Signal Analysis of Irradiation,Temperature and Primary Production in a Small Artificial Pond. II. The Residual Spectra

Irradiation, water temperature and dissolved oxygen of a small artificial pond were continuously recorded over a two year period. Following the elimination of previously estimated mean trends and forced annual patterns (LINGEMAN 1980) a spectral analysis procedure is proposed and executed for the residual signals of total diurnal irradiation, diel mean temperature and diurnal gross primary production. The residual power spectrum of diurnal irradiation was shown to be essentially the one of a white noise. Several higher frequencies were significantly present in both the signals of temperature and production. Some consideration is given to the cross correlation between the latter two parameters.     

Signal Analysis of Irradiation,Temperature and Primary Production in a Small Artificial Pond: I. The Annual Signals

This paper provides an example of some initial steps in signal analysis applied to a simple aquatic ecosystem in the form of a small artificial pond. Irradation, water temperature and dissolved oxygen concentration were continuously recorded over a two year period. Following the definition and discussion of several related parameters, an analysis procedure for trends and forced annual patterns was proposed and carried out. The annual pattern of photosynthetic fixation of solar energy is characterized by the annual level transfer efficiency, and for the periodic part of the process, by the transfer gain and phase shift. The possible role of temperature is briefly discussed.     

Modelling Fungal (Neozygites cf. Floridana) Epizootics in Local Populations of Cassava Green Mites (Mononychellus Tanajoa)

The fungus, Neozygitis cf. floridana is parasitic on the cassava green mite, Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) in South America and may be considered for classical biological control of cassava green mites in Africa, where cassava is an important subsistence crop, cassava green mites are an imported pest and specific natural enemies are lacking. Spider mites generally have a viscous structure of local populations, a trait that would normally hamper the spread of a fungus that is transmitted by the contact of susceptible hosts with the halo of capilliconidia surrounding an infectious host. However, if infected mites search and settle to produce capilliconidia on sites where they are surrounded by susceptible mites before becoming infectious, then the conditions for maximal transmission in a viscous host population are met. Because the ratio between spider mites and the leaf area they occupy is constant, parasite-induced host searching behaviour leads to a constant per capita transmission rate. Hence, the transmission rate only depends on the number of infectious hosts. These assumptions on parasite-induced host search and constant host density lead to a simple, analytically tractable model that can be used to estimate the maximal capacity of the fungus to decimate local populations of the cassava green mite. By estimating the parameters of this model (host density, per capita transmission rate and duration of infected and infectious state) it was shown that the fungal pathogen can reduce the population growth of M. tanajoa, but cannot drive local mite populations to extinction. Only when the initial ratio of infectious to susceptible mites exceeds unity or the effective growth rate of the mite population is sufficiently reduced by other factors than the fungus (e.g. lower food quality of the host plant, dislodgement and death by rain and wind and predation), will the fungal pathogen be capable of decimating the cassava green mite population. Under realistic field conditions, where all of these growth-reducing factors are likely to operate, there may well be room for effective control by the parasitic fungus. This revised version was published online in November 2006 with corrections to the Cover Date.     

A characterization and description of the Maarsseveen Lake system

The Maarsseveen Lakes system, located near the City of Utrecht, The Netherlands, consists of two major bodies of water, a larger lake (Maarsseveen I) and a smaller lake (Maarsseveen II), interconnected by a maze of channels known as a ‘petgaten’ area. The hydrodynamics of the lake region coupled with this ‘petgaten’ area are responsible for the maintenance of the relatively oligomesotrophic character of Lake Maarsseveen I, as compared with the more eutrophic lake maarsseveen II. Both lakes are plagued by problems of summer anoxia, although this phenomenon is far more pronounced in the more eutrophic small lake. Atmospheric deposition is responsible for contributions of significant quantities of trace metals to both lakes, and the River Vecht acts as an additional source for Lake Maarsseveen II.     

Time series of physical,chemical and plankton parameters in Lake Maarsseveen I: 1980–1986

In 1983, an unexpected bloom of the cyanobacteriaMicrocystis aeruginosa was observed in Lake Maarsseveen I. It was supposed that this phenomenon might be an indication of accelerated eutrophication of the lake. However, data on physical, chemical and phytoplankton parameters, collected over the last 6 years do not support this contention. Phytoplankton total phosphate and physical characteristics did not change. Annual levels of dissolved nutrients such as silicate and nitrate were even observed to show significant decreases over the period of observation.     

On the occurrence of bimodal diel dissolved oxygen curves in aquatic systems

Although diel dissolved oxygen curves in aquatic ecosystems usually have a unimodal shape, occasionally bimodal curves are observed. Examples of bimodal curves are found throughout literature for various types of aquatic systems; nevertheless, the phenomenon has been generally ignored. In the present study diel changes in dissolved oxygen, temperature, and irradiation were continuously monitored over a 2 year period in an artificial pond. Through analysis of variance an attempt was made to isolate the physical circumstances under which bimodal oxygen curves can be expected. It is suggested that a persistent high irradiation level and/or its accessory high rate of temperature increase and/or a usually simultaneous high rate of primary production may induce bimodal oxygen curves. However, a conclusive explanation could not be given.     

