Expression studies in gliomas and glial cells do not support a tumor suppressor role for LGI1

Disruptions of LGI1 in glioblastoma (GBM) cell lines and LGI1 mutations in families with autosomal dominant epilepsy imply a role for LGI1 in glial cells as well as in neurons. Although we and others could not find LGI1 mutations in malignant gliomas, our initial studies appeared to support the idea that LGI1 is poorly expressed or absent in these tumors. Microarray data suggested that LGI1 could be involved in the control of matrix metalloproteinases, and we found that tumors derived from U87 glioblastoma cells overexpressing LGI1 were less aggressive than U87 control tumors. To our surprise, we observed that LGI1 expression after differentiation of murine neural stem cells was robust in neurons but negligible in glial cells, in agreement with immunohistochemistry studies on rodent brain. This observation could suggest that the variable levels of LGI1 expression in gliomas reflect the presence of neurons entrapped within the tumor. To test this hypothesis, we investigated LGI1 expression in parallel with expression of the neuronal marker NEF3 by real-time PCR on 30 malignant gliomas. Results showed a strong, positive correlation between the expression levels of these two genes (P < 0.0001). Thus, our data confirm that LGI1 is involved in cell-matrix interactions but suggest that its expression is not relevant in glial cells, implying that its role as a tumor suppressor in gliomas should be reconsidered.

Correlation between semen parameters of electroejaculates and achieving pregnancy by intrauterine insemination

OBJECTIVE

To investigate whether any parameter in the routine semen analysis of electroejaculates is correlated with success in achieving pregnancy by IUI.

DESIGN

Retrospective observational study.

SETTING

An Assisted Reproductive Program at a tertiary care university center.

PATIENT(S)

Twenty-seven anejaculatory men with spinal cord injury (n = 24) or history of retroperitoneal lymph node dissection (n = 3), thirteen of whom attempted conception with their wives.

INTERVENTION(S)

Anejaculatory men underwent rectal probe electroejaculation and electroejaculates were used for IUI.

MAIN OUTCOME MEASURE(S)

Statistical correlation of semen parameters between electroejaculates that resulted in pregnancy and those that did not.

RESULT(S)

Seven pregnancies resulted from 56 IUIs using electroejaculates (pregnancy rate = 12.5% per IUI). The total motile sperm count and percentage of normal morphology were significantly higher in the specimens that resulted in pregnancies than those that did not. However, there was no statistically significant difference observed in pH, sperm concentration, or percentage of motility between the two groups. Swim-up techniques used to process electroejaculates significantly improved the motility of the specimens. No pregnancy occurred beyond the fifth IUI attempt. Repeated electroejaculation and duration of spinal cord injury had no effect on the quality of the ejaculates.

CONCLUSION(S)

The total motile sperm count and the percentage normal morphology of electroejaculates correlate with success in achieving pregnancy by IUI. Because repeated electroejaculation does not improve quality of ejaculate, the initial semen analysis of electroejaculates is not only useful in counseling couples undergoing such treatment program but should be planned for use as an inseminate.

Inhibition of H+ secretion in the turtle bladder by colchicine and vinblastine

In order to investigate a possible role of the microtubules in urinary acidification we measured H+ secretion by the turtle bladder in vitro before and after addition of either colchicine or vinblastine to the serosal phase. Both colchicine and vinblastine inhibited H+ secretion in a dose-dependent fashion; in the control hemibladders H+ secretion remained unchanged. The half-maximal inhibition of H+ secretion occurred at 5.2 x 10(-5) M for colchicine and 7.2 x 10(-6)M for vinblastine. The inhibitory effect of colchicine and vinblastine on H+ secretion was maximal at 10(-4)M and 5 x 10(-4)M, respectively. At these concentrations these compounds failed to alter SCC and resistance. The inhibition of H+ secretion by colchicine or vinblastine increased with time of exposure to the drugs. The effect of colchicine or vinblastine on H+ secretion was not reversible with removal of the drug or with addition of 5% CO2 in the serosal phase. Lumicolchicine, an isomer of colchicine devoid of capacity to interact with microtubules, failed to alter the rate of H+ secretion, suggesting that the observed effect of colchicine on H+ secretion was the result of disruption of microtubule function and not the consequence of nonspecific effect of the drug. These data provide evidence for a role of microtubules in urinary acidification by the turtle bladder in vitro, but an effect of these drugs on membrane-bound tubulin cannot be excluded.

On the mechanism of lithium-induced renal tubular acidosis: studies in the turtle bladder

The mechanism whereby lithium impairs urinary acidification was investigated in vitro with the bladder of the fresh water turtle. The effect of lithium was compared to that of choline or cesium. In the presence of 1% carbon dioxide, lithium (40 mM in the mucosa) failed to alter hydrogen ion secretion. Lithium also caused a significant decrease in sodium transport and in potential difference. Lithium failed to increase the passive loss of hydrogen ions from the mucosal solution, indicating that it does not affect the permeability of the mucosa to hydrogen ions. Bicarbonate secretion also was unchanged in lithium-treated hemibladders. Under open-circuit conditions, lithium caused a significant decrease in potential difference and, hence, caused a significant decrease in hydrogen ion secretion. Restoration of the potential difference, in the presence of lithium, to control levels caused a return of hydrogen ion secretion to the original value. These data demonstrate that in the turtle baldder lithium inhibits hydrogen ion secretion solely by reducing the potential difference and suggest that in vivo lithium causes an acidification defect not by directly inhibiting the hydrogen ion pump or causing a hydrogen ion backleak but by inhibiting sodium transport, thereby decreasing the favorable electric gradient for hydrogen ion secretion.

Effect of calcium and magnesium on transport processes by the turtle bladder

The role of the changes in intracellular concentration of Ca and Mg in Na and H+ transport by the turtle bladder in vitro was studied with the use of the ionophore A23187. This ionophore increases the permeability of living and artificial membranes to divalent cations. In the presence of a minimal concentration of Ca (0.2 mM), which is necessary for the membranes to remain stable, the ionophore failed to alter the rate of Na transport or H+ secretion in the presence of 2.5 mM Mg. These data demonstrate that changes in intracellular Mg do not play an important role in Na or H+ transport by the turtle bladder. In the presence of 1.8 mM Ca the ionophore caused a significant decrease in Na transport as compared to control hemibladders treated with dimethylsulfoxide, the vehicle used to dissolve the ionophore. In the presence of a minimal concentration of Ca (0.2 mM) the ionophore failed to alter the rate of Na transport. These observations demonstrate that the decrease in Na transport in the presence of Ca was the result of changes in intracellular Ca concentration rather than a non-specific effect of the ionophore. The data further demonostrate that calcium plays an important role in Na transport by the turtle bladder but that Mg does not seem to be important in the regulation of Na or H+ transport by this membrane.