Effect of fatigue on diaphragmatic function at different lung volumes.

The transdiaphragmatic pressure twitches (PdiT) in response to single maximal shocks delivered bilaterally to the phrenic nerves were recorded as a function of lung volume when the diaphragm was fresh and when fatigued. All relationships were linear and negatively sloped (all r greater than 0.85). From these relationships PdiT was found to decrease with fatigue more rapidly and to recover more quickly at high than at low lung volumes. Complete recovery of PdiT at all lung volumes was greater than 1 h. Contraction and relaxation rate constants of PdiT did not change significantly with fatigue. We conclude that fatigue affects diaphragm contractility more at high than at low lung volumes and that changes in diaphragm contractility are best reflected in the measurement of PdiT as a function of lung volume.     

Muscle activity and fatigue in the shoulder muscles during repetitive work. An electromyographic study

The amplitude distribution probability function (ADPF) and the power spectrum of the surface electromyogram from m. deltoideus anterior, m. infraspinatus and m. trapezius pars descendens were analyzed from 7 persons working at a pillar drill. Recordings were performed 6 times during a working day. The ADPF was analyzed from 2-3 work-cycles from each recording. The static contraction level was 11.0% MCV in m. deltoideus anterior, 8.5% MVC in m. infraspinatus, and 20.5% MCV in m. trapezius, without any change occuring throughout the day. When compared to previous suggested upper limits of ADPF levels, both the static and the medium contraction levels were too high in the performance of this particular task. The power spectrum of the EMG was analyzed during isometric contractions of the shoulder muscles. The mean power frequency decreased during the day in m. trapezius only, suggesting muscular fatigue in this area.     

Choosing between immunity and tolerance after transplantation

Transplantation of MHC disparate solid organ leads to activation of both innate and adaptive immune responses. These immune responses include both effector and regulatory limbs. Lymphodepletion and IL-2 blockade may control the acute alloimmune response in humans but may also limit the regulatory arm. Numerous cytokines involved in rejection appear to be critical for tolerance. TLRs, complement engagement can facilitate suppressive responses as well as effector responses. Facilitating antigen-specific tolerance while enabling robust immunity may require ex vivo manipulation of the immune system rather than relying on in vivo perturbations of the homeostatic process.     

Velopharyngeal motion after sphincter pharyngoplasty: a videonasopharyngoscopic and electromyographic study

Sphincter pharyngoplasty is a surgical procedure for managing velopharyngeal insufficiency after palatal closure. This procedure is intended to create an active diaphragm for velopharyngeal closure. The purpose of this study was to evaluate velopharyngeal motion after sphincter pharyngoplasty, by using selective electromyography and simultaneous videonasopharyngoscopy. Twenty-five patients who were subjected to sphincter pharyngoplasty from 1985 to 1996 were reviewed. All conditions were evaluated by using electromyography with simultaneous videonasopharyngoscopy. The following velopharyngeal muscles were examined: superior constrictor pharyngeus, palatopharyngeus, and levator veli palatini. The palatopharyngeus was included in the superiorly based surgical flaps inserted at the posterior pharyngeal wall. Twenty-three patients (92 percent) showed complete velopharyngeal closure. The two patients with residual velopharyngeal insufficiency showed a defect size of 20 and 25 percent. None of the patients showed electromyographic activity at the superiorly based flaps, indicating absence of activity of the palatopharyngeus muscles. However, all patients showed normal electromyographic activity at the superior constrictor pharyngeus and the levator veli palatini. Videonasopharyngoscopy demonstrated that lateral pharyngeal wall movements, which ranged from 25 to 40 percent, were related to strong electromyographic activity at the superior constrictor pharyngeus. It is concluded that the superiorly based pharyngeal flaps of the sphincter pharyngoplasty do not seem to create an active diaphragm for velopharyngeal closure. Moreover, the observed sphinctering seems to be passive, caused by the contraction of the superior constrictor pharyngeus.     

