Temperature experienced during vitellogenesis influences ovarian maturation and the timing of ovulation in common wolffish

Temperature treatment of common wolffish Anarhichas lupus during vitellogenesis affected the time of final maturation; ovulation in fish held at 8 and 12° C from mid-April to October was about four and five weeks delayed, compared with a 4° C group. Fish in the 8° C group had significantly larger eggs than those in the 4° C and the 12° C groups, and a significantly higher egg production than fish in the 12° C group. Temperature treatment did not affect either fertilization rate or relative fecundity, but absolute fecundity was significantly lower in the 12° C group than the other groups due to poor growth of the fish at high temperature. This did not affect the numbers of spawning individuals. There was a trend towards lower egg survival to the eyed stage in the 12° C group compared to the 4 and 8° C groups, although the effect was not statistically significant. The results indicate that both the timing of final maturation and investment in ovarian growth in common wolffish are affected by temperature experienced during vitellogenesis.     

Serum levels of testosterone, 11‐ketotestosterone and oestradiol‐17β in three species of sturgeon during gonadal development and final maturation induced by hormonal treatment

Changes in serum concentrations of two androgens, testosterone (T) and 11‐ketotestosterone (11KT), and oestradiol‐17β(E2) in male and female giant sturgeon Huso huso , Russian sturgeon Acipenser gueldenstaedtii and stellate sturgeon Acipenser stellatus were studied at different stages of gonadal maturity and after final maturation induced by hormonal treatment. Both male and female fish displayed a distinct increase in serum steroid concentrations during gonadal development. 11KT levels were significantly higher in males than females, with a positive correlation detected between 11KT and T concentrations. In maturing males and females, higher values of both 11KT and T were observed in stellate sturgeon compared to giant and Russian sturgeons. Vitellogenesis and high E2 levels were correlated in maturing sturgeon females.     

Rapid bioconcentration of steroids in the plasma of three-spined stickleback Gasterosteus aculeatus exposed to waterborne testosterone and 17β-oestradiol

The relationship over time between the concentrations of two steroids, singly and in combination, in a static exposure system and in the blood of three-spined stickleback Gasterosteus aculeatus , held within the exposure system was investigated. Groups of three-spined stickleback were exposed (nominally) to either 1000 ng l⁻¹ 17β-oestradiol (E2), testosterone (T) or E2 and T in combination at the same concentrations for 6 days. Both water and fish were sampled at intervals and steroid concentrations in both compartments were determined. The plasma steroid time profile revealed a rapid bioconcentration within the first 6 h of exposure. The plasma steroid levels attained at this time point (20–90 ng ml⁻¹) were up to 50-fold (E2) and 200-fold (T) greater than the actual levels of steroid measured in the exposure water, while levels in the blood of control fish did not exceed 4 ng ml⁻¹. The substantial elevation of plasma steroid levels relative to the concentrations of steroid to which the fish were exposed in the ambient water gives scope for delivery of the steroids to target endocrine tissues at levels far in excess of what might be predicted on the basis of passive branchial uptake alone. These results are discussed in relation to endocrine disruption, and in particular the occurrence of effects in fish exposed to levels of endocrine active substances that are seemingly physiologically irrelevant.     

Steroid hormone profiles and correlative gonadal histological changes during natural sex reversal of sobaity kept in tanks and sea-cages

The gonadosomatic index of sobaity Sparidentex hasta fits well with the natural spawning season of February-March. At 12 and 24 months all the population matured as males. However, during this time, between April-September intersex gonads were seen. From October of the third year of life, females were seen for the first time. These changes in the histology of the gonads were correlated with the hormonal profile. Testosterone showed no significant correlation with sex but 11-ketotestosterone correlated very well with the mature male gonads and thus can be used for sexing. Oestradiol-17β higher in sex reversed individuals (females) in the spawning season than in males. The sequence of events in the protandrous sex change of this fish during the first two spawning seasons is male → intersex → male. However, during the third spawning season (age 36–37 months) this sequence is male →intersex → male or female (10–17%).     

