Fetuses Of Different Gestational Ages Research Articles

Femoral Neck Anteversion and Neck Shaft Angles: Determination and their Clinical Implications in Fetuses of Different Gestational Ages.

Precise anatomical assessment of femoral neck anteversion (FNA) and the neck shaft angles (NSA) would be essential in diagnosing the pathological conditions involving hip joint and its ligaments. The present study was undertaken on 48 fetal femurs to calculate the NSA and FNA in fetuses digitally.End on images of upper end of the femurs were taken for the estimation of FNA and a photograph in a perpendicular plane was taken to calculate the NSA. Microsoft Paint software was used to mark the points and Image J software was used to calculate the angles digitally.The FNA ranged from 17.08º to 33.97 º on right and 17.32 º to 45.08 º on left. The NSA ranged from 139.33 º to 124.91 º on right and 143.98 º to 123.8 º on left. Unpaired t test showed the FNA and NSA of femur did not vary significantly during the third trimester.

Histogenesis of human foetal cerebellar cortex

The objective of present study is to describe the prenatal histogenesis of human cerebellar cortex. The aim of this study is to demonstrate the various histological features of human foetal cerebellum in spontaneously aborted fetuses of different gestational ages for analyzing the cerebellar histology. Histogenesis of cerebellum is observed from 13 weeks to 36 weeks of gestational age by dividing the specimens into six gestational age groups (group A to group F). External granular layer is observed at 13 weeks of gestation and purkinje cell layer is arranged at 17 weeks as a multilayered and single layer at 36 weeks of gestation. The knowledge of cerebellar anatomy has a tremendous neurosurgical importance. Future investigations might involve evaluation of the cerebellum at other gestational ages. Keywords: Cerebellum, Histogenesis, Purkinje cell

Determination of inter-bronchial and subcarinal angles in fetuses of different gestational age and their clinical implication

Introduction: The trachea-bronchial angles in the human fetus are of increasing relevance in perinatal medicine to determine both normal and pathological criteria. The present study was undertaken to calculate the inter-bronchial angle using a novel method by an image analyzer at different gestational ages. Materials and Methods: The present study was carried out using 24 human fetuses in the department of Anatomy, Kasturba Medical College, Manipal. The right and left bronchial, inter-bronchial and subcarinal angles were calculated by using an image analyzer named Image J. Results: The right bronchial angle ranged from 21.99° to 43.96°. The left bronchial angle ranged from 29.48° to 56.21°. The inter-bronchial angle ranged from 60.53° to 100.86°. Student t test was applied to compare the means of bronchial angles between the second and third trimesters which did not show any statistical significance. The subcarinal angle ranged from 41.69° to 74.88° with an average of 61. 15 ± 9.73°. Conclusion: The present study analyses the inter-bronchial and subcarinal angles in different GA, the knowledge of which would be essential to understand the developmentaln changes of the respiratory passages.

Histogenesis of gastric mucosa: A human foetal study

The development of gastric mucosa and the precise description of cardia in developing foetus are still controversial. Hence, this research was conducted to study the histogenesis of gastric mucosa and time of appearance and distribution of its various cell types in developing foetuses of different gestational ages. Ten aborted human foetal autopsy specimens of stomach of gestational ages 10–26 weeks were procured after informed consent. It was immersed fixed in 10% formalin and then sectioned and stained with Haematoxylin and Eosin, Periodic Acid Schiff’s, Bodian’s reducing Silver and PAS Toluidine blue Aurantia stain. Mucus and enteroendocrine cells were found to be the earliest differentiated cells, lining the gastric glands at 10 weeks and further differentiation of parietal and chief cells at 12 weeks. Basal coiling of the glands started at 14 weeks. As the age advanced appreciable differentiation of the gastric mucosa was observed as mucus cells lining the surface, pits and upper part of the gland. The enteroendocrine and chief cells in the base of glands and parietal cells were interspersed with other cell types. Parietal cells were sparse in whole stomach during 20–24 weeks and vanished from pylorus at 26 weeks. The present study established the presence of cardiac mucosa and affirmed that cardiac glands are mixed glands containing both mucus and parietal cells. Pyloric mucosa was more developed with thicker mucosa and denser glands as compared to rest of the gastric region. Copyright © 2014, Indian Journal of Medical Specialities. Published by Reed Elsevier India Pvt. Ltd. All rights reserved.