Non-invasive investigations of muscular fatigue: metabolic and electromyographic components

Muscle fatigue, which is defined as the decline in muscle performance during exercise, may occur at different sites along the pathway from the central nervous system through to the intramuscular contractile machinery. Historically, both impairment of neuromuscular transmission and peripheral alterations within the muscle have been proposed to be involved in the development of fatigue. However, according to the more recent studies, muscle energetics would have a key role in this process. Intramyoplasmic accumulation of inorganic phosphate (P(i)) and limitation in ATP availability are frequently proposed as the causative factors of fatigue development. Although attractive, these hypotheses have been elaborated on the basis of experimental results obtained in vitro and their physiological relevance has never been clearly demonstrated in vivo. In that context, non-invasive methods such as 31-phosphorus magnetic resonance spectroscopy ((31)P MRS) and electromyographic (EMG) recordings have been employed to understand both metabolic and electrical aspects of muscle fatigue under physiological condition. The main results of these studies are reviewed in the present paper.     

Increased plasma mannose binding lectin levels are associated with bronchiolitis obliterans after lung transplantation

Background

Long-term lung allograft survival is limited by bronchiolitis obliterans syndrome (BOS). Mannose binding lectin (MBL) belongs to the innate immune system, participates in complement activation, and may predispose to graft rejection. We investigated mannose binding (MBL) during cold ischemia and in tissue samples from explanted lungs with BOS, and assessed MBL and complement proteins in plasma post-lung transplantation relative to BOS staging.

Methods

MBL was detected by immunohistochemistry lung tissue at the time of cold ischemia and in samples with BOS. MBL was assayed in the peripheral blood of 66 lung transplant patients transplanted between 1990–2007.

Results

MBL localized to vasculature and basement membrane during cold ischemia and BOS. Patients further out post-lung transplant > 5 years (n = 33), had significantly lower levels of MBL in the blood compared to lung transplant patients < 5 years with BOS Op-3 (n = 17), 1738 ± 250 ng/ml vs 3198 ± 370 ng/ml, p = 0.027, and similar levels to lung transplant patients < 5 years with BOS 0 (n = 16), 1738 ± 250 ng/ml vs 1808 ± 345 ng/ml. MBL levels in all BOS 0 (n = 30) vs. all BOS Op-3 (n = 36) were 1378 ± 275 ng/ml vs. 2578 ± 390 ng/ml, p = 0.001, respectively. C3 plasma levels in BOS 0 (n = 30) vs. BOS Op-3 (n = 36) were 101 ± 19.8 mg/ml vs. 114 ± 25.2 mg/ml, p = 0.024, respectively.

Conclusions

MBL localizes within the lung during graft ischemia and BOS, higher levels of plasma MBL are associated with BOS Op-3 and < 5 years post-transplant, and higher level of plasma complement protein C3 was associated with BOS Op-3 clinical status. MBL may serve as a biomarker for poorer outcome post-lung transplantation.     

Quadriceps and hamstring isokinetic strength and electromyographic activity measured at different ranges of motion: a reproducibility study.

Isokinetic strength measurements of the quadriceps and hamstring that are commonly conducted using a 90 degrees range of motion (RoM) may involve some risk to specific knee patient groups. Testing these muscles at a much shorter RoM may reduce the risk but in order to render this method clinically acceptable the reproducibility of the derived test findings has to be established. Therefore the main objective of this study was to assess the reproducibility of isokinetic peak torque and normalized EMG scores of these muscles based on 90 degrees (0-90 degrees flexion, LR) and three successive short RoMs: 0-30 degrees (SR1), 30-60 degrees (SR2) and 60-90 degrees (SR3). Eight healthy subjects were tested three times with a 2 week between-session interval. All tests were performed on the dominant limb and consisted of maximal concentric and eccentric exertions. The velocities applied were 90 degrees /s for LR and 30 degrees /s for each of the SRs. Findings indicated no between-session improvement in strength. Based on the coefficient of variation the measurement error for all isokinetic strength scores remained stable throughout the testing sessions ranging 0.6-13.9% with the absolute majority of instances less than 10%. The reproducibility of the EMG scores was poorer ranging 1.5-25% and 0.5-19% for the quadriceps and hamstring, respectively. It is concluded that testing of knee muscles at short (30 degrees ) RoMs does not compromise the reproducibility of the strength or EMG scores derived from the commonly used RoM of 90 degrees . However, whereas strength was reproducible to within the accepted clinical standards, the corresponding EMG scores were characterized by a wider error band.     

