{'fraction_non_alphanumeric': 0.014607185155941572, 'fraction_numerical': 0.0011843663639952626, 'mean_word_length': 5.019002375296912, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Local control of testicular function.

This review has shown that local control of testicular function exists at three different levels. (1) Regulation of the entry of substances into the testis via the operation of selective barriers at the level of the capillary endothelium, myoid layer and Sertoli cell tight junctions, and by control of the rate of interstitial fluid formation which is the medium for transport into and within the testis. These mechanisms permit the creation of specific micro-environments around the Leydig cells and outside of the seminiferous tubules as well as within the tubules, prerequisites for the local interaction and communication summarized below. (2) Regulation of spermatogenesis by co-ordination of changes in hormone responsiveness and function of the Sertoli cells with the requirements of the associated germ cells, this varying according to the stage of the spermatogenic cycle. These changes involve regulation of germ cell multiplication, their differentiation and translocation from the basal to the adluminal compartment of the seminiferous tubule and their release into the lumen. (3) Interaction between the seminiferous tubules and the Leydig cells via various factors. The purpose of this interaction is not certain but in the prepubertal testis it probably co-ordinates development of the tubules and Leydig cells, whilst in the adult testis it probably functions to regulate the steroidogenic responsiveness of the Leydig cells in accordance with the stage-dependent requirements of the adjacent seminiferous tubules. 
 
 
 
Local control mechanisms within the testis therefore appear to co-ordinate the function of the different cell types in the two testicular compartments and, as this is essential for normal function of the testis, the importance of local factors is self-evident. In each of the three areas there is still only limited information as to the precise operation of the various mechanisms and even less is known about the identity of the co-ordinating agents. But, as most of the available information derives only from the last three years, the gaps in our knowledge are to be expected and it is certain that the next few years will see major advances in this area. If the interpretation of the data offered in this review proves accurate then we are on the threshold of a revolution in our understanding of the control of testicular function, and of spermatogenesis in particular. This can only lead to improved methods for regulation of fertility in the male.