DNA radiation damage and asymmetric somatic hybridization: Is UV a potential substitute or supplement to ionising radiation in fusion experiments?

Recent reports have revealed that the asymmetric nature of the nuclear genome of somatic hybrids, produced following the irradiation of one of the parents with X- or gamma rays, is generally much less than had been anticipated. As a consequence, we have begun to investigate whether UV radiation might be used as an alternative or indeed a supplement to the presently-used ionising radiation techniques in such experiments. Cell culture studies have revealed that UV radiation induces the desired physiological effects in sugar beet ( Beta vulgaris ) protoplasts, namely, a prevention of cell division without immediate cytotoxicity. Preliminary studies using denaturing and pulsed field gel electrophoresis have shown that UV can also induce substantial physical fragmentation of DNA. When using the same techniques, less breakdown was observed following gamma radiation. All results were highly reproducible. Such results augur well for the potential use of UV in asymmetric somatic cell fusion experiments.     

Impact of the field slug Deroceras reticulatum on establishment of ryegrass and white clover in mixed swards

The relationship between numbers of Deroceras reticulatum and the establishment of ryegrass cv. Melle and white clover cv. Milkanova was studied on a mini-plot experiment. Assessments 12 and 33 days after sowing showed that Deroceras reticulatum had a proportionally greater impact on survival and growth of clover than on ryegrass. Slugs had no apparent effect on numbers or growth of three species of broad-leaved weeds (Senecio vulgaris, Cardamine hirsuta and Epilobium sp.) which occurred in the field experiment. In pot experiments where seedlings of ryegrass together with one of three clover cultivars, with or without chickweed (Stellaria media), were exposed to Deroceras reticulatum, seedlings of white clover cv. Aran were less affected by slug grazing than cvs S184 or Milkanova. The presence of different clover cultivars did not significantly influence the impact of slugs on growth of ryegrass or chickweed, nor did the presence or absence of chickweed influence the effect of slugs on ryegrass and clover seedlings. Slugs had less impact on the growth of chickweed than on ryegrass or clover. Thus slug grazing would make clover less able to compete with chickweed as well as the other weeds found in the mini-plot experiment.     

INTERACTIONS BETWEEN KURIL SEALS AND SALMON TRAP NET FISHERY IN THE COASTAL WATERS OF SOUTHEASTERN HOKKAIDO

An annual average of 163 Kuril seals was found dead in two years in salmon trap nets along the coastal waters of the Nemuro Peninsula and adjacent areas. The seal-caused damage to the total salmon catch at the salmon trap nets was concentrated in some of them, particularly No. 27, where seals killed or injured 5.1% of the catch in 1982, and 1.8% in 1983. Based on the proportion of Kuril seals among the dead seals in the trap nets, it was estimated that Kuril seals damaged 4.7% of the total salmon catch at No. 27 in 1982, and 1.7% in 1983. Not all seals that entered the trap net drowned; some killed or damaged salmon, and then escaped.     

Explant organ culture: A review

Organ explant culture models offer several significant advantages for studies of patho-physiologic mechanisms like cell injury, secretion, differentiation and structure development. Organs or small explants/slices can be removed in vivo and maintained in vitro for extended periods of time if careful attention is paid to the media composition, substrate selection, and atmosphere. In the case of human tissues obtained from autopsy or surgery, additional attention must be paid to the postmortem interval, temperature, hydration, and cause of death. Explant organ culture has been effectively utilized to establish outgrowth cell cultures and characterize the histiotypic relationships between the various cell types within an organ or tissue.J. Resau is a visiting scientist at the NCI-LMO-DCE in Frederick, MD 21702, U.S.A.K. Sakamoto is a visiting scientist from the Department of Surgery, Gunma University School of Medicine, Maebashi, Japan     

The effect of vitamin E analogues and long hydrocarbon chain compounds on calcium-induced muscle damage. A novel role for α-tocopherol?

Previous studies have demonstrated that supplemental α-tocopherol inhibited calcium-induced cytosolic enzyme efflux from normal rat skeletal muscles incubated in vitro and suggested that the protective action was mediated by the phytyl chain of α-tocopherol [1]. In order to investigate this further a number of hydrocarbon chain analogues of tocopherol (7.8-dimethyl tocol, 5,7-dimethyl tocol, tocol, α-tocotrienol, α-tocopherol [10], vitamin K1, vitamin K1 [10], vitamin K1 diacetate, vitamin K2 [20], phytyl ubiquinone and retinol) were tested for any ability to inhibit calcium ionophore, A23187, induced creatine kinase (CK) enzyme efflux. Some compounds were found to be very effective inhibitors and comparison of their structures and ability and to inhibit TBARS production in muscle homogenates revealed that the effects did not appear related to antioxidant capacity or chromanol methyl groups, but rather the length and structure of the hydrocarbon chain was the important mediator of the effects seen.     

