Developmental plasticity of respiratory behavior in Lymnaea

The authors investigated the contribution of experience to development and maintenance of pulmonary respiration in Lymnaea stagnalis. Respiration in L. stagnalis is bimodal via both the skin and the lung. Rearing snails from eggs to adulthood while preventing lung respiration (differentially reared snails) showed that L. stagnalis can develop and survive without pulmonary respiration. These snails were able to open and close their pneumostome when given the opportunity as adults. However, quantitative aspects of their respiratory behavior were significantly altered. Prevention of pulmonary respiration in adult, normally reared snails also induced behavioral changes. Comparison of these changes with those in differentially reared snails revealed specific developmental effects, which were reversible. Thus, this is a suitable model system for studying questions related to behavioral plasticity.     

Comparative dose-dependence study of FK506 and cyclosporin A on the rate of axonal regeneration in the rat sciatic nerve

The new immunosuppressant drug FK506 (Tacrolimus) increases the rate of nerve regeneration in vivo (Gold et al., 1994; Gold et al., 1995). In the present study, we have examined the dose-dependence of FK506's ability to enhance nerve regeneration. In the first set of experiments, rats received daily s.c. injections of FK506 (2 mg/kg, 5 mg/kg or 10 mg/kg) for 18 days after a sciatic nerve crush injury. Signs of functional recovery in the hind feet appeared earlier than in saline-treated control rats at all three FK506 dosage; recovery was maximally accelerated in the 5-mg/kg group. Light microscopy at 18 days after nerve crush revealed more regenerating myelinated fibers in FK506-treated rats than in controls; this was most apparent in the 5-mg/kg group. Morphometric analysis of axonal areas in the soleus nerve confirmed that axonal calibers were maximally increased in the 5-mg/kg group. In the second set of experiments, the rate of axonal regeneration was determined by radiolabeling the L5 dorsal root ganglion. Regeneration rate for sensory axons was maximally increased (by 34%) in the 5-mg/kg group. In contrast, cyclosporin A (10 or 50 mg/kg; dosages were selected on the basis of the 1/10 lower potency of cyclosporin A) did not significantly alter the rate of axonal regeneration. Cyclosporin A (50 mg/kg) also failed to increase functional recovery or axonal calibers in the soleus nerve. Because the two drugs share a common mechanism for producing immunosuppression (i.e., calcineurin inhibition), these results indicate that FK506's nerve regenerative property involves a distinct, calcineurin-independent mechanism.     

Modeling the Mechanical Behavior of Lung Tissue at the Microlevel

This paper is concerned with the development of a computational model of pulmonary alveoli against the background of ventilator-induced lung injuries. In order to quantify mechanical stimulation of alveolar tissue during artificial respiration, a detailed constitutive model of alveolar septa and an approach to consider interfacial phenomena is needed. For that purpose, a polyconvex hyperelastic material model formerly developed for arteries is adopted for pulmonary alveoli. Information about tissue morphology is inherently integrated into the constitutive model, therefore, establishing a connection between structure and function of the different septal constituents. Structural and interfacial dynamics are directly coupled at the alveolar surface. In order to take into account the complex behavior of surface active agents covering alveoli, a constitutive model considering dynamical changes of surface energy is employed.     

Effects of oleic acid-induced pulmonary edema on lung mechanics

In 25 rabbits anesthetized with pentobarbital sodium and paralyzed with succinylcholine chloride, we investigated the contributions of four factors that might cause the decreased static lung compliance found in oleic acid-induced pulmonary edema: 1) foam, 2) accumulation of fluid in the interstitial spaces, 3) loss of ventilatable units secondary to alveolar flooding, and 4) increased surface tension. Pulmonary edema, reflected by a 115% increase in mean post-mortem extravascular bloodless lung water content, decreased compliance 47% and tripled alveolar-arterial PO2 difference. Removing foam by degassing did not affect compliance measurements. Filling the lungs with saline caused similar changes in control and edematous animals. Because the 38% decrease in functional residual capacity was largely attributable to water accumulation, we concluded that loss of ventilatable units accounted for virtually all the decreased static lung compliance. The role of increased surface tension could not be determined directly but was considered relatively less important.     

