Magnetic properties of γ-Fe2O3 nanoparticles in a porous SiO2 shell for drug delivery

A method is presented for synthesizing core-shell nanoparticles with a magnetic core and a porous shell suitable for drug delivery and other medical applications. The core contains multiple γ-Fe2O3 nanoparticles (∼15 nm) enclosed in a SiO2 (∼100-200 nm) matrix using either methyl (denoted TMOS-γ-Fe2O3) or ethyl (TEOS-γ-Fe2O3) template groups. Low-temperature Mössbauer spectroscopy showed that the magnetic nanoparticles have the maghemite structure, γ-Fe2O3, with all the vacancies in the octahedral sites. Saturation magnetization measurements revealed that the density of γ-Fe2O3 was greater in the TMOS-γ-Fe2O3 nanoparticles than TEOS-γ-Fe2O3 nanoparticles, presumably because of the smaller methyl group. Magnetization measurements showed that the blocking temperature is around room temperature for the TMOS-γ-Fe2O3 and around 250 K for the TEOS-γ-Fe2O3. Three dimensional topography analysis shows clearly that the magnetic nanoparticles are not only at the surface but have penetrated deep in the silica to form the core-shell structure.

CHARGE TRANSFER. Efficient hot-electron transfer by a plasmon-induced interfacial charge-transfer transition

Plasmon-induced hot-electron transfer from metal nanostructures is a potential new paradigm for solar energy conversion; however, the reported efficiencies of devices based on this concept are often low because of the loss of hot electrons via ultrafast electron-electron scattering. We propose a pathway, called the plasmon-induced interfacial charge-transfer transition (PICTT), that enables the decay of a plasmon by directly exciting an electron from the metal to a strongly coupled acceptor. We demonstrated this concept in cadmium selenide nanorods with gold tips, in which the gold plasmon was strongly damped by cadmium selenide through interfacial electron transfer. The quantum efficiency of the PICTT process was high (>24%), independent of excitation photon energy over a ~1-electron volt range, and dependent on the excitation polarization.

Biomonitoring of traffic-related nitrogen pollution using Letharia vulpina (L.) Hue in the Sierra Nevada, California

To assess the impact of vehicular emissions on a mixed conifer forest, we measured the contents of the trace elements, N, C, and their respective natural isotopes (δ(15)N and δ(13)C), in the epiphytic lichen, L. vulpina. The samples were collected along transects perpendicular to Interstate 80 (I-80) and along a more remote, secondary forest road (R07). Distance to the road verge, trunk cover, and stand basal area were also recorded. Percent N ranged from 1.10% to 2.00% near I-80 and from 0.78% to 1.13% along R07. Concentrations of N, (15)N, Na, As, Pb, and Zn were enhanced in lichen samples near I-80 and were negatively correlated with distance from the road. Trunk cover values differed between roads (p<0.001) and were negatively correlated with %N (r(2)=0.74; p<0.001). The results indicate that vehicular N emissions are significant enough to alter the surrounding ecosystem, modifying the presence of a sensitive component such as L. vulpina, and suggest that a clean-site threshold of 1.0%N may be too high as an indicator of critical N load exceedance. The study also underscored the potential role of wolf lichen in a large-scale assessment of N deposition and source identification.

Adolescent life experiences as predictors of occupational attainment

Adolescent life experiences, measured with Owen's Biographical Questionnaire (BQ), were used to predict occupational attainment 16 years to 21 years later in a sample of 1,523 college graduates. Study participants completed the BQ in either 1968 or 1970-1973 as college freshmen and subsequently reported their occupational status in 1989. Jobs were rationally clustered into 18 different categories. Separate gender analyses were conducted in which 13 BQ factors were used as predictors of occupational attainment. Effect sizes were substantially larger than those obtained in an earlier study by A. G. Neiner and W. A. Owens (1985). The usefulness of life experience data for understanding occupational choices as well as implications for college counseling are discussed.

