University:
Amherst College
Course:
BIOL 220 | Developmental Biology
Academic year:

2020
Views:

260

Pages:

15
Author:

Barti7q5

Cross Section of Tubule Are Cells Only Controlled by External Signals? • Male germ cells often form nests connected by cytoplasmic bridges by incomplete cell division • May contribute to synchrony of development in the differentiation phase (spermiogenesis) • It takes 65 days from spermatogonia to spermatozoa in humans Spermatogonial Syncitium Syncitia in Spermiogenesis Do Testicular Somatic Cells Communicate? Leydig Peritubular Sertoli Do Pituitary and Testis Communicate? • Communication axes – brain testis • brain: luteinizing and follicle stimulating hormones (LH, FSH) • testis: inhibin, activin, follistatin – somatic somatic • peritubular PModS Sertoli • Leydig testosterone Sertoli and peritubular • Sertoli stimulatory and inhibitory factors Leydig Do Somatic and Germ Line Communicate in Testis? • Communication axes (cont.) – somatic germ line • germ line: basic fibroblast growth factor, nerve growth factor • somatic: testosterone, various growth factors How is Cell Differentiation Accomplished to Make Sperm? • Major alterations to make mature sperm cell – Golgi acrosomal vesicle – nucleus compacted and new DNA binding proteins – centrosomes associate with head – mitochondria fused or collected in midpiece – flagellum – shedding of excess cytoplasm Morphogenesis of Spermatids Is Spermiogenesis Progressive? All spermatids All haploid Are There Functional Differences in Mature Sperm Surface? Internal Specialization of the Head: Nucleus and Acrosome Is There Great Diversity in Mature Sperm Morphology? E.B. Wilson, 1898 To Be a Good Sperm, It’s Not Enough to Be Beautiful and Run Fast Sperm are differentiated for many tasks: e.g. swimming, egg recognition, penetration of egg coats, fusion, delivery of genome Is There Biochemical Diversity Among Animals? • DNA packaging proteins – highly conserved histones in somatic cells • basic DNA binding nucleosome forming proteins – in spermatozoa • wide array of different types • Hypothesis • no replication, transcription, metaphase chromosomes in spermiogenesis • removes all evolutionary constraints associated with these processes • proteins free to diverge

Structure of a Mammalian Testis Part 2

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