Isolation and Structure Elucidation of New Cytotoxic Macrolides Halosmysins B and C from the Fungus Halosphaeriaceae sp. Associated with a Marine Alga

Two new cytotoxic metabolites, halosmysins B and C, have been isolated from the fungus Halosphaeriaceae sp. OUPS-135D-4 separated from the marine alga Sargassum thunbergii. These chemical structures have been elucidated by 1D and 2D NMR, and HRFABMS spectral analyses. The new compounds had the same 14-membered macrodiolide skeleton as halosmysin A, which was isolated from this fungal strain previously. As the unique structural feature, a diketopiperazine derivative and a sugar are conjugated to the 14-membered ring of halosmysins B and C, respectively. The absolute stereostructures of them were elucidated by the chemical derivatization such as a hydrolysis, the comparison with the known compounds (6R,11R,12R,14R)-colletodiol and halosmysin A, and a HPLC analysis of sugar. In addition, their cytotoxicities were assessed using murine P388 leukemia, human HL-60 leukemia, and murine L1210 leukemia cell lines. Halosmysin B was shown to be potent against all of them, with IC₅₀ values ranging from 8.2 ± 1.8 to 20.5 ± 3.6 μM, though these values were slightly higher than those of halosmysin A.     

Changes in plasma prolactin and growth hormone concentrations during freshwater adaptation of juvenile chum salmon (Oncorhynchus keta) reared in seawater for a prolonged period

Freshwater adaptability of chum salmon was examined in juvenile fish reared in seawater for 4 months. The fish, weighing about 40g, were transferred directly to fresh water in October, when their cohorts are migrating in the North Pacific Ocean. Plasma sodium concentration decreased from 167 mM in seawater to about 130 mM during the first 24h, and increased gradually during 2–7 days after the transfer. No immunoreactive prolactin (PRL) was detected in the plasma of the seawater-adapted fish nor during the first 24h in fresh water. Significant levels of PRL were detected after 2–3 days. The maximal level (2.6 ng/ml) was observed after 5 days and became undetectable again after 7 days; no significant correlation was seen between the changes in plasma sodium and PRL levels during the transfer. Plasma growth hormone levels were relatively constant, except for a significant decrease 12h after the transfer. Although plasma thyroxine levels were highly variable during the experiment, a significant decrease and an increase were observed 12h and 5 days after the transfer, respectively. The present study indicates that juvenile chum salmon retain hyperosmoregulatory ability even after prolonged rearing in seawater. Examination of turnover rates, rather than changes in plasma levels, seems to be essential to clarify the osmoregulatory roles of the hormones.     

Osmoregulatory actions of growth hormone and its mode of action in salmonids: A review

Osmoregulatory actions of growth hormone (GH) and its mode of action in salmonids are reviewed. We present evidence suggesting that insulin-like growth factor I (IGF-I) mediates some of the actions of GH on seawater acclimation. Plasma concentration and turnover of GH rise following exposure to seawater. Exogenous GH (in vivo) increases gill Na⁺,K⁺-ATPase activity and the number of gill chloride cells, and inhibits an increase in plasma osmolarity and ions following transfer of fish to seawater. A single class of high affinity GH receptors is present in the liver, gill, intestine, and kidney. The levels of IGF-I mRNA in the liver, gill and kidney increased after GH-injection. After transfer to seawater, IGF-I mRNA increased in the gill and kidney following the rise in plasma GH, although no significant change was seen in the liver. Injection of IGF-I improved the ability of the fish to maintain plasma sodium levels after transfer to seawater. GH treatment also sensitizes the interrenal to adrenocorticotropin (ACTH), increasing cortisol secretion. Both cortisol and IGF-I may be involved in mediating the action of GH in seawater adaptation, although studies on the effect of GH on osmoregulatory physiology of non-salmonid species are limited. An integrated model of the osmoregulatory actions of GH is presented, and areas in need of research are outlined.