Influence of dietary lipid and carbohydrate levels and chronic 3,5,3'-triiodo-L-thyronine treatment on thyroid function in immature rainbow trout, Oncorhynchus mykiss

The influence of varying dietary levels of nonprotein energy sources (lipid, L; carbohydrate, C) and 3,5,3'-triiodo-L-thyronine (T3) on thyroid function in immature rainbow trout was studied. Three diets of equivalent available energy content and identical nutrient composition, except for dissimilar concentrations of L and C (diet 1, L = 7%, C = 28.3%; diet 2, L = 13%, C = 14.9%; diet 3, L = 19%, C = 1.5%), were each supplemented with 0, 4, 8, or 12 ppm T3 and fed to satiation to trout at 6.5 +/- 0.5 degrees on a 12-hr photoperiod for 12 weeks. Dietary L and C concentrations did not influence plasma total L-thyroxine (T4) or T3 levels, indices of free T4 or free T3 levels, hepatic T4 5'-monodeiodinase (5'D) activity, capacity or affinity of hepatic nuclear T3 receptors, or thyroid follicle epithelial cell height. T3 treatment elevated total and free T3 levels and decreased 5'D activity (Vmax) in approximate proportion to T3 dose, and without effect on plasma total or free T4 levels or T3 receptor properties. However, thyroid follicle epithelial cell height was depressed at 8 or 12 ppm dietary T3. In trout reverted for 20 days to a T3-free diet from a T3 (12 ppm) diet, plasma total T3 levels fell to 30% of those of control trout (0 ppm T3 throughout). It was concluded that, under our experimental conditions, (i) trout thyroid function was refractory to dietary concentrations of L and C, (ii) the primary response to T3 supplementation was suppressed hepatic 5'D level and T3 production, which was sustained for at least 20 days after T3 treatment ceased, and (iii) despite causing a probable indirect decrease in thyroidal secretion, T3 did not modify the set point of the hypothalamo-hypophyseal-thyroid axis based on plasma total or free T4 levels.

Influence of dietary calcium, phosphorus, zinc and sodium phytate level on cataract incidence, growth and histopathology in juvenile chinook salmon (Oncorhynchus tshawytscha)

To determine the influence of wide variations in dietary levels of calcium, zinc and phytic acid (as sodium phytate) on growth and cataract incidence, juvenile chinook salmon held at 10-11 degrees C were fed daily to satiation for 105 d one of nine purified diets containing one of three levels (grams/kilogram) of calcium (averaged 4.8, 17.7, 50.2), zinc (averaged 0.05, 0.15, 0.39) and phytic acid (1.62, 6.46, 25.8). Diets were formulated to have a calcium-phosphorus ratio of close to unity when considering phosphorus sources other than sodium phytate. High dietary phytic acid concentration (25.8 g/kg) depressed chinook salmon growth, food and protein conversion [protein efficiency ratio (PER)] and thyroid function, increased mortality, promoted cataract formation (zinc at 0.05 g/kg) and induced anomalies in pyloric cecal structure. Calcium at 51 g/kg (or phosphorus) exacerbated the effects of high dietary phytate and low dietary zinc on cataract incidence. Moreover, high dietary levels of calcium (48-51 g/kg) coupled with phosphorus significantly impaired the growth and appetite of low phytic acid (1.62 g/kg) groups and led to nephrocalcinosis in low and high phytic acid groups. Plasma zinc levels were directly related to dietary zinc concentration and inversely related to dietary phytic acid level. Calcium (51 g/kg) and/or phosphorus reduced zinc bioavailability when the diet concurrently contained 0.05 g zinc and 25.8 g of phytic acid per kilogram. It is concluded that zinc is essential for normal eye development in juvenile chinook salmon. Further, zinc deficiency could not be induced in chinook salmon fed diets with high ratios of calcium (or phosphorus) to zinc alone. This required the simultaneous presence of a strong mineral (zinc)-binding agent.

The potential for using the anabolic hormones 17 alpha-methyltestosterone and (or) 3,5,3'-triiodo-L-thyronine in the fresh water rearing of coho salmon (Oncorhynchus kisutch) and the effects on subsequent seawater performance

