Variation and covariation of external shape and cross-sectional geometry in the human metacarpus.

OBJECTIVES: Analyses of external bone shape using geometric morphometrics (GM) and cross-sectional geometry (CSG) are frequently employed to investigate bone structural variation and reconstruct activity in the past. However, the association between these methods has not been thoroughly investigated. Here, we analyze whole bone shape and CSG variation of metacarpals 1-5 and test covariation between them. MATERIALS AND METHODS: We analyzed external metacarpal shape using GM and CSG of the diaphysis at three locations in metacarpals 1-5. The study sample includes three modern human groups: crew from the shipwrecked Mary Rose (n = 35 metacarpals), a Pre-industrial group (n = 50), and a Post-industrial group (n = 31). We tested group differences in metacarpal shape and CSG, as well as correlations between these two aspects of metacarpal bone structure. RESULTS: GM analysis demonstrated metacarpus external shape variation is predominately related to changes in diaphyseal width and articular surface size. Differences in external shape were found between the non-pollical metacarpals of the Mary Rose and Pre-industrial groups and between the third metacarpals of the Pre- and Post-industrial groups. CSG results suggest the Mary Rose and Post-industrial groups have stronger metacarpals than the Pre-industrial group. Correlating CSG and external shape showed significant relationships between increasing external robusticity and biomechanical strength across non-pollical metacarpals (r: 0.815-0.535; p ≤ 0.05). DISCUSSION: Differences in metacarpal cortical structure and external shape between human groups suggest differences in the type and frequency of manual activities. Combining these results with studies of entheses and kinematics of the hand will improve reconstructions of manual behavior in the past.

Maternal oxidative stress during pregnancy associated with emotional and behavioural problems in early childhood: implications for foetal programming.

Childhood mental disorders, including emotional and behavioural problems (EBP) are increasingly prevalent. Higher maternal oxidative stress (OS) during pregnancy (matOSpreg) is linked to offspring mental disorders. Environmental factors contribute to matOSpreg. However, the role of matOSpreg in childhood EBP is unclear. We investigated the associations between (i) matOSpreg and offspring EBP; (ii) social and prenatal environmental factors and matOSpreg; and (iii) social and prenatal factors and childhood EBP and evaluated whether matOSpreg mediated these associations. Maternal urinary OS biomarkers, 8-hydroxyguanosine (8-OHGua; an oxidative RNA damage marker) and 8-hydroxy-2'-deoxyguanosine (8-OHdG; an oxidative DNA damage marker), at 36 weeks of pregnancy were quantified by liquid chromatography-mass spectrometry in a population-derived birth cohort, Barwon Infant Study (n = 1074 mother-infant pairs). Social and prenatal environmental factors were collected by mother-reported questionnaires. Offspring total EBP was measured by Child Behavior Checklist Total Problems T-scores at age two (n = 675) and Strengths and Difficulties Questionnaire Total Difficulties score at age four (n = 791). Prospective associations were examined by multivariable regression analyses adjusted for covariates. Mediation effects were evaluated using counterfactual-based mediation analysis. Higher maternal urinary 8-OHGua at 36 weeks (mat8-OHGua36w) was associated with greater offspring total EBP at age four (ß = 0.38, 95% CI (0.07, 0.69), P = 0.02) and age two (ß = 0.62, 95% CI (-0.06, 1.30), P = 0.07). Weaker evidence of association was detected for 8-OHdG. Five early-life factors were associated with both mat8-OHGua36w and childhood EBP (P-range < 0.001-0.05), including lower maternal education, socioeconomic disadvantage and prenatal tobacco smoking. These risk factor-childhood EBP associations were partly mediated by higher mat8-OHGua36w (P-range = 0.01-0.05). Higher matOSpreg, particularly oxidant RNA damage, is associated with later offspring EBP. Effects of some social and prenatal lifestyle factors on childhood EBP were partly mediated by matOSpreg. Future studies are warranted to further elucidate the role of early-life oxidant damage in childhood EBP.

