TRANSCELLULAR BIOSYNTHESIS OF CYSTEINYL LEUKOTRIENES BY KUPFFER CELL—HEPATOCYTE COOPERATION IN RAT LIVER

We previously proposed that an enzymatic cooperation between Kupffer cells and hepatocytes may play an important role in cysteinyl leukotriene (LT) production in rat liver. Anin vitrotranscellular synthesis cysteinyl LTs by a Kupffer cell—hepatocyte coculture system was characterized here. Kupffer cells alone, with A23187 stimulation, did not generate cysteinyl LTs until supplemented either with isolated hepatocytes or with LTC₄synthase and glutathione, indicating that Kupffer cells can synthesize LTA₄but not convert it into LTC₄. In contrast, hepatocytes converted the LTA₄into cysteinyl LTs and further degraded the cysteinyl LTs. Cysteinyl LT production by the Kupffer cell—hapatocyte coculture system was optimized by addition of 1–3% serum albumin to the culture and by bringing the cell—cell distance closer to less than 3μ. Tumour necrosis factor also stimulated cysteinyl LT production by the coculture system. From these results, it is expected that the Kupffer cell—hepatocyte transcellular system for cysteinyl LT production actually functionsin vivo.     

Microhabitat selection by the fishfly larva, Parachauliodes japonicus, in relation to its mode of respiration

SUMMARY. 1. Larvae of Parachauliodes japonicus (Megaloptera: Corydalidae) were tracked in streams using miniature radio-transmitters.
2. Larvae usually stayed under stones in shallow water for several days, but occasionally moved about on the stream bed at night.
3. Larvae possess a pair of respiratory tubes on abdominal segment VIII, which can be used as a snorkel to obtain oxygen from the atmosphere. Because respiratory rates decreased as dissolved oxygen decreased, larvae turned to air-breathing under lowered oxygen conditions. When in shallow water, they can alter respiratory mode from aquatic respiration to air breathing instantly by raising their caudal respiratory tubes to the surface of the water.
4. Microhabitat selection and respiratory behaviour are compared with those obtained previously for Protohermes grandis larvae, which belong to the same family and often inhabit the same stream as P. japonicus , but which have gill tufts on abdominal segments I-VII instead of respiratory tubes. The respiratory constraint on microhabitat preference by aquatic insects is discussed.     

Life history variation in a dobsonfly, Protohermes grandis (Megaloptera: Corydalidae): effects of prey availability and temperature

SUMMARY. 1. The life cycle of a predatory insect, Protohermes grandis (Megaloptera: Corydalidae), was compared in four streams in central Japan. The effects of annual temperature regime and prey availability on life history characteristics were also assessed.
2. The larval period was 2 years and small adults emerged in the Morito River, where summer water temperature was high and large prey scarce.
3. In the Nagura River, rich in large prey, the larval period was also 2 years in spite of slightly lower temperature, and the adult size was largest among the streams.
4. In Anado Fork with a low summer temperature, the larval development took 3 years, and large adults emerged. Large prey were abundant in this stream.
5. Seasonal abundance of large prey also affected the time large larvae left the stream to pupate. Larvae emigrated earlier in streams where the density of large prey sharply decreased after spring, than in streams where large prey were available throughout the year.     

In Vivo Studies on Fast and Slow Muscle Fibers in Cat Extraocular Muscles

In anesthetized in vivo preparations, responses of two types of extraocular muscle fibers have been studied. The small, multiply innervated slow fibers have been shown to be capable of producing propagated impulses, and thus have been labeled slow multi-innervated twitch fibers. Fast and slow multi-innervated twitch fibers are distinguished by impulse conduction velocities, by ranges of membrane potentials, by amplitudes and frequencies of the miniature end plate potentials, by responses to the intravenous administration of succinylcholine, by the frequency of stimulation required for fused tetanus, and by the velocities of conduction of the nerve fibers innervating each of the muscle fiber types.     

Response of Chlamydomonas to Temperature Change

SYNOPSIS. Response of Chlamydomonas to temperature change was investigated. When the temperature of the medium was suddenly increased (decreased) the abrupt velocity rise (drop) was observed. This abrupt velocity change was induced immediately after the temperature change. Then, the high (low) level of the velocity was maintained for a few minutes. Finally the velocity decreased (increased), tending to a stationary level at the new temperature with the decay time of a few minutes. The rate of the temperature change determined the magnitude of response. The threshold value was found in the rate of the temperature change to produce the transient change of the velocity. It was ∼ 0.2 C/sec.     

