The caudal spinal cord of coho salmon (Oncorhynchus kisutch): Immunocytochemical evidence of a “caudal serotoninergic system”

Summary The caudal spinal cord of the coho salmon was investigated by means of immunocytochemistry using antisera against serotonin, urotensin I, urotensin II, somatostatin and a urea-extract of bovine Reissner's fiber (AFRU). Populations of serotonin-immunoreactive (IR) neurons were found rostral and dorsal to the urophysis in close spatial association with caudal secretory neurons. Thick, smooth serotonin-IR processes extended toward the external surface of the spinal cord where they displayed conspicuous terminal dilatations. Thin, beaded serotonin-IR fibers appeared to innervate populations of caudal secretory and somatostatin-IR cerebrospinal fluid-contacting neurons. Most caudal neurosecretory cells displayed both urotensin I and urotensin II immunoreactivities; only a minority reacted exclusively with either urotensin I or urotensin II antisera. Urotensin II-IR and somatostatin-IR cerebrospinal fluid (CSF)-contacting neurons were found as an integral component of the central canal wall in the caudal spinal cord and filum terminale; their dendritic processes appeared to contact Reissner's fiber, which displayed a weak AFRU-immunoreactivity while inside the central canal, but became strongly reactive in the interior of the terminal ventricle as it formed the massa caudalis. The distribution of serotoninergic processes points to a regulatory role in the function of caudal secretory and CSF-contacting neurons and to a putative serotonin release into the subarachnoid space and/or meningeal vasculature. It is also suggested that the CSF-contacting neurons of the central canal may participate in a feedback mechanism controlling the secretory activity of the subcommissural organ.Supported by Grant A/1095-1 from the International Foundation for Science, Sweden, to C.Y.; Grant I/63-476 from Volkswagen-Stiftung to E.R.; and Grant S-85-39 from the Dirección de Investigaciones, Universidad Austral de Chile     

Analysis of spatial and semporal organization in a salmonid brook in relation to physical factors and macrophytic vegetation

Four compartments of a salmonid brook were studied in consecutive sections either at sector scale or at facies scale: physical features, water quality, macrophytes and salmonids. The most important factor in the spatial and temporal organisation was the longitudinal zonation assessed by the four compartments. It was mainly shown by a gradient of the length of the morphodynamic sequence and of the facies width, of the pH and the conductivity and of macrophyte cover. It induced a colonisation by older trout in the downstream part of the brook where growth was better and shelter given by the bankside vegetation was more abundant. There were also greater densities of other age-classes upstream, with a correlation between salmon and rock shelter. Furthermore, the second factor corresponded to the flow characteristics and a granulometry gradient. The third factor corresponded chiefly to lighting, salmon numbers and densities. Salmonids showed a temporal stability from spring to autumn,and an opposition between growth and density. Six clusters of sectors defined functional entities. With regard to the 3—dimensitnal structure of the brook, the special pattern of each compartment shows its contribution to the functioning of the whole. Taking into account the scale of the study, the coexistence between trout and salmon did not show a competition between the two species, but rather a spatial partition, thanks to thehheterogenity inside each sector. We concluded on the necessity of studying sympatry at the facies scale to assess the role of habitat factors as regulators of carrying capacity.     

A phosphorus NMR study of the reaction products of cis-diamminedichloroplatinum (II) with a double-helical oligonucleotide and with DNA

The structural distortion of oligonucleotides upon cis-PtCl2(NH3)2[d(T-C-T-C-G-G-T-C-T-C)-N7(5), N7(6)] reveals shifting of 4 phosphorus resonances due to platination. 3 Resonances could be assigned by selective 31P-irradiation, showing P(6) (P between the two Gs) to be shifted 1.5 ppm to low field. In the concomitant double strands P(6) is shifted 0.9 ppm to lower field. A similar peak has been observed in platinated salmon sperm DNA (37 degrees C), indicating that Pt-binding to GpG-fragments in DNA is similar to that found for the decanucleotide, so the distortion of DNA might be comparable.     

