Cadmium versus Lanthanum Effects on Spontaneous Electrical Activity and Expression of Connexin Isoforms Cx26, Cx36, and Cx45 in the Human Fetal Cortex.

Electrical activity is important for brain development. In brain slices, human subplate neurons exhibit spontaneous electrical activity that is highly sensitive to lanthanum. Based on the results of pharmacological experiments in human fetal tissue, we hypothesized that hemichannel-forming connexin (Cx) isoforms 26, 36, and 45 would be expressed on neurons in the subplate (SP) zone. RNA sequencing of dissected human cortical mantles at ages of 17-23 gestational weeks revealed that Cx45 has the highest expression, followed by Cx36 and Cx26. The levels of Cx and pannexin expression between male and female fetal cortices were not significantly different. Immunohistochemical analysis detected Cx45- and Cx26-expressing neurons in the upper segment of the SP zone. Cx45 was present on the cell bodies of human SP neurons, while Cx26 was found on both cell bodies and dendrites. Cx45, Cx36, and Cx26 were strongly expressed in the cortical plate, where newborn migrating neurons line up to form cortical layers. New information about the expression of 3 "neuronal" Cx isoforms in each cortical layer/zone (e.g., SP, cortical plate) and pharmacological data with cadmium and lanthanum may improve our understanding of the cellular mechanisms underlying neuronal development in human fetuses and potential vulnerabilities.

Neurogenic potential of hESC-derived human radial glia is amplified by human fetal cells.

The efficient production of human neocortical neurons from human embryonic stem cells (hESC) is the primary requirement for studying early stages of human cortical development. We used hESC to obtain radial glial cells (hESC-RG) and then compared them with RG cells isolated from human fetal forebrain. Fate of hESC-RG cells critically depends on intrinsic and extrinsic factors. The expression of Pax6 (intrinsic factor) has a similar neurogenic effect on hESC-RG differentiation as reported for human fetal RG cells. Factors from the microenvironment also play a significant role in determining hESC-RG cell fate. In contrast to control cultures, wherein hESC-RG generate mainly astroglia and far fewer neurons, in co-cultures with human fetal forebrain cells, the reverse was found to be true. This neurogenic effect was partly due to soluble factors from human fetal brain cultures. The detected shift towards neurogenesis has significance for developing future efficient neuro-differentiation protocols. Importantly, we established that hESC-RG cells are similar in many respects to human fetal RG cells, including their proliferative capacity, neurogenic potential, and ability to generate various cortical neuronal sub-types. Unlike fetal RG cells, the hESC-RG cells are readily available and can be standardized, features that have considerable practical advantages in research and clinics.

Evaluation of the fluidity and functionality of the renal cortical brush border membrane in experimental diabetes in rats.

The present study was aimed at addressing the effect of hyperglycemia on the renal cortical brush border membrane. The fluidity and the functionality of the renal cortical brush border membrane have been evaluated after 6 weeks of streptozotocin-induced diabetes in rats. Lipid peroxidation and protein oxidation were first performed to confirm a state of oxidative stress. The fluidity of the brush border membrane of diabetic rats decreased significantly by 15.76%. There was an increase in the amount of early (19.39%) and advanced (42.23%) glycation end-products suggesting the accumulation of significant amount of non-enzymic glycation products at 6 weeks of diabetes. Although, the activities of both gamma-glutamyl transpeptidase and alkaline phosphatase of the brush border membrane decreased, that of the latter decreased to a significant extent with an increase in K(m) (81%) and no change in the V(max). A study of the activities of glutathione-dependent antioxidant enzymes in the renal cortical homogenates showed that the activities of glutathione peroxidase and glyoxalase II were altered significantly. Our study seems to suggest that increased free radical generation accompanied by non-enzymic glycation may be responsible for oxidative stress and an increased rigidity of the diabetic brush border membrane. Alkaline phosphatase may thus serve as a potentially useful marker of free radical induced damage to the renal cortical brush border membrane. The results also suggest that enhanced susceptibility to oxidative stress during early stages may be an important factor in the development of secondary complications of diabetes.

Oxidative stress and gene expression of antioxidant enzymes in the renal cortex of streptozotocin-induced diabetic rats.

The present study was aimed at addressing the effect of hyperglycemia on antioxidant enzymes. The expression of catalase, superoxide dismutase and glutathione peroxidase, the three primary scavenger enzymes involved in detoxifying reactive oxygen species has been evaluated in the renal cortex of rats after 6 weeks of streptozotocin-induced diabetes. Lipid peroxidation and protein oxidation in the renal cortical homogenate were first performed to confirm a state of oxidative stress. The enzyme assays showed significant and varied alterations in catalase, superoxide dismutase and glutathione peroxidase activities. An opposing response of catalase and glutathione peroxidase activities to diabetes was observed. RT-PCR analysis was used to ascertain whether steady-state transcription levels were altered. While an increase in glutathione peroxidase and Cu-Zn superoxide dismutase mRNA parallels the increase in the activities of the enzymes, an increase in catalase gene expression in contrast to a decrease in enzyme activity suggests a role for post-translational modification in altering the activity of this enzyme.