Objective To investigate the relationship between primary pulmonary mucinous adenocarcinoma (PPMA) mass type and pneumonia type and their difference in malignant degree, and to analyze the role of clinical manifestations and CT features in the diagnosis of this disease. Methods The clinical data of PPMA patients admitted in the First Affiliated Hospital of Xiamen University from May 2011 to March 2022 were retrospectively analyzed. According to CT features, they were divided into a mass type group and a pneumonia type group. The clinical manifestations, CT features and the degree of malignancy between the two groups were analyzed and compared. Results A total of 57 PPMA patients were enrolled. There were 17 males and 40 females, with an average age of (53.82±10.65) years, and 28 (49%) patients had reversed hato-like sign. There were 42 patients in the mass type group and 15 patients in the pneumonia type group. PPMA often occurs in both lower lungs, with clinical manifestations mainly of coughing and expectorating white mucoid sputum. There were statistical differences between the two groups in the maximum diameter of tumor (P<0.001), boundary condition (P<0.001) and pleural indentation sign (P=0.019). There was no statistical difference between the two groups in Ki-67 index (P>0.05). Conclusion There is no statistical difference in the degree of malignancy between the two types of PPMA. Considering their clinical manifestations and differences in imaging features, it is supported that the pneumonia type is just a progression of the mass type. CT can present various manifestations, among which the reversed hato-like sign is expected to become an important imaging feature. Combined with a high proportion of solid components, pleural indentation sign, and vacuole sign, reversed hato-like sign can play a significant role in the diagnosis of PPMA.

Objective:To investigates the efficacy and safety of allogeneic hematopoietic stem cell transplantation(allo-HSCT)in treating older patients(≥60 years old)with hematologic malignancies.Methods:We conducted a retrospective study involving 67 patients aged 60 years and above, diagnosed with malignant hematological diseases, who received allo-HSCT at the Clinical Research Centrer for Haematologic Diseases of the First Affiliated Hospital of Soochow University between June 2015 and March 2023.We collected pre-transplant data, including the patients' age, gender, pre-transplantation disease risk stratification, disease status, and the haematopoietic cell transplantation comorbidity index(HCT-CI). We retrospectively analyzed clinical data regarding treatment-related toxicity, infections, acute and chronic graft-versus-host disease(a/cGVHD), as well as recurrent and non-recurrent deaths, to estimate the overall survival(OS)rate and event-free survival (EFS)rate.Results:Sixty-seven patients were included in the study, comprising 55 males(82.1%)and 12 females(17.9%), with a median age of 63(61, 65) years .The cohort consisted of 42 cases of acute myeloid leukaemia, 22 cases of myelodysplastic syndromes, and 3 cases of acute lymphoblastic leukaemia.The Kaplan-Meier analysis showed that the 1-year OS and EFS rates were 62.9% and 59.2%, respectively, while the 2-year OS and EFS rates were 55.3% and 51.8%, respectively.The cumulative incidence of 1-year non-relapse mortality and relapse was 25.4% and 21.2%, respectively.A total of 13 patients developed grade Ⅱ-Ⅳ aGVHD, with a 1-year cumulative incidence of 22.0%, and 7 patients developed cGVHD requiring treatment.When stratified by age group, the OS rate was higher in patients aged 60~64 years compared to those aged ≥65 years; however, this difference was not statistically significant(Log-rank χ2=0.99, P=0.317). In contrast, when stratified by disease load, the OS rate was significantly higher in the complete remission(CR)group than in the non-CR group, with a statistically significant difference(Log-rank χ2=15.04, P<0.001). When stratified by donor type, the OS rate was higher in the human leukocyte antigens (HLA) allogeneic group compared to the haploinsufficiency group; however, the difference was not statistically significant(Log-rank χ2=2.71, P=0.100). Twenty-seven patients died at an average of 125 days (range 3-1 054 days) after HSCT.The causes of death included leukemia recurrence in 9 cases (33.3%), infection in 8 cases (29.6%), GVHD in 5 cases (18.5%), poor implantation in 3 cases (11.1%), multi-organ failure in 1 case (3.7%), and cerebrovascular accident in 1 case (3.7%). The results of multifactorial analysis indicated that a pre-transplant tumor load greater than 5% was an independent risk factor for OS after transplantation ( HR=4.59, 95% CI: 2.01-10.42, P<0.001)as well as for disease recurrence ( OR=13.11, 95% CI: 1.96-87.87, P=0.008). Additionally, the occurrence of infection was identified as an independent risk factor for non-recurrent death after transplantation( OR=3.95, 95% CI: 1.13 to 13.71, P=0.031). Conclusions:For patients aged 60 years or older with hematologic malignancies, HSCT can serve as a viable treatment option, particularly for those with refractory recurrence and high cytogenetic risk, as it has the potential to significantly enhance prognosis and increase both EFS and OS rates.