Juvenile coho salmon (Oncorhynchus kisutch) held in 11 °C fresh water (FW) were fed Oregon moist pellets supplemented with 3,5,3′-triiodo-L-thyronine at 4 ppm (T34) or 20 ppm(T320) and (or) 17α-methyltestosterone at 0.2 ppm (MT0.2) or 1 ppm (MT1) until early or normal seawater (SW) transfer.During FW residency all hormonal treatments improved growth, appetite, and food utilization. In February, fish fed T320 singly or with MT had increased degranulation of somatotrop cytoplasm. Thyroid epithelial cell height of fish fed T34 or T320 was either suppressed or enhanced. MT1 singly or combined with T3 induced androgenic side effects in males. Proximate body composition was affected only by MT. T320 induced morphological anomalies and treatment was discontinued. In May, thyroid activity and number of putative gonadotrops of fish fed MT1 were increased. Androgenic effects of all groups given MT1 were greater in May than in February.After SW transfer in February growth, appetite, and food utilization were depressed but fish fed T34 performed better than controls. Performance of all groups improved after May but, in general, mortality increased slightly. After transfer in May, T3-fed fish had increased growth in length.It is concluded that MT and T3 effectively enhance growth in FW but only T3 facilitates SW transfer.

Influence of orally administered L-thyroxine or 3,5,3′-triiodo-L-thyronine on growth, food consumption, and food conversion of underyearling coho salmon (Oncorhynchus kisutch)

Between August and November, groups of underyearling coho salmon, held at 10 °C and on a natural photoperiod, were fed twice daily to satiation with Oregon moist pellets supplemented with 0, 20, 100. or 500 ppm of L-thyroxine (T4) or 3,5,3′-triiodo-L-thyronine (T3).The T3 significantly increased weight (20 and 100 ppm) and length (all doses), depressed condition factor (100 and 500 ppm), stimulated food consumption (20 ppm), improved food conversion (all doses), decreased thyroid follicle epithelial height (500 ppm), and influenced pituitary basophil and somatotrop number, size, and granulation.The T4 influenced neither growth nor food conversion, but did increase food consumption (20 ppm) and condition factor (500 ppm). and decreased thyroid follicle epithelial height (500 ppm).No breakdown of either added T4 or T3 was observed during prolonged food storage.It is concluded that T3 unlike T4, can be administered in the diet of coho held at 10 °C to enhance growth and improve food conversion.

Distribution and Disappearance of Radioactivity in Blood and Tissues of Coho Salmon (Oncorhynchus kisutch) After Oral Administration of 3H-Testosterone

Yearling coho salmon (Oncorhynchus kisutch) were fed 3 times per day a diet containing 5 mg/kg of 3H-testosterone until the concentration of radioisotope in all tissues was constant. Radioactivity was monitored in blood and 16 tissues for 10 d after the hormone was withdrawn from the diet. Excretion was via the hepatobiliary pathway. Sixteen hours after the last feeding of 3H-testosterone, 93.1% of total radioactivity in soft tissues resided in the alimentary tract and gall bladder. Blood, skin, white muscle, and liver each contained about one fifth of remaining radioactivity. Concentrations of labeled substances in blood and testis were similar to or lower than normal androgen concentrations reported in salmonids. Ten days after steroid withdrawal concentrations were 1 ng/g or lower in all tissues. Key words: salmonid, diet, anabolic effect, androgen, testosterone, half-life, radioactivity, residue, tissue

A preliminary study of insulin participation in the growth regulation of coho salmon (Oncorhynchus kisutch)

As part of an ongoing survey to identify hormones capable of stimulating growth in Pacific salmon, groups of underyearling coho salmon were injected with bovine (Ultralente) insulin (0.32, 1.0, 3.2, or 10 IU/kg body weight) into the peritoneal cavity either once or twice weekly for 70 days.All doses of insulin, when injected twice weekly, increased the values for specific growth rates and decreased those for food–gain ratios relative to solvent-injected controls, but the differences were not statistically significant. All doses of insulin caused a marked increase in the granulation of the pancreatic B cells. Plasma glucose concentrations in starved coho injected with 10 IU insulin/kg body weight were significantly lower than in solvent-injected controls 4 h after injection.It is concluded that proper evaluation of the effectiveness of insulin as a growth promoter for salmon requires further studies preferably using insulin preparations specific to teleosts.

