Midtrimester Human Fetus Research Articles

Formation of atubular glomeruli in the developing kidney following chronic urinary tract obstruction

Congenital urinary tract obstruction is a major cause of progressive renal disease in children. We developed a model of partial unilateral ureteral obstruction (UUO) in the neonatal mouse, in which nephrogenesis at birth is similar to that of the midtrimester human fetus. The proximal tubule responds to UUO by undergoing apoptosis and necrosis, likely due to mitochondrial sensitivity to hypoxia and reactive oxygen species in the face of reduced endogenous antiapoptotic factors such as eNOS. Damage to the glomerulotubular junction is followed by scission and formation of atubular glomeruli and aglomerular tubules. This is an orchestrated process, with atubular glomeruli surrounded by a continuous layer of regenerated parietal epithelial cells. Relief of UUO at 7 days of age results in remodeling of the renal parenchyma by adulthood. In contrast to proximal tubular destruction, collecting ducts remain dilated and patent, with remodeling due to apoptosis and proliferation (a process associated with recruitment of intercalated cells as progenitor cells following UUO in the fetal monkey). Formation of atubular glomeruli occurs in other renal disorders (congenital nephrotic syndrome and cystinosis), and may represent a maladaptive response to proximal tubular injury reflecting an evolutionary adaptation by an ancestor we share with aglomerular marine fish.

Erythropoietin and hypoxia inducible factor-1 expression in the midtrimester human fetus

Erythropoietin and hypoxia inducible factor-1 expression in the midtrimester human fetus

UNILATERAL URETERAL OBSTRUCTION IN EARLY DEVELOPMENT ALTERS RENAL GROWTH: DEPENDENCE ON THE DURATION OF OBSTRUCTION

Purpose Over 90% of nephrogenesis in the rat takes place postnatally in the first 10 days, analogous to the midtrimester human fetus. We wished to determine the relationship between the duration of unilateral ureteral obstruction and growth and morphology of both kidneys following relief of the obstruction in the neonatal rat. Materials and Methods One ureter of 1 day-old rats was sham-operated or occluded and released 1, 2, 3, or 5 days later, or not released. Fourteen or 28 days later, renal mass, tubular atrophy, and interstitial fibrosis were determined in the obstructed and contralateral kidney of each group. Results At 28 days, there was a linear relationship between kidney/body weight ratio and duration of obstruction, such that the decrement in renal mass resulting from ipsilateral obstruction was precisely compensated by an equal increment in the mass of the contralateral kidney (both, p <0.0001). Tubular atrophy was increased 100-fold in kidneys of rats with 28 days continuous ipsilateral obstruction, while relief of obstruction after 2 to 5 days reduced tubular atrophy by 90% (p <0.01). Interstitial fibrosis was also markedly reduced by relief of obstruction, with the severity of fibrosis being proportional to the duration of obstruction. Conclusions We conclude that ureteral obstruction during the critical period of nephrogenesis impairs growth of the obstructed kidney and stimulates growth of the contralateral kidney in direct proportion to the duration of obstruction. Moreover, counterbalance between the two kidneys is finely regulated. Even 2 days of ureteral obstruction (with subsequent relief) induces contralateral renal growth, and induces ipsilateral tubular atrophy. However, the time dependence of renal injury on duration of obstruction suggests that earlier relief of obstruction in the developing kidney may allow greater ultimate preservation of functional renal mass.

Gonadotropin-releasing hormone immunoreactivity in the nasal epithelia of adults with Kallmann's syndrome and isolated hypogonadotropic hypogonadism and in the early midtrimester human fetus.

GnRH-secreting neurons are known to originate in the epithelium of the medial olfactory placode, whence they migrate along the axons of the terminal nerve via the forebrain and into the hypothalamus. Synaptic contact between the developing olfactory bulbs and fascicles of the vomeronasal, terminal, and olfactory nerves does not occur in Kallmann's syndrome. Consequently, there is migration arrest of GnRH cells and partial or complete failure of formation of the olfactory bulbs, resulting in severe olfactory deficit and hypogonadotropic hypogonadism. In the present study, using an immunofluorescent, double immunostaining technique and confocal laser scanning microscopy, we observed GnRH-immunoreactive neurons in the hypothalamus of a 14-week-old human fetus. However, migration of GnRH neurons was not complete, and indeed, such cells were seen to be migrating along terminal nerve fascicles beneath the cribriform plate in a 16-week-old fetus. The same immunofluorescent technique demonstrated the presence of GnRH cells in biopsies of nasal mucosa obtained from three adults with Kallmann's syndrome, one normosmic subject with hypogonadotropic hypogonadism, and a eugonadal male cadaver. These findings are consistent with two different interpretations: the nasal GnRH neurons may be vestigial, representing cells that failed to migrate during embryogenesis; alternatively, they may have been generated de novo later in life, a possibility consistent with the recognized plasticity of human postnatal olfactory neuroepithelium. They also reveal that subjects with the normosmic (i.e. non-Kallmann's) form of GnRH deficiency are able to synthesize immunologically recognizable GnRH, implying that failure of GnRH synthesis is not responsible for this type of hypogonadotropic hypogonadism.

