Morpho-functional and transcriptional response of zebrafish retinal cells to cadmium stress.

Ocular malformations are observed in embryos and adults of aquatic species after exposure to toxicants. In this study, cadmium, a chemical stressor, was used to determine the toxic effects on the retinal development and visual ability of adult zebrafish (Danio rerio). Our results demonstrated that Cd-exposure (100 μM)from sphere (4 hpf) to gastrula stage (8hpf) led to the up-regulation of the expression of lambda1-crystallin and Retinoblastoma Binding Protein 6 transcripts in embryos. Cryl1 is a lens protein that acts as a molecular chaperone; Rbbp6 is a protein regulating cellular proliferation. In situ hybridization demonstrated that Cd induced the up-regulation of these genes also in adult retina, in the inner and outer nuclear layers. The Cd-induced over-expression was dose-dependent and reversible. Interestingly, metallothionein, the cysteine-rich, low molecular mass metal-binding protein considered a key molecule involved in cellular protection against toxic metals, did not seem to be up-regulated. Adult retinal morpho-cytological alterations were investigated by light and electron microscopy, while the functionality of Cd-exposed retina was assessed by re-illumination behavioral tests. After Cd-treatment, dose-dependent alterations were clearly observed. The nerve fiber layer was clearly thickened and vacuolated, several ganglion cells had compact pycnotic nuclei. Changes occurred in the thickness of the pigmented epithelium and at the level of the cones inner segments. TEM observations oCd-treated retina showed ganglion cells with highly vacuolated cytoplasm and cells with ultrastructural apoptotic features. Apoptotic cells were also evident in the inner nuclear and in the photoreceptor layers. Many polymorphic Müller cells were observed both in inner and outer nuclear layers. Behavioral tests demonstrated that re-illumination with white or colored light induced a significant escape response after Cd-treatment, not observed in untreated animals. All together, data demonstrated that Cd toxicity caused: 1) dysregulation of gene expression; 2) degeneration and loss of organization at both macro and microscopic levels; 3) impairment of the functional response, particularly through increased light sensitivity. The increased amount of Müller cells with irregular shape suggested that the recovery of visual acuity is due to a regenerative process involving these retinal macroglial cells, that are able to dedifferentiate and function as neural stem cells

Cardiac function, phisical exercise capacity and quality of life during long-term thyrotropin-suppressive therapy with levotyroxine: effect of individual dose tailoring

As recently claimed, TSH-suppressive therapy with L-T4 may have adverse effects on the heart, but these results have not been consistently confirmed. We assessed cardiac function by clinical, echocardiographic, and ergometabolic criteria in 19 patients (16 women and 3 men) receiving long term L-T4 at a fixed daily dose ranging from 1.8-4.0 microg/kg. The results showed significant alterations in several cardiac parameters suggestive of subclinical hyperthyroidism. In particular, intraventricular septum thickness (10.0+/-1.4 vs. 8.1+/-1.1 mm), left ventricular posterior wall thickness (9.4 1.5 vs. 8.1+/-1.1 mm), end-diastolic dimension (47+/-4 vs. 44+/-3 mm), and left ventricular mass index (102+/-15 vs. 75+/-15 g/m2) were significantly increased compared to values in age- and sex-matched euthyroid controls. Exercise tolerance (expressed as maximal tolerated workload; 102+/-14 vs. 117+/-12 watts), maximal VO2 achieved at peak exercise (maximum VO2, 17.3+/-3.3 vs. 21.9+/-2.5 mL/min x kg), and anaerobic threshold (expressed as a percentage of VO2max, 46.5+/-8.4 vs. 56.2+/-6.6) were significantly reduced in L-T4-treated patients. The L-T4 dose was then reduced to the minimal amount able to keep the serum TSH concentration at 0.1 mU/L or less in 7 patients who were reevaluated 6 months after the initial study. This individual tailoring of the TSH-suppressive L-T4 dose was in all cases associated with normalization of all echocardiographic and ergometabolic parameters. In conclusion, our findings show that abnormalities of heart morphology associated with impaired exercise performance occur as a consequence of long term therapy with fixed TSH-suppressive doses of L-T4, but that these abnormalities improve or disappear after careful tailoring of TSH-suppressive therapy

Effects of transdermal estrogen administration on peripheral vascular responsiveness in menopausal women

This study was designed to evaluate the peripheral vascular responses to acute estrogen replacement. According to a cross-over, double-blind study design, we randomized nine healthy postmenopausal women (time lapse from menopause to >1 year; mean age±SD 45.4±11.7 years) to treatment with transdermal patches of estradiol-17beta or matched placebo. The estrogen patch was rated to assure a plasma concentration of substance of more than 100 pg/ml after 8–10 hours of treatment. Forearm blood flow (ml/100 ml/minute), local vascular resistance (mmHg/ml/100 ml/minute), venous volume (ml/100 ml), and venous compliance (ml/100 ml/mmHg) were measured in supine resting subjects by the straingauge venous occlusion plethysmography. Plasma concentration of norepinephrine (pg/ml) was quantified by HPLC-ED. Estradiol-17beta produced increase in forearm blood flow and decrease in local vascular resistance. The drug reduced circulating norepinephrine concentrations. There were no significant changes in mean arterial pressure or heart rate. Venous volume and venous compliance were both enhanced by estrogen administration. The peripheral circulatory changes are attributed to a direct activity of estradiol-17beta on arterial and venous wall and may in part reflect a modulation of estrogen on peripheral sympathetic tone