that JEV replication rendered infected baby hamster kidney (BHK-21) cells sensitive to the translational inhibitor hygromycin B or alpha-sarcine, to which mock-infected cells were insensitive. However, little is known about whether any JEV nonstructural (NS) proteins contribute to virus-induced changes in membrane permeability. Using an inducible Escherichia coli system, we investigated which parts of JEV NS1 to NS4 are capable of modifying membrane penetrability. We found that overexpression of NS2B-NS3, the JEV protease, permeabilized bacterial cells to hygromycin B whereas NS1 expression failed to do so. When expressed separately, NS2B alone, but not NS3, was sufficient to alter bacterial membrane permeability. Similarly, expression of NS4A or NS4B also rendered bacteria susceptible to hygromycin B inhibition. Examination of the effect of NS1 to NS4 expression on bacterial growth rate showed that NS2B exhibited the greatest inhibitory capability, followed by a modest repression from NS2A and NS4A, whereas NS1, NS3, and NS4B had only trivial influence with respect to the vector control. Furthermore, when cotransfected with a reporter gene luciferase or beta-galactosidase, transient expression of NS2A, NS2B, and NS4B markedly reduced the reporter activity in BHK-21 cells. Together, our results suggest that upon JEV infection, these four small hydrophobic NS proteins have various modification effects on host cell membrane permeability, thereby contributing in part to virus-induced cytopathic effects in infected cells.

Short- and long-term outcomes after percutaneous transluminal coronary angioplasty in chronic hemodialysis patients

The aim of this study was to obtain data on the outcomes of chronic hemodialysis patients who underwent percutaneous transluminal coronary angioplasty (PTCA). A retrospective chart analysis identified 31 such patients between August 1992 and October 1996. The mean follow-up period was 12.4 +/- 11.7 months. Angiographic success was achieved in 39 of 41 (95.1%) stenoses attempted. There were three in-hospital deaths. Clinical success was achieved in 28 of 31 patients (90%). Two of the 28 survivors were lost to follow-up. Recurrent angina developed within 6 months in 14 of 26 patients (53.8%). Eleven and 17 of the 26 patients (42.3% and 65.4%) died within 6 and 14 months, respectively, after the PTCA procedure. Ten of the 17 deaths (58.8%) were due to cardiovascular events. Our study suggests that PTCA is technically feasible with high angiographic success rate in chronic hemodialysis patients. In-hospital mortality rate and rate of recurrent angina are high. Long-term prognosis is poor.

Serosurvey for selected virus infections of wild carnivores in Taiwan and Vietnam

Serum samples from two leopard cats (Felis bengalensis) and four Formosan gem-faced civets (Paguma larvata taivana) in Taiwan, September 1995, and nine leopard cats in Vietnam, August and December 1997, were examined for the prevalence of antibodies against feline parvovirus, feline herpesvirus type 1, feline calicivirus and feline immunodeficiency virus. All civets and nine of 11 leopard cats were shown to have antibodies against feline parvovirus (FPV), and FPV's were isolated from mononuclear cells in the peripheral blood of the six leopard cats.

Interleukin 1beta increases arginine accumulation and activates the citrulline-NO cycle in rat pancreatic beta cells

Nitric oxide (NO) may contribute to pancreatic beta cell damage during the development of type 1 diabetes. Its formation can be triggered by cytokines which induce the expression of the inducible form of nitric oxide synthase (iNOS) in pancreatic islets. In the iNOS-catalyzed reaction, arginine is converted into citrulline and NO. Cellular NO formation may be regulated by the availability of arginine. Arginine can be provided extracellularly, entering the cell mainly through the cationic amino acid transporter system y+CAT, and intracellularly, by protein degradation or synthesis from citrulline (the citrulline-NO cycle). This study demonstrates for the first time that the citrulline-NO cycle is induced in FACS-purified rat beta cells exposed to interleukin-1beta(IL-1beta) and that extracellular arginine or citrulline is required for NO production by beta cells. Moreover, the accumulation of arginine was higher in IL-1beta-treated beta cells than in control cells.beta cells expressed mRNAs for the two y+CAT transporters CAT-2A and CAT-2B with no change in transporter expression after exposure to IL-1beta. It is concluded that the activation of the citrulline-NO cycle and an increase in arginine accumulation may be adaptive responses in cytokine-exposed beta-cells to assure an adequate arginine supply for continuous NO production in the presence of low extracellular arginine levels which may prevail during insulitis.