Gonadotropin-Releasing Hormone Immunoreactivity in the Nasal Epithelia of Adults with Kallmann's Syndrome and Isolated Hypogonadotropic Hypogonadism and in the Early Midtrimester Human Fetus

Gonadotropin-Releasing Hormone Immunoreactivity in the Nasal Epithelia of Adults with Kallmann's Syndrome and Isolated Hypogonadotropic Hypogonadism and in the Early Midtrimester Human Fetus

Erythropoietin receptors are expressed in the central nervous system of mid-trimester human fetuses.

Recombinant erythropoietin (rEpo) is an effective treatment for infants with the anemia of prematurity. rEpo was previously thought to act only on erythroid progenitor cells, but evidence now indicates that certain nonerythroid cells also express functional erythropoietin receptors (Epo-R). Such receptors have been observed on cells in the developing murine brain and spinal cord. The objective of this study was to determine whether Epo-R are expressed in the CNS of mid-trimester human fetuses. For this study, spinal cords were collected from five mid-trimester abortuses. RNA was extracted from the washed specimens, and the presence of Epo-R mRNA was sought by reverse transcription followed by polymerase chain reaction. Immunohistochemistry was then used to determine the anatomic location of the cells expressing Epo-R within the fetal spinal cord. The results showed that all fetal spinal cords tested contained Epo-R mRNA. The cells expressing Epo-R were radiating from the ependymal canal toward the anterior and posterior median sulci. We conclude that Epo-R are expressed on cells in the developing human CNS. Further studies are needed to determine whether they are clinically relevant in the premature infant.

ERYTHROPOIETIN AND ITS RECEPTOR ARE EXPRESSED IN THE CENTRAL NERVOUS SYSTEM OF FIRST AND SECOND TRIMESTER HUMAN FETUSES. † 1301

Recombinant erythropoietin (rEpo) is an effective treatment for infants with anemia of prematurity, and is used increasingly as an alternative to multiple transfusions. The primary known function of Epo is to promote erythropoiesis by stimulating the proliferation and differentiation of erythroid progenitor cells, however, animal studies have demonstrated the presence of Epo and its receptor (Epo-R) within the developing murine central nervous system. Our objective was to determine whether mRNA for Epo and Epo-R are expressed in the central nervous system of early and mid-trimester human fetuses. Spinal cords (n=12) and brain (n=6) were collected from human abortuses ranging in maturity from 5 weeks to 24 weeks gestation. Meninges were removed from spinal cords, and total RNA was extracted from washed specimens. The presence of Epo and Epo-R mRNA was determined by reverse transcription followed by polymerase chain reaction using primers designed to differentiate between genomic DNA and mRNA amplification. All fetal spinal cords and brain tested contained Epo-R mRNA. Immunofluorescent staining of spinal cord identified cells expressing Epo-R to be radiating from the ependymal canal toward the anterior and posterior median sulci. Expression of Epo mRNA was also present in both spinal cord and brain samples ranging in age from 5 to 24 weeks gestation. We conclude that Epo and its receptor are expressed in cells of the developing human central nervous system. As the role of Epo within the developing central nervous system is unclear, further studies are needed to determine the long-term neurodevelopmental effects of therapeutic rEpo administered to preterm infants.

Distribution of fibroblast growth factor (FGF)-2 and FGF receptor-1 messenger RNA expression and protein presence in the mid-trimester human fetus.

