Interaction of free fatty acids with the erythrocyte membrane as affected by hyperthermia and ionizing radiation

The interference of hyperthermia and ionizing radiation, respectively, with the effects of capric (100), lauric (120), myristic (140), oleic (cis-181) and elaidic (trans-181) acids on the osmotic resistance of human erythrocytes was investigated. The results are summarized as follows: (A) not only at 37°, but also at 42° and 47°C lauric acid (120) represents the minimum chain length for the biphasic behaviour of protecting against hypotonic hemolysis at a certain lower concentration range and hemolysis promotion at subsequent higher concentrations; (B) with increasing temperatures the protecting as well as the hemolytic effects occur at lower concentrations of the fatty acids; (C) the increase of temperature promotes the extent of hemolysis and reduces the extent of protection against hypotonic hemolysis; (D) Gamma-irradiation of erythrocytes selectively affects the concentration of oleic acid at which maximum protection against hypotonic hemolysis occurs, without altering the minimum concentration for 100% hemolysis.     

Correlations between gametophytic (pollen) and sporophytic (seed) generations for polyunsaturated fatty acids in oilseed rape Brassica napus L.

Summary Lipids were extracted from the diploid seed and haploid pollen of Brassica napus L. Two fractions of pollen lipids, namely the diploid-specified pollen-coat and the haploid-specified internal cytoplasmic lipids were obtained. Significant correlations exist between pollen and seed generations for linoleic (182) and linolenic (183) acids. In pollen internal storage lipids, the level of 183 is positively correlated and the level of 182 is negatively correlated with the level of 183 in seed lipids. Evidence is presented that strongly supports the hypothesis that lipid biosynthesis occurs within the pollen and that synthesis is specified by haploid genes. These data support the concept of pollen selection, so that selecting among living pollen grains for superior individuals has potential as a new plant breeding tool for improving seed oil quality.     

Influence of photoperiod,temperature and host plant on the production of diapause eggs inPetrobia (Tetranychina) harti (Acari: Tetranychidae)

Petrobia harti (Ewing) diapauses in the egg stage. Adult females lay either diapause or nondiapause eggs. On the University of Thessaloniki campus (41°N), the mite was found to develop on leaves ofOxalis corniculata L. throughout the year, while no mites were found on leaves ofOxalis articulata Savigny growing in the same area. In the laboratory the mite could be maintained equally well on detached leaves of both plant species, kept on wet cotton-wool.Forty to 90% females laying diapause eggs (dlf) were produced when the mites developed under LD 1212 and 19±1 °C, or LD 168 and 19±1 °C or 25±1 °C on leaves ofO. articulata detached from plants grown in the open in various seasons. Under the same conditions, a very low to zero percentage ofdlf was produced onO. corniculata. By rearing certain feeding stages on one of these twoOxalis hosts, and the other feeding stages on the other host, various percentages ofdlf were obtained. These percentages were the net effect of the antagonistic action of the twoOxalis species.By rearing the mites at LD 8.515.5, LD 1212 or LD 168 and a temperature of 19±1 °C onO. articulata leaves renewed every 3 days, or every 16–18 days, or not at all, it could be shown that diapause induction or aversion is caused by the direct effect of photoperiod on the mites, and not by an effect through the host leaves.When wholeO. articulata plants were grown under LD 168 and 19±1 °C in the laboratory, or developed in the open during April and May, flowers were produced, while under LD 1212 no flowering occurred. In the laboratory under diapause-inducing conditions, higher percentages ofdlf were produced on leaves detached from flowering plants than on leaves detached from plants not flowering.OnO. articulata leaves at 20 °C, photoperiods with photophases equal to or longer than 12 h induced from 70 to 80%dlf, while photoperiods with photophases equal to or shorter than 10.9 h induced very low to zero percentages. By transferring different chrysalis stages from a diapause-inducing (LD 1212) to a diapause-averting (LD 8.515.5) photoperiod, and vice versa, it was found that the nymphochrysalis through deutonymph stages were sensitive to photoperiod, the deutochrysalis and deutonymph being the most sensitive.Under an LD 1212 photoperiod, a temperature of 20 °C induced diapause, whereas 25 °C, 30 °C, or a daynight thermoperiod of 25 °C18 °C suppressed it.     