Derivatization of carboxylic acids with 4-APEBA for detection by positive-ion LC-ESI-MS(/MS) applied for the analysis of prostanoids and NSAID in urine

In order to develop a generic positive ionization ESI LC-MS method for a variety of interesting substance classes, a new derivatization strategy for carboxylic acids was developed. The carboxylic acid group is labeled with the bromine containing 4-APEBA reagent based on carbodiimide chemistry. The derivatization reaction can be carried out under aqueous conditions, thereby greatly simplifying sample preparation. In this paper, the derivatization of carboxylic acids is exemplified for the determination of prostanoids and non-steroidal anti-inflammatory drugs (NSAID). Optimization of the derivatization conditions was studied. In order to prove the applicability of the presented approach, we applied the described protocol to urine samples from complex regional pain syndrome (CRPS) patients and were able to detect several prostanoids not visible in the urine of healthy volunteers. Further, the determination of the non-steroidal anti-inflammatory drug ibuprofen in a urine sample was possible.     

Contribution of renal innervation to hypertension in rat autosomal dominant polycystic kidney disease

The kidney has both afferent (sensory) and efferent (sympathetic) nerves that can influence renal function. Renal innervation has been shown to play a role in the pathogenesis of many forms of hypertension. Hypertension and flank pain are common clinical manifestations of autosomal dominant (AD) polycystic kidney disease (PKD). We hypothesize that renal innervation contributes to the hypertension and progression of cystic change in rodent PKD. In the present study, the contribution of renal innervation to hypertension and progression of renal histopathology and dysfunction was assessed in male Han:SPRD-Cy/+ rats with ADPKD. At 4 weeks of age, male offspring from crosses of heterozygotes (Cy/+) were randomized into either 1) bilateral surgical renal denervation, 2) surgical sham denervation control, or 3) nonoperated control groups. A midline laparotomy was performed to allow the renal denervation (i.e., physical stripping of the nerves and painting the artery with phenol/alcohol). Blood pressure (tail cuff method), renal function (BUN) and histology were assessed at 8 weeks of age. Bilateral renal denervation reduced the cystic kidney size, cyst volume density, systolic blood pressure, and improved renal function (BUN) as compared with nonoperated controls. Operated control cystic rats had kidney weights, cyst volume densities, systolic blood pressures, and plasma BUN levels that were intermediate between those in the denervated animals and the nonoperated controls. The denervated group had a reduced systolic blood pressure compared with the operated control animals, indicating that the renal innervations was a major contributor to the hypertension in this model of ADPKD. Renal denervation was efficacious in reducing some pathology, including hypertension, renal enlargement, and cystic pathology. However, sham operation also affected the cystic disease but to a lesser extent. We hypothesize that the amelioration of hypertension in Cy/+ rats was due to the effects of renal denervation on the renin angiotensin system.     

Diapause survival and post-diapause performance in bumblebee queens (Bombus terrestris)

Diapause survival and post-diapause performance (i.e., if a queen starts to lay eggs) of in total 2210 bumblebee queens (Bombus terrestris) were measured under different diapause regimes: 5 temperatures (–5, 0, 5, 10 and 15 °C) in combination with 5 durations of exposure (1, 2, 4, 6 and 8 months).The results show that weight at the start of diapause determines to a large extent whether a queen will be able to survive diapause. Queens with a wet weight below 0.6 g prior to diapause did not survive, but for those queens exceeding this threshold a higher pre- diapause weight did not increase their post-diapause performance.There was no effect of temperature on diapause survival; 76% of the variance in survival could be explained by the duration of the treatment. Neither temperature nor duration of exposure had an effect on post-diapause performance. The preoviposition period of the queens that laid eggs was also determined. The preoviposition period was affected by both temperature and duration of exposure: the preoviposition period decreased with decreasing temperature but also with increasing duration of the treatment.     

Determination of denaturated proteins and biotoxins by on-line size-exclusion chromatography-digestion-liquid chromatography-electrospray mass spectrometry

A multidimensional analytical method for the rapid determination and identification of proteins has been developed. The method is based on the size-exclusion fractionation of protein-containing samples, subsequent on-line trypsin digestion and desalination, and reversed-phase high-performance liquid chromatography-electrospray mass spectrometry detection. The present system reduces digestion times to 20 min and the total analysis time to less than 100 min. Using bovine serum albumin and myoglobin as model proteins, optimization of key parameters such as digestion times and interfacing conditions between the different pretreatment steps was performed. The automated system was tested for the identification of infectious disease agents such as cholera toxin and staphylococcal enterotoxin B. This resulted typically in a positive identification by a total sequence coverage of approximately 40%.