Objective:To evaluate the efficacy and safety of intrasaccular flow disruptor in wide-necked intracranial aneurysms.Methods:One hundred and seventeen patients with wide-necked intracranial aneurysms treated with intrasaccular flow disruptor were collected from Department of Neurointervention (First Affiliated Hospital of Zhengzhou University), Department of Neurosurgery (Beijing Tiantan Hospital, Capital Medical University), Department of Cerebrovascular Surgery, Neurosurgery Center (Zhujiang Hospital, Southern Medical University), and Department of Neurosurgery (First Affiliated Hospital of Harbin Medical University) from August 2022 to March 2024. Raymond-Roy Occlusion Classification (RROC) was employed to evaluate aneurysm embolization immediately after procedure; cranial CT or MRI within 48 hours of embolization were performed to identify any new intracranial hemorrhage, subarachnoid hemorrhage, or new symptomatic cerebral infarction related to the intracranial aneurysms. Modified Rankin Scale (mRS) was used to assess the neurological function at discharge. Imaging follow-up and outpatient follow-up were performed at 6 months after embolization to evaluate the aneurysm occlusion degree and complications.Results:A total of 117 intrasaccular flow disruptors were implanted in 117 patients, with a technical success rate of 100%; 115 patients (98.3%) enjoyed successful one-time release of their disruptors, and 2 patients (1.7%) required retrieval and redirection of the disruptors before second successful attempt. Flow disruptor plus stent was performed in 13 patients (11.1%). Immediately after procedure, RROC grading I was noted in 3 patients, grading II in 51 patients and grading III in 63 patients. Cranial CT or MRI within 48 hours of embolization indicated no new intracranial hemorrhage, subarachnoid hemorrhage, or symptomatic cerebral infarction related to the intracranial aneurysms. All patients had mRS score of 0 at discharge. Eighty-three patients completed a 6-month follow-up (RROC grading I in 41 patients, grading II in 33 patients and grading III in 9 patients), without ischemic or hemorrhagic adverse events.Conclusion:The results of this study preliminarily suggest that intrasaccular flow disruptor is effective and safe in wide-necked intracranial aneurysms.

Objective:To evaluate the efficacy and safety of Neuroform Atlas stent-assisted coil embolization in patients with middle cerebral artery bifurcation aneurysms.Methods:A retrospective analysis was performed; the clinical data of 46 patients with middle cerebral artery bifurcation aneurysms accepted Neuroform Atlas stent-assisted coil embolization in First Affiliated Hospital of Zhengzhou University, Beijing Tiantan Hospital Affiliated to Capital Medical University, First Affiliated Hospital of Harbin Medical University, Zhujiang Hospital of Southern Medical University and First Affiliated Hospital of Chongqing Medical University from January 2022 to March 2024 were collected. There were 28 ruptured aneurysms (60.87%) and 18 unruptured aneurysms (39.13%). Follow-up was performed for more than 3 months; Raymond-Roy grading was used to evaluate the aneurysm embolization immediately after embolization and during follow-up; perioperative hemorrhagic or ischemic complications were recorded; modified Rankin Scale (mRS) was used to evaluate the prognosis of the patients at discharge and during follow-up (mRS score≤2: good prognosis, and mRS score>2: poor prognosis).Results:Coil embolization was successful in all 46 patients. DSA immediately after embolization showed that 41 patients (89.13%) had completely occluded aneurysms (Raymond-Roy grading I), 2 patients (4.35%) had residual aneurysm neck (Raymond-Roy grading Ⅱ) and 3 patients (6.52%) had partially occluded aneurysms (Raymond-Roy grading Ⅲ). Perioperative complications occurred in 5 patients, including 2 with postoperative cerebral infarction, 1 with hydrocephalus, 1 with postoperative pneumonia leading to respiratory failure, and 1 with stent thrombosis during embolization. Both at discharge and 3 months after embolization, 43 patients (93.48%) had good prognosis and 3 patients (6.52%) had poor prognosis. No obvious ischemic complications (such as stent restenosis) or hemorrhagic complications (such as re-rupture of the aneurysms) were found in all patients. Thirty patients (65.22%) had imaging follow-up for 6-12 months: 26 (86.67%) had Raymond-Roy grading I, 3 (10.00%) had Raymond-Roy grading II, and 1 (3.33%) had Raymond-Roy grading III.Conclusion:Neuroform Atlas stent-assisted coil embolization has good short-term efficacy and high safety in middle cerebral artery bifurcation aneurysms, but long-term follow-up observation is still needed to verify its efficacy.