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Résumé Cet article est une revue des effets osmorégulateurs de l'hormone de croissance et de son mode d'action. Nous présentons des résultats qui suggèrent que le facteur de croissance de type insuline (IGF-I) est un médiateur de certaines des actions de la GH sur l'adaptation à l'eau de mer. Les concentrations plasmatiques et le renouvellement de la GH augmentent après transfert en eau de mer. La GH exogène stimule (in vivo) l'activité Na⁺,K⁺-ATPase et le nombre de cellules à chlorure branchialeset inhibe les augmentations de l'osmolarité et des concentrations ioniques du plasma observées après transfert en eau de mer. Une seule classe de récepteurs à haute affinité pour la GH est présent dans le foie, les branchies, l'intestin et le rein. Les niveaux d'ARNm d'IGF dans le foie, les branchies et le rein augmentent après injection de la GH. Après transfert en eau de mer, les ARNm de l'IGF augmentent dans les branchies et dans le rein en suivant l'augmentation de GH plasmatique, bien qu'aucune modification ne soit observée au niveau du foie. L'injection d'IGF augmente la capacité du poisson à maintenir ses niveaux de sodium plasmatique après transfert en eau de mer. Le traitement à la GH augmente la sensibilité à l'adrenocorticotropine (ACTH) et stimule donc les niveaux de cortisol. A la fois le cortisol et l'IGF-I semblent impliqués comme médiateurs des effets de la GH dans l'adaptation à l'eau de mer, bien que les études sur les effets de la GH sur la physiologie de l'osmorégulation chez les espèces non-salmonidés restent encore limitées. Un modèle intégré des actions de la GH sur l'osmorégulation est présenté et les domaines de recherche à développer sont soulignés.

     

Prevalence of superficial digital flexor tendonitis and suspensory desmitis in Japanese Thoroughbred flat racehorses in 1999

REASONS FOR PERFORMING STUDY: Overstrain injuries to the superficial digital flexor tendon (SDFT) and suspensory ligament (SI) are among the most common musculoskeletal injuries which contribute to the considerable wastage of racing Thoroughbreds. Many epidemiological studies have demonstrated the prevalence of and risk factors for tendon injury when racing but have not included those injuries sustained during training. However, since tendon injury during training is seen commonly in clinical practice, it is appropriate to determine the overall prevalence of tendon injury sustained during both training and racing. OBJECTIVE: To determine the prevalence of overstrain injury to the SDFT and SL during training and racing among Thoroughbred flat racehorses in Japan in 1999. METHODS: A retrospective study was performed using a sample population of 10,262 Thoroughbred racehorses. The medical information database of Thoroughbred racehorses registered by the Japan Racing Association (JRA) in 1999 was analysed for SDFT and SL overstrain injury diagnosed by a veterinarian employed by JRA during training and racing. Jump racehorses were excluded from this study. RESULTS: The prevalence of forelimb SDFT tendonitis and SL desmitis was 11.1% (1130 cases) and 3.61% (370 cases) of the population, respectively. In the hindlimb, there were 0.06% (6 cases) and 0.14% (14 cases), respectively. Risks of SDF tendonitis in the forelimb in 3-year-olds or older horses were significantly higher than in 2-year-olds. In contrast, the risk of SL desmitis in the forelimb at age 3 and 4 years was 2.23 and 2.11 times higher, respectively, than in 2-year-olds, but this increased to 5.07 times in those age > or = 5 years. Entire males were at greater risk in comparison to females and geldings. CONCLUSIONS: The results suggest that the prevalence of SDF tendonitis and SL desmitis in the forelimb was associated with the horse's age and sex. The prevalence of SL desmitis increased further with age compared with SDF tendonitis, possibly reflecting a more rapid accumulation of degeneration in this structure. POTENTIAL RELEVANCE: The age-related risk demonstrated in this study provides further support that overstrain injuries are associated with accumulated degeneration. These data provide a valuable resource for further research into the aetiology of tendon injury in the racehorse.     

