scholarly journals Memoirs: Some Observations on the Hypophysis of Petromyzon and of Amia

1923 ◽  
Vol s2-67 (266) ◽  
pp. 257-292
Author(s):  
G. R. DE BEER

1. The hypophysis of Petromyzon arises as a solid ingrowth. 2. The depression in which the hypophysis and olfactory organs come to lie is formed by the great expansion of the upper lip in conjunction with the sides of the anterior surface of the head. 3. The beginning of the histological differentiation of the glandular elements takes place from a solid strand before the appearance of any cavity. 4. The hypophysial cavity arises late as a split in the thickness of the hypophysis, and afterwards extends in both directions communicating forwards with the external depression. 5. The homologue of the pars tuberalis is probably to be found in the ‘Uebergangsteil’ of Stendell, a chromophobe portion situated between the pars anterior and pars intermedia. 6. The hypophysis of Amia is derived from the ectoderm, thus agreeing with all other known forms. 7. It arises outside the stomodaeum on the anterior surface of the head. 8. It is a solid ingrowth which loses all connexion with its point of origin, and within which the hypophysial cavity makes its appearance at a later stage. 9. Outside and in front of the stomodaeum is probably the primitive position of origin of the hypophysis, without connexion with either mouth or nose. 10. In Selachians and Amniotes where the fore-brain is early very large and the cranial flexure pronounced, the hypophysis arises further posteriorly and so is included in the hollow of the stomodaeum. 11. Although probably primitively hollow, the rudiment of the hypophysis is often solid. Such diversity is brought about by embryonic developmental conditions, perhaps the distance separating the rudiment from the infundibulum.

Author(s):  
Eva Horvath ◽  
Kalman Kovacs

The human pituitary gland consists of two major components: the adenohypophysis comprising the hormone producing cells of the pars anterior, pars intermedia, and pars tuberalis, and the neurohypophysis, also called pars nervosa or posterior lobe (1). In contrast to most mammalian species, the human gland has no anatomically distinct pars intermedia (2). The exclusively proopiomelanocortin (POMC)-producing cells of the pars intermedia are sandwiched between the anterior and posterior lobes in the majority of mammals, whereas in the human they are incorporated within the pars anterior, thereby constituting the pars distalis (3). The pars tuberalis is a minor upward extension of the adenohypophysis attached to the exterior of the lower pituitary stalk. In this chapter we deal only with adenohypophyseal tumours. Histologically, the adenohypophysis consists of a central median (or mucoid) wedge flanked by the two lateral wings. The hormone-producing cell types are distributed in an uneven, but characteristic manner. The cells are arranged within evenly sized acini surrounded by a delicate but well-defined reticulin fibre network giving the pituitary its distinct architecture (4). In the center of the acini is the long-neglected pituitary follicle composed of the agranular nonendocrine folliculo-stellate cells (5).


1936 ◽  
Vol s2-78 (312) ◽  
pp. 637-651
Author(s):  
N. H. HOWES

1. The structure of the pituitary of the adult skate is described. 2. This gland shows two distinct regions of growth which can be correlated with increase of size of the animal. 3. The pars anterior can be subdivided into three regions differing by the staining reactions of their constituent cells: (a) an anterior region where deep-purple chromaphil cells are found; (b) a middle, where they are faintly basiphil; and (c) a posterior, where they are mainly acidophil. 4. It is suggested that these regions are homologous with the pars tuberalis, basiphil, and oxyphil areas respectively of the pars anterior of the mammalian pituitary. 5. The oxyphil cells show an iodine-leucobase reaction similar to that given by the oxyphil cells of the ox pituitary. 6. The ventral lobe is a completely separate structure from the pars intermedia, although it may run along the ventral surface of the latter for some distance. 7. The histology of the neuro-intermediate lobe is described.