Objective:To investigate the effects of 10° head up tilt bed rest (HUT) on human cardiac function via 3D speckle tracking echocardiography (3D-STE), and to study the difference in cardiac function under the submaximal exercise load between the horizontal position and 10° HUBR.Methods:Thirty young healthy volunteers were recruited as the subjects, who were randomly divided into an 10° HUT exercise group and horizontal exercise group with 15 subjects in each. Subjects in both groups were asked to ride the bicycle ergometer in the 10° HUBR position and supine position respectively. The load started with 50 W and was increased by 25 W every 3 min until it reached the maximum of 125 W. Before the exercise (resting state), 1 min after the load was increased each time, and 3 min after exercise (recovery period), the following indices were collected: ①basic cardiac function indices: heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP), ②conventional cardiac ultrasound indices: left ventricular ejection fraction (LVEF), stroke volume (SV) and cardiac output (CO), ③left ventricular strain indices: global longitudinal strain (GLS), global circumferential strain (GCS), and global area strain (GAS) measured by 3D-SET. The changes of these indices in the 2 groups of subjects under different exercise loads were observed.Results:The differences in the major effect of the basic heart indices (HR, SBP and DBP), conventional cardiac ultrasound indices (LVEF, SV and CO) and left ventricular strain indices (GLS, GCS and GAS) in response to the exercise load were statistically significant ( F=194.90, 113.66, 17.19, P=0.017, 0.018, 0.001). With the increase of the exercise load, the basic heart indices and conventional cardiac ultrasound indices kept rising, the left ventricular strain indices reached the minimum under a moderate exercise load (75 W), HR, SBP and CO were higher than those of the resting state ( P<0.05 or 0.01). Both LVEF under exercise loads of 75, 100, 125 W and during recovery, and SV under exercise loads of 100, 125 W and during recovery were significantly higher than those of the resting state ( P<0.05 or 0.01), while GLS and GCS under exercise loads of 50, 75, 125 W ( P<0.05 or 0.01), and GAS under exercise loads of 50, 75 W ( P<0.01) were significantly lower. There were statistically significant differences not only in GCS across the groups ( F=4.60, P=0.026) but also in DBP due to the interactions between the grouping and exercise loads ( F=3.13, P=0.031). DBP was higher than that of the resting state when the exercise load was 125 W in both groups. Conclusions:During submaximal exercise, myocardial contractility shows sustained enhancement with the increase of the exercise load. The results of GLS, GCS and GAS indicate that myocardial strain reaches its lowest value under a moderate exercise load, suggesting that moderate exercise can be used to evaluate cardiac function via 3D-SET. Under a simulated lunar gravity of 10° HUT, there is less deformation in the short axis direction of the myocardium, indicating that GCS can be used as a sensitive indicator to detect changes in cardiac function under different gravities.