Some features of the developmental uterus in human fetuses

Proper development of each component of the reproductive tract is imperative for successful natural reproduction. The aim was to investigate some morphological features of the fetal uterus in early phases of its development. The uteruses of 65 fetuses of different gestational age were included and each of them was measured in three dimensions: uterine length (UL), uterine width (BC) and the antero-posterior (sagittal) thickness of the uterine fundus (FT) using ImageJ computer program. It was observed that the most intense fetal uterus growth occurred between seventh and eighth month of gestational age (between week 25 and 31). The most intense rate of uterine growth had UL and it showed steeper growth curve from the fourth month of gestational age. The values of UL, BC, FT showed statistically highly positive Pearson’s linear correlation with values of CRL, and GA, and among themselves. The strongest correlation was between UL and gestational age. Contrary to proved rising linear trends of UL/FT and UL/BC, BC/FT performed linear trend of decline. However, two divergent linear trends, one ascending (UL/FT), and other declining (BC/FT) have similar descent in values during the early gestational age, from week 12 to 15. Fetal uteruses did not grow at the same rate by all three measured dimensions, and each of measured dimensions has noticeable standard deviations during gestational periods, even with a resolution of a week, suggesting individuality of each human development/growth even during prenatal life.

Immunohistochemical expression of types I and III collagen antibodies in the temporomandibular joint disc of human foetuses

The objective was to study the morphology of the articular disc and analyse the immunohistochemical expression of types I and III collagen markers in the temporomandibular joint (TMJ) disc of human foetuses of different gestational ages. Twenty TMJ from human foetuses supplied by Universidade Federal de Uberaba with gestational ages from 17 to 24 weeks were studied. The gestational age of the foetuses was determined by measuring the crown-rump (CR) length. Macroscopically, the foetuses were fixed in 10% formalin solution and dissected by removing the skin and subcutaneous tissue and exposing the deep structures. Immunohistochemical markers of type I and III were used to characterize the existence of collagen fibres. Analysis of the immunohistochemical markers of types I and III collagen revealed the presence of heterotypical fibril networks.

Transplacental toxoplasmosis in naturally-infected white-tailed deer: Isolation and genetic characterisation of Toxoplasma gondii from foetuses of different gestational ages

Clinical toxoplasmosis is most severe in congenitally-infected hosts. In humans, transmission of Toxoplasma gondii from the mother to the foetus is considered to be most efficient during the last trimester of pregnancy but clinical congenital toxoplasmosis is more severe if transmission occurs during the first trimester. However, there are no data on the rate of congenital transmission of T. gondii with respect to gestational age in any host during natural infection. In the present study, attempts were made to isolate T. gondii by bioassay in mice inoculated with tissues from foetuses of 88 naturally-exposed white-tailed deer from Iowa and Minnesota. Viable T. gondii was isolated from foetuses of six of 61 deer in early pregnancy (45–85 days of gestation) from Iowa and foetuses of nine of 27 deer from Minnesota in mid-gestation (130–150 days) of a gestational period of 7 months. The 15 T. gondii isolates obtained from foetal deer were PCR-restriction fragment length polymorphism genotyped using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22–8, c29–2, L358, PK1 and an apicoplast marker, Apico. Five genotypes were revealed, including the clonal Type II and III lineages, and three non-clonal genotypes. DNA sequencing analysis of representative isolates at loci SAG2, c22–8, L358 and PK1 revealed that the three non-clonal genotypes are closely related to the clonal Type I, II and III lineages. It is very likely that these non-clonal genotypes were derived from genetic crosses among the three clonal Type I, II and III lineages. The most common genotype was Type II, commonly found in humans in North America and Europe, suggesting the possible link of transmission from game animals to humans.

Critical periods during development of the dentate nucleus and their clinical significance

The aim of this study was to identify the critical periods in the development of the human dentate nucleus in fetuses of different gestational ages and in one newborn brain. The fetal brains were fixed in alcohol-formalin-acetic acid, embedded in paraffin, cut into 30 micro sections, and stained with cresyl violet. The sections were examined by light microscopy. In order to identify vulnerable periods, histological and stereological analyses were done. FORMATION OF THE DENTATE NUCLEUS: The first appearance of the dentate nucleus was noticed in fetus of 12.5 weeks of gestation (wg), and its cells corresponded to the first and second stage of maturation. Formation of the dorsomedial lamina begins at the end of the 13th wg, and it starts to fold at 19.5 wg. At this time, cells correspond to the third stage of maturation, and formation of the ventromedial lamina begins. The first folds of the ventromedial lamina are noticed at 23.5 wg. Fourth stage maturity cells are noticed at 23.5 wg. remaining conspicuous up to birth. The numerical density of the nerve cell nuclei shows a constant decrease. Based on our results, we can conclude that during development of the dentate nucleus, there are two vulnerable periods. The first one corresponds to the fourth month of intrauterine life, and the second to the intensive growth of the dorsomedial and ventrolateral lamina (20.0 - 24.5 wg).