Consequences of hybridization between Ohomopterus insulicola and O. arrowianus (Coleoptera, Carabidae) in a segmented river basin: parallel formation of hybrid swarms

A putative hybrid zone between flightless earabid beetles, (iambus (Ohomopterus) insulicola and C. (0.) arrowianus nakamurai in the Ina Valley, central Honshu. Japan, was studied using experimental hybridization and morphological analysis. The principal morphological character analysed was a functional part of the male genitalia (the eopulatory piece), which is also the key diagnostic character in taxonomy. The habitat of the earabid beetles is fragmented by the Tenryu River, which runs through the Ina Valley, and its tributaries. Ohomopterus insulicola and 0. a. nakamurai occur in the upstream and downstream areas of the river basin, respectively, and a putative hybrid swarm (0. insulicola ssp. pseiidinsulkola) is found in the boundary area on the cast side of the Tenryu River. Experimental hybridization between 0. insulicola and 0. a. nakamurai resulted in F₁ offspring that were morphologically similar to 0. i. pseudinsulicola. Pre‐zygotic reproductive isolation was incomplete, although the F₁ males had a dysfunction in sperm production and were almost sterile. Only a single F₁ pair produced F₂, Backcrosses of F₁ females of males of the parental species resulted in offspring that were similar to the parental species in genital morphology. Based on the discriminant function for the shape of the eopulatory piece resulting from the experimental hybridization, we demonstrate that similar hybrid swarms exist on both sides of the Tenryu River, but in locations 25 km apart. This demonstrates parallelism in hybridization events with similar consequences. The hybrid swarms consisted of beetles with intermediate morphological characters and did not contain obvious parental forms. The establishment of such intermediate populations may have been facilitated by selection for fertile hybrids in segregated local sites in the absence of frequent immigration of parental species. This study suggests that a segmented river basin provides an opportunity for establishing novel evolutionary lineages resulting from hybridization.     

Prey selection by the dobsonfly larva, Protohermes grandis (Megaloptera: Corydalidae)

SUMMARY 1. Prey selection by the dobsonfly larva, Protohermes grandis (Thunberg), was studied in stony riffles of the Yataro River, central Japan. The density, size distribution and taxonomic composition of available prey were assessed for 2 years. In order to know the encounter rate between prey and this ambush predator, prey mobility was also estimated from patterns of colonization of experimentally detiuded stones.
2. Foregut analyses revealed that maximum size of prey eaten increased with larval size, and large larvae did not take the smallest prey in spite of high availability in all seasons.
3. Charnov's (1976) optimal diet model quantitatively predicted such size-selective feeding under seasonally fluctuating conditions of water temperature and prey availability. Larvae maximized the feeding rate by selecting prey.
4. Maximum width of prey eaten coincided approximately with larval mandible length. Mandible size seemed to play an important role in the selection of prey in the optimal size range.     

PHOTOCHEMICAL ACTIVITIES OF SONICATED LAMELLAE OF SPINACH CHLOROPLASTS WITH SPECIAL REFERENCE TO THE ACTION OF CRS (CYTOCHROME C REDUCING SUBSTANCE)

The photooxidation of reduced DPIP with NADP and O₂ as finalelectron acceptors was studied with sonicated lamellae of spinachchloroplasts, with special reference to the possible role ofCRS, a newly discovered factor of photochemical system I. Acorrelation between inactivation of NADP-photoreduction anddissolution of CRS was observed on treatment of the lamellaewith various organic solvents. The treatment also suppressedthe O₂-linked photooxidation of reduced DPIP, although the suppressionwas not so marked as in the former reaction. The suppressedphotooxidation of reduced DPIP (with O₂ and NADP as electronacceptors) was partially restored on addition of dyes of negativeredox potential, such as methyl viologen. The experimental resultsindicate that a factor participates in the reactions of photochemicalsystem I, probably functioning as an electron carrier couplingthe photooxidation of P700 with the reduction of ferredoxinor O₂. The finding that the above mentioned activity of thefactor is destroyed by treatments which are effective in solubilizingCRS from the chloroplasts suggests the identity of the factorwith CRS. ¹ Present address: Nomura Research Institute of Technology andEconomics, Kamakura, Kanagawa.     

Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis(Megaloptera: Corydalidae)

SUMMARY 1. Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis ,was studied by measuring the oxygen consumption rate (resting metabolism) bimonthly for 2 years. The respiratory rate of the larva was significantly lower during the summer season when the stream temperature rose to 30°C.
2. Summer depression of respiration was confirmed by measuring the rate of carbon dioxide evolution. The mean value of the respiratory quotient was estimated to be 0.76 ± 0.05 SE. The larva is believed to conserve energy by this reduction in respiratory rate,
3. In other seasons, however, the larva maintained a higher respiratory rate and remained active even in the winter when the stream temperature decreased near to 0°C. In fact, significant growth in weight occurred from mid-October to late March.
4. This acclimation to temperature may enable the efficient allocation of energy during the long larval period (3 years) in streams which have large annual fluctuations in temperature.