The use of a fluorescent dye, Nile red, to evaluate the lipid content of single mammalian oocytes

Lipid content and G6PDH activity in relation to ooplasm morphology and oocyte maturational competence in the domestic cat model

The aim of the study was to investigate the relationship between ooplasm morphology, lipid content, glucose-6-phosphate dehydrogenase activity (G6PDH) and maturation potential of domestic cat oocytes. Cumulus-oocyte complexes were classified according to ooplasm morphology: evenly dark (dCOC), heterogeneous/mosaic (hCOC), or light/transparent (lCOC), however only dCOCs are thought to be the best-quality, the remaining ones are usually rejected, therefore little is known about their intracellular properties. Lipid droplets (LDs) were visualized and quantified using Oil Red O. G6PDH activity was assessed before in vitro maturation (IVM), using the brilliant cresyl blue (BCB) test. IVM-control oocytes underwent IVM without BCB staining. The dCOCs and hCOCs had different patterns of LD spatial distribution, but similar amounts of lipid, although this tended towards being lower in hCOCs. Low G6PDH activity (BCB+) was observed in 74 %, 60 % and 24 % (P < 0.01) of dCOCs, hCOCs, and lCOCs, respectively. Significantly more BCB+ /oocytes than BCB-/oocytes reached the metaphase II stage in all groups. The maturation rate of BCB+ /hCOCs was higher than that of IVM/hCOC-controls (40 % v.s. 20 %, P < 0.001), and was comparable to that of BCB+ /dCOCs (54 %; P > 0.05). lCOCs were the smallest (P < 0.01), contained fewer (P < 0.01) lipids than dCOCs or hCOCs, and displayed reduced maturational potential. Overall, LD content and distribution, as well as G6PDH activity, in cat oocytes were strongly associated with ooplasm morphology and oocyte maturational competence. Deeper understanding of the intrinsic properties of oocytes with different ooplasm morphology using the domestic cat model, may be particularly important in the context of the conservation of endangered felids.

Use of membrane transport models to design cryopreservation procedures for oocytes

Oocyte cryopreservation is increasingly being used in reproductive technologies for conservation and breeding purposes. Further development of oocyte cryopreservation techniques requires interdisciplinary insights in the underlying principles of cryopreservation. This review aims to serve this purpose by: (1) highlighting that preservation strategies can be rationally designed, (2) presenting mechanistic insights in volume and osmotic stress responses associated with CPA loading strategies and cooling, and (3) giving a comprehensive listing of oocyte specific biophysical membrane characteristics and commonly used permeation model equations. It is shown how transport models can be used to simulate the behavior of oocytes during cryopreservation processing steps, i.e., during loading of cryoprotective agents (CPAs), cooling with freezing as well as vitrification, warming and CPA unloading. More specifically, using defined cellular and membrane characteristics, the responses of oocytes during CPA (un)loading were simulated in terms of temperature- and CPA type-and-concentration-dependent changes in cell volume and intracellular solute concentration. In addition, in order to determine the optimal cooling rate for slow programmable cooling cryopreservation, the freezing-induced cell volume response was simulated at various cooling rates to estimate rates with tolerable limits. For vitrification, special emphasis was on prediction of the timing of reaching osmotic tolerance limits during CPA exposure, and the need to use step-wise CPA addition/removal protocols. In conclusion, we present simulations and schematic illustrations that explain the timing of events during slow cooling cryopreservation as well as vitrification, important for rationally designing protocols taking into account how different CPA types, concentrations and temperatures affect the oocyte.

Fluorescence in neurosurgery: its therapeutic and diagnostic significance - a comprehensive review

This review provides a comprehensive overview of the therapeutic and diagnostic implications of fluorescence imaging in neurosurgery. Fluorescence imaging has become a valuable intraoperative visualization and guidance tool, facilitating precise surgical interventions. The therapeutic role of fluorescence is examined, including its application in photodynamic therapy and tumor-targeted therapy. It also explores its diagnostic capabilities in tumor detection, margin assessment, and blood-brain barrier evaluation. Drawing from clinical and preclinical studies, the review underscores the growing evidence supporting the efficacy of fluorescence imaging in neurosurgical practice. Furthermore, it discusses current limitations and future directions, emphasizing the potential for emerging technologies to enhance the utility and accessibility of fluorescence imaging, ultimately improving patient outcomes in neurosurgery.

Ex ovo omnia-why don't we know more about egg quality via imaging?

Determining egg quality is the foremost challenge in assisted reproductive technology (ART). Although extensive advances have been made in multiple areas of ART over the last 40 years, oocyte quality assessment tools have not much evolved beyond standard morphological observation. The oocyte not only delivers half of the nuclear genetic material and all of the mitochondrial DNA to an embryo but also provides complete developmental support during embryonic growth. Oocyte mitochondrial numbers far exceed those of any somatic cell, yet little work has been done to evaluate the mitochondrial bioenergetics of an oocyte. Current standard oocyte assessment in in vitro fertilization (IVF) centers include the observation of oocytes and their surrounding cell complex (cumulus cells) via stereomicroscope or inverted microscope, which is largely primitive. Additional oocyte assessments include polar body grading and polarized light meiotic spindle imaging. However, the evidence regarding the aforementioned methods of oocyte quality assessment and IVF outcomes is contradictory and non-reproducible. High-resolution microscopy techniques have also been implemented in animal and human models with promising outcomes. The current era of oocyte imaging continues to evolve with discoveries in artificial intelligence models of oocyte morphology selection albeit at a slow rate. In this review, the past, current, and future oocyte imaging techniques will be examined with the goal of drawing attention to the gap which limits our ability to assess oocytes in real time. The implications of improved oocyte imaging techniques on patients undergoing IVF will be discussed as well as the need to develop point of care oocyte assessment testing in IVF labs.