The cellular and molecular basis of peripheral nerve regeneration

Functional recovery from peripheral nerve injury and repair depends on a multitude of factors, both intrinsic and extrinsic to neurons. Neuronal survival after axotomy is a prerequisite for regeneration and is facilitated by an array of trophic factors from multiple sources, including neurotrophins, neuropoietic cytokines, insulin-like growth factors (IGFs), and glial-cell-line-derived neurotrophic factors (GDNFs). Axotomized neurons must switch from a transmitting mode to a growth mode and express growth-associated proteins, such as GAP-43, tubulin, and actin, as well as an array of novel neuropeptides and cytokines, all of which have the potential to promote axonal regeneration. Axonal sprouts must reach the distal nerve stump at a time when its growth support is optimal. Schwann cells in the distal stump undergo proliferation and phenotypical changes to prepare the local environment to be favorable for axonal regeneration. Schwann cells play an indispensable role in promoting regeneration by increasing their synthesis of surface cell adhesion molecules (CAMs), such as N-CAM, Ng-CAM/L1, N-cadherin, and L2/HNK-1, by elaborating basement membrane that contains many extracellular matrix proteins, such as laminin, fibronectin, and tenascin, and by producing many neurotrophic factors and their receptors. However, the growth support provided by the distal nerve stump and the capacity of the axotomized neurons to regenerate axons may not be sustained indefinitely. Axonal regenerations may be facilitated by new strategies that enhance the growth potential of neurons and optimize the growth support of the distal nerve stump in combination with prompt nerve repair.     

Excitability increase in withdrawal interneurons after conditioning in snail

Membrane mechanisms of conditioning of the defensive reflex in the snails Helix pomatia and H. lucorum were investigated. Tapping on the shell was used as a conditioned stimulus, which under normal conditions produces no defensive reaction. A light blow of air into the pneumostome, called the defensive closure reaction, was used as an unconditioned stimulus. When a combination of conditioned and unconditioned stimuli were presented with 2-4 min interval, the reflex developed over a period of 3 days. The separate conditioned and unconditioned stimuli presented randomly were used as an active control. The electrical characteristics of identified interneurons involved in this defensive behavior were then measured in an isolated preparation. There was shown to be a decrease in the threshold of action potential generation from 20.5 to 16.3 mV and depolarizing shift of membrane potential from -62.1 to -57.0 mV. The electrical characteristics of withdrawal interneurons of active control snails did not differ from those in intact animals. All results show an increase in excitability of withdrawal interneurons after associative learning.     

An electron microscopic study of the processes of nerve regeneration after lyophilized nerve homografting

The objective of the present study was to investigate the role of the Schwann cell basal lamina in nerve regeneration. To achieve this goal, we observed the process of axonal regeneration within a lyophilized nerve graft, in which only the basal lamina of the Schwann cell persisted. Sciatic nerves were removed from rats and lyophilized to kill the Schwann cells and other components. These grafts were transplanted to rat sciatic nerve defects. The rats were then killed after lapses of time. We observed the processes of axonal regeneration using a transmission electron microscope. Regeneration of axons along the inner surface of the Schwann cell basal lamina was clearly seen. These results suggest that, if tubular basal laminae persist, Schwann cells are not always necessary, and axonal regeneration can be induced in the direction toward the basal lamina.     

Command neurons in the unconditioned reflex arc of the grape snail

Independent intracellular activation of any one of the five identified neurones elicits a behavioral act of pneumostome closing. Similar closing is evoked by adequate stimulation of different modalities. Comparison of unconditioned reflex properties and characteristics of responses of the studied cells leads to the conclusion that neurones under discussion are command elements for the unconditioned reflex. Command neurones respond to all sensory stimuli which can evoke reflex closing. There is a lot of synchronous EPSPs in their spontaneous activity, but no action potentials. A spike discharge of command neurones evoked by an adequate stimulus always precedes the effector movements but there is no action potentials during the pneumostome closing. Conclusion is made that the functional role of command neurones in the unconditioned reflex arc consists in evaluating the sensory input and in triggering motor programmes.     