Influence of combinations of bovine growth hormone, 17 alpha-methyltestosterone, and L-thyroxine on growth of yearling coho salmon (Oncorhynchus kisutch)

Groups of yearling coho salmon held at 10 °C on a natural photoperiod, and fed excess ration daily, were administered either bovine growth hormone (bGH; 0.0092 IU/g body weight), L-thyroxine (T4; 1 μg/g), 17α-methyltestosterone (MT; 1 mg/kg diet), combinations of these hormones, or no hormone for 59 days. Fish received bGH and (or) T4 intramuscularly once weekly.Each individual hormone and hormone combination significantly enhanced growth. The sequence noted for growth rate of the groups was as follows: (bGH + MT + T4) > (bGH + MT) > (bGH + T4) > bGH > (T4 + MT) > MT > T4 > control groups. Three hormonal interactions were additive (T4 + MT; bGH + MT; bGH + MT + T4). The growth rate of fish treated with bGH + MT + T4 was over three times that of the controls.T4 or MT + T4 administration significantly increased condition factors, while MT, bGH, bGH + T4, bGH + MT, and bGH + MT + T4 decreased them.Significant elevations in percentages of muscle water (bGH) and lipid (T4; T4 + MT; bGH + MT) were found. Thyroid activity (follicle epithelial height) was significantly increased in MT and MT + bGH fish, but depressed in T4 fish. Hormone administration altered the histological structure of the endocrine pancreas (bGH and MT groups), ovary (bGH; MT groups), testis (MT groups), and interrenal tissue (bGH; MT).

Influence of Bovine Growth Hormone and L-Thyroxine on Growth, Muscle Composition, and Histological Structure of the Gonads, Thyroid, Pancreas, and Pituitary of Coho Salmon (Oncorhynchus kisutch)

Groups of underyearling coho salmon (Oncorhynchus kisutch) were acclimated to 10 C well water and a photoperiod of 12 h L:12 h D. Excess ration (Oregon Moist Pellet) was presented daily. Doses of bovine growth hormone (5, 10, 20, 30, or 90 μg bGH/g body wt) and L-thyroxine (0.5, 5, or 30 μg T4/g) were administered over a period of 84 days (phase I) either by injection (via dorsal musculature or peritoneal cavity) or by hormone cholesterol implants into the muscle. Administration frequency of bGH and T4 was such (range 2 times/wk-1 time/3 wk) that fish theoretically received either 10 or 30 μg bGH/g per wk or 1 or 10 μg T4/g per wk. Control fish received either alkaline saline (pH 9.5) or a cholesterol pellet. After cessation of treatment the fish were observed for an additional 84 days (phase II). During phase I, growth rates (weight) for bGH fish (2.0–2.4% per day) and for T4 fish (0.97–1.1% per day) were significantly higher than those of control fish (0.42–0.59% per day). Among bGH fish, dorsal musculature injection (2 times/wk) was significantly more effective than intraperitoneal injection (1 time/2 wk).Increases in weight above control for bGH fish at 84 days ranged from 220 to 369%. Those for T4 fish extended from 47 to 78%. In phase II, control fish growth rates were higher (0.61–0.67% per day) than those for bGH fish (0.47–0.57% per day) and T4 fish (0.32–0.44% per day). Administration of bGH and T4 (high dose) caused a progressive decline in condition factor of fish from the control range. This trend was stopped and reversed in phase II.At 84 days, generally no significant differences were detected among groups for percentages of muscle water. However, some groups had significantly higher (bGH) and others lower (T4) percentages of muscle protein relative to those of control fish. Also, significant increases (T4) and decreases (bGH) in muscle lipid percentages were found. Hormone treatment altered the histological structure of the ovary, thyroid, exocrine (T4) and endocrine (bGH) pancreas, and somatotrop cells (T4) of the pituitary. A poor growth response was noted for two groups of coho administered bGH after acclimation to sea water.

Effects of Thiourea Treatment on Sexually Maturing and Gonadectomized Male Sockeye Salmon (Oncorhynchus nerka)

Adult male sockeye salmon in the final stage of sexual maturation were treated with thiourea for periods of 7–14 wk. The treatment produced strong histological thyroid stimulation but no visible effect on spermatogenesis or development of secondary sexual characteristics. The drug did not affect the interrenal hypertrophy that commonly occurs in these salmon, but slightly inhibited the increase in thickness of the skin. Thiourea induced changes in the pars distalis of the pituitary gland, involving several cell-types, including retardation of gonadotrop development.In gonadectomized fish, thiourea affected neither the skin, nor the interrenal tissue. It caused a marked increase in the height of the thyroid epithelium, correlated with hypertrophy, degranulation, and some vacuolization of PAS-positive cells in the dorso-caudal area of the proximal pars distalis of the pituitary gland. Therefore, these last cells are considered thyrotrops.