Immune tolerance to a defined heterologous antigen after intrasplenic hepatocyte transplantation: implications for gene therapy.

Development of a host immune response against gene products expressed by genetically modified cells could be a serious limitation for gene therapy. During examination of whether site-specific differences in antigen presentation could regulate the host immune response, we observed an absence of antibodies against hepatitis B virus surface antigen (HBsAg) when HBsAg producing transgenic hepatocytes were transplanted into the spleen. Intrasplenic transplantation resulted in translocation of a large number of cells into the portal vascular bed and liver sinusoids. In these recipients, HBsAg secreted by the transplanted hepatocytes circulated indefinitely in the blood. In contrast, subcutaneous or intraperitoneal transplantation of the transgenic hepatocytes induced an anti-HBs response, followed by clearance of serum HBsAg. Rechallenge with HBsAg in a highly immunogenic form failed to break the tolerance in intrasplenic hepatocyte recipients even though these animals responded to another antigen (keyhole limpet hemocyanin). Immunization with HBsAg in intraperitoneal recipients of HBsAg producing hepatocytes further elevated anti-HBs titers. Our results indicate that hepatocyte transplantation into the portal vascular bed via injection into the spleen can confer immune tolerance to secreted heterologous antigens. This finding should have important implications for human gene therapy as well as for analyzing the mechanisms of immune tolerance.     

Transplantation tolerance and autoimmunity after xenogeneic thymus transplantation

Successful grafting of vascularized xenografts (Xgs) depends on the ability to reliably induce both T cell-independent and -dependent immune tolerance. After temporary NK cell depletion, B cell suppression, and pretransplant infusion of donor Ags, athymic rats simultaneously transplanted with hamster heart and thymus Xgs developed immunocompetent rat-derived T cells that tolerated the hamster Xgs but provoked multiple-organ autoimmunity. The autoimmune syndrome was probably due to an insufficient development of tolerance for some rat organs; for example, it led to thyroiditis in the recipient rat thyroid, but not in simultaneously transplanted donor hamster thyroid. Moreover, grafting a mixed hamster/rat thymic epithelial cell graft could prevent the autoimmune syndrome. These experiments indicate that host-type thymic epithelial cells may be essential for the establishment of complete self-tolerance and that mixed host/donor thymus grafts may induce T cell xenotolerance while maintaining self-tolerance in the recipient.     

Bilateral phrenic stimulation: a simple technique to assess diaphragmatic fatigue in humans

Transdiaphragmatic pressure (Pdi) and the rate of relaxation of the diaphragm (tau) were measured at functional residual capacity (FRC) in six normal seated subjects during single-twitch stimulation of both phrenic nerves. The latter were stimulated supramaximally with needle electrodes with square-wave impulses of 0.1-ms duration at 1 Hz before and after diaphragmatic fatigue produced by resistive loaded breathing. Constancy of chest wall configuration was achieved by monitoring the diameter of the abdomen and the rib cage with a respiratory inductive plethysmograph system. During control the peak Pdi generated during the phrenic stimulation amounted to 34.4 +/- 4.2 (SE) cmH2O and represented in each subject a fixed fraction (17%) of its maximal transdiaphragmatic pressure. After diaphragmatic fatigue the peak Pdi decreased by an average of 45%, amounting to 18.1 +/- 2.7 cmH2O 5 min after the fatigue run, and tau increased from 55.2 +/- 9 ms during control to 77 +/- 8 ms 5 min after the fatigue run. The decrease in peak Pdi and the increase in tau observed after the fatigue run persisted throughout the 30 min of the recovery period studied, the peak Pdi amounting to 18.4 +/- 2.8 and 18.9 +/- 3.3 cmH2O and tau to 81.3 +/- 5.7 and 88.7 +/- 10 ms at 15 and 30 min after the end of the fatigue run, respectively. It is concluded that diaphragmatic fatigue can be detected in man by bilateral phrenic stimulation with needle electrodes without any discomfort for the subject and that the decrease in diaphragmatic strength after fatigue is long lasting.     

