[Chlamydia psittaci pneumonia complicated with rhabdomyolysis: a case report and literature review].

Objective: To analyze the clinical characteristics and the diagnosis and treatment of Chlamydia psittaci pneumonia complicated with rhabdomyolysis. Methods: We reported a case of Chlamydia psittaci pneumonia complicated with rhabdomyolysis. We did a literature review on the published reports between January 1978 and May 2020 by searching with the key words of "psittacosis" or "Chlamydia psittaci" and "rhabdomyolysis" in the PubMed database (time frame: January 1, 1967 to May 30, 2020). Results: Our patient was a 64-year-old male presenting with high-grade fever, fatigue, myalgia and dyspnea. A computed tomographic scan of the chest revealed bilateral pneumonia, which was further complicated with rhabdomyolysis during disease progression. This prompted the metagenomic next-generation sequencing, revealing the sequences of Chlamydia psittaci in both the bronchoalveolar lavage fluid and blood. Of the 11 cases in the 3 literature reports that we retrieved, 5 had concomitant rhabdomyolysis (two of which did not have complete clinical information), and the other 6 cases had myositis complicated with an elevated level of creatine phosphokinase. This yielded 3 cases with complete clinical information for our analysis. We had further incorporated their information with the single case managed within our study site. Two were males and the other 2 were females. The patients were aged 66, 46, 44 and 64 years, respectively. All cases had fever and 3 had a contact history with live poultry. Two cases had myalgia and progressed rapidly into having respiratory failure, and the other 2 cases did not develop myalgia and improved significantly after a timely treatment. All 4 cases were cured and discharged after treatment with appropriate antibiotics. No adverse outcomes were observed. Conclusions: The prognosis of Chlamydia psittaci pneumonia complicated with rhabdomyolysis was poor in case of a delayed treatment. Early diagnosis would help reduce the mortality.

Visualising the boundary sharpness of uterine zonal structures using high-resolution T2-weighted images during the menstrual cycle.

AIM: To investigate whether there is an optimal time in the menstrual cycle to obtain the best image quality of uterine zonal structures with high-field magnetic resonance imaging (MRI). MATERIALS AND METHODS: Thirty-eight normal volunteers with regular menstrual cycles underwent pelvic 3 T high-resolution T2-weighted three-dimensional (3D) turbo spin echo (TSE) with variable flip angle MRI examinations during the menstrual phase (MP), follicular phase (FP), peri-ovulatory phase (OP), and luteal phase (LP). Two radiologists blinded evaluated the boundary sharpness of the three zonal structures of the uterine corpus and cervix on mid-sagittal images using a three-point Likert-scale. The signal intensity (SI) on T2-weighted sequences of each zonal structure was measured and the ratio between the SI of adjacent structures was calculated. Paired Wilcoxon's test and repeated measurement analysis of variance were used to investigate the differences among the four phases. RESULTS: No variation during the menstrual cycle was found in 10.5% (4/38) of volunteers and their boundaries were all well-defined. The OP exhibited the clearest boundaries of the corpus zonal structures. For the endometrium to junctional zone, mean scores of boundary sharpness from high to low were 3 (OP), 2.97 (FP), 2.76 (LP), 2.74 (MP); that for the junctional zone to myometrium were 2.76 (OP), 2.42 (FP), 2.32 (LP), 2.11 (MP); which were consistent with the SI ratio results. The results for the cervix showed no statistical difference during the menstrual cycle (p>0.05), and was well-defined throughout. CONCLUSIONS: The OP is recommended as the best phase to investigate zonal-related uterine corpus diseases due to the best contrast. For cervical diseases, imaging could be performed when necessary at any time point, due to the limited influence of menstrual phases on cervical zone delineation.

[Downregulation of large conductance calcium-activated potassium channels in paraventricular nucleus contributes to sympathoexcitation in rats with chronic heart failure].