Effect of ACTH and Salmon Gonadotropin on Interrenal and Thyroid Activity of Gonadectomized Adult Sockeye Salmon (Oncorhynchus nerka)

Injection of a chinook salmon (Oncorhynchus tshawytscha) gonadotropin preparation into gonadectomized sockeye salmon (Oncorhynchus nerka) did not result in any increase in the plasma concentration of cortisol or cortisone, nor did it stimulate the activity of the interrenal tissue. On the other hand, injection of mammalian ACTH (Acthar) did result in an increase in the plasma concentration of cortisol and cortisone, and stimulated the interrenal tissue. The salmon gonadotropin preparation, however, elicited an increase in thyroid activity. The results suggest that in the salmon, ovulation is not caused by gonadotropin induced interrenal corticosteroidogenesis.

The Use of 17 α-methyltestosterone for Promoting Weight Increases in Juvenile Pacific Salmon

The effect of 17 α-methyltestosterone feeding on the weight of juvenile coho salmon (Oncorhynchus kisutch) and on the weight, length, and condition factor of juvenile chinook salmon (O. tshawytscha) was determined. Significant increases in weight and length but not in condition factor were noted at all levels of steroid tested. Coho fed rations containing 10 mg/kg of the steroid for 42 days showed a 29% net weight gain and chinooks fed 1 mg/kg of the hormone for 84 days exhibited a 17% net weight gain over the respective control groups.A marked thickening of the skin was noted in the coho retained on diets containing 10 and 50 mg/kg of the steroid. This alteration was most evident in those fish fed the highest concentrations of hormone for the longest period.In the coho, diets containing 10 or 50 mg/kg of the hormone evoked marked degenerative changes in the testes. Less drastic alterations were noted in the testes of the chinooks retained on the 1 mg/kg test ration for 84 days. No apparent structural changes were noted in the ovary of any of the test fish.

Histological Effects of 11-Ketotestosterone, 17α-Methyltestosterone, Estradiol, Estradiol Cypionate, and Cortisol on the Interrenal Tissue, Thyroid Gland, and Pituitary Gland of Gonadectomized Sockeye Salmon (Oncorhynchus nerka)

Effects of two androgens, two estrogens, and cortisol in gonadectomized sockeye salmon (Oncorhynchus nerka) were investigated. Males were injected with 11-ketotestosterone, 17α-methyltestosterone, or cortisol for 4 or 7 weeks. Females were injected with estradiol, estradiol cypionate, or cortisol for 8 weeks.Both the androgens and the estrogens caused interrenal hypertrophy. The effect of 17α-methyltestosterone was stronger than that of 11-ketotestosterone, and of the two estrogens used, estradiol cypionate exerted the most marked effect. Cortisol brought about a slight atrophy of the interrenal tissue.A pronounced histological activation of the small thyroid follicles was induced by the two androgens. The estrogens exerted no visible effect on the thyroid gland, and cortisol treatment caused a slight reduction in the height of the follicular epithelium.In the gonadectomized control fish of both sexes, gonadotrophs were small and practically all devoid of granules. All four sex steroids induced the appearance of many granulated PAS-positive gonadotrophs, particularly in the anterior part of the proximal pars distalis. This effect is considered on activation of the gonadotrophs. Cortisol administration induced pronounced degranulation and atrophy of the corticotrophs and this effect was strongest in the males. Neither the androgens nor the estrogens visibly affected the corticotrophs.

Effects of Androgens, Estrogens, and Cortisol on the Skin, Stomach, Liver, Pancreas, and Kidney in Gonadectomized Adult Sockeye Salmon (Oncorhynchus nerka)

