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- Hernandez, Marta, et al.
(författare)
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Cryo-scanning electron microscopy (Cryo-SEM) of semen frozen in medium-straws from good and sub-standard freezer AI-boars
- 2007
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Ingår i: Cryobiology. - : Elsevier. - 0011-2240 .- 1090-2392. ; 54:1, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- A major limiting factor for commercial cryopreservation of boar semen for artificial insemination (AI) is the large individual variation to cooling, where the degree of cell dehydration during ice (re)shaping seems to play a major role. This study investigated, in the frozen state, the degree of dehydration and ice crystal distribution in boar semen doses whose spermatozoa displayed different viability after thawing. Cross-sectioned medium-straws (0.5 mL, n = 10) from a total of 10 stud boars classified as "good" (n = 5) or sub-standard (e.g., "bad" freezers, n = 5) by conventional analyses (computer assisted motility and sperm viability) were examined by Cryo-scanning electron microscopy (Cryo-SEM) to determine whether differences between groups could be already distinguishable prior to thawing. The degree of hydration was monitored in relation to the areas of ice crystal formed extracellularly (lakes), the areas of frozen, concentrated extender (veins) where spermatozoa were located and the degree of compartmentalization (number of lakes) present. Irrespectively of the region studied, the gradient of main dehydration (as lakes) observed along the cross-section area of the straws was very irregular. Most spermatozoa were enclosed in the freezing extender matrix and no obvious signs of external membrane damage were observed. None of the Cryo-SEM variables significantly correlated with post-thaw sperm parameters (p greater than 0.05). However, we identified significant differences (p less than 0.0001) among boars for all ultrastructure variables studied, including the size of the veins, where differences in solute concentration is expected. We concluded that despite the large variability in ice crystal formation during the conventional freezing process among boars, this is unrelated to inter-boar post-thaw sperm differences. (c) 2007 Elsevier Inc. All rights reserved.
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- Hernandez, Marta, et al.
(författare)
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Differences in SCSA outcome among boars with different sperm freezability
- 2006
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Ingår i: International Journal of Andrology. - : Wiley-Blackwell. - 0105-6263 .- 1365-2605. ; 29:6, s. 583-591
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Tidskriftsartikel (refereegranskat)abstract
- Spermatozoa from some boars sustain the process of cryopreservation poorly and yield poor fertility after artificial insemination. Poor freezability has not been disclosed using conventional semen analyses. A defective chromatin can, if present in a substantial number of spermatozoa, affect the fertilizing ability of spermatozoa. Here we tested the hypothesis that nuclear DNA instability could explain differences in freezability among boars, and complement or supersede conventional tests for sperm quality such as sperm motility or membrane assessments. Frozen-thawed (FT) spermatozoa from a total of 44 stud boars were assessed by the sperm chromatin structure assay (SCSA), in relation to computer-assisted sperm analysis-derived sperm motility variables and sperm viability (triple fluorescent microscopic staining), including three experiments. The first trial, including 24 boars, evaluated the relationship between the sperm motility and viability with levels of DNA integrity. The SCSA showed that most spermatozoa had intact DNA [levels of DNA fragmentation index (%DFI) ranging from 0.63% to 11.85%] significantly correlated (albeit weakly) with current sperm quality variables. The second trial, on 15 boars, assessed the influence of two different thawing rates (20 s at 37 degrees C vs. 8 s at 70 degrees C) and the post-thaw incubation times (0, 30, 150 and 300 min) at 37 degrees C on FT-boar sperm quality. The highest sperm survival (p less than 0.05) and the lowest DNA damage (p less than 0.01) were achieved when thawing was carried out at 70 degrees C for 8 s, without any change during the first 150 min of incubation. Finally, the third experiment studied if differences in sperm freezability showed by stud boar semen, as good or bad freezers by conventional analyses, could be attributed to differences in chromatin structure. All SCSA parameters were low, but significantly (p less than 0.05-0.001) higher for bad freezers, showing they had less homogeneous sperm chromatin than the good freezers. The results indicate that SCSA outcome complements conventional assessment of FT-boar spermatozoa, disclosing differences in their ability to sustain freezing and thawing. However, the low overall DNA damage observed in FT spermatozoa seems to have poor biological significance.
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- Ferro-Vázquez, Cruz, et al.
(författare)
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Tracing Pb Pollution Penetration in Temperate Podzols
- 2017
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Ingår i: Land Degradation and Development. - : John Wiley & Sons. - 1085-3278 .- 1099-145X. ; 28:8, s. 2432-2445
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Tidskriftsartikel (refereegranskat)abstract
- We combine high-resolution soil sampling with lead (Pb) analyses (concentrations and stable isotopes) in two temperate podzols, together with previous data obtained with selective Al and Fe dissolution techniques. We aim to assess how atmospheric Pb is incorporated into the soils during pedogenesis. Partial least squares modelling for Pb concentrations shows that the podzolization process has the largest effect on Pb concentration (803% of the variance). The proportion of inorganic secondary compounds, the input of fresh organic matter from the soil surface and the relative abundance of Fe versus Al are responsible for a small part of the Pb concentration variance. Lead isotopic composition (Pb-206/Pb-207 ratios) depends on soil organic matter content either fresh/poorly humified (573% of the variance) or humified (247% of the variance). The Pb linked to inorganic compounds and the overall podzolization process play a minor role in isotopic signature (53 and 37% of the variance respectively). Soil pH appears to be the controlling variable of the different transport and retention mechanisms. The relatively low isotopic ratios observed in spodic horizons result from geogenic Pb released through the preferential dissolution of the isotopically distinct most weatherable minerals of the parent material in the eluvial horizons, which undergoes downward mobilization. An accurate knowledge of soil reactive components and formation mechanisms is essential to a correct diagnose of the scope of Pb pollution and a more effective design of remediation strategies.
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- Nguyen, Thanh N, et al.
(författare)
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Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up.
- 2023
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Ingår i: Neurology. - 1526-632X. ; 100:4
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Tidskriftsartikel (refereegranskat)abstract
- Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.This study is registered under NCT04934020.
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