Localization of glutamate in the human retina during early prenatal development

In this study we have localized glutamate (GLU) in fetal (14–25 weeks gestation, Wg) human retinas by immunohistochemistry. At 14 Wg, GLU-immunoreactivity (IR) was localized only in the central part of retina, showing a prominently labelled nerve fiber layero A few ganglion cells and displaced amacrine cells were very weakly labelled. At 17 Wg, GLU was localized conspicuously in many ganglion cells, displaced amacrine cells, some amacrine cells and the prospective photoreceptor cell bodies in the neuroepithelial layero With progressive development at 20 and 25 Wg, the IR for GLU was found additionally in the Müller cell endfeet, some bipolar cells as well as in the horizontal cells that were aligned in a row along the outer border of the inner nuclear layer of the central retinao The photoreceptor cell bodies in the outer nuclear layer were also prominently immunopositive for GLU. The developmental distribution of GLU in the human retina tends to indicate that it plays an important role in the differentiation and maturation of retinal neurons.     

Lymphocyte subpopulation state of the human lung during prenatal development]

Distribution of surface lymphocyte markers was assessed in foetus lung by cytofluorimetry using monoclonal antibodies produced by "Ortho Diagnostic systems" and "Becton Dickinson". Seven lymphocyte subpopulations were detected in developing lungs even at the pseudoglandular stage (8-15 weeks). There was a significant increase in these lymphocyte subpopulations in canalicular stage. Quantity of T3+ cells increased 8-fold and B-cells 10-fold. There was a tendency to increased number of cortical thymocytes (T6+), and to decreased ratio T6+/T3+ lymphocytes. The ratio of immunoregulatory lymphocyte subpopulations (T4+/T8+) resembled that of these subpopulations in adult human lung rather than in cord blood. In canalicular stage the share of lung lymphoid cells in S-phase was decreased.     

PTEN-mediated Akt activation in human neocortex during prenatal development

Akt is a crucial factor for cell survival and migration. Phosphatase and tensin (PTEN) negatively regulates cell growth and survival by inhibiting PI3K-dependent signaling. PTEN also blocks Akt phosphorylation, a main downstream molecule of PI3K cascade. So far, no studies have shown PTEN expression and Akt phosphorylation levels in the developing human neocortex. Our hypothesis is that spatial and temporal expression of PTEN is likely to modulate developing human brain cortical modeling by regulating Akt activation. Therefore, our aim is to analyze the expression pattern of PTEN and phospho-Akt levels using immunohistochemistry, Western blot, and semiquantitative analysis in the developing human neocortex (n=13 fetuses from first, second, and third trimesters). PTEN expression was decreased parallel to development, but some cells revealed strong nuclear immunoreactivity in the developing neocortex while the active Akt level was increased. Double immunohistochemistry was performed for proliferating cell nuclear antigen (PCNA)-Tuj1 (as neuronal marker) and PCNA-GFAP (Glial marker) to the subsequent sections of PTEN and Akt-stained slides. PCNA (+) cells were mostly positive for glial fibrillary acidic protein (GFAP) and correlated with active-Akt immunoreactivity. Our results suggest that Akt-mediated signaling plays an active role in cell migration, survival, and cerebral cortical modeling throughout prenatal life and that PTEN is the most likely protein to regulate this signaling.     

Distribution of N-cadherin in human cerebral cortex during prenatal development

An important subgroup of adhesion molecules is the superfamily of cadherins, which takes part in cell recognition and differentiation during development. To our knowledge only one study describing N-cadherin expression in developing human brain has been performed so far. Our aim is to identify N-cadherin expression to establish a relationship between its expression and function in human cerebral cortex during prenatal development. In the present study, localization and intensity of N-cadherin was investigated in developing cerebral cortex. Fetuses from spontaneous abortions (n=13) were obtained from first, second, and third trimesters. Western blot analysis revealed three bands and the third trimester samples showed the strongest bands for N-cadherin. Cell processes, axon bundles, and some of the developing neurons revealed immunoreactivity for N-cadherin throughout pregnancy. The immunoreactivity increased in the developing neocortex and expanded from the ventricular layer toward the marginal zone as development progressed. Moreover, the immunoreactivity was strong in vascular endothelium during all three trimesters. We conclude that N-cadherin is dynamically related to the organization of cerebral cortex layers during prenatal development. The dynamic expression pattern implicates N-cadherin as a potential regulator of cell migration, axon extension and fasciculation, the establishment of synaptic contacts, and neurovascular angiogenesis in the developing human cerebral cortex.     

Expression of different liver cell markers during the early prenatal human development

The expression of the liver cell markers, vimentin, desmin, cytokeratins 7, 18, 19, and stem cell markers CD34 and Bcl-2 in the early stages of the human prenatal development was studied. Desmin was revealed in sinusoidal liver cells between 3.5 and 12 weeks of gestation; in mesenchymal cells of ventral mesentery and hepatoblasts it was detected at the 4–7th weeks of gestation. During the hepatic period of hemopoiesis, desmin-positive sinusoidal cells were located close to blood cells. So-called “cholangio-” cytokeratins 7 and 19 displayed different expression patterns. Cytokeratin 7 was found only in cholangiocytes, and cytokeratin 19 in hepatoblasts until 15–16 weeks of prenatal development. Mesenchymal cells of the ventral mesentery expressed cytokeratins 18 and 19 more than hepatoblasts at the 4–7th weeks of gestation. Bcl-2 was seen in the same period in most sinusoidal and mesenchymal cells of the ventral mesentery. CD34 positive cells were detected in liver sinusoids between the 4th and 9th weeks of gestation but probably they are not progenitors of hepatocytes during embryonic development. Ventral mesentery mesenchyma was negative for CD34. These results let us hypothesize that hepatocytes and cholangiocytes may arise from different embryonic sources: cholangyocytes derive only from duodenal epithelial cells, while hepatoblasts develop most likely with the participation of mesenchymal cells.     

