Influence of lipids on ice formation during the freezing of cryoprotective medium

The influence of lipids on ice formation during the freezing of cryoprotective medium for the semen of rainbow trout has been studied by the cryomicroscopy technique. It was shown that the lipids extracted from marine vertebrates and liposomes from the lipids of trout sperm effectively inhibit the ice formation in cryoprotective solutions during freezing, fundamentally changing the form and size of ice crystals. At high concentrations of lipids, either the crystallization does not occur in the cryoprotective medium or, even if ice crystals are formed, they have a broken shape and blurred borders. The addition of egg yolk sligthly increases the size and essentially changes the shape of ice crystals during the freezing of solution.     

Fatty‐Acid Profile of Total and Polar Lipids in Cultured Rainbow Trout (Oncorhynchus mykiss) Raised in Freshwater and Seawater (Croatia) Determined by Transmethylation Method

Fatty acids from total lipids and polar lipids in cultured rainbow trout (Oncorhynchus mykiss) raised in seawater (SW) and freshwater (FW) were identified and quantified from the muscle samples in January, April, and July. The highest total lipid and polar lipid amounts were found in April. July contents of total lipids were low, but percent of the polyunsaturated fatty acids (PUFAs) was high in SW and FW environment (particularly n‐3 PUFAs). Variety of 17 fatty acids was identified by GC‐FID after transmethylation. The predominant fatty acids in rainbow trout from SW and FW were: docosahexaenoic acid among n‐3 PUFAs, palmitic acid among saturated fatty acids (SFAs), and oleic acid among monounsaturated fatty acids (MUFAs). Appreciably higher n‐3/n‐6 ratio was found in total lipids in April (6.40, FW fish) and in polar lipids in July (18.76; SW fish). High n‐3/n‐6 ratio in total lipids and polar lipids of rainbow trout from SW and FW, besides beneficial n‐3/n‐6 ratio in the commercial fish food, could be characteristic for the local environmental conditions (Croatia).     

Lipid profiles of sperm and seminal plasma from boars having normal or low sperm motility

Sperm plasma membrane lipids have an important role to play in determining membrane fluidity and sperm motility. The objective of the present study was to determine whether there are differences in the lipid and fatty acid (FA) composition of boar sperm and seminal plasma in the ejaculates of boars having different sperm motilities. Semen was collected from two groups of boars having normal (> 60%; n = 53) or low (< 60%; n = 53) motility sperm and the semen was evaluated for motility, morphology and vitality. The semen was then centrifuged to separate the sperm from the seminal plasma and both were kept at −20 °C until analyzed for lipid content and FA profile by gas chromatography. Total antioxidant status (TAS) of seminal plasma was determined using a commercial kit. There were differences (P ≤ 0.05) in sperm total lipids, cholesterol, saturated fatty acids (SFA), phospholipids, n-3 polyunsaturated fatty acids (PUFA), docosahexaenoic acid (DHA) and the ratio of n-6:n-3 PUFA between boars with normal and low motility sperm. Total lipids, cholesterol, phospholipids, PUFA, DHA and n-3 PUFA were positively correlated with sperm motility, viability, normal morphology and normal plasma membrane. In contrast, SFA and the ratio of n-6: n-3 PUFA were negatively correlated (P ≤ 0.05) with sperm motility, viability, normal morphology and normal plasma membranes. The TAS of seminal plasma from boars having normal motility sperm was higher (P ≤ 0.05) than that of boars having low motility sperm and TAS was positively correlated (P = 0.0001) with sperm motility, viability, normal morphology and normal plasma membranes. In summary, differences in sperm motility were related to n-3 PUFA content in the sperm plasma membrane and extracellular antioxidants in seminal plasma which protect sperm plasma membranes from lipid peroxidation during periods of oxidative stress.     