Objective: To elucidate the association between large conductance calcium-activated potassium channels (BKCa) in the paraventricular hypothalamic nucleus (PVN) and sympathetic outflow in rats with chronic heart failure (CHF) . Methods: Male Wistar rats (6-7 weeks old) were randomized to sham operated group and CHF group (coronary artery ligation) . Two weeks after operation, BKCa inhibitor Iberiotoxin (IBTX) was infused into PVN by osmotic minipumps, rats were divided into following groups: sham+aCSF, CHF+aCSF, sham+low dose IBTX (0.125 nmol/nl) , CHF+low dose IBTX, sham+moderate dose IBTX (1.25 nmol/nl) , CHF+moderate dose IBTX, sham+ high dose IBTX (12.5 nmol/nl) , and CHF+high dose IBTX (n=6 each) . Additional rats were grouped as follows: sham+vehicle, sham+KCNMB4 knockdown (by rAAV2-KCNMB4 shRNA virus injection in PVN) , CHF+vehicle, CHF+ KCNMB4 knockdown group (n=6 each) . The cardiac function was determined by echocardiography, left ventricular hemodynamics were measured invasively, renal sympathetic nerve activity (RSNA) was recorded at 6 weeks after coronary artery ligation or sham operation. The contents of norepinephrine (NE) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in plasma were determined by enzyme-linked immunosorbent assay. The protein and mRNA expression of KCNMB4 in PVN were measured by immunofluorescence staining, Western blot, and real-time PCR, mRNA expression of BKCa in PVN was detected by real-time PCR. Results: Compared with the sham operation group, the cardiac function of the heart failure group was significantly reduced (P<0.05) , and the plasma NE and the serum NT-proBNP were significantly elevated (P<0.05) . The protein and mRNA expression of KCNMB4 in PVN were obviously down-regulated in CHF rats (P<0.05) . After perfusion of IBTX or KCNMB4 knockdown by microinjection of rAAV2-KCNMB4 shRNA virus,right ventricular weight/body weight and lung weight/body weight ratio as well as left ventricular end-diastolic diameter were increased and left ventricular ejection fraction was decreased (all P<0.05) , the sympathetic driving indexes was increased in sham rats, changes of these parameters further aggravated in CHF rats (P<0.05) . KCNMB4 knockdown further downregulated protein expression in PVN of CHF rats. Conclusion: Downregulation and blunted function of BKCa in PVN may contribute to sympathoexcitation and deterioration of cardiac function in rats with chronic heart failure.

[Role and mechanism of hydrogen sulfide in cigarette smoke induced chronic obstructive pulmonary disease related pulmonary vascular remodeling in rats].

Objective: To investigate the role and mechanism of hydrogen sulfide (H2S) in rats with chronic obstructive pulmonary disease (COPD) related pulmonary vascular remodeling. Methods: Twenty four healthy male Sprague-Dawley rats were randomly divided into 4 groups: control group, cigarette smoke (CS) group, CS+ Sodium hydrosulfide (NaHS) group and CS+ DL-propargylglycine (PPG) group. Rats in control group were fed normally and breathed clear air, and for the rest groups, passive cigarette smoke inhalation method were adopted to establish COPD model. After 8 weeks, the rats in corresponding groups were treated by NaHS or PPG. After 16 weeks, the markers of pulmonary vascular remodeling in all groups were measured. Proliferation marker proliferative cell nuclear antigen (PCNA) and oxidative stress marker 3-neurotrophin (3-NT) in all groups were measured by immunohistochemistry (IHC). Results: Compared with control group, the airway resistance was increased (0.859±0.283 vs 0.578±0.088, P<0.05) and the pathological scores was much higher in CS group, which suggested that the COPD model was successful. The degree of small resistance pulmonary artery medial wall thickness and full vascular muscularization of CS group were much higher (0.54±0.20 vs 0.37±0.12, 0.39±0.08; 0.61±0.16 vs 0.20±0.12, 0.34±0.13, all P<0.01)than control group and CS+ NaHS group, there was no significant difference between CS+ PPG group and CS group. In accordance with the results of morphometric analysis, the proliferation marker PCNA was more in CS group when compared with control group and CS+ NaHS group (0.27±0.08 vs 0.12±0.06, 0.14±0.06, both P<0.05), there was no significant difference between CS+ PPG group and CS group. Furthermore, the IHC also showed that 3-NT significantly increased in CS group compared with control group and CS+ NaHS group (0.26±0.08 vs 0.18±0.04, 0.19±0.06, both P<0.01), there was no significant difference between CS+ PPG group and CS group as well. In addition, the small resistance pulmonary artery medial wall thickness had strong correlation with the expression level of oxidative stress marker 3-NT (r=0.906, P<0.001). Conclusion: H2S significantly attenuates cigarette smoke induced COPD related pulmonary vascular remodeling, which could be related to its ability to decrease oxidative stress.