Developmental Changes in Endothelial Vasoactive and Angiogenic Growth Factors in the Human Perinatal Lung

Little is known of the mechanisms underlying the marked fall in pulmonary vascular resistance that occurs at birth, but changes in the expression of endothelial vasoactive and angiogenic factors during lung development might play a key role. Nitric oxide, endothelin-1, and vascular endothelial growth factor have critical effects on vascular tone and cell growth. Here, we investigated the protein expression of endothelial nitric oxide synthase, endothelin-1 and its receptors, and vascular endothelial growth factor in pulmonary necropsy samples from 14 fetuses of different gestational ages and from 5 infants. Expression of endothelin-1 and its receptor endothelin-A was strong and stable. In contrast, expression of the endothelin-B receptor was weak in early gestation, then increased markedly in mid-gestation and remained high thereafter. The expression of endothelial nitric oxide synthase and vascular endothelial growth factor fell markedly after mid-gestation and remained low thereafter. These data point to a discrepancy between maturational and functional changes in human pulmonary vascular structures. The weak perinatal expression of endothelial nitric oxide could suggest that other potent vasodilatory mediators are responsible for the marked vasodilation observed at birth.

Relationship between vascular development and vascular differentiation during liver organogenesis in humans

Backgrounds/Aims: The complex vascular architecture characteristic of the normal adult liver is progressively acquired during the fetal life. In this study, we aimed to evaluate the relationship between angiogenesis and vascular differentiation during liver organogenesis. Methods: We studied, in 51 fetuses of different gestational ages, the expression of markers of endothelial cell differentiation, integrins, pro- and anti-angiogenic extracellular matrix components, vascular endothelial growth factor (VEGF) and its receptors. Results: Three main stages in the development of the vascular architecture of the liver were identified: (a) from 5 to 10 gestation weeks (GW), no evidence of de novo angiogenesis was detected; the vessels present in the liver primordium were the precursors of portal veins and sinusoids, deriving from preexisting vessels; (b) from 10 to 25 GW, angiogenesis and vasculogenesis resulted in the development of, respectively, arteries and intra-portal capillaries, while portal veins and hepatic sinusoids followed a differentiation process; (c) after 25 GW, little changes were detected in the various vascular compartments. The maximal expression of VEGF and its receptors was from 5 to 25 GW. Conclusions: The development of the hepatic vascular architecture is a multistep process combining angiogenesis, vasculogenesis and vascular differentiation, regulated by specific growth and differentiation factors including VEGF.

Changes in sialic acid expression in the lung during intrauterine development of the human fetus

Sialic acid is a component of glycoproteins that influences enzymatic and receptor functions of cells. During proliferation and differentiation of tissues, sialic acid can serve as a recognition determinant in intercellular communication and interactions of cells with the extracellular matrix. In the present study, sialic acid expression in relation to developmental maturity of the lung has been studied. We analyzed 12 necroptic lung specimens from foetuses of different gestational ages from the 15th week to the neonate. Sections were stained histochemically using 3 lectins specific for sialic acid: Tritrichomonas mobilensis lectin (TML), specific for sialic acid without linkage preference, Sambucus nigra agglutinin (SNA), specific for alpha2,6-linked sialic acid, and Maackia amurensis leucoagglutinin (MAL), specific for alpha2,3-linked sialic acid. MAL positivity dominated over SNA positivity showing prevalence of alpha2,3-linked sialic acids to be homogeneously distributed in the lung at the canalicular stage of development. In more mature lungs, well-differentiated bronchial epithelium showed strong sialic acid expression of both linkages. Sialic acid with alpha2,6 linkage dominated in vascular endothelium. Our results showed a slight decrease in sialic acid expression in lungs with gestational age to a relative minimum before birth. Lectin staining of mature lung tissue showed intense sialic acid expression in alveolar epithelial type II cells. Changes in expression of specific sialic acids during differentiation of the lungs may be useful as marker of the degree of maturity of the foetus.

Origin of cardiac mucosa: ontogenic consideration.

