ERG alterations induced by sound

The existence of efferent neurons from the CNS to the retina mediating centrifugal effects is an old and much debated hypothesis. In order to test whether the human ERG can be influenced by another sensory input, we have recorded the retina response to light when a sound was presented simultaneously. It was found that the b-wave of the ERG increased when a flash was paired with a sound. The sound-induced increment of the b-wave showed the following characteristics: a) Short time course, b) No relation to the frequency and intensity of the sound, c) Habituation specific to the frequency of the sound, d) Adaptation when the sound lasted more than 2 sec, e) Dependence on localization cues of the sound and f) Enhancement by low doses and suppression by high doses of diazepam. Further experiments on rabbits showed that it is not suppressed by ether anesthesia, by local application of atropine or by cutting the external ocular muscles. The results suggest that this effect is brought about by a reticulo-retinal pathway, the function of which is most probably to control the input of the visual route.

Evidence for non genomic action of 17β estradiol on transepithelial resistance of human fetal membranes

BACKGROUND

The role of hormones in the transport mechanisms of human fetal membranes in pregnancy is unclear. Estrogens are essential hormones in pregnancy and they play an important role in the ion transport via membranes.

AIM

The aim of this study was to investigate the effect of 17β-estradiol on transepithelial electrical resistance in the human amniochorion.

MATERIAL AND METHODS

Specimens of human fetal membranes were obtained. 17β-estradiol, tamoxifen and their combination were added in an Ussing chamber. Transepithelial resistance was measured before and after the addition of each solution.

RESULTS

An increase in transepithelial resistance was seen after the addition of estradiol to both sides of the membranes. The effect was rapid with a peak at the 1st min of application and dose-depended. Tamoxifen, caused a similar effect but smaller in magnitude and shorter in duration. Tamoxifen in combination with estradiol inhibited only in part the action of estradiol.

CONCLUSIONS

These results suggest that estradiol induces a rapid increase of transepithelial resistance in human fetal membranes in vitro via a non-genomic pathway. It is possible those changes in transepithelial resistance play a role in the control of permeability of human amniochorion.

Effect of histamine on the electrophysiology of the human parietal pleura

INTRODUCTION

Histamine is involved in the pathogenesis of numerous diseases and regulates the permeability of different tissues. The aim of this study is to investigate the effects of histamine on the electrophysiology of human parietal pleura and the underlying mechanisms involved.

MATERIALS AND METHODS

Pleural specimens were obtained from patients subjected to thoracic surgery and were mounted in Ussing chambers. Histamine solutions (1μM to 1mM) were applied in native and pretreated specimens with dimetindene maleate, cetirizine, ranitidine, amiloride and ouabain. Trans-mesothelial resistance was determined (R(TM)).

RESULTS

Histamine induced a rapid R(TM) increase on the mesothelial (p = 0.008) and a decrease on the interstitial surface (p = 0.029). This effect was dose-dependent and was totally abolished by dimetindene maleate, cetirizine and amiloride and partially by ranitidine and ouabain.

CONCLUSIONS

Histamine induces acute electrochemical changes in human pleura mainly via interaction with the H(1) and partially with the H(2) histamine receptors. It also interferes with trans-cellular permeability and therefore may participate in pleural fluid recycling.

Permeability alterations after surgical trauma in normal rabbit peritoneum

BACKGROUND

To investigate whether surgical trauma in a rabbit adhesion formation model and the administration of normal saline (N/S), icodextrin (ID) and/or dimetindene maleate (DM) changes the permeability of the normal rabbit parietal peritoneum.

MATERIALS AND METHODS

A total of 45 female rabbits were operated on for adhesion formation and were euthanized 10 days later. In some rabbits, ID or N/S was instilled intraabdominally during operation, whereas in others DM was infused intravenously. In others, ID plus DM or no agent was used. Specimens were obtained postoperatively and were mounted between Ussing chambers. Amiloride was used to investigate Na(+) channels. Transmesothelial resistance (R(TM)) was determined as a permeability indicator.

RESULTS

Amiloride increased the R(TM) of both surfaces. Surgical trauma increased R(TM) and partially inhibited the effect of amiloride. ID and N/S increased R(TM) and inhibited the effect of amiloride. Use of DM did not change R(TM) and did not inhibit the effect of amiloride. Use of ID plus DM slightly increased R(TM), but the effect of amiloride was blocked.

CONCLUSIONS

Surgical trauma impairs the permeability of the normal rabbit parietal peritoneum. ID or N/S surmounted this effect, but DM did not, suggesting that surgical trauma is a diffuse process. Antiadhesion measures influence peritoneal physiology.

Insulin alters the permeability of sheep pleura

AIM

Insulin promotes ion transportation across epithelia, mainly kidneys, leading to water and electrolyte abnormalities, possibly causing 'insulin oedema syndrome', which rarely presents as pleural effusion. Direct stimulation of sheep pleura by insulin and the possible electrophysiology mechanisms involved were investigated.

MATERIAL AND METHODS

Sheep visceral and parietal pleural specimens were mounted between Ussing chambers. Insulin solutions (10 (-9) to 10 (-5) M), L-NAME, Nitroprussid sodium, amiloride and ouabain were used. Trans-mesothelial Resistance was determined. Immunohistochemistry for presence of Insulin Receptors was performed.

RESULTS

Insulin increased Trans-mesothelial Resistance within 1st minute when added mesothelially of visceral (p=0.008) and parietal pleura (p=0.046) for concentrations higher than 10 (-7) M. L-NAME or Nitroprussid sodium didn't but amiloride and ouabain inhibited insulin's effect. Immunohistochemistry revealed the presence of Insulin Receptors.

CONCLUSION

Insulin changes the permeability of sheep pleura by altering its electrophysiology and may interfere in pleural effusion formation. Involvement of Insulin Receptors may be suggested.

