Motor unit firing patterns of lower leg muscles during isometric plantar flexion with flexed knee joint position.

The ankle flexor and extensor muscles are essential for pedal movements associated with car driving. Neuromuscular activation of lower leg muscles is influenced by the posture during a given task, such as the flexed knee joint angle during car driving. This study aimed to investigate the influence of flexion of the knee joint on recruitment threshold-dependent motor unit activity in lower leg muscles during isometric contraction. Twenty healthy participants performed plantar flexor and dorsiflexor isometric ramp contractions at 30 % of the maximal voluntary contraction (MVC) with extended (0°) and flexed (130°) knee joint angles. High-density surface electromyograms were recorded from medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) muscles and decomposed to extract individual motor units. The torque-dependent change (Δpps /Δ%MVC) of the motor unit activity of MG (recruited at 15 %MVC) and SOL (recruited at 5 %MVC) muscles was higher with a flexed compared with an extended knee joint (p < 0.05). The torque-dependent change of TA MU did not different between the knee joint angles. The motor units within certain limited recruitment thresholds recruited to exert plantar flexion torque can be excited to compensate for the loss of MG muscle torque output with a flexed knee joint.

Motor unit firing patterns on increasing force during force and position tasks.

Different neurophysiological strategies are used to perform angle adjustments during motor tasks such as car driving and force-control tasks using a fixed-rigid pedal. However, the difference in motor unit behavior in response to an increasing exerted force between tasks is unknown. This study aimed to investigate the difference in motor unit responsiveness on increasing force between force and position tasks. Twelve healthy participants performed ramp and hold contractions during ankle plantarflexion at 20% and 30% of the maximal voluntary contraction using a rigid pedal (force task) and a free pedal with an inertial load (position task). High-density surface electromyograms were recorded of the medial gastrocnemius muscle and decomposed into individual motor unit firing patterns. Ninety and hundred and nine motor units could be tracked between different target torques in each task. The mean firing rate increased and firing rate variability decreased on 10% maximal voluntary contraction force gain during both force and position tasks. There were no significant differences in these responses between the two tasks. Our results suggest that the motor unit firing rate is similarly regulated between force and position tasks in the medial gastrocnemius muscle with an increase in the exerted force.NEW & NOTEWORTHY Different neurophysiological strategies are used to perform a force control task and angle adjustment task. Our results showed that motor unit firing rate is similarly regulated between the two tasks in the medial gastrocnemius muscle with an increase in the exerted force. Although it is reported that position tasks contribute to early fatigue, it does not seem to be a particular problem for the increase in force.

Clinical characteristics of COVID-19 in 104 people with SARS-CoV-2 infection on the Diamond Princess cruise ship: a retrospective analysis.

BACKGROUND: The ongoing COVID-19 pandemic is a global threat. Identification of markers for symptom onset and disease progression is a pressing issue. We described the clinical features of people infected on board the Diamond Princess cruise ship who were diagnosed with asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or mild or severe COVID-19, on admission to the Self-Defense Forces Central Hospital (Tokyo, Japan) and at the end of observation. METHODS: This retrospective, single-centre study included participants with laboratory-detected SARS-CoV-2 infection who were admitted to the Self-Defense Forces Central Hospital from Feb 11 to Feb 25, 2020. Clinical records, laboratory data, and radiological findings were analysed. Clinical outcomes were followed up until discharge or Feb 26, 2020, whichever came first. We defined asymptomatic infection as SARS-CoV-2 infection with no history of clinical signs and symptoms, severe COVID-19 as clinical symptoms of pneumonia (dyspnoea, tachypnoea, peripheral capillary oxygen saturation <93%, and need for oxygen therapy), and mild COVID-19 as all other symptoms. Clinical features on admission were compared among patients with different disease severity, including asymptomatic infection, at the end of observation. We used univariable analysis to identify factors associated with symptomatic illness among asymptomatic people infected with SARS-CoV-2 and disease progression in patients with COVID-19. FINDINGS: Among the 104 participants included in the final analysis, the median age was 68 years (IQR 47-75) and 54 (52%) were male. On admission, 43 (41%) participants were classified as asymptomatic, 41 (39%) as having mild COVID-10, and 20 (19%) as having severe COVID-19. At the end of observation, 33 (32%) participants were confirmed as being asymptomatic, 43 (41%) as having mild COVID-19, and 28 (27%) as having severe COVID-19. Serum lactate hydrogenase concentrations were significantly higher in the ten participants who were asymptomatic on admission but developed symptomatic COVID-19 compared with the 33 participants who remained asymptomatic throughout the observation period (five [50%] vs four [12%] participants; odds ratio 7·25, 95% CI 1·43-36·70; p=0·020). Compared with patients with mild disease at the end of observation, patients with severe COVID-19 were older (median age 73 years [IQR 55-77] vs 60 years [40-71]; p=0·028) and had more frequent consolidation on chest CT (13 [46%] of 28 vs nine [21%] of 43; p=0·035) and lymphopenia (16 [57%] vs ten [23%]; p=0·0055) on admission. INTERPRETATION: Older age, consolidation on chest CT images, and lymphopenia might be risk factors for disease progression of COVID-19 and contribute to improved clinical management. FUNDING: None.