Dietary polyunsaturated fatty acids affect volume and metabolism of Drosophila melanogaster sperm

Dietary fatty acids can accumulate in sperm and affect their function in vertebrates. As Drosophila melanogaster shares several pathways of lipid metabolism and shows similar lipid‐dependent phenotypes but lacks some hormones that in vertebrates regulate lipid metabolism, there is currently no clear prediction as to how dietary fatty acids affect the sperm of D. melanogaster. We manipulated the amount and identity of dietary polyunsaturated fatty acids (PUFA) in the food of D. melanogaster males (a treatment known to affect membrane fluidity) and measured changes in sperm parameters. We found that (a) males reared on food containing PUFA‐rich, plant‐derived lipids showed a slower increase in sperm volume over male age compared to males reared on yeast‐derived lipid food which is richer in saturated fatty acids. (b) The resistance of sperm membrane integrity to osmotic stress was not altered by dietary lipid treatment, but (c) food containing yeast‐derived lipids induced a 46% higher in situ rate of production of reactive oxygen species in sperm cells. These findings show that dietary lipids have similar effects on sperm parameters in Drosophila as in vertebrates, affect some, but not all, sperm parameters and modulate male reproductive ageing. In concert with recent findings of sex‐specific seasonal variation of diet choice in the wild, our results suggest a substantial dietary impact on the dynamics of male reproduction in the wild.     

Effect of Lipid Head Groups on Double-Layered Two-Dimensional Crystals Formed by Aquaporin-0

Aquaporin-0 (AQP0) is a lens-specific water channel that also forms membrane junctions. Reconstitution of AQP0 with dimyristoyl phosphatidylcholine (DMPC) and E. coli polar lipids (EPL) yielded well-ordered, double-layered two-dimensional (2D) crystals that allowed electron crystallographic structure determination of the AQP0-mediated membrane junction. The interacting tetramers in the two crystalline layers are exactly in register, resulting in crystals with p422 symmetry. The high-resolution density maps also allowed modeling of the annular lipids surrounding the tetramers. Comparison of the DMPC and EPL bilayers suggested that the lipid head groups do not play an important role in the interaction of annular lipids with AQP0. We now reconstituted AQP0 with the anionic lipid dimyristoyl phosphatidylglycerol (DMPG), which yielded a mixture of 2D crystals with different symmetries. The different crystal symmetries result from shifts between the two crystalline layers, suggesting that the negatively charged PG head group destabilizes the interaction between the extracellular AQP0 surfaces. Reconstitution of AQP0 with dimyristoyl phosphatidylserine (DMPS), another anionic lipid, yielded crystals that had the usual p422 symmetry, but the crystals showed a pH-dependent tendency to stack through their cytoplasmic surfaces. Finally, AQP0 failed to reconstitute into membranes that were composed of more than 40% dimyristoyl phosphatidic acid (DMPA). Hence, although DMPG, DMPS, and DMPA are all negatively charged lipids, they have very different effects on AQP0 2D crystals, illustrating the importance of the specific lipid head group chemistry beyond its mere charge.     

Characterization of sperm plasma membrane properties after cholesterol modification: consequences for cryopreservation of rainbow trout spermatozoa

During cryopreservation, the cell plasma membrane faces severe perils, including lipid phase separation, solute effects, and osmotic stresses associated with ice crystallization. How the initial biophysical properties of the plasma membrane can be modulated before cryopreservation in order to influence cellular resistance to the freeze-thaw stress is addressed in this study. Rainbow trout (Oncorhynchus mykiss) spermatozoa were chosen because the lack of an acrosome in this species suppresses potential interactions of cryopreservation with capacitation. Methyl-beta cyclodextrin-induced modulation of membrane cholesterol revealed the presence of a significant cholesterol exchangeable pool in the trout sperm plasma membrane, as membrane cholesterol content could be halved or doubled with respect to the basic composition of the cell without impairing fresh sperm motility and fertilizing ability. Biophysical properties of the sperm plasma membrane were affected by cholesterol changes: membrane resistance to a hypo-osmotic stress increased linearly with membrane cholesterol whereas membrane fluidity, assessed with DPH (1,6-diphenyl-1,3,5-hexatriene) and with several spin-labeled analogues of membrane lipids, decreased. Phosphatidyl serine translocation between the bilayers was slowed at high cholesterol content. The increased cohesion of fresh trout sperm plasma membrane as cholesterol increased did not improve the fertilizing ability of frozen-thawed sperm whereas the lowest cholesterol contents impaired this parameter of sperm quality. Our study demonstrated that cholesterol induced a stabilization of the plasma membrane in rainbow trout spermatozoa, but this stabilization before cryopreservation brought no improvement to the poor freezability of this cell.     

