Ouabain stimulates atrial natriuretic peptide secretion via the endothelin-1/ET(B) receptor-mediated pathway in beating rabbit atria

AIMS

Ouabain has been reported to increase the secretion of atrial natriuretic peptide (ANP) in vitro. However, the mechanism by which ouabain increases ANP secretion is not well known. Therefore, the purpose of the present study was to investigate the underlying mechanism of ouabain-stimulated ANP secretion.

MAIN METHODS

A perfused beating rabbit atrial model was used. The ANP and ET-1 levels in the atrial perfusates were measured by radioimmunoassays.

KEY FINDINGS

Ouabain (1.0, 3.0 and 6.0 μmol/L) significantly increased atrial ANP secretion in a dose-dependent manner, while the endothelin (ET)-1 levels were increased by the higher doses (3.0 and 6.0 μmol/L) of ouabain. Ouabain-increased atrial ET-1 release was blocked by PD98059 (30.0 μmol/L), an inhibitor of mitogen-activated protein kinase (MAPK). Nifedipine (1.0 μmol/L), an inhibitor of L-type Ca(2+) channels, completely abolished ouabain-increased ANP secretion without changing the ouabain-induced atrial dynamics. KB-R7943 (3.0 μmol/L), an inhibitor of Na(+)-Ca(2+) exchangers, completely blocked the effects of ouabain-increased atrial dynamics, but did not modulate ouabain-increased ANP secretion. ET-1 significantly stimulated atrial ANP release in a dose-dependent manner. The effects of ET-1 and ouabain on ANP secretion were completely blocked by BQ788 (0.3 μmol/L), an inhibitor of ET-1 type B (ET(B)) receptors, but not by BQ123 (0.3 μM), an inhibitor of ET-1 type A receptors. Ouabain-increased atrial ANP secretion was blocked by PD98059 and indomethacin (30.0 μmol/L), an inhibitor of cyclooxygenase.

SIGNIFICANCE

Ouabain significantly stimulated atrial ANP secretion via an ET-1-ET(B) receptor-mediated pathway involving MAPK signaling pathway activation and prostaglandin formation.

Leaving a mark: the frequency and accuracy of tattooing prior to laparoscopic colorectal surgery

AIM

Intra-operative localization of small cancers and polyps during laparoscopic colorectal surgery is difficult due to reduced tactile feedback. The consequences of failing to identify the lesion for resection can result in open conversion or removal of the wrong segment of bowel.

METHOD

Data were collected from a prospectively-kept database over a 12-month period from April 2008 to March 2009 and analysed retrospectively. Details concerning the documentation, visibility and accuracy of tattoos were recorded.

RESULTS

Eighty-five patients (88 lesions) underwent laparoscopic resection for a benign or malignant colorectal tumour during 1 year from April 2008. Eighty-one patients underwent endoscopic visualization of the tumour as a first or second procedure. Of these 81 patients, 83 lesions were visualized endoscopically and 54 (65.1%) were tattooed in 52 patients. In the 52 patients, 36 (69%) of the tattoos were carried out on the first endoscopy. At operation the tattoo was judged to be visible and accurate in 70%, visible but inaccurate in 7% and not visible in 15%. It was significantly easier to see the tattoo in women (19/21 women vs 21/29 men; P=0.03) but there was no relationship between tattoo visibility and BMI. An accurate tattoo did not reduce the conversion rate (P=0.71). No tattoo-related complications were encountered.

CONCLUSION

The practice of tattooing colorectal cancers is variable in frequency, technique and accuracy. We advocate that all colonic lesions suspicious for cancer should be tattooed during endoscopy at a defined distance below the tumour, adhering to a departmental protocol in case surgery is required.

Toxicity of hypofractionated adjuvant radiation after breast-conserving surgery for DCIS

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Background: Traditional fractionation for whole breast radiation therapy after breast-conserving surgery has been 50Gy in 25 fractions over a 5-week period, with or without a 10 Gy boost. Hypofractionation has recently been adapted for early-stage invasive breast cancer, typically treating with 42.5 Gy in 16 daily fractions. This approach has been shown to have equivalent efficacy as the more traditional schedule. Its application to patients with DCIS has been an extrapolation of these data, and warrants further examination. This retrospective analysis reviews toxicity outcomes in women with DCIS treated with hypofractionation at our institution.