Comparison of biological features between severely immuno-deficient NOD/Shi-scid Il2rgnull and NOD/LtSz-scid Il2rgnull mice.

Biological background data up to 11 weeks of age and tumorigenic susceptibility to xenotransplantation with HeLa cells were compared between severely immuno-deficient NOG and NSG mice. The body weight was lower in NOG mice than in NSG mice. Severe depletion of peripheral blood lymphocytes and lymphoid hypoplasia that are well-known characteristics of these mice were equally observed. No lymphoproliferative lesions developed in any mouse of either strain. The occurrence of ectopic exocrine gland and cyst was a common finding in the thymus of both strains. In addition, minimal spongiotic change was observed in the medulla oblongata and spinal cord in both strains, and its incidence in female NOG mice was a little higher than that in NSG mice. In the adrenal, subcapsular cell hyperplasia that is known as an age-related change in non-genetically modified mice developed earlier and its incidence was higher in NSG mice than in NOG mice. The development of female genital organs of NOG mice was slightly retarded in comparison with that of NSG mice. To evaluate tumorigenic susceptibility to xenotransplantation, female mice were implanted in the dorsal subcutis with 1×103 to 1×106 cells/head of HeLa cells, and were checked up to 16 weeks after implantation. As a result, there was no significant strain difference on tumor formation rate and tumor volume. In conclusion, the present study clearly demonstrated that NOG and NSG mice showed no distinct strain differences in either biological features or biological disadvantages.

Trial application of oxygen and carbon isotope analysis in tooth enamel for identification of past-war victims for discriminating between Japanese and US soldiers.

Stable isotope analysis has undergone rapid development in recent years and yielded significant results in the field of forensic sciences. In particular, carbon and oxygen isotopic ratios in tooth enamel obtained from human remains can provide useful information for the crosschecking of morphological and DNA analyses and facilitate rapid on-site prescreening for the identification of remains. This study analyzes carbon and oxygen isotopic ratios in the tooth enamel of Japanese people born between 1878 and 1930, in order to obtain data for methodological differentiation of Japanese and American remains from the Second World War. The carbon and oxygen isotopic ratios in the tooth enamel of the examined Japanese individuals are compared to previously reported data for American individuals (born post WWII), and statistical analysis is conducted using a discrimination method based on a logistic regression analysis. The discrimination between the Japanese and US populations, including Alaska and Hawaii, is found to be highly accurate. Thus, the present method has potential as a discrimination technique for both populations for use in the examination of mixed remains comprising Japanese and American fallen soldiers.

Conophylline suppresses pancreatic stellate cells and improves islet fibrosis in Goto-Kakizaki rats.

