Newly-formed neurons in the regenerating optic tectum of Triturus cristatus carnifex

A histochemical light and electron microscopy study of acetylcholinesterase (AChE) was carried out on the regenerating opic tectum of adult newt. A plug of optic tectum was removed and 15 days later [6-H3] thymidine was injected. Ninety days after the lesion the brain was removed, treated for histochemical AChE-detection and autoradiographic analysis. This double treatment showed the capacity of these adult amphibians to regenerate the nervous tissue through the proliferation of undifferentiated elements and their subsequent differentiation into neurons as is shown by the presence of cells both labelled by [6-H3] thymidine and by the AChE-reaction product.     

Opening of blood-brain barrier in Triturus cristatus carnifex by hyperosmolar mannitol solutions

The permeability of the newt cerebral capillaries to lanthanum ion has been studied after perfusion with mannitol solutions of increasing molarity. In the control specimens lanthanum deposits were limited to the luminal side of the capillaries and tracer did not spread to the pericapillary spaces due to the tight junctions. Treatment with hypertonic solutions of mannitol (0.25M, 0.5M, 1M) caused opening of the blood brain barrier with a progressive increase in lanthanum between the endothelial cell edges, in the basal lamina and in the extracellular spaces of the nervous parenchyma in relation to the molarity of the mannitol solution. The spread of lanthanum is probably due to opening of the tight junctions between the endothelial cells, since pinocytotic vesicles labelled with tracer were not evident.     

Cell proliferation in vivo and in vitro in visceral organs of the adult newt, Triturus cristatus carnifex

The mitotic and labelling incidence of intestine, liver, spleen and pancreas cells of Triturus cristatus carnifex adults kept at 15°C, 20°C, 25°C and 30°C were examined. Intestine mitotic and labelling incidences were highest at 25°C and lowest at 30°C. There was no significant difference between 15°C and 20°C. No such relationship could be shown for liver, spleen or pancreas, which had very much lower mitotic and labelling incidences. In culture, intestine mitotic and labelling incidences fell significantly within the first four hours, and maintained these low levels for the next five days. In contrast, liver mitotic and labelling incidences rose for 9–11 days, and then began to fall, while pancreas mitotic and labelling incidences reached peak values at day 5, and were kept in good condition for up to 14 days.     

Morphogenesis of the adrenal gland of Triturus cristatus carnifex during larval development and metamorphosis

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.     

In vitro conversion of testosterone-4-14C to androgens of the 5alpha-androstane series by a normal human ovary

In a previous communication (1) the identification of Δ⁴ -3-oxo-steroids and estrogens as metabolites of testosterone-4-¹⁴C incubated with normal post-ovulatory human ovaries was reported. Thin-layer chromatography of the extracts of those ovaries which contained no corpus luteum yielded zones of radioactivity which were not associated with any of these products. Detailed investigation of these zones from the extract of one of these glands resulted in identification of the following radiometabolites of the 5α-androstane series: 5α-androstane-3,17-dione, androsterone, 3β-hydroxy-5α-androstan-17-one, 17β-hydroxy-5α-androstan-3-one, 5α-androstane-3ga, 17β-diol and 5α-androstane-3β, 17β-diol. The capacity of a normal human ovary to produce these 5α-reduced androgens, especially the potent 17β-hydroxy-steroids, suggests a regulatory role of these compounds in ovarian function.     

In vitro incorporation of cholesterol-14C into very low density lipoprotein cholesteryl esters

The cholesteryl esters of very low density lipoproteins become labeled when human plasma is incubated with cholesterol-(14)C. The relative order of magnitude of the specific activity of the cholesteryl esters of the major lipoprotein fractions is: high density lipoproteins > very low density lipoproteins > low density lipoproteins. This pattern of labeling is similar to that found by others in experiments performed in vivo. Very low density lipoprotein cholesteryl esters are probably not formed by direct action of the plasma lecithin:cholesteryl acyltransferase, since significant esterification of cholesterol does not occur when very low density lipoproteins are incubated separately with the enzyme. Instead, labeled cholesteryl esters formed in the other lipoprotein fractions transfer to the very low density lipoproteins, the relative amount of monounsaturated esters transferred being slightly greater than that of saturated and polyunsaturated esters. The results support the possibility that the acyltransferase indirectly increases the concentration of very low density lipoprotein cholesteryl esters in vivo.     

Absence of chiasmata from the heteromorphic region of chromosome I during spermatogenesis in Triturus cristatus carnifex

Analysis of squash preparations of spermatocytes from crested newts, Triturus cristatus carnifex, has shown that in most cells at least one large bivalent regularly fails to form chiasmata in one arm-pair. Feulgen microphotometry of diplotene and metaphase bivalents has shown that it is the largest bivalent in each cell which shows chiasma failure in one arm-pair. A C-banding technique which identifies chromosome I by virtue of a long, darkly stained region in its long arm, was used to confirm the absence of chiasmata from one arm-pair of the longest bivalent, and specifically from the darkly stained region. The achiasmate region which chromosome I exhibits during spermatogenesis, corresponds to the heteromorphic region of oocyte lampbrush bivalent I in which chiasmata never form. A possible correlation between the complete absence of crossing-over from the heteromorphic region and unusual cytological and molecular features which it exhibits, are discussed.     

Placental transfer of cholesterol-4-14C into rabbit and guinea pig fetus

A tracer dose of cholesterol-4-(14)C was given daily in the diet of six pregnant guinea pigs to establish an isotopic steady state. At the time of parturition, maternal and fetal blood and fetal tissues were collected and analyzed for cholesterol content and cholesterol specific activity. A comparison of these specific activities in neonatal and maternal serum indicated that about 22% of the fetal serum cholesterol was transferred from maternal blood. In the newborn, tissues generally had the same cholesterol specific activity as serum. Brain tissue was an exception in having a specific activity only 8.4% of that of serum. Dietary cholesterol did not increase serum cholesterol levels in the newborn but did increase the percentage of fetal cholesterol derived from the maternal circulation. The rapid transfer of cholesterol-4-(14)C across the placenta was indicated by the appearance of this isotope in the newborn 2 days after its administration to pregnant rabbits. A considerable amount of the cholesterol content of newborn guinea pigs and rabbits originated from the maternal blood.     

Proliferative response of the mesencephalic matrix areas in the reparation of the optic tectum of Triturus cristatus carnifex

The localization and proliferative response of optic tectum matrix cells has been studied in adult newt following an experimental lesion on an optic lobe. The results show that 15 days after the lesion the cells in division, autoradiographically labelled, are located in the periventricular layer. Thirty days after the lesion the labelled cells are also found in the innermost grey layers; at 90 days the injured optic tectum regains the cytoarchitecture characteristic of this centre, with labelled cells, whether in the external or in the internal pyriform layers. In all the stages the labelled cells are also found in the periventricular layers of the controlateral optic tectum, in the dorsal pallium and in the striatum. The quantitative data exhibit the existence of a direct relationship between the number of proliferating cells in the injured optic lobe and the extent of the lesion. These data show the possibility of active cellular proliferation for the reconstruction of the lesioned nervous area and for restoration of the characteristic histological structure.