Rapid effect of progesterone on transepithelial resistance of human fetal membranes: evidence for non-genomic action

1. The factors that regulate human fetal membrane transport mechanisms are unknown. The aim of the present study was to investigate the effect of progesterone on transepithelial electrical resistance (R(TE)) in the human amniochorion. 2. Fetal membranes from uncomplicated term pregnancies were obtained immediately after vaginal or Caesarean deliveries. Intact pieces were mounted as planar sheets separating an Ussing chamber. Progesterone (10(-4) to 10(-7) mol/L), mifepristone (10(-4) to 10(-8) mol/L) and combinations of progesterone plus mifepristone were applied to the chambers facing the fetal or maternal sides of the membrane. The R(TE) was measured before and 1, 5, 10, 15, 20, 25, 30, 45 and 60 min after each solution was added (at 37 degrees C). The R(TE) was calculated in Omega.cm(2), according to Ohm's law. 3. The mean (+/-SEM) basal value of R(TE) before the application of any substance in all experiments was 29.1 +/- 0.4 Omega.cm(2). The net change in the R(TE) (Delta R(TE)) in relation to the basal value was calculated in each experiment. Progesterone, mifepristone and the combination of progesterone and mifepristone induced a rapid, surge-type increase in R(TE) during the 1st min on both sides of the membrane. The combination of progesterone plus mifepristone exerted a synergistic action. The effect was stronger on the fetal side than on the maternal side for all substances tested (P < 0.05). The highest Delta R(TE) during the 1st min on the fetal side was seen with the combination of progesterone plus mifepristone (4.0 +/- 0.3 Omega.cm(2)) and the lowest Delta R(TE) occurred with mifepristone (1.5 +/- 0.1 Omega.cm(2)). 4. The present results demonstrated that the R(TE) of human fetal membranes increases rapidly in response to progesterone. It is possible that changes in R(TE) play a role in the control of membrane permeability during pregnancy.

Low glucose level and low pH alter the electrochemical function of human parietal pleura

The aim of the present study was to investigate whether low glucose and pH level, which are usually measured in complicated pleural effusions, alter the electrochemical function of healthy human parietal pleura. Parietal pleural pieces were stripped from 66 patients during thoracic surgery and were mounted in Ussing chambers. Krebs' solutions containing different glucose levels (0, 40 and 100 mg) and balanced at different pH levels (7.4, 7.3 and 7.2) were added to the pleural cavity surface of the pieces. Transmesothelial potential difference was measured at various time-points as an electrophysiological variable and transmesothelial resistance (R(TM)) was calculated using Ohm's law. When normal-glucose Krebs at pH 7.45 was used, R(TM) remained unchanged over time, but when low-glucose Krebs was used, R(TM) decreased. Krebs without glucose caused the greatest decrease in R(TM). Use of low-pH Krebs decreased R(TM). The lower the pH of the Krebs, the faster the decrease in R(TM) and the greater the effect. The decrease in R(TM) was greater with low-pH than with low-glucose Krebs. Low glucose and low pH caused an additive decrease in R(TM). Low glucose concentration and low pH cause alteration of the electrochemical function of human parietal pleura and could act as agents that lead to further exudate progression.

Non-genomic effect of testosterone on airway smooth muscle

BACKGROUND AND PURPOSE

Recent studies on blood vessels have provided evidence that testosterone may exert direct effects on smooth muscle. However, an acute effect on airway reactivity has not been shown yet. The aim of this study was to assess the direct effect of testosterone on the responsiveness of male adult rabbit airway smooth muscle (ASM), precontracted with 10 microM acetylcholine, 10microM carbachol or 80 mM KCl.

EXPERIMENTAL APPROACH

Contractility studies of rabbit tracheal smooth muscle were performed.

KEY RESULTS

Testosterone at concentrations of or above 1 nM had a significant relaxant effect on ASM precontracted with acetylcholine or carbachol, but did not affect ASM precontracted with KCl. The mechanical removal of airway epithelium as well as the inhibition of NO synthetase (by 100microM L-NAME) reduced the relaxation caused by testosterone. The effect of testosterone was not altered by impairing prostanoid synthesis (by 10microM indomethacin). The nitric oxide donor, sodium nitroprusside, had the same relaxant effect on ASM precontracted with either carbachol or KCl. Inhibitors of androgen receptors (10microM flutamide) or DNA transcription (100microM actinomycin D) did not alter the effect of testosterone. Prolonged incubation of ASM with 100 nM or 100 microM testosterone for 24 or 48 h did not alter their responsiveness to acetylcholine. BSA-testosterone (1pM to 100nM) relaxed significantly ASM precontracted with carbachol. The mechanical removal of airway epithelium abolished the relaxant effect of BSA-testosterone.

CONCLUSIONS AND IMPLICATIONS

Testosterone relaxes precontracted ASM via an epithelium and NO-mediated way. This effect is mediated via a non-genomic pathway.

Effect of adrenaline on transmesothelial resistance of isolated sheep pleura

The effect of adrenaline on the transmesothelial resistance (RTM) of sheep's visceral and parietal pleura was studied using the Ussing chamber technique. Basal transmesothelial resistance of visceral pleura was found to be 20.71 +/- 0.31 Omega cm2, whereas that of parietal pleura was found to be 19.53 +/- 0.34 Omega cm2. Immediately after the addition of adrenaline (10(-7) M) both apically and basolaterally on the visceral and parietal pleura, these values were significantly increased (P < 0.05). Addition of the nonselective beta-receptor blocker, propranolol (10(-5) M), suppressed this effect in both visceral and parietal pleura, while addition of the nonselective alpha-receptor blocker, phentolamine (10(-5) M), partly suppressed the above-mentioned increase in the parietal pleura. In conclusion, our results show that adrenaline has a rapid effect on both pleurae. This rapid effect is mediated by the stimulation of beta-adrenergic receptors in the case of visceral pleura, while in the case of parietal pleura this effect seems to be due to a stimulation of alpha- and beta-adrenergic receptors. On the visceral pleura the effect of adrenaline vanishes after some minutes and on the parietal this effect is more permanent than the visceral's one, suggesting differences in the distribution of the adrenergic receptors between the visceral and parietal pleura.

