Alveolar rhabdomyosarcomas in conditional Pax3:Fkhr mice: cooperativity of Ink4a/ARF and Trp53 loss of function

Alveolar rhabdomyosarcoma is an aggressive childhood muscle cancer for which outcomes are poor when the disease is advanced. Although well-developed mouse models exist for embryonal and pleomorphic rhabdomyosarcomas, neither a spontaneous nor a transgenic mouse model of alveolar rhabdomyosarcoma has yet been reported. We report the first mouse model of alveolar rhabdomyosarcoma using a conditional Pax3:Fkhr knock-in allele whose activation in late embryogenesis and postnatally is targeted to terminally differentiating Myf6-expressing skeletal muscle. In these mice, alveolar rhabdomyosarcomas occur but at low frequency, and Fkhr haploinsufficiency does not appear to accelerate tumorigenesis. However, Pax3:Fkhr homozygosity with accompanying Ink4a/ARF or Trp53 pathway disruption, by means of conditional Trp53 or Ink4a/ARF loss of function, substantially increases the frequencies of tumor formation. These results of successful tumor generation postnatally from a target pool of differentiating myofibers are in sharp contrast to the birth defects and lack of tumors for mice with prenatal and postnatal satellite cell triggering of Pax3:Fkhr. Furthermore, these murine alveolar rhabdomyosarcomas have an immunohistochemical profile similar to human alveolar rhabdomyosarcoma, suggesting that this conditional mouse model will be relevant to study of the disease and will be useful for preclinical therapeutic testing.     

Regulation of the TSC pathway by LKB1: evidence of a molecular link between tuberous sclerosis complex and Peutz-Jeghers syndrome

Tuberous sclerosis complex (TSC) and Peutz-Jeghers syndrome (PJS) are dominantly inherited benign tumor syndromes that share striking histopathological similarities. Here we show that LKB1, the gene mutated in PJS, acts as a tumor suppressor by activating TSC2, the gene mutated in TSC. Like TSC2, LKB1 inhibits the phosphorylation of the key translational regulators S6K and 4EBP1. Furthermore, we show that LKB1 activates TSC2 through the AMP-dependent protein kinase (AMPK), indicating that LKB1 plays a role in cell growth regulation in response to cellular energy levels. Our results suggest that PJS and other benign tumor syndromes could be caused by dysregulation of the TSC2/mTOR pathway.     

The pharmacodynamic equivalence of levothyroxine and liothyronine: a randomized,double blind,cross‐over study in thyroidectomized patients

Context The substitution of liothyronine (L‐T3) for levothyroxine (L‐T4) is commonly employed during thyroid hormone (TH) withdrawal in preparation for diagnostic and therapeutic interventions on thyroid cancer patients. Presently, only limited data are available on the L‐T3 for L‐T4 therapeutic substitution. Objective To characterize the pharmcodynamic equivalence of L‐T3 and L‐T4. Design Randomized, double‐blind, cross‐over intervention study. Setting NIH clinical center. Patients Ten thyroidectomized patients. Interventions Study participants were treated with L‐T3 or L‐T4 with a target TSH ≥ 0·5 ≤ 1·5 mU/l for at least 30 days before undergoing inpatient testing. Following testing, subjects crossed‐over according to the same scheme. Main outcome measures Area under the serum concentration–time curve of TSH from 0 to 60 min (AUC_0–60) and peak TSH serum concentration (C_max) following thyrotropin‐releasing hormone (TRH) stimulation test, total L‐T4 and L‐T3 dose (mcg/kg), and L‐T4/L‐T3 ratio. Results No difference was observed for time 0 TSH values between L‐T3 and L‐T4 replacement phases (1·48 ± 0·77 vs. 1·21 ± 0·62 mU/l, P = 0·293) at average daily doses of 40·3 ± 11·3 mcg L‐T3 and 115·2 ± 38·5 mcg L‐T4, L‐T3: L‐T4 ratio 0·36 ± 0·06. TRH stimulation test resulted in similar L‐T3 vs. L‐T4 TSH responses with AUC_0–60 of 326·1 (95% CI 232·6–457·1) and 247·1 (95% CI 153·8–397·1) mU* min/l (P = 0·285); and C_max of 6·83 (95% CI 4·88–9·55) and 5·23 (95% CI 3·31–8·3) mU/l (P = 0·383). Conclusions This is the first study addressing the equivalency between L‐T3 and L‐T4 therapy measured by baseline and TRH‐stimulated TSH. The therapeutic substitution of L‐T3 for L‐T4 was achieved at approximately 1:3 ratio.     

