Acquired enamel pellicle and biofilm engineering with a combination of acid-resistant proteins (CaneCPI-5, StN15, and Hemoglobin) for enhanced protection against dental caries - in vivo and in vitro investigations

OBJECTIVE

This study was designed in two-legs. In the in vivo, we explored the potential of a rinse solution containing a combination (Comb) of 0.1 mg/mL CaneCPI-5 (sugarcane-derive cystatin), 1.88 × 10- 5M StN15 (statherin-derived peptide) and 1.0 mg/mL hemoglobin (Hb) to change the protein profile of the acquired enamel pellicle(AEP) and the microbiome of the enamel biofilm. The in vitro, was designed to reveal the effects of Comb on the viability and bacterial composition of the microcosm biofilm, as well as on enamel demineralization.

MATERIALS AND METHODS

In vivo study, 10 participants rinsed (10mL,1 min) with either deionized water (H2O-control) or Comb. AEP and biofilm were collected after 2 and 3 h, respectively, after rinsing. AEP samples underwent proteomics analysis, while biofilm microbiome was assessed via 16 S-rRNA Next Generation Sequencing(NGS). In vitro study, a microcosm biofilm protocol was employed. Ninety-six enamel specimens were treated with: 1)Phosphate-Buffered Solution-PBS(negative-control), 2)0.12%Chlorhexidine, 3)500ppmNaF and 4)Comb. Resazurin, colony-forming-units(CFU) and Transversal Microradiography(TMR) were performed.

RESULTS

The proteomic results revealed higher quantity of proteins in the Comb compared to control associated with immune system response and oral microbial adhesion. Microbiome showed a significant increase in bacteria linked to a healthy microbiota, in the Comb group. In the in vitro study, Comb group was only efficient in reducing mineral-loss and lesion-depth compared to the PBS.

CONCLUSIONS

The AEP modification altered the subsequent layers, affecting the initial process of bacterial adhesion of pathogenic and commensal bacteria, as well as enamel demineralization.

CLINICAL RELEVANCE

Comb group shows promise in shaping oral health by potentially introducing innovative approaches to prevent enamel demineralization and deter tooth decay.

The central role of pyruvate metabolism on the epigenetic maturation and transcriptional profile of bovine oocytes

In brief

Pyruvate metabolism is one of the main metabolic pathways during oocyte maturation. This study demonstrates that pyruvate metabolism also regulates the epigenetic and molecular maturation in bovine oocytes.

Abstract

Pyruvate, the final product of glycolysis, undergoes conversion into acetyl-CoA within the mitochondria of oocytes, serving as a primary fuel source for the tricarboxylic acid (TCA) cycle. The citrate generated in the TCA cycle can be transported to the cytoplasm and converted back into acetyl-CoA. This acetyl-CoA can either fuel lipid synthesis or act as a substrate for histone acetylation. This study aimed to investigate how pyruvate metabolism influences lysine 9 histone 3 acetylation (H3K9ac) dynamics and RNA transcription in bovine oocytes during in vitro maturation (IVM). Bovine cumulus-oocyte complexes were cultured in vitro for 24 h, considering three experimental groups: Control (IVM medium only), DCA (IVM supplemented with sodium dichloroacetate, a stimulant of pyruvate oxidation into acetyl-CoA), or IA (IVM supplemented with sodium iodoacetate, a glycolysis inhibitor). The results revealed significant alterations in oocyte metabolism in both treatments, promoting the utilization of lipids as an energy source. These changes during IVM affected the dynamics of H3K9ac, subsequently influencing the oocyte's transcriptional activity. In the DCA and IA groups, a total of 148 and 356 differentially expressed genes were identified, respectively, compared to the control group. These findings suggest that modifications in pyruvate metabolism trigger the activation of metabolic pathways, particularly lipid metabolism, changing acetyl-CoA availability and H3K9ac levels, ultimately impacting the mRNA content of in vitro matured bovine oocytes.