Effects of the two most common Wx alleles on different genetic backgrounds in rice

Wx^a and Wx^b are the most common alleles of the Wx gene in Asian cultivated rice. The difference between them is responsible for differences in the levels of the Wx gene product in the endosperm, as well as in amylose content, which is an important determinant of the quality of edible rice. Since Indica rice mostly carries the Wx^a allele, we introduced the Wx^b allele into Indica‐type rice (IR36) from a Japonica‐type rice (T65) by repeated backcrossing. In the near‐isogenic line (IR36 Wx^b), the level of the Wx gene product was reduced and, as expected, the level of amylose. However, IR36Wx^b had a lower amylose content than the recurrent parent of T65 with the Wx^b allele. The results suggest that the Indica (IR36) background might lower the amylose content more than the Japonica (T65) background when the Wx allele is the same. The possible importance of modifiers that regulate expression of the Wx gene is also discussed in relation to improvements in the grain quality of rice.     

Immunogold labeling of an extracellular substance producing hydroxyl radicals in wood degraded by brown-rot fungusTyromyces palustris

A fraction containing low-molecular-weight peptides that catalyzes redox reactions between electron donors and O₂ to produce ·OH, was partially purified from wood-decaying cultures of the brown-rot fungusTyromyces palustris. Polyclonal antibodies raised to the fraction were used for immunogold labeling of transverse sections of sapwood of spruce in various stages of degradation byT. palustris to demonstrate the cellular localization of the ·OH-producing substance. Initially, the wood cell wall was attacked primarily by fungal hyphae growing in the cell lumen. During the early stages of degradation, the gold label was localized in the fungal cytoplasm and cell wall and in the extracellular slime sheath surrounding the fungal cell wall. The gold label also was found throughout the wood cell wall, although the cell wall remained almost intact so long as the fungal hyphae remained in the lumen. Thus, the ·OH-producing substance is secreted by the hyphae into the lumen, and it diffuses through the S3 layer into the S2 layer and the middle lamella. The role of this ·OH-producing system in wood degradation byT. palustris is discussed.     

Examination of the onset of stable crack growth under fracture toughness testing of paper

Successive temperature distribution images around the notch tips during fracture toughness testing of paper were obtained by means of an infrared thermography system. Analysis of the images gave the critical times when the temperature significantly rose at the notch tip and when the distance between two maximum temperature spots started to decrease during the testing. Other successive microscopic images around the notch tips showed the relation between crack opening and displacement and the transitional point of the relation. The onset of stable or unstable crack growth as indicated in these critical times and the point agree with each other. For the specimen with a small width, an unstable crack starts to grow at the maximum load point without the stable crack growth period. On the other hand, a stable crack grows before the maximum load point unless the specimen width is small.The period of the stable crack growth increases with an increase in width. Differing from the methods based on thermal images to determine the onset of crack growth, the microscopic method is applicable at a wide range of strain rates and is thus suitable for quasistatic fracture toughness testing.This work was presented in part at the 8th annual meeting of the Society of Packaging Science and Technology, Japan, Tokyo, June 1999     

Cloning and expression of the human interleukin-6 (BSF-2/IFN beta 2) receptor

Interleukin-6 (IL-6/BSF-2/IFN beta 2) is a multifunctional cytokine that regulates the growth and differentiation of various tissues, and is known particularly for its role in the immune response and acute phase reactions. A complementary DNA encoding the human IL-6 receptor (IL-6-R) has now been isolated. The IL-6-R consists of 468 amino acids, including a signal peptide of approximately 19 amino acids and a domain of approximately 90 amino acids that is similar to a domain in the immunoglobulin (Ig) superfamily. The cytoplasmic domain of approximately 82 amino acids lacks a tyrosine/kinase domain, unlike other growth factor receptors.