Spontaneous bacterial peritonitis in adult patients with primary nephrotic syndrome

BACKGROUND

Susceptibility to bacterial infection is a common problem in nephrotic patients. Spontaneous bacterial peritonitis, although characteristic of nephrotic children, is extremely rare in adults.

METHODS

A retrospective review was performed on all adult patients with the discharge diagnoses of primary nephrotic syndrome and spontaneous bacterial peritonitis treated between 1986 and 1998 at Chang Gung Memorial Hospital in Kaohsiung, Taiwan. Ten patients were included in this study, 9 of them men and one woman. The average age was 30.5 years.

RESULTS

All the patients had signs of active nephrosis and presented with diffuse abdominal pain, ascites, fever and/or chills. Thirty percent (3/10) of the causative pathogens were gram-positive bacteria and 60% (6/10) were gram-negative bacteria. One patient had sterile cultures. Seven patients recovered after antibiotic treatment for 1 to 2 weeks. Three patients died of septic shock.

CONCLUSION

Therefore, to improve patient outcome, it is essential to establish a diagnosis early and to initiate broad-spectrum antimicrobial therapy even before culture results are available.

Inhibition of human pancreatic islet insulin release by receptor-selective somatostatin analogs directed to somatostatin receptor subtype 5

Somatostatin (SS)-14 and SS28 are produced by pancreatic D cells and gut mucosa and inhibit pancreatic islet insulin and glucagon release. There are five distinct SS receptor (SSTR) subtypes, namely SSTR1-5, which show different affinities for SS14 and SS28. In order to identify the subtype responsible for inhibition of insulin release by human B cells, SSTR-selective SS analogs were tested in isolated human islets. Glucose-stimulated insulin secretion in human islets incubated for 1 hr at 20 mM glucose, and in islets cultured for 24 hr at a near-physiological (6.1 mM) glucose concentration, was inhibited (<50% of the control) by SSTR5-specific analogs and by SS14 and SS28. SS14, SS28, and different SSTR5 preferential analogs also inhibited islet amyloid polypeptide release during the 24-hr culture. On the other hand, a group of SSTR2-selective analogs failed to inhibit insulin release. Analysis by reverse transcription-polymerase chain reaction indicated that human islets express similar amounts of SSTR2 and SSTR5 mRNAs, while human pancreatic ductal cells express much lower levels of these mRNAs. In conclusion, our data suggest that SSTR5 is an important mediator of the insulin inhibitory action of SS in cultured human islets.

Effects of growth factors and trefoil peptides on migration and replication in primary oxyntic cultures

Restitution, the lateral migration of cells over an intact basement membrane, maintains mucosal integrity. We studied the regulation of migration and proliferation of enzyme-dispersed canine oxyntic mucosa cells in primary culture. Confluent monolayers were wounded and cultured in serum-free medium, and cells migrating into the wound were counted. [3H]thymidine incorporation into DNA was studied using subconfluent cultures. Considerable migration occurred in untreated monolayers; however, epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, basic fibroblast growth factor (bFGF), insulin-like growth factor I (IGF-I), two trefoil peptides, and interleukin (IL)-1beta further enhanced migration. The specific EGF receptor (EGFR) monoclonal antibody, MAb-528, inhibited both basal and TGF-alpha- or IL-1beta-stimulated migration, but not the response to trefoil peptide, bFGF, or IGF-I. Exogenous TGF-beta inhibited cell proliferation but did not alter migration. Immunoneutralization with anti-TGF-beta blocked the response to exogenous TGF-beta and produced a small enhancement of basal thymidine incorporation but did not attenuate basal or TGF-alpha-stimulated migration. In conclusion, endogenous EGFR ligands regulate proliferation and migration. TGF-beta inhibits mitogenesis; it did not upregulate migration in these cultures. Although bFGF, IGF-I, and IL-1beta enhance gastric epithelial migration, only IL-1beta acted in a TGF-alpha-dependent fashion.

