Time course analysis of mechanical ventilation-induced diaphragm contractile muscle dysfunction in the rat.

Controlled mechanical ventilation (CMV) plays a key role in triggering the impaired diaphragm muscle function and the concomitant delayed weaning from the respirator in critically ill intensive care unit (ICU) patients. To date, experimental and clinical studies have primarily focused on early effects on the diaphragm by CMV, or at specific time points. To improve our understanding of the mechanisms underlying the impaired diaphragm muscle function in response to mechanical ventilation, we have performed time-resolved analyses between 6 h and 14 days using an experimental rat ICU model allowing detailed studies of the diaphragm in response to long-term CMV. A rapid and early decline in maximum muscle fibre force and preceding muscle fibre atrophy was observed in the diaphragm in response to CMV, resulting in an 85% reduction in residual diaphragm fibre function after 9-14 days of CMV. A modest loss of contractile proteins was observed and linked to an early activation of the ubiquitin proteasome pathway, myosin:actin ratios were not affected and the transcriptional regulation of myosin isoforms did not show any dramatic changes during the observation period. Furthermore, small angle X-ray diffraction analyses demonstrate that myosin can bind to actin in an ATP-dependent manner even after 9-14 days of exposure to CMV. Thus, quantitative changes in muscle fibre size and contractile proteins are not the dominating factors underlying the dramatic decline in diaphragm muscle function in response to CMV, in contrast to earlier observations in limb muscles. The observed early loss of subsarcolemmal neuronal nitric oxide synthase activity, onset of oxidative stress, intracellular lipid accumulation and post-translational protein modifications strongly argue for significant qualitative changes in contractile proteins causing the severely impaired residual function in diaphragm fibres after long-term mechanical ventilation. For the first time, the present study demonstrates novel changes in the diaphragm structure/function and underlying mechanisms at the gene, protein and cellular levels in response to CMV at a high temporal resolution ranging from 6 h to 14 days.

Molecular characterization and expression of three heat shock protein70 genes from the carmine spider mite, Tetranychus cinnabarinus (Boisduval).

Three heat shock protein 70 (Hsp70) cDNAs were isolated from the carmine spider mite, Tetranychus cinnabarinus. They were tentatively named as TCHsp70-1, TCHsp70-2 and TCHsp70-3. Structural analyses showed that all of the three TCHsp70 cDNAs held the full open reading frame (ORF). Putative protein sequences and a phylogenetic tree suggested that TCHsp70-1 and TCHsp70-3 were cytoplasm HSP70 and TCHsp70-2 was endoplasmic reticulum HSP70. Comparison of deduced amino acid sequences of TCHsp70-1 and TCHsp70-3 showed 84.78% identity, TCHsp70-1 and TCHsp70-2 showed 57.33% identity, TCHsp70-2 and TCHsp70-3 showed 58.26% identity. Real-time comparative quantitative PCR revealed that the relative expression of TCHsp70-2 was lower than TCHsp70-1 and TCHsp70-3 at each temperature tested. TCHsp70-1 and TCHsp70-3 shared a similar expression pattern after cold and heat shock compared with their expression at normal temperature (26 degrees C), but the mRNA expression of TCHsp70-1 was significantly higher and lower than that of TCHsp70-3 at cold and heat shock temperatures (except for 34 degrees C), respectively. This result possibly indicated the expression patterns of TCHsp70 were affected by their location in different cellular compartments. The results also indicated that three TCHsp70s, especially TCHsp70-1 and TCHsp70-3, may play an important role in mediating tolerance to cold, thermal stress for Tetranychus cinnabarinus.

Co-expression of skeletal and cardiac troponin T decreases mouse cardiac function.