Activin A is a differentiation factor for ß-cells and is effective to promote ß-cell neogenesis. Activin A is also an autocrine activator of pancreatic stellate cells, which play a critical role in fibrogenesis of the pancreas. Conophylline (CnP) is a natural compound, which reproduces the effect of activin on ß-cell differentiation and promotes ß-cell neogenesis when administered in vivo. However, its effect on stellate cells is not known. We therefore investigated the effect of CnP on stellate cells both in vitro and in vivo. Unlike activin A, CnP inhibited activation of cultured stellate cells and reduced the production of collagen. We then analyzed the involvement of stellate cells in islet fibrosis in Goto-Kakizaki (GK) rats, a model of type 2 diabetes mellitus. In pancreatic sections obtained from 6-wk-old GK rats, CD68-positive macrophages and glial fibrillary acidic protein- and α-smooth muscle actin-positive stellate cells infiltrated into islets. Later, the number of macrophages was increased, and the α-smooth muscle actin staining of stellate cells became stronger, indicating the involvement of stellate cells in islet fibrosis in GK rats. When CnP was administered orally for 4 wk, starting from 6 wk of age, invasion of stellate cells and macrophages was markedly reduced and islet fibrosis was significantly improved. The insulin content was twice as high in CnP-treated rats. These results indicate that CnP exerts antifibrotic actions both in vitro and in vivo and improves islet fibrosis in Goto-Kakizaki rats.

Extracellular matrix modulates insulin production during differentiation of AR42J cells: functional role of Pax6 transcription factor.

Extracellular matrix (ECM) modulates differentiation of pancreatic ß-cells during development. However, the mechanism by which ECM proteins modulate differentiation is not totally clear. We investigated the effect of ECM proteins on differentiation ß-cells in vitro. We investigated the effect of basement membrane ECM on differentiation of AR42J cells and rat ductal cells. First, we examined the effect of reconstituted basement membrane, Matrigel on differentiation of AR42J cells induced by activin and betacellulin. Matrigel augmented insulin production and increased the expression of GLUT2, SUR1, and glucokinase. Among various transcription factors investigated, Matrigel markedly upregulated the expression of Pax6. When Pax6 was overexpressed in cells treated with activin and betacellulin, the expression of insulin was upregulated. Conversely, knockdown of Pax6 significantly reduced the insulin expression in cells cultured on Matrigel. The effects of Matrigel on insulin-production and induction of Pax6 were reproduced partially by laminin-1, a major component of Matrigel, and inhibited by anti-integrin-ß1 antibody. Matrigel also enhanced the activation of p38 mitogen-activated kinase induced by activin and betacellulin, which was inhibited by anti-ß1 antibody. Finally, the effect of Matrigel on differentiation was reproduced in rat cultured ductal cells, and Matrigel also increased the expression of Pax6. These results indicate that basement membrane ECM augments differentiation of pancreatic progenitor cells to insulin-secreting cells by upregulating the expression of Pax6. .

Potent anti-tumor activity of a macrocycle-quinoxalinone class pan-Cdk inhibitor in vitro and in vivo.

Deregulation of cell-cycle control is a hallmark of cancer. Thus, cyclin-dependent kinases (Cdks) are an attractive target for the development of anti-cancer drugs. Here, we report the biological characterization of a highly potent pan-Cdk inhibitor with a macrocycle-quinoxalinone structure. Compound M inhibited Cdk1, 2, 4, 5, 6, and 9 with equal potency in the nM range and was selective against kinases other than Cdks. This compound inhibited multiple events in the cell cycle in vitro, including retinoblastoma protein (pRb) phosphorylation, E2F-dependent transcription, DNA replication (determined by bromodeoxyuridine incorporation), and mitosis completion (assayed by flow cytometry) in the 10 nM range. Moreover, this compound induced cell death, as determined by induction of the subG1 fraction, activated caspase-3, and anexin V. In vivo, Compound M showed anti-tumor efficacy at a tolerated dose. In a nude rat xenograft tumor model, an 8-h constant infusion of Compound M inhibited pRb phosphorylation and induced apoptosis in tumor cells at ~ 30 nM, which led to the inhibition of tumor growth. Immunosuppression was the only liability observed at this dose, but immune function returned to normal after 10 days. Suppression of pRb phosphorylation in tumor cells was clearly correlated with tumor cell growth inhibition and cell death in vitro and in vivo. In vivo, Compound M inhibited pRb phosphorylation in both tumor and gut crypt cells. Rb phosphorylation may be a suitable pharmacodynamic biomarker in both tumors and normal tissues for monitoring target engagement and predicting the efficacy of Compound M.

Biological characterization of 2-aminothiazole-derived Cdk4/6 selective inhibitor in vitro and in vivo.

