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PubMed2000

Transient estrogen exposure of female mice during early development permanently affects osteoclastogenesis in adulthood.

Estrogens modulate bone tissue turnover in both experimental animal models and postmenopausal women. Our previous studies have shown that exposure to diethylstilbestrol (DES) during the perinatal period increases peak bone mass in female mice in adulthood. We investigated whether developmental DES exposure can influence bone mass by affecting osteoclastogenesis. Female mice were injected with 100 microg/kg body weight DES from days 9-16 of gestation or, alternatively, pups received neonatal injections of 2 microg of DES from days 1-5 of life. Animals were weaned at 21 days of age and effects of estrogen on bone cells were evaluated in adulthood. A significant increase in bone mass in female mice was already observed at 2 months, with a maximal effect in older animals. Bone sections from DES-treated animals showed a significant decrease in osteoclast number and tartrate-resistant acid phosphatase (TRAP) enzymatic activity as compared with controls. To verify the importance of the estrogen surge at puberty in this event, a group of control and DES-treated mice were ovariectomized at 17 days to prevent puberty, and potential effect on osteoclastic cells was evaluated in adulthood. As expected, ovariectomy induced an increase of TRAP-positive cells. DES treatment blunted the ovariectomized-dependent increase of the total number of osteoclastic cells, suggesting a role of developmental DES exposure in the process of bone-cell imprinting. Our data indicate, for the first time, that transient changes in estrogen levels during development modulate bone turnover and osteoclastogenesis likely participating in bone-cell imprinting during early phases of bone development, and that this effect could be induced by direct alteration of bone microenvironment.

Animals↗
PubMed2000

A dissociation in infants' memory for stimulus size: evidence for the early development of multiple memory systems.

Adults' memory performance on recognition (explicit memory) tests is sensitive to stimulus size, but their performance on priming (implicit memory) tests is not. This memory dissociation is taken as evidence for two, functionally distinct memory systems. Young infants, however, are thought to possess only a single representational system that supports implicit memory; the system that supports explicit memory is thought not to mature before 8-9 months of age. In two experiments with 54 infants, we asked if 3-month-olds exhibit a memory dissociation for stimulus size on recognition and priming tests. All infants learned to move a mobile displaying +s of a given size. In Experiment 1, infants recognized +s in the original size but not 33% smaller or larger. In Experiment 2, +s were effective memory primes in a reactivation task, irrespective of size. The finding that young infants exhibit a memory dissociation for stimulus size adds to growing evidence that two memory systems are functional from early in development.

Association Learning↗
PubMedDate not supplied

Potential phasic and tonic muscles express a common set of fast and slow myosin light chains and fast tropomyosin during early development of chick embryo.

We investigated the expression of myosin light chains and tropomyosin subunits during chick embryonic development of the anterior (ALD) and posterior (PLD) parts of the latissimus dorsi muscles. As early as day 8 in ovo, both muscles accumulate a common set of myosin light chains (LC) in similar ratios (LC1F: 55 per cent; LC2S: 25 per cent; LC2F: 12 per cent; LC1S: 8 per cent) and a common set of tropomyosin (TM) subunits (beta 2, beta 1, alpha 2F). Later during development, the slow components of the LC regularly disappear in the PLD and the fast components of the LC and the alpha 2FTM disappear in the ALD, so that the adult pattern is almost established at the time of hatching. Thus, early in development, the two muscles accumulate a common set of fast and slow myosin light chains and fast tropomyosin and some isoforms are repressed at a later stage during development. These data might suggest that during development, the regulatory mechanisms of muscle specific isoform expression differ from one contractile protein to another.

Animals↗
PubMed1999

Early development and composition of the human primordial plexiform layer: An immunohistochemical study.

The early expression of reelin, calcium-binding proteins (calretinin, calbindin, and parvalbumin), and neurofilament proteins have been explored in the developing central nervous system of human embryos and fetuses during the first trimester of gestation. Our objective has been to determine further the nature, developmental roles, and contributions of the early neurons and fibers of the original subpial neuropil, i.e., the primordial plexiform layer (PPL). In young embryos (4-5 weeks old), neurofilament protein-labeled fibers run through the subpial neuropil of the caudal portion of the neural tube, reaching the mesencephalon rostrally. At this age, calretinin-immunoreactive and calbindin-immunoreactive neurons are also found among cells already detached from the ventricular zone. The expression of neurofilament protein, calretinin, and calbindin follows an ascending caudorostral gradient, reaching the cerebral vesicles by the 6th-7th week of gestation. In the cerebral cortex, this timing coincides with the initial expression of reelin in the PPL. The reelin immunoreactivity throughout the most superficial cellular population of the cortical PPL supports the early genesis of Cajal-Retzius cells, around the 6th week of gestation. After the splitting of the PPL by the formation of the cortical plate (7-8 weeks of gestation), reelin-immunoreactive cells remain only in the newly established layer I. This study proposes that an initial PPL may be a universal feature of the developing central nervous system.