Light exposure stimulates arachidonic acid metabolism in intact rat retina and isolated rod outer segments

This paper presents evidence that short-term exposure to light increases synthesis of hydroxyei-cosatetraenoic acid (HETE) and prostaglandin D₂ (PGD₂) and stimulates the uptake and metabolism of 204 in phospholipids and triacylglycerols in rat retina. There was a time-dependent increase in incorporation of 1-¹⁴C-204 into glycerolipids in both dark-adapted and light-exposed groups. Exposure to light for 15 or 30 min enhanced the acylation of 204 into phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and triacylglycerols. In the light-exposed groups there was a large increase in the conversion of 204 to leukotriene B₄, two diHETEs, 5-HETE, 15-HETE, and PGD₂. The stimulation of HETE synthesis by light could be due to early stages of light-induced lipid peroxidation in visual cells. To examine this, we studied peroxidation of 204 in isolated rod outer segments (ROS). There was more oxidation of 204 in light-exposed ROS, as compared to ROS incubated in the dark. Vitamin E and nordihydroguaiaretic acid inhibited the light-induced formation of some of these products. The data indicate that photo-oxidation of 204 in ROS is accompanied by enzymatic oxygenation that is stimulated by light. Increased production of HETEs and PGD₂ may be a consequence of the light-induced stimulation of the metabolism of 204 in membrane phospholipids in the retina.     

Metabolisme lipidique chez l'Aspergillus versicolor (Vuill.) tiraboschi. Relations avec la biogenese de la sterig matocystine

Résumé L' Aspergillus versicolor est cultivé sur un milieu synthétique pendant 22 jours. Les productions de lipides et de stérigmatocystine sont comparées. Les acides gras des fractions neutres et polaires sont essentiellement: C 160, C 180, C 181 C 182, et C 183. Les quantités maximales de mycélium sec, de lipides neutres et de stérigmatocystine apparaissent respectivement au 4e, 7e et 20e jours. Une diminution de la teneur en lipides précède la phase de concentration maximale en métabolites secondaires du type polycéto-acide. Il semble que les lipides, et tout particulièrement l'acide palmitique, participent à la biogenèse de ces dérivés.

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Summary Aspergillus versicolor is cultivated in a synthetic medium for 22 days. Bioproduction of lipids and sterigmatocystin are compared. The fatty acids of the neutral lipid and polar lipids fractions are mainly: C 160, C 180, C 181, C 182, C 183. Maximal yields of dry weight, neutral lipids and sterigmatocystin occur, respectively, on the 4th, the 7th and the 20th days. These results and their comparison with other works emphasize that a fall of concentration in lipids precedes the phase of highest concentration in secondary metabolites of polyketide type; it appears that fats and particularly palmitic acid are present in biogenesis of these derivatives.

     

Lipid structure and Ca2+-ATPase function

Effects of lipid structure on the function of the Ca²⁺-ATPase of skeletal muscle of sarcoplasmic reticulum are reviewed. Binding of phospholipids to the ATPase shows little specificity. Phosphatidylcholines with short (C14) or long (C24) fatty acyl chains have marked effects on the activity of the ATPase, including a change in the stoichiometry of Ca binding. Low ATPase activity in gel phase lipid follows from low rate of phosphorylation. Phosphatidylinositol 4-phosphate increases ATPase activity by increasing the rate of dephosphorylation of the phosphorylated ATPase. Stimulation is not seen with other anionic phospholipids; phosphatidic acid decreases ATPase activity in a Mg²⁺-dependent manner.Abbreviations di(C141)PC dimyristoleoylphosphatidycholine - di(C160)PC dipalmitoylphosphatidylcholine - di(C181)PC dioleoylphosphatidylcholine - di(Br₂C180)PC dibromostearoylphosphatidylcholine - di(C241)PC dinervonylphosphatidylcholine - di(C181)PA dioleoylphosphatidic acid - di(C181)PE dioleoylphosphatidylethanolamine - Ptdlns phosphatidylinositol - PtdIns-4P phos-phatidylinositol 4-phosphate     

Localization of the gene for human heart fatty acid binding protein to chromosome 1p32-1p33

