Possible evolution of alliarinoside biosynthesis from the glucosinolate pathway in Alliaria petiolata

Nitrile formation in plants involves the activity of cytochrome P450s. Hydroxynitrile glucosides are widespread among plants but generally do not occur in glucosinolate producing species. Alliaria petiolata (garlic mustard, Brassicaceae) is the only species known to produce glucosinolates as well as a γ-hydroxynitrile glucoside. Furthermore, A. petiolata has been described to release diffusible cyanide, which indicates the presence of unidentified cyanogenic glucoside(s). Our research on A. petiolata addresses the molecular evolution of P450s. By integrating current knowledge about glucosinolate and hydroxynitrile glucoside biosynthesis in other species and new visions on recurrent evolution of hydroxynitrile glucoside biosynthesis, we propose a pathway for biosynthesis of the γ-hydroxynitrile glucoside, alliarinoside. Homomethionine and the corresponding oxime are suggested as shared intermediates in the biosynthesis of alliarinoside and 2-propenyl glucosinolate. The first committed step in the alliarinoside pathway is envisioned to be catalysed by a P450, which has been recruited to metabolize the oxime. Furthermore, alliarinoside biosynthesis is suggested to involve enzyme activities common to secondary modification of glucosinolates. Thus, we argue that biosynthesis of alliarinoside may be the first known case of a hydroxynitrile glucoside pathway having evolved from the glucosinolate pathway. An intriguing question is whether the proposed hydroxynitrile intermediate may also be converted to novel homomethionine-derived cyanogenic glucoside(s), which could release cyanide. Elucidation of the pathway for biosynthesis of alliarinoside and other putative hydroxynitrile glucosides in A. petiolata is envisioned to offer significant new knowledge on the emerging picture of P450 functional dynamics as a basis for recurrent evolution of pathways for bioactive natural product biosynthesis.     

The effects of 884 MHz GSM wireless communication signals on headache and other symptoms: an experimental provocation study

Findings from prior studies of possible health and physiological effects from mobile phone use have been inconsistent. Exposure periods in provocation studies have been rather short and personal characteristics of the participants poorly defined. We studied the effect of radiofrequency field (RF) on self-reported symptoms and detection of fields after a prolonged exposure time and with a well defined study group including subjects reporting symptoms attributed to mobile phone use. The design was a double blind, cross-over provocation study testing a 3-h long GSM handset exposure versus sham. The study group was 71 subjects age 18-45, including 38 subjects reporting headache or vertigo in relation to mobile phone use (symptom group) and 33 non-symptomatic subjects. Symptoms were scored on a 7-point Likert scale before, after 1(1/2) and 2(3/4) h of exposure. Subjects reported their belief of actual exposure status. The results showed that headache was more commonly reported after RF exposure than sham, mainly due to an increase in the non-symptom group. Neither group could detect RF exposure better than by chance. A belief that the RF exposure had been active was associated with skin symptoms. The higher prevalence of headache in the non-symptom group towards the end of RF exposure justifies further investigation of possible physiological correlates. The current study indicates a need to better characterize study participants in mobile phone exposure studies and differences between symptom and non-symptom groups.     

Intensive fish predation: an obstacle to biological recovery following liming of acidified lakes?

Several thousand lakes have been limed inNorway and Sweden during the last threedecades. Most fishless lakes are stocked withsalmonid game fish after liming, predominantlybrown trout (Salmo trutta). Thecombination of intensive anthropogenic stockingand improved natural reproduction possibilitiesin brooks and rivers often leads to denselypopulated lakes and excess fish planktivory.Another major fish species in southern Norway,Eurasian perch (Perca fluviatilis),exhibits strong numerical increases afterliming, and within a short period of time thelakes harbor dense and often stuntedpopulations. The cladoceran zooplanktoncommunity was used as a diagnostic tool forstudying fish status, patterns and processes oflakes in the present area. Systems that werelimed before all fish species were lost, andbefore major dominance shifts had taken placewithin the invertebrates, recovered morequickly. Recovery periods are severelyprolonged in strongly disturbed, chronicallyacidified ecosystems. The control of fishabundance in optimal human resource managementof limed lakes is a delicate balance betweenthe necessity to suppress potentialinvertebrate predators and fish competitorssuch as corixids and chaoborids, and to avoidover-exploitation of the planktonic and benthiccommunities. If the combined watershed and lakesystem does not naturally produce sub-optimalspawning and recruitment possibilities, eitherfor brown trout or Eurasian perch, resulting insmaller populations, chances are high that thesite will lose its attraction as a fishingobject due to overpopulation. This should be amajor field of concern both for the ecology ofthese lakes and their resource management bythe fishery and environmental officials.     

Protective somatic antigen of Corynebacterium diphtheriae

Deoxycholate C. diphtheriae extract was separated into fractions differing in the size of their molecules. Correlation between the molecular weight of each fraction, its specific protein content and its immunogenicity was observed. The high-molecular fraction (mol. wt. exceeding 300,000 daltons) was shown to be the protective somatic antigen of C. diphtheriae.     

Ultrastructure of the Cuticle of Loricifera and Demonstration of Chitin using Gold-Labelled Wheat Germ Agglutinin

The pharyngeal and lorical cuticles of adult and larval Loricifera were investigated by transmission electron microscopy. LR White sections of larval and adult Loricifera were labelled with the lectin wheat germ agglutinin (WGA) conjugated to colloidal gold. The pharyngeal cuticle of Nanaloricus mysticus exhibits a multilaminate epicuticle and an amorphous basal layer with osmiophilic fibres. The lorical cuticle consists of an osmiophilic or trilaminate epicuticle, one to three amorphous layer(s), and a basal fibrous layer which is strongly labelled by the lectin-gold conjugate. Chitinase treatment or competitive inhibition with N-, N '-, N "-triacetylchitotriose exclude labelling almost completely, whereas competitive inhibition with N -acetyl-D-glucosamine does not affect labelling intensity. The binding of WGA in connection with competition experiments indicates the presence of chitin in the fibrous layer. In most areas of a section, three amorphous layers extend below the epicuticle of the Nanaloricidae. Only in favourably orientated sections can all three "amorphous" layers be seen to be formed by stacks of lamellae. Modified articulation sites with bundles of osmiophilic longitudinal fibres and an osmiophilic plate (Nanaloricidae only) occur in adult Loricifera, but not in the larval stages. The ultrastructure of the lorical cuticle of the Loricifera resembles that of other Nemathelminthes (= Aschelminthes). The morphology of the articulation sites and the number of lorical plates seem to differ between the Loricifera and Priapulida. Therefore, it is currently not possible to conclude whether the lorica of the Loricifera and Priapulida are homologous structures. © 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.     

On the rotifer plankton of some East African lakes

Slightly alkaline and strongly alkaline lakes were investigated. A rather varied rotifer fauna was found in the first category, while in the second group, no rotifers at all or, at the most, only one species was found.