Inhibition by mercuric chloride of aquaporin-1 in the parietal sheep peritoneum: an electrophysiologic study

The peritoneal mesothelium is a barrier to ion transport in peritoneal dialysis. In this study, we used Ussing-chamber experiments to investigate the effect of HgCl2, an aquaporin-1 inhibitor, on the transmesothelial electrical resistance (RTM) of isolated sheep parietal peritoneum. Peritoneal samples from the diaphragm of adult sheep were isolated immediately after the death of the animal and were transferred within 30 minutes to the laboratory in a cooled Krebs-Ringer bicarbonate solution (4 degrees C, pH 7.5) bubbled with 95% O(2)/5% CO2. A planar sheet of the parietal peritoneum was mounted in an Ussing-type chamber and HgCl2 (10(-4) mol/L) was added apically or basolaterally. The RTM was measured before and serially after the addition of the HgCl2. The entire experimental apparatus was held at 37 degrees C, because active ion transport is temperature-dependent. The results presented are the mean +/- standard error of 12 experiments. The control RTM (that is, before the addition of HgCl) was 19.3 +/- 0.38 omega x cm2. Addition of HgCl2 apically induced a decrease in the RTM to 16.25 +/- 0.86 omega x cm2 within 1 minute. When added basolaterally, HgCl2 action was similar, with a rapid reduction in the RTM to 18.1 +/- 0.51 omega x cm2 (p < 0.05). A clear association between the RTM and the active transmesothelial ion transport was shown in previous studies. In the present study, rapid action of HgCl2 on the permeability ofthe parietal peritoneum was observed, resulting in a reduction in the RTM Taken together, these findings indicate that inhibition of aquaporin-1 alters the ionic permeability of the parietal peritoneal membrane.

Therapeutic value of antidepressants in asthma

Laboratory and clinical data provide evidence that a biological linkage exists between asthma and depression. Cytokines are key molecules in both diseases. They promote allergic reaction as well as depressive symptomatology. Antidepressants may have a therapeutic role in asthma by suppressing production of proinflammatory cytokines, inducing production of anti-inflammatory ones and preventing their brain effects. Most antidepressants also induce adaptive changes in central monoaminergic neurotransmission, which itself might modulate immune reactivity and central actions of cytokines. Antidepressants may also have direct effects on the immune cells. Their impact on hypothalamus-pituitary-adrenal axis is discussed. Antidepressants are expected to terminate the cascade of inflammatory events in other inflammatory diseases as well. The use of antidepressants in experimental clinical trials in patients with asthma is suggested.

In vitro responsiveness of human post-menopausal myometrium to endothelin-1 and ovarian steroids

It has been shown in vitro that endothelin 1 (ET1) differentially affects the human myometrial contractility according to the hormonal profile of women. Our purpose was to test the hypothesis that ovarian steroids influence the ET1 induced myometrial contractility. We performed three types of experiments. Myometrial tissues were exposed to 17beta-oestradiol (E), progesterone (P), E plus P (E+P) in concentrations 10(-10)M, 10(-8)M, 10(-7)M, 10(-6)M and 10(-4)M (Type I), ET1 in concentrations 10(-10)M, 10(-9)M, 10(-8)M, 10(-7)M and 10(-6)M (Type II) and E+ET1, P+ET1 and E+P+ET1 in concentrations ranging from 10(-10)M to 10(-6)M (Type III). Tissue exposure to E, P and E+P did not significantly alter the pattern of spontaneous myometrial motility. ET1 (10(-6)M) induced a sustained long-lasting contraction, the initial part of which lasted 34 +/- 4 min, elevating the initial baseline by 190 +/- 20%. This was followed by ripples of gradually increasing amplitude with no regular contractions up to the end of the period of observation (120 min). Addition of P or E+P to ET1 markedly restricted (p<0.05) the elevation of initial baseline (P+ET1: 68 +/- 8%, P+E+ET1: 67 +/- 8%), and significantly shortened (p<0.01) the duration of the alterations (P+ET1: 21 +/- 3 min, P+E+ET1: 26 +/- 3 min). These results demonstrate the lack of any significant effect of E and P or their combinations on the pattern of spontaneous myometrial motility in post-menopausal women. However, P alone or in combination with E exerted an inhibitory action on ET1 -induced contractility on human post-menopausal myometrium. The physiological significance of these findings remains to be clarified.

Fetal sensitivity to testosterone, left-handedness and development of bronchial asthma: a new approach

In contrast to Geschwind, Behan and Galaburda (GBG) theory, there is strong evidence that inheritance through maternal line is responsible for the coexistence of asthma and left-handedness early in childhood. A new model that incorporates GBG's theory and maternal inheritance is proposed. This hypothesis suggests that maternal atopy is the most important factor in the evolution of asthma and that GBG's theory applies mainly in childhood. An inherited enhanced sensitivity of fetus to testosterone may be the underlying mechanism that leads to the development of bronchial asthma.

Diabetes mellitus and lung function

OBJECTIVES

To assess the nature of pulmonary dysfunction in type 1 diabetes and the relationship of pulmonary function tests to diabetic factors and complication.

SUBJECTS AND METHODS

Sixteen type 1 diabetic patients and 26 control subjects matched for age and sex were studied. We performed spirometry measurements and measured pulmonary diffusing capacity (DL(CO)) in sitting and supine position by the single-breath method corrected by alveolar volume (VA). Glycosylated hemoglobin (HbA(Ic)), retinopathy and microalbuminuria were included as parameters of metabolic control and diabetic complications.

RESULTS

Diabetic patients showed a significant reduction of the following pulmonary function tests (% predicted value) as compared with control subjects: total lung capacity (TLC, 92.6 +/- 14.5 vs. 113.9 +/- 17.5, p < 0.001), lung diffusing capacity in sitting position (DL(CO), 90.4 +/- 21.1 vs. 107.7 +/- 15.6, p = 0.004), lung diffusing capacity in supine position (DL(CO), 88.3 +/- 19.3 vs. 111.9 +/- 19.9, p = 0.001). The differences in diffusing capacity corrected by alveolar volume in sitting and supine position (DL(CO)/VA) were not significant. By changing the posture from sitting to supine position both diabetic patients and control subjects significantly increased DL(CO)/VA (103.4 +/- 17.7 vs. 112.7 +/- 22.3, p = 0.046 and 99.5 +/- 13.4 vs. 114.4 +/- 13, p < 0.001, respectively). There was no correlation between pulmonary function tests and diabetic complications.

