- Email: [email protected]
Mathematical models of the pubertal process
1420
B14
BIS
MATHEMATICAL MODELS OF THE PUBERTAL PROCESS. W. R. Smith, Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario, NlG 2W1, Canada, A general framework is presented and discussed for mathematical models of the reproductive endocrine system, which is based on systems of nonlinear differential equations. These models attempt to describe the time course of serum concentrations of the principal hormones affecting the system - luteinizing hormone releasing hormone, luteinizing hormone, The framework is and estradiolcfor females) or testosterone(for males). illustrated by some specific models, and the relevance of these to the underlying biological phenomena is explored. An important feature of the the models is their attempt to understand certain qualitative aspects of An example and their evolution over time. reproductive endocrine system, release associated a feature is the onset of episodic hormonal of such It is argued that this may occur as a result of the gradual with puberty. system of the inter-relationships among the the strengths change of specific than as a result of a sudden change in one components, rather associated with the system as a whole This type of phenomenon, component. is called an “emergent property” rather than with an isolated part of it, The likely importance of such properties in the of the system. as well as in other biological systems, is reproductive endocrfne system, stressed. S. Wray and G.E. POSTNATAL MATURATION OF THE LHRH SYSTEiM.
Hoffman-Small*, Department of Anatomy, University of Rochester Schoom Medicine and Dentistry, Rochester, NY 14642, USA. The luteinizing hormone releasing hormone ILHRH) system plays an integral role in the CNS regulation of reproduction, including puberty. To determine if changes in the LHRH system correlate with reproductive maturation, an immunocytochemlcal study of the postnatal development of the LHRH system was performed in male and female rats. LHRH cells were present in a V-shaped field whose apex lay in the preoptic/septal area and whose sides extended caudally to the ventrolateral anterior hypothalamus. LHRH fibers extended to the median eminence, organum vasculosum of the lamina terminalis, as well as a number of The LHRH distributional patterns did not change with age and other brain areas. were identical in male and female animals. Total LHRH cell number was 1380 + 35 (S&M,) and likewise showed no significant changes in male or female animal; during maturation even after colchicine pretreatment. in examining the LHRH cells, two cell types were characterized: a) bipolar cells with smooth, aspinous contours on both the soma and dendrites, and b) smaller irregular cells with spinelike processes on the dendrites and/or soma. In the prepubertal animal, LHRH neurons were predominantly classified as smooth cells. Between 26-32 days of age, i.e. just prior to the onset of puberty m the rat, a striking shift in the ratio of the two cell types was noted: the percent of ceils increased. The morphological changes in the LHRH ceils followed a time course similar to gonadal and behavioral maturation. The shift in the LHRH cell morphology toward spiny cells suggests that changes in the afferent input to the LHRH are among the triggers of the pubertal process. Supported by USPHS grant NS 13725 and MH 08838. SYNAPTIC CORRELATES OF MATURATION OF THE NEUROI?NDOCRINE HYPOTHALAMUS: ,'OSSIBLE IMPLICATION FOR ONSET MECHANISTS OF PUBERTY. A. Matsumoto', ~--Department of Anatomy, Juntendo Unrverslty School of Medrclne, Hongo,
Tokyo 113, Japan B16
Semi-yuantltatlve studies on the synaptic structures in the arcuate nucleus (ARCN) and ventromedial nucleus (VMN) in female rats during postnatal development were perf'ormed by counting the number of synapses. The neuropli of the ARCN and VMN In neonatal females was in an rmmature state characterlzed by the presence of extracellular space and a paucity of syn:pses. The number of synapses in the VMN increased with age and reached a plateau by the prepubertal period. The extracellular space observed at neonatal period was fully occupied by axons, their terminals, dendrites and gllal processes. On the other hand, the maturation of the neuropll of the ARCN was delayed, compared to the VMN. The number of synapses I" the ARCN increased up to puberty. These results suggest that the maJor neural CLI‘cults drlvlng postpubertal neuroendocrlne functions are not yet established at early postnatal period. Evidence IS accumulating that estrogen plays a srgnlflcant role rn modulating postnatal neuronal maturation and clrcult formation. Furthermore, acceleration of synaptogenesis In the ARCN occurred concurrently with precocious ovulation in Immature females followlng a Single lnjectlon of pregnant mal-e serum gonadotropin. These results may provide morphoioglcal evidence suggesting that the maturation of negative and posltrve feedback systems for gonadotropin regulatlon 1s closely associated with the maturation of the hardwares of neuroendocrine hypothalamus. The establishment of' new crrcults ln the hypethalamus during peripubertal period mdy be related to the onset of puberty.