Gastrointestinal-Specific symptom anxiety in patients with gastroparesis: Relationships to symptom severity and quality of life.

BACKGROUND: Gastrointestinal (GI)-specific anxiety has been identified as a treatment target in irritable bowel syndrome. However, GI-specific anxiety has been understudied in other GI functional/motility disorders. Among adults with gastroparesis, we aimed to: (1) initially validate a measure of GI-specific anxiety, the Visceral Sensitivity Index (VSI); and (2) evaluate the relationship between GI-specific anxiety and gastroparesis symptom severity and quality of life, compared to measures of anxiety, depression, and somatization. METHODS: Consecutive adult patients (N = 100) with gastroparesis presenting for initial consultation completed a series of self-report measures including the VSI. We conducted a confirmatory factor analysis of the VSI one-factor structure and tested internal consistency and convergent validity. We then performed hierarchical linear regression analyses to explore associations between VSI and gastroparesis symptom severity and overall quality of life. KEY RESULTS: Confirmatory factor analysis revealed that the original VSI one-factor structure overall fit well [χ2 (90) = 220.1, p < 0.0001; SRMR = 0.08; RMSEA = 0.12; CFI = 0.96]. The VSI also had excellent internal consistency (α = 0.99) and convergent validity (r = 0.29-0.56; all p < 0.01). Higher GI-specific anxiety was significantly associated with greater gastroparesis symptom severity, including nausea/vomiting, fullness/satiety, and upper abdominal pain scores beyond depression, anxiety, or somatization (all p = <0.01-0.01). Additionally, higher GI-specific anxiety was significantly associated with lower mental health-related quality of life, beyond gastroparesis symptom severity, depression, anxiety, or somatization (p = 0.01). CONCLUSIONS & INFERENCES: The VSI is an adequate measure of GI-specific anxiety in patients with gastroparesis. Higher GI-specific anxiety was associated with increased patient-reported gastroparesis symptom severity and decreased quality of life, beyond depression/anxiety.

Clinical Characteristics of Patients With Ineffective Esophageal Motility by Chicago Classification Version 4.0 Compared to Chicago Classification Version 3.0.

Background/Aims: Chicago classification version 4.0 (CCv4.0) of esophageal motility disorders developed a more stringent diagnostic criteria for ineffective esophageal motility (IEM) than version 3.0. We studied the implications of the new diagnostic criteria on the prevalence of IEM, and clinically characterized and compared the population of patients who no longer meet diagnostic criteria for IEM to those who retain the diagnosis. Methods: We included all consecutively performed high-resolution esophageal impedance manometries from 2014 to 2021. Three cohorts of patients with IEM were created: Patients with IEM by Chicago classification version 3.0 (CCv3.0; CC3 group), by CCv4.0 only (CC4 group), and by CCv3.0 who are now considered normal (Normal group). Demographics, manometric and reflux parameters, and clinical outcomes were compared. Results: A total of 594 manometries were analyzed. Of those, 66 (11.1%) met criteria for IEM by CCv3.0 (CC3), 41 (62.0%) retained an IEM diagnosis using CCv4.0 criteria (CC4), while 25 (38.0%) patients no longer met criteria for IEM (Normal). The CC4 group had higher esophageal acid exposure, especially supine (% time - 18.9% vs 2.2%; P = 0.005), less adequate peristaltic reserve (22.0% vs 88.0%; P = 0.003), and higher Demeester score (49.0 vs 21.2; P = 0.017) compared to the Normal group. There was no difference in bolus clearance between the groups. Conclusions: IEM under CCv4.0 has a stronger association with pathologic reflux, especially supine reflux, and inadequate peristaltic reserve, but impairment in bolus clearance is unchanged when compared with IEM diagnosed based on CCv3.0. Further studies are required to determine the implications of these findings on management strategies.