Induction, isolation and a characterization of the lipid content of plasma vitellogenin from two Salmo species: rainbow trout (Salmo gairdneri) and sea trout (Salmo trutta)

Vitellogenin synthesis is induced in juvenile rainbow trout (Salmo gairdneri) and juvenile sea trout (Salmo trutta) by estradiol-17 beta. A purification procedure for vitellogenin from trout plasma by precipitation with MgCl2-EDTA and subsequent anion exchange chromatography on DEAE-Sephacel is described. The total lipid contents of purified rainbow trout and sea trout vitellogenins are 18 and 19%, respectively. Approximately 2/3 of the lipids are phospholipids, while the remainder consists of triglycerides and cholesterol. Phosphorus determinations on delipidated vitellogenin yield a phosphorus content of 0.63% in rainbow trout and 0.58% in sea trout vitellogenin. Native (dimeric) vitellogenins from rainbow trout and sea trout both have an apparent molecular weight of 440,000, when estimated by gel filtration on Sepharose 6B.     

Fatty-Acid Profile of Total and Polar Lipids in Cultured Rainbow Trout (Oncorhynchus mykiss) Raised in Freshwater and Seawater (Croatia) Determined by Transmethylation Method

Fatty acids from total lipids and polar lipids in cultured rainbow trout (Oncorhynchus mykiss) raised in seawater (SW) and freshwater (FW) were identified and quantified from the muscle samples in January, April, and July. The highest total lipid and polar lipid amounts were found in April. July contents of total lipids were low, but percent of the polyunsaturated fatty acids (PUFAs) was high in SW and FW environment (particularly n-3 PUFAs). Variety of 17 fatty acids was identified by GC-FID after transmethylation. The predominant fatty acids in rainbow trout from SW and FW were: docosahexaenoic acid among n-3 PUFAs, palmitic acid among saturated fatty acids (SFAs), and oleic acid among monounsaturated fatty acids (MUFAs). Appreciably higher n-3/n-6 ratio was found in total lipids in April (6.40, FW fish) and in polar lipids in July (18.76; SW fish). High n-3/n-6 ratio in total lipids and polar lipids of rainbow trout from SW and FW, besides beneficial n-3/n-6 ratio in the commercial fish food, could be characteristic for the local environmental conditions (Croatia).     

Lipid changes of goat sperm plasma membrane during epididymal maturation

Highly purified plasma membranes of maturing goat caput-, corpus- and cauda-epididymal spermatozoa were isolated by aqueous two-phase polymer methods and their lipid constituents were analysed. Phospholipid (approx. 75% w/w), neutral lipid (approx. 15% w/w) and glycolipid (approx. 10% w/w) were the major sperm membrane lipids. There was a significant decrease in the total lipids (approx. 25% w/w), phospholipid (approx. 30% w/w) and glycolipid (approx. 80% w/w) contents of sperm membrane during epididymal maturation. On the contrary, the mature cauda-sperm membrane showed greater (approx. 50% w/w) neutral lipid content than that of the immature caput sperm. Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin were the phospholipids of the sperm membrane, the former two being the major lipids. Both PC and PE fractions consisted of three species--diacyl, alkylacyl and alkenylacyl forms, the last one being the dominant species in both PC and PE. Of all the phospholipids, diacyl PE decreased most strikingly (approx. 65% w/w) during sperm maturation. The neutral lipid fraction contained sterols, wax esters, 1-O-alkyl-2,3-diacylglycerol, triacylglycerol and fatty acids. Sterols represented nearly 75% w/w of the neutral lipids and cholesterol was the major component (approx. 95% w/w) of the sterol fraction. The sperm maturity was associated with marked increase of sterol (approx. 60% w/w) and steryl ester (approx. 200% w/w) and decrease (approx. 50-65% w/w) of the other membrane-bound neutral lipids. The glycolipid was identified as monogalactosyldiacylglycerol. The fatty acid profile of the various membrane lipids underwent marked alteration during the epididymal transit of the male gametes. Cholesterol/phospholipid and saturated/unsaturated fatty acid ratios increased greatly in the maturing sperm membrane. 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.     