Influence of glucose and oxygen tension on the trophectoderm and the inner cell mass of in vitro produced bovine embryos

The first cell differentiation event that occurs in the embryo determines the inner cell mass (ICM) and the trophectoderm (TE). In the mouse, glucose (GLC) is essential for this process, while oxygen tension (O2) also interferes with TE formation. The roles of GLC and O2 in this event in bovine embryos are not completely elucidated. We hypothesized that the absence of glucose and a higher O2 tension negatively impact ICM and TE cell allocation in the bovine embryo. The objective of this study was to evaluate the effect of GLC within different O2 levels on the formation of the TE. In vitro-produced embryos were cultured in serum-free KSOM medium and randomly submitted to treatments on the day of IVC, according to a 2x2 factorial model, in which GLC (present [+GLC] or absent [-GLC]) and O2 (low [5%O2] or high [20%O2]) were the independent variables. Cleavage and blastocyst rates were obtained at D4 and D8, respectively. Embryos at D8 were subjected to autofluorescence analysis to quantitate NADH and FAD + or fixed for GATA3 and YAP1 immunostaining using a laser scanning confocal microscope. Total, TE, and ICM cell counts were obtained. Embryos were also harvested for gene expression quantification of GATA3, YAP1, SOX2, CDX2, TFAP2C and OCT4. Results indicate that there was an effect of O2 (p = 0.018) on cleavage rates, although no differences were observed in blastocyst rates. NADH was higher in -GLC compared to + GLC (p = 0.014) and no differences in FAD+ were observed. Total cell count data were not different between variables. There was an increase in the ICM cell count in the +GLC 5%O2 condition compared to the other three conditions. No effects of GLC, O2, or their interactions were observed on TE cell count or the TE/total cell ratio. CDX2 (p = 0.007) and TFAP2C (p = 0.038) were increased in -GLC 20%O2 compared to + GLC 20%O2. SOX2 was decreased in +GLC 20%O2 compared to + GLC 5%O2 (p = 0.027) or compared to -GLC 20%O2 (p = 0.005). GATA3, YAP1, and OCT4 genes did not present differences among conditions. In conclusion, both GLC and high oxygen tension did not impair TE formation and TE cell number, although a +GLC-low oxygen environment led to a higher number of ICM cells. Interestingly, the expression of TE-related gene CDX2 was increased in the absence of glucose within higher O2 tension. Our results implicate that according to the oxygen tension used in IVC, glucose can exert different effects on blastocyst cell allocation or gene expression.

Different Lengths of Diet Supplementation with 10% Flaxseed Alter the Hormonal Profile and the Follicular Fluid Fatty Acid Content of Fattening Gilts

The effect of 10% dietary flaxseed fed for 3 and 6 weeks on serum hormone levels of fattening gilts, the fatty acid (FA) follicular fluid (FF) composition of small and large antral follicles, and the steroidogenesis and IGF-I secretion by isolated small antral follicles and their response to regulatory hormones (LH, FSH, IGF-I) was studied using immunoassay and gas chromatography analyses. Both supplemental periods increased levels of P4 and IGF-I in blood serum. A shorter period inhibited steroidogenesis (P4, T, E2) and IGF-I secretion by small antral follicles, which was associated with decreased levels of monounsaturated FAs (MUFA) and preferred n-6 polyunsaturated FA (PUFA) metabolism. A longer period stimulated hormone secretion at elevated levels of saturated FAs (SFA) at the expense of MUFAs and PUFAs preferring the n-3 PUFA metabolism. Out of ovarian regulators, only LH and IGF-I were able to alter the secretion of steroids and IGF-I by small follicles of fattening pigs fed a basal diet. The effect of flaxseed on the secretion of follicular hormones after both supplemental periods was altered by all regulatory hormones in a dose-dependent manner. The level of SFAs and PUFAs in FF of large follicles increased with the length of flaxseed feeding, suggesting the suppression of ovulation.

Ferredoxin 1 is essential for embryonic development and lipid homeostasis

Mammalian ferredoxin 1 and 2 (FDX1/2) belong to an evolutionary conserved family of iron-sulfur cluster containing proteins and act as electron shutters between ferredoxin reductase (FDXR) and numerous proteins involved in critical biological pathways. FDX1 is involved in biogenesis of steroids and bile acids, Vitamin A/D metabolism, and lipoylation of tricarboxylic acid (TCA) cycle enzymes. FDX1 has been extensively characterized biochemically but its role in physiology and lipid metabolism has not been explored. In this study, we generated Fdx1-deficient mice and showed that knockout of both alleles of the Fdx1 gene led to embryonic lethality. We also showed that like Fdxr+/-+/-, Fdx1+/-+/- had a shorter life span and were prone to steatohepatitis. However, unlike Fdxr+/-+/-, Fdx1+/-+/- were not prone to spontaneous tumors. Additionally, we showed that FDX1 deficiency led to lipid droplet accumulation possibly via the ABCA1-SREBP1/2 pathway. Specifically, untargeted lipidomic analysis showed that FDX1 deficiency led to alterations in several classes of lipids, including cholesterol, triacylglycerides, acylcarnitines, ceramides, phospholipids and lysophospholipids. Taken together, our data indicate that FDX1 is essential for mammalian embryonic development and lipid homeostasis at both cellular and organismal levels.

Maturation and culture affect the metabolomic profile of oocytes and follicular cells in young and old mares

Introduction: Oocytes and follicular somatic cells within the ovarian follicle are altered during maturation and after exposure to culture in vitro. In the present study, we used a nontargeted metabolomics approach to assess changes in oocytes, cumulus cells, and granulosa cells from dominant, follicular-phase follicles in young and old mares. Methods: Samples were collected at three stages associated with oocyte maturation: (1) GV, germinal vesicle stage, prior to the induction of follicle/oocyte maturation in vivo; (2) MI, metaphase I, maturing, collected 24 h after induction of maturation in vivo; and (3) MIIC, metaphase II, mature with collection 24 h after induction of maturation in vivo plus 18 h of culture in vitro. Samples were analyzed using gas and liquid chromatography coupled to mass spectrometry only when all three stages of a specific cell type were obtained from the same mare. Results and Discussion: Significant differences in metabolite abundance were most often associated with MIIC, with some of the differences appearing to be linked to the final stage of maturation and others to exposure to culture medium. While differences occurred for many metabolite groups, some of the most notable were detected for energy and lipid metabolism and amino acid abundance. The study demonstrated that metabolomics has potential to aid in optimizing culture methods and evaluating cell culture additives to support differences in COCs associated with maternal factors.

A turn-on fluorescent probe for lipid-targeting imaging in human arterial aneurysm and fibrocalcific stenotic aortic valve

Fluorescence imaging techniques have shown remarkable performance in studying the biological functions of lipid droplets (LDs). However, the biological applications of the commercially available LDs probes suffer from insufficient specificity and low signal/noise ratio (SNR). Herein, we presented a novel near-infrared (NIR) lipid activatable fluorescence probe, namely Me2NND, with extremely low emission in water but significantly enhanced emission in the lipid environment. Me2NND presented good biocompatibility and impressive LDs-specific imaging ability in cells and tissues. Moreover, Me2NND has also shown good photostability and it could efficiently locate the distribution of LDs in human pathological samples of aortic aneurysms and fibrocalcific stenotic aortic valves. This study provided a novel turn-on probe Me2NND and would improve the bio-applications of LDs-specific probes.