Inflammatory Bowel Disease and Helicobacter pylori: Protective or Present?

This article describes the prevalence of inflammatory bowel disease in patients with gastritis, duodenitis, and peptic ulcer disease, stratified by Helicobacter pylori infection. Inflammatory boweld is less prevalent in patients with H. pylori, and no increased risk of IBD is seen after H. pylori eradication therapy.

Trends in Gastroparesis Management: A United States Population-based Study From 2010 to 2020.

BACKGROUND: There is little consensus on the medical management of gastroparesis, a disorder characterized by delayed gastric emptying with symptoms of early satiety, nausea, vomiting, and upper abdominal pain. GOALS: We utilized population-level data to: (1) describe the prevalence of different pharmacological and nonpharmacological therapies in patients with gastroparesis; and (2) trend the prevalence of these therapies from 2010 to 2020. STUDY: More than 59 million unique medical records across 26 US-based major health care systems were surveyed using the Explorys platform to identify a cohort of adults with gastroparesis who completed both a gastric emptying study and upper endoscopy or upper gastrointestinal tract imaging. Prevalence of antiemetic, prokinetic, neuromodulator prescriptions, and surgical therapies for gastroparesis were searched within this cohort and trended annually from 2010 to 2020. RESULTS: Antiemetics (72% of patients), prokinetics (47%), and neuromodulators (75% of patients, 44% of patients without a concomitant psychiatric or diabetic peripheral neuropathy diagnosis) were all commonly used in the treatment of patients with gastroparesis. From 2010 to 2020, there was an increase in the prevalence of antiemetic and neuromodulator prescriptions (36.4% to 57.6%, P <0.001 and 47.0% to 66.9%, P <0.001, respectively), whereas the prevalence of prokinetics remained relatively constant (31.8% to 31.6%, P =0.52). Procedural and surgical treatments were used in 5% of gastroparesis patients. CONCLUSIONS: Treatments for gastroparesis have changed over the last decade: antiemetic and neuromodulator use has increased whereas prokinetic use has remained constant. This practice pattern may reflect the growing number and availability of antiemetics and neuromodulators and the small number and known side effects of prokinetics.

A Case of Upper Gastrointestinal Bleeding Due to Metastatic High-Grade B-Cell Lymphoma Successfully Treated With Chemotherapy.

Upper gastrointestinal bleeding (UGIB) is a common and potentially life-threatening condition. Metastatic disease is an exceedingly rare cause of UGIB. We report the case of a 73-year-old man with high-grade B-cell lymphoma (HGBL) who presented for the initiation of chemotherapy and was found to be acutely anemic due to UGIB. An esophagogastroduodenoscopy (EGD) revealed multiple large, discrete, ulcerated, non-circumferential, and friable masses in the stomach. Biopsies were consistent with HGBL. The patient was urgently initiated on chemotherapy with the resolution of lesions on subsequent EGD. The rate of prevalence of gastric metastases is unknown, but it should be considered in patients with active malignancy who present with signs of UGIB.

A Pathway-Based Genetic Score for Oxidative Stress: An Indicator of Host Vulnerability to Phthalate-Associated Adverse Neurodevelopment.