CONCLUSION

These data indicate that type 1 diabetic patients showed reduced TLC and DL(CO), features of pulmonary restrictive dysfunction. There was no correlation between abnormal pulmonary function and the presence of other diabetic complications.

Indoor maternal smoking doubles adolescents' exhaled carbon monoxide

The aim of this study was to evaluate the effects of indoor smoking. Exhaled carbon monoxide (CO) concentrations were measured on a CO monitor by a vital capacity manoeuvre in three groups of adolescents: non-smokers with non-smoking families, non-smokers with smoking mothers, and smokers. Each group included eight families. Smokers had higher exhaled CO (mean +/- SD, 35.67 +/- 14.62 ppm) than non-smokers with smoking mothers (6 +/- 2.5 ppm) and non-smokers (2.37 +/- 0.56 ppm), late in the evening (21.00 h). The levels of exhaled CO in non-smoking adolescents doubled if their mothers smoked.

CONCLUSION

Exhaled CO can be used as an indicator of indoor smoking. Maternal smoking plays a major role in the health of adolescents.

Effect of amiloride in human and sheep parietal pleura

The fluid and solute transport properties of human parietal pleura were studied and compared with sheep parietal pleura in vitro. The pleura was mounted as a planar sheet between Ussing-type chambers. The results presented are the mean values of nine different experiments. The transepithelial electrical resistance (R(TE)) of both pleurae species was measured before and after the addition of amiloride in both sides of pleura. The R(TE) for human was 25.74 +/- 1.23 Ohm x cm(2), while for the sheep it was 38.18 +/- 0.83 Ohm x cm(2). The addition of amiloride to the serosal bathing solution increased the R(TE) of human pleura to 30.48 +/- 1.01 Ohm x cm(2) and sheep pleura to 40.32 +/- 0.82 Ohm x cm(2), while amiloride had no effect on the basolateral side. From the above, it is strongly suggested that the human pleura seems to be more leaky than sheep pleura. Although the R(TE) was increased in both pleurae, the elevation in human pleura was significantly higher, thus results from experiments in sheep pleura could only partly be extrapolated in human pleura.

Rapid effects of 17beta-estradiol and progesterone on sheep visceral and parietal pleurae via a nitric oxide pathway

We investigated the effects of 17beta-estradiol and progesterone on transepithelial electrical resistance (R(TE)) in sheep visceral and parietal pleurae. Specimens of intact pleurae from adult female sheep were used. The samples were transferred to the laboratory within 30 min after death of the animal in a Krebs-Ringer solution at 4 degrees C. The pleura was then mounted as a planar sheet in Ussing-type chambers, and electrical measurements were made. There was an increase in R(TE) in all of the samples examined after addition of 17beta-estradiol and progesterone in visceral and parietal pleurae. This increase was rapid within 1 min, lasted for ~15 min, returned to the basal level within 30-45 min, and was dose dependent. Tamoxifen, an estrogen receptor antagonist, did not significantly eliminate the effect of 17beta-estradiol. Furthermore, no steroid receptors were identified in cytosolic preparations of visceral and parietal pleura with ligand binding assays. The estrogen- and progesterone-induced increase in R(TE) in both visceral and parietal pleurae was affected by addition of an inhibitor of nitric oxide synthase. Indeed, previous administration of N(omega)-nitro-L-arginine methyl ester prevented the increase in R(TE) by 17beta-estradiol and progesterone. These results suggest that 17beta-estradiol and progesterone induce an increase in R(TE) in both visceral and parietal pleura and thus alter the transepithelial permeability. The effect of steroids may be accounted for by rapid release of nitric oxide in pleura.

Magnesium as a relaxing factor of airway smooth muscles

In the search for effective treatment of a life-threatening asthma attack, intravenous magnesium infusion has been studied in asthmatic patients because of its potential effect to reverse bronchospasm and improve pulmonary function. To determine whether magnesium sulfate inhibits airway smooth muscle contraction and the possible mechanism of its action, in vitro experiments were performed on rabbit tracheas. Tracheal muscle strips were obtained from 12 rabbits. Initially, the muscle strip was pretreated with a solution containing MgSO4 (concentrations 10(-4) to 2 M) and 85 mM KCl. The response curve of the muscle was recorded. Application of the above solution led to a 40% relaxation at a magnesium concentration of 10(-1) M. The time to peak and to wash-out remained unchanged, and fixed to 66.6 and 123.3 sec, respectively, not influenced by magnesium concentration. On a second phase, the muscle strip was pretreated with KCl alone, and only after a full contractile response was obtained did we add 10(-1) M MgSO4, which led to full relaxation. We follow the same protocol using 10(-4) M acetylcholine (ACH). In this case, simultaneous application of 10(-1) M MgSO4 caused a 55.1% decrease in muscle contraction and a 60% decrease in time to peak. On a second phase, we added magnesium as we did with KCl, but without the same result. Magnesium caused a full relaxation when the constrictor agent was KCl, but a residual contraction was observed when the constrictor was ACH. Based on the knowledge that ACH and KCl cause Ca2+ influx into the cells and subsequent contraction by acting on different Ca2+ channels, we concluded that magnesium inhibits Ca2+ influx by blocking the voltage-dependent calcium channels.

The influence of altitude in bronchial asthma

BACKGROUND

Some asthmatic children living in mountain areas experience significant improvement in daily symptoms and in the degree of bronchial obstruction. The aim of this study is to investigate the effect of altitude on the prevalence and morbidity of childhood bronchial asthma.

METHODS

A questionnaire regarding the history and symptoms of asthma was distributed to 874 children aged 6-12 years, to be completed by their parents with the help of their pediatrician. A total of 583 children lived at sea level, 180 at an altitude between 501 and 800 meters, and 111 at an altitude between 801 and 1,200 meters. All children with recurrent cough, shortness of breath, wheezing, and a history of bronchial asthma were considered to have bronchial asthma.