The origin and histology of the cardiac mucosa remains controversial. The classical concept that the cardiac mucosa is of gastric origin has been challenged by those who advocate that the cardiac mucosa results from a metaplastic esophageal process. Some regard cardiac mucosa as consisting solely of pure mucous glands, whereas others accept the presence of isolated parietal cells within the mucous gland (mixed glands). In this study, we have clarified the presence and site of origin of the cardiac mucosa and its histological composition. To do so we studied the microscopic characteristics of the gastric side of the squamous-columnar junction (SCJ) of 77 autopsied fetuses of different gestational ages (prenatal group) and of infants, young children, and adolescents (postnatal group). We evaluated the presence or absence of a transitional zone, defined as the area between the squamous esophageal and oxyntic mucosa, the glandular composition of the transitional zone (i.e., pure mucous and mixed glands), and the presence or absence of inflammation. Our study revealed that a transitional zone with the microscopic characteristics of cardiac mucosa was universally present at the SCJ. The microscopic characteristics of this zone varied with age. Both pure mucous and mixed glands were observed. We conclude that the cardiac mucosa is partially if not entirely the result of normal embryonic gastric development. Both mucous and mixed glands constitute normal components of the cardiac mucosa.

Contribution of Apoptosis and Apoptosis-Related Proteins to the Malformation of the Primitive Intrahepatic Biliary System in Meckel Syndrome

In the developing liver, the complete or partial persistence of the primitive double-layered cylinder of biliary-type cells that surrounds the branches of portal vein and its mesenchyme gives origin to portal tracts with an increased number of bile duct structures. The term "ductal plate malformation of the liver" was coined to label the insufficient remodeling of the primitive intrahepatic biliary system. Meckel syndrome is an autosomal recessive inherited disease characterized by occipital encephalocele, postaxial polydactyly, diffuse cystic renal dysplasia, and malformation of the ductal plate of the liver. We studied 52 fetuses with Meckel syndrome from five German centers (Berlin, Freiburg, Heidelberg, Mainz, and Marburg). Analysis of apoptosis and cell proliferation (Ki-67) was performed by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) and immunohistochemistry in the liver of 24 normal fetuses of different gestational ages (14-38 weeks of gestation) and in 14 fetuses with Meckel syndrome (17-38 weeks of gestation). The expression of two apoptosis-related proteins, Fas (a transmembrane cell surface protein involved in the apoptosis) and Bcl-2 (an anti-apoptotic protein), was studied by immunohistochemistry in the liver of 11 normal fetuses of different gestational ages (14-40 weeks of gestation) and in 40 fetuses with Meckel syndrome (16-38 weeks of gestation). In control fetuses, apoptosis rate and cell proliferation were high in the remodeling ductal plate and moderate in the ductal plate and in remodeled bile ducts. During gestation, expression of Fas and Bcl-2 decreased and increased, respectively. The malformed ductal plates in the fetal livers with Meckel syndrome showed a marked decrease in the apoptotic rate and Fas expression and an increase in proliferative activity and Bcl-2 expression in comparison with control fetuses. Furthermore, by linear regression analysis, we found that both proliferation activity and apoptosis rate in the ductal plate malformation of fetuses with Meckel syndrome were practically constant along the gestation. These results, which represent the first systematic study of apoptosis in ductal plate malformation of the liver, indicate that 1) animals harboring the gene defect of Meckel syndrome could be a good model for the study of the abnormal development of the primitive intrahepatic biliary system, 2) a decreased cell turnover occurs in the ductal plate malformation of fetuses with Meckel syndrome, and 3) the increase of Bcl-2 expression contributes to the pathogenesis of the lack of remodeling of ductal plate of the liver in Meckel syndrome.

Quantitative immunophenotypic characterization, cryopreservation, and enrichment of second- and third-trimester human fetal cord blood hematopoietic stem cells (progenitor cells)