Methods: 59 women with DCIS treated with lumpectomy and hypofractionated radiotherapy with or without boost between 2006 and 2010 at the Einstein-Montefiore Cancer Center were identified. Median age was 65 (39-85). Median follow-up was 13.7 months (2–37.6). Surgical margin status was negative in 55, positive in 1, and unknown in 3. Thirteen patients had high-grade DCIS, 17 intermediate-grade, and 13 low-grade nuclear features, and 16 did not have grade delineation. 68% of patients (40 women) had disease that was positive both for ER and PR receptors, 2 women were simultaneously positive for ER and PR, 5 women had ER-only positive disease, 2 women had HER2-neu-only positive disease, 1 woman was positive for both ER and HER2-neu receptors, 1 woman was positive only for PR receptors, and 6 women were negative for all receptors; receptor status of specimens from 2 patients is not known. All women were treated with whole-breast hypofractionated therapy (42.4 Gy, in 16 fractions of 2.65 Gy each). 49 women received a boost to the lumpectomy cavity consisting of 10Gy in 5 fractions or 9.6 Gy in 4 fractions at the physician’s discretion.

Results: With this regimen, no patient experienced acute RTOG grade 3 or higher skin, or other toxicity. No treatment breaks were required due to toxicity. The most common side effects were grade 1 dermatitis, followed by grade 2 dermatitis with mild edema of the treated breast.

Conclusions: Our results suggest that postoperative hypofractionated radiation to the breast is well tolerated by women with DCIS and does not result in untoward acute toxicity.

Brain regional pharmacokinetics of p-aminosalicylic acid and its N-acetylated metabolite: effectiveness in chelating brain manganese

para-aminosalicylic acid (PAS; 4-amino-2-hydroxybenzoic acid), an antituberculosis drug in use since the 1950s, has recently been suggested to be an effective agent for treatment of manganese-induced parkinsonian disorders. However, the neuropharmacokinetics of PAS and its metabolite N-acetyl-para-aminosalicylic acid (AcPAS; N-acetyl-4-amino-2-hydroxybenzoic acid) are unknown. This study was designed to investigate the pharmacokinetics of PAS and its distribution in brain to help better design the dosing regimen for clinical trials. Male Sprague-Dawley rats received single femoral artery injections of PAS (200 mg/kg). Plasma, cerebrospinal fluid, and brain tissues were collected, and PAS and AcPAS concentrations were quantified by high-performance liquid chromatography. After administration, the concentrations of PAS declined rapidly in plasma with an elimination t(½) of 34 min; the metabolite AcPAS was detected in plasma and eliminated with a t(½) of 147 min. PAS and AcPAS were detected in brain tissues; AcPAS had a much higher tissue concentration and a longer t(½) than the parent PAS in most tissues examined. Although both were present in blood or tissues as free, unbound molecules, AcPAS appeared to have a higher tissue affinity than PAS. Taken together, our results suggest that a dosing regimen with continuous intravenous infusion of PAS is necessary to achieve therapeutic levels in targeted brain regions. Furthermore, PAS and AcPAS seem to be effective in reducing manganese levels in brain.

Dynamic heterogeneities, boson peak, and activation volume in glass-forming liquids

There are various arguments and models connecting the characteristic length associated with the boson peak vibrations ξ to the length scale of dynamical heterogeneity L(het). ξ is usually defined as the ratio of the transverse sound velocity to the boson peak frequency. Here we present pressure, temperature, and molecular weight dependencies of ξ, estimated using light scattering, in a few molecular and polymeric glass formers. These dependencies are compared with respective dependencies of the activation volume ΔV(#) in the same materials. Good agreement is found for the pressure and molecular weight dependencies of ξ and ΔV(#) measured at the glass transition temperature T(g). These results provide more evidence for a possible relationship between the sensitivity of structural relaxation to density (activation volume) and the heterogeneity volume. However, contrary to the expectations for L(het), ξ does not decrease with temperature above T(g) in most of the studied materials. The temperature dependence of ξ is compared to that of L(het) in glycerol and orthoterphenyl (OTP) estimated from literature data. The analysis shows a clear difference in the behavior of ξ(T) and ΔV(#)(T) at temperatures above T(g), although ΔV(#)(T)(1/3) and L(het)(T) have similar temperature dependence. Possible reasons for the observed difference are discussed.