鲑鱼生长激素cDNA的分子克隆和序列分析

从太平洋切奴克鲑鱼(Pacific Chinook Salmon,Oncorthychus tschawytscha)垂体poly(A)~+ RNA构建cDNA文库。按照鲑鱼生长激素(sGH)部分氨基酸序列合成两个寡聚脱氧核苷酸探针,它们分别与编码第1—7和第166—172氨基酸序列互补。用探针筛查cDNA文库,得到了完整的sGH cDNA克隆。cDNA序列已测定,包括编码210个氨基酸的编码序列。其中含有22个氨基酸的信号肽序列和188个氨基酸的成熟GH序列。该克隆还包括了5'端和3'端非翻译区,分别为72个和438个碱基对长。与Chum鲑鱼比较表明,核酸序列和氨基酸序列的同源性分别为97%和99%。     

Effects of fasting and nutritional restriction on the isotopic ratios of nitrogen and carbon: a meta‐analysis

Many organisms experience fasting in their life time, and this physiological process has the potential to alter stable isotope values of organisms, and confound interpretation of food web studies. However, previous studies on the effects of fasting and starvation on stable isotopes show disparate results, and have never been quantitatively synthesized. We performed a laboratory experiment and meta‐analysis to determine how stable isotopes of δ¹⁵N and δ¹³C change with fasting, and we tested whether moderators such as taxa and tissue explain residual variation. We collected literature data from a wide variety of taxa and tissues. We surveyed over 2000 papers, and of these, 26 met our selection criteria, resulting in 51 data points for δ¹⁵N, and 43 data points for δ¹³C. We determine that fasting causes an average increase in the isotopic value of organisms of 0.5‰ for δ¹⁵N and that the only significant moderator is tissue type. We find that the overall effect size for δ¹³C is not significant, but when the significant moderator of tissue is considered, significant increases in blood and whole organisms are seen with fasting. Our results show that across tissues and taxa, the nutritional status of an organism must be considered when interpreting stable isotope data, as fasting can cause large differences in stable isotope values that would be otherwise attributed to other factors.     

Frequency responses of age-structured populations: Pacific salmon as an example

Increasing evidence of the effects of changing climate on physical ocean conditions and long-term changes in fish populations adds to the need to understand the effects of stochastic forcing on marine populations. Cohort resonance is of particular interest because it involves selective sensitivity to specific time scales of environmental variability, including that of mean age of reproduction, and, more importantly, very low frequencies (i.e., trends). We present an age-structured model for two Pacific salmon species with environmental variability in survival rate and in individual growth rate, hence spawning age distribution. We use computed frequency response curves and analysis of the linearized dynamics to obtain two main results. First, the frequency response of the population is affected by the life history stage at which variability affects the population; varying growth rate tends to excite periodic resonance in age structure, while varying survival tends to excite low frequency fluctuation with more effect on total population size. Second, decreasing adult survival strengthens the cohort resonance effect at all frequencies, a finding that addresses the question of how fishing and climate change will interact.     

Anti-hypercalcemic effect of orally administered recombinant <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> expressing salmon calcitonin on hypercalcemic rats

Oral delivery of salmon calcitonin (sCT) to rats via a recombinant Saccharomyces cerevisiae was assessed. A synthetic sCT gene was cloned and expressed in S. cerevisiae yAGA2-sCT. Recombinant salmon calcitonin (rsCT) expression was detected by flow cytometry. The resorption activity of osteoclasts was inhibited by 3 × 10⁻⁶ M rsCT. Oral administration of 5 g lyophilized yAGA2-sCT/kg to hypercalcemic rats decreased serum calcium from 2.8 ± 0.02–2.7 ± 0.02 mM.     

An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D?

It has been suggested that the major source of vitamin D should come from dietary sources and not sun exposure. However, the major fortified dietary source of vitamin D is milk which often does not contain at least 80% of what is stated on the label. Fish has been touted as an excellent source of vitamin D especially oily fish including salmon and mackerel. Little is known about the effect of various cooking conditions on the vitamin D content in fish. We initiated a study and evaluated the vitamin D content in several species of fish and also evaluated the effect of baking and frying on the vitamin D content. Surprisingly, farmed salmon had approximately 25% of the vitamin D content as wild salmon had. The vitamin D content in fish varied widely even within species. These data suggest that the tables that list the vitamin D content are out-of-date and need to be re-evaluated.