188 



HYPOPHYSIS AND GONADOTROPHIC HORMONES 



the identification of cell types, the three 

 basophil cell types have been identified as 

 thyrotrophs, FSH cells, and LH cells. It 

 will be noted that it is possible to distinguish 

 cell types by specific staining reactions or 

 by other diagnostic features without identi- 

 fying them. By "identification" is meant 

 here the allocation of specific function or 

 functions to a distinguishable cell type. 



It is not yet certain that all vertebrates 

 have separate FSH and LH or that the phys- 

 iologic reciuirements of all species would re- 

 quire the two hormones, if present, to be 

 secreted separately and by different cells. 

 In some species there may be only one type 

 of basophil cell with gonadotrophic func- 

 tions. It is likely, too, that in some species 

 the duality of the gonadotrophic basophils 

 is concealed by the fact that the staining 

 reactions of the two types may be so alike 

 that a distinction by tinctorial methods 

 cannot be easily or consistently obtained. 

 The term "gonadotroph" can be used as an 

 inclusive term to denote the two types of 

 cells secreting gonadotrophins and is also 

 applicable in cases where a distinction of 

 two such cell types has not been made. 



Thyrotrophs and gonadotrophs have been 

 identified in the guinea pig (D'Angelo, 

 1955), Xenopus (Cordier, 1953; Saxen, 

 Saxen, Toivonen and Salimiiki, 1957), two 

 species of fish, Phoxinus phoxinus (Barring- 

 ton and Matty, 1955) and Caecobarbus 

 geerstii (Olivereau and Herlant, 1954) , and 

 in the pars distalis of the fowl (Payne, 1944, 

 1949; Brown and Knigge, 1958; Mikami, 

 1957 ». From observations recorded by Her- 



R.L. P I. 



Fig. 3.8. Diagram of a horizontal section through 

 tlie rat hypophysis showing the distribution of 

 three types of basophil cell. P.D., pars distalis; 

 P. I., pars intermedia; P.N., pars nervosa; R.L., 

 hypophyseal cleft or residual lumen ; P.G., follicle- 

 stimulating hormone cells (peripheral gonado- 

 trophs); C.G., luteinizing hormone cells (central 

 gonadotrophs) ; T.. thyrotrophs. 



lant (1954a) it seems that a differentiation 

 of two kinds of basophil cells presumably 

 thyrotrophs and gonadotrophs is generally 

 observable in amphibians and bony fishes. 



H. THE THREE FUNCTIONAL TYPES OF BASO- 

 PHIL CELL IN THE R.\T HYPOPHYSIS 



The identification of three functional 

 types of basophil cells was first achieved in 

 the rat by means which did not depend on 

 specific staining reactions, the shape of the 

 cells, their distribution and other minor 

 features (Fig. 3.8). The pars anterior of 

 the rat hypophysis has certain advantages 

 which helped these identifications. Its hor- 

 mone content and secretory function have 

 been extensively investigated. It contains 

 an adequate number of w^ell granulated 

 basophils. Its small size allows its cell popu- 

 lation to be evaluated under the micro- 

 scope without an inordinate expenditure of 

 time and the use of tedious cell enumeration 

 techniques. 



Another favorable quality shown by the 

 rat hypophysis is its reactivity. The hor- 

 mone content can be varied over a wide 

 range by experimental procedures, and vari- 

 ations in secretion rate are accompanied 

 by striking changes in the size and granule 

 content of basophil cells. Especially con- 

 spicuous are the hyalinized cells derived 

 from basophil cells. Under conditions of 

 rapid secretion there is an accumulation of 

 a structureless protein solution called hya- 

 line substance in certain small cytoplasmic 

 vesicles. By distension and coalescence of 

 these vesicles one or more large hyaline- 

 filled spaces result. 



Evidence suggesting that the basophil 

 cell class might consist of two distinct func- 

 tional subdivisions, one concerned with thy- 

 rotrophic activity and one with gonado- 

 ti'ophic, was obtained from the study of the 

 changes occurring after thyroidectomy and 

 castration. In both these conditions an in- 

 crease in the number and activity of cells of 

 the basophil class are observed and the ini- 

 tial cellular hypertrojihy is followed by hya- 

 linization of a proportion of the basophills. 

 The hyalinized cells appearing after thy- 

 roidectomy (Figs. 3.9 and 3.10) are called 

 thyroidectomy cells, those appearing after 

 castration (Figs. 3.11 and 3.12) castration 

 or signet ring cells. In the rat there are a 