Post-mortem muscle proteome of crossbred bulls and steers: Relationships with carcass and meat quality

This study investigated the skeletal muscle proteome of crossbred bulls and steers with the aim of explaining the differences in carcass and meat quality traits. Therefore, 640 post-weaning Angus-Nellore calves were fed a high-energy diet for a period of 180 days. In the feedlot trial, comparisons of steers (n = 320) and bulls (n = 320) showed lower (P < 0.01) average daily gain (1.38 vs. 1.60 ± 0.05 kg/d), final body weight (547.4 vs. 585.1 ± 9.3 kg), which resulted in lower hot carcass weight (298.4 vs. 333.7 ± 7.7 kg) and ribeye area (68.6 vs. 81.0 ± 2.56 cm²). Steers had higher (P < 0.01) carcass fatness, meat color parameters (L*, a*, b*, chroma (C*), hue (h°)) and lower ultimate pH. Moreover, lower (P < 0.01) Warner-Bratzler shear force (WBSF) were observed in steers compared to bulls (WBSF = 3.68 vs. 4.97 ± 0.08 kg; and 3.19 vs. 4.08 ± 0.08 kg). The proteomic approach using two-dimensional electrophoresis, mass spectrometry and bioinformatics procedures revealed several differentially expressed proteins between steers and bulls (P < 0.05). Interconnected pathways and substantial changes were revealed in biological processes, molecular functions, and cellular components between the post-mortem muscle proteomes of the compared animals. Steers had increased (P < 0.05) abundance of proteins related to energy metabolism (CKM, ALDOA, and GAPDH), and bulls had greater abundance of proteins associated with catabolic (glycolysis) processes (PGM1); oxidative stress (HSP60, HSPA8 and GSTP1); and muscle structure and contraction (TNNI2 and TNNT3). The better carcass (fatness and marbling degree) and meat quality traits (tenderness and color parameters) of steers were associated with higher abundance of key proteins of energy metabolism and lower abundance of enzymes related to catabolic processes, oxidative stress, and proteins of muscle contraction SIGNIFICANCE: Sexual condition of cattle is known to be an important factor affecting animal performances and growth as well as the carcass and meat quality traits. The investigation of skeletal muscle proteome help a better understanding of the origin of the differences in quality traits between bulls and steers. The inferior meat quality of bulls was found to be due to the greater expression of proteins associated with primary and catabolic processes, oxidative stress, and muscle contraction. Steers had greater expression of proteins, from which several are known biomarkers of beef quality (mainly tenderness).

Effect of Cow-Calf Supplementation on Gene Expression, Processes, and Pathways Related to Adipogenesis and Lipogenesis in Longissimus thoracis Muscle of F1 Angus × Nellore Cattle at Weaning

The aim of this study was to identify differentially expressed genes, biological processes, and metabolic pathways related to adipogenesis and lipogenesis in calves receiving different diets during the cow-calf phase. Forty-eight uncastrated F1 Angus × Nellore males were randomly assigned to two treatments from thirty days of age to weaning: no creep feeding (G1) or creep feeding (G2). The creep feed offered contained ground corn (44.8%), soybean meal (40.4%), and mineral core (14.8%), with 22% crude protein and 65% total digestible nutrients in dry matter. After weaning, the animals were feedlot finished for 180 days and fed a single diet containing 12.6% forage and 87.4% corn-based concentrate. Longissimus thoracis muscle samples were collected by biopsy at weaning for transcriptome analysis and at slaughter for the measurement of intramuscular fat content (IMF) and marbling score (MS). Animals of G2 had 17.2% and 14.0% higher IMF and MS, respectively (p < 0.05). We identified 947 differentially expressed genes (log₂ fold change 0.5, FDR 5%); of these, 504 were upregulated and 443 were downregulated in G2. Part of the genes upregulated in G2 were related to PPAR signaling (PPARA, SLC27A1, FABP3, and DBI), unsaturated fatty acid synthesis (FADS1, FADS2, SCD, and SCD5), and fatty acid metabolism (FASN, FADS1, FADS2, SCD, and SCD5). Regarding biological processes, the genes upregulated in G2 were related to cholesterol biosynthesis (EBP, CYP51A1, DHCR24, and LSS), unsaturated fatty acid biosynthesis (FADS2, SCD, SCD5, and FADS1), and insulin sensitivity (INSIG1 and LPIN2). Cow-calf supplementation G2 positively affected energy metabolism and lipid biosynthesis, and thus favored the deposition of marbling fat during the postweaning period, which was shown here in an unprecedented way, by analyzing the transcriptome, genes, pathways, and enriched processes due to the use of creep feeding.