Induction of p21(CIP1/Waf1) and activation of p34(cdc2) involved in retinoic acid-induced apoptosis in human hepatoma Hep3B cells

The biological activity of retinoic acid (RA) was examined in human hepatoma Hep3B cells. Under serum-deprived conditions, RA induced S/M-phase elevation and mitotic index increase within 24 h, followed by apoptosis. This RA-induced apoptosis was accompanied by p53-independent up-regulation of endogenous p21(CIPI/Waf1) and Bax proteins, as well as activation of p34(cdc2) kinase, and increase of Rb2 protein level and phosphorylation pattern. In addition, RA had no effect on the levels of Bcl-XL; Bcl-XS; cyclins A, B, D1, D3, or E; or Rb1 expression but markedly down-modulated Cdk2 kinase activity and reduced Cdk4 expression. RA also slightly delayed p27(Kip1) expression. Olomoucine, a potent p34(cdc2) and Cdk2 inhibitor, effectively blocked RA-mediated p34(cdc2) kinase activation and prevented RA-induced apoptosis. Furthermore, antisense oligonucleotide complementary to p21(CIP2/Waf1) and p34(cdc2) mRNA significantly rescued RA-induced apoptosis. Our data indicate that p21(CIP2/Waf1) overexpression may not be the only regulatory factor necessary for RA-induced apoptosis in human hepatoma Hep3B cells. RA treatment leads to Rb2 hyperphosphorylation, and p34(cdc2) kinase activation is coincident with an aberrant mitotic progression, followed by appearance of abnormal nucleus. This aberrant cell cycle progression appeared requisite for RA-induced cell death. These findings suggest that inappropriate regulation of the cell cycle regulators p21(CIP2/Waf1) and p34(cdc2) is coupled with induction of Bax and involved in cell death with apoptosis when Hep3B cells are exposed to RA.

Feline immunodeficiency virus subtype C is prevalent in northern part of Taiwan

The seroepidemiological survey of cats conducted in northern part of Taiwan in 1998 revealed that the positive rate of feline immunodeficiency virus (FIV)-infection was 21.9% (7/32) and the rate was much higher than those of previous reports. We succeeded in isolation of three strains of FIV from peripheral blood mononuclear cells of the blood samples. Nucleotide sequences of the env variable V3 to V5 region of the strains revealed that the isolates from distinct areas belong to subtype C. These data together with our previous report (Inada et al. 1997. Arch. Virol., 142: 1459-1467) indicate that FIV subtype C is prevalent in northern part of Taiwan.

Contribution of ductal cells to cytokine responses by human pancreatic islets

In type 1 diabetes, autoimmune destruction of pancreatic beta-cells has been attributed to cytokines released from infiltrating immunocytes. Exposure of isolated islets to cytokines leads to nitric oxide (NO) production, which can damage beta-cells. Because ductal cells are closely associated with human beta-cells, we examined whether they can contribute to this process. Isolated human ductal cells were cultured for 48 h with various cytokines. The combination of interleukin-1beta (IL-1beta) plus interferon-gamma (IFN-gamma) increased nitric oxide production 12-fold while stimulating mRNA expression of inducible nitric oxide synthase (iNOS). In this condition, 10-20% of cells positive for the cytokeratin-19 duct marker also stained positive for iNOS protein, whereas no positive cells were found in control preparations. Comparison of the magnitude of iNOS mRNA expression and nitric oxide production in these cells with that in isolated human islets suggests that >50% of total islet nitric oxide production might originate from associated ductal cells. It is concluded that ductal cells are a potential source of nitric oxide production in human islets infiltrated by cytokine-releasing immunocytes.

Junctional tachycardia during radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia: effects of autonomic blockade

INTRODUCTION

The autonomic nervous system richly innervates the peri-AV nodal region and may be activated during radiofrequency (RF) ablation for AV nodal reentrant tachycardia, resulting in the generation of junctional tachycardia. The purpose of this prospective study was to determine the role of the autonomic nervous system in the genesis of junctional tachycardia.

