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Ken W S Ashwell

Publications and source records attributed to Ken W S Ashwell.

18 recordsLinked to original sources
PubMed2006

The hypothalamic supraoptic and paraventricular nuclei of the echidna and platypus.

The monotremes are an intriguing group of mammals that have major differences in their reproductive physiology and lactation from therian mammals. Monotreme young hatch from leathery skinned eggs and are nourished by milk secreted onto areolae rather than through nipples. Parturition and lactation are in part controlled through the paraventricular and supraoptic nuclei of the hypothalamus. We have used Nissl staining, enzyme histochemistry, immunohistochemistry for tyrosine hydroxylase, calbindin, oxytocin, neurophysin and non-phosphorylated neurofilament protein, and carbocyanine dye tracing techniques to examine the supraoptic and paraventricular nuclei and the course of the hypothalamo-neurohypophysial tract in two monotremes: the short-beaked echidna (Tachyglossus aculeatus) and the platypus (Ornithorhynchus anatinus). In both monotremes, the supraoptic nucleus consisted of loosely packed neurons, mainly in the retrochiasmatic position. In the echidna, the paraventricular nucleus was quite small, but had similar chemoarchitectural features to therians. In the platypus, the paraventricular nucleus was larger and appeared to be part of a stream of magnocellular neurons extending from the paraventricular nucleus to the retrochiasmatic supraoptic nucleus. Immunohistochemistry for non-phosphorylated neurofilament protein and carbocyanine dye tracing suggested that hypothalamo-neurohypophysial tract neurons in the echidna lie mainly in the retrochiasmatic supraoptic and lateral hypothalamic regions, but most neurophysin and oxytocin immunoreactive neurons in the echidna were found in the paraventricular, lateral hypothalamus and supraoptic nuclei and most oxytocinergic neurons in the platypus were distributed in a band from the paraventricular nucleus to the retrochiasmatic supraoptic nucleus. The small size of the supraoptic nucleus in the two monotremes might reflect functional aspects of monotreme lactation.

Acetylcholinesterase↗
PubMed2006

Development of the human nucleus of the solitary tract: a cyto- and chemoarchitectural study.

The present study investigated the prenatal development of the cyto- and chemoarchitecture of the human nucleus of the solitary tract from 9 to 35 weeks, by using Nissl staining and immunoreactivity to calbindin, calretinin, tyrosine hydroxylase and GAP-43. The nucleus began to gain heterogeneity and show different subnuclei as early as 13 weeks, and approached cytoarchitectural maturation from 21 to 25 weeks. The subnuclear division pattern observed in the fetal nucleus of the solitary tract at 25 weeks was very similar to that of the adult. Neurons immunoreactive to calbindin first appeared in the medial gastrointestinal area of the nucleus at 13 weeks, particularly within a putative gelatinosus subnucleus, while calretinin immunoreactivity during fetal life suggested the possible presence of a central subnucleus. Tyrosine hydroxylase immunoreactive neurons were seen in the medial subdivisions of the nucleus of the solitary tract as early as 13 weeks, but the population continued to increase until 25 weeks. Strong GAP-43 immunoreactivity was also present in the nucleus of the solitary tract at 13 weeks, especially in the dorsolateral and commissural subnuclei, while at 21 weeks there was a significant decline of GAP-43 expression. Results from the chemoarchitectural study showed that the human nucleus of the solitary tract expressed various neurochemical substances at an early developmental age (13 weeks), even before cellular and neuropil maturation was fully attained. Expression of these factors may play an important role in establishment and integration of viscerosensory function in the nucleus.

Aborted Fetus↗
PubMed2006

The anterior olfactory nucleus and piriform cortex of the echidna and platypus.