Orientation and conformation of lipids in crystals of transmembrane proteins

Orientational order parameters and individual dihedral torsion angles are evaluated for phospholipid and glycolipid molecules that are resolved in X-ray structures of integral transmembrane proteins in crystals. The order parameters of the lipid chains and glycerol backbones in protein crystals are characterised by a much wider distribution of orientational order than is found in fluid lipid bilayers and reconstituted lipid–protein membranes. This indicates that the lipids that are resolved in crystals of membrane proteins are mostly not representative of the entire lipid–protein interface. Much of the chain configurational disorder of the membrane-bound lipids in crystals arises from C–C bonds in energetically disallowed skew conformations. This suggests configurational heterogeneity of the lipids at a single binding site: eclipsed conformations occur also in the glycerol backbone torsion angles and the C–C torsion angles of the lipid head groups. Conformations of the lipid glycerol backbone in protein crystals are not restricted to the gauche C1–C2 rotamers found invariably in phospholipid bilayer crystals. Lipid head-group conformations in the protein crystals also do not conform solely to the bent-down conformation, with gauche–gauche configuration of the phosphodiester, that is characteristic of phospholipid bilayer membranes. Stereochemical violations in the protein-bound lipids are evidenced by ester carboxyl groups in non-planar configurations, and even in the cis configuration. Some lipids have the incorrect enantiomeric configuration of the glycerol backbone, and many of the branched methyl groups in the phytanyl chains associated with bacteriorhodopsin have the incorrect S configuration.     

The role of lipids and salts in two-dimensional crystallization of the glycine-betaine transporter BetP from Corynebacterium glutamicum

The osmoregulated and chill-sensitive glycine–betaine transporter (BetP) from Corynebacterium glutamicum was reconstituted into lipids to form two-dimensional (2D) crystals. The sensitivity of BetP partly bases on its interaction with lipids. Here we demonstrate that lipids and salts influence crystal morphology and crystallinity of a C-terminally truncated BetP. The salt type and concentration during crystallization determined whether crystals grew in the form of planar-tubes, sheets or vesicles, while the lipid type influenced crystal packing and order. Three different lipid preparations for 2D crystallization were compared. Only the use of lipids extracted from C. glutamicum cells led to the formation of large, well-ordered crystalline areas. To understand the lipid-derived influence on crystallinity, lipid extracts from different stages of the crystallization process were analyzed by quantitative multiple-precursor ion scanning mass spectroscopy (MS). Results show that BetP has a preference for fatty acid moieties 16:0–18:1, and that a phosphatidyl glycerol (PG) 16:0–18:1 rich preparation prevents formation of pseudo crystals.     

The desaturation and elongation of linolenic acid and eicosapentaenoic acid by hepatocytes and liver microsomes from rainbow trout (Oncorhynchus mykiss) fed diets containing fish oil or olive oil

