PubMed Health⌕ Search

Biomedical subjects

J Calvo

Publications and source records attributed to J Calvo.

At least 91 records · Page 5Linked to original sources
PubMed1979

Development of the innervation in the chicken pineal gland (Gallus gallus).

The innervation of the pineal gland has been studied during the embryonic development and the first 10 days after hatching. On day 17 of embryonic development, the first nerve fibers are observed in the pineal capsule. They appear at the stalk level and rise to locate mostly on the anterior side of the capsule. Some nerve fibers leave these nerve bundles to penetrate the gland and they situate in the connective septa (18 days of development). From day 19 of development onwards, nerve fibers locate only in the parafollicular layer. Cells that may be identified as neurons are found in the pineal parenchyma.

Animals↗
PubMed1979

Evolution and nature of the dense bodies in the chicken pinealocytes.

The acid phosphatase reaction, applied to light and electron microscopy, was studied in the chicken pineal gland from the moment of hatching until 2 months of age. From the moment of hatching there is a great amount of acid phosphatase, which is mainly found in the vicinity of the lumen of both the recess and large follicles. Acid phosphatase is poor in the parafollicular layer. From day 30 onwards, there is an obvious fragmentation of the recess and of large follicles. Also, the parafollicular layer differentiates to form new follicles. The dense polymorphous bodies of the B pinealocytes are ultrastructurally identified as lysosomes.

Acid Phosphatase↗
PubMed1979

Evolution of the pineal gland in the adult chicken.

The structural pattern of the pineal gland in the hen corresponds to a more advanced stage of the evolution which began in an early period of the animal's life. This evolution corresponds mainly to the transformation of the large follicular cavities into cellular 'rosettes'. The parafollicular layer disappears from the rosette wall which thus remains with only one row of cells (A and B pinealocytes). The cellular hypertrophy and the great development of the pinealocyte organelles in the adult pineal gland makes us think of this gland as a functionally active organ. This functional activity must have remained during the entire period of the time studied (1--5 years), due to the ultrastructural uniformity found and due to the fact that we could not observe any type of degenerative process in the gland.

Acid Phosphatase↗
PubMed1979

The origin of microglial cells.

The rat brain has been studied between 6 hours after birth and 100 days, using histochemical techniques for acid phosphatase and peroxidase, and silver impregnation for microglial cells. The results indicate that microglia come initially from acid phosphatase-positive cells of the meninges. These invade the nervous parenchyma and transform into ramified microglia. At 3 days of age similar cells are present on the outer surface of the large blood vessels, from which site they migrate into the nervous parenchyma. In 100 days old rats the acid phosphatase-positive cells are practically all pericytes. None of the microglial cells or their precursors give a positive reaction for peroxidase.

Acid Phosphatase↗
PubMed1978

Post-hatching evolution of the pineal gland of the chicken.

The authors studied the evolution of the pineal gland of the chicken (Gallus gallus) from hatching until 34 months of age. They describe the progressive decrease of the follicular cavities and the appearance of solid-looking cavities. The stroma increases with age, dividing the pineal parenchyma into territories of small caliber.

Age Factors↗
PubMed1978

Embryonic development of the pineal gland of the chicken (Gallus gallus).

A study of the embryonic development of the pineal gland of the chicken was performed with the optical microscope. The time of apparition of the first outline, as a derivative of the roof of the third ventricle, was fixed at 3 days. The major portion of the pineal parenchyma is derived from the frontal wall of the outline. All the vesicles and follicles were formed by solid mammilliform projections which subsequently presented a central lumen. In no case was a communication of the follicular cavities with the pineal recess observed. Three categories of vesicles or follicles can be distinguished according to their origin.

Animals↗
PubMed1977

[Pediatric intensive care (author's transl)].

In the Intensive Care Unit of our General Hospital, where an important obstetric-pediatric unit exists, 392 infants have been treated from August 1974 to 1976. Although the results of all age groups are shown, the neonatal one is specially considered. All those patients who recovered and were discharged from the hospital were called for revision and the results of those whom attended are shown. The convinience of the regionalisation and hierarchisation of these intensive care units and the necessity of adequately organise the communication and transport of these patients from the peripheral small units to the regional one, is emphasized.

Critical Care↗
PubMed1966

Expression of the leucine operon.

Burns, R. O. (Cold Spring Harbor Laboratories of Quantitative Biology, Cold Spring Harbor, N.Y.), J. Calvo, P. Margolin, and H. E. Umbarger. Expression of the leucine operon. J. Bacteriol. 91:1570-1576. 1966.-The four genes which specify the structure of the three enzymes specifically involved in the biosynthesis of leucine in Salmonella typhimurium constitute a single operon. Three types of control mutants have been delineated on the basis of their location on the Salmonella chromosome and the manner in which they coordinately affect the rates of synthesis of the pertinent enzymes. The three types of mutants correspond to operator-negative, operator-constitutive, and regulator-negative. The rate of synthesis of the enzymes can also be altered by varying the amount of leucine made available to the cell. Leucine can be effectively limited by limiting the supply of alpha-ketoisovalerate, but in doing so two of the three enzymes, alpha-isopropylmalate synthetase and isopropylmalate isomerase, are labilized. This observation was correlated with an in vivo diminution of the levels of the substrates of these enzymes and the fact that alpha-ketoisovalerate and alpha-isoporpylmalate protect the respective enzymes against thermal inactivation in vitro. The functional association of the structural genes is also illustrated by the presence of polarity mutations; that is, certain structural gene mutations lower the rates of synthesis of the enzymes specified by genes located distally to the mutated gene and the operator segment of the operon.

Genes↗