The cyto- and chemoarchitecture of the anterior olfactory nucleus and piriform cortex of the short-beaked echidna and platypus were studied to determine: (1) if these areas contain chemically distinct subdivisions, and (2) if the chemoarchitecture of those cortical olfactory regions differs from therians. Nissl and myelin staining were applied in conjunction with enzyme reactivity for NADPH diaphorase and acetylcholinesterase, and immunoreactivity for calcium-binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase. Golgi impregnations were also available for the echidna. In the echidna, the anterior olfactory nucleus is negligible in extent and merges at very rostral levels with a four-layered piriform cortex. Several rostrocaudally running subregions of the echidna piriform lobe could be identified on the basis of Nissl staining and calcium-binding protein immunoreactivity. Laminar-specific differences in calcium-binding protein immunoreactivity and NADPH-d-reactive neuron distribution were also noted. Neuron types identified in echidna piriform cortex included pyramidal neurons predominating in layers II and III and non-pyramidal neurons (e.g., multipolar profusely spiny and neurogliaform cells) in deeper layers. Horizontal cells were identified in both superficial and deep layers. By contrast, the platypus had a distinct anterior olfactory nucleus and a three-layered piriform cortex with no evidence of chemically distinct subregions within the piriform cortex. Volume of the paleocortex of the echidna was comparable to prosimians of similar body weight and, in absolute volume, exceeded that for eutherian insectivores such as T. ecaudatus and E. europaeus. The piriform cortex of the echidna shows evidence of regional differentiation, which in turn suggests highly specialized olfactory function.

Animals↗
PubMed2005

Chemoarchitecture of the monotreme olfactory bulb.

The cyto- and chemoarchitecture of the olfactory bulb of two monotremes (shortbeaked echidna and platypus) was studied to determine if there are any chemoarchitectural differences from therian mammals. Nissl staining in conjunction with enzyme reactivity for NADPH diaphorase, and immunoreactivity for calcium binding proteins (parvalbumin, calbindin and calretinin), neuropeptide Y, tyrosine hydroxylase and non-phosphorylated neurofilament protein (SMI-32 antibody) were applied to the echidna. Material from platypus bulb was Nissl stained, immunoreacted for calretinin, or stained for NADPH diaphorase. In contrast to eutherians, no immunoreactivity for either the SMI-32 antibody or calretinin was found in the mitral or dispersed tufted cells of the monotremes and very few parvalbumin or calbindin immunoreactive neurons were found in the bulb of the echidna. On the other hand, immunoreactivity for tyrosine hydroxylase in the echidna was similar in distribution to that seen in therians, and periglomerular and granule cells showed similar patterns of calretinin immunoreactivity to eutherians. Multipolar neuropeptide Y immunoreactive neurons were confined to the deep granule cell layer and underlying white matter of the echidna bulb and NADPH diaphorase reactivity was found in occasional granule cells, fusiform and multipolar cells of the inner plexiform and granule cell layers, as well as underlying white matter. Unlike eutherians, no NPY immunoreactive or NADPH diaphorase reactive neurons were seen in the glomerular layer. The bulb of the echidna was comparable in volume to prosimians of similar body weight, and its constituent layers were highly folded. In conclusion, the monotreme olfactory bulb does not show any significant chemoarchitectural dissimilarities from eutheria, despite differences in mitral/tufted cell distribution.

Animals↗
PubMed2005

Cyto- and chemoarchitecture of the monotreme olfactory tubercle.

This study was undertaken to determine whether the olfactory tubercles of two monotremes (platypus and echidna) showed cyto- or chemoarchitectural differences from the tubercles of therian mammals. Nissl staining was applied in conjunction with enzyme reactivity for NADPH diaphorase and acetylcholinesterase, and immunoreactivity for calcium binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase (echidna only). Golgi impregnations of the tubercle were also available for the echidna. The olfactory tubercle is a poorly laminated structure in the echidna, despite the pronounced development of other components of the echidna olfactory system, and the dense cell layer of the olfactory tubercle was found to be discontinuous and irregular. Granule cell clusters (islands of Calleja) were present, but were small, poorly defined and did not show the intense NADPH diaphorase activity seen in marsupial and placental mammals. A putative small island of Calleja magna was seen in only one echidna out of four. In Golgi impregnations of the echidna olfactory tubercle, the most abundant neuron type was a medium-sized densely spined neuron similar to that seen in the olfactory tubercle of some therians. Large spine-poor neurons were also seen in the polymorphic layer. In the platypus, the olfactory tubercle was very small but showed more pronounced lamination than the echidna, although no granule cell clusters were seen. In both monotremes, the development of the olfactory tubercle was poor relative to other components of the olfactory system (bulb and piriform cortex). The small olfactory tubercle region in the platypus is consistent with poor olfaction in that aquatic mammal, but the tubercle in the echidna is more like that of a microsmatic mammal than other placentals occupying a similar niche (e.g., insectivores).