Abnormalities in the p16INK4a/ cyclin-dependent kinase (Cdk)4, 6/ Retinoblastoma (Rb) pathway frequently occur in various human cancers. Thus, Cdk4/6 is an attractive target for cancer therapy. Here we report the biological characterization of a 2-aminothiazole-derived Cdk4/6 selective inhibitor, named Compound A in vitro and in vivo. Compound A potently inhibits Cdk4 and Cdk6 with high selectivity (more than 57-fold) against other Cdks and 45 serine/threonine and tyrosine kinases. Compound A inhibits Rb protein (pRb) phosphorylation at Ser780, inhibits E2F-dependent transcription, and induces cell-cycle arrest at G1 in the T98G human glioma cell line. Among 82 human cells derived from various tissues, cell lines derived from hematological cancers (leukemia/lymphoma) tended to be more sensitive to Compound A in cell proliferation assay. Rb-negative cells tended to be insensitive to Compound A, as we had expected. In a nude rat xenograft model, Compound A inhibited pRb phosphorylation and bromodeoxyuridine (BrdU) incorporation in Eol-1 xenograft tumor at plasma concentration of 510 nM. Interestingly Compound A only moderately inhibited those pharmacodynamic and cell cycle parameters of normal crypt cells in small intestine even at 5 times higher plasma concentration. In F344 rats, Compound A did not cause immunosuppression even at 17 times higher plasma conc. These results suggest that Cdk4/6 selective inhibitors only moderately affects on the cell cycle of normal proliferating tissues and has a safer profile than pan-Cdk inhibitor in vivo.

MK-5108, a highly selective Aurora-A kinase inhibitor, shows antitumor activity alone and in combination with docetaxel.

Aurora-A kinase is a one of the key regulators during mitosis progression. Aurora-A kinase is a potential target for anticancer therapies because overexpression of Aurora-A, which is frequently observed in some human cancers, results in aberrant mitosis leading to chromosomal instability and possibly tumorigenesis. MK-5108 is a novel small molecule with potent inhibitory activity against Aurora-A kinase. Although most of the Aurora-kinase inhibitors target both Aurora-A and Aurora-B, MK-5108 specifically inhibited Aurora-A kinase in a panel of protein kinase assays. Inhibition of Aurora-A by MK-5108 in cultured cells induced cell cycle arrest at the G(2)-M phase in flow cytometry analysis. The effect was confirmed by the accumulation of cells with expression of phosphorylated Histone H3 and inhibition of Aurora-A autophosphorylation by immunostaining assays. MK-5108 also induced phosphorylated Histone H3 in skin and xenograft tumor tissues in a nude rat xenograft model. MK-5108 inhibited growth of human tumor cell lines in culture and in different xenograft models. Furthermore, the combination of MK-5108 and docetaxel showed enhanced antitumor activities compared with control and docetaxel alone-treated animals without exacerbating the adverse effects of docetaxel. MK-5108 is currently tested in clinical trials and offers a new therapeutic approach to combat human cancers as a single agent or in combination with existing taxane therapies.

Administration of conophylline and betacellulin-delta4 increases the beta-cell mass in neonatal streptozotocin-treated rats.

The present study was conducted to examine the effect of administration of conophylline (CnP) and betacellulindelta4 (BTCdelta4) on the beta-cell mass in neonatal streptozotocin-treated rats (neonatal STZ rats). STZ (100 microg/g) was injected into neonatal rats, and then CnP (2 microg/g) and/or BTCdelta4 (200 pmol/g) were administered to neonatal STZ rats for 1 week. The plasma glucose concentration was monitored, and an intraperitoneal glucose tolerance test (ipGTT) was performed on day 8 and at 8 weeks after the STZ injection. In neonatal STZ rats treated with control solution (S group), the plasma glucose concentration increased for several days after the STZ injection, returned to nearly normal levels, and then increased gradually after six weeks of age. Eight weeks after the STZ-injection, the plasma glucose concentration was increased significantly compared to that of normal rats. The glucose response to ipGTT was significantly reduced in neonatal STZ rats treated with CnP (CnP group), BTCdelta4 (delta4 group) and CnP+BTCdelta4 (CnP+delta4 group). The beta-cell mass and the insulin content of the pancreas were significantly increased in the CnP group and delta4 group. The effect of CnP+delta4 was greater than that of CnP alone or BTCdelta4 alone. CnP+BTCdelta4 significantly increased the number of PDX-1-positive ductal cells and the number of insulin/BrdU double-positive ductal cells. These results indicate the efficacy of CnP and BTCdelta4 in increasing the beta-cells mass of neonatal STZ-treated rats.