HEK293T Cells with TFAM Disruption by CRISPR-Cas9 as a Model for Mitochondrial Regulation

The mitochondrial transcription factor A (TFAM) is considered a key factor in mitochondrial DNA (mtDNA) copy number. Given that the regulation of active copies of mtDNA is still not fully understood, we investigated the effects of CRISPR-Cas9 gene editing of TFAM in human embryonic kidney (HEK) 293T cells on mtDNA copy number. The aim of this study was to generate a new in vitro model by CRISPR-Cas9 system by editing the TFAM locus in HEK293T cells. Among the resulting single-cell clones, seven had high mutation rates (67-96%) and showed a decrease in mtDNA copy number compared to control. Cell staining with Mitotracker Red showed a reduction in fluorescence in the edited cells compared to the non-edited cells. Our findings suggest that the mtDNA copy number is directly related to TFAM control and its disruption results in interference with mitochondrial stability and maintenance.

Uncovering the important role of mitochondrial dynamics in oogenesis: impact on fertility and metabolic disorder transmission

Oocyte health is tightly tied to mitochondria given their role in energy production, metabolite supply, calcium (Ca2+) buffering, and cell death regulation, among others. In turn, mitochondrial function strongly relies on these organelle dynamics once cyclic events of fusion and fission (division) are required for mitochondrial turnover, positioning, content homogenization, metabolic flexibility, interaction with subcellular compartments, etc. Importantly, during oogenesis, mitochondria change their architecture from an "orthodox" elongated shape characterized by the presence of numerous transversely oriented cristae to a round-to-oval morphology containing arched and concentrically arranged cristae. This, along with evidence showing that mitochondrial function is kept quiescent during most part of oocyte development, suggests an important role of mitochondrial dynamics in oogenesis. To investigate this, recent works have downregulated/upregulated in oocytes the expression of key effectors of mitochondrial dynamics, including mitofusins 1 (MFN1) and 2 (MFN2) and the dynamin-related protein 1 (DRP1). As a result, both MFN1 and DRP1 were found to be essential to oogenesis and fertility, while MFN2 deletion led to offspring with increased weight gain and glucose intolerance. Curiously, neither MFN1/MFN2 deficiency nor DRP1 overexpression enhanced mitochondrial fragmentation, indicating that mitochondrial size is strictly regulated in oocytes. Therefore, the present work seeks to discuss the role of mitochondria in supporting oogenesis as well as recent findings connecting defective mitochondrial dynamics in oocytes with infertility and transmission of metabolic disorders.

Catalytic inhibition of H3K9me2 writers disturbs epigenetic marks during bovine nuclear reprogramming

Orchestrated events, including extensive changes in epigenetic marks, allow a somatic nucleus to become totipotent after transfer into an oocyte, a process termed nuclear reprogramming. Recently, several strategies have been applied in order to improve reprogramming efficiency, mainly focused on removing repressive epigenetic marks such as histone methylation from the somatic nucleus. Herein we used the specific and non-toxic chemical probe UNC0638 to inhibit the catalytic activity of the histone methyltransferases EHMT1 and EHMT2. Either the donor cell (before reconstruction) or the early embryo was exposed to the probe to assess its effect on developmental rates and epigenetic marks. First, we showed that the treatment of bovine fibroblasts with UNC0638 did mitigate the levels of H3K9me2. Moreover, H3K9me2 levels were decreased in cloned embryos regardless of treating either donor cells or early embryos with UNC0638. Additional epigenetic marks such as H3K9me3, 5mC, and 5hmC were also affected by the UNC0638 treatment. Therefore, the use of UNC0638 did diminish the levels of H3K9me2 and H3K9me3 in SCNT-derived blastocysts, but this was unable to improve their preimplantation development. These results indicate that the specific reduction of H3K9me2 by inhibiting EHMT1/2 during nuclear reprogramming impacts the levels of H3K9me3, 5mC, and 5hmC in preimplantation bovine embryos.