Animals↗
PubMed2005

Cyto- and chemoarchitecture of the sensory trigeminal nuclei of the echidna, platypus and rat.

We have examined the cyto- and chemoarchitecture of the trigeminal nuclei of two monotremes using Nissl staining, enzyme reactivity for cytochrome oxidase, immunoreactivity for calcium binding proteins and non-phosphorylated neurofilament (SMI-32 antibody) and lectin histochemistry (Griffonia simplicifolia isolectin B4). The principal trigeminal nucleus and the oralis and interpolaris spinal trigeminal nuclei were substantially larger in the platypus than in either the echidna or rat, but the caudalis subnucleus was similar in size in both monotremes and the rat. The numerical density of Nissl stained neurons was higher in the principal, oralis and interpolaris nuclei of the platypus relative to the echidna, but similar to that in the rat. Neuropil immunoreactivity for parvalbumin was particularly intense in the principal trigeminal, oralis and interpolaris subnuclei of the platypus, but the numerical density of parvalbumin immunoreactive neurons was not particularly high in these nuclei of the platypus. Neuropil immunoreactivity for calbindin and calretinin was relatively weak in both monotremes, although calretinin immunoreactive somata made up a large proportion of neurons in the principal, oralis and interpolaris subnuclei of the echidna. Distribution of calretinin immunoreactivity and Griffonia simplicifolia B4 isolectin reactivity suggested that the caudalis subnucleus of the echidna does not have a clearly defined gelatinosus region. Our findings indicate that the trigeminal nuclei of the echidna do not appear to be highly specialized, but that the principal, oralis and interpolaris subnuclei of the platypus trigeminal complex are highly differentiated, presumably for processing of tactile and electrosensory information from the bill.

Animals↗
PubMed2005

Development of the human superior colliculus and the retinocollicular projection.

We have used carbocyanine dye tracing from the brachium of the superior colliculus in conjunction with Nissl staining and immunohistochemistry to GAP-43 and calretinin to study the development of retinal projections to the superior colliculus in 17 human embryos and fetuses aged from 8 to 28 weeks. Lamination of the superior colliculus begins to emerge by 11 weeks, and by 16 weeks all seven layers of the mature superior colliculus are visible. Fibres immunoreactive to GAP-43 were seen at 13 weeks in the most superficial layers. By 19 weeks, GAP-43 immunoreactivity was present in the stratum opticum as well as the deeper fibres layers, indicating the development of fibre pathways following those laminae. Carbocyanine dye tracing of retinocollicular projections showed extensive rostrocaudally running unbranched fibres in the superficial superior colliculus at 12 weeks. Shortly after this (13 weeks), retinocollicular fibres penetrate the deeper collicular layers and branching becomes apparent. We also saw occasional retrogradely labelled somata following DiI insertion into the superior brachium. Our findings indicate that development of the human superior colliculus and its connections is largely complete by 20 weeks. This would suggest that functional capacity of the human superior colliculus should also be mature by the middle of gestation.

Calbindin 2↗
PubMed2005

Cyto- and chemoarchitecture of the dorsal thalamus of the monotreme Tachyglossus aculeatus, the short beaked echidna.