Electroporation enhances transfection efficiency in murine cutaneous wounds

Transfection of wounds with DNA-encoding growth factors has the potential to improve healing, but current means of nonviral gene delivery are inefficient. Repeated high doses of DNA, necessary to achieve reliable gene expression, are detrimental to healing. We assessed the ability of in vivo electroporation to enhance gene expression. Full-thickness cutaneous excisional wounds were created on the dorsum of female mice. A luciferase- encoding plasmid driven by a CMV promoter was injected at the wound border. Following plasmid administration, electroporative pulses were applied to injection sites. Pulse parameters were varied over a range of voltage, duration, and number. Animals were euthanized at intervals after transfection and the luciferase activity measured. Application of electric pulses consistently increased luciferase expression. The electroporative effect was most marked at a plasmid dose of 50 micro g, where an approximate tenfold increase was seen. Six 100- micro s-duration pulses of 1750 V/cm were found to be the most effective in increasing luciferase activity. High numbers of pulses tended to be less effective than smaller numbers. This optimal electroporation regimen had no detrimental effect on wound healing. We conclude that electroporation increases the efficiency of transgene expression and may have a role in gene therapy to enhance wound healing.     

Pten constrains centroacinar cell expansion and malignant transformation in the pancreas

To determine the role of the phosphatidylinositol 3-kinase (PI3-K) pathway in pancreas development, we generated a pancreas-specific knockout of Pten, a negative regulator of PI3-K signaling. Knockout mice display progressive replacement of the acinar pancreas with highly proliferative ductal structures that contain abundant mucins and express Pdx1 and Hes1, two markers of pancreatic progenitor cells. Moreover, a fraction of these mice develop ductal malignancy. We provide evidence that ductal metaplasia results from the expansion of centroacinar cells rather than transdifferentiation of acinar cells. These results indicate that Pten actively maintains the balance between different cell types in the adult pancreas and that misregulation of the PI3-K pathway in centroacinar cells may contribute to the initiation of pancreatic carcinoma in vivo.     

Ginger lowers blood pressure through blockade of voltage-dependent calcium channels

Ginger (Zingiber officinale Roscoe), a well-known spice plant, has been used traditionally in a wide variety of ailments including hypertension. We report here the cardiovascular effects of ginger under controlled experimental conditions. The crude extract of ginger (Zo.Cr) induced a dose-dependent (0.3-3 mg/kg) fall in the arterial blood pressure of anesthetized rats. In guinea pig paired atria, Zo.Cr exhibited a cardiodepressant activity on the rate and force of spontaneous contractions. In rabbit thoracic aorta preparation, Zo.Cr relaxed the phenylephrine-induced vascular contraction at a dose 10 times higher than that required against K (80 mM)-induced contraction. Ca2+ channel-blocking (CCB) activity was confirmed when Zo.Cr shifted the Ca2+ dose-response curves to the right similar to the effect of verapamil. It also inhibited the phenylephrine (1 microM) control peaks in normal-Ca2+ and Ca2+-free solution, indicating that it acts at both the membrane-bound and the intracellular Ca2+ channels. When tested in endothelium-intact rat aorta, it again relaxed the K-induced contraction at a dose 14 times less than that required for relaxing the PE-induced contraction. The vasodilator effect of Zo.Cr was endothelium-independent because it was not blocked by L-NAME (0.1 mM) or atropine (1 microM) and also was reproduced in the endothelium-denuded preparations at the same dose range. These data indicate that the blood pressure-lowering effect of ginger is mediated through blockade of voltage-dependent calcium channels.     

