Lipid changes of goat sperm plasma membrane during epididymal maturation
TL;DR: The altered lipid profile of the mature sperm membrane leads to changes in its fluidity that play an important role in determining the structure and functions of the biomembrane.
About: This article is published in Biochimica et Biophysica Acta.The article was published on 1991-01-30. It has received 76 citations till now. The article focuses on the topics: Sperm plasma membrane & Membrane lipids.
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TL;DR: It is shown that HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes, and that adipocytes were significantly enlarged and the size differences between cell and tissue suggests the heterogeneity of adipocytes.
Abstract: Hormone-sensitive lipase (HSL) is known to mediate the hydrolysis not only of triacylglycerol stored in adipose tissue but also of cholesterol esters in the adrenals, ovaries, testes, and macrophages. To elucidate its precise role in the development of obesity and steroidogenesis, we generated HSL knockout mice by homologous recombination in embryonic stem cells. Mice homozygous for the mutant HSL allele (HSL−/−) were superficially normal except that the males were sterile because of oligospermia. HSL−/− mice did not have hypogonadism or adrenal insufficiency. Instead, the testes completely lacked neutral cholesterol ester hydrolase (NCEH) activities and contained increased amounts of cholesterol ester. Many epithelial cells in the seminiferous tubules were vacuolated. NCEH activities were completely absent from both brown adipose tissue (BAT) and white adipose tissue (WAT) in HSL−/− mice. Consistently, adipocytes were significantly enlarged in the BAT (5-fold) and, to a lesser extent in the WAT (2-fold), supporting the concept that the hydrolysis of triacylglycerol was, at least in part, impaired in HSL−/− mice. The BAT mass was increased by 1.65-fold, but the WAT mass remained unchanged. Discrepancy of the size differences between cell and tissue suggests the heterogeneity of adipocytes. Despite these morphological changes, HSL−/− mice were neither obese nor cold sensitive. Furthermore, WAT from HSL−/− mice retained 40% of triacylglycerol lipase activities compared with the wild-type WAT. In conclusion, HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes.
560 citations
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TL;DR: A model is proposed in which phospholipid scrambling induces the formation of an apical membrane raft in the sperm head surface that enables albumin mediated efflux of cholesterol.
Abstract: Mammalian sperm cells are activated prior to fertilization by high bicarbonate levels, which facilitate lipoprotein-mediated cholesterol efflux. The role of bicarbonate and cholesterol acceptors on the cholesterol organization in the sperm plasma membrane was tested. Bicarbonate induced an albumin-independent change in lipid architecture that was detectable by an increase in merocyanine staining (due to protein kinase A-mediated phospholipid scrambling). The response was limited to a subpopulation of viable sperm cells that were sorted from the non-responding subpopulation by flow cytometry. The responding cells had reduced cholesterol levels (30% reduction) compared with non-responding cells. The subpopulation differences were caused by variable efficiencies in epididymal maturation as judged by cell morphology. Membrane cholesterol organization was observed with filipin, which labeled the entire sperm surface of non-stimulated and non-responding cells, but labeled only the apical surface area of bicarbonate-responding cells. Addition of albumin caused cholesterol efflux, but only in bicarbonate-responding cells that exhibited virtually no filipin labeling in the sperm head area. Albumin had no effect on other lipid components, and no affinity for cholesterol in the absence of bicarbonate. Therefore, bicarbonate induces first a lateral redistribution in the low cholesterol containing spermatozoa, which in turn facilitates cholesterol extraction by albumin. A model is proposed in which phospholipid scrambling induces the formation of an apical membrane raft in the sperm head surface that enables albumin mediated efflux of cholesterol.
293 citations
Cites background from "Lipid changes of goat sperm plasma ..."
...(1) Severe modifications in the lipid composition take place during this process, including a decrease in cholesterol (Rana et al., 1991; Haidl and Opper, 1997)....
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TL;DR: It was found that the He1 homolog is a major cholesterol-binding protein in the porcine epididymal fluid and the possibility that the HE1 homology is involved in the regulation of the lipid composition of the sperm membranes during the maturation in epidIDymis is discussed.
199 citations
TL;DR: In common mammals, sperm leaving the testis are incapable of fertilizing a female gamete, and when assessing sperm maturation it is necessary to establish the proportion of sperm that has completed and retained all steps of maturation necessary to achieve fertilization of oocytes under the conditions imposed.