Objective: The aims of this study were (1) to assess the hematopoietic stem cell (progenitor cell) contents of umbilical cord blood samples from second-trimester and early-third-trimester fetuses versus term fetuses and (2) to determine the feasibility of cryopreservation and enrichment of cord blood from fetuses of different gestational ages. Study Design: Cord blood between 13 and 42 weeks’ gestation (n = 31) was sampled after delivery or fetal expulsion. Fluorescence-activated cell sorting was used to measure CD34 + and CD34 + CD38 – cell numbers. Samples were cryopreserved with 10% dimethylsulfoxide, and CD34 + enrichment was performed by magnetically activated cell sorting with the MiniMACS system (Miltenyi Biotech, Bergisch Gladbach, Germany). Kruskal-Wallis analysis of variance and the Mann-Whitney U test were used for analysis of data. Results: CD34 + and CD34 + CD38 – cell contents were significantly higher in second- and early third-trimester fetuses than in term fetuses (CD34 + 2.57% ± 0.38%, 1.48% ± 0.31%, and 0.7% ± 0.13%, respectively, P = .0067; CD34 + CD38 – 0.72% ± 0.26%, 0.18% ± 0.05%, and 0.06% ± 0.02%, respectively, P = .0132). Mononuclear cell recovery, viability, and CD34 + cell purity after cryopreservation and enrichment were similar among different gestational ages. Conclusion: Cord blood stem cell content decreases significantly from the second trimester to term. Cryopreservation and enrichment of these cells from earlier gestational ages is feasible. This might be especially useful for allogeneic stem cell transplantation and for in utero gene therapy. (Am J Obstet Gynecol 1998;179:1228-33.)

Fetal growth retardation as a cause of impaired ovarian development.

Low birthweight has been associated with diseases and disorders later in life. It has been suggested that this is caused by the impaired development of abdominal organs, especially in cases of growth retardation. Besides general malnutrition of the fetus, preferential bloodflow to the heart and brain may further deprive organs, such as liver, pancreas and kidney, of nutrients. As a result these organs may not develop properly. Anatomically, the ovary is situated close to the kidney and it is very likely that, similar to the kidney, ovarian development can be negatively affected by intra-uterine growth retardation. Placental insufficiency, which is an important cause of severe intra-uterine growth retardation, was used as a model to investigate this hypothesis. In the present study, the volume percentages of primordial follicles in the ovaries of four severely growth-retarded fetuses of different gestational ages are compared to those of four age-matched controls. It is found that these volume percentage in growth-retarded fetuses were significantly lower than those observed in the age-matched controls. It can be concluded that ovarian development is impaired in intra-uterine growth-retarded fetuses. These findings further suggest that, as a result of the premature loss of follicles, females with low birthweights may encounter fertility problems later in life.

Structural and Functional Differentiation of Sinusoidal Endothelial Cells During Liver Organogenesis in Humans

During fetal life, human liver sinusoids, which differentiate between 4 and 12 weeks of gestation from capillaries of the septum transversum, must support an important hematopoietic function and acquire the structural and functional characteristics of adult sinusoids. To gain insight into their differentiation process, we studied the expression of (1) markers of continuous endothelia, absent from adult sinusoidal endothelial cells (PECAM-1, CD34, and 1F10); (2) functional markers of adult sinusoidal endothelial calls (CD4, 1CAM-1, CD32, and CD14); and (3) extracellular matrix components (laminin, tenascin, fibronectin, and thrombospondin) in 37 fetuses of different gestational ages. We identified two successive differentiation events. (1) An early structural differentiation, occurring from 5 to 12 weeks of gestation, was characterized by the loss of continuous endothelial cell markers and a reduction in the perisinusoidal amount of laminin and in the deposition of tenascin, fibronectin, and thrombospondin; at the end of this process, fetal liver sinusoids present structural characteristics comparable to those of the sinuses in adult hematopoietic bone marrow. (2) A later functional differentiation was characterized by the acquisition of the markers of adult sinusoidal endothelial cells, initiating at 10 weeks of gestation and completed by 20 weeks of gestation; this process likely contributes to adapt liver sinusoids to the specific functions of the adult hepatic tissue.

Use of Placental Cord Serum in Cultures of Human Fetal Hepatocytes: Its Assessment with Carbamyl Phosphate Synthetase and Argininosuccinate Lyase as Marker Enzymes.

Isolated human fetal hepatocytes could be successfully cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with placental cord serum, which is a rich source of various growth factors. These cultured hepatocytes were found to maintain their viability, morphological integrity, and detoxifying capacity. The expression of two urea-cycle enzymes, i.e., carbamyl phosphate synthetase (CPS) and argininosuccinate lyase (ASL), was studied in isolated and cultured hepatocytes from human fetuses of different gestational age classified as Group I: 17-20 weeks, Group II: 21-24 weeks, Group III: 25-28 weeks, Group IV: 29-32 weeks, and Group V: 33-36 weeks. We found that on culture the activities of the two enzymes increased for a period of 4-6 days. Hepatocytes of Group I and Group II showed maximum expression of CPS by the 6th day of culture, whereas those of Groups III, IV, and V showed theirs by the 5th day of culture. In the case of ASL the maximum levels were seen by the 4th day of culture, after which the activities of both enzymes decreased. CPS activity in cultured hepatocytes was about 1.4-4.7 times higher whereas that of ASL was about 1.2-1.6 times higher, when compared with that of freshly isolated cells.This study indicates that isolated hepatocytes undergo reversible changes and that on culture for 4-6 days, liver cell functions recover with enhanced enzyme activities. Cultured human fetal hepatocytes of Group III gestation would appear to be more suitable for transplantation than isolated hepatocytes.

