Effects of cadmium on the ultrastructure of the mouse parathyroid gland

Electron-microscopic studies were made on the parathyroid gland of cadmium-treated mice. Most chief cells in treated mice were rich in free ribosomes and secretory granules compared to the control mice. In the parathyroid gland after 3 and 4 weeks of administration of cadmium, interdigitations between adjacent chief cells became more complex than in the control mice. In most chief cells of the parathyroid gland after 2, 3 and 4 weeks of administration of cadmium, the Golgi complexes associated with numerous prosecretory granules were better developed than in the control mice. These ultrastructural appearances suggest that parathyroid gland cellular activity was stimulated in response to cadmium treatment.     

Effects of cadmium on E-cadherin and VE-cadherin in mouse lung

Exposure to Cd(2+) via inhalation or intratracheal instillation results in pulmonary edema, which is followed by the influx of leukocytes, the proliferation of type II pneumocytes and eventual scarring and fibrotic changes. While the general toxic effects of Cd(2+) in the lung have been well characterized, the specific molecular mechanisms underlying these effects have yet to be elucidated. Previously we have shown that Cd(2+) can disrupt the adhering junctions between various types of epithelial and endothelial cells in culture, most likely by perturbing the function of the Ca(2+) dependent cell adhesion molecules E-cadherin and VE-cadherin respectively. The objectives of this study were to determine whether respiratory exposure to Cd(2+) can alter the localization of E-cadherin and VE-cadherin in the lung, and to determine whether this effect may play a role in the acute pneumotoxic response to Cd(2+). Male CF-1 mice were exposed to CdCl(2) (0, 16.25, 32.5, 65 or 130 nmoles in 50 microl saline) via intratracheal instillation. After 24 hours, the lungs were removed and either subjected to bronchoalveolar lavage or analyzed for histopathologic changes. The results showed that Cd(2+) caused an increase in lung weight and in the protein content of the lavage fluid. These effects were accompanied by a pronounced decrease in the amount of E-cadherin in epithelial cells of the alveoli and small bronchioles and of VE-cadherin in vascular endothelial cells. Assessment of cell membrane integrity with ethidium homodimer-1 showed no evidence of severe injury or death in alveolar epithelial cells. These findings suggest that E-cadherin and VE-cadherin may be important early targets of Cd(2+) toxicity in the lung.     

Effects of cadmium on polyribosome sedimentation pattern in mouse liver.

Cadmium injected to mice provokes an acute disaggregation of hepatic polyribosomes. The effect appears within 15 min, it is maximal after 1 h and then gradually disappears. The reaggregation of polyribosomes takes place 6--12 h after injection. The disaggregation of polyribosomes is linear with log doses in a range of 7.25--20 mumol/kg CdCl2. Cycloheximide pretreatment prevents the disaggregation of polyribosomes in the livers of cadmium-treated mice.     

Periodic breathing in the mouse.

The hypothesis was that unstable breathing might be triggered by a brief hypoxia challenge in C57BL/6J (B6) mice, which in contrast to A/J mice are known not to exhibit short-term potentiation; as a consequence, instability of ventilatory behavior could be inherited through genetic mechanisms. Recordings of ventilatory behavior by the plethsmography method were made when unanesthetized B6 or A/J animals were reoxygenated with 100% O(2) or air after exposure to 8% O(2) or 3% CO(2)-10% O(2) gas mixtures. Second, we examined the ventilatory behavior after termination of poikilocapnic hypoxia stimuli in recombinant inbred strains derived from B6 and A/J animals. Periodic breathing (PB) was defined as clustered breathing with either waxing and waning of ventilation or recurrent end-expiratory pauses (apnea) of > or = 2 average breath durations, each pattern being repeated with a cycle number > or = 3. With the abrupt return to room air from 8% O(2), 100% of the 10 B6 mice exhibited PB. Among them, five showed breathing oscillations with apnea, but none of the 10 A/J mice exhibited cyclic oscillations of breathing. When the animals were reoxygenated after 3% CO(2)-10% O(2) challenge, no PB was observed in A/J mice, whereas conditions still induced PB in B6 mice. (During 100% O(2) reoxygenation, all 10 B6 mice had PB with apnea.) Expression of PB occurred in some but not all recombinant mice and was not associated with the pattern of breathing at rest. We conclude that differences in expression of PB between these strains indicate that genetic influences strongly affect the stability of ventilation in the mouse.     