Among 639 spontaneous abortions between the 8th and 14th week of gestation 342 (53.5%) revealed an abnormal karyotype. While the rate of trisomies distinctly increased with advancing maternal age, a decrease in the rate of 45,X conceptuses and polyploidies was observed among abortions from older women. The overall relation of XXXXXXYY among the tetraploidies was 1411 and that of XXXXXYXYY among the triploidies was 26 361. However, when the latter was related to maternal age, a reversal of the XXXXXY ratio of 12 in the younger to 21 in the older age groups became evident. Furthermore a decrease in the rate of paternally derived partial hydatidiform moles was found among the triploid abortion specimens from older women. From these observations we conclude that digyny plays a major role in the origin of triploidy in the increased maternal age groups, while diandry related to immaturity of oocytes and impairment of oocyte cortical function is more frequent in triploid abortions from younger women.     

Comparison of fatty acids of marine fungi using multivariate statistical analysis

Summary Ten obligate marine fungi have as their principal fatty acids 160, 180, 181n9 and 182n6. The fatty acids ranged from 14 to 22 carbons, completely dominated by those with even numbers of carbons. The amount of unsaturated fatty acids varied between 35% and 80%. Each isolate contained small amounts of the acids 183n3 and 204n6. Branched, hydroxy- or cyclic fatty acids were not detected. Multivariate statistical, i.e. principal component analysis, showed that all ten strains could be distinguished on the basis of their fatty acid composition. These results indicate that the marine fungi do not have an unusual fatty acid composition and suggest that chemometric, multivariate analysis might be employed to confirm taxonomic relationships among these organisms.     

Photoperiodic induction of the first and the second diapause in the bean bug,Riptortus clavatus: a photoperiodic history effect

Summary In nondiapause adults raised under a long-day photoperiod, the critical daylength for diapause induction was between 13 and 14 h although some individuals did not respond to the short-day photoperiod and went on laying eggs. In postdiapause adults in which LD 1311 induced the first diapause (L13 insects), the critical daylength for diapause reinduction was between 13 and 14 h, whereas it was between 12 and 13 h in postdiapause adults in which LD 1014 induced the first diapause (L10 insects). Under LD 1311, a small proportion of L10 insects went into the second diapause after great delay as compared with L13 insects. Under LD 1014, on the other hand, L10 insects went into the second diapause more rapidly than L13 insects. Therefore, the photoperiod which had induced the first diapause affected the photoperiodic induction of the second diapause not only in the critical daylength but also in the speed of response. In Riptortus clavatus, the photoperiodic history influences the subsequent photoperiodic response even after a physiological state induced by the previous photoperiod was terminated completely.Abbreviations L13 insects postdiapause adults in which LD 1311 induced the first diapause - L10 insects postdiapause adults in which LD 1014 induced the first diapause     

Novel seed lipid phenotypes in combinations of mutants altered in fatty acid biosynthesis inArabidopsis

Summary The seed fatty acid (FA) composition of various single mutant combinations ofArabidopsis thaliana that affect FA biosynthesis has been examined. Double mutant combinations offae, a mutation affecting CIS elongation, and a series of four other FA biosynthetic mutants were synthesized. The four other single mutants were:fad2 andfad3, which are deficient in 181 and 182 desaturation, respectively;fab1, which is elevated in 160 and decreased in 181; andfab2, which is elevated in 180 and decreased in 181. The superimposition of two blocks in the FA biosynthetic pathway leads to dramatic changes in the FA content of the double mutants. The tenArabidopsis stocks analyzed to date (wild-type, five single mutants, and four double mutants) make seed oils with a wide range of FA compositions, and illustrate the diversity of oils it is possible to obtain from a single plant species.     