Endoplasmic reticulum stress in bone marrow-derived cells prevents acute cardiac inflammation and injury in response to angiotensin II.

Inflammation plays an important role in hypertensive cardiac injury. The endoplasmic reticulum (ER) stress pathway is involved in the inflammatory response. However, the role of ER stress in elevated angiotensin II (Ang II)-induced cardiac injury remains unclear. In this study, we investigated the role of ER stress in Ang II-induced hypertensive cardiac injury. Transcriptome analysis and quantitative real-time PCR showed that Ang II infusion in mice increased ER stress-related genes expression in the heart. C/EBP homologous protein (CHOP) deficiency, a key mediator of ER stress, increased infiltration of inflammatory cells, especially neutrophils, the production of inflammatory cytokines, chemokines in Ang II-infused mouse hearts. CHOP deficiency increased Ang II-induced cardiac fibrotic injury: (1) Masson trichrome staining showed increased fibrotic areas, (2) immunohistochemistry staining showed increased expression of α-smooth muscle actin, transforming growth factor ß1 and (3) quantitative real-time PCR showed increased expression of collagen in CHOP-deficient mouse heart. Bone marrow transplantation experiments indicated that CHOP deficiency in bone marrow cells was responsible for Ang II-induced cardiac fibrotic injury. Moreover, TUNEL staining and flow cytometry revealed that CHOP deficiency decreased neutrophil apoptosis in response to Ang II. Taken together, our study demonstrated that hypertension induced ER stress after Ang II infusion. ER stress in bone marrow-derived cells protected acute cardiac inflammation and injury in response to Ang II.

Effect of Treadmill Running on Apelin and APJ Expression in Adipose Tissue and Skeletal Muscle in Rats Fed a High-fat Diet.

Apelin, an adipokine and also a myokine, is involved in glucose homeostasis. In this study we investigated the effect of insulin resistance and exercise on the regulation of apelin and APJ in adipose tissue and skeletal muscle. After 20 weeks of a high-fat diet (HFD), rats showed severe insulin resistance, with increased fasting blood sugar and plasma insulin and impaired glucose tolerance. Plasma apelin immunoreactivity as well as apelin and APJ expression in adipose tissue and gastrocnemius muscle were significantly increased, with no difference in soleus muscle. Treadmill running completely ameliorated the HFD-induced insulin resistance, decreased plasma apelin level, and downregulated apelin and APJ expression in adipose tissue. However, apelin and APJ expression was upregulated in soleus and gastrocnemius muscle with treadmill training and a HFD. Exercise had a tissue-dependent effect on apelin and APJ expression in rats fed a HFD.

Tumor cell-activated CARD9 signaling contributes to metastasis-associated macrophage polarization.

Macrophages are critical immune effector cells of the tumor microenvironment that promote seeding, extravasation and persistent growth of tumor cells in primary tumors and metastatic sites. Tumor progression and metastasis are affected by dynamic changes in the specific phenotypes of macrophage subpopulations; however, the mechanisms by which tumor cells modulate macrophage polarization remain incompletely understood. Caspase recruitment domain-containing protein 9 (CARD9) is a central adaptor protein of innate immune responses to extracellular pathogens. We report that increased CARD9 expression is primarily localized in infiltrated macrophages and significantly associated with advanced histopathologic stage and the presence of metastasis. Using CARD9-deficient (CARD9(-/-)) mice, we show that bone marrow-derived CARD9 promotes liver metastasis of colon carcinoma cells. Mechanistic studies reveal that CARD9 contributes to tumor metastasis by promoting metastasis-associated macrophage polarization through activation of the nuclear factor-kappa B signaling pathway. We further demonstrate that tumor cell-secreted vascular endothelial growth factor facilitates spleen tyrosine kinase activation in macrophages, which is necessary for formation of the CARD9-B-cell lymphoma/leukemia 10-mucosa-associated lymphoid tissue lymphoma translocation protein 1 complex. Taken together, our results indicating that CARD9 is a regulator of metastasis-associated macrophages will lead to new insights into evolution of the microenvironments supporting tumor metastasis, thereby providing targets for anticancer therapies.

Adrenomedullin attenuates vascular calcification in fructose-induced insulin resistance rats.