An immunohistochemical study of the fetal sheep neocortex and cerebellum with antibodies against nervous system-specific proteins

The topographical distribution of glial fibrillary acidic protein (GFAP), vimentin, neuron-specific enolase (NSE) and neurofilament (NF) proteins in the developing neocortex and cerebellum of sheep fetuses of different gestational ages (60-149 days) was described. For comparison, brain tissues from a lamb and two adult sheep were included in this study. In the walls of the developing cerebral hemispheres GFAP- and vimentin-immunoreactive radial glial fibres were demonstrated. From 80 days of gestation onwards a continuous decrease of radial fibres occurred which was accompanied by an increase of GFAP-positive mature astrocytes. In Bergmann glial fibres of the cerebellum, which are the equivalent of radial fibres in the telencephalon, both GFAP and vimentin were detectable in fetuses and adult sheep. With polyclonal antibodies against NSE and NF proteins (NF-M, NF-H) prominent staining of neuronal fibre tracts was seen in fetuses of all gestational ages studied. In the neocortex, staining for NF-L did not occur before day 80 of gestation. With monoclonal antibodies against phosphorylated NF-H (clone SMI 31), however, reaction of neocortical fibre tracts was first seen at 85 days of gestation, and cytoplasmic staining of single neocortical neurons was first found in a 149-day-old fetus. Several fixatives and proteolytic pretreatment were examined for their effects on preservation and re-establishment of marker protein expression, respectively. GFAP and vimentin in radial glial fibres were not demonstrable without pretrypsinization of tissue sections. The most intensive staining of NF proteins with polyclonal antisera was seen in brains fixed in Bouin's fluid.

Infection of ovine fetal brain cell cultures with cytopathogenic and non-cytopathogenic bovine viral diarrhoea virus

The in vitro cell tropism of non-cytopathogenic (ncp) and cytopathogenic (cp) bovine viral diarrhoea virus (BVDV) was studied in primary dissociated brain cell cultures derived from ovine fetuses of different gestational ages. The cell types infected were identified by double immunofluorescence using antibodies against BVDV and cell type-specific markers. In cultures infected with ncp BVDV viral antigen was present in neurofilament (NF 200 kDa)-positive neurons, glial fibrillary acidic protein (GFAP)-positive astrocytes and fibronectin-expressing cells. Estimation of the percentages of individual cell types infected with ncp BVDV indicated a tropism for NF 200-positive neurons. In cultures infected with cp BVD virus cytopathic changes were observed beginning at 40 hours post infection. Viral antigen was present in vacuolated NF 200-, GFAP- and fibronectin-positive cells. In comparison with non-infected control cultures a considerable reduction of the number of the different cell types was seen.

Comparison of rates of neuronal development and survival in human and rat cerebral cortical cell cultures

A problem that has not been addressed directly at the cellular and molecular levels concerns the basic mechanisms governing rates of development and aging in the nervous system. We have begun to examine this problem by employing parallel cell cultures of cerebral cortical neurons taken from rat and man, two species with markedly different developmental periods and life spans. Cortical cultures were established from rat and human fetuses and were maintained under identical conditions. Long-term neuronal survival in human cortical cultures was strikingly greater than in rat cortical cultures, and axonal outgrowth was significantly slower in the human neurons. These differences were consistently observed in a variety of culture media. Exchanges of culture medium between cultures of the two species did not alter the differences in neuronal survival and axon outgrowth suggesting that the differences between human and rat neurons were probably not due to factors released into the culture medium. Furthermore, the differences were not related to developmental stage at the time of culture initiation since similar results were obtained in cultures established from fetuses of different gestational ages. These initial data indicate that differences in the developmental time courses and life spans of human and rat cerebral cortex are reflected at the level of the individual neuron, and provide a system in which to explore the mechanisms responsible for these differences.