1967 ◽  
Vol 39 (3) ◽  
pp. 351-359 ◽  
Author(s):  
A. HOWE ◽  
A. J. THODY

SUMMARY The adenohypophysis of the pig was examined histochemically for the presence of 11 oxidative enzymes, namely: 1.1.1.27 l-lactate: NAD oxidoreductase, 1.1.1.30 d-3-hydroxybutyrate: NAD oxidoreductase, 1.1.1.37 l-malate: NAD oxidoreductase, 1.1.1.41 threo-ds-isocitrate: NAD oxidoreductase (decarboxylating), 1.1.1.42 threo-ds-isocitrate: NADP oxidoreductase (decarboxylating), 1.1.1.49 d-glucose-6-phosphate: NADP oxidoreductase, 1.1.99.5 l-glycerol-3-phosphate: (acceptor) oxidoreductase, 1.3.99.1 succinate: (acceptor) oxidoreductase, 1.4.1.2 l-glutamate: NAD oxidoreductase (deaminating), 1.6.99.1 reduced-NADP: (acceptor) oxidoreductase, 1.6.99.3 reduced-NAD: (acceptor) oxidoreductase. With the exception of 1.1.1.30 d-3-hydroxybutyrate: NAD oxidoreductase, activity was found throughout the adenohypophysis for all these enzymes. A comparison was made with the activity for these enzymes in liver. In the adenohypophysis, the pars tuberalis exhibited the highest activity for all enzymes, generally equal to or greater than that shown by the liver. The pars intermedia and the pars anterior showed similar activity for these enzymes, in general of a lower order than that given by the liver. The pattern of enzyme distribution in the pars intermedia is described; high activity for 1.1.1.37 l-malate: NAD oxidoreductase, 1.1.1.27 l-lactate: NAD oxidoreductase, 1.6.99.3 reduced-NAD: (acceptor) oxidoreductase, 1.6.99.1 reduced-NADP: (acceptor) oxidoreductase was shown by cells lining cysts and the pituitary cleft. The findings are discussed in relation to the possible association of these enzymes with secretory function.


In a previous contribution (Hogben and Slome, 1931) evidence was brought forward to show that the white background response does not depend on the same mechanism of coordination as the black background response, which is produced by reflex liberation of a hormone (“B” substance) of the pars intermedia in the pituitary gland; and experiments pointing to the existence of another internal secretion (“W” substance), connected directly or indirectly with the activity of the pars tuberalis, were described. The existence of separate receptor components of the retina controlling the two systems was left for subsequent enquiry. Of two possible hypotheses concerning the nature of the receptive mechanism, the most likely one is illustrated diagrammatically in fig. 1. In normal situations, when an animal is illuminated on a black background, light can only fall on the floor of the retina. If it is aquatic, the maximum divergence of any two rays which strike the eye is twice the critical angle for air and water, so that in the absence of reflexion of rays from sur­rounding objects below the surface of separation all rays will presumably be brought to a sharp focus in shallow water. There are thus three distinct possibilities which arise from the way in which the animal is illuminated if, as in Xenopus , the eyes are situated on the top of the head: ( a ) in darkness no part of the retina is stimulated, the same being true of the eyeless animal; ( b ) when the animal is exposed to a black background only a sharply localized region of the retina is stimulated; ( c ) when the animal is exposed to a white background the whole of the retina is illuminated owing to the scattering of rays in all directions from the surroundings. For convenience of description the usual black back­ground situation will be described hereafter as one in which only the “floor” of the retina is stimulated, and the white background situation as one in which the floor and the “ periphery ” of the retina are both stimulated together. If then, the receptor elements of the floor and periphery initiate different systems of reflex arcs the phenomena of the background response in Amphibia and Reptiles may be interpreted as follows. In Reptiles we may suppose that stimulation of floor reflexly excites the melanophores to expand, while stimulation of peripheral photoreceptors excites them to contract, being presumably prepotent in the final common path. In Amphibia two alternatives may be con­sidered: ( a ) that floor elements reflexly excite liberation of “B” and that peripheral photoreceptors, being prepotent, reflexly inhibit libera­tion of “B"; ( b ) that floor elements reflexly excite liberation of “B”, and peripheral photoreceptors reflexly excite production of the antago­nistic substance “W” in quantity sufficient to over-ride the effect of “B”. The crucial test of the truth of the general hypothesis that the floor and peripheral elements of the retina initiate different processes of coordina­tion was suggested by Keeble and Gamble (1904-6) in their experiments on Crustacea. If it is true, a normal animal illuminated from below in a black tank with a white top should react in exactly the same way as a normal animal when illuminated in a black tank from above. On the other hand, a normal animal illuminated from below in a black tank with a black top should react like an eyeless animal in the same situation, because the floor elements would not be subject to stimulation. The experiment may be varied as indicated below. In order to obtain signi­ficant results two classes of precautions must be carefully observed. One is that the physical dimensions of the tank must not exceed certain limits, since the maximal divergence of two rays is rigidly fixed when an animal is illuminated from above. The other is that there must be no air-water interface to permit reflexion of the incident rays downwards. Aside from the fact that no bubbles must be allowed to collect, this condition presents a practical difficulty if the animal has to come to the surface to breathe.


