Developmental genetics

Summary Of particular concern to the human geneticist are the effects of genetic abnormalities on development. To gain an understanding of these effects it is necessary to engage in a reciprocal process of using knowledge of normal developmental events to elucidate the mechanisms operative in abnormal situations and then of using what is learned about these abnormal situations to expand our understanding of the normal. True developmental genes have not been described in man, although it is likely that they exist, but many developmental abnormalities are ascribable to mutations in genes coding for enzymes and structural proteins. Some of these even produce multiple malformation syndromes with dysmorphic features. These situations provide a precedent for asserting that not only monogenic developmental abnormalities, but also abnormalities resulting from chromosome imbalance must ultimately be explicable in molecular terms. However, the major problem confronted by the investigator interested in the pathogenesis of any of the chromosome anomaly syndromes is to understand how the presence of an extra set of normal genes or the loss of one of two sets of genes has an adverse effect on development. Several molecular mechanisms for which limited precedents exist may be considered on theoretical grounds. Because of the difficulties in studying developmental disorders in man, a variety of experimental systems have been employed. Particularly useful has been the mouse, which provides models for both monogenic and aneuploidy produced abnormalities of development. An example of the former is the mutation oligosyndactylism which in the heterozygous state causes oligosyndactyly and in the homozygous state causes early embryonic mitotic arrest. All whole arm trisomies and monosomies of the mouse can be produced experimentally, and of special interest is mouse trisomy 16 which has been developed as an animal model of human trisomy 21 (Down syndrome). In the long run, the most direct approach to elucidating the genetic problems of human development will involve not only the study of man himself but also of the appropriate experimental models in other species.Acknowledgments. This review was written while the author was a Henry J. Kaiser Senior Fellow at the Center for Advanced Study in the Behavioral Sciences, Palo Alto, California. This work was supported by grants from the National Institutes of Health (GM-24309, HD-03132, HD-15583, HD-17001) and the American Cancer Society (CD-119) and by a contract from the National Institute of Child Health and Human Development (NOI-HD-2858).     

Developmental genetics

Of particular concern to the human geneticist are the effects of genetic abnormalities on development. To gain an understanding of these effects it is necessary to engage in a reciprocal process of using knowledge of normal developmental events to elucidate the mechanisms operative in abnormal situations and then of using what is learned about these abnormal situations to expand our understanding of the normal. True developmental genes have not been described in man, although it is likely that they exist, but many developmental abnormalities are ascribable to mutations in genes coding for enzymes and structural proteins. Some of these even produce multiple malformation syndromes with dysmorphic features. These situations provide a precedent for asserting that not only monogenic developmental abnormalities, but also abnormalities resulting from chromosome imbalance must ultimately be explicable in molecular terms. However, the major problem confronted by the investigator interested in the pathogenesis of any of the chromosome anomaly syndromes is to understand how the presence of an extra set of normal genes or the loss of one of two sets of genes has an adverse effect on development. Several molecular mechanisms for which limited precedents exist may be considered on theoretical grounds. Because of the difficulties in studying developmental disorders in man, a variety of experimental systems have been employed. Particularly useful has been the mouse, which provides models for both monogenic and aneuploidy produced abnormalities of development. An example of the former is the mutation oligosyndactylism which in the heterozygous state causes oligosyndactyly and in the homozygous state causes early embryonic mitotic arrest. All whole arm trisomies and monosomies of the mouse can be produced experimentally, and of special interest is mouse trisomy 16 which has been developed as an animal model of human trisomy 21 (Down syndrome). In the long run, the most direct approach to elucidating the genetic problems of human development will involve not only the study of man himself but also of the appropriate experimental models in other species.     

Developmental forms of human skeletal muscle AMP-deaminase

Chromatography on phosphocellulose revealed the existence of two well-separable forms of skeletal muscle AMP-deaminase in the tissue extracts of 11- and 16-week-old human fetuses. One of these forms elutes from the column at the same salt concentration as the muscle isozyme found in the skeletal muscle extract from adult man, and seems to have similar kinetic properties. The second form, which was found only in vestigial amounts in adult human tissue extract, represents different kinetic properties and seems to be a form characteristic for the fetal period of ontogenesis.     

GIS的功能与发展趋势探析

GIS自诞生到如今经历40年的历史，无论是功能还是应用领域都有长足的进步。计算机技术和社会需求始终是GIS产生与发展的基础与动力，社会应用领域的扩大化、应用层次的多样化和应用人员的复杂化向GIS的技术与功能提出了新的挑战。本文主要阐述了GIS的核心功能、关键技术及其应用，并对其发展趋势略作探讨。     

Developmental control of the orientation of cuticular structures inDrosophila

Summary A scanning electron microscope study of bristle mutations inDrosophila melanogaster has shown that the cell hairs (trichomes) can be altered in predictable ways. The trichomes appear to act as markers of a diffusion gradient dttermining the orientation of cuticular structures in the thorax.We are grateful to W.F. Chissoe and M.R. Whitmore for theil help with the electron microscopy.This work was supported by DHEW-NIGMS grant GM2480901.     