Lithium-induced Hashimoto's encephalopathy: a case report.

OBJECTIVE: To report on a patient with Hashimoto's encephalopathy induced by lithium. PATIENT AND INTERVENTIONS: A 61-year-old woman with a type II bipolar disorder and a history of lithium-induced thyrotoxicosis associated with silent thyroiditis was hospitalized to treat a severe major depressive episode. Given long-term treatment with levothyroxine for hypothyroidism that had resulted from silent thyroiditis, endogenous hormone in thyroid follicles was assumed to be minimized by the negative feedback, decreasing risk of recurrent thyrotoxicosis if lithium were restarted. RESULTS: Lithium clearly relieved the patient's depressive symptoms, but after 40 days encephalopathy developed. Thyrotoxicosis was ruled out, and serum antithyroid antibody titers were elevated. In the cerebrospinal fluid, protein content was substantially elevated and antithyroid antibodies were detected. Encephalopathy resolved dramatically after course of intravenous pulse therapy with methylprednisolone. CONCLUSIONS: We believe that autoantibodies against antigens shared by the thyroid gland and the brain were induced by exposure to lithium, causing the patient to develop Hashimoto's encephalopathy.

Reversal of streptozotocin-induced hyperglycemia by continuous supply of betacellulin in mice.

Previous studies have shown the efficacy of betacellulin (BTC) to promote beta-cell regeneration. Because of its short half-life, however, the effect of BTC may have been underestimated. This study was conducted to assess the effect of continuous administration of BTC on beta-cell regeneration. Adenovirus vectors encoding proBTC (Ad-proBTC) and mature BTC (Ad-mBTC) were prepared, and the efficacy of secretion of BTC was compared in AML12 hepatocytes. When AML12 cells were infected with Ad-proBTC or Ad-mBTC, cells infected with Ad-mBTC secreted considerably larger amount of BTC. We then infused Ad-mBTC into the mouse tail vein. Expression of BTC was detected in the liver for at least 21 days, and serum BTC was maintained at approximately 1 ng/ml for 7 days. When Ad-mBTC was infused immediately after administration of STZ (170 mg/kg), elevation of the plasma glucose induced by STZ was markedly inhibited, and the plasma glucose concentration remained at less than 200 mg/dl for 21 days. The insulin content and the beta-cell mass were significantly increased in Ad-mBTC-infused mice. These results indicate that continuous administration of BTC is quite effective in promoting regeneration of beta-cells.

In vitro transdifferentiation of mature hepatocytes into insulin-producing cells.

Adenovirus-mediated gene transfer of pancreatic duodenal homeobox transcription factor PDX-1, especially its super-active version (PDX-1/VP16), induces the expression of pancreatic hormones in murine liver and reverses streptozotocin-induced hyperglycemia. Histological analyses suggest that hepatocytes are the major source of insulin-producing cells by PDX-1 gene transfer, although the conversion of cultured hepatocytes into insulin-producing cells remains to be elucidated. The present study was conducted to address this issue. Hepatocytes were isolated from adult rats. Then, PDX-1 or PDX-1/VP16 gene was introduced by using adenovirus vector. Two days later, the expression of insulin was detected at mRNA and protein levels. Transfection of PDX-1/VP16 was more efficient in converting hepatocytes to insulin-producing cells. Immunoreactivity of albumin was downregulated in transdifferentiated cells and some of them almost completely lost albumin expression. During the course of transdifferentiation, upregulation of mRNA for CK19 and alpha-fetoprotein was observed. When cultured in collagen-1 gel sandwich configuration, hepatocytes maintained their mature phenotype and did not proliferate. In this condition, transfer of PDX-1/VP16 also induced the expression of insulin. These results clearly indicate that hepatocytes possess a potential to transdifferentiate into insulin-producing cells in vitro.