Calbindin 2↗
PubMed1998

Early development of the peripheral nervous system in a lancelet species.

The developmental pattern of the lancelet (amphioxus) peripheral nervous system from embryos to larvae has been studied by using wholemount immunostaining and transmission electron microscopy. The peripheral nerves first appeared on the anterior dorsal surface of the medulla at the middle neurula stage, when the anterior nerve cord was just closing. A single axon with a large growth cone was the progenitor of each nerve. The nerve roots adopted an asymmetric arrangement soon after. The first nerve, likely a pair of pure sensory nerves, sprouted from the anterior tip of the nerve cord. This nerve may be comparable topographically to the preoptic nerve (the posterior branch of the terminal nerve) in lungfishes. However, the neuron that first extends its axon was located in the medulla, as in the other posterior nerves. One of the extramedullary primary sensory neurons, the corpuscles of de Quatrefages, appeared in larvae with the mouth and two anterior gill pores. Their axons were seemingly fasciculated with the efferent axon of the first nerve. The second nerve, the most complex one to appear during embryonic and early larval development, innervated the preoral pit and the buccal region. The third and fourth nerves on the left side also innervated the buccal region. The larval innervation patterns in the anterior region differed from the adult organization, suggesting a segmental rearrangement of the nerve supply during development. There was no evidence to dichotomize the peripheral nerves into cranial and spinal nerves, as exist in vertebrates. These characteristics of the peripheral nervous system in the lancelet indicate that this animal has a rather derived or primitive developmental system of peripheral nerves, making the analysis of homology with vertebrates difficult.

Animals↗
PubMed1989

Characterization of a highly unstable mouse minisatellite locus: evidence for somatic mutation during early development.

A highly unstable mouse minisatellite locus, Ms6-hm, has been identified in mouse DNA fingerprints produced by cross-hybridization with human minisatellite probe 33.6. A 7-kb allele of Ms6-hm was cloned from a C57BL/6J mouse and collapsed to a 400-bp plasmid insert on propagation in Escherichia coli due to loss of the majority of minisatellite repeat units. Sequence analysis revealed that Ms6-hm has evolved by amplification within a member of the MT (mouse transcript) family of interspersed repetitive elements. Linkage analysis localized Ms6-hm near the brown coat color gene (b) on chromosome 4. Multiallelism and heterozygosity at this locus within inbred strains result from a high germline mutation rate to new-length alleles (2.5% per gamete). Mice mosaic for cells carrying a nonparental allele in somatic tissue, and in some cases also in the germline, provide evidence for additional, somatic, mutation events at Ms6-hm. In two mosaic mice the fraction of cells containing the nonparental allele has been shown to be indistinguishable in different adult tissues. These somatic mutation events at Ms6-hm must therefore occur very early in development, preceding the allocation of somatic lineages, and the same pool of primitive ectoderm cells must contribute equally to all somatic tissues. Under low-stringency hybridization conditions the collapsed subclone of Ms6-hm cross-hybridizes to other unstable loci in the mouse genome to generate a novel and highly individual specific mouse DNA fingerprint.

Alleles↗
PubMed1992

A human Id-like helix-loop-helix protein expressed during early development.

The interaction of helix-loop-helix (HLH) proteins is known to regulate the differentiation of several different tissues, including mammalian muscle and the insect peripheral nervous system. In myoblasts, the products of myogenic HLH genes such as MyoD and ubiquitous HLH proteins such as E12 are present at constant levels throughout development. An E12 monomer and a MyoD monomer form a DNA binding heterodimer that activates muscle-specific genes. These two proteins are unable to dimerize in proliferating myoblasts because a negative regulator HLH protein, Id, is present. We now report the sequence and structure of a human HLH gene related to Id, which has been designated Id-2. Two prominent Id-2 RNA molecules of 2.5 and 1.3 kilobases were found in a number of different human normal and neoplastic tissues. We believe the larger RNA is a precursor of the 1.3-kilobase mRNA that encodes an Id-2 protein of 134 amino acids. The HLH region of the Id-2 protein is 90% homologous to that of myogenic Id, but the homology is much less extensive outside the HLH region. The Id-2 gene is highly expressed during early fetal development in several tissues, including those of the central nervous system, but is not expressed in the corresponding mature tissues. Id-2 expression is modulated in association with retinoic acid-induced ganglionic differentiation of the neuroblastoma cell line SMS-KCNR. These findings suggest that Id-2 is an inhibitor of tissue-specific gene expression, although its distinctive pattern of expression during development suggests a role different from that of Id.

