Functional organisation of anterior thoracic stretch receptors in the deep-sea isopod Bathynomus doederleini: Behavioural, morphological and physiological studies

The relationship between segmental mobility and the organisation of thoracic stretch receptors was examined in the deep-sea isopod Bathynomus doederleini, which shows a developed adaptive behaviour during digging. The movements of segments during digging were analysed from video recordings, which showed that a large excursion occurred in the anterior thoracic segments. Dyefills of axons revealed four types of thoracic stretch receptor (TSR): an N-cell type (TSR-1), a differentiated Ncell type (TSR-2), a muscle receptor organ (MRO)-type with a long, single receptor muscle (TSR-3) and an MROtype with a short, single receptor muscle (TSR-4 to TSR-7). Physiologically, TSR-1 and TSR-2 are tonic-type stretch receptors. TSR-3 to TSR-7 show two kinds of stretchactivated responses, a tonic response and a phasico-tonic response in which responses are maintained as long as the stretch stimulus is delivered. Both TSR-2, with a long muscle strand, and TSR-3, with a single, long receptor muscle, have a wide dynamic range in their stretchactivated response. In addition, TSR-2 is controlled by an intersegmental inhibitory reflex from TSR-3. These results suggest that, although TSR-1 has no receptor muscle and TSR-2 has a less-differentiated receptor-like muscle, they are fully functional position detectors of segmental movements, as are the MRO-type receptors TSR-3 to TSR-7.</p

Studies on the physiology and ecology of Porphyra tenera

Cultivation of the red sea-weed Porphyra tenera was started in Japan several centuries ago. It is now the largest industrial cultivation of any marine products. Despite this fact, more knowledge of Porphyra is needed for improving methods of cultivation-to bring them under a control comparable to that achieved in land agriculture. In this paper, the results of ecological and physiologicav studies on P. tenera are contained. I. Ecology. Environmental characteristics both on Matsushima Bay (Miyagi pref.) and Matsukawa-ura inlet (Fukushima pref.), where the cultural industries are practising, were investigated. Several factors affecting the production of Porphyra were clarified from the results of survey. These results are summarized in Figs. 1-18, and Tables 1-4. The relation between the growth of Porphyra thalli and the environmental factors were also examined (Figs. 19-30, and Tables 5-7). II. Nutrition. Experimental results on mineral nutrition of P. tenera are shown m Figs. 31-35, and Tables 8-12. Axenic culture of P. tenera was obtained by the "dip and drag" technique in an agarized medium containing antibiotics. Then, vitamins requirements and effects of plant hormones were examined. The results are indicated in Tables 13-14. In axenic culture of P. tenera needs vitamin B12 for growth. III. Artificial management of the life-cycle. The complete life-cycle of P. tenera was obtained in vitro. Chemically defined media or enriched sea-water permit good growth of these unialgal (not bacteria-free) cultures. Under suitable light and temperature, the entire life-cycle is completed in 5-6 months. Both the Conchocelis and the thallus phases grow out of season. The Conchocelis phase grows well free in liquid media; a calcareous substrate is unnecessary. Monosporangia formation and release of fertile monospores are induced by short-day conditions (8-11 hours daily); monosporangia and germinating monospores develop after 1-2 months from the inoculation of the Conchocelis filaments (Table 16). A daily photoperiod of 13 hours inhibits growth of young thalli. Carpospores production are induced by long-day conditions (Table 18). The experiments show that the length of the photoperiod has remarkable effects on the Conchocelis and leafythallus phases of P. tenera. The photoperiod governs, besides growth, the formation of the spores producing the next phase of the life-cycle.本研究の一部は文部省科学研究助成金でなされた事を附記して併せて謝意を表する

Role of the Schizosaccharomyces pombe F-box DNA helicase in processing recombination intermediates.

In an effort to identify novel genes involved in recombination repair, we isolated fission yeast Schizosaccharomyces pombe mutants sensitive to methyl methanesulfonate (MMS) and a synthetic lethal with rad2. A gene that complements such mutations was isolated from the S. pombe genomic library, and subsequent analysis identified it as the fbh1 gene encoding the F-box DNA helicase, which is conserved in mammals but not conserved in Saccharomyces cerevisiae. An fbh1 deletion mutant is moderately sensitive to UV, MMS, and ¿ rays. The rhp51 (RAD51 ortholog) mutation is epistatic to fbh1. fbh1 is essential for viability in stationary-phase cells and in the absence of either Srs2 or Rqh1 DNA helicase. In each case, lethality is suppressed by deletion of the recombination gene rhp57. These results suggested that fbh1 acts downstream of rhp51 and rhp57. Following UV irradiation or entry into the stationary phase, nuclear chromosomal domains of the fbh1¿ mutant shrank, and accumulation of some recombination intermediates was suggested by pulsed-field gel electrophoresis. Focus formation of Fbh1 protein was induced by treatment that damages DNA. Thus, the F-box DNA helicase appears to process toxic recombination intermediates, the formation of which is dependent on the function of Rhp51

Studies on the red tide dinoflagellates-I. : On Entomosigma sp. appeared in coastal area of Fukuyama

　1966年，福山市田尻附近に赤潮として出現したEntomosigma sp. をミクロピペット法で分離して無菌培養を行ない，その生理，生態について観察実験を行なうとともに栄養要求に関する二，三の実験を行ない，その発生要因について検討した. 1)この生物の至適塩分濃度は海水より僅かに低いS28.9‰ (Cl16.0‰)附近である. 2)海水lこ微量金属類および弱キレート剤(NTA) が添加されると，それぞれ50%，80 %程度増殖が促進される. 3)至適pHは7.5 で海水より低く， pH=7.5 からのずれとともに増殖は減少する. 4) 一般に海水lこ窒素，燐を添加するだけでEntomosigma sp. の増殖は促進されるが， その割合は海水の穏類によって異なる. 5) ビタミンB12 はこの生物の増殖に不可欠の重要素である. B12 類似物のうち，ベンジミダゾールを持つコパテミンはB12 と同じように作用し，B12 の代用ができる.この生物のB12 要求特性はOchromonas型といえる. 　以上の結果から，この赤潮の発生は降雨による降水の大量流入が主な原因と考えることができそうである.The red tide that appeared in the coastal area of Fukuyama, June 1966, was caused by the microscopic dinoflagellate Entomosigma sp. Since this red tide came after rainfall, it was implied that the organism might prefer low salinities and perhaps nutrients washed into the sea from the land. From this hypothesis, laboratory culture was started. Entomosigma sp. was obtained in axenic culture by micropipette washings. The organism prefers slightly low salinity (Cl 16.0‰), yet, tolerates a wide range of salinities. The growth is accelerated by the trace metals and/or the weak chelator, nitrilotriacetic acid, to sea water. Supplement of nitrogen and phosphorus sources to sea water favors growth. Entomosigma sp. needs vitamin B12 for growth. The pattern of specificity is similar to that of Ochromonas malhamensis. All the analogues containing benzimidazole can replace B12 • These results seem to substantiate the above hypothesis.本研究の一部は昭和41 ，42年度農林水産特別試験研究費補助金でなされたことを附記し，あわせて感謝の意を表する