We have examined the cyto- and chemoarchitecture of the dorsal thalamus of the short beaked echidna (Tachyglossus aculeatus), using Nissl and myelin staining, immunoreactivity for parvalbumin, calbindin, calretinin and non-phosphorylated neurofilament protein (SMI-32 antibody), and histochemistry for acetylcholinesterase and NADPH diaphorase. Immunohistochemical methods revealed many nuclear boundaries, which were difficult to discern with Nissl staining. Parvalbumin immunoreactive somata were concentrated in the ventral posterior, reticular, posterior, lateral and medial geniculate nuclei, while parvalbumin immunoreactivity of the neuropil was present throughout all but the midline nuclei. Large numbers of calbindin immunoreactive somata were also found within the midline thalamic nuclei, and thalamic sensory relay nuclei. Immunoreactivity for calretinin was found in many small somata within the lateral geniculate "a" nucleus, with other labelled somata found in the lateral geniculate "b" nucleus, ventral posterior medial and ventral posterior lateral nuclei. Immunoreactivity with the SMI-32 antibody was largely confined to somata and neuropil within the thalamocortical relay nuclei (ventral posterior medial and lateral nuclei, lateral and medial geniculate nuclei and the posterior thalamic nucleus). In broad terms there were many similarities between the thalamus of this monotreme and that of eutheria (e.g. disposition of somatosensory thalamus, complementarity of parvalbumin and calbindin immunoreactive structures), but there were some unique features of the thalamus of the echidna. These include the relatively small size of the thalamic reticular nucleus and the preponderance of calbindin immunoreactive neurons over parvalbumin immunoreactive neurons in the ventral posterior nucleus.

Acetylcholinesterase↗
PubMed2005

Cyto- and chemoarchitecture of the cerebral cortex of an echidna (Tachyglossus aculeatus). II. Laminar organization and synaptic density.

We have examined the distribution and morphology of neurons immunoreactive for nonphosphorylated neurofilament protein (SMI-32 antibody), calcium-binding proteins (parvalbumin, calbindin, calretinin), and neuropeptide Y as well as neurons reactive for NADPH diaphorase in the cerebral cortex of the Australian short-beaked echidna (Tachyglossus aculeatus). We have also studied synaptic morphology and density in S1 somatosensory cortex and assessed parameters associated with metabolic activity of the cerebral cortex (vessel volume density, mitochondrial volume density, and mitochondrial numerical density) in semi- and ultrathin sections. SMI-32 immunoreactivity was found mostly in layer V pyramidal neurons in selected cortical regions (S1, PV, V1, A). These neurons often showed atypical morphology compared with therian cortex. Neurons immunoreactive for calcium-binding proteins were broadly similar in both morphology and distribution to those seen in therian cortex, although calretinin-immunoreactive neurons were rare. Both Gray type I and Gray type II synapses could be identified in echidna S1 cortex and were similar to those seen in therian cortex. Peak synaptic density was in upper layer IV, followed by layer I, lower layer II, and upper layer III. Most synapses were of type I (72%), although types I and II were encountered with similar frequency in lower layer II and upper layer III. The capillary volume fraction values obtained for the echidna (from 1.18% in V1 to 1.34% in S1 cortex) fall within the values for rodent cortex. Similarly, values for mitochondrial volume fraction in echidna somatosensory cortex (4.68% +/- 1.76%) were comparable to those in eutherian cortex.

Animals↗
PubMed2005

Cyto- and chemoarchitecture of the amygdala of a monotreme, Tachyglossus aculeatus (the short-beaked echidna).

We have examined the cyto- and chemoarchitecture of the temporal and extended amygdala in the brain of a monotreme (the short-beaked echidna Tachyglossus aculeatus) using Nissl and myelin staining, enzyme histochemistry for acetylcholine esterase and NADPH diaphorase, immunohistochemistry for calcium binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase. While the broad subdivisions of the eutherian temporal amygdala were present in the echidna brain, there were some noticeable differences. No immunoreactivity for parvalbumin or calretinin for somata was found in the temporal amygdala of the echidna. The nucleus of the lateral olfactory tract could not be definitively identified and the medial nucleus of amygdala appeared to be very small in the echidna. Calbindin immunoreactive neurons were most frequently found in the ventrolateral part of the lateral nucleus, intraamygdaloid parts of the bed nucleus of the stria terminalis and the lateral part of the central nucleus. Neurons strongly reactive for NADPH diaphorase with filling of the dendritic tree were found mainly scattered through the cortical, central and lateral subnuclei, while neurons showing only somata reactivity for NADPH diaphorase were concentrated in the basomedial and basolateral subnuclei. Most of the components of the extended amygdala of eutherians could also be identified in the echidna. Volumetric analysis indicated that the temporal amygdala in both the platypus and echidna is small compared to the same structure in both insectivores and primates, with the central and medial components of the temporal amygdala being particularly small.

