Age-Associated Metabolic and Morphologic Changes in Mitochondria of Individual Mouse and Hamster Oocytes

Background: In human oocytes, as in other mammalian ova, there is a significant variation in the pregnancy potential, with approximately 20% of oocyte-sperm meetings resulting in pregnancies. This frequency of successful fertilization decreases as the oocytes age. This low proportion of fruitful couplings appears to be influenced by changes in mitochondrial structure and function. In this study, we have examined mitochondrial biogenesis in both hamster (Mesocricetus auratus) and mouse (Mus musculus) ova as models for understanding the effects of aging on mitochondrial structure and energy production within the mammalian oocyte. Methodology/Principal Findings: Individual metaphase II oocytes from a total of 25 young and old mice and hamsters were collected from ovarian follicles after hormone stimulation and prepared for biochemical or structural analysis. Adenosine triphosphate levels and mitochondrial DNA number were determined within individual oocytes from young and old animals. In aged hamsters, oocyte adenosine triphosphate levels and mitochondrial DNA molecules were reduced 35.4% and 51.8%, respectively. Reductions of 38.4% and 44% in adenosine triphosphate and mitochondrial genomes, respectively, were also seen in aged mouse oocytes. Transmission electron microscopic (TEM) analysis showed that aged rodent oocytes had significant alterations in mitochondrial and cytoplasmic lamellae structure. Conclusions/Significance: In both mice and hamsters, decreased adenosine triphosphate in aged oocytes is correlated with a similar decrease in mtDNA molecules and number of mitochondria. Mitochondria in mice and hamsters undergo significant morphological change with aging including mitochondrial vacuolization, cristae alterations, and changes in cytoplasmic lamellae

Search for a Light Charged Higgs Boson Decaying to a W Boson and a CP-Odd Higgs Boson in Final States with eμμ or μμμ in Proton-Proton Collisions at √s=13 TeV

A search for a light charged Higgs boson (H+) decaying to a W boson and a CP-odd Higgs boson (A) in final states with eμμ or μμμ is performed using data from pp collisions at √s=13  TeV, recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9  fb−1. In this search, it is assumed that the H+ boson is produced in decays of top quarks, and the A boson decays to two oppositely charged muons. The presence of signals for H+ boson masses between 100 and 160 GeV and A boson masses between 15 and 75 GeV is investigated. No evidence for the production of the H+ boson is found. Upper limits at 95% confidence level are obtained on the combined branching fraction for the decay chain, t→bH+→bW+A→bW+μ+μ−, of 1.9×10−6 to 8.6×10−6, depending on the masses of the H+ and A bosons. These are the first limits for these decay modes of the H+ and A bosons.Peer reviewe

The effects of pentoxifylline on skeletal muscle contractility and neuromuscular transmission during hypoxia

Objectives: The objective of this study was to investigate the effects of pentoxifylline (PTX), a drug that is mainly used for indications related to tissue hypoxia, on hypoxia-induced inhibition of skeletal muscle contractility and neuromuscular transmission in mice. We hypothesized that chronic PTX treatment alters skeletal muscle contractility and hypoxia-induced dysfunction. Materials and Methods: Mice were treated with 50 mg/kg PTX or saline intraperitoneally for a week. Following ether anesthesia, diaphragm muscles were removed; isometric muscle contractions and action potentials were recorded. Time to reach neuromuscular blockade and the rate of recovery of muscle contractility were assessed during hypoxia and re-oxygenation. Results: The PTX group displayed 90% greater twitch amplitudes (P < 0.01). Hypoxia depressed twitch contractions and caused neuromuscular blockade in both groups. However, neuromuscular blockade occurred earlier in PTX-treated animals (P < 0.05). Muscle contractures developed during hypoxia were more pronounced in the PTX group (P < 0.05). Re-oxygenation reduced contracture and indirect muscle contractions resumed. The rate of recovery of contractions was faster (P < 0.05) and the amplitude of contractions was greater (P < 0.01) in the PTX group. PTX treatment increased amplitude (P < 0.05) and shortened action potential (P < 0.05) without altering resting membrane potential, excitation threshold, and neurotransmitter release. Conclusion: Chronic PTX treatment increases diaphragm contractility, but amplifies hypoxia-induced contractile dysfunction in mice. These results may implicate important clinical consequences for clinical usage of PTX in hypoxia-related conditions.PubMedWo

Age-associated metabolic and morphologic changes in mitochondria of individual mouse and hamster oocytes.

