<em>In Vivo</em> Microinjection and Electroporation of Mouse Testis

This video and article contribution gives a comprehensive description of microinjection and electroporation of mouse testis in vivo. This particular ...

Leibniz Institute for Farm Animal Biology (FBN)

The detection of lymph node metastases is an important step in tumor staging and is significant for therapy planning. Lymph node-specific contrast agents can raise the sensitivity and specificity of modern diagnostic methods. This study investigated the suitability of the dendritic contrast agent Gadomer-17 in magnetic resonance (MR) lymph node imaging and compared three different dosages in such an application.

Interstitial magnetic resonance lymphography using a polymeric t1 contrast agent: initial experience with Gadomer-17.

Mice deficient in selenoprotein P exhibit a disturbed selenium distribution and reduced activities of other selenoenzymes and display defects in growth and motor co-ordination. We have normalized selenoenzyme activities and rescued the phenotype of mutant mice by supplementing their nursing mothers with sodium selenite. Our results indicate that selenium from inorganic sources can be transferred efficiently via mother's milk to the developing offspring in a form that is both highly bioavailable by target tissues and yet sufficiently safe to prevent overdosages.

Efficient selenium transfer from mother to offspring in selenoprotein-P-deficient mice enables dose-dependent rescue of phenotypes associated with selenium deficiency.

Thyroid hormone (TH) homeostasis depends on peripheral activation and inactivation of iodothyronines by selenoenzymes of the deiodinase (Dio) family. We genetically inactivated hepatic selenoenzyme expression, including Dio1, in order to determine the contribution of hepatic Dio to circulating TH levels. Serum levels of TSH, total T(4), and total T(3) were not different from controls. We measured Dio1 and Dio2 in kidney, skeletal muscle, heart, brown adipose tissue, and brain, but did not find compensatory up-regulation in these tissues. Finally, we determined expression in the liver of the following T(3) target genes: Spot14, alpha-glycerophosphate dehydrogenase (alphaGPD), and malic enzyme (ME). On the transcript level, both Spot14 and alphaGPD were reduced in Dio-deficient liver to about 60-70% of controls. However, mRNA and activity of ME were significantly increased in the same mice. Together, our results indicate that hepatic Dio1 activity is not absolutely required to sustain the euthyroid state in mice.

Hepatic deiodinase activity is dispensable for the maintenance of normal circulating thyroid hormone levels in mice.

The thyroid gland is rich in selenium (Se) and expresses a variety of selenoproteins that are involved in antioxidative defense and metabolism of thyroid hormones (TH). Se deficiency impairs regular synthesis of selenoproteins and adequate TH metabolism. We recently generated mice that lack the plasma Se carrier, selenoprotein P (SePP). SePP-knockout mice display decreased serum Se levels and manifest growth defects and neurological abnormalities partly reminiscent of thyroid gland dysfunction or profound hypothyroidism. Thus, we probed the TH axis in developing and adult SePP-knockout mice. Surprisingly, expression of Se-dependent 5'-deiodinase type 1 was only slightly altered in liver, kidney, or thyroid at postnatal d 60, and 5'-deiodinase type 2 activity in brain was normal in SePP-knockout mice. Thyroid gland morphology, thyroid glutathione peroxidase activity, thyroid Se concentration, and serum levels of TSH, T4, or T3 were within normal range. Pituitary TSHbeta transcripts and hepatic 5'-deiodinase type 1 mRNA levels were unchanged, indicating regular T3 bioactivity in thyrotropes and hepatocytes. Cerebellar granule cell migration as a sensitive indicator of local T3 action during development was undisturbed. Collectively, these findings demonstrate that low levels of serum Se or SePP in the absence of other challenges do not necessarily interfere with regular functioning of the TH axis. 5'-deiodinase isozymes are preferentially supplied, and Se-dependent enzymes in the thyroid are even less-dependent on serum levels of Se or SePP than in brain. This indicates a top priority of the thyroid gland and its selenoenzymes with respect to the hierarchical Se supply within the organism.

Synthesis and metabolism of thyroid hormones is preferentially maintained in selenium-deficient transgenic mice.