Amino Acid Sequence↗
PubMed2001

Novel control motif cluster in the IgH delta-gamma 3 interval exhibits B cell-specific enhancer function in early development.

The majority of the human Ig heavy chain (IgH) constant (C) region locus has been cloned and mapped. An exception is the region between C delta and C gamma 3, which is unstable and may be a recombination hot spot. We isolated a pBAC clone (pHuIgH3'delta-gamma 3) that established a 52-kb distance between C delta and C gamma 3. Sequence analysis identified a high number of repeat elements, explaining the instability of the region, and an unusually large accumulation of transcription factor-binding motifs, for both lymphocyte-specific and ubiquitous transcription activators (IKAROS, E47, Oct-1, USF, Myc/Max), and for factors that may repress transcription (Delta EF1, Gfi-1, E4BP4, C/EBP beta). Functional analysis in reporter gene assays revealed the importance of the C delta-C gamma 3 interval in lymphocyte differentiation and identified independent regions capable of either enhancement or silencing of reporter gene expression and interaction with the IgH intron enhancer E mu. In transgenic mice, carrying a construct that links the beta-globin reporter to the novel delta-gamma 3 intron enhancer (E delta-gamma 3), transgene transcription is exclusively found in bone marrow B cells from the early stage when IgH rearrangement is initiated up to the successful completion of H and L locus recombination, resulting in Ab expression. These findings suggest that the C delta-C gamma 3 interval exerts regulatory control on Ig gene activation and expression during early lymphoid development.

Amino Acid Motifs↗
PubMed2001

Estrogen and xenoestrogens upregulate the brain aromatase isoform (P450aromB) and perturb markers of early development in zebrafish (Danio rerio).

Estrogen synthesized in the brain itself by the action of cytochrome P450 aromatase (P450arom) is known to have permanent organizing effects on the developing CNS. In fish, estrogen upregulates the predominant brain isoform (P450aromB), implying that xenoestrogens (XE) could act as neurodevelopmental toxicants by altering P450aromB. To test this hypothesis, zebrafish embryos were exposed to 17beta-estradiol (E(2)), diethylstilbestrol (DES, a potent agonist), and bisphenol A (BPA, a weak agonist). RT-PCR/Southern transfer analysis showed that E(2) (0.01-10 microM) upregulated P450aromB in a dose-response manner. The effect of DES (0.01 microM) was similar to 1 microM E(2) (three- to four-fold higher than control), but BPA was less effective (<threefold increase at 10 microM). mRNA levels of the predominant ovarian isoform (P450aromA) were unchanged by estrogen. Treatment with E(2) (0.1-10 microM) between 2 and 72 hpf had dose-response effects on mortality and hatching and induced a 'curved tail down' phenotype characteristic of mutants with defects of early CNS development. The critical period of estrogen sensitivity for effects on mortality and curved tails was 2-24 hpf, whereas hatching effects were both stage- and duration-dependent. Developmental effects of DES and BPA were similar to E(2) but testosterone, and 5alpha-dihydrotestosterone were ineffective. 17alpha-Estradiol showed a small but significant effect on curved tails. We conclude that P450aromB mRNA is a sensitive marker of XE effect during embryogenesis, but further studies are required to determine whether changes in neural aromatase expression and estrogen biosynthesis have consequences for CNS development.

Animals↗
PubMed1991

Modulation of Na,K-ATPase expression during early development of Xenopus laevis.

In amphibian and mammalian systems, regulation of Na+ transport via the Na,K-ATPase plays an important role in distinct developmental processes such as blastocoele formation and neurulation. In this study, we have followed the Na,K-ATPase activity, the biosynthesis, and the cellular accumulation of catalytic alpha-subunits after fertilization of Xenopus laevis eggs up to neurula formation. Our data show that Na,K-ATPase activity increases significantly between stages 4 and 6 and again between stages 13 and 24. The four-fold rise in Na,K-ATPase activity during blastocoele formation is not mediated by an increased cellular pool of alpha-subunits. On the other hand, a five-fold increase of the biosynthesis rate around midblastula precedes a progressive accumulation up to neurula stage mainly of alpha 1-subunits and to a lesser extent of a second alpha-immunoreactive species. In contrast, newly synthesized glycoproteinic beta 1-subunits of Na,K-ATPase cannot be detected up to late neurula. These data indicate that (1) upregulation of Na,K-ATPase activity during blastocoele and neurula formation are mediated by different regulation mechanisms and (2) alpha- and possibly beta-isoforms are expressed in a developmentally regulated fashion during early Xenopus development.