A study was made of the histological changes occurring in the skin, stomach, liver, pancreas and kidney of adult gonadectomized male and female sockeye salmon in response to hormone treatments. The males received 11-ketotestosterone, 17α-methyltestosterone or cortisol for 4 or 7 weeks, and the females received estradiol, estradiol cypionate, or cortisol for 8 weeks.In the males, androgen injection evoked a highly significant increase in the thickness of the epidermis, a marked atrophy of the stomach, and a degeneration in the liver and kidney. In the pancreas, the exocrine portion showed characteristics of cytolysis in the acini, whereas the islets of Langerhans were hypertrophied. These changes were generally more pronounced after 7 weeks than after 4 but, in the skin, no further increase in the thickening of the epidermis was noted after the 4th week of treatment. No differences between responses of these tissues to 11-ketotestosterone and 17α-methyltestosterosne were detected.Estrogen administration in the females evoked similar, albeit weaker, responses in the skin, stomach, pancreas, and kidney than those recorded in the androgen-treated males. The liver of the females exhibited the characteristics of a hyperactive organ, which probably reflects estrogen-induced vitellogenesis.The effects of cortisol were similar in both sexes: little, if any, change was noted in the skin; atrophy or degeneration was observed in the stomach, liver, kidney, and in the exocrine portion of the pancreas, and the islets of Langerhans were hypertrophied. The cortisol-induced alterations were not, however, as pronounced as those noted in either the androgen- or estrogen-treated fish.These changes are discussed in relation to the changes observed in normal sexually maturing and reproducing Pacific salmon.

Hypertrophy of the Interrenal Tissue in Sexually Maturing Sockeye Salmon (Oncorhynchus nerka) and the Effect of Gonadectomy

Sockeye salmon (Oncorhynchus nerka) develop marked hypertrophy of the interrenal tissue during the period of sexual maturation and spawning. No differences were found between fish held in captivity and those that matured in their natural habitat. Feeding appeared to have an inhibitory effect, but did not prevent the hypertrophy. Gonadectomy of sexually mature fish resulted in a rapid involution of the hyperplastic interrenal tissue. On the other hand, gonadectomy, when performed in an early stage of sexual maturity, prevented the development of interrenal hypertrophy. The interrenal hyperplasia was not accompanied by apparent changes in the ACTH cells of the pituitary gland. Gonadectomy, however, led to increased affinity of these cells for lead-hematoxylin, but this effect did not take place until after interrenal involution had commenced. The results are discussed and it is concluded that the hypertrophy of the interrenal at this time is caused by gonadal hormones, which may act directly on the adrenal homologue without mediation by the pituitary gland.

Cytological Changes in the Pituitary Gland of the Adult Sockeye Salmon (Oncorhynchus nerka) after Gonadectomy

Effects of gonadectomy on the cytological structure of the pituitary gland of sockeye salmon were investigated. Castration of fully grown, but sexually immature, fish appeared to prevent differentiation of any periodic acid–Schiff (PAS) positive cells. On the other hand, castration of mature sockeye induced degranulation of this cell type. These cells later disintegrated. Although the acidophil cells of the proximal pars distalis in the immature castrates showed an apparent increase in number, those in the gonadectomized ripe fish exhibited marked hyperplasia and hypertrophy. In view of the "rejuvenation," including the considerable increase in body weight that occurs after castration of sexually ripe sockeye, it is thought that the changes in the acidophils noted in this experiment may reflect an increased production of growth hormone. Where the gonadectomy was incomplete it was noted that very small remnants of gonad were able to induce, or maintain, all the external secondary characteristics of full sexual maturity. The pituitary of these fish exhibited cytological features intermediate between those of the controls and the complete castrates.

Effect of Metopirone on Pituitary–Interrenal Function in Two Teleosts, Sockeye Salmon (Oncorhynchus nerka) and Rainbow Trout (Salmo gairdneri)

Metopirone (SU 4885), an inhibitor of 11β-hydroxylation of adrenocorticosteroids, was administered intramuscularly to adult castrated sockeye salmon (Oncorhynchus nerka) and intact rainbow trout (Salmo gairdneri). Marked hypertrophy of interrenal cells pointed to an increase in the activity of the interrenal tissue of both species. Increased cortisol concentrations in trout at low dosage levels of metopirone suggested that the drug was stressful. However, decreased concentrations at higher dosage levels in trout, and decreased cortisol concentrations in all salmon indicated that the drug was also exerting a marked inhibitory effect on 11β-hydroxylation. In salmon, a repository ACTH preparation (acthar) brought about interrenal hypertrophy similar to that produced by metopirone. Metopirone also induced degranulation and hyperplasia of the cells of the palisade-like layer in the rostral region of the pars distalis in both species of fish. These cells were the only cell type of the pars distalis that were stained with lead-haematoxylin. The evidence indicates that they are the corticotrops.