The products of desaturation and elongation of [1−¹⁴C] 18:3(n − 3) and [1−¹⁴C]20:5(n − 3) were studied using hepatocytes and microsomes prepared from livers of trout maintained on diets containing either olive oil or fish oil, to establish the extent to which the formation of 22:6(n − 3) was enhanced in the absence of dietary 22:6(n − 3) and to investigate the pathway(s) of conversion of 18:3(n − 3) and 20:5(n − 3) to 22:6(n − 3). Levels of 20:5(n − 3) and 22:6(n − 3) in the total lipid of hepatocytes from trout fed olive oil were 20-fold and 10-fold, respectively, lower than in cells from trout fed fish oil. For both dietary groups, [1−¹⁴C]18:3(n − 3) was incorporated into hepatocyte lipid to a greater extent than [1−¹⁴C]20:5(n − 3). Almost 70% of the total radioactivity from [1−¹⁴C]18:3(n − 3) was recovered in hepatocyte triacylglycerols, whereas radioactivity from [1−¹⁴C]20:5(n − 3) was recovered almost equally in neutral lipids (52%) and polar lipids (48%). The products of desaturation and elongation from both labelled substrates were esterified mainly into hepatocyte polar lipids, whereas elongation products of [1−¹⁴C]18:3(n − 3) were preferentially incorporated into neutral lipids. Radioactivity recovered in the 22:6(n − 3) of polar lipids of hepatocytes from trout fed olive oil, from both ¹⁴C substrates, was approximately double that in hepatocytes from trout fed fish oil. No radioactivity from either [1−¹⁴C]18:3(n − 3) or [1−¹⁴C]20:5(n − 3) was incorporated into 22:6(n − 3) by microsomes isolated from livers from either group of fish and incubated in the presence of acetyl-CoA, malonyl-CoA, NADH, NADPH, ATP and coenzyme A. However, significant radioactivity was recovered in 24:5(n − 3) and 24:6(n − 3) from [1−¹⁴C]20:5(n − 3) and more radioactive 24:6(n − 3) accumulated in microsomes from trout fed olive oil than from trout fed fish oil. The results establish that the formation of 22:6(n − 3) from both 18:3(n − 3) and 20:5(n − 3) in hepatocytes of rainbow trout is stimulated by omitting 22:6(n − 3) from the diet and are consistent with the biosynthesis of 22:6(n − 3) in trout liver cells proceeding via 24:5(n − 3) and 24:6(n − 3) intermediates.     

Increased quality of in natura and cryopreserved semen of water buffaloes supplemented with saturated and unsaturated fatty acids from the palm oil industry

Ruminant energy supplementation with vegetable oils or fats has been standing out worldwide and oil palm processing has been receiving growing interest. This study assessed the effect of supplementation with saturated and unsaturated fatty acids from the palm oil industry on the lipid profile of seminal plasma and of the sperm membrane, as well as on the morphological and functional characteristics of raw and cryopreserved buffalo semen. Twelve purebred Murrah bulls (Bubalus bubalis) were assigned to the experimental groups and fed diets for 120 days with no added lipids (CONT, four bulls), or with an extra amount of 3% lipids from crude palm oil (PALM, four bulls), or from palm oil deodorizer distillate (PODD, four bulls). Semen was collected and cryopreserved every 15 days. The lipid composition of membranes and semen quality were determined after collections. Lipid supplementation did not impact feed intake (P>0.05). Diet enrichment with PALM increased the linoleic acid (C18:2,ω6) in seminal plasma. Lipid supplementation did not increase the polyunsaturated fatty acids in the sperm membrane composition, but significantly increased the lignoceric acid (C24:0). Cryopreserved semen of the supplemented bulls presented higher progressive motility (60.2 vs. 67.9 vs. 65.2%; P<0.05) and sperm viability detected by eosin-nigrosin staining (61.1 vs. 69.4 vs. 67.8%; P<0.05). Palm oil reduced major sperm defects in both raw (12.2 vs. 9.3 vs. 13.2%; P<0.0001) and cryopreserved semen (12.4 vs. 9.4 vs. 11.2%; P<0.0001). The lipids added to the diet did not impact the population of spermatozoa with intact plasma and acrosomal membranes (PI-/PSA-), but significantly increased the percentage of spermatozoa with high mitochondrial potential (25.6 vs. 31.5 vs. 32.0%; P=0.008). The results suggest that lipid supplementation based on crude palm oil or palm oil deodorizer distillate can be safely used to feed buffalo bulls and may increase sperm attributes related to male fertility.     

Dietary carotenoid pigment supplementation influences hepatic lipid and mucopolysaccharide levels in rainbow trout (Oncorhynchus mykiss)

We assessed the effects of dietary carotenoid pigment supplementation on liver histochemistry in the rainbow trout. One hundred and eight rainbow trout (mean mass 266 ± 10 g) were assigned to each of three replicate tanks for each of three dietary treatments; astaxanthin, canthaxanthin, or control at a target dietary inclusion of 100 mg/kg, by top-coating a pigment-free commercially extruded basal diet (Trouw Aquaculture, U.K.). Fish were fed for 3 weeks at a ration of 1.2% body mass/day, in a recirculating freshwater system maintained at 16 °C. Frozen liver sections were stained for total lipids, unsaturated lipids, glycogen, mucopolysaccharides, glycogen phosphorylase and aspartate aminotransferase. Relative amounts were measured quantitatively by image analysis. Carotenoid treatment significantly (P < 0.05) altered the total lipid profile and hepatic mucopolysaccharide contents of livers of rainbow trout. Results are discussed in relation to the catabolic potential of the liver in carotenoid pigment metabolism.     

