Involvement of the cerebellum in classical fear conditioning in goldfish

To investigate the cognitive role of the cerebellum of fish, we conducted experiments examining effects of cerebellar manipulations on fear-related classical heart rate conditioning in goldfish. We performed two types of manipulations, one was total ablation of the corpus cerebelli and the other was localized cooling of the corpus cerebelli for reversible inactivation of the cerebellar function. Both the cardiac arousal response to the first presentation of the conditioned stimulus and the cardiac reflex to the aversive unconditioned stimulus were not impaired by the ablation or cooling of the corpus cerebelli. On the other hand, inactivation of cerebellar function severely impaired the acquisition of a conditioned cardiac response in the fear-related conditioning. In addition, localized cooling of the corpus cerebelli reversibly suppressed the expression of established conditioned response. We suggest that the cerebellum of fish is not only being a motor coordination center but also is involved in emotional learning

Ontogeny of gene expression of group IB phospholipase A(2) isoforms in the red sea bream, Pagrus (Chrysophrys) major

The red sea bream (Pagrus major) was previously found to express mRNAs for two group IB phospholipase A(2) (PLA(2)) isoforms, DE-1 and DE-2, in the digestive organs, including the hepatopancreas, pyloric caeca, and intestine. To characterize the ontogeny of the digestive function of these PLA(2)s, the present study investigated the localization and expression of DE-1 and DE-2 PLA(2) genes in red sea bream larvae/juveniles and immature adults, by in situ hybridization. In the adults, DE-1 PLA(2) mRNA was expressed in pancreatic acinar cells. By contrast, DE-2 PLA(2) mRNA was detected not only in digestive tissues, such as pancreatic acinar cells, gastric glands of the stomach, epithelial cells of the pyloric caeca, and intestinal epithelial cells, but also in non-digestive ones, including cardiac and lateral muscle fibers and the cytoplasm of the oocytes. In the larvae, both DE-1 and DE-2 PLA(2) mRNAs first appeared in pancreatic tissues at 3 days post-hatching (dph) and in intestinal tissue at 1 dph, and expression levels for both gradually increased after this point. In the juvenile stage at 32 dph, DE-1 PLA(2) mRNA was highly expressed in pancreatic tissue, and DE-2 PLA(2) mRNA was detected in almost all digestive tissues, including pancreatic tissue, gastric glands, pyloric caeca, and intestine, including the myomere of the lateral muscles. In conclusion, both DE-1 and DE-2 PLA(2) mRNAs are already expressed in the digestive organs of red sea bream larvae before first feeding, and larvae will synthesize both DE-1 and DE-2 PLA(2) proteins

New Universality Class of Quantum Criticality in Ce- and Yb-based Heavy Fermions

A new universality class of quantum criticality emerging in itinerant electron systems with strong local electron correlations is discussed. The quantum criticality of a Ce- or Yb-valence transition gives us a unified explanation for unconventional criticality commonly observed in heavy fermion metals such as YbRh2Si2 and \beta-YbAlB4, YbCu5-xAlx, and CeIrIn5. The key origin is due to the locality of the critical valence fluctuation mode emerging near the quantum critical end point of the first-order valence transition, which is caused by strong electron correlations for f electrons. Wider relevance of this new criticality and important future measurements to uncover its origin are also discussed.Comment: 20 pages, 4 figure

メダカ Oryzias latipesの放卵機序

メダカの放卵を誘起するサイン刺激と放卵の神経支配系を明らかにすることを目的として、一連の産卵行動のうち放卵に関わる過程の時間前推移を測定した。産卵行動の末期にメダカの雄は背鰭と尻鰭で雌を抱擁しながら、魚体を細かく振動させる。この間に放卵放精が行われる。22組のペアの産卵行動を観察した結果、メダカの雌は抱擁している雄の与える機械的刺激をある時間感受し続けると放卵することが明らかとなった(8.7±3.2秒、平均±S.D.)。抱擁の開始から放卵が起こるまでの間の適当な時点で人為的に雌雄を分離させることにより、放卵が起こるために必要な雌雄の接触時間を測定した。その結果、雌は雄からの刺激を少なくとも4秒間感受すると放卵でき、一度開始された放卵、つまり卵巣の収縮は決して中断できないことが分かった。これにより、メダカの放卵は自律神経系の関与する反射であることが示唆される。また、第10椎骨より吻側で脊髄を切断すると雌は雄からいくら刺激を受けても放卵できない。以上より、メダカの放卵は脊髄以上の中継神経系が関与する反射であり、卵巣の収縮には第9椎骨付近の脊髄から出る神経が関与することが明らかとなった。この神経は交感神経幹を経て卵巣にいたるアセチルコリン作動性の神経であると推察される。Specific stimuli required for initiating oviposition of the spawning medaka and sufficient duration of the stimuli were examined by means of measuring time durations of selected stages of the sequential spawning behaviour of the medaka. The female medaka oviposits the eggs after receiving tactile stimuli applied by the male as a vigorous body vibration, quivering, for a certain period (8.7±3.2 sec, mean±SD). By a forced separation of spawning pairs, it was determined that the sufficient duration of the stimulation for initiation of oviposition is longer than 4 sec. After the separation it was often observed that a fully stimulated female made oviposition whether willing or not. The automatism of the ovarian contraction indicates that oviposition of the medaka is a reflex mediated by the autonomic nervous system. The excitatory ovarian nerve is speculated to be emerged from the spinal cord at the level near the 10th vertebrae