RESULTS

The prevalence of childhood bronchial asthma in the mountains (800-1,200 meters) was twice as low as that at sea level (15.8% of children) (p <0.01). Parental smoking was more frequent in children who lived at sea level than in the mountains. Additionally, consumption of fish and oranges was more frequent at sea level. Children with asthma who lived in the mountains were absent fewer days from school per year (0.2) and had fewer nights with dyspnea per year (0.5) than asthmatic children who lived at sea level (1.6 days and 25 nights, respectively).

CONCLUSIONS

Bronchial asthma in children who live at high altitudes is characterized by low prevalence and low morbidity.

Effects of SNP, ouabain, and amiloride on electrical potential profile of isolated sheep pleura

The fluid and solute transport properties of pleural tissue were studied by using specimens of intact visceral and parietal pleura from adult sheep lungs. The samples were transferred to the laboratory in a Krebs-Ringer solution at 4 degrees C within 1 h from the death of the animal. The pleura was then mounted as a planar sheet in a Ussing-type chamber. The results that are presented in this study are the means of six different experiments. The spontaneous potential difference and the inhibitory effects of sodium nitroprusside (SNP), ouabain, and amiloride on transepithelial electrical resistance (R(TE)) were measured. The spontaneous potential difference across parietal pleura was 0.5 +/- 0.1 mV, whereas that across visceral pleura was 0.4 +/- 0.1 mV. R(TE) of both pleura was very low: 22.02 +/- 4.1 Omega. cm2 for visceral pleura and 22.02 +/- 3.5 Omega. cm2 for parietal pleura. There was an increase in the R(TE) when SNP was added to the serosal bathing solution of parietal pleura and to the serosal or mucosal bathing solution in visceral pleura. The same was observed when ouabain was added to the mucosal surface of visceral pleura and to either the mucosal or serosal surface of parietal pleura. Furthermore, there was an increase in R(TE) when amiloride was added to the serosal bathing solution of parietal pleura. Consequently, the sheep pleura appears to play a role in the fluid and solute transport between the pleural capillaries and the pleural space. There results suggest that there is a Na+ and K+ transport across both the visceral and parietal pleura.

Insulin NO-dependent action on airways smooth muscles

In order to find out how insulin acts on airway smooth muscle and which mechanisms could be involved, we studied the effect of insulin on contraction induced, first, by KCl and, second, by Acetylcholine (Ach), before and after epithelium removal, and finally in the presence of N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Tracheal smooth muscle strips from 24 rabbits, 6 being used for each experiment. Each muscle strip was pretreated with a solution containing either 80 mM KCl or 10(-5) Ach and increasing doses of insulin (range 10(-10)--10(-5) M) in the presence or absence of 10(-4) M L-NAME. A reference curve for contraction evoked by 80 mM KCl or 10(-5) M Ach in the presence or absence of 10(-4) M L-NAME was recorded each time before the pretreatment mentioned above. Insulin evoked a concentration-dependent inhibition of tracheal smooth muscle contraction, induced by 80 mM KCl or 10(-5) M Ach. After epithelium removal, insulin (10(-8), 10(-7) M) evoked statistically significant increases to the contractions induced by 10(-5) M Ach compared to the contractions induced by 10(-5) M Ach and insulin in the presence of epithelium (P < 0.05). These increases were higher when 10(-4) M l-NAME was added to the bath (P < 0.05). In conclusion, these results indicate that insulin inhibits tracheal smooth muscle contraction by acting on epithelium and releasing NO.

In vitro effects of endothelin-1 on the contractility of myometrium obtained from pre- and postmenopausal women

This study was conducted to evaluate the responsiveness of human nonpregnant myometrium to endothelin 1 (ET1) (10(-10) M-10(-6 )M) and KCl (80 mM) in relation to the hormonal profile of the women, who were allocated into three groups: group 1, premenopausal follicular phase, n=14, group 2, premenopausal luteal phase, n=20, and group 3, postmenopausal women, n=12. At a concentration of 10(-6 )M, ET1 in both groups 1 and 2 induced very low ripples of high frequency (group 1: 80+/-14%, n=5, group 2: 314+/-63%, n=11; P<0.05 compared with the pretreatment frequency) which lasted significantly longer in group 2 (29+/-2 min, n=10, P<0.05) than in group 1 (20+/-2 min, n=5), increasing the basal tone (group 1: 57.9+/-6%, n=5, group 2: 64.4+/-4%, n=6), the amplitude of myometrial contractility (group 1: 1.2+/-0.07 g, n=5, group 2: 1.6+/-0.1 g, n=7, P<0.05) and the area under the contractility curve (AUC; group 1: 8.4+/-1.1 gxmin, n=6, group 2: 11.9+/-1.6 g x min, n=11). In group 3, ET1 (10(-6 )M) created a sustained long-lasting contraction (initial phase: 43+/-6 min, n=6) characterized by the complete obliteration of spontaneous contractility with no ripples at all, and increasing significantly (P<0.05) the amplitude of myometrial contractility (2.8+/-0.5 g, n=6), the AUC (24.7+/-3.3 g x min, n=6), as well as the basal tone (183.6+/-21%, n=6) compared with the two premenopausal groups. In all three groups KCl exposure induced an initial rise (mean amplitude value: 1.1 g) followed by a relaxation phase to the primal baseline level (mean duration value: 12 min). Addition of ET1 (10(-6 )M) to KCl (80 mM) induced a similar pattern of contractility to that evoked by ET1 alone which, compared with KCl alone lasted significantly longer (P<0.05) in all three groups (group 1: 20+/-2 min, n=6; group 2: 23+/-2 min, n=6; group 3: 35+/-3 min, n=5). In group 3, the percentage change in basal tone was significantly smaller following KCl than after the combination of KCl plus ET1 (149+/-16%, n=5; P<0.01), indicating a different mechanism of contractility between KCl and ET1. These results demonstrate for the first time differences in myometrial response to ET1 between pre- and postmenopausal women. It is suggested that KCl and ET1 affect uterine contractility through different mechanisms and that ovarian steroids may play a regulatory role in human uterine responsiveness to ET1.