Effects of cadmium on lactate dehydrogenase activities in mouse pre-embryos at various stages

A decline in LDH activity from four-cell to late blastocyst was demonstrated in pre-embryos from F1 (C57 female X A2G male) female mice. An exposure to 0.5 or 1 microgram/ml cadmium did not affect the in vitro development of the four-cell pre-embryos and morulae or their LDH activities. At 5 or 10 micrograms/ml cadmium, the in vitro development of the treated pre-embryos was affected. Although most of the treated four-cell pre-embryos had proceeded to compaction, they became degenerated 24 h after treatment. The LDH activity of these degenerated pre-embryos was higher than that in the control blastocysts. We propose that cadmium may interfere with the general energy metabolism of the cells. This causes a reduced rate of LDH degradation, leading to a slower decline in LDH activity in cadmium-treated pre-embryos. Failure of some critical biochemical processes after cadmium treatment may ultimately lead to the subsequent degeneration of the treated pre-embryos.     

Effects of inhaled oxygen (up to 40%) on periodic breathing and apnea in preterm infants.

To discover whether increases in inhaled O2 fraction (FIO2; up to 40%) decrease apnea via an increase in minute ventilation (VE) or a change in respiratory pattern, 15 preterm infants (birth weight 1,300 +/- 354 g, gestational age 29 +/- 2 wk, postnatal age 20 +/- 9 days) breathed 21, 25, 30, 35, and 40% O2 for 10 min in quiet sleep. A nosepiece and a flow-through system were used to measure ventilation. Alveolar PCO2, transcutaneous PO2, and sleep states were also assessed. All infants had periodic breathing with apneas greater than or equal to 3 s. With an increase in FIO2 breathing became more regular and apneas decreased (P less than 0.001). This regularization in breathing was not associated with significant changes in VE. However, the variability of VE, tidal volume, and expiratory and inspiratory times decreased significantly. The results indicate that the more regular breathing observed with small increases in FIO2 was not associated with significant changes in ventilation. The findings suggest that the increased oxygenation decreases apnea and periodicity in preterm infants, not via an increase in ventilation, but through a decrease in breath-to-breath variability of VE.     

Effects of dopamine on chemoreflexes in breathing

The effects of intravenous infusion of dopamine (20 microgram.min) on the steady-state ventilatory and carotid chemoreceptor responses to successive levels of isocapnic hypoxia and hyperoxic hypercapnia were investigated in cats anesthetized with alpha-chloralose. Dopamine infusion was followed by a maximal decrease in ventilation in about 20 s. Thereafter, the effect diminished and stabilized. Termination of dopamine infusion was promptly followed by an increase in ventilation. These ventilatory responses were smaller than the corresponding carotid chemoreceptor responses. The steady-state effect of dopamine infusion was to diminish ventilation at all levels of arterial O2 tension, the decrease being greater during hypoxia than that during hyperoxia. Bilateral section of the carotid sinus nerves significantly diminished but did not abolish the inhibitory effect of dopamine on ventilation during hyperoxia. Thus the ventilatory depression due to dopamine infusion is not entirely due to its effect on the carotid chemoreceptors. Dopamine decreased ventilatory responses to successive levels of hypercapnia by the same magnitude without changing the slope of the response curves. The steady-state relationship between chemoreceptor activity and ventilation shows that the ventilatory equivalent for carotid chemoreceptor activity is increased during dopamine infusion because of its greater inhibitory effect on carotid chemoreceptor activity than on ventilation with the decrease of arterial O2 tension.     

镉对小鼠精子蛋白酪氨酸磷酸化修饰的影响及EGTA的保护作用

采用体外培养的方法,利用精子活力分析软件(CASA)、蛋白免疫印迹(WB)及免疫荧光技术, 探讨镉(Cd)对小鼠精子活力参数、蛋白酪氨酸磷酸化修饰的影响,并对小鼠精子酪氨酸磷酸化蛋白进行细胞亚组分定位. 结果表明: Cd对小鼠精子活力具有明显抑制作用,且随着Cd浓度的增加抑制作用增强,当Cd浓度达到1.0 μmol·L^-1时, 小鼠精子活力(MOT)显著低于对照组;同时,Cd促进小鼠精子蛋白酪氨酸磷酸化,当浓度≥1.0 μmol·L^-1时,尤其分子量约为55 kDa的蛋白酪氨酸磷酸化程度显著增强,且免疫荧光结果显示主要集中在小鼠精子中段;当用30 μmol·L^-1 乙二醇二乙醚二胺四乙酸(EGTA)和10 μmol·L^-1 Cd同时培养时,55 kDa蛋白并未发生明显的酪氨酸磷酸化修饰,而且小鼠精子活力变化不显著. 表明Cd可能是通过诱导中段55 kDa蛋白发生酪氨酸磷酸化修饰从而抑制精子活力,EGTA能螯合Cd离子并有效防止其毒性作用. 研究证实,Cd诱导精子特异性蛋白酪氨酸磷酸化增强,进而抑制精子活力. EGTA可以用于体外控制Cd进入细胞的阻断剂,为Cd繁殖毒性分子机制的研究提供了研究手段.     