In contrast to skeletal muscles that simultaneously express multiple troponin T (TnT) isoforms, normal adult human cardiac muscle contains a single isoform of cardiac TnT. To understand the significance of myocardial TnT homogeneity, we examined the effect of TnT heterogeneity on heart function. Transgenic mouse hearts overexpressing a fast skeletal muscle TnT together with the endogenous cardiac TnT was investigated in vivo and ex vivo as an experimental system of concurrent presence of two classes of TnT in the adult cardiac muscle. This model of myocardial TnT heterogeneity produced pathogenic phenotypes: echocardiograph imaging detected age-progressive reductions of cardiac function; in vivo left ventricular pressure analysis showed decreased myocardial contractility; ex vivo analysis of isolated working heart preparations confirmed an intrinsic decrease of cardiac function in the absence of neurohumoral influence. The transgenic mice also showed chronic myocardial hypertrophy and degeneration. The dominantly negative effects of introducing a fast TnT into the cardiac thin filaments to produce two classes of Ca(2+) regulatory units in the adult myocardium suggest that TnT heterogeneity decreases contractile function by disrupting the synchronized action during ventricular contraction that is normally activated as an electrophysiological syncytium.

[Transition of soleus troponin I isoforms and atrophy of testis in tail-suspended rats].

Objective. To observe the transition time of soleus I (TnI) isoforms and to elucidate the relationship between soleus TnI transition and atrophy; and to analyze the time course between testis atrophy and soleus atrophy. Method. Eight groups of male rats were suspended for 3, 4, 5, 7, 14, 21, 28 and 42 d, respectively. Besides, three groups of female rats were suspended for 3, 4 and 5 d respectively. Wet and relative weights (wet weight/body weight) of testis and soleus were measured. The expression of TnI was observed by Western blot. Result. The relative weight of soleus of tail-suspended male rats decreased significantly after 4 d of suspension as compared with control. The degree of rats soleus atrophy in the first 14 d of suspension was greater than that after 14 d. The relative weight of testis showed the same change as that of soleus. There was no significant change in the relative weight of soleus in 4 d of tail-suspended female rats. The significant decrease in the relative weight of tail-suspended female rats began on the 5th day. The Western blot showed that the transition from slow skeletal TnI (ssTnI) to fast skeletal TnI (fsTnI) in the soleus occurred in 14 d of tail-suspension. Conclusion. The overt atrophy of tail-suspended male rats occurs on the 4th day. The soleus TnI transition from ssTnI to fsTnI is on the 14th day. It is suggested that the TnI is not the sensitive protein to gravity. The overt atrophy of female tail-suspended rats occurs at the 5th day. This indicated that the decrease in testosterone level may accelerate the atrophy of the soleus.

[The suggestive indication for operation on pulmonary tuberculoma--based on the bacteriologic study on the tuberculous section samples].

The pathologic features, tuberculous bacilli and antituberculous drug resistance were studied on lung section samples from 16 patients with pulmonary tuberculoma. The authors found that in about half of the samples the tuberculous bacilli were positive. When the diameter of the lesion was > 3cm, the positive rate for bacilli was high and the isolated bacilli were resistant to different antituberculous drugs in various level. The indication for operation was also recommended.

[Histochemical changes in endometrial fibrolytic activity with different IUDs].

The histochemical changes of endometrial fibrinolytic activity were observed in rabbits. 1 horn of the uterus was put in IUDs made of different materials (steel, copper, magnet, and EACA-copper). It was found that the endometrial fibrinolytic activity in the experimental horns was significantly higher than the controls, and the effect was the highest with the copper IUD. In the contrasted groups (copper versus steel, copper versus magnet, steel versus magnet), the endometrial fibrinolytic activity induced by the copper IUD was the highest (P0.05), while there was no significant diffeence between that of steel and magnet (P0.05). In the EACA-copper IUD groups, the results were also observed on days 7, 14, and 28 after insertion of the devices. There was no difference in fibrinolytic activity between the experimental horns and the controls in 7 and 14 days groups, but it was significantly higher than the controls in 28 days group. In the contrasted groups of the EACA-copper IUD and copper IUD the endometrial fibrinolytic activity of the former was lower than that of the latter in 7 days group (0.05 P 0.1). This suggests that fibrinolytic activity may be inhibited by EACA, which, however, may be released from IUD at such a rapid rate that it loses its effect in 28 days.