Noxious gases in greenhouses

The concentration of NO(2) and SO(2) was measured in a commercial greenhouse from 23/9/1999 25/01/2000. The measurements showed that the level of the two gases is very high in the greenhouse atmosphere. Lung function tests in 42 workers showed that temporary work did not influence significantly the respiratory health status.

Lung function in Gypsies in Greece

The relationship between lung function and smoking and dietary habits was examined in 121 Gypsies (62 males, 59 females) who were 14-70 y of age and who lived in Greece. All were examined clinically, after which they all participated in spirometry tests. Half of the study group had abnormal (< 80% of predicted) forced vital capacity, 36.4% had abnormal (< 80% of predicted) forced expiratory volume in 1 sec, and 5% had serious lung function disturbances (forced vital capacity < 50% of predicted). Approximately 70% of subjects were smokers, and their diets were rich in alcohol and meat; they ate very few salads and oranges. Consequently, decreased lung function might be a major health problem in Gypsies in Greece. Organization of preventive health strategies should improve the overall health of this study group.

Left-handedness and inheritance of bronchial asthma

A statistically significant difference in mean laterality quotients of 15 asthmatic and 106 nonasthmatic children showed a coexistence of left-handedness and asthma early in life. It is suggested that this phenomenon is not only a fetal event as the Geschwind-Galaburda hypothesis claims but it is mainly based on maternal line inheritance.

Chronic bronchitis in rural and industrial areas

The purpose of the study was the determination of prevalence of chronic bronchitis in people older than 55 years in rural and industrial areas. 569 people over 55 years old living in central Greece were studied. A protocol was completed for each patient that included smoking habits, job, age, weight, drugs used for respiratory system and symptoms. A chest radiograph was taken for each patient. Each patient was submitted to three trials of dynamic spirometry. The best results were used for the study. The patients who complained of expectoration for three months for two continuous years and had obstructive pattern of lung function were diagnosed with chronic bronchitis. 9.6% of the subjects in rural area and 17.1% in industrial area were diagnosed with chronic bronchitis. Half the COPD patients never visited a doctor for this specific problem and were diagnosed for the first time. One out of three examined people had abnormal lung function. Consequently, more than one out of ten people older than 55 years have chronic bronchitis. Industrial exposure seems to double the risk for chronic bronchitis.

Airway responsiveness: role of inflammation, epithelium damage and smooth muscle tension

The purpose of this study was the effect of epithelium damage on mechanical responses of airway smooth muscles under different resting tension. We performed acetylcholine (ACh) (10(-5) M)-induced contraction on tracheal strips from 30 rabbits in five groups (0.5, 1, 1.5, 2 and 2.5 g) before and after epithelium removal. At low resting tension (0.5-1.5 g), the epithelium removal decreased the ACh-induced contractions. At 2 g resting tension, the epithelium removal increased the ACh-induced contractions of airways with intact epithelium about 20%. At 2.5 g resting tension, the elevation of contraction is about 25% (P<0.01). Consequently, after epithelium loss, the resting tension determines the airway smooth muscles responsiveness. In asthma, mediators such as ACh act on already contracted inflammatory airways, which results in additional increase of contraction. In contrast, low resting tension, a condition that simulates normal tidal breathing, protects from bronchoconstriction even when the epithelium is damaged.

Ventilation distribution during histamine provocation

The following is the abstract of the article discussed in the subsequent letter:

Verbanck, S., D. Schuermans, A. Van Muylem, M. Paiva, M. Noppen, and W. Vincken. Ventilation distribution during histamine provocation. J. Appl. Physiol.83(6):1907–1916, 1997.—We investigated ventilation inhomogeneity during provocation with inhaled histamine in 20 asymptomatic nonsmoking subjects. We used N2 multiple-breath washout (MBW) to derive parameters S cond and S acin as a measurement of ventilation inhomogeneity in conductive and acinar zones of the lungs, respectively. A 20% decrease of forced expiratory volume in 1 s (FEV1) was used to distinguish responders from nonresponders. In the responder group, average FEV1decreased by 26%, whereas S cond increased by 390% with no significant change in S acin. In the nonresponder group, FEV1 decreased by 11%, whereas S cond increased by 198% with no significant S acin change. Despite the absence of change in S acin during provocation, baseline S acin was significantly larger in the responder vs. the nonresponder group. The main findings of our study are that during provocation large ventilation inhomogeneities occur, that the small airways affected by the provocation process are situated proximal to the acinar zone where the diffusion front stands, and that, in addition to overall decrease in airway caliber, there is inhomogeneous narrowing of parallel airways.

Epithelium-dependent regulation of airways smooth muscle function. A histamine-nitric oxide pathway

The airway epithelium is responsible for the production of a number of arachidonic acid and non-prostanoid inhibitory factors. Epithelium synthesises nitric oxide (NO) which may be important in regulating the function of airways smooth muscles. We studied in vitro the effect of histamine (100 nM-100 microM) which increases the NO release on rabbit airway smooth muscles induced by 80 mM KC1 in the presence or not of 10(-5) Methylene blue (MB) (inactivator of guanylate cyclase) or N(G)-monomethyl L-arginine (L-NMMA), a NOS inhibitor. All experiments were done in tracheal muscle strips from 28 rabbits with epithelium and after epithelium removal. The additional use of histamine (1 microM) on KC1 contraction induced a relaxation of 10% of the initial contraction. The additional use of L-NMMA decreased the relaxation to 5% of initial contraction. MB rather than L-NMMA increased the contraction significantly (p<0.01). Epithelium removal increased the contraction induced by KC1 (80 mM) and histamine (1 microM) by about 30% (p<0.001). NO release especially from epithelium regulates the airways smooth muscle functions. Damage to the epithelium may contribute to an increase in airways sensitivity, observed in asthma.

Benign postpartum pleural effusion

The conditions of labour appear to favour the development of pleural effusion. The frequency of postpartum pleural effusion was investigated in this study using thoracic ultrasonography. Thirty one postpartum and 22 healthy nonpregnant women of the same age-group were examined, both supine and seated, via an intercostal approach. Seven of the 31 (23%) postpartum women had pleural effusion within 1-24 h of normal delivery. None of the nonpregnant women had pleural effusion. No correlation was found between postpartum pleural effusion and age, weight-gain during pregnancy, duration of labour, use of intravenous fluid, or oxytocin administration. Pleural effusion seems to be a common finding postpartum, but of no clinical significance.