METHODS AND RESULTS

We compared the characteristics of junctional tachycardia in patients with (n = 10) and without (n = 10) autonomic blockade undergoing RF ablation for AV nodal reentrant tachycardia. Intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg) were used to block the autonomic nervous system. There were no differences in clinical variables and baseline electrophysiologic characteristics between the two groups except for slightly longer effective refractory periods of the fast pathway and of the atrium in the autonomic blockade group. The autonomic blockade shortened the baseline sinus cycle length and effective refractory period of the ventricle only but not other electrophysiologic characteristics of the AV node. The junctional tachycardia was observed during ablation in each patient, but its occurrence and cycle length, as well as numbers of consecutive junctional beats, were not altered by the autonomic blockade.

CONCLUSION

Our results indicate that the muscarinic and beta-adrenergic components of the autonomic nervous system play no role in the genesis of junctional tachycardia.

Validation of electrolytic-liquid tilt sensors for human motion measurement

The development of inexpensive, low-weight, no-invasive sensors that can be used to accurately measure human motion is important for the evaluation of biomechanical risk during a variety of industrial work activities. Electrolytic liquid tilt sensors that measure the angular position of an object relative to the gravitational force vector may provide a valuable means for assessing the postural demand of work tasks. For example, the biomechanical cost to the low back could be assessed during manual material handling activities, or the demand to the shoulders could be evaluated during overhead construction work. Tilt sensors were tested during static and dynamic activities, using isovelocity and isoacceleration dynamometers to move the sensor. The output voltage of the sensors was found to be linearly proportional to the angular deviation of the dynamometer within an 150 degree range (r > 0.99). During constant angular velocity and constant angular acceleration movements, the correlation between the output of the dynamometer and sensor was high and linearly dependent on angular position. Hence, the sensors are capable of accurate motion measurement during static and controlled dynamic movements. Because of the inertia of the liquid within the sensor, its output during sudden acceleration/deceleration may cause some artifact which requires more extensive investigation.

Benzodiazepine binding site-interactive flavones from Scutellaria baicalensis root

A benzodiazepine binding assay directed separation led to the identification of 3 flavones baicalein (1), oroxylin A (2), and skullcapflavone II (3) from the water extract of Scutellaria baicalensis root. Compounds 1, 2, and 3 interacted with the benzodiazepine binding site of GABAA receptors with a Ki value of 13.1, 14.6 and 0.36 micromol/L, respectively.

Radiofrequency and cryoablation of atrial fibrillation in patients undergoing valvular operations

BACKGROUND

Previous studies have shown that the maze operation can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation. The purpose of this study was to test the feasibility of the application of radiofrequency and cryoablation as an alternative to the classic maze operation.

METHODS

Twelve patients undergoing mitral valve procedures were included in this study. Radiofrequency and cryoablation were applied to create lesions in both atria to simulate the classic maze operation.

RESULTS

There were two surgical deaths. At the mean follow-up of 10.25 months for the remaining 10 patients; 6 were in sinus rhythm, 2 in atrial rhythm, 1 in paroxysmal atrial tachycardia, and 1 in atrial fibrillation. Doppler echocardiography at 6-month follow-up showed emergence of biatrial transport function in 3 patients and right atrial contractility in 8. At 12-month follow-up of 5 patients, Doppler echocardiography showed biatrial transport function in 3 and right atrial contractility in 4.

CONCLUSIONS

Our modified maze procedure during valvular operation is effective for achieving an acceptable success rate to restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation.

Immunohistochemical analysis of proliferating cells in a sterile labyrinthitis animal model

Inflammatory reactions within the cochlea lead to the formation of fibrotic tissue and bone. To determine which cells are involved in the proliferation of the inflammatory response within the cochlea, sterile labyrinthitis was created by inoculating keyhole limpet hemocyanin (KLH) into the scala tympani of systemically sensitized animals. Cellular proliferation was assessed immunohistochemically using the monoclonal antibody Ki-67. Proliferating cells were identified among inflammatory cells and fibroblasts within the matrix, as well as in endosteal cells lining the scala tympani. Inflammatory and potential osteoprogenitor cells were labeled as late as 6 weeks after inoculation, suggesting the absence of a strong immunosuppressive mechanism. Endosteal cells may proliferate and secrete the extracellular matrix used by the inflammatory cells to move within the cochlear scalae. They may also participate in the ossification of the inflammatory matrix.