Acetylcholinesterase↗
PubMed2004

The claustrum is not missing from all monotreme brains.

Many authors have reported that the claustrum, which comprises the insular claustrum and the endopiriform nucleus, is missing from the monotreme forebrain. We used Nissl and myelin staining in conjunction with enzyme histochemistry for acetylcholinesterase and immunohistochemistry for parvalbumin, calbindin, calretinin and tyrosine hydroxylase to examine the brains of two monotremes, the short-beaked echidna (Tachyglossus aculeatus) and the platypus (Ornithorhynchus anatinus). We found that although the insular claustrum is a small structure in the echidna brain, it is nevertheless clearly present as loosely clustered neurons embedded in the white matter ventrolateral to the putamen and deep to the piriform and entorhinal cortices. Neurons in this region share the chemical features of the adjacent cortex (presence of a similar proportion of parvalbumin immunoreactive neurons and minimal activity for acetylcholinesterase and tyrosine hydroxylase), unlike the adjacent putamen and ventral pallidum. A putative endopiriform nucleus can be identified in the interior of the piriform lobe of the echidna as calretinin immunoreactive neurons embedded within the white matter. The situation is much less clear in the platypus, but our data suggest that there may be an insular claustrum deep to frontal cortex, separated from layer VI by only a thin layer of white matter. We could not identify an endopiriform nucleus in our platypus material. Our findings indicate that presence of the claustrum cannot be considered a feature confined to therian mammals and lend weight to arguments that this structure was present in the ancestral mammalian brain.

Acetylcholinesterase↗
PubMed2004

Cyto- and chemoarchitecture of the cerebral cortex of the Australian echidna (Tachyglossus aculeatus). I. Areal organization.

We have examined the topography of the cerebral cortex of the Australian echidna (Tachyglossus aculeatus), using Nissl and myelin staining, immunoreactivity for parvalbumin, calbindin, and nonphosphorylated neurofilament protein (SMI-32 antibody), and histochemistry for acetylcholinesterase (AChE) and NADPH diaphorase. Myelinated fibers terminating in layer IV of the cortex were abundant in the primary sensory cortical areas (areas S1, R, and PV of somatosensory cortex; primary visual cortex) as well as the frontal cortex. Parvalbumin immunoreactivity was particularly intense in the neuropil and somata of somatosensory regions (S1, R, and PV areas) but was poor in motor cortex. Immunoreactivity with the SMI-32 antibody was largely confined to a single sublayer of layer V pyramidal neurons in discrete subregions of the somatosensory, visual, and auditory cortices, as well as a large field in the frontal cortex (Fr1). Surprisingly, SMI-32 neurons were absent from the motor cortex. In AChE preparations, S1, R, V1, and A regions displayed intense reactivity in supragranular layers. Our findings indicate that there is substantial regional differentiation in the expanded frontal cortex of this monotreme. Although we agree with many of the boundaries identified by previous authors in this unusual mammal (Abbie [1940] J. Comp. Neurol. 72:429-467), we present an updated nomenclature for cortical areas that more accurately reflects findings from functional and chemoarchitectural studies.

Acetylcholinesterase↗
PubMed2004

Central vagal sensory and motor connections: human embryonic and fetal development.