1965 ◽  
Vol 31 (3) ◽  
pp. 279-287 ◽  
Author(s):  
B. A. YOUNG ◽  
C. L. FOSTER ◽  
E. CAMERON

SUMMARY The ultrastructure of the adenohypophysis of the rabbit is described preliminary to reporting changes after experimental procedures. Fixation by perfusing with gluteraldehyde enabled selected regions of the gland to be removed with accuracy. Separate descriptions of the pars distalis proper, zona tuberalis, pars tuberalis and pars intermedia are therefore included. In the pars distalis proper four types of granular cell were recognized although their function cannot be accurately determined. For convenience, therefore, they have been designated 1, 2, 3 and 4. In addition a fifth type of cell (type 5) is described which is also present in the other areas. This cell, as well as having possible phagocytic functions, appears to be concerned in the formation of a perivascular channel. Two types of cell are recognized in the zona tuberalis, which are similar in appearance to the 3 and 4 cells of the pars distalis, although not necessarily identical in function. The characteristic cells of the pars tuberalis are rich in cytoplasmic RNA and contain large numbers of intracellular fibrils. It is suggested that the ribosomes are concerned in the synthesis of a sedentary protein which may take the form of the microfibrils. The pars intermedia contains a predominant cell type with large granules of varying density. The relationship of these granules to the specific hormone is discussed.


1933 ◽  
Vol 10 (2) ◽  
pp. 186-195
Author(s):  
H. A. SHAPIRO ◽  
H. ZWARENSTEIN

1. A new micro-method for the estimation of serum calcium requiring only 0.4 C.C. serum is described. 2. Castration causes a persistent fall (17-24 per cent.) in the calcium content of the serum in females of Xenopus laevis as soon as 2 months after operation. In males there is no effect 3 ½ months after castration but a fall (16 per cent.) 6 months after. 3. Removal of the anterior lobe (i.e.. pars anterior and pars tuberalis) of the pituitary leads to a significantly lower calcium level than removal of the entire gland. 4. Injection of antuitrin into completely hypophysectomised animals causes a rise, injection of pituitrin a fall in serum calcium. Injection of antuitrin into normal animals leads to maximal contraction of melanophores on a black background and injection of pituitrin into normal or completely hypophysectomised toads causes maximal expansion on a white background. 5. When the pars tuberalis regenerates the serum calcium returns to normal concomitantly with the reappearance of the white background response, but without regeneration of the ovaries. 6. The influence of the pituitary on ovarian activity and its effect on serum calcium are concomitant but independent activities. It is suggested that the pars tuberalis and the posterior lobe have antagonistic effects on both colour change and serum calcium, and that the pars anterior and the posterior lobe exert antagonistic influences on ovarian activity. It is further suggested that the pituitary directly controls ovarian activity, but that both the pituitary and the gonads control calcium metabolism through some other endocrine gland.


1959 ◽  
Vol s3-100 (51) ◽  
pp. 463-482
Author(s):  
M. ALLANSON ◽  
C. L. FOSTER ◽  
G. MENZIES

Evidence is presented which suggests that in this animal the pars tuberalis may have some function in addition to acting as a bed for the hypophysial portal system, since its cells appear rich in RNA. The granules of the cells of the pars intermedia are shown to be PAS-positive, but this reaction, unlike that of the basiphil cells of the pars distalis proper and the zona tuberalis, is readily prevented by pretreatment of sections with proteolytic enzymes. A study of the basiphil cells of the pars distalis proper and of the zona tuberalis, based on cytological characteristics, size, and shape, provides some evidence for the existence of two, and possibly three, kinds of basiphil cell. The lipid inclusions of the adenohypophysial cells and their relationship to the Golgi elements are described, together with some brief preliminary observations upon the electron microscopic characteristics of acidophil and basiphil cells.


1960 ◽  
Vol 20 (1) ◽  
pp. 48-55 ◽  
Author(s):  
R. L. HOLMES

SUMMARY Six distinct types of cell can be distinguished in the pars distalis of the pituitary gland of the female ferret after staining by performic acid-Alcian blue followed by periodic acid-Schiff (PAS)-orange G. The first of these types contains coarsely granular PAS-positive material; the second contains granules which stain with Alcian blue, with or without PAS-positive material; while the third contains finely granular or diffuse PAS-positive material. The fourth type of cell, apparently equivalent to the 'carminophil' of other species, stains deep orange due to a combination of staining with orange G and a weakly positive PAS reaction. The fifth type is the ordinary acidophil, and the sixth the chromophobe. The pars tuberalis is extensive, and may be compact or lobulated. The pars intermedia contains two types of cell, but shows no obvious secretory characteristics. The neural process consists of a central zone which resembles the stalk in structure, and a peripheral, more vascular zone which contains the bulk of the neurosecretory material. A nucleus of small nerve cells lies in the junctional region where the stalk joins the main neural process.


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