Effects of forskolin on cryopreservation and embryo development in the domestic cat

One of the approaches to improve cryotolerance in lipid-rich embryos is to modify their lipidome in vitro. This work is aimed to study the effects of forskolin exposure on the in vitro embryo development of the domestic cat and to evaluate how the change in lipid content affects the cryopreservation results. In vitro-derived embryos were cultured with 10 μM forskolin from the 2-cell stage for 24 h or 96/168 h to the morula/blastocyst stage. Some of the embryos treated with forskolin for 24 h were cryopreserved with slow freezing, the other ones were used to characterize their developmental rates and the amount of intracellular lipids. The in vitro exposure to forskolin had a positive effect on the embryo development, as more embryos developed to the morula stage in the forskolin-treated group (92.9%) compared to the controls (64.7%) after 120 h of in vitro culture (IVC). Nile Red staining revealed a reduced amount of intracellular lipids in the forskolin-treated embryos. The percentage of embryos developed to the morula stage was lower in the frozen-thawed embryos not treated with forskolin (54.5%), but not in the frozen-thawed forskolin-treated group (63.6%) as compared to non-frozen controls (80.8%). Thus, the exposure of embryos to forskolin in vitro reduced the level of intracellular lipids and affected embryo development before and after cryopreservation.

Role of functional fatty acids in modulation of reproductive potential in livestock

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.

Nile Red and BODIPY Staining of Lipid Droplets in Mouse Oocytes and Embryos

Lipid droplets (LDs) are intracellular structures composed of hydrophobic lipids. Their amount in oocytes and embryos varies among the mammalian species and even among different strains of the same species. Here we describe a method to stain LDs, which can be applied to previously fixed mouse oocytes and embryos. This method is based on fluorescent dyes, Nile red and BODIPY, which allow visualization and quantification of LDs using conventional and confocal fluorescence microscopy.

FULL-MDS: Fluorescent Universal Lipid Labeling for Microfluidic Diffusional Sizing

Microfluidic diffusional sizing (MDS) is a recent and powerful method for determining the hydrodynamic sizes and interactions of biomolecules and nanoparticles. A major benefit of MDS is that it can report the size of a fluorescently labeled target even in mixtures with complex, unpurified samples. However, a limitation of MDS is that the target itself has to be purified and covalently labeled with a fluorescent dye. Such covalent labeling is not suitable for crude extracts such as native nanodiscs directly obtained from cellular membranes. In this study, we introduce fluorescent universal lipid labeling for MDS (FULL-MDS) as a sparse, noncovalent labeling method for determining particle size. We first demonstrate that the inexpensive and well-characterized fluorophore, Nile blue, spontaneously partitions into lipid nanoparticles without disrupting their structure. We then highlight the key advantage of FULL-MDS by showing that it yields robust size information on lipid nanoparticles in crude cell extracts that are not amenable to other sizing methods. Furthermore, even for synthetic nanodiscs, FULL-MDS is faster, cheaper, and simpler than existing labeling schemes.

Acyl-CoA:diacylglycerol acyltransferase: Properties, physiological roles, metabolic engineering and intentional control

Acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the last reaction in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG). DGAT activity resides mainly in membrane-bound DGAT1 and DGAT2 in eukaryotes and bifunctional wax ester synthase-diacylglycerol acyltransferase (WSD) in bacteria, which are all membrane-bound proteins but exhibit no sequence homology to each other. Recent studies also identified other DGAT enzymes such as the soluble DGAT3 and diacylglycerol acetyltransferase (EaDAcT), as well as enzymes with DGAT activities including defective in cuticular ridges (DCR) and steryl and phytyl ester synthases (PESs). This review comprehensively discusses research advances on DGATs in prokaryotes and eukaryotes with a focus on their biochemical properties, physiological roles, and biotechnological and therapeutic applications. The review begins with a discussion of DGAT assay methods, followed by a systematic discussion of TAG biosynthesis and the properties and physiological role of DGATs. Thereafter, the review discusses the three-dimensional structure and insights into mechanism of action of human DGAT1, and the modeled DGAT1 from Brassica napus. The review then examines metabolic engineering strategies involving manipulation of DGAT, followed by a discussion of its therapeutic applications. DGAT in relation to improvement of livestock traits is also discussed along with DGATs in various other eukaryotic organisms.

Lipid Metabolic Process Involved in Oocyte Maturation During Folliculogenesis

Oocyte maturation is a complex and dynamic process regulated by the coordination of ovarian cells and numerous extraovarian signals. From mammal studies, it is learnt that lipid metabolism provides sufficient energy for morphological and cellular events during folliculogenesis, and numerous lipid metabolites, including cholesterol, lipoproteins, and 14-demethyl-14-dehydrolanosterol, act as steroid hormone precursors and meiotic resumption regulators. Endogenous and exogenous signals, such as gonadotropins, insulin, and cortisol, are the upstream regulators in follicular lipid metabolic homeostasis, forming a complex and dynamic network in which the key factor or pathway that plays the central role is still a mystery. Though lipid metabolites are indispensable, long-term exposure to a high-fat environment will induce irreversible damage to follicular cells and oocyte meiosis. This review specifically describes the transcriptional expression patterns of several lipid metabolism–related genes in human oocytes and granulosa cells during folliculogenesis, illustrating the spatiotemporal lipid metabolic changes in follicles and the role of lipid metabolism in female reproductive capacity. This study aims to elaborate the impact of lipid metabolism on folliculogenesis, thus providing guidance for improving the fertility of obese women and the clinical outcome of assisted reproduction.

A smart probe for simultaneous imaging of the lipid/water microenvironment in atherosclerosis and fatty liver

A smart lipid droplet specific fluorescent probe (LDs-DM) with dual-emission in water (706 nm) and oil (535 nm) under single-excitation was prepared for revealing the ultra-structure of the aqueous and lipidic microenvironment in living cells, fatty liver tissues and atherosclerotic plaques without fluorescence emission crosstalk. This work is expected to provide inspiration for designing a novel probe with color switching ability.

