In testes, the spaceflight mice showed severe degenerative changes, in some cases with tubules
almost devoid of spermatozoa except for few spermatogonia. Tubular degeneration was not
homogenous and differences were not seen between Wt and Tg mice. The expression of
androgen and follicle stimulating hormone receptors increased while luteinizing hormone
receptor levels were not changed.
These data indicate that several changes occur in relevant endocrine organs under the control
of the pituitary gland and they could be responsible for variations of hormone levels in humans
during space missions, significantly affecting the endocrine homeostasis of the body, as well as
the reproductive function (Masini 2012).
Loss of parafollicular cells during gravitational changes (Microgravity, Hypergravity) and the
secret effect of Pleiotrophin
Bone loss is one of the most important complications for crewmembers who are exposed to
long-term microgravity. Changes in blood flow and systemic hormones were indicated as
important contributing elements to the response of the mechanical loading experienced by
osteoblast cells. Here, the possible biological involvement of thyroid C cells is being
investigated.
This study has provided evidence that both microgravity and hypergravity induce similar loss of
thyroid C cells with reduction of calcitonin production. Pleiotrophin over-expression results in
some protection against negative effects of gravity change. To confirm these results it would be
important to know blood levels of calcitonin in hypogravity and hypergravity environments and
this could be an area of study for future missions (Albi-a 2012).
Observing the mouse thyroid Sphingomyelin under space conditions: A case study from the
MDS Mission in comparison with hypergravity conditions
Histological examination of the thyroid gland revealed an increase in the average follicle size
compared to that of 3 control animals and 3 animals exposed to hypergravity (2g) conditions in
a centrifuge. Additional analysis detected an increase in two thyroid gland enzymes,
sphingomyelinase and sphingomyelin-synthase1. In addition, sphingomyelinase, an enzyme
traditionally confined to the cell nucleus in the control animals, was found in the mouse
exposed to hypogravity to be homogenously distributed throughout the cell bodies (Albi-b
2012).
Evaluation of gene, protein and neutrophin expression in the brain of mice exposed to space
environment for 91 days
While modification in the central nervous system are described in literature after short space
missions, long-term inhibition of antigravity activity on the mouse brain are unclear. After the
MDS experiment, the effects of the 3-month exposure to microgravity environment on the
expression of genes and proteins in the mouse brain were studied.