Abstract: In common mammals, sperm leaving the testis are incapable of fertilizing a female gamete. Sperm have limited biosynthetic capability and need to minimize demand for ATP. Hence, modification of sperm to achieve their maturation requires pre-programmed cleavage of integral molecules (planned self-modification) and remodelling by action of molecules found in the suspending fluids. Most of these biocatalysts are secreted by a series of specialized regions in the epididymal epithelium, but some are provided in seminal plasma. The role of the epididymis in sperm maturation is postulated to be 'setting a series of triggers' each capable of initiating cellular changes either at emission or near or in the oocyte, and 'setting a safety' for each trigger to prevent premature occurrence of the event. The attributes required in a spermatozoon for in vitro fertilization and natural mating are different, and their expression is dependent on the site of sperm sampling. Some attributes needed for fertility are probably like an on-off switch, whereas others probably allow a gradually reduced probability of success before going to the off position (analogous to a conventional light switch and a dimmer-type light switch). All essential attributes of a spermatozoon must be expressed in a 'combined effective amount' for that cell to be fertile. Because of mixing, in any segment of the epididymal duct the population of sperm is heterogeneous in age and biological status. Thus, when assessing sperm maturation it is necessary to establish the proportion of sperm that has completed and retained all steps of maturation necessary to achieve fertilization of oocytes under the conditions imposed. In a normal animal, most sperm leaving the epididymis have a 'combined effective amount' of attributes, and the population has a high fertilizing potential.
191 citations
References
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TL;DR: The structure of the acetylated 1,2-diglycerides was determined by a combination of argentation-TLC and pancreatic lipase hydrolysis using internal standards for quantification and was accompanied by intermolecular as well as intramolecular rearrangement of the fatty acids.
Abstract: A detailed procedure for quantitative determinations of molecular species of lecithins is described and applied to several lecithins isolated from natural sources. The method is based on the conversion of lecithin to acetylated 1,2-diglycerides and analysis of these compounds by methodology used for the determination of triglyceride structure.
70 citations
TL;DR: The flow rate and composition of boar rete testis fluid were similar to those in other species studied previously, but the level of phospholipid phosphorus was slightly higher in ejaculated spermatozoa than in epididymal spermatozosa.
Abstract: The flow rate and composition of boar rete testis fluid were similar to those in other species studied previously. The total phospholipid phosphorus and phospholipid fatty acid content of boar spermatozoa decreased during maturation in the epididymis but the level of phospholipid phosphorus was slightly higher in ejaculated spermatozoa than in epididymal spermatozoa. During passage of the spermatozoa from the testis to the cauda epididymidis, loss of the major saturated acids (palmitic, 16:0, and stearic, 18:0) was extensive but partly recovered in the ejaculated spermatozoa. The mass of docosapentaenoic (22:5) and docosahexaenoic (22:6) acids tended to decrease continuously during maturation but the percentage of 22:6 by weight of total phospholipid fatty acid reached a maximum in the epididymis. Ejaculated boar spermatozoa contained considerably more phospholipid and phospholipid fatty acid than did ejaculated bull or ram spermatozoa.
68 citations
TL;DR: The previously unidentified neutral lipid present in tumor tissues has been isolated from Ehrlich ascites cells and unequivocally identified as a lipid class of glyceryl ether diesters containing various degrees of unsaturation, and ranging in approximate molecular weight from 760 to 990.
67 citations
TL;DR: It is reported that 1- O -hexadecyl-2-acetyl- sn -glycerol inhibits the growth of HL-60 cells and induces differentiation to cells resembling mononuclear phagocytes, and resulted in the virtual absence of cells resembling the original HL- 60 line.
66 citations
TL;DR: Comparison of epidermal acids with those of sebaceous glands showed that each tissue can synthesize the same kind of acids but in widely different amounts.
Abstract: Lipids from the living layer and stratum corneum of human sole epidermis were extracted, saponified and the fatty acids analyzed. The proportion of fatty acids to unsaponifiables (mainly cholesterol), was higher in the living layer than in the stratum corneum. Fatty acids of the living layer and stratum corneum of human sole epidermis comprise saturates, monoenes, dienes, traces of polyenes and α-hydroxy fatty acids. Homologs of monoenoic and dienoic fatty acids for both living layer and stratum corneum lipids have a similar distribution. C16 and C18 were major components for each type of acids. There appeared to be two clusters, especially for saturates of both living layer and stratum corneum acids. One of these clusters ranged from C12 to C20 with C16 or C18 as a maximum and the other ranged from C21 to C30 with C24 as a maximum. The proportion of saturated acids with chain length C20 and above was much higher in the stratum corneum than in the living layer. Position isomers of the monoenoic fatty acids for both the living layer and stratum corneum show a predominance of ω9 acids, due to the overwhelmingly large amount of oleic acid. Linoleic acid was by far the major component of the dienoic acids. Homolog distribution of α-hydroxy fatty acids for the living layer was similar to that of the stratum corneum and again two clusters of acids below and above C20 with maxima at C16 and C24 were noticeable. Comparison of epidermal acids with those of sebaceous glands showed that each tissue can synthesize the same kind of acids but in widely different amounts. Oxidation of palmitate and stearate could supply the necessary energy for the late stages of keratinization.
64 citations