Ferredoxin reductase and p53 are necessary for lipid homeostasis and tumor suppression through the ABCA1-SREBP pathway

p53 is known to modulate metabolism and FDXR is required for steroidogenesis. Given that FDXR is a target/regulator of p53, the FDXR–p53 axis may play a unique role in lipid metabolism. Here, we found that expression of ABCA1, a cholesterol-efflux pump, was suppressed by loss of FDXR and/or p53, leading to activation of master lipogenic regulators SREBP1/2. Accordingly, lipid droplets, cholesterol, and triglycerides were increased by loss of FDXR or p53, which were further increased by loss of both FDXR and p53. To explore the biological significance of the FDXR–p53 axis, we generated a cohort of mice deficient in Fdxr and/or Trp53. We found that Fdxr^+/−, Trp53^+/−, and Fdxr^+/−;Trp53^+/− mice had a short life span and were prone to spontaneous tumors and liver steatosis. Moreover, the levels of serum cholesterol and triglycerides were significantly increased in Fdxr^+/− and Trp53^+/− mice, which were further increased in Fdxr^+/−;Trp53^+/− mice. Interestingly, loss of Fdxr but not p53 led to accumulation of serum low-density lipoprotein. Together, our findings reveal that the FDXR–p53 axis plays a critical role in lipid homeostasis and tumor suppression.

Effects of different stimulators of cGMP synthesis on lipid content in bovine oocytes matured in vitro

Bovine oocytes and blastocysts produced in vitro are frequently of lower quality and less cryotolerant than those produced in vivo, and greater accumulation of lipids in the cytoplasm has been pointed out as one of the reasons. In human adipocytes cGMP signaling through the activation of PKG appears to be involved in lipid metabolism, and components of this pathway have been detected in bovine cumulus-oocyte complexes (COCs). The aim of this study was to investigate the influence of this pathway on the lipid content in oocytes and expression of PLIN2 (a lipid metabolism-related gene) in cumulus cells. COCs were matured in vitro for 24 h with different stimulators of cGMP synthesis. The activation of soluble guanylyl cyclase (sGC) by Protoporphyrin IX reduced lipid content (22.7 FI) compared to control oocytes (36.45 FI; P <0.05). Stimulation of membrane guanylyl cyclase (mGC) with natriuretic peptides precursors A and C (NPPA and NPPC) had no effect (36.5 FI; P>0.05). When the PKG inhibitor KT5823 was associated with Protoporphyrin IX, its effect was reversed and lipid contents increased (52.71 FI; P<0.05). None of the stimulators of cGMP synthesis affected the expression of PLIN2 in cumulus cells. In conclusion, stimulation of sGC for cGMP synthesis promotes lipolytic activities in bovine oocytes matured in vitro and such effect is mediated by PKG. However, such effect may vary depending on the stimulus received and/or which synthesis enzyme was activated, as stimulation of mGC had no effects.

Organelle targeting using a fluorescent probe that selectively penetrates the zona pellucida

The characteristics of oocytes, which are female germ cells, have not been studied using optical materials. The structural layers (zona pellucida, ZP) around oocytes make it difficult to deliver drugs aimed at treating infertility. Here, we investigated whether the fluorescent probes sulforhodamine, fluorescein 5(6)-isothiocyanate, tetramethylrhodamine isothiocyanate, cyanine 3 carboxylic acid, and cyanine 5 carboxylic acid penetrate oocytes. By targeting the ZP layer of the oocyte, the characteristics of the model drug, a fluorescent probe, were analyzed, and the position of the probe in the oocyte was confirmed for differences in the characteristics. Penetration of the ZP and delivery into the cytoplasm differed between the fluorescent probes. This was due to their different physiochemical properties, including hydrophobicity (contact angle and surface tension), surfactant activity, and electrical charge. Among the fluorescent probes delivered to cytoplasm, unlike TRITC, Cy3 and Cy5 perturbed oocyte development. These results suggest that in oocytes with high physical barriers (cell membrane, zona pellucida), the delivery efficiency can be estimated by considering the properties (molecular weight and structure, solubility and functional structure, etc.) of the drug. In addition, it suggests that an encapsulated or bound carrier of a drug with properties similar to that of a fluorescent probe can be efficiently delivered into oocytes.

Oocyte Cryopreservation in Domestic Animals and Humans: Principles, Techniques and Updated Outcomes

Oocyte cryopreservation plays important roles in basic research and the application of models for genetic preservation and in clinical situations. This technology provides long-term storage of gametes for genetic banking and subsequent use with other assisted reproductive technologies. Until recently, oocytes have remained the most difficult cell type to freeze, as the oocytes per se are large with limited surface area to cytoplasm ratio. They are also highly sensitive to damage during cryopreservation, and therefore the success rate of oocyte cryopreservation is generally poor when compared to noncryopreserved oocytes. Although advancement in oocyte cryopreservation has progressed rapidly for decades, the improvement of cryosurvival and clinical outcomes is still required. This review focuses on the principles, techniques, outcomes and prospects of oocyte cryopreservation in domestic animals and humans.

Mannosylation of pH-sensitive liposomes promoted cytoplasmic delivery of protein to macrophages: green fluorescent protein (GFP) performed as an endosomal escape tracer

Conventional non-pH-sensitive liposomes for cytoplasmic delivery of protein suffer from poor efficiency. Here we investigated mannosylated pH-sensitive liposomes (MAN-PSL) for cytoplasmic delivery of protein to macrophages RAW 264.7 using PSL and non-pH-sensitive liposomes for comparison. We characterised the pH-dependent fluorescence of green fluorescent protein (GFP) and encapsulated it in liposomes as an intracellular trafficking tracer. GFP showed a reversed 'S'-shaped pH-fluorescence curve with a dramatic signal loss at acidic pH. GFP stored at 4 °C with light protection showed a half-life of 10 days (pH 5-8). The entrapment efficiency of GFP was dominated by the volume ratio of intraliposomal core to external medium for thin-film hydration. Mannosylation did not affect the pH-responsiveness of PSL. Confocal microscopy elucidated that mannosylation promoted the cellular uptake of PSL. For both these liposomes, the strongest, homogeneously distributed GFP fluorescence in the cytoplasm was found at 3 h, confirming efficient endosomal escape of GFP. Conversely, internalisation of non-pH-sensitive liposomes was slow (peaked at 12 h) and both Nile Red and GFP signals remained weak and punctuated in the cytosol. In conclusion, GFP performed as a probe for endosome escape of liposomal cargo. Mannosylation facilitated the internalisation of PSL without compromising their endosomal escape ability.