Seasonal correlative changes between sex steroids and lipid levels in the freshwater female catfish, Heteropneustes fossilis (Bloch)

Circannual variation in plasma levels of testosterone (T), oestradiol-17β(E₂) and 17α-hydroxy-progesterone (17α-OHPg) were measured in female, Heteropneustes fossilis . T and E2 levels increased during the preparatory phase, reached their peak in the early prespawning phase and fell during the late prespawning phase to reach their lowest levels post-spawning. 17a-OHPg was detected from the late preparatory to the late spawning phase showing its peak during the early spawning phase. The levels of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL), free cholesterol (CF)and esterified cholesterol (CE) were estimated in liver, plasma and ovaries. The preparatory phase showed hepatic lipogenic activity while during the prespawning phase TG lipolysis was increased by FFA. Ovarian CF was depleted by enhancing plasma E, levels during the prespawning phase. The gonadosomatic index reached its peak during spawning.     

Plasma cortisol and 17β-oestradiol levels in roach exposed to acute and chronic stress

Plasma cortisol levels were measured as an indicator of physiological stress in roach subjected to brief handling, or to a 14-day period of confinement, and in undisturbed control fish, during winter (water temperature 5° C) and summer (16° C), at which time plasma 17 β-oestradiol levels were also determined. Cortisol levels in undisturbed roach were low (mean 8·1 ng ml⁻¹ at 5° C; 1·4 ng ml⁻¹ at 16° C) and both handling and handling+confinement elevated blood cortisol levels significantly to 400 and 140 ng ml⁻¹, respectively (at 5° C) and 700 and 600 ng ml⁻¹, respectively (at 16) C). Blood cortisol levels had almost returned to baseline within 4 h following handling alone but in fish subjected to handling and prolonged confinement cortisol levels remained elevated for up to 168 h. Differences in baseline and poststress levels of cortisol, and in the rate of recovery from acute stress, were observed at the two different temperatures and the possible factors underlying these differences are discussed. Circulating levels of 17 β-oestradiol were reduced significantly within 24 h of exposure to either acute handling or chronic confinement indicating that the reproductive endocrine system in roach is sensitive to disruption by stressors.     

Dynamics of excretion of 17α,20β-dihydroxy-4-pregnen-3-one 20-sulphate, and of the glucuronides of testosterone and 17β-oestradiol, by urine of reproductively mature male and female rainbow trout (Oncorhynchus myklss)

Levels of sulphated 17α20β-dihydroxy-4-pregnen-3-one (17,20 β -P; the oocyte maturation inducing steroid) in blood plasmas of sexually mature male and female rainbow trout Oncorhynchus mykiss , were very low in comparison to those of the free steroid. However, relatively large amounts were found in urine of both sexes.
Catheters were inserted into the urinary bladders of unovulated and ovulated females and of ripe-running males, and the fish then placed in spawning channels. Three-hourly urine samples were collected between 09.00 and 18.00 hours and then a 15-h sample between 18.00 and 09.00 hours the next morning. Measurements were made of 17,20 β -P-sulphale, testosterone glucuronide (T-G) and 17 β -oestradiol glucuronide (E2-G). In females, the highest rates of excretion of E2-G, T-G and 17,20 β -P-sulphate were found in unovulated, ovulating and ovulated females, respectively. The rates of excretion of 17,20 β -P-sulphate, T-G and E2-G in ovulated females were unaffected by the presence of a male. id males, however, there was a sharp increase in the rate of excretion of 17,20 β -P-suiphate and T-G in fish which were paired with an ovutated (nesting) female. A similar increase was found in males injected with male trout pituitary extract.     

Changes in ovarian development and plasma levels of sex steroid hormones in the wild female Japanese sardine (Sardinops melanostictus) during the spawning period

In order to clarify the spawning pattern of Japaneses sardine ( Sardinops melanostictus ) during the spawning period, changes in ovarian histology, frequency distributions of oocyte diameter and plasma levels of oestradiol-17β (E₂) and 17 a ,20β-dihydroxy-4-pregnen-3-one (17 a ,20β-diOH-P) were examined in female fish captured in the region off Kyushu and Shikoku in Japan. With the development of the ovary, the gonadosomatic index (GSI) increased gradually and the size of oocytes became larger. When the GSI exceeded 13, the translucent hydrated eggs began to dominate and ovulation subsequently occurred. After ovulation, GSI decreased to less than 3. Post-ovulatory follicles were found only in the lower GSI ranges and atretic oocytes were always observed in the ovary. Plasma E₂ levels increased along with ovarian development but decreased after completion of yolk accumulation. On the other hand, 17 a ,20β-diOH-P showed the highest level just before and after ovulation. Ovarian histology and hormonal profiles suggest that the sardine spawns repeatedly during the spawning period. Based on the concentration of 17a,20β-diOH-P, the female Japanese sardine was estimated to ovulate before the middle of the night.     