The Pituitary Gland of the Sockeye (Oncorhynchus nerka) During Sexual Maturation and Spawning

This communication presents the results of a study of the pituitaries of 150 sockeye salmon in various stages of sexual maturation from the time they entered freshwater till after completion of spawning. In the homologue of the adenohypophysis, nine different cell types were distinguished. On the basis of changes in tinctorial and histochemical properties and relative proportions of each of these cells, it was concluded that the sockeye pituitary contains six different hormone-producing cell types. One of these probably possesses a gonadotrophic function. Degenerative phenomena in the pituitary were found in the sexually ripe and the spent salmon, but only to a limited extent. The implications of the changes in the occurrence of the six different cell types and the degenerative alterations are discussed in relation to gonad development and the death after spawning.

The Sodium, Potassium, and Water Content of the Flesh of Sockeye Salmon (Oncorhynchus nerka) in Relation to Sexual Development and Starvation

The influence of feeding on the changes that occur in the skeletal muscle content of sodium, potassium, and water in sockeye salmon (Oncorhynchus nerka) during sexual development and spawning has been investigated. Feeding has little, if any, effect on the changes. Thus it appears that the period of starvation these fish undergo during their spawning migration under natural conditions is not the major cause of the degeneration of their skeletal muscle, but rather that these changes are associated in some manner with the development of the gonads, presumably through the mediation of hormones.

Effects of Feeding on the Thyroid, Kidney, and Pancreas in Sexually Ripening Adult Sockeye Salmon (Oncorhyncus nerka)

In unfed adult sockeye salmon, Oncorhynchus nerka, histological examination showed extensive degenerative changes in the thyroid, pancreas, and kidney during gonad development. The more pronounced changes were generally noted in starved fish spawned in the wild. Feeding either prevented (thyroid) or distinctly reduced (pancreas, kidney) these changes in the sexually ripe fish. In fed spent sockeye the thyroid showed little change, the kidney exhibited further deterioration although not as marked as in the corresponding unfed fish, but the pancreas showed marked degenerative changes comparable with those exhibited in the unfed.

Post-Spawning Death of Pacific Salmon: Sockeye Salmon (Oncorhynchus nerka) Maturing and Spawning in Captivity

It has been shown that sockeye salmon, Oncorhynchus nerka, will start to eat soon after capture during their freshwater spawning migration. Some will continue to eat up to, during, and after spawning, while others stop eating shortly before spawning. The effect of feeding has been investigated histologically in a number of tissues by comparison of feeding fish, unfed controls, and fish spawned in the wild. Atrophy, and often degeneration of the liver, stomach, and intestine in post-spawned unfed controls and fish spawned in the wild was equally marked, but was absent or much less pronounced in fed fish.

OLFACTORY PERCEPTION IN JUVENILE SALMON: II. CONDITIONED RESPONSE OF JUVENILE SOCKEYE SALMON (ONCORHYNCHUS NERKA) TO LAKE WATERS

Sockeye salmon smolts were conditioned to distinguish between waters from two natural sockeye nursery systems, Great Central Lake (from which the smolts were obtained) and Cultus Lake. The attractant from each water was volatile, but that from Great Central Lake was the more readily volatilized of the two. Volatile material from Great Central Lake water was collected and shown to evoke a response in the group of fish conditioned to whole Great Central Lake water.

Olfactory Perception in Migrating Salmon: III. Stimulants for Adult Sockeye Salmon (Oncorhynchus nerka) in Home Stream Waters

Adult sockeye salmon (Oncorhynchus nerka) captured during their spawning migration to Great Central Lake, British Columbia, show a consistent response in the laboratory to water taken from the outlet of the lake. The specificity of this response has been confirmed and the responses to water from streams feeding Great Central Lake have been determined. A portion at least of the stimulatory material is volatile and can be retained in a cold trap. Concentration of the active factor has been achieved by a freezing-out technique.

2-Phenoxyethanol as a General Anaesthetic for Sockeye Salmon

The dose–response relationship of 2-phenoxyethanol, as a general anaesthetic, in adult sockeye salmon (Oncorhynchus nerka) has been investigated. At 11 °C the effective dose (ED50) and lethal dose (LD50) were approximately 43 and 130 ml/100 Imperial gal, respectively. The therapeutic ratio [Formula: see text] was more than 3, indicating a good margin of safety. At a lowered aquarium temperature of 4 °C the anaesthetic effects of 2-phenoxyethanol were potentiated. ED50 and LD50 at this temperature were approximately 25 and 130 ml/100 gal of water, respectively. The therapeutic ratio was more than 5, indicating that the margin of safety was increased by the decrease in temperature.