Characterization of post-edited cells modified in the TFAM gene by CRISPR/Cas9 technology in the bovine model

Gene editing in large animal models for future applications in translational medicine and food production must be deeply investigated for an increase of knowledge. The mitochondrial transcription factor A (TFAM) is a member of the HMGB subfamily that binds to mtDNA promoters. This gene maintains mtDNA, and it is essential for the initiation of mtDNA transcription. Lately, we generated a new cell line through the disruption of the TFAM gene in bovine fibroblast cells by CRISPR/Cas 9 technology. We showed that the CRISPR/Cas9 design was efficient through the generation of heterozygous mutant clones. In this context, once this gene regulates the mtDNA replication specificity, the study aimed to determine if the post-edited cells are capable of in vitro maintenance and assess if they present changes in mtDNA copies and mitochondrial membrane potential after successive passages in culture. The post-edited cells were expanded in culture, and we performed a growth curve, doubling time, cell viability, mitochondrial DNA copy number, and mitochondrial membrane potential assays. The editing process did not make cell culture unfeasible, even though cell growth rate and viability were decreased compared to control since we observed the cells grow well when cultured in a medium supplemented with uridine and pyruvate. They also exhibited a classical fibroblastoid appearance. The RT-qPCR to determine the mtDNA copy number showed a decrease in the edited clones compared to the non-edited ones (control) in different cell passages. Cell staining with Mitotracker Green and red suggests a reduction in red fluorescence in the edited cells compared to the non-edited cells. Thus, through characterization, we demonstrated that the TFAM gene is critical to mitochondrial maintenance due to its interference in the stability of the mitochondrial DNA copy number in different cell passages and membrane potential confirming the decrease in mitochondrial activity in cells edited in heterozygosis.

The role of mitochondria in the female germline: Implications to fertility and inheritance of mitochondrial diseases

Mitochondria play a fundamental role during development of the female germline. They are fragmented, round, and small. Despite these characteristics suggesting that they are inactive, there is accumulating evidence that mitochondrial dysfunctions are a major cause of infertility and generation of aneuploidies in humans. In addition, mitochondria and their own genomes (mitochondrial DNA-mtDNA) may become damaged with time, which might be one reason why aging leads to infertility. As a result, mitochondria have been proposed as an important target for evaluating oocyte and embryo quality, and developing treatments for female infertility. On the other hand, mutations in mtDNA may cause mitochondrial dysfunctions, leading to severe diseases that affect 1 in 4,300 people. Moreover, very low levels of mutated mtDNA seem to be present in every person worldwide. These may increase with time and associate with late-onset degenerative diseases such as Parkinson disease, Alzheimer disease, and common cancers. Mutations in mtDNA are transmitted down the maternal lineage, following a poorly understood pattern of inheritance. Recent findings have indicated existence in the female germline of a purifying filter against deleterious mtDNA variants. Although the underlying mechanism of this filter is largely unknown, it has been suggested to rely on autophagic degradation of dysfunctional mitochondria or selective replication/transmission of non-deleterious variants. Thus, understanding the mechanisms regulating mitochondrial inheritance is important both to improve diagnosis and develop therapeutic tools for preventing transmission of mtDNA-encoded diseases.

Real-Time PCR Quantification of Heteroplasmy in a Mouse Model with Mitochondrial DNA of C57BL/6 and NZB/BINJ Strains

Mouse models are widely employed to study mitochondrial inheritance, which have implications to several human diseases caused by mutations in the mitochondrial genome (mtDNA). These mouse models take advantage of polymorphisms between the mtDNA of the NZB/BINJ and the mtDNA of common inbred laboratory (i.e., C57BL/6) strains to generate mice with two mtDNA haplotypes (heteroplasmy). Based on PCR followed by restriction fragment length polymorphism (PCR-RFLP), these studies determine the level of heteroplasmy across generations and in different cell types aiming to understand the mechanisms underlying mitochondrial inheritance. However, PCR-RFLP is a time-consuming method of low sensitivity and accuracy that dependents on the use of restriction enzyme digestions. A more robust method to measure heteroplasmy has been provided by the use of real-time quantitative PCR (qPCR) based on allelic refractory mutation detection system (ARMS-qPCR). Herein, we report an ARMS-qPCR assay for quantification of heteroplasmy using heteroplasmic mice with mtDNA of NZB/BINJ and C57BL/6 origin. Heteroplasmy and mtDNA copy number were estimated in germline and somatic tissues, providing evidence of the reliability of the approach. Furthermore, it enabled single-step quantification of heteroplasmy, with sensitivity to detect as low as 0.1% of either NZB/BINJ or C57BL/6 mtDNA. These findings are relevant as the ARMS-qPCR assay reported here is fully compatible with similar heteroplasmic mouse models used to study mitochondrial inheritance in mammals.