Aflatoxin — induced alteration in the levels of membrane chemicals of subcellular organelles isolated from excised,incubated Glycine max,cv. ‘Essex’ roots

Isolates of aflatoxin-producing strains of Aspergillus grow on autoclaved and field-grown (lesser extent) Glycine max beans. Both mixed and aflatoxin B₁ inhibit G. max, cv. Essex bean germination and elongation of either attached or excised cultured roots. Because B₁ impairs the latter roots' ability to intracellularize [¹⁴C]-leucine, it may alter plasmalemma structure and/or function. To determine whether incubation of excised roots for 18 hours in toxin-containing medium could affect cellular membrane chemical content, organelles were isolated by differential centrifugation (1 000, 40 000, and 80 000 xg) of homogenates and characterized chemically. Statistically significant differences between treated and untreated roots in acid insoluble protein but not either sterol or lipid phosphorus levels were observed for both 40,000 and 80,000 xg pellets. Protein and sterol recoveries were 81 (treated) and 84 (untreated) % for the former and 77 (treated) and 79 (untreated) % for the latter. Lipid phosphorus recoveries were 87.3 (treated) and 136 (untreated) % with and 96 (treated) and 83 (untreated) without membrane stabilization. Protein:sterol:lipid phosphorus were 35.74.51 (1 000 xg), 18.93.61 (40000 xg), 26.34.61 (80 000 xg) and 1,010291 (80 000 xg supernatant) for untreated and 36.93.31 (1,000 xg), 23.13.81 (40 000 xg), 36.24.81 (80 000 xg) and 1,05321.71 (80 000 xg supernatant) for treated roots. Significant differences in RNA content between treated and untreated roots were found for both 1 000 and 40 000 xg pellets but not for the 80 000 xg pellet and its supernatant. Whereas a significant increase in the 1 000 xg pellet occurred upon treatment, a decrease was noted for the 40 000 xg pellet but not for the 80 000 xg pellet and its supernatant. Similar pH 6 (plasmalemma marker enzyme) and 9 (mitochondrial marker enzyme) K⁺-stimulated ATPase activities were demonstrated for 40 000 and 80 000 xg pellets. The 1 000 xg pellet contained greater than 50% of the NADH-cytochrome c-reductase activity (endoplasmic reticulum marker enzyme) recovered from fractions examined for this activity which was absent from the 40 000 xg pellet. Both the 80 000 xg pellet and its supernatant possessed equivalent reductase activities. Inosine diphosphatase activity (dictyosome marker enzyme) was not present in 1 000 xg pellets obtained from either treated or untreated roots but was in both 40 000 and 80 000 xg pellets. Based on these results, a tentative assignment of organelles to each fraction (xg force) is reported.Abbreviations used AFB₁ aflatoxin B₁ - AFB₂ aflatoxin, B₂ - AFG₁ aflatoxin G₁ - AFG₂ aflatoxin G₂ - ATPase adenosine triphosphatase - IDPase inosine diphosphatase - NADH reduced nicotinamide-adenine dinucleotide - PCA perchloric acid - TCA trichloroacetic acid - 2, 4-D 2,4-dichlorophenoxyacetic acid Aided by grant IN-127 from the American Cancer Society to WVD and funds from the Departments of Biology, West Virginia University and Virginia Commonwealth University as well as a Sigma Xi award to JMD.     

Circadian effects of hydrocortisone on the blood of the newt,Notophthalmus viridescens

Summary Differential counts of the leucocytes of newts,Notophthalmus viridescens, were made at four times of day (200, 900, 1400 and 2100), 72 hours after the injection of hydrocortisone acetate (experimentais) or distilled water (controls). At all times, increases in neutrophils and decreases in lymphocytes were observed in experimentais as compared to the controls (Table 1). The increases in neutrophils in the experimental newts were most pronounced at 1400, and the decreases in the lymphocytes were greatest at 2100. The least degrees of neutrophilia and lymphopenia occurred at 900. Consequently, circadian variations in response to the hydrocortisone are indicated. The possible mechanism of mediation of the variations is discussed.Supported in part by National Science Foundation grant, GY-7661, to Sweet Briar College.     

Bicuculline induces free fatty acid release from phospholipids in Neuro-2A cells in culture