The embryonic and fetal development of the nuclear components and pathways of vagal sensorimotor circuits in the human has been studied using Nissl staining and carbocyanine dye tracing techniques. Eight fetal brains ranging from 8 to 28 weeks of development had DiI (1,1'-dioctadecyl-3,3,3',3' tetramethylindocarbocyanine perchlorate) inserted into either the thoracic vagus nerve at the level of the sternal angle (two specimens of 8 and 9 weeks of gestation) or into vagal rootlets at the surface of the medulla (at all other ages), while a further five were used for study of cytoarchitectural development. The first central labeling resulting from peripheral application of DiI to the thoracic vagus nerve was seen at 8 weeks. By 9 weeks, labeled bipolar cells at the ventricular surface around the sulcus limitans (sl) were seen after DiI application to the thoracic vagus nerve. Subnuclear organization as revealed by both Nissl staining and carbocyanine dye tracing was found to be advanced at a relatively early fetal age, with afferent segregation in the medial Sol apparent at 13 weeks and subnuclear organization of efferent magnocellular divisions of dorsal motor nucleus of vagus nerve noticeable at the same stage. The results of the present study also confirm that vagal afferents are distributed to the dorsomedial subnuclei of the human nucleus of the solitary tract, with particular concentrations of afferent axons in the gelatinosus subnucleus. These vagal afferents appeared to have a restricted zone of termination from quite early in development (13 weeks) suggesting that there is no initial exuberance in the termination field of vagal afferents in the developing human nucleus of the solitary tract. On the other hand, the first suggestion of afferents invading 10N from the medial Sol was not seen until 20 weeks and was not well developed until 24 weeks, suggesting that direct monosynaptic connections between the sensory and effector components of the vagal sensorimotor complex do not develop until this age.

Carbocyanines↗
PubMed2003

Tactile sensory function in the forearm of the monotreme Tachyglossus aculeatus.

Peripheral tactile neural mechanisms in the forepaw of the echidna (Tachyglossus aculeatus, from the order Monotremata) were investigated to establish the extent of correspondence or divergence that has emerged over the widely different evolutionary paths taken by monotreme and placental mammals. Electrophysiological recordings were made in anesthetized echidnas from 29 single tactile sensory nerve fibers isolated in fine strands of the median or ulnar nerves of the forearm. Controlled tactile stimuli were applied to the forepaw glabrous skin to classify fibers, initially, into two broad divisions, according to their responses to static skin displacement. One displayed slowly adapting (SA) response properties, and the other showed a selective sensitivity to the dynamic components of the skin displacement. The SA class was made up of low-threshold SA fibers and other less sensitive SA fibers, and the purely dynamically sensitive tactile fibers could be subdivided according to vibrotactile sensitivity and receptive field characteristics into a rapidly adapting (RA) class, sensitive to low-frequency (< or =50-Hz) vibration, that resembled a corresponding RA class in placental species, and another class, sensitive to a broader range of vibrotactile frequencies (approximately 50-300 Hz), that may represent a monotreme equivalent of the Pacinian corpuscle (PC)-related fiber class of placental mammals. The differential tactile sensitivity of the three principal fiber classes and their individual coding characteristics, determined by quantitative stimulus-response analysis, indicate, first, that this triad of fiber classes can subserve high-acuity tactile signalling from the echidna footpad and, second, that peripheral tactile sensory mechanisms are highly conserved across evolutionarily divergent mammalian orders.

Afferent Pathways↗
PubMed2002

GAP-43 Immunoreactivity in the brain of the developing and adult wallaby ( Macropus eugenii).

We have examined the distribution of immunoreactivity for GAP-43 in the developing and adult brain of a diprotodontid metatherian, the tammar wallaby ( Macropus eugenii). The distribution of GAP-43 immunoreactivity in the neonatal wallaby brain was strikingly heterogeneous, in contrast to that reported for the newborn polyprotodontid opossum. Immunoreactivity for GAP-43 in the developing wallaby brain showed a caudal-to-rostral spatiotemporal gradient, with the brainstem well in advance of the telencephalon throughout the first 100 days of postnatal life. In many regions examined, GAP-43 immunoreactivity passed through the following phases: 1. intense immunoreactivity in developing fiber tracts and occasional somata; 2. diffuse homogeneous immunoreactivity; 3. selective loss of immunoreactivity in particular nuclei or cortical regions. In the isocortex, selective loss of GAP-43 immunoreactivity in the somatosensory and visual cortex (at postnatal day 115) coincided with the maturation of the laminar distribution of terminal thalamocortical axonal fields. Within adult cortical regions, GAP-43 immunoreactivity was highest in layer I of all regions, lower layers (V and VI) of primary somatosensory and visual cortices, layers II/III of motor and cingulate cortex, and layer IV of entorhinal cortex. Our findings suggest that, while patterning of GAP-43 immunoreactivity in the mature brain is similar across meta- and eutheria, there may be early developmental differences in the distribution of GAP-43 immunoreactivity between poly- and diprotodontid metatheria.

