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Light and electron microscopic investigations on stellate cells in pars distalis of the adenohypophysis of ducks and geese.
The pars distalis of geese and ducks was investigated by light and electron microscopical methods to identify certain peculiarities of the stellate cells. Stellate cells were found in both cephalic and caudal lobes of the pars distalis in both sexes of geese and ducks. These cells were small in size and stained blue to violet by Performic-Acid, Alcian- blue (pH 0.2), PAS, Orange G stain. The stellate cells have numerous fine and long cytoplasmic processes which are linked together and with the pars distalis cells by cell junctions. Some of the stellate cells were arranged into folliclelike structure entirely surrounding an extra-cellular heterogenous substance. Particular emphasis was given to the ultrastructure peculiarities of the stellate cells which may be considered to exhibit secretory as well as phagocytic activities.
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[Electron microscopic study of rat tanicyte differentiation during the perinatal period].
The tanycyte differentiation during the perinatal period was studied by means of electron microscope in rats. From the 16th till the 18th day of prenatal period the wall of the 3rd ventricle is formed by intensively proliferating matrix cells with a narrow long apical process, oval perykarya and basal process. As the differentiation proceeds, the apical process shortens and disappears. The number of such cells increases gradually. At the same time the concentration of rough endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense, lamellated and multivesicular bodies increases. By the 3rd day the proliferative activity of cells decreases and they differ markedly in the ventral and ventrolateral parts of the infundibular recess and in the periphery of its broadened part. After the 5th day the ultrastructure of tanycytes and character of their distribution within the infundibular recess practically do not change, thus witnessing indirectly the completion of the main stages of differentiation of these cells.
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The filum terminale of the frog spinal cord. Light and electron microscopic observations.
The filum terminale, or terminal portion of the spinal cord, was studied in normal adult frogs (Rana pipiens) bu means of light and electron microscopy. Astroglial cells are the predominant elements in this region. The rostral portion of the filum terminale consists mainly of (1) a peripheral dense ring of myelinated and some unmyelinated nerve fibers, and processes of astrobytes terminating at the subpial space; (2) an intermediate zone, in which astrocytes are the main cellular elements in addition to a few degenerated neurons; and (3) a central region where the central canal is lined by dark and light ependymal cells. In the caudal portion of the filum terminale, the amount of neuropil is greatly reduced. This region os formed mainly by astrocytic glial cells and very few neuronal elements. The central canal in the caudal portion is located ventrally and contains a lining consisting almost exclusively of dark ependymal cells.
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The effects of adrenalectomy and cortisol treatment on cell types, other than corticotrophs, in the anterior pituitary of the mouse.
This investigation was designed to characterize changes due to adrenalectomy and cortisol treatment in cell types, other than corticotrophs, in the anterior pituitary of the mouse. Cortisol injections resulted in a reduced number of mammotrophs and an increased number of somatotrophs. By 5 days post-adrenalectomy an increase in the number of mammotrophs and a decrease in the number of somatotrophs was observed. No changes were noted in the number of gonadotrophs or thyrotrophs due to either adrenalectomy or cortisol treatment.
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Investigation on the pars tuberalis of the hypophysis of Psammodromus algirus L. (Sauria). An electron microscopy study.
The anatomic-microscopic and cytological aspects of the lateral lobes of adenohypophysis of Psammodromus algirus have been studied. Along the whole of its extension, the 'pars tuberalis' appears to be separated from the hypothalamic region by a space of 1600 A with a winding course filled with fibrillar matrix. The main inclusions of 'pars tuberalis' cells are glycogen granules histochemically characterized by the Thiery's method. A correlation between the electron and light microscopy observations on the lateral lobes of Psammodromus algirus is attempted.
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Ultrastructural changes in neurons and neuroglia of the avian telencephalon (hyperstriatum accessorium) following tri-ortho-cresyl-phosphate intoxication.
Ultrastructural reactions of neurons of the avian forebrain following tri-ortho-cresyl-phosphate (TOCP) poisoning are described. The neurons show a marked increase in the rough endoplasmic reticulum (RER), with RER specializations such as lamellar bodies and subsurface cisternae, as well as a proliferation of the Golgi complex and neurofilaments. In addition, an increase in the number of dense bodies and mitochondrial osmiophilia is noted. Similar changes can also be observed in the neuroglia. These alterations appear 10-13 days after TOCP ingestion.
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[Features of the development of the dendrites of differentiating pyriform cerebellar cortex neurons in mammals and man].