This study characterizes free fatty acid release in a neuroblastoma cell line (Neuro-2A), a potential model system for the study of factors that control phospholipase A₂ in neurons. Two compounds, bicuculline (an antagonist at -aminobutyric acid receptors), and A23187 (a Ca²⁺ ionophore), were examined. The release of endogenous fatty acids and the turnover of radiolabeled arachidonic and docosahexaenoic acids were measured. The cells actively incorporated radiolabeled fatty acids into various glycerolipid pools. Both endogenous fatty acids and radiolabeled fatty acids were released from glycerolipids in a time-dependent manner. Phosphatidylcholine was a major source of released fatty acids. Release of free fatty acids was markedly stimulated by both bicuculline and A23187. We conclude that the Neuro-2A cell contain phospholipase activity that is sensitive to Ca²⁺ ionophore and bicuculline, and may provide a good system for further studies on the regulation of phospholipase A₂ in neurons.Abbteviations 160 palmitic acid - 180 stearic acid - 181 oleic acid - 182 linoleic acid - 183 linolenic acid - 204 arachidonic acid - 226 docosahexaenoic acid - DG diacylglycerol - FAME fatty acid methyl ester - FFA free fatty acid - GABA -aminobutyric acid - PA phosphatidic acid - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - TG triacylglycerol     

Structure of the majorO-glycosidic oligosaccharide of monkey erythrocyte glycophorin

Sialic acids and the majorO-glycosidic oligosaccharide of glycophorin MK from monkey (Japanese monkey,Macaca fuscata) erythrocyte membranes were characterized.N-Glycolylneuraminic acid (neu5Gc) was found as the major sialic acid, which was confirmed by gas-liquid chromatography-mass spectrometry as the trimethylsilyl methyl ester. ThreeO-glycosidic oligosaccharide units were obtained from a tryptic glycopeptide that contained all of the carbohydrate units in glycophorin MK by mild alkaline borohydride/borotritide treatment. Carbohydrate analyses of the oligosaccharides revealed that they were composed of Neu5Gc, galactose andN-acetylgalactosaminitol in the molar ratios of 111 (trisaccharide), 211 (tetrasaccharide) and 111 (pentasaccharide). The content of oligosaccharide units was estimated to be 1125 for penta-, tetra- and trisaccharide, respectively, based on the yields, the molecular weight, and the number of oligosaccharide attachment sites in the amino-acid sequence. The tetrasaccharide was the major oligosaccharide and its structure was proposed to be Neu5Gc2-3Gal1-3[Neu5Gc2-6]GalNAcol.     

Substrate and inhibitor specificity of anion exchangers on the brush border membrane of rabbit ileum

Summary In previous studies we have found that several anions can be transported by an exchange process in rabbit ileal brush border membranes. We demonstrated exchanges of Cl for OH or HCO₃, SO₄ for OH, oxalate for OH, and oxalate for Cl. The purpose of these studies was to determine the number of distinct carriers mediating these exchanges. We utilized substrate and inhibitor specificity studies to distinguish between different anion exchange transporters. We conclude that SO₄OH and oxalate: OH exchange occur on the same carrier because: (i) pH-gradient stimulated transport of both¹⁴C-oxalate and³⁵SO₄ were equally sensitive tocis-inhibition by unlabeled SO₄ or oxalate; and (ii) both were inhibited equally by K. We conclude that oxalate: OH and oxalate: Cl exchanges occur on different carriers because: (i) Cl or SO₄ caused unequalcis-inhibition of these two exchanges; and (ii) as compared to oxalate: Cl exchange, oxalate: OH exchange was more sensitive to inhibition by probenecid and K and less sensitive to inhibition by bumetanide. Finally, we conclude that oxalate: Cl exchange and ClHCO₃ exchange occur on different carriers because: (i) ClHCO₃ exchange was almost completely insensitive tocis-inhibition by oxalate; and (ii) oxalate: Cl exchange was more sensitive to inhibition by DIDS and bumetanide than ClHCO₃ exchange. Thus we have found that there are at least three separate anion exchangers on rabbit ileal brush border: (i) a ClHCO₃ exchanger; (ii) a SO₄OH exchanger, which also transports oxalate; and (iii) an oxalate: Cl exchanger.     

On age morphological changes of males of Chydoridae (Cladocera)

Summary Young and adult males of 11 species of Chydoridae are studied, their figures being published here (fig. 1–15). The necessity is stressed to distinguish young forms of males and gynandromorphic individuals.Pleuroxus balatonicus is considered to be described from the population ofPleuroxus unicatus having under Balaton Lake conditions retarded transformation of young males into adult form, and accordingly having unusually numerous young males. \qO\qs\qn\qo\qv\qn\qy\ye \qr\ye\qz\qu\ql\Qj\qt\qa\qt\qy 11 (. 1–15). . , Pleuroxus uncinatus , Pleuroxus balatonicus.     