Effect of inhaled alpha-emitting nuclides on mouse alveolar macrophages

The effects of inhaled alpha emitters on the free cell population of the mouse lung were investigated up to 100 days after exposure. Groups of mice inhaled aerosols of 238PuO2, 239PuO2, or 241Am(NO3)3 to give alveolar deposits resulting in lung-averaged cumulative absorbed doses of about 20 Gy by the end of the study. Initially, with 238Pu most of the activity was associated with relatively few pulmonary alveolar macrophages (PAM), whereas with 241Am, all pulmonary alveolar macrophages were labeled and a substantial fraction was extracellular. The free cell population of the lung was sampled using bronchoalveolar lavage. The main parameters investigated were (a) the recovery and total numbers of free cells, including PAM, lymphocytes, and neutrophils; (b) the incidence of nuclear abnormalities in PAM (cells with more than one nucleus or with micronuclei); and (c) metabolic activation of PAM from measurements of their size and associated beta-glucuronidase activity. All three actinides produced depletions in total numbers of PAM, increased incidences of nuclear abnormalities, and metabolic activation of PAM, without a marked infiltration of inflammatory cells. Americium-241, which is distributed relatively uniformly in PAM, produced the most marked changes in that population and 238Pu, which gave the most inhomogeneous distribution of activity, produced the least.     

Effects of tumors on inhaled pharmacologic drugs

Lung carcinomas are now the most common form of cancer. Clinical data suggest that tumors are found preferentially in upper airways, perhaps specifically at carina within bifurcations. The disease can be treated by aerosolized pharmacologic drugs. To enhance their efficacies site-specific drugs must be deposited selectively. Since inhaled particles are transported by air, flow patterns will naturally affect their trajectories. Therefore, in Part I of a systematic investigation, we focused on tumor-induced effects on airstreams, in Part II (the following article [p. 245]), particle trajectories were determined. To facilitate the targeted delivery of inhaled drugs, we simulated bifurcations with tumors on carinas using a commercial computational fluid dynamics (CFD) software package (FIDAP) with a Cray T90 supercomputer and studied effects of tumor sizes and ventilatory parameters on localized flow patterns. Critical tumor sizes existed; e.g., tumors had dominant effects when r/R > or = 0.8 for bifurcation 3-4 and r/R > or = 0.6 for bifurcation 7-8 (r = tumor radius and R = airway radius). The findings suggest that computer modeling is a means to integrate alterations to airway structures caused by diseases into aerosol therapy protocols.     

Effects of tumors on inhaled pharmacologic drugs

Computer simulations were conducted to describe drug particle motion in human lung bifurcations with tumors. The computations used FIDAP with a Cray T90 supercomputer. The objective was to better understand particle behavior as affected by particle characteristics, airflow conditions, and disease-modified airway geometries. The results indicated that increases in particle sizes, breathing intensities and tumor sizes could enhance drug deposition on the tumors. The modeling suggested that targeted drug delivery could be achieved by regulating breathing parameters and designing (selecting physical features of) aerosolized drugs. We present the theoretical work as a step towards improving aerosol therapy protocols. Since modeling describes factors affecting dose, it is complementary to considerations of the molecular aspects of drug formulation and pharmacokinetics.     

Effects of hyperthermia on fetal breathing movements

High environmental temperature is known to impair fetal growth and development. We now report long lasting changes in fetal breathing activity following the exposure of pregnant ewes to an ambient temperature of 43 degrees C for 8 h. In 16 trials in 10 ewes (119-138 days gestation) heat exposure increased maternal and fetal core temperatures 1.5-2.0 degrees C, and the hyperventilation by the ewe produced a fall in fetal PaCO2 from 53.5 +/- 1.3 to 34.8 +/- 5.3 mmHg (P less than 0.05). Fetal breathing movements decreased in incidence during the hyperthermia but remained episodic (present during low-voltage electrocortical activity) with occasional brief episodes of breathing at high rates (greater than 4 breaths/s). However, 1-2 h after the end of heating, when maternal and fetal core temperature and PaCO2 had returned to normal, fetal breathing movements became continuous, and were augmented 30-100% in amplitude. Fetal breathing movements occurred during both low- and high-voltage electrocortical activity. The results show that a heat load similar to that experienced by sheep in sub-tropical regions in the summer months cause prolonged changes in the central regulation of fetal breathing.     

Repetitive measurements of pulmonary mechanics to inhaled cholinergic challenge in spontaneously breathing mice.

