Hitting the wall: Human sperm velocity recovery under ultra-confined conditions.

Infertility is a common medical condition encountered by health systems throughout the world. Despite the development of complex in vitro fertilization techniques, only one-third of these procedures are successful. New lab-on-a-chip systems that focus on spermatozoa selection require a better understanding of sperm behavior under ultra-confined conditions in order to improve outcomes. Experimental studies combined with models and simulations allow the evaluation of the efficiency of different lab-on-a-chip devices during the design process. In this work, we provide experimental evidence of the dynamics of sperm interacting with a lateral wall in a shallow chamber. We observe a decrease in average sperm velocity during initial wall interaction and partial recovery after the alignment of the trajectory of the cell. To describe this phenomenon, we propose a simple model for the sperm alignment process with a single free parameter. By incorporating experimental motility characterization into the model, we achieve an accurate description of the average velocity behavior of the sperm population close to walls. These results will contribute to the design of more efficient lab-on-a-chip devices for the treatment of human infertility.

Glucocorticoid and progesterone mechanisms in photoreceptor survival.

Death of retinal photoreceptors is the basis of prevalent blinding diseases. Since steroids might have a therapeutic role in retinal degenerations, we compared the protective effects of dexamethasone and progesterone on photoreceptor death induced by mifepristone and light exposure. Therefore, we studied the effective protection doses for each steroid in the two models. In addition, we analyzed changes in the levels of pro- and antiapoptotic molecules, glucocorticoid receptors α and ß (GRα and GRß), and rhodopsin under conditions of successful protection and photoreceptor survival. Mifepristone and light exposure selectively damaged photoreceptors. In light exposed retinas, photoreceptors mainly disappeared in the dorsotemporal region, while mifepristone produced a uniform damage. Dexamethasone and progesterone, at the same dose of 4 mg/kg/day for 2 days, preserved over 88% photoreceptor nuclei in both models. Assessment of cell death regulators showed that, in control retinas, both steroids activated BCL-XL, a prosurvival molecule, and decreased BID, a proapoptotic regulator. After steroid treatment of damaged retinas, BCL-XL, BCL2 and BAX showed characteristic patterns depending on the use of dexamethasone or progesterone on mifepristone or light exposed retinas. By contrast, BID decreased with any injury-steroid combination. Changes in GRα or GRß levels did not correlate with survival but were consistent with a mechanism of ligand induced downregulation of receptor expression. GRß might be upregulated by progesterone. Both dexamethasone and progesterone increased retinal rhodopsin stores, suggesting a link between photoreceptor protection and transduction pathways. Results show that dexamethasone and progesterone induced comparable but not identical protection responses in each model.

Islet cannabinoid receptors: cellular distribution and biological function.

OBJECTIVES: This study aimed to determine the cellular distribution of islet cannabinoid receptors (CBs) and their involvement in the development of metabolic and hormonal changes in rats fed a fructose-rich diet (F). METHODS: In normal rat islets, we determined CBs (immunofluorescence and retrotranscription-polymerase chain reaction) and glucose-stimulated insulin secretion (GSIS) of isolated islets incubated with the CB1 antagonist rimonabant (R) and/or different CBs agonists. In 3-week F-fed rats, we determined the in vivo effect of R on serum glucose, triglyceride, and insulin levels; homeostasis model assessment for insulin resistance, GSIS, and CBs and insulin receptor substrate gene expression levels (real-time polymerase chain reaction). RESULTS: Cannabinoid receptors appeared exclusively in islet α cells. Whereas different CB agonists enhanced GSIS in normal rat islets, R did not affect it. F rats had higher serum triglyceride and insulin levels and homeostasis model assessment for insulin resistance than control rats; these alterations were prevented by R coadministration. Although R did not correct the increased GSIS observed in F islets, it modulated CBs and insulin receptor substrate gene expression. CONCLUSIONS: Islet CBs would exert an important modulatory role in metabolic homeostasis. Administration of R and F affected islet CB expression and prevented the development of F-induced metabolic impairment. Selective islet CB1 blockers could be useful to prevent/treat the alterations induced by the intake of unbalanced/unhealthy diets.

Mifepristone, a blocker of glucocorticoid receptors, promotes photoreceptor death.