Dissociation of hemopoietic chimerism and allograft tolerance after allogeneic bone marrow transplantation.

Creation of stable hemopoietic chimerism has been considered to be a prerequisite for allograft tolerance after bone marrow transplantation (BMT). In this study, we demonstrated that allogeneic BMT with bone marrow cells (BMC) prepared from either knockout mice deficient in both CD4 and CD8 T cells or CD3E-transgenic mice lacking both T cells and NK cells maintained a high degree of chimerism, but failed to induce tolerance to donor-specific wild-type skin grafts. Lymphocytes from mice reconstituted with T cell-deficient BMC proliferated when they were injected into irradiated donor strain mice, whereas lymphocytes from mice reconstituted with wild-type BMC were unresponsive to donor alloantigens. Donor-specific allograft tolerance was restored when donor-type T cells were adoptively transferred to recipient mice given T cell-deficient BMC. These results show that donor T cell engraftment is required for induction of allograft tolerance, but not for creation of continuous hemopoietic chimerism after allogeneic BMT, and that a high degree of chimerism is not necessarily associated with specific allograft tolerance.     

Partial tolerance and immunity after adoptive abrogation of transplantation tolerance in the rat

Lewis rats were rendered hematopoietic and lymphoid cell chimeras by injection of (LBN)F₁ hybrid cells at birth or following treatment with cyclophosphamide in adult life. The establishment of transplantation tolerance was indicated by acceptance of (LBN)F₁ skin grafts and specific unresponsiveness in graft vs. host reaction (GvHR) and mixed lymphocyte interaction (MLI) in vitro. Tolerance was abolished by adoptively transferred Lewis lymphocytes, and the loss of chimerism and recovery of specific reactivity by blood lymphocytes were monitored independently by mixed lymphocyte cultures. Recovery of competence to initiate GvHR by splenic and lymph node cells was monitored by the local renal graft vs. host technique. Both techniques measure essentially the proliferative response of certain lymphocytes to foreign cellular AgB antigens, and both detected a prolonged, but gradually weakening, state of partial tolerance to the AgB factors to which tolerance had originally been induced. During this phase of partial tolerance the former chimera rejects skin and lymph node cell grafts from (LBN)F₁ donors with alacrity, but in some cases accepts (LBN)F₁ kidney grafts. Cytotoxic antibodies appear in the serum soon after allogeneic chimerism is terminated. These results are interpreted to indicate that a state of partial tolerance exists among the cells which proliferate in response to certain AgB antigens in GvHR and MLI in the formerly tolerant chimera, and that a state of transplantation immunity (possibly to other determinants) coexists with this partial tolerance.     

Time factors in VDT-induced myopia and visual fatigue: an experimental study.

In an experimental design with two matched groups (n = 13 and n = 17) working 2 and 4 hr respectively, followed by a 15-min restitution time, the study examined the effect of continuous VDT work on 1) visual acuity, refraction and oculomotor functions (ZCSV: zone of clear, single vision) and 2) the effect of 15-min restitution time on the oculomotor functions (ZCSV). In both groups there were a significant reduction in visual acuity, refraction changes in myopic direction and reduced ciliar and vergence muscle capacity. The ZCSV changes were temporary and a 15-min restitution period restored approximately half of the ZCSV changes. There were no significant differences between 2 or 4 hr of VDT work on any of the variables examined.     

Respiratory function of intercostal muscles in supine dog: an electromyographic study

It is traditionally considered that the difference in orientation of the muscle fibers makes the external intercostals elevate the ribs and the internal interosseous intercostals lower the ribs during breathing. This traditional view, however, has recently been challenged by the observation that the external and internal interosseous intercostals, when contracting alone in a single interspace, have a similar effect on the ribs into which they insert. This view has also been challenged by the observation that the external and internal intercostals in a given interspace often change their length in the same direction during breathing. In an attempt to clarify the respiratory function of these muscles, we studied eight supine lightly anesthetized dogs during quiet breathing and during static inspiratory efforts. In each animal electromyographic (EMG) recordings from the external and internal interosseous intercostals were obtained in all interspaces from the second to the eighth, and selective denervations were systematically performed to ensure with complete certainty the origin of the recorded EMG activities. The external intercostals were only activated in phase with inspiration, whereas the internal interosseous intercostals were only activated in phase with expiration. These phasic EMG activities, however, were generally small in magnitude, and the muscles were often silent. Indeed, activation of the externals was always confined to the upper portion of the rib cage, whereas activation of the internals was limited to the lower portion of the rib cage. Internal intercostal activation always occurred sequentially along a caudocephalic gradient. These observations are thus compatible with the traditional view of intercostal muscle action.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in afferent and efferent phrenic activities with electrically induced diaphragmatic fatigue.