土佐湾及び四国沖黒潮流域で採集されたウナギ目魚類レプトケファルス幼生の分布

土佐湾及び四隅沖黒潮流域で、1990年1月にウナギ目魚類レプトケファルス幼生の採集を行った。採集は丸稚ネット(口径1.3m、網口面積1.33㎡、目合O.33mm)による傾斜曳あるいはステップ曳と高速稚魚ネット(網口面積2.03㎡、目合2.0mm)による表層曳で行われた。計41尾のレプトケファルス幼生が黒潮流域で採れた。その内訳はギンアナゴGnathophis nystromi nystromi(JORDAN et SNYDER)(33尾)、ニラミアナゴ属sp. 5 Ariesoma sp. 5(1尾)、ニラミアナゴ属sp. 7 Ariosoma sp. 7(2尾)、クロアナゴConger japonicus BLEEKER(1尾)、クロアナゴ亜科sp. 1 Congrinae sp. 1(2尾)、メクラアナゴDysomma anguillare BARNARD(2尾)であった。全個体の82.9%(34尾)が黒潮南外側域に分布していた。またギンアナゴは全個体が表層曳で、それ以外は全でステップ曳(ワイヤー長;500, 400, 300, 200, 100m)で採集された。A total of 41 leptocephali was collected in the Kuroshio waters off Shikoku Island. They included 33 Gnathophis nystromi nystromi (JORDAN et SNYDER), one Ariosoma sp. 5, two Ariosoma sp. 7, one Conger japonicus BLEEKER, two Congrinae sp. 1, and two Dysomma anguillare BARNARD. Most of leptocephali collected (82.9% of a total catch) were occurred in the southern boundary of the Kuroshio Current. All the Gnathophis leptocephali were collected with the surface horizontal tow of High Speed Larva Net, and the other leptocephali were with step tow of Larva Net

Screening of freshwater fish species for their susceptibility to a betanodavirus.

Betanodaviruses, the causative agents of viral nervous necrosis in marine fish, have bipartite positive-sense RNA genomes. Because the genomes are the smallest and simplest among viruses, betanodaviruses have been well studied using a reversed genetics system as model viruses. However, studies of virus–host interactions have progressed slowly because permissive hosts for betanodaviruses (basically larvae and juveniles of marine fish) are only available for limited periods of the year and are not suitable for the construction of a genetic engineering system. To obtain a model fish species that are not subject to these problems, 21 freshwater fish species were injected intramuscularly with a betanodavirus (redspotted grouper nervous necrosis virus) and tested for their susceptibility to the virus. Based on their responses, the tested fish were classified into 3 groups: 4 susceptible fish, 10 less susceptible fish, and 7 resistant fish. The susceptible fish, celebes rainbowfish Telmatherina ladigesi, threadfin rainbowfish Iriatherina werneri, dwarf rainbowfish Melanotaenia praecox, and medaka Oryzias latipes, exhibited erratic swimming and eventually died within 10 d post-inoculation. The virus was specifically localized in the brains, spinal cords, and retinas of the infected fish, similar to the pattern of infection in naturally infected marine fish. We believe that these susceptible freshwater fish species could act as good host models for betanodavirus–fish interaction studies

Blood Properties and Cardiovascular Function after the Cannulation into the Dorsal Aorta in Carp, Cyprinus carpio

コイにMS222(メタアミノ安息香酸エチル・スルホン酸塩)麻酔を施し、口腔および背大動脈カニュレーション後の循環機能について検討した。コイ動脈血中の乳酸濃度は手術1時間後に約80mg/dlを示し、24時閲後に約5mg/dlにまで低下した。へモグロビン濃度と循環カテコールアミン濃度は、それぞれ手術1時間後に11～12g/dl、4～9nM/lを示したが、手術後18～24時間かけてヘモグロビン濃度は約8g/dl、循環カテコールアミン濃度は約3nM/lにまで低下した。さらに、手術1時間後に確認されたアシドーシスは6時間後に解消されたものの、動脈血pHが安定するのに18時間を要した。これらのことから麻酔、手術からの回復過程では、血液の酸素容量の増大と赤血球の酸素親和力の増強による酸素債への補償作用が重要であり、循環機能が安定するまでに要する時間は手術後18～24時間である事が明らかになった。After anesthetization with MS222 (ethyl m-aminobenzoate methanesulfonate) and cannulation into the dorsal aorta of carp, blood lactate levels decreased from 80 mg/dl to 5 mg/dl in 24 hours. Circulating catecholamines concentrations and haemoglobin concentration showed the highest values (4-9 nM/l catecholamines and 11-12 g/dl haemoglobin) at one hour after cannulation and then decreased gradually to the constant values (about 3 nM/l catecholamines and 8 g/dl haemoglobin) until 24 hours after cannulation. Acidosis occurred from one hour after cannulation and subsided at 6 hour after cannulation. Blood pH, however, was significantly higher from 6 to 12 hours after cannulation and was unstable until 18 hours after cannulation. The above changes in the circulating catecholamines concentration, the haemoglobin concentration, and the blood pH contributed to clear the oxygen debt due to MS222 anesthesia and cannulation into the dorsal aorta. The cardiovascular parameters and the blood properties of carp appear to recover to normal from sequels of the operation in 18 to 24 hours after cannulation