PURPOSE: Glucocorticoids are best known by their protective effect on retinal photoreceptor damage. However, they could also be involved in photoreceptor homeostasis under basal, nonstressful conditions. Therefore, we aimed to study glucocorticoid-induced changes of survival-related molecules in male mice retinas under standard illumination conditions (12 hours light, ≤ 60 lux/12 h dark). METHODS: Male Balb-c mice were injected with dexamethasone (DEX), a selective glucocorticoid receptor α (GRα) agonist, its antagonist mifepristone (MFP), or both drugs (D+M) at noon. A group of mice was subjected to surgical adrenalectomy (AdrX). Retinas were studied by histology, immunohistochemistry, TUNEL procedure, and Western blotting at different periods after pharmacological or surgical intervention (6 hours, 48 hours, or 7 days). RESULTS: The antiapoptotic molecule Bcl-X(L) significantly increased 6 hours after DEX injection. By contrast, this molecule could no longer be found after MFP injection. At the same time, high levels of cleaved caspase-3 (CC-3) and Bax appeared in retinal extracts, and TUNEL(+) nuclei selectively showed in the outer nuclear layer (ONL). After MFP, retinal extracts also contained phosphorylated histone H2AX (p-H2AX), a marker of DNA breakage and repair. Loss of ONL nuclear rows and decrease of rhodopsin levels were evident 7 days after MFP administration. These changes were minimized when DEX was given together with MFP (D+M). In the absence of MFP, DEX increased Bcl-X(L) in every retinal layer, with a marked intensification in photoreceptor inner segments. Numerous TUNEL(+) nuclei rapidly appeared in the ONL after AdrX. CONCLUSIONS: A single dose of MFP induced selective photoreceptor damage in the absence of other environmental stressors. Because damage was prevented by DEX, and was reproduced by AdrX, our findings suggest that glucocorticoids play a critical role in photoreceptor survival.

Endothelinergic signaling during recovery of brain cortical lesions.

OBJECTIVES: Recovery of brain lesions has been associated with increased activation and migration of endogenous neural stem cells, glia, and endothelium. To understand the role of endothelinergic signaling in these phenomena we studied devascularizing lesions of mouse brain cortex. Our specific aims were to: (i) describe the endothelinergic cell phenotypes appearing within the lesions; and (ii) evaluate the effect of endothelinergic blockade on the injured cortex. METHODS: C57BL/6 mice were anesthetized and submitted to devascularization lesions of the right M1 cortical area. A group of mice was daily treated with tezosentan, a dual endothelinergic receptor blocker. Mice were euthanatized 5 days after surgery and the injured area was studied with immunohistochemistry for endothelin, endothelin receptor B, glial fibrillary acidic protein, prominin-1, nestin, and phospho-histone H3. RESULTS: The injured cortex exhibited a large increase of multipolar endothelin(+), endothelin receptor B(+), glial fibrillary acidic protein(+), prominin-1(+), and nestin(+) cells. These markers appeared in different combinations. Tezosentan treatment reduced the perilesional expression of glial fibrillary acidic protein and decreased the number of proliferating cell nuclei displaying phospho-histone H3. DISCUSSION: Our observations suggest that endothelinergic cells surrounding the lesion belong to a mixed population including reactive glia and neural progenitor cells. Findings in tezosentan-treated mice probably reflect a decrease of reactive gliosis with a still unknown effect on neural progenitor cells.

Endothelinergic cells in the subependymal region of mice.

Endothelin (ET) is a small peptide that activates astrocyte proliferation, regulates proliferation and migration of embryonic neural precursor cells and stimulates glioblastoma growth. We found that in mouse brain, ET and its receptor B (ETRB) were highly expressed in the subependymal zone (SEZ), an adult neurogenic niche. Cells with ET immunoreactivity (ET+ cells) selectively appeared along the lateral and dorsal walls of the lateral ventricle. They also appeared in the cingular region of the corpus callosum. Subependymal ET+ cells also displayed prominin (PRO), glial fibrillary acidic protein (GFAP) and ETRB immunoreactivities. ET+ processes traversed the ependymal epithelium and approached the ventricular lumen. Ependymal cells only showed ETRB-ir. A small but consistent number of ET+ cells displayed proliferation markers: 5-bromo-2'-deoxyuridine (BrdU) incorporation, and minichromosome maintenance protein 2 (Mcm2). Cortical injury and G-CSF increased subependymal endothelinergic cells and their proliferation markers. Our findings suggest that ET and ETRB might be associated with regulation of adult neural stem cells and their migration through neurogenic and gliogenic pathways.