Localization of MOC-1 cell surface antigen in small-cell lung carcinoma cell lines: an immunohistochemical and immunoelectron microscopic study

Expression of cell surface antigens of the neural cell adhesion molecule (N-CAM) class was recently shown to be shared by both fetal and neoplastic neuroendocrine cells, including those of the lung. We investigated the expression and localization of MOC-1 antigen on small-cell (neuroendocrine) lung carcinoma cell lines with immunohistochemical methods at the light (LM) and electron microscopy (EM) level and by Western blot. At LM level, using monoclonal antibody (MAb) MOC-1 with the ABC method and immunofluorescence, positive staining was observed on surfaces of cells from all tumor lines examined. Strongest immunostaining was found on cell surfaces of pulmonary small-cell carcinoma-derived cell line NCI-H69 with the majority of cells showing positive staining. An adherent variant of NCI-H69 cell line, H69V, exhibited positive staining in about 60% of cells, whereas only occasional cells of NCI-H727 cell line derived from pulmonary carcinoid tumor were positive for MOC-1 antigen. Western blot analysis confirmed these findings, showing a strong MOC-1-specific band in cell extracts of NCI-H69, with weaker band densities for H69V and NCI-H727. Immunoelectron microscopy (IEM) revealed that MOC-1 was not uniformly distributed on the outer surface of plasma membrane; immunogold particles appeared concentrated in areas of thick cell surface "fuzz" coating, surface microvilli, and in areas of cell-cell contact. In some cells, areas of plasma membrane invaginations and a few intracytoplasmic vesicles were also labeled, suggesting endocytosis. Surface labeling for SEM confirmed the finding of more dense labeling over the microvilli, cell membrane folds, and in areas of cell-cell contact. The cell lines derived from pulmonary neuroendocrine cell tumors can provide a useful model to study the role and function of neural adhesion molecules in pulmonary neoplasia and during lung development.     

Lobular low attenuation of the lung parenchyma on CT: evaluation of forty-eight patients

PURPOSE: Our goal was to analyze patients with pulmonary lobular low attenuation (LLA) on thin section CT with regard to the underlying pulmonary diseases and the dynamic changes occurring in the low attenuation regions during respiration. METHOD: Forty-eight consecutive patients with LLA on thin section CT were analyzed retrospectively. Forty-six patients (95%) had symptoms related to respiratory disease, such as productive cough (n = 25) and hemoptysis (n = 18). Only two patients, one with chronic pulmonary embolism and one with Takayasu arteritis combined with bronchiectasis, had pulmonary vascular disease. Six patients, four with bronchiectasis and two with vascular disease, were studied with dynamic CT during forced vital capacity maneuver. Attenuation values for LLA areas and adjacent lung were measured and time-density curves were plotted. RESULTS: Forty-one (85%) patients had bronchiectasis, typically in other than the regions of the LLA. Areas with proximal bronchiectasis showed low attenuation but without notable lobular distribution. Pulmonary vessels in the LLA areas were smaller than those of adjacent normal lung (n = 45). Of 22 patients who underwent pulmonary function tests, 15 had obstructive pattern of impairment. Respiratory dynamic CT showed expiratory air trapping in LLA areas in all six patients. The mean attenuation values of LLA areas were lower than those of the adjacent normal lung by 67 HU at end-inspiration and by 165 HU at end-expiration (p = 0.002). CONCLUSION: The majority of the patients with LLA shown by thin section CT had bronchiectasis elsewhere in the lung, and evidence of air trapping in the LLA was clearly demonstrated. Bronchiolar obstruction may be the most prevalent cause for the development of LLA.     

Recovery, work engagement, and proactive behavior: A new look at the interface between nonwork and work.

This study examined work-related outcomes of recovery during leisure time. A total of 147 employees completed a questionnaire and a daily survey over a period of 5 consecutive work days. Multilevel analyses showed that day-level recovery was positively related to day-level work engagement and day-level proactive behavior (personal initiative, pursuit of learning) during the subsequent work day. The data suggest considerable daily fluctuations in behavior and attitudes at work, with evidence that these are related to prior experience and opportunity for recovery in the nonwork domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complement depletion reduces macrophage infiltration and activation during Wallerian degeneration and axonal regeneration

