Incubation and maternal behaviour in domestic hens: influence of the presence of chicks on circulating luteinising hormone, prolactin and oestradiol and on behaviour

1. The consequences of the adoption of chicks and their subsequent removal on behaviour and plasma hormone concentrations of incubating hens were investigated. Birds were divided into two group: in group A, incubating hens were given chicks for 11 d; in group B chicks were left with the hens for 3 d only. 2. Incubating hens given chicks immediately showed maternal responses. The introduction of chicks induced a gradual nest desertion. Their removal stopped nest desertion temporarily on day 4 in group B hens. 3. Plasma prolactin concentrations fell one day after introduction of chicks and continued to decline for about one week in group A hens, although there was no further significant decrease in group B hens. Circulating prolactin tended to decrease with time in both groups. 4. Plasma luteinising hormone (LH) concentrations increased concurrently with the decrease of prolactin. The increase was more abrupt in group B hens. 5. Plasma oestradiol concentrations decreased slightly on the day chicks were introduced. The decline was arrested by removal of chicks in group B; in group A the tendency was reversed about 10 days after chick introduction. 6. Irrespective of group, before chick removal hens which deserted their nest rapidly had less contact with chicks and lower prolactin concentrations.     

Resistance mechanisms to DDT and transpermethrin in Aedes aegypti

Penetration, metabolism and excretion of [¹⁴C]DDT and [³H]transpermethrin were studied in three strains of Aedes aegypti L. after topical application of 10 nl of a solution of the insecticide in 2-ethoxyethanol. The standard susceptible strain was compared with a DDT-selected strain (BKS) and a permethrin-selected strain (BKPM). No significant penetration resistance was observed in either resistant strain, but both showed high DDT-dehydrochlorinase activity which contributed to the DDT resistance. A non-metabolic factor was also involved. Rates of transpermethrin metabolism were very similar in all three strains and substantially higher internal concentrations of transpermethrin were required to produce toxic effects in both BKS and BKPM mosquitoes. By analogy with other insect species, it is concluded that transpermethrin resistance in these strains is of the kdr type, while the DDT resistance is a mixture of kdr and DDT-dehydrochlorinase.     

Antagonism of chlorobenzene-induced hepatotoxicity by lindane

In two complete replicates of a 2 × 2-fractorial-designed experiment involving chlorobenzene and γ-hexachlorocyclohexane (lindane), the hepatotoxicity induced by a challenge dose of chlorobenzene was altered by the pretreatments due to selective changes in various metabolis pathways. Pretreatment with either toxicant, alone or in combination, elevated the relative metabolism of 1.12 g chlorobenzene/kg to conjugated and polar metabolites. The relative importance of these pathways was increased most by pretreatment with chlorobenzene + lindane and least with chlorobenzene. The incidence and severity of chlorobenzene-induced hepatocellular necrosis was dependent on how much the pretreatments increased excretion of these metabolites relative to that of p-chlorophenol, since the conjugates and polar metabolites represent an inactivation of the toxic chlorobenzene-3,4-epoxide whereas p-chlorophenol reflects its formation. Thus these changes in the metabolic pathways resulted in either (i) a marginally significant decrease in hepatotoxicity (chlorobenzene pretreatment); (ii) significant reduction in both the incidence and severity of the lesions (lindane pretreatment); or (iii) absence of centrilobular hepatocellular necrosis in all but 1 of 12 rats where a minimal degree of necrosis was present (chlorobenzene + lindane pretreatment). In this study, the effect of pretreatment with xenobiotics on chlorobenzene-induced hepatotoxicity was dependent on how much the pretreatments altered the inactivation of chlorobenzene-3,4-epoxide relative to its formation.     

Variations in plasma prolactin, thyroid hormones, gonadal steroids and growth hormone in turkeys during the induction of egg laying and moult by different photoperiods.

1. Concentrations of prolactin, growth hormone, testosterone, progesterone, thyroxine and triiodothyronine were measured in the blood plasma of female turkeys during successive periods of egg laying, a decline in lay, a moult induced by a short photoperiod (6 light: 18 dark) and a resumption of egg laying induced by a long photoperiod (16L:8D). 2. Concentrations of prolactin, growth hormone, testosterone and progesterone were higher in laying birds than in birds which were moulting or not laying. 3. The concentration of testosterone, but not of the other hormones studied, increased significantly during the period of profuse moult. 4. Concentrations of the thyroid hormones did not change with the varying physiological condition of the birds. However, the concentration of thyroxine was depressed by the long photoperiod.     

An Example of Cross-resistance to Pyrethroids in DDT-resistant Aedes aegypti

Comparisons of the susceptibility of several strains of adult Aedes aegypti were made. Mosquitoes from Bangkok and Jakarta were found to be highly resistant to DDT and resistant to pyrethroids relative to a laboratory strain. A strain from Singapore, where less DDT has been used, was susceptible to DDT and pyrethroids. Two strains from the Caribbean had LC₅₀ values to DDT 3 times that of the reference strain while the LC₅₀ values against bioresmethrin synergised with piperonyl butoxide were 1 1/2 times raised. Another two strains from central Africa were 2 times tolerant of DDT and 1 1/2 times tolerant of bioresmethrin plus piperonyl butoxide. Agents which block DDT-dehydrochlorinase, esterases and oxidases each caused small increases in the mortality of the Bangkok strain due to DDT and bioresmethrin as well as augmenting toxicity to the susceptible reference strain. It is tentatively suggested that resistance in the Bangkok strain is due to a combination of the actions of these and perhaps other resistance mechanisms.     

Carbon,Fossil Fuel,and Biodiversity Mitigation With Wood and Forests

Life-cycle analyses, energy analyses, and a range of utilization efficiencies were developed to determine the carbon dioxide (CO₂) and fossil fuel (FF) saved by various solid wood products, wood energy, and unharvested forests. Some products proved very efficient in CO₂ and FF savings, while others did not. Not considering forest regrowth after harvest or burning if not harvested, efficient products save much more CO₂ than the standing forest; but wood used only for energy generally saves slightly less. Avoided emissions (using wood in place of steel and concrete) contributes the most to CO₂ and FF savings compared to the product and wood energy contributions. Burning parts of the harvested logs that are not used for products creates an additional CO₂ and FF savings. Using wood substitutes could save 14 to 31% of global CO₂ emissions and 12 to 19% of global FF consumption by using 34 to 100% of the world’s sustainable wood growth. Maximizing forest CO₂ sequestration may not be compatible with biodiversity. More CO₂ can be sequestered synergistically in the products or wood energy and landscape together than in the unharvested landscape. Harvesting sustainably at an optimum stand age will sequester more carbon in the combined products, wood energy, and forest than harvesting sustainably at other ages.     

A new population of very high energy gamma-ray sources in the Milky Way

Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.