Glucocorticoids inhibit the induction of nitric oxide synthase and the related cell damage in adenocarcinoma cells

Lipopolysaccharide (LPS) induced a time-dependent synthesis of nitric oxide (NO) in EMT6 adenocarcinoma cells, assayed by accumulation of NO-derived nitrite in the medium. The induction NO synthesis was inhibited in a concentration-dependent manner by the glucocorticoids dexamethasone (IC₅₀ = 5 nM) and hydrocortisone (IC₅₀ = 20 nM) and this effect was partially antagonized by progesterone and cortexolone. If addition of dexamethasone was delayed 6 h or more, inhibition of nitrite accumulation over 24 h was substantially reduced, indicating a lack of direct effect of glucocorticoids on the NO synthase. Nitrite accumulation was accompanied by cell damage, which was increased by L-arginine and inhibited by $\text{N}{}^{\mathrm{<mtext>G</mtext>}}\text{-}\text{monomethyl-}\text{L}\text{-arginine}$ (L-NMMA) and dexamethasone. These data show that NO is a primary cytotoxic mediator and that suppression of its formation by glucocorticoids explains some of their anti-inflammatory and cytoprotective effects.     

Effect of Ozone on the Activities of Reactive Oxygen Scavenging Enzymes in Rbc of Ozone Exposed Japanese Charr (Salvelinus Leucomaenis)

The effect of ozone exposure on the activities of reactive oxygen scavenging enzymes (SOD†, catalase, GSH-Px) in RBC of Japanese charr (Salvelinus leucomaenis) was examined. Ozone (0, 0.4 and 0.7 ppm as initial concentrations) was exposed to Japanese charr for 30 min, which definitely caused serious membrane damage to RBC of fish. Ozone exposure at 0.4 and 0.7 ppm decreased activities of both catalase and GSH-Px by 80 to 57+ of the control. On the other hand, the activities of SOD remained unaffected even by 0.7 ppm ozone exposure. A hypothesis on the RBC membrane damage and participation of SOD and heme-iron was proposed.     

Studies on organ weights in naproxen treated rats after intermittent exposure to simulated high altitude

Rats were exposed intermittently for 8h per day over 6 days at simulated high altitude of 20 000 feet. One group of altitude-exposed animals was treated with naproxen, a prostaglandin inhibiting drug. Significant reduction in body weight gain was observed in both altitude-exposed and drug-treated altitude-exposed animals compared to the control group. Right and left ventricular weights and weights of the adrenal glands were increased significantly in altitude-exposed and altitude-exposed drug-treated animals. The weight of the spleen was increased significantly in altitude-exposed animals whereas no such increase of splenic weight was observed in drug-treated altitude-exposed group of animals. On the other hand, the weight of the liver was decreased significantly in both cases. In drug-treated altitude-exposed animals, the unaltered splenic weight was thought to be due to inhibition of the erythropoietic activity.     

Effect of seed depth on slug damage to winter wheat

In a field experiment drilled at two depths on three dates in autumn 1988, with or without methiocarb pellets broadcast on the soil surface immediately after drilling, 26% of seeds of winter wheat sown at c. 20 mm depth were killed by slugs compared with only 9% of seeds sown at c. 40 mm. The protection from slug damage provided by this additional 20 mm of depth was comparable with that provided by methiocarb pellets. The effects of seed depth and pellet application did not interact and were consistent on all drilling dates. Thus, fewest seeds and seedlings were killed where methiocarb pellets were broadcast on a seed-bed with seeds sown at 40 mm depth. Intermediate damage was recorded where seeds were sown at 40 mm depth without pellets, or where pellets were broadcast on seeds sown at 20 mm depth. Most seeds and seedlings were killed where seeds were sown at 20 mm depth without pellets. Sublethal damage to seedlings was not affected by sowing depth but was reduced where pellets were broadcast immediately after sowing.     

Structural damage to oak leaves alters natural enemy attack on a leafminer

A field experiment was conducted to test the role of structural changes in oak leaves caused by folivory on natural enemy attack of leafmining larvae and pupae of Cameraria sp. nov., while controlling for induced chemical responses. Damaged and intact leaves of Quercus emoryi were sealed with a fluorocarbon telomer in 1988–1989 to prevent release of long-range or contact chemical cues that might be perceived by searching parasitoids and predators. These leaves were attached to Q. emoryi leaves harboring first instars of Cameraria, but otherwise were undamaged. Rates of attack by natural enemies of leafminers in leaves with sealed, damaged leaves attached were significantly greater than those in control leaves, indicating that structural damage alone influences attack by natural enemies. Survival of leafminers in leaves with attached damaged leaves was significantly less than that of controls, suggesting that structural changes in leaves due to folivore feeding affect population dynamics of Cameraria via increased attack by the third trophic level.

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Résumé Des expériences ont été faites dans la nature pour évaluer l'influence des modifications structurales provoquées par la défoliation sur les attaques des ennemis naturels des chenilles mineuses et des chrysalides de Cameraria sp. nov. En 1988–89 des feuilles saines et endommagées de Quercus emoryi ont été enduites de télomère de fluorocarbone pour empêcher l'émission d'indicateurs chimiques à distance ou de contact pouvant être utilisés par les parasitoïdes et les prédateurs lors de leur prospection. Ces feuilles ont été attachées à des feuilles apparemment intactes de Q. emoryi mais hébergeant des Cameraria du premier stade. Les attaques par les ennemis naturels des mineuses étaient plus importantes sur feuilles associées à des feuilles endommagées mais enduites de fluorocarbone que sur feuilles témoins, ce qui montre que les dégâts structuraux seuls influent sur les attaques par les ennemis naturels. La survie des mineuses dans les feuilles associées à des feuilles endommagées était plus faible que chez les témoins, ce qui suggère des changements structuraux dans les feuilles provoqués par les phytophages affectant la dynamique de population de Cameraria via une attaque accrue par le troisième niveau trophique.