Resumption of Feeding by and Survival of Adult Sockeye Salmon (Oncorhynchus nerka) Following Advanced Gonad Development

Adult, migrating, fasting sockeye salmon (Oncorhynchus nerka) were held in captivity in fresh water without spawning well beyond the time when they would normally have done so and died. A few of the fish were then gonadectomized and force feeding was begun. A few unoperated fish were fed similarly while the remainder served as unoperated, unfed controls. The gonads of the operated fish were well developed. After a period of feeding of about four months some fish in each group had survived. The fed fish had regained their green color and much of their weight and vigor, while the surviving unfed fish were extremely emaciated and listless. At this time voluntary feeding by the force-fed fish was observed for the first time, and it was then found that the five surviving unfed controls would also take food voluntarily. While two of these fish died without apparent improvement in their condition, the other three gradually regained green color, weight and vigor.

Olfactory Perception in Juvenile Salmon.: I. Observations on Response of Juvenile Sockeye to Extracts of Foods

The introduction of aqueous extracts of natural foods into an aquarium holding juvenile sockeye evoked exploratory and feeding responses in fish that had previously eaten the foods, but failed to do so in fish that had not. Responses were characterized by breaking up of the school, increased swimming speeds, and the swimming of the fish into lighted areas. The fish detected concentrations of the active substance(s) in the order of one part in 80,000,000, based on the wet weight of the whole food.

OLFACTORY PERCEPTION IN MIGRATING SALMON: II. STUDIES ON A LABORATORY BIO-ASSAY FOR HOMESTREAM WATER AND MAMMALIAN REPELLENT

A laboratory bio-assay, based on the response of adult migrating sockeye salmon (Oncorhynchus nerka) to homestream water, is described. A characteristic response to the repellent in mammalian skin is discussed. The homestream substance(s) was tentatively identified as volatile, dialyzable, neutral, and heat-labile.The transportation and holding of sockeye in captivity was investigated.

The Liquefaction of British Columbia Herring by Ensilage, Proteolytic Enzymes and Acid Hydrolysis

Nearly all the herring landed on the British Columbia coast during the past 10 years has been converted by the wet reduction process to animal feed, the bulk of which was in the dry form. While the final products of the wet reduction process have proven to be of a high nutritive value, in the dry form they have the disadvantage in the amount of handling required during transit. A liquid product would not only reduce handling costs but also it would act as a binder in otherwise dry feed rations.Three methods have been tested to liquefy the whole herring: ensilage, high pressure steam liquefaction and proteolytic enzyme solubilization. In the ensilage process the liquefaction of the whole fish in an acid medium was achieved in 72 hours at 37 °C. The liquefaction of the fish was shown to be due to proteolysis by the natural occurring enzymes present both in the viscera and in the flesh of the fish and was not caused by the action of bacteria. While up to 70% of the whole fish was solubilized by autoclaving the fish in an acid medium, the resulting free oil was high in free fatty acid content and the liquid concentrate dark in colour. Of the commercial proteolytic enzymes tested, pepsin achieved the highest maximum solubilization, followed by bromelin and Rhozyme B-6. An oil–protein emulsion stable at 100 °C and to salting, however, was formed in the digest of each enzyme tested.Liquid fish products were prepared under pilot-plant conditions for future nutritional assay.

Seasonal Variation in the Collagen Content of Pacific Herring Tissues

The total amount of collagen and its relative solubility was determined in 3-year-old herring of the same population caught at two periods, June and January, representing two extremes of the sexual cycle. Sexually mature herring, caught in January, contained 40% more collagen than sexually immature fish caught in June. When fractionated into neutral salt-soluble, acid-soluble and insoluble collagen, the proportions of the three fractions remained much the same at both seasons of the year. When various tissue fractions of the fish were examined at the two seasons it was found that not only did the concentration of collagen change in the tissues with maturation but the contribution which some of the tissues made to the total body weight also changed. The skin + scales fraction contributed most to the increase in collagen in February herring. This was due partly to a higher concentration of collagen in these tissues at this season and partly to the higher proportion of skin + scales at this time of year. The significance of these findings in relation to the biochemistry of sexual maturation is considered.