Isolation and preliminary characteristics of β-N-acetylglucosaminidase in the sperm of Siberian sturgeon (Acipenser baerii) and rainbow trout (Oncorhynchus mykiss)

The aim of this study was to characterize the enzyme β- N -acetyglucosaminidase (β-NAGase) in the milt and spermatozoa extracts from Siberian sturgeon and rainbow trout. After ion exchange chromatography one protein peak showed β-NAGase activity in sturgeon milt plasma and sperm extracts of both species. Surprisingly, two protein peaks showing β-NAGase activity were found in rainbow trout milt plasma. The molecular mass of β-NAGase was estimated by gel filtration as 127 kDa for rainbow trout spermatozoa, 271 kDa for sturgeon spermatozoa, and 74 kDa for milt plasma from both species. The kinetic parameters were determined for milt plasma and sperm extracts. The optimum pH of the β-NAGases was 3.8 for sturgeon milt plasma, 4.4 for sturgeon sperm extract, and 4.4–4.8 for milt plasma and sperm extract from rainbow trout. K _m value of the β-NAGases was 0.212, 0.563, 0.779 m m for sturgeon milt plasma, sturgeon sperm extract or rainbow trout extract, respectively. The β-NAGase from sperm extracts in both species showed 100% activity even after incubation at 56°C by 20 min, whereas its activity was decreased to 23% in sturgeon milt plasma and to 2% in trout milt plasma.     

Influence of sex, body size, and reproduction on overwinter lipid depletion in brook trout

Expressed as percentages of total fresh body weight, lipids of brook trout Salvelinus fontinalis declined between October and April: reproductive males from 2·89 to 1·22%, reproductive females from 3·19 to 1·84%, and non-reproductive males and females from 2·75 to 2·08%. The absolute and proportional overwinter reduction in lipids among reproductive trout was more than twice that of non-reproductive trout, with reproductive males losing significantly more lipids than reproductive females. Larger reproductive individuals lost more lipids during winter, relative to body size, than smaller individuals, although such an effect was not evident among non-reproductive trout. The average overwinter reduction in lipids for reproductive males (58%), females (42%), and non-reproductive trout (24%) was negatively associated with mark-recapture estimates of overwinter survival probabilities of 0·27, 0·36, and 0·58, respectively, providing support for the hypothesis that energy is allocated to reproduction to the detriment of post-reproductive survival. Our emergent hypothesis that reproductive costs differ between sexes, and the life history consequences thereof, merit further study.     

The Na+,K+-ATP-ase Activity and Lipids of Trout and Rat Brain Cell Membranes at the Pressure of 101 Atmospheres

The effect of elevated heliox pressure (101 ATA) on activity of Na⁺,K⁺-ATP-ase and some characteristics of fatty acid composition was studied in membrane phospholipids of trout and rat brain synaptosomal and mitochondrial fractions. The Na⁺,K⁺-ATP-ase activity was shown to decrease by 25% in both fractions of the rat brain; in mitochondrial fraction of the trout brain it decreased by 47%, while in synaptosomal fraction, only by 11%. It has also been established that under experimental conditions, the unsaturation index of fatty acids of phosphatidylcholine and phosphatidylethanolamine of trout synaptosomes decreased, with no changes in these lipids in mitochondrial fraction. The phosphatidylcholine unsaturation index in rats did not practically change in both fractions, while in rat phosphatidylethanolamine it increased in mitochondrial fraction and slightly decreased in synaptosomal fraction. Thus, under conditions of high pressure the reduction of the enzyme activity is also determined, specifically, by peculiarities of the phospholipid fatty acid composition in the subcellular fractions studied. A possibility of changes of the enzyme activity as a result of transition of its lipid component from the liquid crystalline to the gel state under effect of an enhancement of lipid peroxidation under conditions of elevated pressure is discussed.     