After peripheral nerve injury, macrophages infiltrate the degenerating nerve and participate in the removal of myelin and axonal debris, in Schwann cell proliferation, and in axonal regeneration. In vitro studies have demonstrated the role serum complement plays in both macrophage invasion and activation during Wallerian degeneration of peripheral nerve. To determine its role in vivo, we depleted serum complement for 1 week in adult Lewis rats, using intravenously administered cobra venom factor. At 1 d after complement depletion the right sciatic nerve was crushed, and the animals were sacrificed 4 and 7 d later. Macrophage identification with ED-1 and CD11a monoclonal antibodies revealed a significant reduction in their recruitment into distal degenerating nerve in complement-depleted animals. Complement depletion also decreased macrophage activation, as indicated by their failure to become large and multivacuolated and their reduced capacity to clear myelin, which was evident at both light and electron microscopic levels. Axonal regeneration was delayed in complement-depleted animals. These findings support a role for serum complement in both the recruitment and activation of macrophages during peripheral nerve degeneration as well as a role for macrophages in promoting axonal regeneration.     

Role of vagus during exercise in thermal panting

In dogs anaesthetised with pentobarbitone sodium raising the body temperature from 37 degrees C during mild exercise increased the rate of respiration and pulmonary ventilation but decreased the tidal volume. Cold blocking the vagi during the exercise resulted in decrease in respiration rate and minute ventilation, but increase in tidal volume. At 40 degrees C body temperature vagal block was not effective in decreasing the respiration rate and minute ventilation, which may be due to stimulation of lung irritant receptors through hyperthermia.     

Slime-trail tracking in the predatory snail, Euglandina rosea.

Euglandina rosea, a predatory land snail, tracks prey and mates by following slime trails. Euglandina follow slime trails more than 80% of the time, following trails of their own species, but not those of prey snails, in the direction that they were laid. The attractive elements of prey slime are small, water-soluble compounds detected by specialized lip extensions. Although olfaction plays no role in trail following, strong odors disrupt tracking. Inhibition of nitric oxide synthase also disrupts slime trail following, suggesting a role for nitric oxide in neural processing of slime trail stimuli. Euglandina can be conditioned to follow novel trails of glutamate or arginine paired with feeding on prey snails. These experiments demonstrate that slime-trail tracking in Euglandina is a robust, easily measured behavior that makes a good model system for studying sensory processing and learning in a novel modality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails (Pleuroceridae: Juga spp.) from northern California

Ehrlichia DNA was identified by nested PCR in operculate snails (Pleuroceridae: Juga spp.) collected from stream water in a northern California pasture in which Potomac horse fever (PHF) is enzootic. Sequencing of PCR-amplified DNA from a suite of genes (the 16S rRNA, groESL heat shock operon, 51-kDa major antigen genes) indicated that the source organism closely resembled Ehrlichia risticii, the causative agent of PHF. The minimum percentage of Juga spp. harboring the organism in the population studied was 3.5% (2 of 57 snails). No ehrlichia DNA was found in tissues of 123 lymnaeid, physid, and planorbid snails collected at the same site. These data suggest that pleurocerid stream snails may play a role in the life cycle of E. risticii in northern California.     

The electrical characteristics of the command and motor neurons during the acquisition of a conditioned defensive reflex and the development of long-term sensitization in snails

The mechanisms of conditioning of the defensive pneumostome closure reflex and long-term sensitization were studied at the level of electrical characteristics of the command and motor neurons. A significant decrease in membrane and threshold potentials in the command neurons was observed after the acquisition of the defensive reflex and long-term sensitization. These potentials decreased to a greater extent in the snails subjected to conditioning after the sensitization. Changes in the critical depolarization level for the action potential generation and its amplitude were insignificant. Thus, the observed phenomena testify to an increase in membrane excitability of the command neurons. Similar changes were not found in the motor neurons.     