Objective:To identify protein markers that may be associated with ulcerative colitis(UC)by analyzing differential proteins in the salivary exosomes from newly diagnosed patients with active UC and healthy controls(HC),and to investigate the function of salivary exosome-specific high-expression proteins in UC patients and their potential role in the pathogenesis of UC.Methods:All patients and healthy controls were recruited from Peking University People's Hospital.Whole saliva was obtained from 37 patients with newly diagnosed active ulcerative colitis(n=37)and apparently healthy controls(n=10).Salivary exosomes were extracted from samples,and the proteins within the exosomes were identi-fied by liquid chromatograph-mass spectrometer(LC-MS/MS).The differentially expressed protein genes underwent gene ontology(GO)and Kyoto encyclopedia of genes and genomes(KEGG)enrichment analysis using the DAVID tool.In vitro,macrophages were co-cultured with salivary exosomes from UC group and those from HC group,respectively,and real-time quantitative polymerase chain reaction(qPCR)was used to detect levels of CD80+and CD86+.Additionally,ELISA was performed to measure secretion levels of interleukin-6(IL-6),interleukin-1β(IL-1β),tumor necrosis factor-α(TNF-α)in the cell supernatant.Results:A total of 259 proteins were co-expressed in saliva exosomes from UC group and HC group,among which 11 proteins were highly expressed in the UC group,including PDIA4,A2M,EEF2,C3,PSMA2,PSMB6,PSMA1,IGHG1,IGHG3,IGHG4 and SERPING1,while 4 proteins were lowly expressed in UC group,including TCN1,SLPI and SERPING.Functional analysis of these 15 pro-teins,along with 129 specific proteins found only in the UC patients and 69 specific proteins found only in HC patients,respectively,was conducted using GO/KEGG.The results revealed that in the UC group,proteasome-related proteins such as PSMA1,PSMA2 and PSMB6 expressions were increased in salivary ex-osomes while many key molecules involved in complement cascade pathways,such as C3 were up-regu-lated.In vitro co-culture experiments demonstrated that compared with healthy controls,the salivary exo-somes of the UC patients in active stage could play a pro-inflammatory role by promoting the transformation of macrophages into M1 type cells that secrete inflammatory factors IL-1β,IL-6 and TNF-α.Conclusion:Salivary exosomes in the UC patients may have the function of promoting inflammation.Analysis of protein levels in the saliva of the UC patients and healthy controls revealed significant differences in the expression levels of 15 co-expressed proteins between the two groups.Among them,C3,PSMA2,PSMB6 and PSMA1 were found to be mainly related to immune and inflammatory reactions in the UC group.These findings sug-gest that proteins with high specific expression in salivary exosomes of the UC patients have the potential to be used as a disease marker for UC diagnosis and may contribute to the pathogenesis of UC.

Objective:To investigates the efficacy and safety of allogeneic hematopoietic stem cell transplantation(allo-HSCT)in treating older patients(≥60 years old)with hematologic malignancies.Methods:We conducted a retrospective study involving 67 patients aged 60 years and above, diagnosed with malignant hematological diseases, who received allo-HSCT at the Clinical Research Centrer for Haematologic Diseases of the First Affiliated Hospital of Soochow University between June 2015 and March 2023.We collected pre-transplant data, including the patients' age, gender, pre-transplantation disease risk stratification, disease status, and the haematopoietic cell transplantation comorbidity index(HCT-CI). We retrospectively analyzed clinical data regarding treatment-related toxicity, infections, acute and chronic graft-versus-host disease(a/cGVHD), as well as recurrent and non-recurrent deaths, to estimate the overall survival(OS)rate and event-free survival (EFS)rate.Results:Sixty-seven patients were included in the study, comprising 55 males(82.1%)and 12 females(17.9%), with a median age of 63(61, 65) years .The cohort consisted of 42 cases of acute myeloid leukaemia, 22 cases of myelodysplastic syndromes, and 3 cases of acute lymphoblastic leukaemia.The Kaplan-Meier analysis showed that the 1-year OS and EFS rates were 62.9% and 59.2%, respectively, while the 2-year OS and EFS rates were 55.3% and 51.8%, respectively.The cumulative incidence of 1-year non-relapse mortality and relapse was 25.4% and 21.2%, respectively.A total of 13 patients developed grade Ⅱ-Ⅳ aGVHD, with a 1-year cumulative incidence of 22.0%, and 7 patients developed cGVHD requiring treatment.When stratified by age group, the OS rate was higher in patients aged 60~64 years compared to those aged ≥65 years; however, this difference was not statistically significant(Log-rank χ2=0.99, P=0.317). In contrast, when stratified by disease load, the OS rate was significantly higher in the complete remission(CR)group than in the non-CR group, with a statistically significant difference(Log-rank χ2=15.04, P<0.001). When stratified by donor type, the OS rate was higher in the human leukocyte antigens (HLA) allogeneic group compared to the haploinsufficiency group; however, the difference was not statistically significant(Log-rank χ2=2.71, P=0.100). Twenty-seven patients died at an average of 125 days (range 3-1 054 days) after HSCT.The causes of death included leukemia recurrence in 9 cases (33.3%), infection in 8 cases (29.6%), GVHD in 5 cases (18.5%), poor implantation in 3 cases (11.1%), multi-organ failure in 1 case (3.7%), and cerebrovascular accident in 1 case (3.7%). The results of multifactorial analysis indicated that a pre-transplant tumor load greater than 5% was an independent risk factor for OS after transplantation ( HR=4.59, 95% CI: 2.01-10.42, P<0.001)as well as for disease recurrence ( OR=13.11, 95% CI: 1.96-87.87, P=0.008). Additionally, the occurrence of infection was identified as an independent risk factor for non-recurrent death after transplantation( OR=3.95, 95% CI: 1.13 to 13.71, P=0.031). Conclusions:For patients aged 60 years or older with hematologic malignancies, HSCT can serve as a viable treatment option, particularly for those with refractory recurrence and high cytogenetic risk, as it has the potential to significantly enhance prognosis and increase both EFS and OS rates.