Modulation of periovulatory endocrine profiles in beef cows: consequences for endometrial glucose transporters and uterine fluid glucose levels

In beef cattle, proestrus estradiol and subsequent progesterone (P4) concentrations can regulate the endometrial characteristics and thereby determine maternal receptivity toward the embryo. However, the underlying mechanisms linking periovulatory endocrine profiles to receptivity, which is crucial to obtain pregnancy, need to be elucidated. We hypothesized that the size of the preovulatory follicle (POF) and subsequent circulating P4 concentrations, during early diestrus, modulate endometrial levels of glucose transporter transcripts and proteins, and subsequently affect the luminal glucose availability in the uterus. Therefore, follicle growth of Nelore cows was manipulated, and cows were assigned to 2 experimental groups: (1) large follicle and large corpus luteum (LF-LCL) group with a large POF and corpus luteum (CL); and (2) small follicle and small corpus luteum (SF-SCL) group with a small POF and CL. At day 7 post gonadotropin-releasing hormone induced ovulation (gonadotropin-releasing hormone treatment = day 0), animals were slaughtered (n = 18 per group), and uterine tissues and washings were collected for characterization of glucose transporters and glucose levels, respectively. The diameter of POF was larger (P < 0.05) in the LF-LCL cows compared with their SF-SCL counterparts (12.8 ± 0.4 vs 11.1 ± 0.4 mm). Furthermore, CL size (17.49 ± 0.88 vs 14.48 ± 0.52 mm) and circulating P4 concentrations at day 7 (4.5 ± 1.0 vs 3.3 ± 1.1 ng/mL, P < 0.05) were significantly higher in the LF-LCL cows compared with the SF-SCL cows. No differences (P > 0.05) were detected in gene expression patterns of SLC2A1, SLC2A3, SLC2A4, SLC2A5, SLC5A1, ATP1A2, ATP1B2, and SLC37A4. However, the protein abundance of endometrial SLC2A1was increased in the LF-LCL group compared with the SF-SCL group (P < 0.05). SLC2A1 and SLC2A4 protein products were mainly identified at the endometrial luminal and glandular epithelium membranes as well as in the endometrial stroma. Glucose concentrations in uterine washings were similar between groups. In conclusion, we provided information on the potential link between endocrine profiles and glucose transport pathways in the bovine endometrium. More specifically, our data reveal that the size of the POF, and subsequent P4 concentrations, do not functionally affect the main endometrial glucose transporter pathways or uterine fluid glucose concentrations during diestrus.

Development to term of cloned cattle derived from donor cells treated with valproic acid

Cloning of mammals by somatic cell nuclear transfer (SCNT) is still plagued by low efficiency. The epigenetic modifications established during cellular differentiation are a major factor determining this low efficiency as they act as epigenetic barriers restricting reprogramming of somatic nuclei. In this regard, most factors that promote chromatin decondensation, including histone deacetylase inhibitors (HDACis), have been found to increase nuclear reprogramming efficiency, making their use common to improve SCNT rates. Herein we used valproic acid (VPA) in SCNT to test whether the treatment of nuclear donor cells with this HDACi improves pre- and post-implantation development of cloned cattle. We found that the treatment of fibroblasts with VPA increased histone acetylation without affecting DNA methylation. Moreover, the treatment with VPA resulted in increased expression of IGF2R and PPARGC1A, but not of POU5F1. However, when treated cells were used as nuclear donors no difference of histone acetylation was found after oocyte reconstruction compared to the use of untreated cells. Moreover, shortly after artificial activation the histone acetylation levels were decreased in the embryos produced with VPA-treated cells. With respect to developmental rates, the use of treated cells as donors resulted in no difference during pre- and post-implantation development. In total, five clones developed to term; three produced with untreated cells and two with VPA-treated cells. Among the calves from treated group, one stillborn calf was delivered at day 270 of gestation whereas the other one was delivered at term but died shortly after birth. Among the calves from the control group, one died seven days after birth whereas the other two are still alive and healthy. Altogether, these results show that in spite of the alterations in fibroblasts resulting from the treatment with VPA, their use as donor cells in SCNT did not improve pre- and post-implantation development of cloned cattle.