Role of ω-3 fatty acid desaturases in the regulation of the level of trienoic fatty acids during leaf cell maturation

Trienoic fatty acids, namely -linolenic acid and hexadecatrienoic acid, present in leaf lipids are produced by -3 fatty acid desaturases located in the endoplasmic reticulum and plastid membranes. The changes in the level of trienoic fatty acids during leaf maturation were investigated in wild-type plants of Arabidopsis thaliana (L.) Heynh. and in the fad7 mutant deficient in the activity of a plastid -3 desaturase. The levels of trienoic fatty acids increased in 26 °C- and 15 °C-grown wild-type plants with maturation of leaves. The increase in trienoic fatty acids was mainly due to galactolipids enriched in plastid membranes. In addition, the relative levels of trienoic fatty acids in major glycerolipids, including phospholipids enriched in the endoplasmic reticulum membranes, also increased with leaf maturation. By contrast, when the fad7 mutant was grown at 26 °C, the relative levels of trienoic fatty acids in individual lipids decreased with leaf maturation. The decreases in the levels of trienoic fatty acids, however, were alleviated when the fad7 mutant was grown at 15 °C. These results suggest that the plastid -3 desaturase plays a major role in increasing the levels of trienoic fatty acids with leaf maturation.Abbreviations 163 hexadecatrienoic acid - 183 -linolenic acid - DGD digalactosyldiacylglycerol - MGD monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - TA trienoic fatty acid - WT wild type - -3 refers to the position of the double bond from the methyl end of a fatty acid This research was supported in part by Grants-in-Aid for Scientific research (#07251214 and #06804050 to K.I.) from the Ministry of Education, Science and Culture, Japan, and by the research grant from Shorai Foundation.     

Comparative analysis of glycoprotein and glycolipid composition of virulent and avirulent strain membranes ofMycoplasma hyopneumoniae

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.     

Developmental changes of myelin-related lipids in brain of miniature swine

The biochemical development of whole brains from male and female miniature swine aged 2 weeks to 1 years was studied. The data were similar for both sexes. The brain-body weight ratio declined rapidly for the first 10–12 weeks after birth, then decreased at a slower rate up to 1 year. Total brain lipid weight and lipid phosphorus changed rapidly during the first 8–10 weeks of life, but thereafter changed very little. The glycolipid content rapidly increased during the first 12–14 weeks of life and then increased at a slower rate. Total brain cholesterol increased continuously over the time period studied, although the rate of increase appeared to decline with age. Monogalactosyl diacylglycerol concentration remained constant up to about 8 weeks of age, but then decreased continuously up to 1 year. The alkali-labile fatty acid composition of pig brain remained relatively constant except for increases in 181 and 226(n – 3) and a decrease in 160. The increase in percentage of 181 was most rapid during the first 10 weeks of age. These data suggest that the growth spurt or active myelination phase of miniature pig brain development ends at 8–10 weeks post partum.     

Immunocytochemical studies on the LHRH system of the Japanese quail: influence by photoperiod and aspects of sexual differentiation

Summary Immunocytochemistry was used to determine if photoperiod and/or sex have any effect on the pattern of the luteinizing hormone-releasing hormone (LHRH) system in the brain of the Japanese quail. Immunopositive perikarya were found within three major areas of the brain: the rostral paraolfactory lobe, the preoptic, and the septal region. A quantitative analysis of LHRH cell numbers was performed on male and female quail after two photoperiodic treatments: sexually mature birds exposed to 24 weeks of 20 h light: 4 h darkness (20L4D), and birds with a regressed reproductive system (induced by transfer from a photoregime of 20L4D to 25 short days of 8L16D). Two-way analysis of variance showed that short-day males display significantly (p < 0.05) more immunopositive perikarya (607 + 134) than long-day males (291 + 114), short-day females (293 + 103) or long-day females (330 + 92). The density of LHRH-immunoreactive nerve fibres and the intensity of the immunostaining in the median eminence were always greater in long-day sexually mature quail (male and female) than in animals exposed to 25 days of 8L16D. These results demonstrate that the LHRH system of the quail is influenced by photoperiod and mirrors sexual differentiation.