BACKGROUND: In human oocytes, as in other mammalian ova, there is a significant variation in the pregnancy potential, with approximately 20% of oocyte-sperm meetings resulting in pregnancies. This frequency of successful fertilization decreases as the oocytes age. This low proportion of fruitful couplings appears to be influenced by changes in mitochondrial structure and function. In this study, we have examined mitochondrial biogenesis in both hamster (Mesocricetus auratus ) and mouse (Mus musculus) ova as models for understanding the effects of aging on mitochondrial structure and energy production within the mammalian oocyte. METHODOLOGY/PRINCIPAL FINDINGS: Individual metaphase II oocytes from a total of 25 young and old mice and hamsters were collected from ovarian follicles after hormone stimulation and prepared for biochemical or structural analysis. Adenosine triphosphate levels and mitochondrial DNA number were determined within individual oocytes from young and old animals. In aged hamsters, oocyte adenosine triphosphate levels and mitochondrial DNA molecules were reduced 35.4% and 51.8%, respectively. Reductions of 38.4% and 44% in adenosine triphosphate and mitochondrial genomes, respectively, were also seen in aged mouse oocytes. Transmission electron microscopic (TEM) analysis showed that aged rodent oocytes had significant alterations in mitochondrial and cytoplasmic lamellae structure. CONCLUSIONS/SIGNIFICANCE: In both mice and hamsters, decreased adenosine triphosphate in aged oocytes is correlated with a similar decrease in mtDNA molecules and number of mitochondria. Mitochondria in mice and hamsters undergo significant morphological change with aging including mitochondrial vacuolization, cristae alterations, and changes in cytoplasmic lamellae

Correlation of ATP level and mtDNA copy numbers within single oocytes.

<p>Left panel (A), mouse oocytes and right panel (B), hamster oocytes. Statistical analysis was done by the Pearson correlation test.</p

Ultrastructure of mouse MII oocytes.

<p>A and B are representative TEM micrographs at 3,000X magnification. Note the mitochondria (M) and lipid droplets (LD). C and D are representative TEM micrographs from young (C) and old (D) mice at 12,000X magnification. Note the normal (Mn) and vacuolated (Mv).mitochondria (Bar: A&B, 2 µm; C&D, 500 nm).</p

Ultrastructure of hamster MII oocytes.

<p>A and B are representative TEM micrographs at 2,000X magnification, showing various cytoplasmic lamellae (CL) and numerous mitochondria (M) in this oocyte from a young animal (A) compared to the number in an oocyte from an old hamster (B). C and D are representative TEM micrographs of oocytes from young (C) and old (D) hamsters at 10,000X magnification. Note the dark mitochondria (Md) and mitochondria with clear cristae (Mc). The old ova also showed the presence of collapsed cytoplasmic lamellae (cCL). (Bar: A&B, 2 µm; C&D, 500 nm).</p

Measurement of ATP levels (fmoles) in individual mouse (A) and hamster (B) oocytes.

<p>Note that there is a 38.4% decrease in ATP levels in old mice vs. young mice (<i>P</i><0.0001) and a 35.4% drop in ATP in old vs. young hamster oocytes. (<i>P</i> = 0.002). Data are also presented as median with 10^th, 25^th, 75^th, and 90^th percentiles and outliers in whisker plot inserts. Statistical analysis was performed by Student T-test and a <i>P</i> value less than 0.05 was considered significantly different between the groups.</p

Real-time PCR analysis of mtDNA copy numbers in individual mouse (A) and hamster (B) oocytes.

<p>mtDNA copy numbers were significantly lower in old oocytes compared to young oocytes in both mice and hamsters. There is a 44% decrease in mtDNA number in aged mouse oocytes and a 51.8% decrease in aged hamster oocytes. Data were also presented as median with 10^th, 25^th, 75^th, and 90^th percentiles and outliers shown in whisker plot inserts.</p