NEUROSECRETION 



Stainable neurosecretory material as well as maximal 

 amounts of the oxytoxic and vasopressor hormones 

 may be obtained from the same granule fraction of 

 posterior lobe homogenates (132, 246, 292). The re- 



FIG. 19. A, cross-section of the regenerated neural lobe of a 

 toad 6 mos. after hypophysectomy and autotransplantation of 

 the pars distalis; B, cross-section of a normal neural lobe (X). 

 Note the sinusoid vessels in the regenerated lobe. Gomori staining 

 method. X 65. [From Jorgensen c/a/. (179).] 



ports of an increase in neurosecretor\- material in the 

 supraoptic and paraventricular nuclei after potas- 

 .sium cyanide poisoning (129) and hypoxia (259) 

 require confirmation. 



Attempts to transplant or culture hypothalamic or 

 posterior lobe tissue have not been particularly suc- 

 cessful. Although cultured nerve fibers of the hypo- 

 thalamus (even from adult tissue) may exhibit re- 

 markable growth, direct evidence of secretory activity 

 could not be demonstrated by either staining methods 

 or by attempts to extract hormones (167). The ob- 

 served transport of particles along the axon cannot 

 be considered as specific evidence of secretory activity 

 in view of the fact that this phenomenon occurred in 

 both directions along the axon as well as the fact that 

 cultures from other regions of the nervous system 

 were observed to behave similarly (126). The efforts 

 to demonstrate hormone secretion in posterior loi)e 

 cultures (123, 134) are considerably handicapped by 

 the large amount of hormone already present in the 

 tissue at the time of explantation (167). With re- 

 peated subculturing of posterior lobe tissue, hormone 

 (as well as neurosecretory material) can no longer be 

 demonstrated (167). This, however, may be due to 

 lack of innervation to the pituicytes as well as to their 

 progressive dedifferentiation to protoplasmic astro- 

 cytes. 



FUNCTIONAL RELATIONSHIPS. In spite of some objections 

 (87, 131, 144, 314), it seems clear that a close relation- 

 ship does exist between the neurosecretory material and 

 the so-called posterior lobe hormones which have been 

 well defined chemically (2). The suggestion to rename 

 the posterior lobe hormones as 'hypothalamus hor- 



2S 



30 



W 



SO 



60 



SSm'm 



FIG. 20. Evidence of antidiuretic and 

 chloride-concentrating action of ex- 

 tracts of hypothalamic nuclei of the 

 dog. Two hours before urine collection, 

 100 cc of vi-ater is administered by 

 stomach tube, with an additional 300 

 cc at the beginning of collection. After 

 a diuresis of 2 to 3 cc per niin. is estab- 

 lished, the extract of supraoptic or 

 paraventricular nucleus is injected 

 intravenously in a dose corresponding 

 to a 4 X 10* part of the nucleus. Urine 

 flow (x — X — x) and chloride concen- 

 tration (x — X — X) measurements are 

 shown after injection of extracts of the 

 supraoptic nucleus, urine flow 

 (O — O — O) and chloride concentration 

 (O — O— O) after injection of extracts 

 of the paraventricular nucleus. [From 

 Hild & Zetler (168).] 