Azelastine effects on electrical and mechanical activities of guinea pig papillary muscles

The effects of azelastine, a new anti-asthmatic drug under clinical investigation, were studied on both normal fast action potentials (APs) and slow APs using conventional microelectrode techniques in guinea pig papillary muscles (superfused with oxygenated Tyrode solution at 37 degrees C). Slow APs were induced by either 10(-7) M isoproterenol, 10(-5) M histamine, db-cAMP (3 mM) or 10 mM TEA, in the presence of 25 mM [K]o to voltage inactive the fast Na+ channels. At 10(-5) M, azelastine depressed the maximum rate of rise (+Vmax) of the slow APs and the force of contraction. At 3 X 10(-5) M, azelastine further reduced +Vmax and the amplitude of the slow APs; complete abolishing of slow APs and contractions occurred at 10(-4) M. Upon washout of the drug, automaticity appeared. In the presence of 10(-4) M azelastine, increasing the [Ca]o concentration from 1.8 to 3.6 and 5.4 mM caused partial recovery of the slow APs and contractions. The fast APs were also depressed by azelastine. At 10(-5) and 3 X 10(-5) M, azelastine reduced +Vmax and the AP duration at 50% repolarization (APD50) of the fast APs. Complete block of the fast APs and suppression of contractions were observed after 30 min at 10(-4) M azelastine. After 3-5 h of washout, excitability recovered; however, +Vmax was depressed and APD90 was prolonged. It is concluded that azelastine inhibits the slow Ca2+ channels and the fast Na+ channels. The slow recovery suggests that the drug may accumulate inside the cells, and exert a prolonged inhibitory effect on contraction.

Acetylcholine inhibition in rabbit sinoatrial node is prevented by pertussis toxin

The effects of acetylcholine (ACh) were examined on the naturally occurring slow action potentials (APs) of the isolated, organ-cultured, spontaneously beating sinoatrial (SA) node of the rabbit, in the presence or absence of pertussis toxin. The sensitivity of the SA-node preparations to ACh was not altered after 24 h incubation in organ culture medium. Activation of the muscarinic receptor hyperpolarized the cells and reduced the frequency of spontaneous activity at low concentrations (1 X 10(-6) and 3 X 10(-6) M), and completely abolished automaticity at higher concentrations (1 X 10(-5) M). However, stimulated activity was maintained. Increased concentrations (1 X 10(-4) M) of ACh completely abolished excitability. When the SA-node preparations were cultured in the presence of 0.5 micrograms/mL pertussis toxin, concentrations of ACh as high as 1 X 10(-4) M had no effect on the AP parameters and frequency of spontaneous activity. The results indicate that inactivation of G proteins by pertussis toxin caused inhibition of the ACh effects on the automaticity of the SA node. In addition, the blocking effect of ACh to the naturally occurring slow APs was also inhibited by pertussis toxin. We conclude that in the rabbit SA node, the effects of ACh on automaticity and on the slow channels are mediated by G protein.

Calcium dobesilate and transmembrane potential in canine cardiac cells. A preliminary study

The electropharmacological effects of calcium 2,5-dihydroxybenzene sulfonate (calcium dobesilate, Doxium) were studied by means of intracellular microelectrode technique in order to measure the changes in action potentials (A.ps.) in dog isolated cardiac Purkinje fibers and the adjacent ventricular tissue superfused with Tyrode's solution. The addition of 25 mmol/l of calcium dobesilate to the superfusate suppressed automaticity in spontaneously functioning preparation. The frequency of the action potentials was decreased and their duration increased with elevation and prolongation of their plateau phase. These effects were produced in both Purkinje and adjacent ventricular fibers and they were reversed by washing out with Tyrode's solution. Addition of calcium (25 mmol/l) restored automaticity in preparation in which spontaneous activity had been previously arrested by tetrodotoxin (10(-4) mol/l). Calcium dobesilate-induced action potentials were slow i.e. with low dV/dtmax and were abolished by verapamil (10(-5) mol/l). Calcium dobesilate increased the contractile force in both normally working and tetrodotoxin-arrested preparations. These findings suggest that calcium dobesilate acts on the myocardial cell by promoting transmembrane calcium influx during the plateau phase through activation of the slow inward calcium current.

New dihydropyridine drug, nilvadipine, blocks the calcium slow action potential in rat-cultured aortic smooth muscle cells

The effects of the dihydropyridine analogs, nilvadipine (FR-34235) and mesudipine, on the electrical activity of rat aortic smooth muscle cells in culture (reaggregates) were compared with the calcium antagonist verapamil. Nilvadipine blocked the tetraethylammonium-induced action potentials (APs), whose inward current is carried almost exclusively by Ca2+ through voltage-dependent slow channels. The effects of nilvadipine were dose dependent, and nilvadipine had a more potent inhibitory effect on the K+-induced contraction than on the norepinephrine-induced contraction of rabbit aorta. The ED50 value for blockade of the K+-induced contracture by nilvadipine was 6.4 X 10(-8) M, and complete blockade of the Ca2+ slow channels occurred at 10(-8) M. Mesudipine also inhibited the Ca2+ slow channels in cultured vascular smooth muscle cells in a dose-dependent manner; elevation of the [Ca]O from 1.8 to 5.4 mM partially restored the slow APs. The order of the inhibitory action on the Ca2+-dependent slow APs was: nilvadipine greater than mesudipine greater than verapamil. The inhibition of Ca2+ influx during excitation by the drugs can account for their vasodilatory properties.