The developing brain is highly sensitive to environmental disturbances, and adverse exposures can act through oxidative stress. Given that oxidative stress susceptibility is determined partly by genetics, multiple studies have employed genetic scores to explore the role of oxidative stress in human disease. However, traditional approaches to genetic score construction face a range of challenges, including a lack of interpretability, bias towards the disease outcome, and often overfitting to the study they were derived on. Here, we develop an alternative strategy by first generating a genetic pathway function score for oxidative stress (gPFSox) based on the transcriptional activity levels of the oxidative stress response pathway in brain and other tissue types. Then, in the Barwon Infant Study (BIS), a population-based birth cohort (n = 1074), we show that a high gPFSox, indicating reduced ability to counter oxidative stress, is linked to higher autism spectrum disorder risk and higher parent-reported autistic traits at age 4 years, with AOR values (per 2 additional pro-oxidant alleles) of 2.10 (95% CI (1.12, 4.11); p = 0.024) and 1.42 (95% CI (1.02, 2.01); p = 0.041), respectively. Past work in BIS has reported higher prenatal phthalate exposure at 36 weeks of gestation associated with offspring autism spectrum disorder. In this study, we examine combined effects and show a consistent pattern of increased neurodevelopmental problems for individuals with both a high gPFSox and high prenatal phthalate exposure across a range of outcomes, including high gPFSox and high DEHP levels against autism spectrum disorder (attributable proportion due to interaction 0.89; 95% CI (0.62, 1.16); p < 0.0001). The results highlight the utility of this novel functional genetic score and add to the growing evidence implicating gestational phthalate exposure in adverse neurodevelopment.

Inhibitors of HIV-1 Nef-Mediated Activation of the Myeloid Src-Family Kinase Hck Block HIV-1 Replication in Macrophages and Disrupt MHC-I Downregulation.

HIV-1 Nef is an attractive target for antiretroviral drug discovery because of its role in promoting HIV-1 infectivity, replication, and host immune system avoidance. Here, we applied a screening strategy in which recombinant HIV-1 Nef protein was coupled to activation of the Src-family tyrosine kinase Hck, which enhances the HIV-1 life cycle in macrophages. Nef stimulates recombinant Hck activity in vitro, providing a robust assay for chemical library screening. High-throughput screening of more than 730 000 compounds using the Nef·Hck assay identified six unique hit compounds that bound directly to recombinant Nef by surface plasmon resonance (SPR) in vitro and inhibited HIV-1 replication in primary macrophages in the 0.04 to 5 µM range without cytotoxicity. Eighty-four analogs were synthesized around an isothiazolone scaffold from this series, many of which bound to recombinant Nef and inhibited HIV-1 infectivity in the low to submicromolar range. Compounds in this series restored MHC-I to the surface of HIV-infected primary cells and disrupted a recombinant protein complex of Nef with the C-terminal tail of MHC-I and the µ1 subunit of the AP-1 endocytic trafficking protein. Nef inhibitors in this class have the potential to block HIV-1 replication in myeloid cells and trigger recognition of HIV-infected cells by the adaptive immune system in vivo.

Prevalence and Clinical Characteristics of Dyssynergic Defecation and Slow Transit Constipation in Patients with Chronic Constipation.

Patients with chronic constipation who do not respond to initial treatments often need further evaluation for dyssynergic defecation (DD) and slow transit constipation (STC). The aims of this study are to characterize the prevalence of DD and STC in patients referred to a motility center with chronic constipation and correlate diagnoses of DD and STC to patient demographics, medical history, and symptoms. High-resolution ARM (HR-ARM), balloon expulsion testing (BET) and whole gut transit scintigraphy (WGTS) of consecutive patients with chronic constipation were reviewed. Patients completed questionnaires describing their medical history and symptoms at the time of testing. A total of 230 patients completed HR-ARM, BET, and WGTS. Fifty (22%) patients had DD, and 127 (55%) patients had STC. Thirty patients (13%) had both DD and STC. There were no symptoms that were suggestive of STC vs. DD; however, patients with STC and DD reported more severe constipation than patients with normal transit and anorectal function. Patients with chronic constipation often need evaluation for both DD and STC to better understand their pathophysiology of symptoms and help direct treatment.

Impact of patient position on esophageal motility disorders using high-resolution esophageal manometry with impedance (HREMI): supine versus upright swallows.