Precise and repeatable measurements of pulmonary function in intact mice are becoming increasingly important for experimental investigations on various respiratory disorders including asthma. Here, we present validation of a novel in vivo method that, for the first time, combines direct and repetitive recordings of standard pulmonary mechanics with cholinergic aerosol challenges in anesthetized, orotracheally intubated, spontaneously breathing mice. We demonstrate that, in several groups of nonsensitized BALB/c mice, dose-related increases in pulmonary resistance and dynamic compliance to aerosolized methacholine are reproducible over short and extended intervals without causing detectable cytological alterations in the bronchoalveolar lavage or relevant histological changes in the proximal trachea and larynx regardless of the number of orotracheal intubations. Moreover, as further validation, we confirm that allergic mice, sensitized and challenged with Aspergillus fumigatus, were significantly more responsive to cholinergic challenge (P < 0.01) and exhibited marked eosinophilia and lymphocytosis in bronchoalveolar lavage fluids as well as significant pathological alterations in laryngotracheal histology compared with nonsensitized mice. We suggest that this approach will provide useful and necessary information on pulmonary mechanics in studies of various respiratory disorders in mice, including experimental models of asthma and chronic obstructive pulmonary disorder, investigations of pulmonary pharmacology, or more general investigations of the genetic determinants of lung function.     

Effects of cadmium on lymphocyte activation

The effects of cadmium (Cd) on phytohemoagglutinin or phorbol myristate acetate-induced lymphocyte activation were investigated and a dose-dependent inhibition of cell proliferation was found. Kinetic studies revealed that the Cd-sensitive step is an early event of T cell stimulation. Failure of IL2 secretion and reduction of IL2 receptor expression in the Cd-treated cells are also reported. Regardless of which mechanism is responsible for Cd effects, our studies show that the inhibition of lymphocyte activation is associated with reduced [3H]phorbol dibutyrate binding to Ca2+-phospholipid-dependent protein kinase and altered breakdown of phosphatidylinositols. Thus, Cd interferes with two biochemical events which play a critical role in lymphocyte signal transduction and activation.     

Effects of naloxone on breathing movements during hypercapnia in the fetal lamb

To determine whether endogenous opioids influence the fetal breathing response to CO2 we have investigated the effect of the opiate antagonist, naloxone on the incidence, rate, and amplitude of breathing movements during hypercapnia in fetal lambs in utero. In 20 experiments in six pregnant sheep (130-145 days gestation) hypercapnia was induced by giving the ewe 4-6% CO2-18% O2 in N2 to breathe for 60 min. After 30 min of hypercapnia either naloxone (13 experiments) or saline (7 experiments) was infused intravenously for the remaining 30 min. During hypercapnia breath amplitude increased from 5.8 +/- 0.5 to 9.1 +/- 1.2 mmHg (P less than 0.001), and infusion of naloxone was associated with a further significant increase to 15.7 +/- 1.2 mmHg (P less than 0.001). Naloxone had no effect on the incidence or rate of breathing movements during hypercapnia. After hypercapnia there was a significant decrease in the incidence of fetal breathing movements in the naloxone group (14.7 +/- 3.2%). Infusion of saline during hypercapnia had no effect on incidence, rate, or amplitude of fetal breathing movements. These results suggest that endogenous opioids act to suppress or limit breath amplitude during hypercapnia but do not affect rate or incidence of breathing movements.     

Effects of increase in body temperature on the breathing pattern in premature infants

This study was designed to determine the effects of a mild increase in body temperature within the physiological range (0.8 degrees C) in healthy premature infants. Seven unsedated premature infants (38.4 wk +/- 1.5 postconceptional age) were monitored polygraphically during "morning naps" in an incubator under two different environmental temperatures: (1) normothermia with the incubator temperature set at 25 degrees C and the rectal temperature equal to 36.9 degrees C +/- 0.1; (2) hyperthermia with the incubator temperature set at 35 degrees C and the rectal temperature equal to 37.7 degrees C +/- 0.15. Respiratory frequency and heart rate, respiratory events, i.e., central and obstructive apnea, and periodic breathing with and without apneic oscillations were tabulated. Results for respiratory events were expressed as (1) indices of the total number of respiratory events, and of specific respiratory events per hour of total, quiet and active sleep times; (2) duration of total and specific respiratory events expressed as a percentage of total sleep, quiet and active sleep times. Respiratory frequency and heart rate were significantly increased by hyperthermia (P less than 0.05). Hyperthermia did not significantly modify the indices or the duration of central and obstructive apnea. But the indices and the duration of periodic breathing with and without apneic oscillations were significantly increased by hyperthermia during active sleep (P less than 0.05) but not during quiet sleep. The present study shows that a mild increase in body temperature within the physiological range in premature infants enhances the instability of the breathing pattern during active sleep.