Intercellular differences in interleukin 1beta-induced suppression of insulin synthesis and stimulation of noninsulin protein synthesis by rat pancreatic beta-cells

The normal pancreatic beta-cell population exhibits intercellular differences in its responsiveness to glucose. This cellular heterogeneity allows glucose to regulate, in a dose-dependent manner, total rates of insulin synthesis and release. It may also predispose to intercellular differences in susceptibility to dysregulating agents. The present study examines whether this is the case for interleukin 1beta (IL-1beta), which is known to suppress glucose-induced insulin synthesis and release. The effects of the cytokine were compared on beta-cell subpopulations with, respectively, high and low sensitivity to glucose. These subpopulations were separated on the basis of differences in the cellular metabolic responsiveness to an intermediate glucose concentration (7.5 mmol/liter) and then cultured for 20 h at 5 or 20 mmol/liter with or without IL-1beta. The suppressive action of IL-1beta (0.1 ng/ml) occurred predominantly in glucose-activated beta cells, reducing their high rates of insulin synthesis and release by more than 80%. Glucose-unresponsive cells became subject to a similar inhibition after their activation during culture at 20 mmol/liter glucose. On the other hand, IL-1beta induced or enhanced the expression of several noninsulin proteins in both subpopulations. The IL-1beta-stimulated expression of inducible nitric oxide synthase (iNOS) and heat shock protein 70 was more marked in the glucose-responsive subpopulation; that of heme oxygenase and Mn superoxide dismutase was comparable in the two subpopulations. Exposure to IL-1beta resulted in 10-fold higher medium nitrite levels in both subpopulations; this effect was prevented by the iNOS blocker, N(G)-methyl-L-arginine, which also prevented the IL-1beta-induced suppression in the glucose-responsive subpopulation. This study demonstrates that the cellular heterogeneity in glucose responsiveness predisposes to intercellular differences in the IL-1-induced suppression of insulin synthesis and release. While the cytokine induces the expression of noninsulin proteins such as iNOS in both glucose responsive and unresponsive cells, the subsequent nitric oxide production appears to predominantly affect glucose-stimulated functions in the glucose-activated cells.

Clinical diagnoses associated with histologic findings of fibrotic tissue and new bone in the inner ear

Fibrotic tissue or new bone occurs following inner ear inflammation, fracture, or surgery. The prevalence is unknown and was investigated using the National Temporal Bone, Hearing and Balance Pathology Resource Registry database. A search yielded 264 temporal bones with diagnoses of otosclerosis, tumor, Meniere's disease, meningitis, labyrinthitis, chronic otitis media, autoimmune disease, temporal bone fracture, or sensorineural hearing loss. All autoimmune cases contained some new bone, whereas only 20% to 30% of the labyrinthitis/meningitis cases were reported to contain new bone. Otosclerosis, Meniere's disease, and otitis media had relatively few cases containing new bone. Although new bone may derive from surgical trauma, it is also likely to be a result of the disease process. It seems that all these disease processes may contain a common feature that acts as a stimulus to induce fibrosis or bone growth in the inner ear.

Pharmacokinetic characteristics, efficacy, and safety of buccal testosterone in hypogonadal males: a pilot study

Transbuccal administration of drugs provides an easy route of administration. To test the safety and efficacy of a novel testosterone (T) product, we performed a randomized, double blind, placebo-controlled study in a parallel design. Men with serum T levels below 250 ng/dL were administered either an active buccal tablet containing 10 mg T (n = 7) or a buccal placebo tablet (n = 6) containing 3 mg pseudoephedrine HCl for taste matching. Men were studied while taking a standard T enanthate dose, after 6 weeks of a wash-out period, and after 8 weeks of therapy. The men were matched for age (mean +/- SD, 41 +/- 16 vs. 47 +/- 16) and type of hypogonadism (three primary testicular failures in each group, with the remainder having a central etiology). Acute pharmacokinetic testing showed peak serum hormone levels at 30 min, with a mean serum T concentration of 2688 +/- 147 ng/dL (range, 1820-3770 ng/dL). Levels returned to baseline in 4-6 h, resulting in a total T area under the curve level of 3865 ng/hn.dL, less than that using other available forms of T administration. Similar pharmacokinetics were observed for the hormone's metabolites, bioavailable T, free T, and estradiol. After 8 weeks of treatment, the results of nocturnal penile tumescence studies evaluating rigidity and circumference were significantly different from those in the placebo group (P < 0.05) and comparable to those during T enanthate therapy. In conclusion, transbuccal T therapy was sufficient to maintain normal sexual function while minimizing the total time of exposure to elevated circulating serum T levels.