Pecularities of development of the differentiating piriform neuron cerebellum cortex dendrite system in the mammals and in man were studied with light and electron microscopy. Three consequent stages are involved in the process: the formation of a dilated portion of apical (supranuclear) cytoplasm with an increased amount of organelles; the formation of a temporary apical cytoplasmic mitre (cone); the development of the dendrite system occurring on the background of reduction of this temporary cytoplasmic formation. In the course of differentiation, a distinct change of the dendrite cytoplasm contents from reticular to tubular ones takes place.
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The pituitary cleft of the rat: an electron microscopic study.
The epithelium of the pituitary cleft and its colloid have been studied at the ultrastructural level in normal, adrenalectomized, castrated, dehydrated and lactating adult rats. Both control and experimental animals showed cells in different stages of degradation inside the cleft and mixed with the colloid. These exfoliated cells seems to have originated from the cleft's epithelium of the adjacent granular cells. In adrenalectomized and castrated rats the rostral epithelium of the cleft had large intercellular spaces that in some instances appeared to open directly into the cleft. Occasionally, the adenohypophysial canaliculi of the adrenalectomized rats were also seen connecting with the cleft. In lactating and castrated animals dark cells appeared more frequently in the rostral and caudal epithelium of the cleft. The results obtained suggest that the colloids is originated at least in part by involuted pituitary cells. There is also evidence that the follicular cavities of the Pars distalis and the cleft are continuous structures.
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Coordinated neural progenitor adaptations contribute to primate neocortical downscaling.
Most primates have a large, highly folded (gyrencephalic) neocortex, a feature present in the primate common ancestor. In contrast, several New World monkey species display a comparatively small and largely smooth, unfolded (lissencephalic) neocortex. One prominent example is the common marmoset, an increasingly popular model in neuroscience. This phenotype likely reflects an evolutionary reduction from the ancestral primate condition, implying modifications in neurodevelopmental programs. One essential basis for neocortical development is the activity and behavior of neural progenitor cells (NPCs). Here, we identify coordinated adaptations in NPC biology that bias neurodevelopmental trajectories toward neocortical downscaling. By combining marmoset and human cerebral organoids with analyses of fetal marmoset neocortical tissue and previously published histological data, we uncover multiple adaptations in apical and basal progenitors that converge on reduced progenitor capacity, alter early progenitor dynamics, and likely constrain neuronal output, thereby limiting the size and folding of the marmoset neocortex.
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CRISPR/Cas9-mediated heterozygous knockout of the autism gene CHD8 and characterization of its transcriptional networks in cerebral organoids derived from iPS cells.
BACKGROUND: CHD8 (chromodomain helicase DNA-binding protein 8), which codes for a member of the CHD family of ATP-dependent chromatin-remodeling factors, is one of the most commonly mutated genes in autism spectrum disorders (ASD) identified in exome-sequencing studies. Loss of function mutations in the gene have also been found in schizophrenia (SZ) and intellectual disabilities and influence cancer cell proliferation. We previously reported an RNA-seq analysis carried out on neural progenitor cells (NPCs) and monolayer neurons derived from induced pluripotent stem (iPS) cells that were heterozygous for CHD8 knockout (KO) alleles generated using CRISPR-Cas9 gene editing. A significant number of ASD and SZ candidate genes were among those that were differentially expressed in a comparison of heterozygous KO lines (CHD8+/-) vs isogenic controls (CHD8+/-), including the SZ and bipolar disorder (BD) candidate gene TCF4, which was markedly upregulated in CHD8+/- neuronal cells. METHODS: In the current study, RNA-seq was carried out on CHD8+/- and isogenic control (CHD8+/+) cerebral organoids, which are 3-dimensional structures derived from iPS cells that model the developing human telencephalon. RESULTS: TCF4 expression was, again, significantly upregulated. Pathway analysis carried out on differentially expressed genes (DEGs) revealed an enrichment of genes involved in neurogenesis, neuronal differentiation, forebrain development, Wnt/β-catenin signaling, and axonal guidance, similar to our previous study on NPCs and monolayer neurons. There was also significant overlap in our CHD8+/- DEGs with those found in a transcriptome analysis carried out by another group using cerebral organoids derived from a family with idiopathic ASD. Remarkably, the top DEG in our respective studies was the non-coding RNA DLX6-AS1, which was markedly upregulated in both studies; DLX6-AS1 regulates the expression of members of the DLX (distal-less homeobox) gene family. DLX1 was also upregulated in both studies. DLX genes code for transcription factors that play a key role in GABAergic interneuron differentiation. Significant overlap was also found in a transcriptome study carried out by another group using iPS cell-derived neurons from patients with BD, a condition characterized by dysregulated WNT/β-catenin signaling in a subgroup of affected individuals. CONCLUSIONS: Overall, the findings show that distinct ASD, SZ, and BD candidate genes converge on common molecular targets-an important consideration for developing novel therapeutics in genetically heterogeneous complex traits.