Archives d'anatomie microscopique et de morphologie experimentale最新文献

Spontaneous, transitory feminization of the left embryonic testis occurs in the majority of male Japanese quails from day 11 of incubation until the 2nd day after hatching. The feminized gonad is composed of a testicular part and of an ovarian-like cortical region, which develops outside the tunica albuginea. The cortical region contains numerous germ cells some of which enter meiosis on day 11 (i.e. at the time characteristic of female germ cells) and reach pachytene on day 14. Cortical regions are best developed on day 16 (day of hatching), but regression, accompanied by degeneration of many germ cells, begins shortly afterwards. The mechanism of feminization of the left embryonic testis is discussed.

During the morphogenesis of the adrenal gland of Triturus cristatus, a cranio-caudal differentiation is observed together with a migration of the two cell types composing the adrenal gland: the steroidogenic cells and the chromaffin cells. During the cranio-caudal differentiation the two cell type gradually occupy an increasingly posterior position on the mesonephros until they are distributed, in the adult, along the whole kidney. The migration brings the cells from dorsal or dorso-lateral position, with respect to the venous vessels, to the ventral surface of the kidney, an arrangement typical of the adult.

Psittacula psittacula when subjected to long term hypercalcemia by intramuscular injections of vitamin D2 (20,000 I.U.) on alternate days and by increasing dietary calcium, exhibit a rise in the serum calcium level after 10, 20 and 30 days of treatment as compared to their corresponding controls. The ultimobranchial cells show progressive hypertrophy up to 20th day of the treatment. From 20th day till the end of the experiment (30 days) these cells show feeble staining response. The parathyroid glands suffer from degenerative changes due to its inactivity under chronic hypercalcemia.

Tissue mechanically dissociated from blastocysts of the pig around the time of implantation were found to produce, in culture, free-floating multicellular spheroids (trophospheres) and adherent monolayer cells. Ultrastructurally the two cellular layers of the trophospheres were very similar to those of the blastocyst but the trophosphere outer layer characteristically contained very large mitochondria with a vastly expanded matrix and few cristae. Similar mitochondria were also found in the monolayer cells. Using a monoclonal antibody specific for pig trophectoderm, it was found that about 20% of the monolayer cells, and some of the spheroids expressed this trophectodermal antigen. In the latter case the antigen was present only on the surface facing the medium. The spheroids were fluid-filled and occasionally grew inside each other. The monolayer cells were predominantly uninuclear but did form a number of binucleate cells and in older cultures the occasional cell with many nuclei could be seen. The spheroids and the monolayer cells had similar glycoprotein profiles indicating that they were composed of similar cell populations. A glycoprotein of apparent molecular weight 68,000 observed in both spheres and monolayers may represent pig placental alkaline phosphatase. Both trophospheres and monolayer cells were observed to interconvert steroid precursors. It is apparent that the trophospheres share many features of the blastocyst and may thus represent a valuable model system similar to those described in other species for the investigation of their biochemical physiological and immunological properties.

The molecular mechanism of neural induction of embryonic cells is an important but poorly understood problem in neuroembryology. Glycoconjugates in the target cell plasma membrane and/or its structural organization play a key role in the reception of the inductive signal. It is the competent target tissue itself which probably contains the capacity and specificity for neuralization. However, the mechanism of transmission of the signal which leads to activation of the intracellular machinery involved in the process of neural determination remains to be elucidated. With respect to the information acquired by the target cells during neural induction, and the early events in differentiation, neuronal precursor cells have been shown to have acquired the potential to display a high degree of biochemical and phenotypic differentiation, even in the absence of further embryonic influences.

A 27 +/- 1 days old human embryo arising from an ectopic pregnancy was incubated with 3,4, L-dihydroxyphenylalanine (L-DOPA) to investigate whether cells of the gut primordium have at this early stage of development, the ability to take up the amine precursors. We could observe that a few cells exhibiting greenish fluorescence were located in the epithelium wall of the fore gut. Most of them were situated in contact with the basal lamina and possessed a long apical process extending over towards the gut lumen. The uptake of amine precursor, the morphology and the location of these cells strongly suggest that they represent the gut endocrine precursor cells of the human embryo.

In the adult palm squirrel, F. pennanti the pineal is a club shaped, elongated structure with a connective tissue capsule. It consists of various types of pinealocytes, glial cells, neurons, nerve fibres, blood vessels and connective tissue. Two types of pinealocytes could be identified by light microscopy. They are large rounded with centrally placed nucleus, and small rounded pinealocytes. They have medium sized processes stainable with Alcian blue, periodic acid Schiff and Nissl methods. The pinealocytes are not stainable with bromophenol blue. However, they are moderately stainable with PAS, Sudan black and Baker's acid hematin. Neurons are seen either singly or in groups with axonal processes. Cystic cavities often lined by cells are a normal feature of adult squirrel pineal, and the lining cells are both pinealocytes and glial cells. Often neuronal endings are seen terminating on these lining cells. PAS positive globules were also seen inside the cysts. In some squirrel pineals, fibrous cysts with an inner core of cells are also seen. Occasionally groups of lymphocytes were also encountered in the pineal. In the fetal pineal, the cells are both larger and smaller ones and arranged in a cortex and medulla pattern and no cystic cavities are seen. The third ventricle enters the base of the pineal as pineal recess.

The involvement of the pineal gland in the oestrous cycle seems to be clear nowadays according to various types of studies, although its exact functional mechanism remains unknown. The lack of morphological studies on the pineal gland throughout the oestrous cycle has drawn us into the quantification of the surface of pinealocyte nucleoli and nuclei and lipid contents (expressed in mean area of lipid droplets with respect to the total area of pinealocytes) in each of one of the four days of the oestrous cycle: Prooestrous, oestrous, metoestrous and dioestrous. The measures of nuclei and lipid droplets were taken on photographs that were obtained from 1 micron thick sections by means of an image analyzer and the measures of nucleoli were obtained from micrography by means a point-counting analysis. One-way analysis of variance showed significant differences among nucleolar surface during the four days of the cycle. Nucleolar surface in prooestrous and oestrous was significantly smaller than in metoestrous and dioestrous and nuclear surface showed higher values in dioestrous and proestrous than oestrous and metoestrous. The relative value of lipid surface with respect to pinealocyte surface showed significant differences between oestrous and the other three days, with their minimum value in oestrous and maximum in metoestrous. We conclude that the pinealocyte have a rhythmic activity during the oestrous cycle, with a minimum close to ovulation, where the pituitary gonadotropins and ovarian hormonal levels presents a surge.