The role of serum basic fibroblast growth factor, estradiol and urine basic fibroblast growth factor in differentiating infantile haemangiomas from vascular malformations

OBJECTIVE

To investigate the role of serum basic fibroblast growth factor (bFGF), estradiol (E2) and urine bFGF in differentiating infantile haemangiomas from vascular malformations.

METHOD

Between October 2007 and January 2009, 97 patients with haemangiomas and 25 patients with vascular malformations who had not been treated previously were included in this prospective study. Forty-eight patients with cleft lip and/or palate were selected as controls. The age of all subjects ranged from 1 to 30 months. The serum and urine levels of bFGF were determined by enzyme-linked immunosorbent assay (ELISA). The serum levels of E2 were examined via radioimmunoassay. All data were analysed with SPSS 11.5 software package.

RESULTS

The concentration of serum and urine bFGF was significantly different among the three groups (haemangiomas, vascular malformations and controls) (P = 0.027, P = 0.001). Significantly different urine bFGF levels were found in patients with proliferating and involuting haemangiomas (P = 0.04). The serum E2 levels were significantly higher in patients with haemangiomas than vascular malformations (P = 0.001) and controls (P = 0.001).

CONCLUSION

Serum bFGF and E2 as well as urine bFGF can be used to supplement the clinical diagnosis of congenital vascular anomalies. Urine bFGF combined with serum E2 may be the most potential markers for diagnosing haemangiomas and determining the proliferating stage of haemangiomas.

[The role of ADME evaluation in translation research of innovative drug]

New Chemical Entities (NCEs) development is a systematic long-term project that involves multiple disciplines. The translation research will help to build an advanced R&D system from the basic laboratory research, preclinical studies and clinical evaluation to clinical application of drug, for the purpose of shortening the R&D cycle and accelerate the launch of new drugs. In new drug R&D and its clinical application, drug disposition (absorption, distribution, metabolism, excretion, ADME) properties are important criteria for assessing drug-likeness of candidates. ADME evaluation of NCEs plays an important role in the translation research throughout innovative drug R&D process. Therefore, ADME evaluation at the early stage of drug design and development will be helpful to improve the success rate and reduce costs, and further access to safe, effective drugs.

HPLC analysis of para-aminosalicylic acid and its metabolite in plasma, cerebrospinal fluid and brain tissues

Para-aminosalicylic acid (PAS), an approved drug for treatment of tuberculosis, is a promising therapeutic agent for treatment of manganese (Mn)-induced parkinsonian syndromes. Lack of a quantifying method, however, has hindered the clinical evaluation of its efficacy and there upon new drug development. This study was aimed at developing a simple and effective method to quantify PAS and its major metabolite, N-acetyl-para-aminosalicylic acid (AcPAS), in plasma, cerebrospinal fluid (CSF) and tissues. Biological samples underwent one-step protein precipitation. The supernatant was fractionated on a reversed-phase C18 column with a gradient mobile system, followed by on-line fluorescence detection. The lower limits of quantification for both PAS and AcPAS were 50 ng/ml of plasma and 17 ng/g of tissues. The intra-day and inter-day precision values did not exceed 5% and 8%, respectively, in all three matrices. The method was used to quantify PAS and AcPAS in rat plasma and brain following a single iv injection of PAS. Data showed a greater amount of PAS than AcPAS in plasma, while a greater amount of AcPAS than PAS was found in brain tissues. The method has been proven to be sensitive, reproducible, and practically useful for laboratory and clinical investigations of PAS in treatment of Mn Parkinsonism.