Cytotoxic activity of cholesterol oxidase produced by Streptomyces sp. AKHSS against cancerous cell lines: mechanism of action in HeLa cells

Re-occurrence of cancer is the major drawback for the currently available anticancer therapies. Therefore, study of an efficient enzyme, cholesterol oxidase produced by various kinds of microbes especially obtained from unexplored marine actinobacterial species against human cancer cell lines and understanding its mechanism of action helps to identify an irreversible and potent anticancer agent. The cytotoxic potential of cholesterol oxidase produced by a marine Streptomyces sp. AKHSS against four different human cancer cell lines was demonstrated through MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. Fluorescent confocal microscopy and flow cytometry based experiments were performed to understand the efficiency of the enzymatic action on HeLa cells. Further, the apoptotic related proteins were detected through western blotting. Interestingly, the enzyme exhibited potent cytotoxicity at very low concentrations (0.093-0.327 µM) against all the cells tested. Fluorescent confocal microscopy revealed the morphological variations induced by the enzyme on cancer cell lines such as the formation of lipid droplets and condensation of nuclei. The enzyme treated cell-free extracts of HeLa cells analyzed through gas chromatography mass spectrometry showed the depletion of membrane cholesterol and the presence of substituted enzyme oxidized product, cholest-4-ene-3-one. The enzyme had induced significant inhibitory effects on the cell viability such as cell cycle arrest (G₁ phase), apoptosis and rise of reactive oxygen species as evident through flow cytometry. Besides, hyperpolarization of mitochondrial membrane, reduced rates of phosphorylation of pAkt and the expression of apoptotic death markers like Fas, Fas L, caspases (8 and 3) and PARP-1 were recorded in the enzyme treated HeLa cells. Thus, cholesterol oxidase purified from a marine Streptomyces sp. AKHSS exhibits potent cytotoxicity at very low concentrations against human cancer cell lines. All the ex vivo experiments portrayed the substantial inhibitory effect of the enzyme on HeLa cells suggesting that cholesterol oxidase of Streptomyces sp. AKHSS could be a prominent cancer chemotherapeutic agent.

Mechanisms of lipid metabolism promoted by berberine via peroxisome proliferator-activated receptor gamma during in vitro maturation of porcine oocytes

This study was conducted to explore the molecular mechanisms of berberine (Ber) via peroxisome proliferator-activated receptor gamma (PPARG) in promoting in vitro maturation (IVM) and lipid metabolism of porcine oocytes. Our results showed that expression changes in PPARG influenced IVM and the lipid droplet content of porcine oocytes. Moreover, c-Jun-N-terminal kinase (JNK) inhibitor modified the effect of PPARG agonist on IVM and lipid droplet content of porcine oocytes, and Ber significantly reduced lipid droplet content. Activation of PPARG upregulated the transcription level of microRNA-192 (miR-192), significantly promoted the expression of fatty acid binding protein 3 (FABP3) and steroid regulatory element binding transcription factor 1 (SREBF1) and PPARG, inhibited phosphorylation of PPARG, and enhanced JNK phosphorylation. Ber and overexpression of miR-192 upregulated the transcription level of miR-192 in porcine oocytes; significantly decreased the expression of FABP3, SREBF1, and PPARG; increased PPARG phosphorylation; and inhibited JNK phosphorylation. Otherwise, JNK inhibitor reduced the effects of PPARG agonist. In conclusion, Ber may activate the expression of miR-192, downregulate the expression level of PPARG and lipid synthesis-related genes, increase PPARG phosphorylation, and reduce JNK phosphorylation to enhance lipid metabolism, which is beneficial to improve porcine oocyte quality of IVM.

Distribution and size of lipid droplets in oocytes recovered from young lamb and adult ovine ovaries

This study evaluated the distribution and size of lipid droplets (LDs) in oocytes recovered from young and adult ovine ovaries. Collected oocytes were categorised on the basis of their major diameter (small (SO), 70-90 µm; medium (MO), >90-110 µm; large (LO), >110-130µm) and were stained with Nile red to detect LDs. In adult and young oocytes, a diffuse pattern distribution of LDs was dominant in all classes except adult LO and young SO and LO. Larger LDs (i.e. >3µm) were mostly present in young SO and LO, whereas smaller LDs (1-3µm) were detected in the other adult and young oocyte categories.

Comparison of Different Materials for Self-Pressurized Vitrification of Feline Oocytes-First Results

Cryobanking is a crucial part on species conservation. Nowadays, there is no suitable protocol for vitrification of feline oocytes. Self-pressurized rapid freezing of different cell types proved to mimic the advantages of high pressure freezing. As this method could also be applied for gamete rescue under field conditions, the aim here was to analyse the impact of self-pressurized vitrification on feline cumulus-oocyte-complexes (COCs) and to determine the appropriate material. Therefore, COCs of domestic cat were randomly vitrified (n = 189) in metal tubes of different materials: Aluminium, silver, and titanium. No significant differences were found on oocytes' competence after thawing. On average, 44% of the COCs presented normal morphology and 48.2% of them showed a polar body after in vitro maturation (IVM) and were subsequently fertilised. Aluminium tubes were positive on toxicity tests, producing the lowest cleavage rates. Silver tubes showed no toxic effect, but the cleavage rate was lower than with titanium tubes, and a previous association with embryotoxicity and biological alterations makes us aware of its indiscriminate use. Titanium seems to be the only inert material of them, presenting a slightly higher maturation (55.6%) and cleavage (20%) rates. Nevertheless, more studies should follow to increase embryo competence after warming.

Acetyl-CoA synthases are essential for maintaining histone acetylation under metabolic stress during zygotic genome activation in pigs

ACSS1/2 converts acetate into acetyl-coenzyme A, which contributes to histone acetylation in the mitochondria and cytoplasm. Zygotic genome activation (ZGA) is critical for embryo development involving drastic histone modification. An efficient crRNAs-Cas13a targeting strategy was employed to investigate the ACSS1/2 function during ZGA. The results showed that nuclear accumulation of ACSS1 and ACSS2 occurs during ZGA. Knockdown of ACSS1/2 did not affect blastocyst formation when using a normal medium. On culturing embryos in a medium with acetate and no pyruvate (-P + Ace), knockdown of ACSS1 did not affect histone acetylation levels but significantly reduced ATP levels, whereas knockdown of ACSS2 significantly reduced histone acetylation levels in porcine embryos. Inhibition of fatty acid beta-oxidation by etomoxir significantly reduced ATP levels, which could be restored by acetate. The histone acetylation levels in the ACSS1 and ACSS2 knockdown groups both decreased considerably after etomoxir treatment. Moreover, acetate showed dose-dependent effects on SIRT1 and SIRT3 levels when under metabolic stress. The C-terminus of ACSS1 regulated the nuclear translocation. In conclusion, ACSS1/2 helps to maintain ATP and histone acetylation levels in porcine early embryos under metabolic stress during ZGA.