BACKGROUND: High-resolution esophageal manometry with impedance (HREMI) performed with supine patient positioning is used to evaluate patients for esophageal dysmotility. However, most patients experience symptoms related to esophageal dysmotility when eating or drinking upright. The aims of this study are to: (1) compare HREMI metrics in supine versus upright position; and (2) determine if upright position alters motility characterization of patients. METHODS: HREMI of twelve wet swallows in supine position and five wet swallows in upright position were performed on normal subjects (NS) and consecutive patients. Chicago Classification v3.0 (CC) diagnoses were evaluated in the supine position and a modified version of the Chicago Classification system was used in the upright position using normative upright values for DCI and IRP. RESULTS: DCI decreased in NS by 414 mmHg × cm × sec (p = 0.001) and patients by 613 mmHg × cm × sec (p < 0.001). IRP decreased in NS by 6.2 mmHg (p < 0.001) and patients by 4.6 mmHg (p < 0.001). The rate of successful bolus clearance decreased in the upright position in patients by 11% (p < 0.001), but no statistically significant differences were observed in NS. 82 of 200 patients (41%) had a change in CC diagnosis in the upright position. Bolus clearance in the upright position varied in patients depending on their diagnosis in the upright position. CONCLUSIONS: Upright swallows had lower LES, IRP, DCI and UES pressures in both normal subjects and patients with decreased bolus clearance in patients. Upright positioning can alter esophageal motility patterns and enhance diagnostic yield. Thus, upright swallows supplement supine swallows to help characterize esophageal dysmotility.

Common sampling and modeling approaches to analyzing readmission risk that ignore clustering produce misleading results.

BACKGROUND: There is little consensus on how to sample hospitalizations and analyze multiple variables to model readmission risk. The purpose of this study was to compare readmission rates and the accuracy of predictive models based on different sampling and multivariable modeling approaches. METHODS: We conducted a retrospective cohort study of 17,284 adult diabetes patients with 44,203 discharges from an urban academic medical center between 1/1/2004 and 12/31/2012. Models for all-cause 30-day readmission were developed by four strategies: logistic regression using the first discharge per patient (LR-first), logistic regression using all discharges (LR-all), generalized estimating equations (GEE) using all discharges, and cluster-weighted (CWGEE) using all discharges. Multiple sets of models were developed and internally validated across a range of sample sizes. RESULTS: The readmission rate was 10.2% among first discharges and 20.3% among all discharges, revealing that sampling only first discharges underestimates a population's readmission rate. Number of discharges was highly correlated with number of readmissions (r = 0.87, P < 0.001). Accounting for clustering with GEE and CWGEE yielded more conservative estimates of model performance than LR-all. LR-first produced falsely optimistic Brier scores. Model performance was unstable below samples of 6000-8000 discharges and stable in larger samples. GEE and CWGEE performed better in larger samples than in smaller samples. CONCLUSIONS: Hospital readmission risk models should be based on all discharges as opposed to just the first discharge per patient and utilize methods that account for clustered data.

Characterizing the proximal esophageal segment in patients with symptoms of esophageal dysmotility.

BACKGROUND: Proximal esophageal striated muscle contractility may be abnormal in patients with esophageal symptoms, but is not assessed in the Chicago Classification (CC) v3.0. We aimed to (a) determine the prevalence of abnormal proximal esophageal contractility in patients with esophageal symptoms; (b) compare proximal esophageal contractility in patients with different esophageal motility disorders; (c) assess the association of abnormal proximal esophageal contractility with esophageal symptoms. METHODS: Patients undergoing high-resolution esophageal manometry (HREM) from 7/2019 to 11/2019 and healthy volunteers (HVs) were studied. Measurements of the proximal esophageal segment included the vigor of contractility of the proximal esophagus (proximal contractile integral/PCI). Patients rated gastrointestinal symptoms' severity. KEY RESULTS: HREM was performed on 221 patients (63.8% females, mean age 57.1 ± 1.1 years) and 19 HVs. Mean PCI in HVs was 299.5 ± 30.6 (95% CI 32.3-566.7 mm Hg. s. cm). Of all patients, 61 (27.6%) had abnormal PCI. HVs and patients with different esophageal motility disorders had significantly different PCI (P < .01). Type 1 achalasia patients had weaker PCI than patients with absent contractility (P = .02). Patients with abnormal PCI had more severe dysphagia (P = .02), nausea (P = .03), vomiting (P = .03), and lower bolus clearance (P < .01) than patients with normal PCI. CONCLUSIONS AND INFERENCES: Abnormal PCI was found in a fourth of patients with esophageal symptoms. PCI may be useful to distinguish some esophageal motility disorders. Patients with abnormal PCI had a higher severity of some upper gastrointestinal symptoms than patients with normal PCI. Assessing the proximal esophageal segment on HREM may be useful in characterizing patients with esophageal symptoms.

