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41.
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>0.05). However, we identified significant differences (p<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.  相似文献   
42.
DNA methylation is an epigenetic modification that regulates gene expression by DNA methyltransferases (DNMTs). Inhibition of DNMTs is a promising approach for cancer therapy. Recently, novel classes of the quinolone-based compound, SGI-1027, and RG108-procainamide conjugates, CBC12, have been identified as potent DNMT inhibitors. In this work, we report comprehensive studies using induced-fit docking of SGI-1027 and CBC12 with human DNMT1 and DNMT3A. The docking was performed in the C-terminal MTase catalytic domain, which contains the substrate and cofactor binding sites, in the presence and absence of other domains. Induced-fit docking predicts possible binding modes of the ligands through the appropriate structural changes in the receptor. This work suggests a hypothesis of the inhibitory mechanisms of the new inhibitors which is in agreement with the reported autoinhibitory mechanism. The insights obtained in this work can be used to design DNMT inhibitors with novel scaffolds.  相似文献   
43.
Boar spermatozoa collected in the ejaculate sperm peak-portion (P1, first 10 mL of the sperm-rich fraction, SRF), had shown a higher resilience to freezing and thawing compared to spermatozoa from the rest of the ejaculate (2nd portion of the SRF plus the post-sperm-rich fraction, PSRF), even when using a simplified freezing technique, as long as spermatozoa were incubated in their own seminal plasma (SP). This experiment studied the stability of P1- and SRF-P1 boar spermatozoa frozen in MiniFlatPacks (MFP), post-thaw, using flow cytometry. Since spermatozoa from either portion showed similar cryosurvival and low proportions of unstable membranes (<3%, annexin-V/propidium iodide staining), and only a tendency for SRF-P1 live spermatozoa to depict acrosome exocytosis (FITC-PNA/PI/H33342); they were explored for Ca(2+) contents using a Fluo-4 probe under in vitro capacitating conditions (mBO+ medium), as well they were tested for their ability to sustain a short Ca(2+)-ionophore (A23187) in vitro challenge. The proportions of live spermatozoa depicting high Ca(2+)-levels were initially <2% but increased over incubation time, particularly in SRF-P1(P<0.05), while proportions of live spermatozoa with low Ca(2+)-levels were basically constant over incubation time (~11-14%), for either portion. Incubation in capacitation medium did not modify the proportions of low-Ca(2+) but dramatically increased the proportions of high-Ca(2+) spermatozoa (P<0.001) already after 15 min exposure, highest for SRF-P1 spermatozoa. While the proportion of live spermatozoa with intact acrosome was significantly decreased among SRF-P1 (P<0.001), that of P1-spermatozoa remained unchanged, probably owing to the lowest relative content of cytosolic Ca(2+). The results suggest that spermatozoa in the P1-portion are more resilient to express acrosome exocytosis post-thaw compared to those bathing in the rest of the SRF-fraction when cryopreserved using a simplified technique, in MFPs.  相似文献   
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45.
Boar spermatozoa in the oviduct   总被引:5,自引:0,他引:5  
In the pig, a functional tubal sperm reservoir (SR) is established before ovulation to ensure availability of suitable numbers of viable spermatozoa for fertilization. The boar's large ejaculate is split: most spermatozoa are delivered in a sperm-rich fraction (SRF) followed by a post-SRF fraction containing increasing amounts of the spermadhesin PSP-I/PSP-II-rich seminal vesicle secretion. This heterodimer acts as leukocyte chemoattractant both in vitro and in vivo, contributing to the phagocytosis of those spermatozoa not reaching the SR. Sequential ejaculate deposition of marked spermatozoa and SR screening showed that most spermatozoa in the SR arose from the fortuitous PSP-poor, first portion of the SRF fraction, escaping phagocytosis and replenishing the SR within 2-3 h. The SR-sperm numbers diminish gradually in relation to ovulation, spermatozoa being continuously redistributed toward the upper isthmus. In vitro, only uncapacitated spermatozoa bind to epithelial explants, suggesting that the SR influences sperm capacitation. In vivo, most viable spermatozoa--usually harbored in the deep furrows in the pre- or peri-ovulatory SR during spontaneous standing estrus--are uncapacitated, but capacitation significantly increases after ovulation. Pre-/peri-ovulatory SR spermatozoa promptly capacitate in vitro when exposed to the effector bicarbonate, an influence that can be reversed by co-incubation with SR fluid or its component hyaluronan. Fluid collected from the ampullar segment (rich in bicarbonate) induces capacitation in vitro. In conclusion, the lack of massive sperm capacitation in the SR and the diverse individual response to capacitation shown by tubal spermatozoa would relate both to the insurance of full sperm viability before ovulation and the presence of spermatozoa at different stages of capacitation in the upper oviduct, thus maximizing the chances of normal fertilization.  相似文献   
46.