AIM: To determine the therapeutic effects of adrenomedullin (ADM) on vascular calcification and related molecular mechanism in fructose-induced insulin resistance rats. METHODS: Rats received ordinary drinking water or 10% fructose in drinking water for 12 weeks and subcutaneous injection of normal saline or ADM (3.6 µg kg(-1) ) twice a day for the last 4 weeks. Levels of ADM, calcitonin receptor-like receptors (CRLR), receptor activity-modifying proteins (RAMP) as well as calcium content, alkaline phosphatase (ALP) activity, osteoblastic and contractile smooth muscle markers in aortic media were measured. RESULTS: The levels of ADM, CRLR, RAMP2 and RAMP3 in aortic media were increased in fructose-fed rats. ADM treatment attenuated the fructose-induced insulin resistance, increased blood pressure, fasting glucose, insulin, triglycerides and cholesterol levels. It improved VSMCs proliferation and disordered arrangement and hyperplasia of elastic fibres in fructose-fed rats. Calcium deposits, calcium content and ALP activity in the aortic media were increased in fructose-fed rats, which were attenuated by ADM treatment. The osteoblastic markers such as osteopontin (OPN), bone morphogenetic protein 2 (BMP2) proteins and core binding factor alpha-1 (Cbfα-1) protein and mRNA expressions were increased in fructose-fed rats. ADM treatment increased the OPN protein expression, but reduced the BMP2 protein, Cbfα-1 protein and mRNA expression. Contractile smooth muscle markers such as α-actin and smooth muscle 22α (SM-22α) were downregulated in fructose-fed rats, which were recovered by ADM treatment. CONCLUSION: Administration of ADM attenuates insulin resistance, calcium deposition and osteogenic transdifferentiation in aortic media in fructose-fed rats.

Primary malignant fibrous histiocytoma of the thyroid.

AIMS AND METHODS: To study the clinical features, diagnosis, and treatment of primary malignant fibrous histiocytoma of the thyroid (MFH-T). Treatment and outcome were analyzed retrospectively in a consecutive series of 12 patients with primary MFH-T treated at the Cancer Hospital of the Chinese Academy of Medical Sciences from 1987 to 2007. RESULTS: All 12 patients underwent surgery; surgery alone was used in four patients. Five patients were given post-operative radiotherapy, and one patient was given pre-operative radiotherapy. Two patients were given post-operative chemotherapy. Five patients had locoregional recurrence, and five had distant metastases in follow-up. Median survival was 9 months. One patient is alive, and has no evidence of disease. Six patients died six months after treatment, and the other four patients died in 10, 14, 18, and 24 months after treatment, respectively. Nine patients died of the disease, and one patient died of cerebral hemorrhage after treatment. CONCLUSION: Primary MFH-T is very rare and has a poor prognosis. Although surgical resection of MFH-T is the treatment of choice in MFH-T, the results are unsatisfactory.

The role of adrenomedullin and its receptor system in cardiovascular calcification of rat induced by Vitamin D(3) plus nicotine.

Adrenomedullin (ADM) is a potent vasodilatory peptide which regulates blood pressure, cell growth and bone formation. Our work was aimed to explore the production of ADM, changes and pathophysiological significance of ADM mRNA and ADM receptor components--calcitonin receptor like receptor (CRLR) and receptor activity modifying proteins (RAMPs) mRNA in calcified myocardium and aorta of rats induced by Vitamin D3 plus nicotine. Contents of ADM in plasma, myocardium and aorta were measured by radioimmunoassay (RIA). The amount of ADM, CRLR and RAMPs mRNA was determined by semi-quantitative RT-PCR. The calcium content and alkaline phosphatase activity in myocardium and aorta of rats were measured. The results showed that the contents of calcium in calcified myocardium and aorta were increased by 3.5- and 6-fold (all P < 0.01), respectively, and alkaline phosphatases activity in calcified myocardium and aorta were increased by 66.5 and 82.7% (all P < 0.01 ), respectively, compared with control. Contents of ADM in plasma, myocardium and aorta were increased by 58% (P < 0.01), 14.3% (P < 0.01) and 27.8% P < 0.05). Furthermore, it was found that the amount of ADM, CRLR and RAMP2 mRNA in calcified myocardium was elevated by 90.6, 157.5 and 119.6% (all P < 0.01), RAMP3 mRNA was decreased by 14.1% (P < 0.01), respectively, compared with control. The amount of ADM, CRLR, RAMP2 and RAMP3 mRNA in calcified aorta was elevated by 37.7% (P < 0.01), 41.4% (P < 0.01), 60.1% (P < 0.05) and 13% P < 0.01), respectively, compared with control. The elevated level of CRLR and RAMP2 mRNA were in positive correlation with that of ADM mRNA (r = 0.992 and 0.882, respectively, P < 0.01) in calcified myocardium. The elevated level of CRLR and RAMP3 mRNA were also in positive correlation with that of ADM mRNA (r = 0.727, P < 0.05 and 0.816, P < 0.01, respectively) in calcified aorta. These results demonstrated that calcified myocardium and aorta generated an increased amount of ADM, up-regulated gene expressions of ADM, CRLR and RAMP2 mRNA. While the alteration of RAMP3 mRNA in calcified myocardium and aorta was different. These suggested that ADM and its receptor system might involve in the regulation of calcification in heart and aorta.