Vascular pressure bands on high-resolution esophageal manometry with impedance studies.

Horizontal pressure bands on high-resolution esophageal manometry with impedance (HREMI) tracings are often seen and thought to be due to cardiovascular structures compressing the esophagus. The aim of this study was to determine the prevalence and location of vascular pressure bands on HREMI studies and correlate these pressure bands to bolus clearance. HREMI studies in supine and upright positions from patients and normal volunteers were reviewed. Pressure bands were defined as bands of horizontal pressure greater than the 20 mmHg isobaric contour. Each swallow was reviewed with impedance to determine if bolus transit was impaired by the band. 38.6% of 251 patients and 36.4% of 11 normal controls had a pressure band present. There were a greater number of bands in supine versus upright position (patients: 130 vs. 25, P < 0.001 and controls: 6 vs. 1). Patients with pressure bands had similar demographics (age, gender, BMI) compared to those without. Average distal contractile integral of bands was greater in supine compared to upright (133 ± 201 vs. 60 ± 148 mmHg cm s, P < 0.05). Bands were commonly located clustered at 46 and 72% of esophageal length. Bolus transit was impaired by bands in 20.4% of supine and 14.0% of upright swallows. Vascular pressure bands can have a prominent appearance on HREMI studies, present in, being more prevalent and having greater pressure in the supine than the upright position. These vascular bands, when present, may impair esophageal transit.

Influence of Mechanical Unloading on Articular Chondrocyte Dedifferentiation.

Due to the limited self-repair capacity of articular cartilage, the surgical restoration of defective cartilage remains a major clinical challenge. The cell-based approach, which is known as autologous chondrocyte transplantation (ACT), has limited success, presumably because the chondrocytes acquire a fibroblast-like phenotype in monolayer culture. This unwanted dedifferentiation process is typically addressed by using three-dimensional scaffolds, pellet culture, and/or the application of exogenous factors. Alternative mechanical unloading approaches are suggested to be beneficial in preserving the chondrocyte phenotype. In this study, we examined if the random positioning machine (RPM) could be used to expand chondrocytes in vitro such that they maintain their phenotype. Bovine chondrocytes were exposed to (a) eight days in static monolayer culture; (b) two days in static monolayer culture, followed by six days of RPM exposure; and, (c) eight days of RPM exposure. Furthermore, the experiment was also conducted with the application of 20 mM gadolinium, which is a nonspecific ion-channel blocker. The results revealed that the chondrocyte phenotype is preserved when chondrocytes go into suspension and aggregate to cell clusters. Exposure to RPM rotation alone does not preserve the chondrocyte phenotype. Interestingly, the gene expression (mRNA) of the mechanosensitive ion channel TRPV4 decreased with progressing dedifferentiation. In contrast, the gene expression (mRNA) of the mechanosensitive ion channel TRPC1 was reduced around fivefold to 10-fold in all of the conditions. The application of gadolinium had only a minor influence on the results. This and previous studies suggest that the chondrocyte phenotype is preserved if cells maintain a round morphology and that the ion channel TRPV4 could play a key role in the dedifferentiation process.

Discovery and evaluation of nNav1.5 sodium channel blockers with potent cell invasion inhibitory activity in breast cancer cells.