Fibroblast growth factors (FGF) are known to have key roles in embryonic growth and morphogenesis, but their presence and contributions to fetal development are unclear. In particular, little information exists as to the relevance of FGF and their specific receptors to human fetal development. We studied the anatomical distribution of messenger RNA encoding FGF-2 and one of its high affinity receptors, FGFR1, using in situ hybridization in a variety of human fetal tissues in early second trimester. Corresponding protein distributions were determined by immunohistochemistry. Both FGF-2 and FGFR1 mRNA and proteins were found to be present in every organ and tissue examined, but with defined cellular localizations. In skeletal muscle, both FGF-2 and FGFR1 mRNA and peptides were present in differentiated fibers, and both co-localized to proliferating chondrocytes of the epiphyseal growth plate. FGF-2 and FGFR1 mRNA and peptides were also present within cardiac or gastrointestinal smooth muscle. Within the gastrointestinal tract FGF-2 mRNA and peptide were located in the submucosal tissue, whereas FGFR1 was expressed within the overlying mucosa. Similarly, in skin, FGF-2 was expressed within the dermis whereas FGFR1 mRNA and peptide were most apparent in the stratum germinativum of the epidermis. In kidney and lung, FGFR1 mRNA was located in the tubular and alveolar epithelia respectively, whereas FGF-2 was expressed in both epithelial and mesenchymal cell populations. Both growth factor and receptor were widespread in both neuroblasts and glioblasts in the cerebral cortex of the brain. Immunoreactivity for FGF-2 and FGFR1 was seen in all vascular endothelial cells of major vessels and capillaries. Within the skin, kidney, lung, and intestine FGF-2 immunoreactivity was found in basement membranes underlying epithelia, and was associated with the extracellular matrix and plasma membranes of many cell types. The results show that FGF-2 and one of its receptors are widely expressed anatomically in the mid-trimester human fetus.

Immunohistochemical localization of epidermal growth factor in the second-trimester human fetus.

Epidermal growth factor (EGF) is considered to be important in mammalian neonatal growth and development. In order to clarify its developmental role, we have investigated, by immunohistochemistry, the localization of EGF and the time of its first appearance in various organs from a series of 25 midtrimester human fetuses with a gestational age ranging from 13 to 22 weeks. The first detectable EGF immunoreactivity occurred in week 15-16 fetuses in the placenta, the skin, the distal tubules of the kidney, the surface epithelium of the stomach, and the tips of the small intestinal villi, as well as in a few Paneth cells. Glandular structures, such as the glands of the cardia and the pyloric part of the stomach, Brunner's glands of the duodenum, the pancreas, and the submucous glands of the trachea, showed positive EGF immunoreactivity later (week 17). Thus, apart from the kidney, staining of the surface epithelia seems to precede staining of the EGF-producing glandular structures and EGF is not present in the glands before these have already differentiated.

Neutrophil Pool Sizes and Granulocyte Colony-Stimulating Factor Production in Human Mid-Trimester Fetuses

We quantified neutrophils and neutrophil progenitors, and assessed granulocyte colony-stimulating factor (G-CSF) production in the liver and bone marrow of 20 human abortuses after elective pregnancy termination between 14 and 24 wk of gestation. Mature neutrophils were not observed in any of the liver specimens, but were present in the bone marrow as early as 14 wk. The concentrations of neutrophils in the fetal marrow were extremely low, by comparison with term infants and adults, with less than 5% of the nucleated cells being segmented neutrophils, band neutrophils, or metamyelocytes compared with 31-69% in term infants. Despite the low neutrophil populations, progenitors which had the capacity for clonal maturation into neutrophils in vitro were abundant in the fetal liver and fetal bone marrow. In addition, such progenitors had a dose-response relationship to recombinant G-CSF similar to that of progenitors from the bone marrow of healthy adults. At each gestational age tested, stimulation of mononuclear cells from fetal liver with IL-1 alpha generated less G-CSF protein and fewer G-CSF mRNA transcripts than did stimulation of mononuclear cells from fetal bone marrow. Mononuclear cells from the fetal bone marrow produced less G-CSF protein and mRNA than did mononuclear cells from the blood of adults. Thus, the liver of the mid-trimester human fetus is almost devoid of neutrophils, and the bone marrow contains a significantly lower proportion of neutrophils than does the marrow of term neonates or adults. These findings correlate with IL-1 alpha-induced production of G-CSF in these organs.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative assessment of the stage of neuronal maturation in the developing human fetal gut—A new dimension in the pathogenesis of developmental anomalies of the myenteric plexus

