Early Effects of Experimental Cryptorchidism on the Activity of Selected Enzymes in Rat Testes

Ewing, Larry L.; Schanbacher, Larry M.

doi:10.1210/endo-87-1-129

Cited by 19 publications

(8 citation statements)

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“…Given the present focus, I suggest that testis descent provides a means for the cauda epididymidis to 'piggyback' to an inguinal or fully scrotal situation and that the sensitivity of the germinal epithelium to body temperature in scrotal species merely reflects a secondary adaptation of its metabolic machinery to function optimally at the temperature of its location for that species (e.g. Ewing & Schanbacher (1970)). As for the spectrum of anatomical variations, the size of the testis and character of the scrotum have probably been affected by several factors in the course of mammalian evolution.…”

Section: The Scrotummentioning

confidence: 95%

Singular features of fertilization and their impact on the male reproductive system in eutherian mammals

Bedford

2014

Reproduction

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Therian (marsupial and eutherian) mammals have evolved a suite of novel reproductive features -seen variously in their gametes, the steps of fertilization and the male reproductive tract -whose adaptive significance remains unclear. Present evidence for the betterunderstood eutherian mammals suggests that the 'prime mover' in their evolution has been the character of the egg coat, with other such features being adaptations to the consequences of this. Its elastic thickness allows the zona pellucida to stretch to a variable degree and yet remain around the blastocyst during much or all of its expansion before implantation, but its character represents an unusual challenge for spermatozoa. Novel aspects of the acrosome related to this challenge enable it to maintain a relatively prolonged binding after the onset of the acrosome reaction, and the structure, shape and behaviour of the sperm head point to physical thrust as a major element of zona penetration -with the unique configuration of gamete fusion as a sequela of this strategy. In the male, such adaptations are reflected in sperm head formation in the testis and in sperm maturation in the epididymis involving at least the sperm head's structure, plasmalemma and acrosome. This complexity allied to a slow epididymal sperm transport, a relatively modest sperm production and the brief life span of mature spermatozoa kept above the cauda epididymidis could account for the evolution of the sperm storage function -a development seemingly linked, in turn, to the need for sperm capacitation and scrotal evolution.Reproduction (2014) 147 R43-R52

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Section: The Scrotummentioning

confidence: 95%

Singular features of fertilization and their impact on the male reproductive system in eutherian mammals

Bedford

2014

Reproduction

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“…sperm motility of reptiles increases with temperature peaking around 30 °C (Licht 1972;Joly and SaintGirons 1975), while testicles of obligate endothermic mammals are often externalized and kept a few degrees below body temperature (Thundathil et al 2012). In fact, some enzymatic isoforms in rat testes display optimal kinetics of 32 °C (Ewing and Schanbacher 1970). The temperature dependence for hatching speed and reproductive success is similar in reptile females (Clarke and Zani 2012;Amiel and Shine 2012;Bell et al 2013).…”

Section: The Potential Role For Ancient Bat In Reproductionmentioning

confidence: 99%

Brown adipose tissue: physiological function and evolutionary significance

2015

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In modern eutherian (placental) mammals, brown adipose tissue (BAT) evolved as a specialized thermogenic organ that is responsible for adaptive non-shivering thermogenesis (NST). For NST, energy metabolism of BAT mitochondria is increased by activation of uncoupling protein 1 (UCP1), which dissipates the proton motive force as heat. Despite the presence of UCP1 orthologues prior to the divergence of teleost fish and mammalian lineages, UCP1's significance for thermogenic adipose tissue emerged at later evolutionary stages. Recent studies on the presence of BAT in metatherians (marsupials) and eutherians of the afrotherian clade provide novel insights into the evolution of adaptive NST in mammals. In particular studies on the 'protoendothermic' lesser hedgehog tenrec (Afrotheria) suggest an evolutionary scenario linking BAT to the onset of eutherian endothermy. Here, we review the physiological function and distribution of BAT in an evolutionary context by focusing on the latest research on phylogenetically distinct species.

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“…There are several examples of organs adapting to lower temperatures, and in the case of the scrotal testis its sensitivity may just reflect an adaptation of key metabolic pathways. For instance, the kinetics of the rat testis isoform, phosphofructokinase, are optimal at 32 o C rather than 37 o C (Ewing and Schanbacher, 1970).…”

Section: Sperm Capacitationmentioning

confidence: 99%

Puzzles of mammalian fertilization and beyond

Bedford¹

2008

Int. J. Dev. Biol.

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A complexity imposed on the events of conception during the evolution of eutherian mammals is reflected not only in the placenta but also in a series of gamete-related novelties that involve the design of sperm and eggs, their interactions leading to fertilization, epididymal function, and even the scrotal state. While their functional significance has been difficult to determine, I suggest on the basis of present evidence that the genesis of these novel features relates ultimately to changes in the egg associated with nidation, that they imply a new fertilization strategy, and that most are causally linked -a major first 'domino' being the formidable zona pellucida. The eutherian zona pellucida stands out by virtue of an elastic resilience and thickness which allow it to stretch around the expanding blastocyst. However, this quality of the zona together with its relative protease-insensitivity creates a physical challenge which appears to have determined the design of the sperm head, its behaviour at fertilization, and indirectly even the pattern of sperm maturation in the epididymis. In turn, that pattern appears to have evoked the development of the sperm storage function of the cauda region, with both sperm capacitation and the scrotal state as ultimate legacies of this. Coincidentally, the vulnerability of the small yolkless egg to polyspermy appears to have selected for a unique parsimonious pattern of sperm transport in the Fallopian tube, and possibly for the role of the cumulus oophorus as a sperm sequestering device. These ideas are supported generally by evidence from marsupials, as well as by the deviant patterns seen in some insectivorous mammals.

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Early Effects of Experimental Cryptorchidism on the Activity of Selected Enzymes in Rat Testes

Cited by 19 publications

References 0 publications

Singular features of fertilization and their impact on the male reproductive system in eutherian mammals

Singular features of fertilization and their impact on the male reproductive system in eutherian mammals

Brown adipose tissue: physiological function and evolutionary significance

Puzzles of mammalian fertilization and beyond

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