Objective:To evaluate the efficacy and safety of intrasaccular flow disruptor in wide-necked intracranial aneurysms.Methods:One hundred and seventeen patients with wide-necked intracranial aneurysms treated with intrasaccular flow disruptor were collected from Department of Neurointervention (First Affiliated Hospital of Zhengzhou University), Department of Neurosurgery (Beijing Tiantan Hospital, Capital Medical University), Department of Cerebrovascular Surgery, Neurosurgery Center (Zhujiang Hospital, Southern Medical University), and Department of Neurosurgery (First Affiliated Hospital of Harbin Medical University) from August 2022 to March 2024. Raymond-Roy Occlusion Classification (RROC) was employed to evaluate aneurysm embolization immediately after procedure; cranial CT or MRI within 48 hours of embolization were performed to identify any new intracranial hemorrhage, subarachnoid hemorrhage, or new symptomatic cerebral infarction related to the intracranial aneurysms. Modified Rankin Scale (mRS) was used to assess the neurological function at discharge. Imaging follow-up and outpatient follow-up were performed at 6 months after embolization to evaluate the aneurysm occlusion degree and complications.Results:A total of 117 intrasaccular flow disruptors were implanted in 117 patients, with a technical success rate of 100%; 115 patients (98.3%) enjoyed successful one-time release of their disruptors, and 2 patients (1.7%) required retrieval and redirection of the disruptors before second successful attempt. Flow disruptor plus stent was performed in 13 patients (11.1%). Immediately after procedure, RROC grading I was noted in 3 patients, grading II in 51 patients and grading III in 63 patients. Cranial CT or MRI within 48 hours of embolization indicated no new intracranial hemorrhage, subarachnoid hemorrhage, or symptomatic cerebral infarction related to the intracranial aneurysms. All patients had mRS score of 0 at discharge. Eighty-three patients completed a 6-month follow-up (RROC grading I in 41 patients, grading II in 33 patients and grading III in 9 patients), without ischemic or hemorrhagic adverse events.Conclusion:The results of this study preliminarily suggest that intrasaccular flow disruptor is effective and safe in wide-necked intracranial aneurysms.