Time-dependent expression of cytochrome p450 epoxygenases during human prenatal development

There is growing evidence that some members of cytochrome P450 enzymes contribute to regulation of normal prenatal development. CYP epoxygenases (CYP2C and CYP2J subfamilies) convert arachidonic acid into four regioisomeric epoxyeicosatrienoic acids (EETs), biologically active molecules involved in mitogenesis and cell signaling. Almost nothing is known about localization of their expression in tissues during human prenatal development. The spatio-temporal expression pattern of CYP2C8, CYP2C9, CYP2C19 and CYP2J2 in human embryonic/fetal intestines, liver, and kidney was investigated by immunohistochemical method. CYP epoxygenases are expressed already in early stages of development in these embryonic/fetal tissues (as early as 7th week of IUD in the intestines, 5th week of IUD in the liver, and 6th week of IUD in the kidney). In kidney, CYP epoxygenases are expressed in the metanephrogenic blastema (but not in the uninduced mesenchyme) and in the tubular system. In the intestines, diverse CYP epoxygenases distribution along crypt-villus axis could suggest role in cell differentiation. Moreover, we detected higher CYP2J2 level in these organs than in adult tissue samples.     

Time-dependent expression of cytochrome p450 epoxygenases during human prenatal development

There is growing evidence that some members of cytochrome P450 enzymes contribute to regulation of normal prenatal development. CYP epoxygenases (CYP2C and CYP2J subfamilies) convert arachidonic acid into four regioisomeric epoxyeicosatrienoic acids (EETs), biologically active molecules involved in mitogenesis and cell signaling. Almost nothing is known about localization of their expression in tissues during human prenatal development. The spatio-temporal expression pattern of CYP2C8, CYP2C9, CYP2C19 and CYP2J2 in human embryonic/fetal intestines, liver, and kidney was investigated by immunohistochemical method. CYP epoxygenases are expressed already in early stages of development in these embryonic/fetal tissues (as early as 7th week of IUD in the intestines, 5th week of IUD in the liver, and 6th week of IUD in the kidney). In kidney, CYP epoxygenases are expressed in the metanephrogenic blastema (but not in the uninduced mesenchyme) and in the tubular system. In the intestines, diverse CYP epoxygenases distribution along crypt-villus axis could suggest role in cell differentiation. Moreover, we detected higher CYP2J2 level in these organs than in adult tissue samples.     

Finding of carotenoids in the vitreous body of human eye during prenatal development

Carotenoids were found for the first time in the vitreous body of human eye during the fetal period from week 15 until week 28. Their maximum content was timed to week 16–22. No carotenoids were found the vitreous body of 31-week fetuses, as well as adult humans, which corresponds to the published data. It was shown using HPLC that chromatographic characteristics of these carotenoids correspond to those of lutein and zeaxanthin, characteristic pigments of the retinal yellow macula.     

Changes of sulfated mucopolysaccharides and mucopolysaccharidases during fetal development

The changes of sulfated mucopolysaccharides and mucopolysaccharidases during bovine fetal development were analyzed. It is shown that chondroitin sulfate C increases in concentration up to the 50th day of fetal development and then decreases progressively until its complete disappearance in most adult tissues. Likewise, hyaluronidase also reaches a peak on the 50th day and decreases in activity until its disappearance in adult tissues. On the other hand, heparitin sulfate and chondroitin sulfate B as well as beta-glucuronidase and beta-N-acetylglucosaminidase remain without significant changes during the whole period. The fetal chondroitin sulfate C is tissue specific with different molecular weights depending on the tissue of origin. Some properties of fetal muscle and brain hyaluronidase are also described. The possible role of chondroitin sulfate C and hyaluronidase in the processes of differentiation and division is discussed in view of the present findings.     

Detection of carotenoids in the vitreous body of the human eye during prenatal development

Carotenoids were found for the first time in the vitreous body of human eye during the fetal period from week 15 until week 28. Their maximum content was timed to week 16-22. No carotenoids were found the vitreous body of 31-week fetuses, as well as adult humans, which corresponds to the published data. It was shown using HPLC that chromatographic characteristics of these carotenoids correspond to those of lutein and zeaxanthin, characteristic pigments of the retinal yellow macula.     

Expression of fucosyltransferases in skin, conjunctiva, and cornea during human development

During human development, type-1-precursor, sialyl-Le a, and Le x antigens were present in the periderm of skin and eye at week 6. The Le x antigen disappeared from cornea at 10 weeks and then from skin at 20 weeks. H-type-1, Le a, Le b, sialyl-Le a, H-type-2, sialyl-Le x, and Le y were found in cornea, conjunctiva, and periderm between 10 and 20 weeks. They disappear from the skin (at week 20) and progressively reappear in skin derivatives, especially in the epithelium of sweat glands. The secretory part of the sweat gland is type-1-precursor and H-type-1 positive while its excretory part is Le a, Le b, sialyl-Le a, and Le y positive. On the eye surface the disappearance of Le x at 10 weeks and of the H-type-1, sialyl-Le x, and Le y at week 35 starts in the central cornea in front of the lens. The corneal epithelium and the conjunctiva have similar antigens to those of excretory and secretory parts of the sweat gland, respectively. Invaginations and folding of the epidermis might preserve the embryonic staining. We propose that fucosylation patterns are associated with the embryonic origin and differentiation stage of tissue. The early and transient presence of Le x is associated with FUT4 or FUT9 activities, while the late appearance of Lewis antigens is related to other alpha3-fucosyltransferases.