Immunopathology of the inner ear: an update

We have reviewed the events of an inner-ear immune response. The perilymph contains antibody, presumably derived from the systemic circulation and CSF, which would allow for neutralization and help with opsonization and complement fixation. The endolymphatic sac contains immunocompetent cells capable of processing and presenting viral or bacterial antigen, potentiating the immune response, attacking the invaders directly or attacking infected cells, and developing immunoglobulin responses in situ. The early release of mediators such as IL-2 likely emanate from the endolymphatic sac and result in potentiation and regulation of the response and may assist in changes in the SMV, including expression of ICAM-1, which aid in the egress of immune cells from the systemic circulation. PMNs arrive first, followed by T cells and B cells, with secretion of specific antibody a relatively late event. Concomitant with the increase in cellular constituents is the formation of a dense extracellular matrix. The inner ear appears to have remarkable difficulty in clearing this matrix, ultimately resulting in ossification. The immune response is unfortunately deleterious to the inner ear, resulting in degeneration of the organ of Corti, stria vascularis, and spiral ganglion. Hearing loss is consistently seen following sterile and virally induced labyrinthitis. The inner ear also appears to be a target for autoimmune disease. While inner-ear damage has been described as part of non-organ-specific autoimmune disease, specific disease against the hearing apparatus is also likely. Experimental paradigms have allowed alterations of both the afferent and efferent limbs of this response; ultimately, with the hope that we can alter the course of the response and the subsequent damage in patients.

Inhibition of protein synthesis by reduced K+ in cultured endothelial cells

Total protein synthesis (as precipitable [3H] leucine incorporation) was determined under various experimental conditions to examine the relationship between cellular K+ and protein synthesis in human umbilical vein endothelial cells (HUVEC). We found that under normal external K+ concentration (5 mM), total protein synthesis was inhibited by cycloheximide and ouabain, with estimated values of IC50 of 0.41 microM and 0.60 mM, respectively. Cellular K+ concentrations were determined (102 +/- 4 mM for control cells) and found to be significantly increased (P < 0.01) by high external K+ (25 mM) and significantly decreased (P < 0.001) by low external K+ (0.5 mM) as well as by ouabain (2 mM). Under high external K+, total protein synthesis and the inhibitory responses of cycloheximide and ouabain were not altered. On the contrary, cellular K+ and protein synthesis were both further reduced by about half (P < 0.001) under low external K+. While ouabain further reduced cellular K+ by half (P < 0.001), protein synthesis was only slightly reduced (P < 0.05) under low external K+ and thus the relative reduction on protein synthesis was much less than that for cellular K+. These results indicate that while elevated intracellular K+ did not alter protein synthesis, reduced intracellular K+ correlated with a reduced cellular protein synthesis in HUVEC such that K+ may play a permissible role in the regulation of protein synthesis.

Paroxysmal atrial tachycardia with second-degree atrioventricular block

Paroxysmal atrial tachycardia with atrioventricular block usually indicates potentially dangerous overdigitalization, and serious heart disease is almost universally present. In this report, we describe a patient with a structurally normal heart who manifested spontaneously intra-atrial reentrant tachycardia with Wenckebach atrioventricular block in the absence of medications. In this patient, the longest atrial paced cycle length that induced atrioventricular nodal block was 390 ms, and the atrial cycle length during tachycardia ranged from 360 to 400 ms. The electrophysiologic study in our patient demonstrated that second-degree atrioventricular block during atrial tachycardia may occur in patients without structural heart diseases or taking any medication.