Reference gene selection for gene expression analysis of oocytes collected from dairy cattle and buffaloes during winter and summer

Oocytes from dairy cattle and buffaloes have severely compromised developmental competence during summer. While analysis of gene expression is a powerful technique for understanding the factors affecting developmental hindrance in oocytes, analysis by real-time reverse transcription PCR (RT-PCR) relies on the correct normalization by reference genes showing stable expression. Furthermore, several studies have found that genes commonly used as reference standards do not behave as expected depending on cell type and experimental design. Hence, it is recommended to evaluate expression stability of candidate reference genes for a specific experimental condition before employing them as internal controls. In acknowledgment of the importance of seasonal effects on oocyte gene expression, the aim of this study was to evaluate the stability of expression levels of ten well-known reference genes (ACTB, GAPDH, GUSB, HIST1H2AG, HPRT1, PPIA, RPL15, SDHA, TBP and YWHAZ) using oocytes collected from different categories of dairy cattle and buffaloes during winter and summer. A normalization factor was provided for cattle (RPL15, PPIA and GUSB) and buffaloes (YWHAZ, GUSB and GAPDH) based on the expression of the three most stable reference genes in each species. Normalization of non-reference target genes by these reference genes was shown to be considerably different from normalization by less stable reference genes, further highlighting the need for careful selection of internal controls. Therefore, due to the high variability of reference genes among experimental groups, we conclude that data normalized by internal controls can be misleading and should be compared to not normalized data or to data normalized by an external control in order to better interpret the biological relevance of gene expression analysis.

Expression of PLIN2 and PLIN3 during oocyte maturation and early embryo development in cattle

In vitro-produced embryos store high lipid content in cytoplasmic lipid droplets (LD), and reduction or removal of LD has been demonstrated to improve freeze-thaw viability. The Perilipin Adipophilin Tail-interacting Protein of 47 kD (PAT) family of proteins is involved in the formation and regulation of LD in many cell types, but their presence has not been addressed either in cattle oocytes or preimplantation embryos. Therefore, this study aimed to detect the expression of PAT family transcripts (Perilipin-2 [PLIN2] and Perilipin-3 [PLIN3]) in immature and in vitro-matured (IVM) oocytes, and in in vitro-produced embryos at the stages of two to four cells, eight to 16 cells, morulae (MO), and blastocyst (BL). The expression of PLIN3 was downregulated in response to IVM, and PLIN2 was comparatively more expressed than PLIN3 in IVM oocytes (P < 0.001). During the early stages of embryo development, PLIN2 expression reached its peak at the MO stage (P < 0.001) and decreased again at the BL stage. In contrast, PLIN3 was expressed in low levels during the earliest stages of development, slightly upregulated at the MO stage (P < 0.05), and greatly increased its expression at the BL stage (15-fold; P < 0.001). PLIN3 was comparatively more expressed than PLIN2 during embryo culture in most stages analyzed (P < 0.05), except in eight- to 16-cell embryos. These results indicate that PLIN2 might be involved in the maintenance of lipid stocks necessary to support embryo development after fertilization of IVM oocytes. Also, we hypothesize that PLIN3 is the main PAT protein responsible for stabilization of LD formed in consequence of the acute lipid load seen during embryo development. We confirmed the presence of both PLIN2 and PLIN3 proteins in BL at Day 7 using immunocytochemistry: these PAT proteins colocalized with LD stained with BODIPY. PLIN3 seemed to be more ubiquitously spread out in the cytoplasm than PLIN2, consistent with the pattern seen in adipocytes. These findings suggest that both elderly (bigger) and newly formed (smaller) LD, positive for PLIN2 and PLIN3 respectively, coexist in blastocysts. To our knowledge this is the first report showing that transcripts of the PAT family are present in cattle oocytes and embryos.

Xenooplasmic transfer between buffalo and bovine enables development of homoplasmic offspring

Nuclear-mitochondrial incompatibilities may be responsible for the development failure reported in embryos and fetuses produced by interspecies somatic cell nuclear transfer (iSCNT). Herein we performed xenooplasmic transfer (XOT) by introducing 10 to 15% of buffalo ooplasm into bovine zygotes to assess its effect on the persistence of buffalo mitochondrial DNA (mtDNA). Blastocyst rates were not compromised by XOT in comparison to both in vitro fertilized embryos and embryos produced by transfer of bovine ooplasm into bovine zygotes. Moreover, offspring were born after transfer of XOT embryos to recipient cows. Buffalo mtDNA introduced in zygotes was still present at the blastocyst stage (8.3 vs. 9.3%, p = 0.11), indicating unaltered heteroplasmy during early development. Nonetheless, no vestige of buffalo mtDNA was found in offspring, indicating a drift to homoplasmy during later stages of development. In conclusion, we show that the buffalo mtDNA introduced by XOT into a bovine zygote do not compromise embryo development. On the other hand, buffalo mtDNA was not inherited by offspring indicating a possible failure in the process of interspecies mtDNA replication.