There are two main theories of the normal development of the enteric nervous system: the classical theory suggests that the enteric neuroblasts migrate along the alimentary tract in a single cranio-caudal direction. However, the second theory postulates a dual gradient of neuronal development. The present study aims to support the second theory and contribute to the understanding of the pathogenesis of Hirschsprung's disease and its allied gut motility disorders. Using a histomorphometric method, quantitative estimation of the myenteric intraganglionic neuronal development was made in tissues from various selected levels of the gut in 32 normal human fetuses of 11 to 24 weeks ovulation age. A parallel study with special chromatin staining was carried out from these materials to investigate different neurons in the myenteric plexus. Development of intraganglionic neurons was shown to be more advanced in the esophagus, less so in the rectosigmoid and least so in the ileocecal region: the mean values of neuronal and nuclear volume were found in the esophagus greater than in rectosigmoid and ileocecal region as ovulation age progressed. Intraganglionic mitotic figures were detected at all the selected levels of the gut. A decrease of the mitosis index as age progressed was observed. We showed that myenteric neurons followed a dual gradient of development proceeding from both ends to the middle of the gut in mid-trimester human fetuses. Our findings are compatible with the suggestion that any alterations in the fetal gut microenvironment may affect seriously the normal development of a multipotential precursor cell population resulting in various congenital anomalies of the myenteric plexus.

Relationship between maternal and fetal corticotrophin-releasing hormone-41 and ACTH levels in human mid-trimester pregnancy

Samples of maternal blood, amniotic fluid and umbilical arterial and venous blood were collected from 11 women at 16-24 weeks of pregnancy. Corticotrophin-releasing hormone-41 (CRH-41) and ACTH were measured by immunoradiometric assay. The mean levels of ACTH were 11 pmol/l in maternal plasma, 12 pmol/l in fetal plasma and 9.7 pmol/l in amniotic fluid. The mean levels of CRH-41 were 1.6 pmol/l in maternal plasma and 0.7 pmol/l in fetal plasma. There was a positive correlation between maternal and fetal plasma CRH-41 and between maternal CRH-41 and ACTH. In fetal plasma there was a weak inverse correlation between CRH-41 and ACTH. This is the first demonstration of CRH-41 in the circulation of the mid-trimester human fetus, but on the basis of the present findings it is not possible to specify the exact source (fetal, placental or maternal).

Development profile of neuron-specific enolase in human gut and its implications in Hirschsprung's disease

The most widely held view on the pathogenesis of Hirschsprung's disease as an arrest of neuroblast migration in the gut was based on the hypothesis of a single craniocaudal gradient of development of enteric neurons. Recent experimental studies in animals, however, have revived a contradictory hypothesis of a dual gradient of neuronal development; such data are not available in humans. To test these hypotheses in humans, we studied the pylorus, ileum, and colon of 28 fetuses with gestational ages of 9–21 wk, using immunohistochemical localization of neuron-specific enolase, a specific neuronal marker indicative of differentiation. Development of the enteric nervous system was shown to be most advanced in the pylorus, less so in the colon, and least so in the ileum. The findings support the hypothesis of a dual gradient of neuronal development proceeding from both ends to the middle of the gut in midtrimester human fetuses and suggest that the pathogenesis of Hirschsprung's disease needs to be reconsidered.

Plasma amino acids of the mid-trimester human fetus.

The amino acid concentrations in umbilical cord plasma taken at fetoscopy were measured from 12 fetuses between 18 and 29 weeks gestation. Concurrent maternal plasma levels were measured. Fetal plasma showed consistently higher concentrations of plasma amino acids with the ratios varying between 1.1:1 and 3:1 and the difference always reached statistical significance. It is suggested that these results reflect the in vivo situation of the mid-trimester human fetus.

Development of Pluripotent Hematopoietic Progenitor Cells in the Human Fetus

Pluripotent hematopoietic progenitor cells (CFU-GEMM), myeloid progenitor cells (CFU-GM), and erythroid progenitors (BFU-E) were studied in midtrimester human fetuses using the mixed colony assay. All three progenitor cell populations were detected at high levels in the fetal liver from 12 to 23 wk of gestation. Stem cells were first observed in the bone marrow at 15-16 wk of gestation, although bone marrow cultures from earlier fetuses showed heavy growths of stromal cells. Spleen cultures first showed growth of stem cells at 18-19 wk, but fetal thymus showed no hematopoietic activity. Peripheral blood from four fetuses aged 13, 18, 20, and 21 wk showed very high levels of all 3 progenitor cells. The results demonstrate that hematopoietic development in the human fetus parallels that of the mouse. The observation that stromal cell development in the bone marrow precedes the appearance of hematopoietic progenitor cells suggests that they may be closely involved in stem cell growth.