In anesthetized artificially ventilated cats, diaphragmatic fatigue was produced by direct muscle stimulation with trains of pulses for 30 min. Failure of contraction was assessed from decrease in the maximal relaxation rate of transdiaphragmatic pressure twitches. Motor activities (electromyogram and motor phrenic neurogram) were processed by fast-Fourier transform analysis, which provided the power spectrum density function (PSDF). The discharge frequency of diaphragmatic afferents was also measured. In control conditions (before fatigue), intra-arterial bolus injection of lactic acid enhanced tonically active diaphragmatic afferents, whereas it reduced the firing rate of afferent fibers activated in phase with diaphragmatic contraction or relaxation. The same sensory response pattern was observed with the development of diaphragmatic fatigue. Leftward shift in PSDFs of motor phrenic neurogram also occurred, but it preceded the failure of diaphragmatic contraction as well as the changes in the electromyogram's PSDF and afferent paths, which were closely associated with lengthening of both inspiratory and total breath durations. After section of the phrenic nerves, the motor phrenic response disappeared during the fatigue trial. This demonstrates the existence of complex reflex-induced changes in the ventilatory control during diaphragmatic fatigue. They seem to involve the participation of several types of phrenic afferents.     

Increased lung vascular permeability after arachidonic acid and hydrostatic challenge

Arachidonic acid (AA) metabolites are known to be potent vasoactive substances in the pulmonary circulation, whereas their influence on lung vascular permeability is still uncertain. We investigated the effect of AA bolus injection on the capillary filtration coefficient (Kf,C) of isolated rabbit lungs, recirculatingly perfused with Krebs-Henseleit albumin (1%) buffer. Kf,C was measured using repetitive sudden venous pressure elevations (7.5 Torr) and time zero extrapolation of the slope of the weight gain curve. It ranged from 1.3 to 2.4 cm3 X s-1 X Torr-1 X g-1 X 10(-4) in control lungs. Pulmonary arterial injection of AA (100 microM; in presence of 20 microM indomethacin to suppress pulmonary arterial pressure rise) during an acute hydrostatic challenge, but not at zero venous pressure, caused a greater than 10-fold increase in Kf,C. Vascular compliance was not altered. Additional experiments, performed under zero-flow conditions to avoid any ambiguity in microvascular pressure, corroborated the severalfold increase in vascular permeability, detectable within 3 min after AA application during acute hydrostatic challenge.     

Increased sensitivity of an adriamycin-resistant human small cell lung carcinoma cell line to mitochondrial inhibitors.

The energy metabolism of an atypical multidrug resistant human small cell lung carcinoma cell line (GLC4/ADR) was studied. The glycolytic rate was 30% reduced and the glucose-6-phosphate dehydrogenase activity 2-fold increased in GLC4/ADR compared to the parental sensitive line (GLC4). Although mitochondrial respiration activities were similar in both cell lines, GLC4/ADR was more sensitive to the antimitochondrial drugs doxycycline and oligomycin, while cross-resistance was observed for the glycolytic inhibitor 2-deoxyglucose and for the antimitochondrial drug rhodamine-123. Continuous incubation with doxycycline induced a dramatic reduction of mitochondrial mRNAs in both cell lines, whereas a strong reduction of the nuclear-coded mRNA for subunit IV of cytochrome c oxidase was induced in GLC4/ADR only. Incubation with doxycycline had an additive effect on the cytotoxicity of adriamycin in both cell lines. Thus, a form of collateral sensitivity to antimitochondrial drugs may exist in atypical multidrug resistant cell lines.