Important enzymes for thyroid hormone metabolism, antioxidative defense, and intracellular redox control contain selenocysteine (Sec) in their active centers. Expression of these selenoproteins is tightly controlled, and a sex-specific phenotype is observed on disturbance of selenium (Se) transport in mice. Therefore, we analyzed Se concentrations and expression levels of several selenoproteins including type I iodothyronine deiodinase (Dio1) and glutathione peroxidase (GPx) isozymes in male and female mice. On regular lab chow, serum Se levels were comparable, but serum GPx3 activity was higher in females than males (1.3-fold). Selenoprotein P (SePP) mRNA levels were higher in livers (1.3-fold) and lower in kidneys (to 31%) in female compared with male mice. Orchidectomy alleviated the sex-specific differences in SePP mRNA amounts, indicating modulatory effects of androgens on SePP expression. Female mice expressed higher levels of Dio1 mRNA in kidney (2.6-fold) and liver (1.4-fold) in comparison with male mice. This sexual dimorphic expression of Dio1 mRNA was paralleled by increased Dio1 activity in female kidney (1.8-fold) but not in liver in which males expressed higher Dio1 activity (2.8-fold). Interestingly, Se deficiency decreased Dio1 activity more effectively in males than females, and resulting hepatic enzyme levels were then comparable between the sexes. At the same time, the sex-specific difference of Dio1 activity widened in kidney. Orchidectomy or estradiol treatment of ovariectomized females impacted stronger on renal than hepatic Dio1 expression. Thus, we conclude that Se-dependent posttranscriptional mechanisms are operational that affect either translational efficiency or Dio1 stability in a sex- and tissue-specific manner.

Selenium-dependent pre- and posttranscriptional mechanisms are responsible for sexual dimorphic expression of selenoproteins in murine tissues.

Sex-specific differences in blood pressure (BP) suggest an important modulating role of testosterone in the kidney. However, little is known about the interaction between androgens and the mineralocorticoid aldosterone. Our objective was to determine the effects of testosterone in gonadectomized male and female rats on a low-salt diet, and to determine the effect of androgen receptor (AR) blockade by flutamide on BP and on aldosterone levels.

Flutamide increases aldosterone levels in gonadectomized male but not female Wistar rats.

Animal models are valuable tools in fertility research. Worldwide, there are more than 400 transgenic or knockout mouse models available showing a reproductive phenotype; almost all of them exhibit an infertile or at least subfertile phenotype. By contrast, animal models revealing an improved fertility phenotype are barely described. This article summarizes data on two outbred mouse models exhibiting a 'high-fertility' phenotype. These mouse lines were generated via selection over a time period of more than 40 years and 161 generations. During this selection period, the number of offspring per litter and the total birth weight of the entire litter nearly doubled. Concomitantly with the increased fertility phenotype, several endocrine parameters (e.g. serum testosterone concentrations in male animals), physiological parameters (e.g. body weight, accelerated puberty, and life expectancy), and behavioral parameters (e.g. behavior in an open field and endurance fitness on a treadmill) were altered. We demonstrate that the two independently bred high-fertility mouse lines warranted their improved fertility phenotype using different molecular and physiological strategies. The fertility lines display female- as well as male-specific characteristics. These genetically heterogeneous mouse models provide new insights into molecular and cellular mechanisms that enhance fertility. In view of decreasing fertility in men, these models will therefore be a precious information source for human reproductive medicine. Translated abstract A German translation of abstract is freely available at http://www.reproduction-online.org/content/147/4/427/suppl/DC1.

High-fertility phenotypes: two outbred mouse models exhibit substantially different molecular and physiological strategies warranting improved fertility.

Hepatically-derived selenoprotein P (SePP) transports selenium (Se) via blood to other tissues including the testes. Male Sepp-knockout mice are infertile. SePP-mediated Se transport to Sertoli cells is needed for supporting biosynthesis of the selenoenzyme glutathione peroxidase-4 (GPX4) in spermatozoa. GPX4 becomes a structural component of sperm midpiece during sperm maturation, and its expression correlates to semen quality. We tested whether SePP is also present in seminal plasma, potentially correlating to fertility parameters. Semen quality was assessed by sperm density, morphology and motility. SePP was measured by an immunoluminometric assay, and trace elements were determined by X-ray fluorescence spectroscopy. SePP levels were considerably lower in seminal plasma as compared to serum (0.4±0.1 mg/l vs. 3.5±1.0 mg/l); Se concentrations showed a similar but less pronounced difference (48.9±20.7 μg/l vs. 106.7±17.3 μg/l). Se and Zn correlated positively in seminal fluid but not in serum. Seminal plasma SePP concentrations were independent of serum SePP concentrations, but correlated positively to sperm density and fraction of vital sperm. SePP concentrations in seminal plasma of vasectomized men were similar to controls indicating that accessory sex glands are a testes-independent source of SePP. This notion was corroborated by histochemical analyses localizing SePP in epithelial cells of seminal vesicles. We conclude that SePP is not only involved in Se transport to testes supporting GPX4 biosynthesis but it also becomes secreted into seminal plasma, likely important to protect sperm during storage, genital tract passage and final journey.

Marten Michaelis

Institute of Reproductive Biology

Leibniz Institute for Farm Animal Biology (FBN)

In Vivo Microinjection and Electroporation of Mouse Testis

Marten Michaelis

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Institute of Reproductive Biology

Leibniz Institute for Farm Animal Biology (FBN)

In Vivo Microinjection and Electroporation of Mouse Testis

Institute of Reproductive Biology