Electropharmacological effects of a new dihydropyridine analog on isolated guinea pig papillary muscles and Purkinje fibers

The effects of a new dihydropyridine, FR-34235, were compared with those of the dihydropyridine, nifedipine, and verapamil on the normal fast action potentials (APs), slow APs, and contractions of guinea pig papillary muscles and Purkinje fibers. FR-34235 (10(-6) M) blocked the contractions of papillary muscles superfused with normal Tyrode solution within 10-12 min. Maximal upstroke velocity (+Vmax) and overshoot of the fast APs were not affected, whereas the AP durations at 50 and 90% repolarization (APD50 and APD90) were shortened. The effects of FR-34235 on the fast APs and contractions were reversed within 10 min on washout. To determine the effects of the calcium antagonists on slow APs, the fast Na+ channels were inactivated by partial depolarization (to approximately -45 mV) by elevated [K]0, and isoproterenol (10(-6) M) or histamine (10(-5) M) was used to induce slow APs on stimulation. Nifedipine (10(-7) M) and verapamil (2 X 10(-6) M) completely blocked the slow APs. FR-34235 depressed (3 X 10(-8) M) and blocked (10(-7) M) the slow APs in a frequency-dependent manner. The effects were reversed by elevated [Ca]0 or washout of the drug. The contractions accompanying the slow APs were depressed and blocked in parallel with the depression of +Vmax. In guinea pig Purkinje fibers, FR-34235 had no significant effect on the fast AP parameters but produced a marked depression of automaticity. FR-34235 also blocked the slow APs of the Purkinje fibers in a frequency-dependent manner; all drug effects were reversed within 10 min on washout.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of calcium antagonistic drugs on the electrical activity of rabbit sino-atrial node

The effects of several calcium antagonistic drugs (slow channel blockers), mesudipine, FR-34235 (nilvadipine), nifedipine, and verapamil, were compared on the naturally-occurring slow action potentials (APs) of the isolated spontaneously-contracting sinoatrial (SA)-node of the rabbit. Mesudipine, at 1 X 10(-8) M, had little or no effect on the AP parameters and beating frequency. At 1 X 10(-7) M, mesudipine depressed the amplitude, + Vmax and frequency of the APs. A higher concentration of mesudipine (3 X 10(-7) M) completely blocked the slow APs. The concentration of FR-34235 required for 50% depression of Vmax was 3 X 10(-8) M, and complete block required 1 X 10(-7) M. The verapamil and nifedipine concentrations required for complete block were 1 X 10(-6) M and 1 X 10(-7) M, respectively. The cells blocked by these drugs were depolarized to about -40 mV. Cells blocked and depolarized by the drugs responded to intensive field stimulation with a transient after-hyperpolarization, followed by damped oscillations. When [Ca]o was elevated from 1.8 mM to 5.4 mM, full block required a higher concentration of mesudipine (1 X 10(-6)M) and FR-34235 (1 X 10(-6)M). The order of potency of the drugs tested was: nifedipine = FR-34235 greater than mesudipine greater than verapamil. The effects of mesudipine, FR-34235, and nifedipine were easily reversible upon washout for 10 min, whereas those of verapamil required longer periods. The results indicate that the slow channel blockers, mesudipine, FR-34235, nifedipine, and verapamil depress the APs and automaticity of the SA-node.

Synthesis and biological activity of carboxy verapamil, a new derivative of verapamil

New analogues of the calcium antagonist verapamil (alpha-isopropyl-alpha-[(N-methyl-N-homoveratryl)-gamma-aminopropy l] -3,4-dimethylphenyl acetonitrile) were synthesized. Carboxy verapamil (alpha-isopropyl-alpha-[(N-methyl-N-homoveratryl)-gamma -aminopropyl]-3,4-dimethylphenyl acetic acid) was prepared by hydrolysis of the nitrile group of verapamil. Derivatives of carboxy verapamil could be synthesized by coupling substituents onto the carboxylic acid moiety. All syntheses can be prepared on a microscale. The biological activity of carboxy verapamil was compared with that of verapamil by testing their ability to block the isoproterenol-induced slow action potential (APs) in guinea pig papillary muscle. Carboxy verapamil was about 10-fold less potent than verapamil in blocking the slow APs. The IC50 for carboxy verapamil was about 6 X 10(-6) M. Furthermore both drugs had a similar frequency dependency. The effects of carboxy verapamil were rapidly reversed upon washout, suggesting that this drug may act on the external surface of the myocardial plasma membrane. In contrast, verapamil-induced effects are slowly reversed upon washout and it may exert is primary effects on the inner surface of the plasma membrane. Carboxy verapamil, because of its dipolar charge character may not readily penetrate into myocardial cells.

Comparison of the effects of several calcium antagonistic drugs on the electrical activity of guinea pig Purkinje fibers

The effects of several slow channel blockers were compared on the normal fast action potentials (APs) and the slow APs of guinea pig Purkinje fibers. In spontaneously-firing Purkinje fibers perfused with normal Tyrode solution, mesudipine (analog of nifedipine) at 10(-7) and 10(-6) M, had no significant effect on the fast AP parameters (at 5 X 10(-6) M, excitability was abolished due to depolarization to about -45 mV). Washout of the drug rapidly (within 3 min) repolarized the preparations and restored automatic activity. In order to determine the effect of the calcium antagonists on the slow APs, the fast Na+ channels were inactivated by partial depolarization (to about -45 mV) by perfusing with 20 mM K+-Tyrode solution and isoproterenol (10(-6) M), or histamine (10(-5) M) were used to induce slow APs upon stimulation. Verapamil (10(-6) M) and nifedipine (10(-7) M) completely blocked the slow APs. Mesudipine at 10(-8) and 4 X 10(-8) M depressed the Vmax, amplitude and duration of the slow APs and abolished excitability within 11 min at 10(-7) M. At 10(-7) M, mesudipine blocked the slow APs earlier (within 3 min) at higher stimulation frequency (from the usual drive rate of 0.5-1.5 Hz). Lowering the stimulation frequency to 0.1 Hz restored the slow APs; however, the mesudipine block was independent of the stimulating frequency after 20 min. The dose/response curve for the mesudipine effect was shifted to the right in high Ca2+ concentration (5.4 mM). Washout of mesudipine and nifedipine restored the slow APs within 15 min, whereas verapamil required about 1 h. The results indicate that mesudipine has potent Ca2+ slow channel blocking properties in Purkinje fibers. Mesudipine and nifedipine are about ten times more potent than verapamil. This effect is not mediated by beta-adrenergic receptor antagonism, because the histamine-induced slow APs were also blocked.