Objective:To evaluate the efficacy and safety of Neuroform Atlas stent-assisted coil embolization in patients with middle cerebral artery bifurcation aneurysms.Methods:A retrospective analysis was performed; the clinical data of 46 patients with middle cerebral artery bifurcation aneurysms accepted Neuroform Atlas stent-assisted coil embolization in First Affiliated Hospital of Zhengzhou University, Beijing Tiantan Hospital Affiliated to Capital Medical University, First Affiliated Hospital of Harbin Medical University, Zhujiang Hospital of Southern Medical University and First Affiliated Hospital of Chongqing Medical University from January 2022 to March 2024 were collected. There were 28 ruptured aneurysms (60.87%) and 18 unruptured aneurysms (39.13%). Follow-up was performed for more than 3 months; Raymond-Roy grading was used to evaluate the aneurysm embolization immediately after embolization and during follow-up; perioperative hemorrhagic or ischemic complications were recorded; modified Rankin Scale (mRS) was used to evaluate the prognosis of the patients at discharge and during follow-up (mRS score≤2: good prognosis, and mRS score>2: poor prognosis).Results:Coil embolization was successful in all 46 patients. DSA immediately after embolization showed that 41 patients (89.13%) had completely occluded aneurysms (Raymond-Roy grading I), 2 patients (4.35%) had residual aneurysm neck (Raymond-Roy grading Ⅱ) and 3 patients (6.52%) had partially occluded aneurysms (Raymond-Roy grading Ⅲ). Perioperative complications occurred in 5 patients, including 2 with postoperative cerebral infarction, 1 with hydrocephalus, 1 with postoperative pneumonia leading to respiratory failure, and 1 with stent thrombosis during embolization. Both at discharge and 3 months after embolization, 43 patients (93.48%) had good prognosis and 3 patients (6.52%) had poor prognosis. No obvious ischemic complications (such as stent restenosis) or hemorrhagic complications (such as re-rupture of the aneurysms) were found in all patients. Thirty patients (65.22%) had imaging follow-up for 6-12 months: 26 (86.67%) had Raymond-Roy grading I, 3 (10.00%) had Raymond-Roy grading II, and 1 (3.33%) had Raymond-Roy grading III.Conclusion:Neuroform Atlas stent-assisted coil embolization has good short-term efficacy and high safety in middle cerebral artery bifurcation aneurysms, but long-term follow-up observation is still needed to verify its efficacy.

Objective:To investigate the effects of 10° head up tilt bed rest (HUT) on human cardiac function via 3D speckle tracking echocardiography (3D-STE), and to study the difference in cardiac function under the submaximal exercise load between the horizontal position and 10° HUBR.Methods:Thirty young healthy volunteers were recruited as the subjects, who were randomly divided into an 10° HUT exercise group and horizontal exercise group with 15 subjects in each. Subjects in both groups were asked to ride the bicycle ergometer in the 10° HUBR position and supine position respectively. The load started with 50 W and was increased by 25 W every 3 min until it reached the maximum of 125 W. Before the exercise (resting state), 1 min after the load was increased each time, and 3 min after exercise (recovery period), the following indices were collected: ①basic cardiac function indices: heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP), ②conventional cardiac ultrasound indices: left ventricular ejection fraction (LVEF), stroke volume (SV) and cardiac output (CO), ③left ventricular strain indices: global longitudinal strain (GLS), global circumferential strain (GCS), and global area strain (GAS) measured by 3D-SET. The changes of these indices in the 2 groups of subjects under different exercise loads were observed.Results:The differences in the major effect of the basic heart indices (HR, SBP and DBP), conventional cardiac ultrasound indices (LVEF, SV and CO) and left ventricular strain indices (GLS, GCS and GAS) in response to the exercise load were statistically significant ( F=194.90, 113.66, 17.19, P=0.017, 0.018, 0.001). With the increase of the exercise load, the basic heart indices and conventional cardiac ultrasound indices kept rising, the left ventricular strain indices reached the minimum under a moderate exercise load (75 W), HR, SBP and CO were higher than those of the resting state ( P<0.05 or 0.01). Both LVEF under exercise loads of 75, 100, 125 W and during recovery, and SV under exercise loads of 100, 125 W and during recovery were significantly higher than those of the resting state ( P<0.05 or 0.01), while GLS and GCS under exercise loads of 50, 75, 125 W ( P<0.05 or 0.01), and GAS under exercise loads of 50, 75 W ( P<0.01) were significantly lower. There were statistically significant differences not only in GCS across the groups ( F=4.60, P=0.026) but also in DBP due to the interactions between the grouping and exercise loads ( F=3.13, P=0.031). DBP was higher than that of the resting state when the exercise load was 125 W in both groups. Conclusions:During submaximal exercise, myocardial contractility shows sustained enhancement with the increase of the exercise load. The results of GLS, GCS and GAS indicate that myocardial strain reaches its lowest value under a moderate exercise load, suggesting that moderate exercise can be used to evaluate cardiac function via 3D-SET. Under a simulated lunar gravity of 10° HUT, there is less deformation in the short axis direction of the myocardium, indicating that GCS can be used as a sensitive indicator to detect changes in cardiac function under different gravities.