Candida albicans Bgl2p, Ecm33p, and Als1p proteins are involved in adhesion to saliva-coated hydroxyapatite

Introduction: Candida albicans is an opportunistic pathogen that causes oral candidiasis. A previous study showed that Bgl2p and Ecm33p may mediate the interaction between the yeast and saliva-coated hydroxyapatite (SHA; a model for the tooth surface). This study investigated the roles of these cell wall proteins in the adherence of C. albicans to SHA beads. Methods: C. albicans BGL2 and ECM33 null mutants were generated from wild-type strain SC5314 by using the SAT1-flipper gene disruption method. A novel method based on labelling the yeast with Nile red, was used to investigate the adherence. Results: Adhesion of bgl2Δ and ecm33Δ null mutants to SHA beads was 76.4% and 64.8% of the wild-type strain, respectively. Interestingly, the adhesion of the bgl2Δ, ecm33Δ double mutant (87.7%) was higher than that of both single mutants. qRT-PCR analysis indicated that the ALS1 gene was over-expressed in the bgl2Δ, ecm33Δ strain. The triple null mutant showed a significantly reduced adherence to the beads, (37.6%), compared to the wild-type  strain. Conclusion: Bgl2p and Ecm33p contributed to the interaction between C. albicans and SHA beads. Deletion of these genes triggered overexpression of the ALS1 gene in the bgl2Δ/ecm33Δ mutant strain, and deletion of all three genes caused a significant decrease in adhesion.

Alteration of the lipid phase transition during mouse embryos freezing after in vitro culture with linoleic acid

Lipids significantly affect embryo cryopreservation in some mammalian species depending on the cell lipidome quantity and composition. One of the ways to study the relationship between lipid content and cryotolerance of cells is to study the effect of lipidome modification on laboratory mice. The objective of this research was to study how in vitro culture of mouse embryos with linoleic acid (LA) will affect lipid phase transition (LPT) during cooling and subsequent embryo development after cryopreservation. Embryos obtained in vivo at the 2-cell stage were cultured with 200 μM LA for 46 h up to the morula/blastocyst stage. Thereafter, one portion of embryos was slowly frozen to reveal the effect of LA on survival after cryopreservation, another portion was used to characterize the lipid composition and to determine the temperature of the LPT onset. Confocal fluorescence microscopy of Nile Red stained embryos showed a significant increase in lipid content of the LA treated group compared to the controls. Raman measurements showed that the onset of LPT in LA treated embryos is lower than in untreated ones: -5 °C vs +2 °C. However, these changes in the LPT onset did not affect the survival rates of embryos after cryopreservation. In summary, in vitro culture with LA changes the biophysical characteristics of embryos' lipidome and is realized in lower LPT onset, but this does not affect embryo survival after cryopreservation.

Oocyte Selection for In Vitro Embryo Production in Bovine Species: Noninvasive Approaches for New Challenges of Oocyte Competence

Simple Summary

The efficiency of producing embryos using in vitro technologies in cattle species remains lower when compared to mice, indicating that the proportion of female gametes that fail to develop after in vitro manipulation is considerably large. Considering that the intrinsic quality of the oocyte is one of the main factors affecting embryo production, the precise identification of noninvasive markers that predict oocyte competence is of major interest. The aim of this review was to explore the current literature on different noninvasive markers associated with oocyte quality in the bovine model. Apart from some controversial findings, the presence of cycle-related structures in ovaries, a follicle size between 6 and 10 mm, a large slightly expanded investment without dark areas, large oocyte diameter (>120 microns), dark cytoplasm, and the presence of a round and smooth first polar body have been associated with better embryonic development. In addition, the combination of oocyte and zygote selection, spindle imaging, and the anti-Stokes Raman scattering microscopy together with studies decoding molecular cues in oocyte maturation have the potential to further optimize the identification of oocytes with better developmental competence for in vitro technologies in livestock species.

Abstract

The efficiency of producing embryos using in vitro technologies in livestock species rarely exceeds the 30–40% threshold, indicating that the proportion of oocytes that fail to develop after in vitro fertilization and culture is considerably large. Considering that the intrinsic quality of the oocyte is one of the main factors affecting blastocyst yield, the precise identification of noninvasive cellular or molecular markers that predict oocyte competence is of major interest to research and practical applications. The aim of this review was to explore the current literature on different noninvasive markers associated with oocyte quality in the bovine model. Apart from some controversial findings, the presence of cycle-related structures in ovaries, a follicle size between 6 and 10 mm, large number of surrounding cumulus cells, slightly expanded investment without dark areas, large oocyte diameter (>120 microns), dark cytoplasm, and the presence of a round and smooth first polar body have been associated with better competence. In addition, the combination of oocyte and zygote selection via brilliant cresyl blue (BCB) test, spindle imaging, and the anti-Stokes Raman scattering microscopy together with studies decoding molecular cues in oocyte maturation have the potential to further optimize the identification of oocytes with better developmental competence for in-vitro-derived technologies in livestock species.

Effects of a high-fat diet on the lipid profile of oocytes in mice

Существуют предпосылки того, что у женщин с ожирением возможно снижение качества ооцитов. При этом остается неясным, как связано это изменение с ожирением: опосредованно или напрямую, че- рез изменение содержания и/или состава липидов в ооцитах. Целью настоящей работы было изучение на мышах влияния богатой жирами диеты, применяемой к самкам-донорам, на качественный состав и общее количество липидов в незрелых и созревших in vivo ооцитах. Установлено, что диета, богатая липидами, при- водит к увеличению массы тела самок мышей по сравнению с контролем ( p < 0.001; 44.77 ± 1.46 и 35.22 ± 1.57 соответственно), а также уровня холестерина ( p < 0.05; 2.06 ± 0.10 и 1.78 ± 0.10 соответственно) и триглицери- дов ( p < 0.05; 2.13 ± 0.23 и 1.49 ± 0.21 соответственно) в крови этих животных. Эта диета не повлияла на степень ненасыщенности внутриклеточных липидов незрелых (0.207 ± 0.004 в эксперименте и 0.206 ± 0.002 в контроле) и зрелых ооцитов (0.212 ± 0.005 в эксперименте и 0.211 ± 0.003 в контроле). При созревании ооцитов in vivo на- блюдалось возрастание содержания внутриклеточных липидов. В зрелых ооцитах количество липидов было больше в экспериментальной группе по сравнению с контролем ( p < 0.01; 8.15 ± 0.37 и 5.83 ± 0.14 соответствен- но). Выявлено увеличение количества внутриклеточных липидов при созревании ооцитов как после стан- дартной диеты ( p < 0.05; 4.72 ± 0.48 и 5.83 ± 0.14 соответственно), так и после диеты, богатой жирами ( p < 0.001; 3.45 ± 0.62 и 8.15 ± 0.37 соответственно). Таким образом, при созревании ооцитов мышей in vivo возрастает со- держание внутриклеточных липидов, богатая жирами диета приводит к повышенному содержанию липидов в зрелых ооцитах.