Animals↗
PubMed2001

Expression of CD40 in vascular smooth muscle cells and macrophages is associated with early development of human atherosclerotic lesions.

CD40-CD154-mediated signaling has recently been described as playing a role in cellular functions involved in atherosclerotic processes. CD40 is expressed in macrophages, lymphocytes, endothelial cells, and vascular smooth muscle cells. However, cross-sectional studies investigating the expression of CD40 in atherosclerotic lesions are lacking. In the present study the expression of CD40 was studied in atherosclerotic lesions from 43 patients classified according to the World Health Organization criteria. Serial immunohistologic stainings of human iliac arteries from 43 patients were performed using monoclonal antibodies. Lesions were classified according to World Health Organization criteria, and CD40 expression was analyzed with regard to cell morphology and cellular markers by 2 independent observers. Human atherosclerotic lesions revealed a significant increase in intimal thickness, number of inflammatory infiltrates, and CD40-positive macrophages and vascular smooth muscle cells with progression of the lesions. This increase was most prominent from stage 0 to stage I. A significant correlation between intimal thickness and CD40-positive macrophages (r = 0.75, p <0.0005) and CD40-positive vascular smooth muscle cells (r = 0.81, p <0.0005) was observed. Ligation of the cellular CD40 receptor contributes to inflammatory cellular events in human vascular smooth muscle cells. These data suggest a direct association of CD40 expression in atherosclerotic lesions with early plaque development.

Aged↗
PubMed1976

Early development of gap junctions between the mouse embryonic myocardial cells. A freeze-etching study.

Using the freeze-etch technique, nexuses have been shown to exist at a very early stage in developing mouse hearts (10 dpc). At this time they are rare, but become more progressively frequent and extensive at 12 and 14 dpc. Special arrangements of particles progressively observed on the fracture faces PF (linear arrays, small associated groups of linear arrays, then hexagonal arrays with 'arms' formed by linear clusters) suggest that in ontogenesis the gap junctions may be built up by successive aggregation of the linear arrays of particles.

Animals↗
PubMed1998

NMDA receptor antagonists influence early development of GABAergic interneurons in the mammalian striatum

Neurotransmitters influence a wide variety of developmental processes. We hypothesize that N-methyl-d-aspartate (NMDA) glutamate receptors influence proliferation of populations of forebrain neurons. As our model, we use a subclass of GABAergic striatal interneurons that express the calcium binding protein parvalbumin (PV). To separate proliferative and post-proliferative effects of NMDA receptor antagonists on PV neurons, we first determined the birth-date of rat striatum PV neurons at the coronal level selected for analysis. Dividing striatal progenitor cells were marked by intraperitoneal injections of 5'-bromodeoxyuridine (BrdU) given to timed pregnant rats at selected time points between embryonic days (E) 12-22. Double immunohistochochemistry for BrdU and PV is used in adult progeny to determine the time course of neurogenesis of striatal PV neurons. The results of the neurogenetic analysis were then used for rational timing of treatment with competitive (CGS19755) and non-competitive (MK-801) NMDA receptor antagonists. In comparison to pair-fed and vehicle-injected controls, gestational rats given CGS-19755 and MK-801 during the proliferative phase (E15-E18) showed a marked reduction of striatal PV neuron cell density as adults. In contrast, animals given NMDA antagonists during the post-proliferative period (E18-E21) showed no significant reduction in PV neuron cell density compared to pair-fed controls. These results suggest that glutamate influences cell proliferation of a population of striatal neurons by an NMDA-mediated mechanism, suggesting a novel role for excitatory amino acids in early forebrain development.

Journal Article↗
PubMed1998

NMDA receptor antagonists influence early development of GABAergic interneurons in the mammalian striatum.