[The biochemical properties of L-arginine/nitric oxide pathway in rat brain mitochondria].

Biochemical property of L-arginine (L-Arg)/nitric oxide synthase (NOS)/nitric oxide (NO) system was observed in rat brain mitochondria. The results showed that there existed L-Arg transporters of high-affinity, low-transport and saturability in mitochondria membrane of normal rat brain. The maximum transport velocity (V(max)) and Michaelis constant (Km) were 5.87+/ -0.46 nmol/mg pro x min(-1) and 7.8+/- 0.56 micromol/L respectively. In normal condition, endothelium-type NOS was expressed in the mitochondria of rat brain, with its V(max) and Km being 2.7+/-0.3 nmol/mg pro x min(- 1) and 20.85+/-3.27 micromol/L, respectively. NO production was increased in a time-dependent manner and reached a maximum value at 60 min. These results suggest that the L-Arg transporters in MT membrane of normal rat brain were similar with Y(+) type amino acid transporters in cellullar membrane. Furthermore the NOS of mitochondria belongs to eNOS, whereas the L-Arg/NOS/NO system may be a source of NO.

[Experimental study on xiaoliu pingyi mixture with medicated serum in inducing apoptosis of human hepatocellular carcinoma cell line H-7402].

OBJECTIVE: To observe the efficacy of Xiaoliu Pingyi Mixture (XLPY) in inducing the apoptosis of human hepatocellular carcinoma (HCC) cell line H-7402. METHODS: Using serum pharmacologic method, the morphological change of apoptotic cells was observed at different time points by co-culturing with different concentrations of medicated serum containing XLPY with light and fluorescent microscopy, flow cytometry, and immunohistochemical staining methods. Blank serum was taken as control. RESULTS: The different concentration of medicated serum containing XLPY could significantly inhibit the growth of H-7402 cell line in vitro. After treated with medicated serum of XLPY, the cellular morphologic changes were typical apoptosis under light and fluorescent microscopy, the sub-G1 peaks were observed by flow cytometric assays. The apoptosis rate revealed a medicated serum concentration and time dependent manner. The control group 5%, 10% medicated serum induced apoptotic rate were 0.49%, 5.58% and 8.46% by 24 h; while by 48 h, it was 0.83%, 11.58% and 14.25% respectively. bcl-2 gene examination showed that the bcl-2 gene expression was inhibited. CONCLUSION: XLPY could induce apoptosis in carcinoma cells, and play the clinical role of anti-tumor and anti-metastasis.

[Ameliorative effects of adrenomedullin on rat cardiac sarcoplasmic reticulum injured by isoproterenol].

Five indices were used to assess the degree of the ameliorative effects of adrenomedullin (Adm) in isoproterenol (ISO) induced injury of cardiac sarcoplasmic reticulum (SR) of rats: +/- LV dp/dtmax, SR Ca2+ uptake, Ca2+ release (in nmol/mg SR protein) and Ca(2+)-ATPase activity. Adm (5 x 10(-5) mol/L) was perfused into rat heart before cardiac function +/- LV dp/dtmax was determined. Cardiac SR was purified and SR Ca2+ uptake, Ca2+ release, Ca(2+)-ATPase activity, and 3H-ryanodine maximal binding (Bmax) were measured. After perfusion of Adm (5 x 10(-5) mol/L), the +LV dp/dtmax and -LV dp/dtmax in ISO injured heart were increased by 16.9% (2,135 +/- 281 vs 1980 +/- 302, P < 0.05) and 29.2% (1375 +/- 267 vs 1064 +/- 355, P < 0.05), respectively. Cardiac SR Ca2+ uptake and Ca2+ release were increased by 23.0% (15.0 +/- 1.4 vs 12.2 +/- 1.2, P < 0.01) and 43.5% (6.6 +/- 1.0 vs 4.6 +/- 0.6, P < 0.01), respectively. Ca(2+)-ATPase activity and 3H-ryanodine binding were increased by 23.0% (P < 0.01) and 42.2% (P < 0.05), respectively. It seems that Adm exerted a protective effect on cardiac function in injured rat heart by enhancing SR Ca2+ uptake and release, suggesting that Adm may play a therapeutic role in myocardial injury.