Assisted reproductive technologies for endangered species conservation: developing sophisticated protocols with limited access to animals with unique reproductive mechanisms

Assisted reproductive technologies (ARTs) have been proposed as a means of overcoming the significant challenges of managing small, isolated populations of endangered species in zoos. However, efficient protocols for ARTs do not exist for most endangered species. This review will focus on research efforts to characterize unique reproductive mechanisms and develop species-specific ARTs. Central to these studies are assays to measure steroid metabolites in urine or feces and/or training programs to allow unrestrained blood collections and ultrasound evaluations. The resulting information about estrous cycle dynamics, combined with studies of semen collection and processing, provides the foundation for the development of artificial insemination (AI). In vitro fertilization and embryo transfer are also discussed in relation to the advantages these techniques could provide relative to AI, as well as the significant challenges involved with technologies that require oocytes and embryos. Finally, an argument is made for additional research of nontraditional model species (e.g., domestic cats and dogs) and the development of novel models representing unique taxa. Whether these species are studied by zoo-based researchers with the expressed intent of developing ARTs for conservation or academic scientists interested in basic biology, the resulting information will provide a unique, evolutionary perspective on reproduction that could have wide-reaching benefits. The more information we have available, the better our chances will be of developing effective ARTs and making a difference in conservation efforts for endangered species.

A novel culture medium with reduced nutrient concentrations supports the development and viability of mouse embryos

Further refinement of culture media is needed to improve the quality of embryos generated in vitro. Previous results from our laboratory demonstrated that uptake of nutrients by the embryo is significantly less than what is supplied in traditional culture media. Our objective was to determine the impact of reduced nutrient concentrations in culture medium on mouse embryo development, metabolism, and quality as a possible platform for next generation medium formulation. Concentrations of carbohydrates, amino acids, and vitamins could be reduced by 50% with no detrimental effects, but blastocyst development was impaired at 25% of standard nutrient provision (reduced nutrient medium; RN). Addition of pyruvate and L-lactate (+PL) to RN at 50% of standard concentrations restored blastocyst development, hatching, and cell number. In addition, blastocysts produced in RN + PL contained more ICM cells and ATP than blastocysts cultured in our control (100% nutrient) medium; however, metabolic activity was altered. Similarly, embryos produced in the RN medium with elevated (50% control) concentrations of pyruvate and lactate in the first step medium and EAA and Glu in the second step medium were competent to implant and develop into fetuses at a similar rate as embryos produced in the control medium. This novel approach to culture medium formulation could help define the optimal nutrient requirements of embryos in culture and provide a means of shifting metabolic activity towards the utilization of specific metabolic pathways that may be beneficial for embryo viability.

Early cell-autonomous accumulation of neutral lipids during infection promotes mycobacterial growth

Lipids represent an important source of nutrition for infecting mycobacteria, accumulating within the necrotic core of granulomas and present in foamy macrophages associated with mycobacterial infection. In order to better understand the timing, process and importance of lipid accumulation, we developed methods for direct in vivo visualization and quantification of this process using the zebrafish-M. marinum larval model of infection. We find that neutral lipids accumulate cell-autonomously in mycobacterium-infected macrophages in vivo during early infection, with detectable levels of accumulation by two days post-infection. Treatment with ezetimibe, an FDA-approved drug, resulted in decreased levels of free cholesterol and neutral lipids, and a reduction of bacterial growth in vivo. The effect of ezetimibe in reducing bacterial growth was dependent on the mce4 operon, a key bacterial determinant of lipid utilization. Thus, in vivo, lipid accumulation can occur cell-autonomously at early timepoints of mycobacterial infection, and limitation of this process results in decreased bacterial burden.

A Comparative Analysis of Oocyte Development in Mammals

Sexual reproduction requires the fertilization of a female gamete after it has undergone optimal development. Various aspects of oocyte development and many molecular actors in this process are shared among mammals, but phylogeny and experimental data reveal species specificities. In this chapter, we will present these common and distinctive features with a focus on three points: the shaping of the oocyte transcriptome from evolutionarily conserved and rapidly evolving genes, the control of folliculogenesis and ovulation rate by oocyte-secreted Growth and Differentiation Factor 9 and Bone Morphogenetic Protein 15, and the importance of lipid metabolism.

Adsorption of Nile Red Self-Assembled Monolayers on Au(111)

The ability of Nile Red to self-assemble into supramolecular packings on Au(111) was studied using scanning tunneling microscopy and modeled through theoretical semiempirical calculations. At both submonolayer (sub-ML) and ML coverages, two distinct molecular packings, that is, four-leaf clover and dense chain, were observed, both weakly interacting with the underlying metal surface. Theoretical calculations suggested that the dipole moment plays a subtle role in both molecular assemblies, held together by hydrogen bonds between the Nile Red molecules. Furthermore, although both molecular assemblies were observed in as-deposited samples, a mild thermal annealing caused the transition from the four-leaf clover to the dense-chain packing, pointing out the greater stability of the dense-chain configuration. The study further emphasized how the established interactions between the Nile Red molecules are strongly influenced by the surrounding environment.

Importance of lipid metabolism on oocyte maturation and early embryo development: Can we apply what we know to buffalo?