Neurotransmitters influence a wide variety of developmental processes. We hypothesize that N-methyl-D-aspartate (NMDA) glutamate receptors influence proliferation of populations of forebrain neurons. As our model, we use a subclass of GABAergic striatal interneurons that express the calcium binding protein parvalbumin (PV). To separate proliferative and post-proliferative effects of NMDA receptor antagonists on PV neurons, we first determined the birth-date of rat striatum PV neurons at the coronal level selected for analysis. Dividing striatal progenitor cells were marked by intraperitoneal injections of 5'-bromodeoxyuridine (BrdU) given to timed pregnant rats at selected time points between embryonic days (E) 12-22. Double immunohistochochemistry for BrdU and PV was used in adult progeny to determine the time course of neurogenesis of striatal PV neurons. The results of the neurogenetic analysis were then used for rational timing of treatment with competitive (CGS 19755) and non-competitive (MK-801) NMDA receptor antagonists. In comparison to pair-fed and vehicle-injected controls, gestational rats given CGS-19755 and MK-801 during the proliferative phase (E15-E18) showed a marked reduction of striatal PV neuron cell density as adults. In contrast, animals given NMDA antagonists during the post-proliferative period (E18-E21) showed no significant reduction in PV neuron cell density compared to pair-fed controls. These results suggest that glutamate influences cell proliferation of a population of striatal neurons by an NMDA-mediated mechanism, providing evidence for a novel role for excitatory amino acids in early forebrain development.

Animals↗
PubMed2003

Relationship between differences of gene expression in early developing seeds of hybrid versus parents and heterosis in wheat.

In order to understand molecular basis of heterosis, mRNA differential display was used to analyze the differences in gene expression between seeds of 18 reciprocal hybrids and their 6 parents at 6th day after pollination. The relationship between gene expression patterns and heterosis was determined. Only bands that can be repeated in duplicate PCR were used for analysis so as to reduce false positive bands. Among the total of 2,025 bands displayed, 1,386 bands (68.43%) were reproducible. Eight patterns (fifteen kinds) of gene expression were observed, which include: (1) bands occurring in only one parent (two kinds); (2) bands observed in both hybrids and one parent (two kinds); (3) bands detected in parents and one hybrid (two kinds); (4) bands displayed in only one hybrid (two kinds); (5) bands revealed in one hybrid and its corresponding female (two kinds) or male (two kinds) parent; (6) bands visualized in only both hybrids (one kind); (7) bands occurring in only parents (one kind); (8) bands observed in parents and both hybrids (one kind). Our results indicate that differences of gene expression between hybrids and their parents are very obvious. The percentages of bands observed in only both hybrids and in only both parents are lower. The analysis shows that bands observed in parents and both hybrids are not correlated with all nine agronomic traits, which indicates differentially expressed genes are mainly responsible for the observed heterosis. At least one pattern of differential gene expression is significantly correlated with nine agronomic traits. Silenced bands in hybrid (which include bands occurring in only one parent, bands detected in both parents and one hybrid and bands in only parents) and bands present in one hybrid and its corresponding female or male parent are likely to play important roles in heterosis. These results suggest that early seed development could be closely related to heterosis.

Gene Expression Regulation, Developmental↗
PubMed1996

Growth of dorsal spinocerebellar axons through a lesion of their spinal pathway during early development in the North American opossum, Didelphis virginiana.

Supraspinal axons grow around or through lesions of their spinal pathway during specific critical periods of mammalian development, but comparable plasticity has not been documented for axons which form ascending tracts. In the present study, we asked whether axons of the dorsal spinocerebellar tract (DSCT) are capable of such growth. The spinal cord of the North American opossum, Didelphis virginiana, was hemisected at mid-thoracic levels between postnatal day (PD) 5 and 68 and after varying survival times, bilateral injections of Fluoro-Gold or Fast Blue were made into the anterior lobe of the cerebellum, the major target of DSCT axons. Seven days later, the pups were sacrificed and their spinal cord processed for fluorescence microscopy. In animals lesioned between PD5 and 9, and allowed to survive for 37-269 days, neurons were labeled bilaterally in Clarke's nucleus (CN) caudal to the lesion, but they were fewest in number and smallest in size on the lesioned side. Since the DSCT originates almost entirely within CN on the ipsilateral side, we conclude that the neurons labeled ipsilateral and caudal to the lesion supported axons which grew around or through it. Histological examination revealed that recognizable spinal cord was present at the lesion site and that labeled spinocerebellar axons were located in their normal position ipsilateral to the lesion. It appears, therefore, that growth occurred through the lesion. In animals lesioned between PD13 and 68, labeled neurons were not found in CN caudal and ipsilateral to the lesion although they were present on the contralateral (control) side. We conclude that DSCT axons, like axons which form descending tracts, grow through a lesion of their spinal pathway if it is made early in development.

Animals↗