Seasonal variations of lipid fatty acids of boreal freshwater fish species

1. The fatty acid levels of muscle and liver lipids of perch, vendace and rainbow trout (Salmo gairdneri) cultivated in the same area (for comparison) were monitored. 2. The total lipid content in the muscle of perch (Perca fluviatilis) and vendace (Coregonus albula) was less than 50% of that in rainbow trout and a seasonal variation was clear only in vendace. 3. The relative amounts of polyunsaturated fatty acids as well as omega-3 acids were higher in vendace and perch than in cultivated rainbow trouts. Arachidonic acid content was much higher in vendace and perch than in rainbow trout. The content of monoenes was considerably higher in rainbow trout than in free freshwater fish. 4. The seasonal variations in the degree of unsaturation were small in fish muscle. 5. In the muscle of rainbow trout the relative amount of polyunsaturated fatty acids diminished with the increase of total lipids.     

The development of regionalized lipid diffusibility in the germ cell plasma membrane during spermatogenesis in the mouse

The lipids and proteins of sperm cells are highly regionalized in their lateral distribution. Fluorescence recovery after photobleaching studies of sperm membrane component lateral diffusibility have shown that the sperm plasma membrane is also highly regionalized in the extents and rates of diffusion of its surface components. These studies have also shown that regionalized changes in lateral diffusibility occur during the differentiative processes of epididymal maturation and capacitation. Unlike mammalian somatic cells, sperm cells exhibit large nondiffusing lipid fractions. In this paper, we will show that both regionalized lipid diffusibility and nondiffusing lipid fractions develop with the morphogenesis of cell shape during spermatogenesis in the mouse. Pachytene spermatocytes and round spermatids show diffusion rates and the nearly complete recoveries (80-90%) typical of mammalian somatic cells. In contrast, stage 10-11 condensing spermatids, testicular spermatozoa, cauda epididymal spermatozoa, as well as the anucleate structures associated with these later stages of spermatogenesis (residual bodies and the cytoplasmic droplets of condensing spermatids and testicular spermatozoa), exhibit large nondiffusing fractions. Both the diffusion rates and diffusing fractions observed on the anterior and posterior regions of the head of stage 10-11 condensing spermatids are the same as the values obtained for these regions on testicular spermatozoa. Possible mechanisms of lipid immobilization and possible physiological implications of this nondiffusing lipid are discussed.     

Sperm motility characteristics of wild Atlantic salmon (Salmo salar L.) and sea trout (Salmo trutta m. trutta L.) as a basis for milt selection

The aim of the study was to determine the sperm motility parameters in wild Atlantic salmon and sea trout to define criteria important for selection of milt for controlled fertilisation. Parameters for these species were determined in the fish migrating into north‐western rivers of Poland at spawning time. Eight motility parameters percentage of motile sperm (MOT), curvilinear velocity (VCL), average path velocity (VAP), straight line velocity (VSL), linearity (LIN), straightness (STR), amplitude of lateral head displacement (ALH), beat cross frequency (BCF) and motility duration were subjected to computer‐assisted sperm analysis (CASA). Milt of most individuals studied representing both salmon and trout showed spermatozoa density of 12–22 × 10⁹ ml^?1 and a high percentage of motile sperm (>70%). In general, spermatozoa swim progressively with slightly curved trajectories (mean STR = 70%, LIN = 65%) and velocity VCL of 180 μm s^?1 (salmon) and 190 μm s^?1 (trout), at 10 s post‐activation. Such sperm is easily accessible in the wild populations of salmon and sea trout and is recommended for use in reproduction trials. The spermatozoa of sea trout seem to show a greater tendency to follow curvilinear trajectories than those of salmon, both in the beginning and the final phase of motion. In the first phase of motility, the values and time dependencies of the motility parameters were similar in both species. In the end phase of movement differences in LIN and BCF time dependencies were found in the samples representing the two species. In salmon the linearity and beat cross frequency remained stable in this phase, contrary to the patterns in sea trout for which LIN decreased while BCF increased in the end period of movement. Durations of movement were similar in both species (ranges of 20–40 s).