How costly is clutch formation in the Audouin's Gull Larus audouinii?

During the Audouin's Gull's breeding season at the Ebro Delta in 1993, 24 fresh eggs from eight three-egg clutches (modal clutch-size) were collected at the peak of the laying period. Eggs were processed to obtain formalin-fixed yolks, which were halved and stained using the potassium dichromate method. Digitized images of the yolks were examined to assess the daily rates of yolk deposition. We used these data in combination with egg compositional analysis to build a model of energy demands during the formation of an average clutch in Audouin's Gull. To show how the different parameters of clutch formation affect the daily energy investment peak, we performed a simulation analysis in which the rapid yolk development (RYD) period, the follicle triggering interval (FTI), the laying interval (LI) and the albumen synthesis period (ASP) were allowed to vary simultaneously. In our sample, the mean RYD period was seven days with a range from six to eight days. There were no significant differences in yolk volume among eggs in a clutch, but albumen volume was significantly smaller in third eggs. According to our model the albumen synthesis of the a-egg coincides with the energy demand peak for clutch formation. This peak represents an increase by ca. 42% in female energy requirements. Values obtained from the simulation analysis showed that only the ASP of the a-egg and the RYD durations of the second and third follicles produced noticeable reductions in peak energy investment. We predict that in gulls, whose laying intervals seem to be kept constant, significant increases of the durations of the RYD periods of second and third eggs, or even significant reductions of yolk size of these eggs, may operate simultaneously to match the energy demands during clutch formation to the prevailing food conditions.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Intraperitoneal injection of chloral hydrate causes intra-abdominal adhesions and unilateral testicular atrophy in golden Syrian hamsters.

We investigated the reason for the high mortality we had observed in hypophysectomized-orchidectomized Golden Syrian hamsters that were anesthetized with intraperitoneal (i.p.) injections of chloral hydrate (CH). Intact male Golden Syrian hamsters were injected intraperitoneally with 0.1cc/100g BW of a 35% solution of CH, a 35% solution of sodium chloride, or double-distilled water. Equal numbers of hamsters in each group were injected on the right or left side of the abdomen. Within 10 days, 35% of the CH-injected hamsters were dead or had to be euthanized. Autopsy revealed severe peritonitis and adynamic ileus. CH-injected hamsters that survived gained weight at a rate similar to that of the controls. All surviving hamsters were killed 18 days after the injections. Among the surviving CH-injected hamsters, 84.6% had intra-abdominal adhesions, 61.5% had unilateral testicular atrophy, and 53.8% had a yellowish necrotic mass in the epididymal fat pad (EFP). All the lesions occurred on the side that was injected. The atrophied testes had been rendered cryptorchid due to involvement with intra-abdominal adhesions. In the water-treated controls, there were no abnormalities; whereas, in the saline controls, 75% had a mass in the EFP. Histology of the EFP mass was similar in hamsters injected with CH or hypertonic saline and suggested a diagnosis of fat necrosis. The results suggest that the mortality, the intra-abdominal adhesions, and the unilateral cryptorchidism were caused by a single i.p. injection of CH, but the fat necrosis in the EFP was probably caused by high concentrations of salt. The results further suggest that high concentrations of CH should not be injected intraperitoneally for anesthesia in chronic studies, particularly of the male reproductive system.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

The Michaelis constants of a nonchromogenic substrate may be determined using a chromogenic substrate

A general method is presented for the determination of the KM and Vmax for a nonchromogenic substrate in an experimental system where a chromogenic and a nonchromogenic substrate compete for the active site of a single enzyme. Entire progress curves of absorbance versus time for the transformation of the chromogenic substrate must be obtained in the absence and presence of the nonchromgenic substrate. Two quantities may then be extracted from the entire kinetic curves: the value of a delta Area, the area bounded by the kinetic traces of absorbance versus time in the presence and absence of the nonchromogenic substrate; and the value of delta t(5%), the time required to transform 5% of the chromogenic substrate in the presence of the nonchromogenic substrate minus the corresponding time required in its absence. The values of KM and Vmax for the nonchromogenic substrate may be obtained from the dependencies of delta Area and delta t(5%) upon the concentration of the nonchromogenic substrate. The ability of this procedure to yield the correct values of KM and Vmax was demonstrated using beta-lactamase, beta-galactosidase, alkaline phosphatase, and 19 chromogenic/nonchromogenic substrate pairs. This method is equally valid in the absence or presence of competitive product inhibition and should be applicable to any enzyme-catalyzed, strongly exergonic reaction.     

Effect of chronic ingestion of iodide during pregnancy and lactation on rat pup brain enzymes

The developmental pattern of several key enzymes in brain of pups born to mothers receiving high levels of iodide (1.1 mg daily intake) during pregnancy and lactation were followed up to the weaning period. We found that in the initial states of postnatal development, glutamic dehydrogenase increased above control levels, whereas succinic dehydrogenase decreased. At late stages, we observed differences in phosphofructokinase and malic enzyme activities which were all increased at 30 days. There was no change in hexokinase. Animal weight did not vary with respect to controls and we only obtained discrete increases (not statistically different) in serum thyroxine values, which led us to assume that the enzymatic modifications might be a consequence of either a very mild hormonal alteration or to the direct effect of iodide.     

Suicide vector for transposon mutagenesis in Pseudomonas solanacearum.

A suicide vector was constructed by cloning the transfer genes of the wide-host-range (IncW group) plasmid R388 into the BamHI site of pBR325. This plasmid can deliver Tn5 into Pseudomonas solanacearum at frequencies ranging from 10(-6) to 10(-9) per recipient.