Voltage-gated sodium channels (VGSC) are a well-established drug target for anti-epileptic, anti-arrhythmic and pain medications due to their presence and the important roles that they play in excitable cells. Recently, their presence has been recognized in non-excitable cells such as cancer cells and their overexpression has been shown to be associated with metastatic behavior in a variety of human cancers. The neonatal isoform of the VGSC subtype, Nav1.5 (nNav1.5) is overexpressed in the highly aggressive human breast cancer cell line, MDA-MB-231. The activity of nNav1.5 is known to promote the breast cancer cell invasion in vitro and metastasis in vivo, and its expression in primary mammary tumors has been associated with metastasis and patient death. Metastasis development is responsible for the high mortality of breast cancer and currently there is no treatment available to specifically prevent or inhibit breast cancer metastasis. In the present study, a 3D-QSAR model is used to assist the development of low micromolar small molecule VGSC blockers. Using this model, we have designed, synthesized and evaluated five small molecule compounds as blockers of nNav1.5-dependent inward currents in whole-cell patch-clamp experiments in MDA-MB-231 cells. The most active compound identified from these studies blocked sodium currents by 34.9 ±â€¯6.6% at 1 µM. This compound also inhibited the invasion of MDA-MB-231 cells by 30.3 ±â€¯4.5% at 1 µM concentration without affecting the cell viability. The potent small molecule compounds presented here have the potential to be developed as drugs for breast cancer metastasis treatment.

Rapid adaptation to microgravity in mammalian macrophage cells.

Despite the observed severe effects of microgravity on mammalian cells, many astronauts have completed long term stays in space without suffering from severe health problems. This raises questions about the cellular capacity for adaptation to a new gravitational environment. The International Space Station (ISS) experiment TRIPLE LUX A, performed in the BIOLAB laboratory of the ISS COLUMBUS module, allowed for the first time the direct measurement of a cellular function in real time and on orbit. We measured the oxidative burst reaction in mammalian macrophages (NR8383 rat alveolar macrophages) exposed to a centrifuge regime of internal 0 g and 1 g controls and step-wise increase or decrease of the gravitational force in four independent experiments. Surprisingly, we found that these macrophages adapted to microgravity in an ultra-fast manner within seconds, after an immediate inhibitory effect on the oxidative burst reaction. For the first time, we provided direct evidence of cellular sensitivity to gravity, through real-time on orbit measurements and by using an experimental system, in which all factors except gravity were constant. The surprisingly ultra-fast adaptation to microgravity indicates that mammalian macrophages are equipped with a highly efficient adaptation potential to a low gravity environment. This opens new avenues for the exploration of adaptation of mammalian cells to gravitational changes.

Calcium-dependent deceleration of the cell cycle in muscle cells by simulated microgravity.

Of all our mechanosensitive tissues, skeletal muscle is the most developmentally responsive to physical activity. Conversely, restricted mobility due to injury or disease results in muscle atrophy. Gravitational force is another form of mechanical input with profound developmental consequences. The mechanical unloading resulting from the reduced gravitational force experienced during spaceflight results in oxidative muscle loss. We examined the early stages of myogenesis under conditions of simulated microgravity (SM). C2C12 mouse myoblasts in SM proliferated more slowly (2.23× less) as a result of their being retained longer within the G2/M phase of the cell cycle (2.10× more) relative to control myoblasts at terrestrial gravity. Blocking calcium entry via TRP channels with SKF-96365 (10-20 µM) accumulated myoblasts within the G2/M phase of the cell cycle and retarded their proliferation. On the genetic level, SM resulted in the reduced expression of TRPC1 and IGF-1 isoforms, transcriptional events regulated by calcium downstream of mechanical input. A decrease in TRPC1-mediated calcium entry thus appears to be a pivotal event in the muscle atrophy brought on by gravitational mechanical unloading. Hence, relieving the constant force of gravity on cells might prove one valid experimental approach to expose the underlying mechanisms modulating mechanically regulated developmental programs.