Air-breathing rhythm in Clarias batrachus (Linn.): modulatory role of eyes, pineal and exogenous melatonin.

Effects of enucleation followed by pinealectomy and administration of exogenous melatonin on air-breathing activity rhythm in a fresh water catfish, C. batrachus maintained at LD 12:12 and laboratary temperature during its prepratory phase, were examined. Results of cosinor analysis clearly reveal that most of the intact individuals exhibited circadian rhythm in their air-breathing activity and such rhythm persists even after enucleation followed by pinealectomy and then melatonin administration. However, the period (tau) of the activity obtained by power spectrum analysis was prominent 24 hr in most of the intact individuals, but it was increased (tau > 24 hr) after enucleation in most of the individuals. In most of the enucleated + pinealectomized individuals tau was less than 24 hr, and after receiving melatonin treatment tau was shifted to prominent 24 hr in most of the individuals. In addition, visual analysis of the actograms depicted that in intact individuals air-breathing activity is entrained with the timings of lights on/off with elevation of activity during dark period and decreased activity during light hours. However, enucleated and enucleated + pinealectomized individuals showed free run in their activity rhythm. The treatment of melatonin reestablished the entrainment of activity at least with the timing of lights off, in most of the studied individuals. Further, daily mean of the air-breathing activity was decreased in enucleated + pinealectomized individuals as compared with other studied groups (intact, enucleated, enucleated + pinealectomized + melatonin receiving). It could be speculated that there may be existence of extraretinal and extrapineal photoreceptors in C. batrachus. However, eyes play an important role in regulating air-breathing activity rhythm in such species. In addition, exogenous melatonin may also have some modulatory effect on such rhythm.

Pulmonary function in infants exposed to pethidine.

OBJECTIVE: To investigate the effects of maternal pethidine administration on pulmonary function tests in newborn infants. PATIENTS AND METHOD: The study was carried out in the Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital. The study group consisted of 20 infants exposed to pethidine within 4 hours prior to delivery. Twenty infants whose mothers received no analgesic drug or regional anesthesia were randomly selected as the controls. Narcotic related respiratory depression was determined by Apgar scores, the need for ventilatory support in the delivery room and abnormal pulmonary function measurements. RESULTS: There was no difference in birth weight and gestational age between the two groups of infants. Pethidine was given to mothers at a dose of 72.5 +/- 7.6 mg/kg with a mean drug-delivery interval of 152 +/- 61 minutes. One infant in each group had a 1-minute Apgar score less than 7, but there was no statistical difference in the mean Apgar score between the two groups. None of the infants whose mothers received pethidine required ventilatory support, but oxygen was provided to eight infants who were apparently cyanosed at birth. Pulmonary function measurements were performed at the age of 7.4 +/- 2.3 hours in the controls and 6.0 +/- 2.5 hours in the study group. There was no significant difference in respiratory rate, tidal volume, inspiratory time, functional residual capacity, compliance and resistance between the two groups of infants. CONCLUSION: Severe narcotic related respiratory depression was uncommon in this study. In the first 12 hours of life, there was no significant difference in pulmonary function of the infants exposed to pethidine. It is quite safe to allow the baby to room-in with the mother if respiratory depression is not presented at birth.

Effect of oral contraceptives on respiratory function.

The present study was carried out to assess the lung functions in oral contraceptive administered women. Lung function tests were carried out with Spirometer (Vitallograph Compact II). A significant increase in vital capacity (VC) was observed in these women as compared to normal control. There was also a significant decrease in forced expiratory volume in 1 sec./vital capacity (FEV1/VC%) and forced expiratory volume in 1 sec./forced vital capacity (FEV1/FVC%) among oral contraceptive administered women as compared to controls. Further, a significant increase in peak expiratory flow rate (PEF), reduction in forced expiratory flow rate (FEF75-85%) and FEF75% were observed among oral contraceptive administered women as compared to controls. The increase in VC and PEF might be due to the synthetic form of progesterone (progestins) present in oral contraceptive pills which causes hyperventilatory changes. Synthetic progesterone during luteal phase of menstrual cycle might increase the static and dynamic volumes of lung i.e. VC and PEF. But FEF75% showed a decrease which might be due to the lower neuromuscular coordination during breathing.

Respiratory mechanics and morphometric changes during anesthesia with ketamine in normal rats

Ketamine is believed to reduce airway and pulmonary tissue resistance. The aim of the present study was to determine the effects of ketamine on the resistive, elastic and viscoelastic/inhomogeneous mechanical properties of the respiratory system, lungs and chest wall, and to relate the mechanical data to findings from histological lung analysis in normal animals. Fifteen adult male Wistar rats were assigned randomly to two groups: control (N = 7) and ketamine (N = 8). All animals were sedated (diazepam, 5 mg, ip) and anesthetized with pentobarbital sodium (20 mg/kg, ip) or ketamine (30 mg/kg, ip). The rats were paralyzed and ventilated mechanically. Ketamine increased lung viscoelastic/inhomogeneous pressure (26 percent) compared to the control group. Dynamic and static elastances were similar in both groups, but the difference was greater in the ketamine than in the control group. Lung morphometry demonstrated dilation of alveolar ducts and increased areas of alveolar collapse in the ketamine group. In conclusion, ketamine did not act at the airway level but acted at the lung periphery increasing mechanical inhomogeneities possibly resulting from dilation of distal airways and alveolar collapse