The head louse Pediculus humanus capitis (De Geer) is a hematophagous ectoparasite that inhabits the human scalp. The infestations are asymptomatic; however, skin irritation from scratching occasionally may cause secondary bacterial infections. The present study determined the presence and frequency of the knockdown resistance (kdr) mutation T929I in 245 head lice collected from Mexico, Peru, and Canada. Head lice were collected manually using a comb in the private head lice control clinic. Allele mutation at T9291 was present in 100% of the total sampled populations (245 lice) examined. In addition, 4.89% of the lice were homozygous susceptible, whereas 6.93% heterozygous and 88.16% homozygous were resistant, respectively. This represents the second report in Mexico and Quebec and fist in Lima.  相似文献   
47.
48.
α-Conotoxins are peptide neurotoxins isolated from venomous cone snails that display exquisite selectivity for different subtypes of nicotinic acetylcholine receptors (nAChR). They are valuable research tools that have profound implications in the discovery of new drugs for a myriad of neuropharmacological conditions. They are characterized by a conserved two-disulfide bond framework, which gives rise to two intervening loops of extensively mutated amino acids that determine their selectivity for different nAChR subtypes. We have used a multistep synthetic combinatorial approach using α-conotoxin ImI to develop potent and selective α7 nAChR antagonists. A positional scan synthetic combinatorial library was constructed based on the three residues of the n-loop of α-conotoxin ImI to give a total of 10,648 possible combinations that were screened for functional activity in an α7 nAChR Fluo-4/Ca2+ assay, allowing amino acids that confer antagonistic activity for this receptor to be identified. A second series of individual α-conotoxin analogs based on the combinations of defined active amino acid residues from positional scan synthetic combinatorial library screening data were synthesized. Several analogs exhibited significantly improved antagonist activity for the α7 nAChR compared with WT-ImI. Binding interactions between the analogs and the α7 nAChR were explored using a homology model of the amino-terminal domain based on a crystal structure of an acetylcholine-binding protein. Finally, a third series of refined analogs was synthesized based on modeling studies, which led to several analogs with refined pharmacological properties. Of the 96 individual α-conotoxin analogs synthesized, three displayed ≥10-fold increases in antagonist potency compared with WT-ImI.  相似文献   
49.
Parasitic infections caused by the protozoa Trichomonas vaginalis and Giardia intestinalis still represent a major problem in developing countries. Despite the fact that benzimidazoles are promising compounds with activity against both protozoa, systematic studies to characterize and compare their structure-activity relationships (SAR) are limited. Herein, we report a systematic characterization of the SAR of 32 benzimidazoles with activity against T. vaginalis and G. intestinalis. The analysis was based on pairwise comparisons of the activity similarity and molecular similarity using different molecular representations. Radial, MACCS keys, TGD and piDAPH3 fingerprints were used to develop consensus models of the landscape. The landscapes contained continuous regions and activity cliffs. Two 'deep consensus activity cliffs' and several pairs of compounds in smooth regions of the SAR were identified in the landscape of T. vaginalis. In contrast, a number of 'apparent and shallow cliffs' were found for G. intestinalis. Several compounds active for both parasites showed similar SAR suggesting a common mechanism of action. We also identified pairs of structurally similar molecules with dramatic changes in selectivity. Results suggested that while substitution at position 2 on the benzimidazole moiety plays an important role in increasing the potency against both parasites, substitutions at positions 4-7 could influence selectivity. This study represents a first step towards the systematic characterization of the antiprotozoal activity landscape of benzimidazoles, and has direct implications in the future development of other types of quantitative models. The landscape of larger data sets with other biological endpoints can be analyzed using the general approaches used in this work.  相似文献   
50.
The five recognized endemic pamphagid species (Orthoptera) of the Canary Islands have restricted and fragmented ranges due to habitat decline. Seven polymorphic microsatellite markers have been developed for Acrostira tamarani, and the performance of primer pairs amplifying these loci in related taxa has been tested. The number of alleles in A. tamarani samples taken from two distant localities in the island of Gran Canaria ranged from two to eight per locus. Observed heterozygosities were from 0.151 to 0.559. Up to four primer pairs amplified in related species with moderate heterozigosities (maximum of 0.687 and 10 alleles for Ata67 locus in Purpuraria erna). These markers could be useful tools to study the population structure and management of endemic threatened pamphagids of the Canary archipelago.  相似文献   
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