Development of pluripotent hematopoietic progenitor cells in the human fetus

Pluripotent hematopoietic progenitor cells (CFU-GEMM), myeloid progenitor cells (CFU-GM), and erythroid progenitors (BFU-E) were studied in midtrimester human fetuses using the mixed colony assay. All three progenitor cell populations were detected at high levels in the fetal liver from 12 to 23 wk of gestation. Stem cells were first observed in the bone marrow at 15–16 wk of gestation, although bone marrow cultures from earlier fetuses showed heavy growths of stromal cells. Spleen cultures first showed growth of stem cells at 18–19 wk, but fetal thymus showed no hematopoietic activity. Peripheral blood from four fetuses aged 13, 18, 20, and 21 wk showed very high levels of all 3 progenitor cells. The results demonstrate that hematopoietic development in the human fetus parallels that of the mouse. The observation that stromal cell development in the bone marrow precedes the appearance of hematopoietic progenitor cells suggests that they may be closely involved in stem cell growth.

Oxytocin, vasopressin and neurophysins in the hypothalamo-neurohypophysial system of the human fetus.

The content of vasopressin, oxytocin and their related neurophysins was measured in the hypothalamus and pituitary gland of mid-trimester human fetuses. Vasopressin was present in both tissues approximately 3-4 weeks before oxytocin. The levels of the hormones in the pituitary gland increased 1000-fold over the next 3-4 months. During this time, the very high vasopressin/oxytocin ratio gradually deceased but did not reach unity in the period studied. In contrast, both the vasopressin-associated neurophysin and the oxytocin-associated neurophysin appeared in the pituitary gland at the same gestational age and showed the same exponential increase with fetal age. Lower levels of the neurophysins and the nonapeptides were found in the hypothalamus and the levels increased more slowly with fetal age. Our results suggest that the high vasopressin/oxytocin ratios observed in fetal life are due to differences in the rate of maturation of the hormone precursor, rather than to differences in the rate of de-novo synthesis.

Isozyme patterns in erythrocytes from human fetuses

Starch gel electrophoretic patterns of 26 enzymes (corresponding to 36 gene loci) were examined in hemolysates of erythrocytes from 11 first-trimester and mid-trimester human fetuses (65-138 gestation days). The zymograms of 16 enzymes were identical in fetal and control adult red cells. Six enzymes (enolase, guanylate kinase, lactate dehydrogenase, nucleoside phosphorylase, phosphofructokinase, hexokinase) showed differences in the staining intensity of certain isozyme zones as compared with the controls. Also, the fetal red cell zymograms, in contrast to those of adults, contained the mitochondrial forms of isocitric dehydrogenase and glutamic oxaloacetic transaminase as well as more definite zones of phosphoglucomutase-3. Finally, some of the isozymes of uridine diphosphate kinase in the fetal cells had slightly retarded mobility. These observed differences between fetal and adult red cells could reflect the expression of a different program of protein synthesis in red cells of the fetuses or the epigenetic modifications of isozymes in immature red cells.

Conversion of pregnenolone and pregnenolone sulfate to other steroid sulfates by the human fetus perfused at midgestation.

ABSTRACT Two previable human fetuses (16th and 19th weeks of gestation) were perfused in situ with a combination of 4-14C-pregnenolone and 3H-pregnenolone sulfate. Approximately 70% of the perfused radioactive material was recovered from the various fetal tissues and perfusates in both experiments. Only approximately 20–40% of the 3H- and 10–25% of the 14C-labeled material administered was recovered from the perfusate. Very little 3H-labeled material was detected in any of the extracts of the fetal tissues and perfusates as unconjugated (free) material. Approximately 30% of the 14C- and 0.07% of the 3H-labeled conjugated material recovered from the perfusate was isolated as dehydroepiandrosterone sulfate (DHAS). Double-labeled dihydropregnenolone sulfate, 16α-hydroxypregnenolone sulfate, DHAS and pregnenolone sulfate (PS) were identified in the liver, whereas from the adrenal only PS and DHAS were isolated. These results are interpreted as demonstrating that the midtrimester human fetus is capable of effe...