Inhaled nitric oxide in patients with cystic fibrosis during preoperative evaluation and during anaesthesia for lung transplantation

INTRODUCTION: Inhaled nitric oxide (iNO) has been recently used as pulmonary vasodilator without any systemic effects because of a rapid inactivation by haemoglobin. We studied haemodynamic and oxygenation effects during iNO administration in cystic fibrotic patients during preoperative evaluation and during anaesthesia for lung transplantation. METHODS: From March 1996 to November 1997, 35 patients received iNO (40 ppm) during preoperative evaluation in spontaneously breathing. 13 patients, who underwent double lung transplantation, received iNO (40 ppm) during the surgical procedures, after pulmonary artery clamping. RESULTS: In the preoperative evaluation a significant decrease of mean pulmonary artery pressure, pulmonary vascular resistance index and intrapulmonary shunt, with an increase of PaO2/FiO2, were observed during iNO administration, compared to baseline in 100% O2. During lung transplantation a significant decrease in intrapulmonary shunt was noted. All the transplants were successfully performed without cardio-pulmonary bypass. In all procedures, after iNO administration, we observed no modification of systemic haemodynamics. In conclusion, our study confirms the pulmonary effects of iNO without any systemic effects in patients affected by cystic fibrosis during preoperative evaluation and during anaesthesia for lung transplantation.     

The carcinogenicity of environmental tobacco smoke

Male strain A/J mice were exposed for 6 h a day, 5 days a week to environmental tobacco smoke (ETS) generated from Kentucky 1R4F reference cigarettes. Chamber concentrations were 87 mg/m3 of total suspended particulate matter (TSP), 246 p.p.m. of CO and 16 mg/m3 of nicotine. After 5 months, 33% of the ETS exposed and 11% of the control animals had one or several lung tumors; the difference was statistically not significant. A second group of animals exposed for 5 months to ETS was allowed to recover for another 4 months in filtered air. When they were killed, 85% of the ETS animals had lung tumors (average number per lung: 1.4 +/- 0.2), whereas in the control group 38% had lung tumors (average number of lung tumors in all animals 0.5 +/- 0.2). The differences in tumor incidence and multiplicity were statistically significant. More than 80% of all tumors were adenomas, the rest adenocarcinomas. When animals were pretreated with a carcinogen, lung tumor multiplicity was lower in the ETS exposed animals after 5 months compared with controls injected with a carcinogen and kept in air. However, after an additional 4 month recovery period in air, lung tumor multiplicities were the same in ETS plus carcinogen exposed mice as in carcinogen-treated air-exposed controls. Histopathologic and morphometric analysis of the lung tissue failed to reveal any differences between ETS exposed and control animals. However, immediately after ETS exposure, immunohistochemistry revealed increased staining for CYP1A1 in airway epithelia and lung parenchyma; following recovery in air, the staining disappeared again. Analysis of cell kinetics showed an initial burst of increased DNA synthesis in the epithelial cells of the airways and a smaller early positive response in the parenchyma. Feeding of butylated hydroxytoluene during ETS exposure did not modulate lung tumor development. It was concluded that ETS is a pulmonary carcinogen in strain A/J mice.     

Percutaneous fibrin glue therapy of meningeal cysts of the sacral spine

The release of extracellular proteases by the axonal growth cone has been proposed to facilitate its movement by digesting cell-cell and cell-matrix contacts in the path of the advancing growth cone. The serine protease plasminogen activator (PA) has been shown to be secreted and focally concentrated at axonal growth cones of cultured mammalian neurons. Thus, PAs are well-placed to play an active role in growth cone movement and axonal pathfinding in development and regeneration. We discuss recent findings that suggest that the biological action of these proteases is more complex than originally thought.     

Features of external respiration and pulmonary hyperemia in man during immersion

Reactions of external respiration on catheterization of main blood vessels were studied in healthy subjects following 12 hr and 5-6 day immersion. The purpose of the investigation was to detect respiratory signs of hyperemia in pulmonary circulation under these conditions. Results of the investigation were compared with the data of great vessel catheterization in patients of a cardiological clinic afflicted with cardiac diseases with lung hyperemia and lung tissue hyperhydration. The results obtained failed to confirm suppositions about elevated blood filling of the lung and a possible increase of lung tissue hydration during water immersion. Catheterization of great vessels in patients and healthy subjects in most cases leads to an increase of respiratory minute volume. In patients with cardiac diseases the respiratory minute volume grew with an adequate rise in breathing rate, respiratory volume and gas exchange parameters unaltered; this suggested excessive blood filling of the lung and resulting higher respiratory resistance. After immersion the healthy subjects displayed an utterly different pattern, i.e. the growth of their respiratory minute volume was provided exclusively by the growth of respiratory volume while breathing rate did not change and gas exchange increased. These observations were considered an evidence of hyperemia and hyperhydration of pulmonary tissue.