Substitution of Thr for Ala-237 in TEM-17, TEM-12 and TEM-26: alterations in β-lactam resistance conferred on Escherichia coli

Non-naturally occurring mutants of TEM-17 (E104K), TEM-12 (R164S) and TEM-26 (E104K:R164S) extended-spectrum (ES) beta-lactamases bearing threonine at position 237 were constructed by site-specific mutagenesis and expressed under isogenic conditions in Escherichia coli. Quantification of beta-lactamase activities and immunoblotting indicated that Ala-237-->Thr did not significantly affect expression levels of these ES enzymes. Minimum inhibitory concentrations of beta-lactam antibiotics showed that the presence of threonine at position 237 exerted a dominant effect increasing the enzymes' preference for various early generation cephalosporins over penicillins. Activity against broad-spectrum oxyimino-beta-lactams was also changed. The effect of Ala-237-->Thr on the activity against ceftazidime, aztreonam, cefepime and cefpirome of all three ES TEM enzymes was detrimental. Introduction of Thr-237 improved activity against cefotaxime and ceftriaxone in TEM-12 and TEM-26, but not in TEM-17.     

Selectivity and Regulation in the Phospholipase A2-Mediated Attack on Cholinergic Synaptic Vesicles by β-Bungarotoxin

Abstract The total fatty acid composition of purified Torpedo californica electric organ synaptic vesicles was determined by GLC analysis of methyl esters. Limit amounts of fatty acids released by high concentrations of either β-bungarotoxin (β-BuTx) or Naja naja venom phospholipase A₂ (PLA₂) acting in deoxycholate are reported. The time and enzyme concentration dependence for β-BuTx- and PLA₂-induced release of fatty acids from intact synaptic vesicles indicate that PLA₂ is 100- to 1,000-fold more active. The Ca²⁺ dependence for β-BuTx-induced release of fatty acids also was determined. ATP inhibits β-BuTx- but not PLA₂-induced release of fatty acids from vesicles in a manner that can not be ascribed only to chelation of the required Ca²⁺. ATP, other nucleotides, and adenosine have complex effects on β-BuTx-induced release of fatty acids from egg yolk phosphatidylcholine dispersed in deoxycholate. The results suggest that β-BuTx-mediated hydrolysis of the cholinergic synaptic vesicle membrane is ～10- to 100-fold more effective at causing uncoupling of vesicles than is PLA₂ and that the enzymatic activity of β-BuTx is subject to regulation by nucleotide-like factors.     

Influence of plasma lipid changes in response to 17β-oestradiol stimulation on plasma growth hormone, somatostatin, and thyroid hormone levels in immature rainbow trout

Plasma total lipids were significantly higher in 17β-oestradiol(E₂)-treated immature rainbow trout Oncorhynchus mykiss at week 4 after implantation, due to increases in polar and neutral lipids. The lipid classes responding were phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, sterols and sterol esters, in a proportion that approximately reflected the increase in plasma vitellogenin (VtG) levels as measured by a non-competitive enzyme-linked immunosorbent assay (ELISA). Plasma non-esterified fatty acids and triacylglycerol were not affected by E₂ treatment. Plasma growth hormone GH levels were increased, and plasma somatostatin-14 (SRIF) levels decreased in E₂-treated fish, responses which could be secondary to elevated plasma lipid (VtG) content, although a direct E₂ action on somatotroph function is possible. Plasma T₄ concentrations were not affected by E₂ treatment, but plasma T₃ concentrations were significantly lower than in controls 1 week after implantation when plasma E₂ concentrations were the highest; this is in support of the hypothesis that E₂ has a suppressive action on T₃ production.