Desensitization of adrenomedullin and calcitonin gene-related peptide receptors in vascular smooth muscle cells--effects of receptor activity-modifying protein.

Recent researches suggest that adrenomedullin (ADM) and calcitonin gene-related peptide (CGRP) bind to the same calcitonin receptor-like receptors (CRLR), with receptor specificity being determined by a receptor activity-modifying protein (RAMP). Our objective was to explore the significance of CRLR/RAMP hypothesis in cardiovascular tissues through experiments on the phenomenon of desensitization of both ADM and CGRP receptors using cultured rat aortic vascular smooth muscle cells (VSMCs). VSMCs were incubated for 20 min either in serum-free medium (SFM) alone or in the SFM containing vasoactive agonist [10(-8) mol/L ADM, CGRP and proadrenomedullin (PAMP)]. Cells were washed twice and incubated for another 20 min in SFM containing a repetitive agonist ADM or CGRP and 0.5 mmol/L isobutyryl methylxant (an inhibitor of phosphodiesterase). VSMCs were harvested and assayed for cAMP. Exposure of VSMCs to ADM, CGRP, or PAMP alone increased intracellular cAMP generation by 191% (P < 0.01), 385% (P < 0.01) and 67% (P < 0.05), respectively, compared with SFM group. Pre-treatment of VSMCs to ADM or CGRP decreased cAMP generation in response to subsequent stimulation with CGRP by 44% (P < 0.05) and 48% (P < 0.01), respectively. Pre-treatment of VSMCs with 100 nmol/L H-89, a protein kinase A (PKA) inhibitor, abolished the desensitization of CGRP-acting receptor, implying that this desensitization was mediated through PKA. In contrast, there was no attenuation in cAMP response to stimulation with ADM by pre-exposure to ADM or CGRP. Identical results were seen with or without PKA inhibition by H-89. Pre-exposure of VSMCs to PAMP resulted in no change in cAMP generation in response to subsequent stimulation with ADM or CGRP. These results indicate that ADM receptors do not desensitize in VSMCs in contrast to CGRP-receptors, which are desensitized by pre-exposure to ADM or CGRP. These data also suggest that the desensitization phenomenon of ADM is different from that of CGRP.

[Clinical observation of the effect of blood gas with two different methods of sputum suction].

The authors observed the preventive effect of the oxygen supplied double channel sucker on low blood oxygen. Thirty patients with channel sputum sucker under the mechanical respiratory support were taken as the contrast group, in comparison with the experimental group A and B respectively. Patients (n = 30) with one channel sputum sucking for 15 sec. were designated as experimental group A, while the other patients (n = 30) with the oxygen supplied double channel sucking for 15 sec were the group B, Blood gas analysis was done in every patient of each group. Significant difference of PO2 was found between group A and the contrast group (P < 0.01). No significant difference was found between group B and the contrast group (P > 0.05). It shows that oxygen supplied double channel sucker has preventive effect on low blood oxygen, and is suitable for sputum sucking in severe patients.

[Effects of Cu2+ on the neuromuscular junction transmission].

Experiments were carried out on the isolated rat phrenic nerve diaphragm preparations and chick biventer cervicis preparations. Cu2+ at cumulative concentrations inhibited muscle contractile response to indirect stimulation without affecting the conductivity of the nerve. The inhibiting action of Cu2+ on the muscle contractile response to indirect stimulation was stronger than that to direct stimulation. Cu2+ did not affect the Ach sensitivity of the chick biventer cervicis muscle. The effects of Cu2+ on neuromuscular transmission were antagonized by Ca2+ and L-cysteine. It is concluded that Cu2+ produces neuromuscular blockade by acting mainly on the presynaptic nerve terminals, binding with the -SH groups of the membrane and thus altering the transmembrane movement of Ca2+ and reducing the release of Ach from the nerve terminals.