Comparative transmission of, and varietal reaction to, three isolates of rice tungro virus disease

Comparative transmission by leafhoppers of three tungro isolates obtained from the Philippines, India and Malaysia, and of an infectious clone of the Philippine isolate of rice tungro bacilliform virus (RTBV) by agroinoculation, was conducted on 12 rice cultivars. The symptoms, including height of inoculated plants were recorded and the efficiency of RTBV and rice tungro spherical virus (RTSV) transmission was determined by enzyme-linked immunosorbent assay. In most cases, the reduction of height and leaf symptoms of plants infected with RTBV and/or RTSV by the three isolates were similar in any given cultivar. On cultivar ASD 7 , the Malaysian isolate showed more severe yellow orange leaf discolouration symptoms than the Indian isolate which in turn had more severe leaf discolouration than the Philippine isolate. On the other hand, cultivars ASD 7 and Ptb 18 produced the most severe yellow orange leaf discolouration when agroinoculated with an infectious RTBV clone of the Philippine isolate. There was some variation in the transmission profile of the two tungro viruses among the three isolates. However, there was no one clear set of characteristics by which one could use cultivars to distinguish isolates. The amount of viral DNA in agroinfected plants of cultivars Utri merah, Balimau putih, Utri Rajapan and ARC 11554 was low, while the amount was high in cultivars TN1, ASD7, Ptb 18 and TKM 6. There was high correlation between the amount of viral coat protein by ELISA and viral nucleic acid by DNA hybridisation on 10 agroinoculated rice cultivars; this might indicate that similar proportions of the total RTBV DNA are encapsidated in each cultivar.     

A comparison of yolk growth rates in seabird eggs

The duration and rate of yolk deposition in the formation of avian eggs are species specific and are apparently fixed characteristics. We determined these properties for eggs from 40 species of marine birds. The mass of yolk laid down daily during rapid yolk deposition in the ovary was calculated and used to construct and compare yolk enlargement curves for each species. The spectrum of curves are all best fitted by simple second-order polynomial regression equations, with the very rapidly enlarging yolks of Alcidae at one extreme and the slow-forming eggs of Procellariiformes at the other. Calculated daily energy allocation to yolk deposition during the last, and most demanding, phase of yolk formation ranged from 3% to 44% of standard metabolic rate, considerably lower than other estimates.     

Some Biochemical Abnormalities Caused by Cypermethrin in Adults of Tribolium castaneum (Herbst.)

Biochemical effects of sub lethal doses LC₁₀ and LC₂₀ of cypermethrin were studied on some enzymes and macromolecule activities of adult beetles of Tribolium castaneum (Herbst.). Cypermethrin caused disturbances in levels of all biochemical components under study. The dose of 0.78 ppm caused abnormalities in α‐amylase and FAA by increasing their activities i.e., 45.45% and 21.97% significantly. The higher sub lethal dose of 2.62 ppm disturbed all the parameters (AcP, α‐amylase, soluble protein and FAA) except AkP, which was decreased by 93.06%. Moreover, sub lethal doses either increased or decreased the levels of all parameters non‐significantly except AkP and FAA which were effected significantly by 87.92% and 14.29% at lower and higher doses, respectively. In the present studies, cypermethrin significantly enhanced the activity of AkP in both susceptible and resistant strains of T. castaneum adult beetles while FAA contents were increased significantly in resistant strain only. The activity of α‐amylase was significantly lowered in susceptible strain only.     

USE OF SENSORY EVALUATION FOR MEASURING DEODORIZING EFFECTS OF AN AIR CONDITIONER

The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R² values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures.     

A Role for Ecdysteroids in the Induction and Maintenance of the Pharate First Instar Diapause of the Gypsy Moth,Lymantria dispar

Several lines of evidence suggest a novel regulatory mechanism for diapause regulation in the gypsy moth. We propose that ecdysteroids play a role in the induction and maintenance of the pharate first instar larval diapause in this species. A 55 kDa gut protein that is indicative of diapause is expressed in intact and neck-ligated pharate larvae but is not expressed when a ligature is placed posterior to the prothorax, site of the prothoracic gland. Guts cultured in vitro for 12 h cease to synthesize the 55 kDa protein, but synthesis of the protein resumes if the culture medium is enriched with a prothorax extract from pharate larvae or a prothoracic gland extract from fifth instar larvae. Injection of 20-hydroxyecdysone or the ecdysteroid agonist, RH-5992, into isolated abdomens stimulates synthesis of the diapause-specific 55 kDa protein, suggesting that the essential factor from the prothorax is an ecdysteroid. KK-42, an imidazole derivative known to inhibit ecdysteroid biosynthesis, averts diapause when applied to prediapausing pharate first instar larvae, but this effect can be countered by application of 20-hydroxyecdysone or RH-5992, i.e. KK-42 treated pharate larvae that are exposed to an ecdysteroid or RH-5992 readily enter diapause. A chilling period (120 days at 5 degrees C) is normally adequate to prompt an immediate termination of diapause when pharate larvae are transferred to 25 degrees C, but if such larvae are held in hanging drop cultures with ecdysteroids they fail to terminate diapause. Together, these results suggest that ecdysteroids are essential for the induction and maintenance of diapause and imply that a drop in the ecdysteroid titer is essential for diapause termination. Copyright 1997 Elsevier Science Ltd. All rights reserved     

Statural growth in known-age African elephants (Loxodonta africana)

The shoulder heights of 224 females and 170 males, and hindfoot length of 236 female and 217 male known-age African elephants ( Loxodonta africana ) were measured, and growth curves constructed for each measure of size. A linear relationship between foot length and shoulder height was confirmed in simultaneous measures of 97 males and 110 females. Growth curves demonstrated the typical sexual dimorphism in both foot length and shoulder height, with males growing more rapidly than females from birth onwards. The size dimorphism in foot length and shoulder height becomes marked by the age of 10 years, with males on average being 60–70 cm taller than females at 65 years. This size dimorphism is produced through faster growth which continues for longer than does that of females. The variance in growth rates is slightly greater for females than for males. It is proposed that female growth after puberty is affected by a trade-off between growth and reproduction, while males who deviate markedly from typical patterns of growth may be subject either to mortality or energetic constraints limiting their potential variance.     

A multivariate approach to the selection of biological reserves

Multivariate analysis provides an effective context for the examination of some significant aspects of biodiversity and conservation. The framework is a multidimensional space that integrates sample sites, taxa and environments. This approach enables terms such as representativeness, complementarity and irreplaceability to be integrated within an intuitive and practical framework for reserve design. Cluster analysis is proposed to determine what is there by defining a set of complementary clusters. These clusters are sampled in a representative manner; from the core outward. The degree of irreplaceability of a site is defined as the multivariate distance of each potential reserve site to its nearest neighbour.