The knowledge about the biological events that regulate lipid metabolism in oocytes and embryos in buffalo is scarce. Lipogenesis, lipolysis, transport and oxidation of fatty acids (FAs) occur in gametes and embryonic cells of all mammalian species, as an intrinsic component of energy metabolism. In oocytes and cumulus cells, degradation of lipids is responsible for the production of ATP that is essential for the metabolic processes that lead to oocyte maturation in in vivo and in vitro culture conditions. Similarly, throughout embryo development, blastomeres have the capacity to use exogenous and/or endogenous lipid reserves to serve as an energy source necessary for early embryonic development. In addition, supplementation of culture media with L-carnitine to promote lipid metabolism during in vitro oocyte maturation and early embryonic development leads to an improved embryo quality. The limited scientific evidence available in buffalo indicates there is relatively greater oocyte lipid content as compared with many other species that undergoes a dynamic distribution during folliculogenesis and follicle maturation and that has a positive effect on oocyte maturation and embryo development when there is L-carnitine supplementation of the media. Advances in the understanding of the biological peculiarities of lipid metabolism, and the consequences of its alteration on the quality of buffalo gametes and embryos, therefore, are necessary to design specific culture media and laboratory procedures as a strategy to increase in vitro-derived embryo production rates.

Neutral Lipid Content in Lipid Droplets: Potential Biomarker of Cordycepin Accumulation in Cordycepin-Producing Fungi

To clarify the relationship between neutral lipid content and cordycepin accumulation in Cordyceps militaris, mutants were generated from mixed spores of two C. militaris strains with varying cordycepin-producing capacities. Fifteen stable mutants producing from 0.001 to 2.363 mg/mL cordycepin were finally selected. The relative fluorescence intensities of the 15 mutants, two C. militaris strains and an Aspergillus nidulans strain at different concentrations of lyophilized mycelium powder were then investigated using the Nile red method. The mutant CM1-1-1 with the highest relative fluorescence intensity among the eighteen strains was selected for optimizing the Nile red method. Relative fluorescence intensity was linearly correlated with cordycepin concentration in liquid broth (R² = 0.9514) and in lyophilized mycelium powder (R² = 0.9378) for the 18 cordycepin-producing strains under identical culture conditions and with cordycepin concentration in liquid broth (R² = 0.9727) and in lyophilized mycelium powder (R² = 0.9613) for CM1-1-1 under eight different sets of conditions. In addition, the cordycepin content in lyophilized mycelium powder measured by the Nile red method was linearly correlated with that determined by an HPLC method (R² = 0.9627). In conclusion, neutral lipids in lipid droplets are required during cordycepin accumulation; these neutral lipids are potential biomarkers of cordycepin biosynthesis.

Preparation of Fluorescence-Encoded Microspheres Based on Hydrophobic Conjugated Polymer-Dye Combination and the Immunoassay

Fluorescent microspheres are greatly demanded in many applications based on high-throughput suspension array technology. To realize the multiplexed assay, microspheres should be encoded to identify the interaction between analytes and spheres. This study advanced a strategy for preparing fluorescence-encoded microspheres, employing two hydrophobic fluorophores, poly(p-phenyleneethylene) (PPE), and Nile Red (NR), as well as the monodisperse amino-modified porous substrate polymeric spheres, poly(glycidyl methacrylate) microspheres (APGMA). Loading the fluorophores sequentially onto the substrate spheres via adsorption by immersing the spheres in the dipping solution of fluorophores resulted in the APGMA-PPE-NR spheres. By varying the concentration and combination of fluorophores in the solution, an array of 64-code APGMA-PPE-NR spheres was obtained and could be easily individually decoded via flow cytometry. A 2D dot plot from the flow cytometry of a set of mixed spheres with four different codes could also be differentiated, coincident with the overlaid plots of the spheres' corresponding codes but measured individually. These spheres were found to have good stability against washing, photobleaching, and thermal treatment. In addition, a sandwich immunoassay for the detection of goat IgG was performed, and the capability of the encoded spheres to be used in suspension array technology was demonstrated.

Updating the Impact of Lipid Metabolism Modulation and Lipidomic Profiling on Oocyte Cryopreservation

Oocyte cryopreservation has drastically improved in recent years and is receiving widespread clinical use with increasing demand for fertility preservation and assisted reproduction treatments. However, there are still several points to be reviewed in terms of suppressing sub-lethal damages and improving overall safety, especially when trying to preserve oocytes at the germinal vesicle stage or oocytes matured in vitro. The lipid content of oocytes is highly associated with both their competence and cryotolerance. Differences in lipid content are observed not just between different species but also at different developmental stages and when the oocytes are kept under different conditions, including cryopreservation. Many efforts have been made to understand how physiological or in vitro alterations in the lipid profile of oocytes impacts cryotolerance and vice-versa; however, the dynamics of cytosolic and membrane lipid involvement in the cryopreservation process remains poorly clarified in the human female gamete. This review presents an updated overview of the current state of cryopreservation techniques and oocyte lipidomics and highlights possible ways to improve cryotolerance, focussing on lipid content modulation.

Evaluation of Bacterial Lipid Production: Quantitative and Qualitative Measurements: Tips and Guidelines

Over the last decade, finding bacterial strains with ability to accumulate high concentrations of lipids has gained increasing interest, since these lipids may be used in different industries. Here we describe two methods for evaluation of lipid accumulation in cyanobacteria, following by our personal reflection on issues surrounding the use of these methods. First, we present the Bligh and Dyer protocol as a traditional extraction method using organic solvents for quantitative determination of lipids and next Nile red, a selective fluorescent stain, that has been used as a rapid approach for both qualitative and quantitative measurement of lipids.

Lipid droplets in clusters negatively affect Bos indicus embryos during cryopreservation

Embryo transfer using cryopreserved B. indicus embryos results in low pregnancy rates. The low viability of B. indicus embryos is likely a result of their low freezability relative to embryos from other species, notably B. taurus. Freezability is probably related to the quantity of lipid droplets in the embryonic cells. However, the mechanism underlying this association is unknown. Using multiphoton and transmission electron microscopy, the proportion, volume, morphology and composition of lipid droplets in fresh and cryopreserved B. indicus and B. taurus embryos were studied. B. indicus embryos have more droplets than B. taurus and a greater percentage of lipid droplets in clusters (34% vs. 24%; p < 0.05). Also, B. indicus individual droplets are of greater volume than those of B. taurus (47 μm³ vs. 34 μm³ ; p < 0.05). After freezing, the percentage of clusters decreased in B. indicus (11% vs. 5%; p < 0.05), while in B. taurus they increased (2% vs. 7%; p < 0.05). Freezing influenced the lipid droplet morphology, increasing the number of cracked droplets in B. indicus embryos (33% fresh vs. 62% frozen; p < 0.05), but not in B. taurus embryos (35% fresh vs. 34% frozen; ns). Regarding composition, saturated lipid droplets prevail in B. indicus embryos, contrary to B. taurus embryos. We observed differences in lipid droplet organization, proportion, volume, morphology and composition between B. indicus and B. taurus embryos which are altered in opposite directions following freezing.