B14
BIS
MATHEMATICAL MODELS OF THE PUBERTAL PROCESS. W. R. Smith, Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario, NlG 2W1, Canada, A general framework is presented and discussed for mathematical models of the reproductive endocrine system, which is based on systems of nonlinear differential equations. These models attempt to describe the time course of serum concentrations of the principal hormones affecting the system - luteinizing hormone releasing hormone, luteinizing hormone, The framework is and estradiolcfor females) or testosterone(for males). illustrated by some specific models, and the relevance of these to the underlying biological phenomena is explored. An important feature of the the models is their attempt to understand certain qualitative aspects of An example and their evolution over time. reproductive endocrine system, release associated a feature is the onset of episodic hormonal of such It is argued that this may occur as a result of the gradual with puberty. system of the inter-relationships among the the strengths change of specific than as a result of a sudden change in one components, rather associated with the system as a whole This type of phenomenon, component. is called an “emergent property” rather than with an isolated part of it, The likely importance of such properties in the of the system. as well as in other biological systems, is reproductive endocrfne system, stressed. S. Wray and G.E. POSTNATAL MATURATION OF THE LHRH SYSTEiM.
Hoffman-Small*, Department of Anatomy, University of Rochester Schoom Medicine and Dentistry, Rochester, NY 14642, USA. The luteinizing hormone releasing hormone ILHRH) system plays an integral role in the CNS regulation of reproduction, including puberty. To determine if changes in the LHRH system correlate with reproductive maturation, an immunocytochemlcal study of the postnatal development of the LHRH system was performed in male and female rats. LHRH cells were present in a V-shaped field whose apex lay in the preoptic/septal area and whose sides extended caudally to the ventrolateral anterior hypothalamus. LHRH fibers extended to the median eminence, organum vasculosum of the lamina terminalis, as well as a number of The LHRH distributional patterns did not change with age and other brain areas. were identical in male and female animals. Total LHRH cell number was 1380 + 35 (S&M,) and likewise showed no significant changes in male or female animal; during maturation even after colchicine pretreatment. in examining the LHRH cells, two cell types were characterized: a) bipolar cells with smooth, aspinous contours on both the soma and dendrites, and b) smaller irregular cells with spinelike processes on the dendrites and/or soma. In the prepubertal animal, LHRH neurons were predominantly classified as smooth cells. Between 26-32 days of age, i.e. just prior to the onset of puberty m the rat, a striking shift in the ratio of the two cell types was noted: the percent of ceils increased. The morphological changes in the LHRH ceils followed a time course similar to gonadal and behavioral maturation. The shift in the LHRH cell morphology toward spiny cells suggests that changes in the afferent input to the LHRH are among the triggers of the pubertal process. Supported by USPHS grant NS 13725 and MH 08838. SYNAPTIC CORRELATES OF MATURATION OF THE NEUROI?NDOCRINE HYPOTHALAMUS: ,'OSSIBLE IMPLICATION FOR ONSET MECHANISTS OF PUBERTY. A. Matsumoto', ~--Department of Anatomy, Juntendo Unrverslty School of Medrclne, Hongo,
Tokyo 113, Japan B16
Semi-yuantltatlve studies on the synaptic structures in the arcuate nucleus (ARCN) and ventromedial nucleus (VMN) in female rats during postnatal development were perf'ormed by counting the number of synapses. The neuropli of the ARCN and VMN In neonatal females was in an rmmature state characterlzed by the presence of extracellular space and a paucity of syn:pses. The number of synapses in the VMN increased with age and reached a plateau by the prepubertal period. The extracellular space observed at neonatal period was fully occupied by axons, their terminals, dendrites and gllal processes. On the other hand, the maturation of the neuropll of the ARCN was delayed, compared to the VMN. The number of synapses I" the ARCN increased up to puberty. These results suggest that the maJor neural CLI‘cults drlvlng postpubertal neuroendocrlne functions are not yet established at early postnatal period. Evidence IS accumulating that estrogen plays a srgnlflcant role rn modulating postnatal neuronal maturation and clrcult formation. Furthermore, acceleration of synaptogenesis In the ARCN occurred concurrently with precocious ovulation in Immature females followlng a Single lnjectlon of pregnant mal-e serum gonadotropin. These results may provide morphoioglcal evidence suggesting that the maturation of negative and posltrve feedback systems for gonadotropin regulatlon 1s closely associated with the maturation of the hardwares of neuroendocrine hypothalamus. The establishment of' new crrcults ln the hypethalamus during peripubertal period mdy be related to the onset of puberty.