Developmental and pathological angiogenesis in the central nervous system

Angiogenesis, the formation of new blood vessels from pre-existing vessels, in the central nervous system (CNS) is seen both as a normal physiological response as well as a pathological step in disease progression. Formation of the blood–brain barrier (BBB) is an essential step in physiological CNS angiogenesis. The BBB is regulated by a neurovascular unit (NVU) consisting of endothelial and perivascular cells as well as vascular astrocytes. The NVU plays a critical role in preventing entry of neurotoxic substances and regulation of blood flow in the CNS. In recent years, research on numerous acquired and hereditary disorders of the CNS has increasingly emphasized the role of angiogenesis in disease pathophysiology. Here, we discuss molecular mechanisms of CNS angiogenesis during embryogenesis as well as various pathological states including brain tumor formation, ischemic stroke, arteriovenous malformations, and neurodegenerative diseases.     

Developmental patterns of supercooling capacity in a subantarctic wingless fly

Anatalanta aptera is a wingless fly which lives in subantarctic islands, particularly in sea bird colonies. Developmental patterns of supercooling capacity were studied in an experimental population reared at 5°C and fed ad libitum. Mean supercooling points of the eggs, second and third instar larvae, pupae, teneral and mature adults were –28.0°C, –10.8°C, –8.8°C, 17.6°C, –16.6°C and –8.2°C respectively. Low mean supercooling points were found for inactive stages (eggs, pupae) and, unexpectedly among Diptera, teneral adults. Mature adults had a combination of low supercooling ability, high lipid content and physogastry. The results are compared with those obtained in winged species from other families of Diptera.     

Developmental physiological optics and visual acuity: A brief review

Summary The development of optical and neural factors affecting visual acuity is reviewed with the aim of determining the age at which the relationship between optical and neural factors become mature. Delayed development of extrastriate cortical and indirect visual pathways may account for differences in acuity assessed by preferential looking and pattern reversal VEPs.     

Developmental actions of natriuretic peptides in the brain and skeleton

The concept that atrial natriuretic peptide (ANP) and the closely related peptides BNP and CNP might be involved in the ontogeny of several organ systems emerged in the late 1980s. While many of the reported in vitro actions have not been examined in the context of organ development in vivo, recent studies demonstrate that mice which lack or overexpress natriuretic peptides or receptors exhibit pronounced skeletal growth defects. This article discusses how natriuretic peptides and other factors appear to regulate bone growth as an example of how natriuretic peptides might participate in the ontogeny of other organ systems. Evidence indicating that natriuretic peptides regulate neural development is then reviewed. Natriuretic peptides and receptors exhibit complex expression patterns in the developing nervous system, where they have been shown to act on neural cells as early as at the embryonic neural tube stage. Interestingly, both bone and brain growth appear to utilize primarily CNP and the CNP-specific type B receptor, and perhaps the type C receptor. In vitro data indicate that CNP may act on developing neurons, astrocytes and Schwann cells like a classical growth factor, regulating proliferation, patterning, phenotypic specification, survival and axonal pathfinding. Natriuretic peptides might also have roles in the vascularization of the embryonic brain, establishment of the blood-brain and blood-nerve barriers, and perhaps in nerve regeneration.Received 13 April 2004; received after revision 20 May 2004; accepted 27 May 2004     

Developmental physiological optics and visual acuity: a brief review

The development of optical and neural factors affecting visual acuity is reviewed with the aim of determining the age at which the relationship between optical and neural factors become mature. Delayed development of extrastriate cortical and indirect visual pathways may account for differences in acuity assessed by preferential looking and pattern reversal VEPs.     

Developmental characteristics of histamine methyltransferase and phenylethanolamine-N-methyltransferase of rat brain

Summary The specific activity of histamine methyltransferase of rat brain increases rapidly from the 16th until the 25th day of gestation (7 days after birth). The specific activity of phenylethanolamine-N-methyl-transferase shows a rapid incrase during the 1st and the 2nd week after birth, the adult values being obtained by the end of the 2nd week.     

Developmental homeostasis and heterozygosity for blood group loci in a human population

Summary Relationship between the variability of 5 independent morphological characters and the heterozygosity level at 4 blood group loci were determined in Israel. An increase in the heterozygosity level led to a reduction of the range and coefficient of variation of the morphological traits and also led to an increase of modal phenotype frequencies in the group.We are very grateful to Professor B. Arensburg of our department at the Tel Aviv University for his kind permission to use anthropometric data collected by him.     

Developmental G6PD polymorphism inDrosophila melanogaster: Evidence for non-structural variants

Summary G6PD isozyme variation inDrosophila melanogaster is investigated in the larval stage through electrophoretic and genetic analyses. As current structural models for this gene-enzyme system fail to apply in these laboratory populations, the authors suggest a regulatory hypothesis to explain their observations.