Localization of the novel Xin protein to the adherens junction complex in cardiac and skeletal muscle during development.

Previously, we demonstrated that chick embryos treated with antisense oligonucleotides against a striated muscle-specific Xin exhibit abnormal cardiac morphogenesis (Wang et al. [1999] Development 126:1281-1294); therefore, we surmised a role for Xin in cardiac development. Herein, we examine the developmental expression of Xin through immunofluorescent staining of whole-mount mouse embryos and frozen heart sections. Xin expression is first observed within the heart tube of embryonic day 8.0 (E8.0) mice, exhibiting a peripheral localization within the cardiomyocytes. Colocalization of Xin with both beta-catenin and N-cadherin is observed throughout embryogenesis and into adulthood. Additionally, Xin is found associated with beta-catenin within the N-cadherin complex in embryonic chick hearts by coimmunoprecipitation. Xin is detected earlier than vinculin in the developing heart and colocalizes with vinculin at the intercalated disc but not at the sarcolemma within embryonic and postnatal hearts. At E10.0, Xin is also detected in the developing somites and later in the myotendon junction of skeletal muscle but not within the costameric regions of muscle. In cultured C2C12 myotubes, the Xin protein is found in many speckled and filamentous structures, coincident with tropomyosin in the stress fibers. Additionally, Xin is enriched in the regions of cell-cell contacts. These data demonstrate that Xin is one of the components at the adherens junction of cardiac muscle, and its counterpart in skeletal muscle, the myotendon junction. Furthermore, temporal and spatial expressions of Xin in relation to intercalated disc proteins and thin filament proteins suggest roles for Xin in the formation of cell-cell contacts and possibly in myofibrillogenesis.     

Circulating Fibronectin Controls Tumor Growth

Fibronectin is ubiquitously expressed in the extracellular matrix, and experimental evidence has shown that it modulates blood vessel formation. The relative contribution of local and circulating fibronectin to blood vessel formation in vivo remains unknown despite evidence for unexpected roles of circulating fibronectin in various diseases. Using transgenic mouse models, we established that circulating fibronectin facilitates the growth of bone metastases by enhancing blood vessel formation and maturation. This effect is more relevant than that of fibronectin produced by endothelial cells and pericytes, which only exert a small additive effect on vessel maturation. Circulating fibronectin enhances its local production in tumors through a positive feedback loop and increases the amount of vascular endothelial growth factor (VEGF) retained in the matrix. Both fibronectin and VEGF then cooperate to stimulate blood vessel formation. Fibronectin content in the tumor correlates with the number of blood vessels and tumor growth in the mouse models. Consistent with these results, examination of three separate arrays from patients with breast and prostate cancers revealed that a high staining intensity for fibronectin in tumors is associated with increased mortality. These results establish that circulating fibronectin modulates blood vessel formation and tumor growth by modifying the amount of and the response to VEGF. Furthermore, determination of the fibronectin content can serve as a prognostic biomarker for breast and prostate cancers and possibly other cancers.     

Synthesis,antitumor activity,distribution and toxicity of 4-[4-[Bis(2-chloroethyl)amino]phenyl]-1-hydroxybutane-1 1-bisphosphonic acid (BAD), a new lost derivative with increased accumulation in rat osteosarcoma

The aim of this study was to investigate whether the newly synthesized bisphosphonic acid-linked N-Lost derivative BAD retains bone-seeking and cytostatic properties. The paper describes experiments on mutagenicity in vitro and on toxicity in vivo. BAD is characterized by very low mutagenic activity toward histidine auxotrophic Salmonella typhimurium strains. Cytotoxic effects were tested in rat osteosarcoma and in Walker carcinosarcoma 256B. The LD50 of i.v. injected BAD was 146 mg/kg. Acute toxicity is probably caused by calcium complexing of the bisphosphonate part of the molecule. Labeling experiments showed moderate accumulation in bone and osteosarcoma, as well as in lung metastases. BAD effected high tumor growth inhibition in osteosarcoma and Walker carcinosarcoma-bearing rats and marked prolongation of survival; histologic and radiographic examination revealed rapid calcification of osteosarcoma and lung metastases. BAD-pretreatment produced protective effects against osteolysis induced by intratibially implanted Walker carcinosarcoma ascites cells. The cytostatic efficacy of equitoxic doses of BAD in rat osteosarcoma is comparable to that of dacarbazine and in Walker carcinosarcoma to that of melphalan.     

Elevated ANA titers in patients with severely abnormal gastrointestinal motility

We studied a group of six patients with clinical, radiological, and/or manometric features of severely abnormal gastrointestinal motility. Symptoms suggestive of esophageal, small bowel, or colonic involvement were present from 1 1/2 to 40 years. All patients had elevated antinuclear antibody (ANA) titers. None had clinical or radiographic features suggestive of progressive systemic sclerosis or other connective tissue diseases. Two patients had pathologic examinations of intestinal specimens, and these did not show changes suggestive of progressive systemic sclerosis. We conclude that patients with severe gastrointestinal motility disorders can have elevated ANA titers without features of progressive systemic sclerosis or other connective tissue diseases.This study was supported by the National Institutes of Health grant AM 25965 and grant RR 59 from the General Research Centers Program, Division of Research Resources, National Institutes of Health.     

Trypsinogen Activation Peptides (TAP) in Peritoneal Fluid as Predictors of Late Histopathologic Injury in Necrotizing Pancreatitis of the Rat

The levels of trypsinogen activation peptides(TAP) were quantified by ELISA immunoassay in acutepancreatitis of the rat and compared to the degree oflate histopathological sequelae and exocrine functional impairment 4 and 12 weeks after the acute phaseof the disease. For this purpose acute pancreatitis ofdifferent severity was induced using a suitable ratmodel recently described. Forty five surviving animals were studied. The level of TAP inperitoneal exudate measured 3 and 6 hr afterpancreatitis induction correlated well with the amountof the late histopathological injury at the end of thecorresponding observation period (at 4 weeks after 3 hr: r =0.75, P = 0.003, after 6 hr: r = 0.72, P = 0.005,Pearson; and at 12 weeks after 3 hr: r = 0.86, P =0.0001, after 6 hr: r = 0.84, P = 0.0001, Pearson). A negative correlation of TAP with the impairmentof exocrine function was found only at 4 weeks for thesecretion of total protein (r = –0.76 after 3 hr;r = –0.62 after 6 hr) and for exocrine function (r = –0.67 after 3 hr, r = –0.57 after6 hr), but not at 12 weeks after acute pancreatitis. Nocorrelation with plasma amylase and lipase was found. Weconclude that quantitation of TAP in ascites provides an accurate prediction of late histopathologicsequelae. Pancreatic exocrine function could bepredicted by TAP assay only in the early stage afterpancreatitis induction (eg, four weeks). In later stages of the disease (eg, 12 weeks) remainingpancreatic tissue seems to compensate for any exocrinedeficits that have occurred.     

Autonomic function test during the COVID-19 pandemic: the Stanford experience

Clinical Autonomic Research -