Animals↗
PubMed2002

Early development of the hypothalamus of a wallaby (Macropus eugenii).

We have studied the development of the hypothalamus of an Australian marsupial, the tammar wallaby (Macropus eugenii), to provide an initial anatomic framework for future research on the developing hypothalamus of diprotodontid metatheria. Cytoarchitectural (hematoxylin and eosin), immunohistochemical (CD 15 and growth associated protein, GAP-43), tritiated thymidine autoradiography, and carbocyanine dye tracing techniques were applied. Until 12 days after birth (P12), the developing hypothalamus consisted of mainly a ventricular germinal zone with a thin marginal layer, but by P25, most hypothalamic nuclei were well differentiated, indicating that the bulk of hypothalamic cytoarchitectural development occurs between P12 and P25. Strong CD 15 immunoreactivity was found in radial glial fibers in the rostral hypothalamus during early developmental ages, separating individual hypothalamic compartments. Immunoreactivity for GAP-43 was used to reveal developing fiber bundles. The medial forebrain bundle was apparent by P0, and the fornix appeared at P12. Tritiated thymidine autoradiography revealed lateral-to-medial and dorsal-to-ventral neurogenetic gradients similar to those seen in rodents. Dye tracing showed that projections to the posterior pituitary arose from the supraoptic nucleus at P5 and from the paraventricular nucleus at P10. Projections to the medulla were first found from the lateral hypothalamic area at P0 and paraventricular nucleus at P10. In conclusion, the pattern of development of the wallaby hypothalamus is broadly similar to that found in eutheria, with comparable neurogenetic compartments to those identified in rodents. Because most hypothalamic maturation takes place after birth, wallabies provide a useful model for experimentally manipulating the developing mammalian hypothalamus.

Animals↗
PubMed2002

Organization of human hypothalamus in fetal development.

The organization of the human hypothalamus was studied in 33 brains aged from 9 weeks of gestation (w.g.) to newborn, using immunohistochemistry for parvalbumin, calbindin, calretinin, neuropeptide Y, neurophysin, growth-associated protein (GAP)-43, synaptophysin, and the glycoconjugate 3-fucosyl- N-acetyl-lactosamine. Developmental stages are described in relation to obstetric trimesters. The first trimester (morphogenetic periods 9-10 w.g. and 11-14 w.g.) is characterized by differentiating structures of the lateral hypothalamic zone, which give rise to the lateral hypothalamus (LH) and posterior hypothalamus. The PeF differentiates at 18 w.g. from LH neurons, which remain anchored in the perifornical position, whereas most of the LH cells are displaced laterally. A transient supramamillary nucleus was apparent at 14 w.g. but not after 16 w.g. As the ventromedial nucleus differentiated at 13-16 w.g., three principal parts, the ventrolateral part, the dorsomedial part, and the shell, were revealed by distribution of calbindin, calretinin, and GAP43 immunoreactivity. The second trimester (morphogenetic periods 15-17 w.g., 18-23 w.g., and 24-33 w.g.) is characterized by differentiation of the hypothalamic core, in which calbindin- positive neurons revealed the medial preoptic nucleus at 16 w.g. abutted laterally by the intermediate nucleus. The dorsomedial nucleus was clearly defined at 10 w.g. and consisted of compact and diffuse parts, an organization that was lost after 15 w.g. Differentiation of the medial mamillary body into lateral and medial was seen at 13-16 w.g. Late second trimester was marked by differentiation of periventricular zone structures, including suprachiasmatic, arcuate, and paraventricular nuclei. The subnuclear differentiation of these nuclei extends into the third trimester. The use of chemoarchitecture in the human fetus permitted the identification of interspecies nuclei homologies, which otherwise remain concealed in the cytoarchitecture.

Biomarkers↗