Mechanism of Trypanosoma cruzi death induced by Cratylia mollis seed lectin

Incubation of T. cruzi epimastigotes with the lectin Cramoll 1,4 in Ca(2+) containing medium led to agglutination and inhibition of cell proliferation. The lectin (50 microg/ml) induced plasma membrane permeabilization followed by Ca(2+) influx and mitochondrial Ca(2+) accumulation, a result that resembles the classical effect of digitonin. Cramoll 1,4 stimulated (five-fold) mitochondrial reactive oxygen species (ROS) production, significantly decreased the electrical mitochondrial membrane potential (Delta Psi(m)) and impaired ADP phosphorylation. The rate of uncoupled respiration in epimastigotes was not affected by Cramoll 1,4 plus Ca(2+) treatment, but oligomycin-induced resting respiration was 65% higher in treated cells than in controls. Experiments using T. cruzi mitochondrial fractions showed that, in contrast to digitonin, the lectin significantly decreased Delta Psi(m) by a mechanism sensitive to EGTA. In agreement with the results showing plasma membrane permeabilization and impairment of oxidative phosphorylation by the lectin, fluorescence microscopy experiments using propidium iodide revealed that Cramoll 1,4 induced epimastigotes death by necrosis.

The kinetics of donor cell mtDNA in embryonic and somatic donor cell-derived bovine embryos

The mechanisms controlling the outcome of donor cell-derived mitochondrial DNA (mtDNA) in cloned animals remain largely unknown. This research was designed to investigate the kinetics of somatic and embryonic mtDNA in reconstructed bovine embryos during preimplantation development, as well as in cloned animals. The experiment involved two different procedures of embryo reconstruction and their evaluation at five distinct phases of embryo development to measure the proportion of donor cell mtDNA (Bos indicus), as well as the segregation of this mtDNA during cleavage. The ratio of donor cell (B. indicus) to host oocyte (B. taurus) mtDNA (heteroplasmy) from blastomere(NT-B) and fibroblast(NT-F) reconstructed embryos was estimated using an allele-specific PCR with fluorochrome-stained specific primers in each sampled blastomere, in whole blastocysts, and in the tissues of a fibroblast-derived newborn clone. NT-B zygotes and blastocysts show similar levels of heteroplasmy (11.0% and 14.0%, respectively), despite a significant decrease at the 9-16 cell stage (5.8%; p<0.05). Heteroplasmy levels in NT-F reconstructed zygotes, however, increased from an initial low level (4.7%), to 12.9% (p<0.05) at the 9-16 cell stage. The NT-F blastocysts contained low levels of heteroplasmy (2.2%) and no somatic-derived mtDNA was detected in the gametes or the tissues of the newborn calf cloned. These results suggest that, in contrast to the mtDNA of blastomeres, that of somatic cells either undergoes replication or escapes degradation during cleavage, although it is degraded later after the blastocyst stage or lost during somatic development, as revealed by the lack of donor cell mtDNA at birth.

Increase in mitochondrial DNA quantity and impairment of oxidative phosphorylation in bovine fibroblast cells treated with ethidium bromide for 15 passages in culture

Bovine fetal fibroblast cells were treated with ethidium bromide at a low concentration for 15 passages in culture to determine its effect on mitochondrial DNA copy number and on cell metabolism. Mitochondrial membrane potential and lactate production were estimated in order to characterize cell metabolism. In addition, mitochondrial DNA ND5 in proportion to a nuclear gene (luteinizing hormone receptor) was determined at the 1st, 2nd, 3rd, 10th, and 15th passages using semi-quantitative PCR amplification. Treated cells showed a lower mitochondrial membrane potential and higher levels of lactate production compared with control cells. However, the mitochondrial DNA/nuclear DNA ratio was higher in treated cells compared with control cells at the 10th and 15th passages. This ratio changed between the 3rd and 10th passages. Despite a clear impairment in mitochondrial function, ethidium bromide treatment did not lead to mitochondrial DNA depletion. It is possible that in response to a lower synthesis of ATP, due to an impairment in oxidative phosphorylation, treated cells develop a mechanism to resist the ethidium bromide effect on mtDNA replication, resulting in an increase in mitochondrial DNA copy number.