Large deep venous anomaly presenting as a left frontal lesion

Venous angiomas` also known as deep vein anomalies (DVA), are one of the well-described brain vascular malformations. Frequently they are diagnosed as an incidental finding on neuroimaging (CT or MRI). A DVA may present as a single enhancing venous channel or as a large vascular abnormality illustrated on cerebral angiogram. Such a large DVA may mimic other intracranial lesions that mandate surgical intervention. We describe the radiological findings on CT, MRI, MRA and cerebral angiography of a 26-year-old male who presented with a few months` history of recurrent attacks of light-headiness, dizziness and slurring of speech that usually lasted for 2 minutes and resolved spontaneously. Cerebral angiography illustrated enlarged medullary veins draining into a central venous trunk then into the superior sagittal sinus resembling a caput medusa sign. Large DVAs may present radiologically as a brain lesion. Early recognition of these anomalies would avoid unnecessary or harmful intervention of this, otherwise, benign pathology.     

A closer look at food allergy and intolerance

Food allergy is a condition prevalent in over 2 percent of the world's population. The topic has been subject to research from ancient Greek times and continues to attract modern scientific and medical communities. In susceptible individuals certain foods produce a wide spectrum of unwanted effects like eczema, asthma, and urticaria. The management of food allergy and intolerance chiefly involves elimination diets, accurate diagnosis and detecting the causative mechanism providing us with ample food for thought. In this article, we have attempted to summarize and simplify the research on the various aspects of food allergy and intolerance, and discuss the natural history, manifestations, mechanisms, diagnosis, and management of this condition affecting countless worldwide.     

Pharmacological basis for the gut stimulatory activity of Raphanus sativus leaves

The crude extract of Raphanus sativus leaves (Rl.Cr) showed a dose-dependent (0.03-5.0 mg/ml) spasmogenicity in guinea-pig ileum and colon. The effect was insensitive to atropine pre-treatment but was completely abolished by pyrilamine indicating involvement of histaminergic (H(1)) receptors. The contractile effect at high doses (3.0-5.0mg/ml) was followed by relaxation. Rl.Cr also enhanced the transit of charcoal meal in mice at 30-100 mg/kg. The petroleum spirit, chloroform and aqueous fractions all showed histaminergic activity in ileum; aqueous fraction being more potent. The study shows the presence of a histaminergic component(s) along with a weak spasmolytic factor thus providing sound mechanistic basis for the traditional use of the plant in constipation.     

Antidiarrhoeal and spasmolytic activities of the methanolic crude extract of Alstonia scholaris L. are mediated through calcium channel blockade

This study was aimed to provide a pharmacological basis to the medicinal use of Alstonia scholaris as an antidiarrhoeal and antispasmodic by using in vivo and in vitro techniques. In the in vivo study the crude extract of Alstonia scholaris (As.Cr), which tested positive for the presence of alkaloids, provided 31–84% protection against castor oil‐induced diarrhoea in mice at 100–1000 mg/kg doses, similar to loperamide. In isolated rabbit jejunum preparation, the As.Cr caused inhibition of spontaneous and high K⁺ (80 mm )‐induced contractions, with respective EC₅₀ values of 1.04 (0.73–1.48) and 1.02 mg/mL (0.56–1.84; 95% CI), thus showing spasmolytic activity mediated possibly through calcium channel blockade (CCB). The CCB activity was further confirmed when pretreatment of the tissue with the As.Cr (0.3–1 mg/mL) caused a rightward shift in the Ca⁺⁺ concentration‐response curves similar to verapamil, a standard calcium channel blocker. Loperamide also inhibited spontaneous and high K⁺ precontractions as well as shifted the Ca⁺⁺ CRCs to the right. These results indicate that the crude extract of Alstonia scholaris possesses antidiarrhoeal and spasmolytic effects, mediated possibly through the presence of CCB‐like constituent(s) and this study provides a mechanistic base for its medicinal use in diarrhoea and colic. Copyright © 2009 John Wiley & Sons, Ltd.