Lipopolysaccharide O-chain microheterogeneity of Salmonella serotypes Enteritidis and Typhimurium

Variability in the lipopolysaccharide (LPS) of the two most prevalent Salmonella serotypes causing food-borne salmonellosis was assessed using gas chromatography analysis of neutral sugars from 43 Salmonella enterica serovar Enteritidis ( S . Enteritidis) and 20 Salmonella enterica serovar Typhimurium ( S . Typhimurium) isolates . Four substantially different types of O-chain chemotypes were detected using cluster analysis of sugar compositions; these were low-molecular-mass (LMM) LPS, glucosylated LMM LPS, high-molecular-mass (HMM) LPS and glucosylated HMM LPS. Nineteen out of 20 S . Typhimurium isolates yielded glucosylated LMM . In contrast, S . Enteritidis produced a more diverse structure, which varied according to the source and history of the isolate: 45.5% of egg isolates yielded glucosylated HMM LPS; 100% of stored strains lacked glucosylation but retained chain length in some cases; and 83.3% of fresh isolates from the naturally infected house mouse Mus musculus produced glucosylated LMM LPS. A chain length determinant ( wzz ) mutant of S . Enteritidis produced a structure similar to that of S . Typhimurium and was used to define what constituted significant differences in structure using cluster analysis. Fine mapping of the S . Enteritidis chromosome by means of a two-restriction enzyme-ribotyping technique suggested that mouse isolates producing glucosylated LMM LPS were closely related to orally invasive strains obtained from eggs, and that stored strains were accumulating genetic changes that correlated with suppression of LPS O-chain glucosylation. These results suggest that the determination of LPS chemotype is a useful tool for epidemiological monitoring of S . Enteritidis , which displays an unusual degree of diversity in its LPS O-chain.     

In Vivo NO/cGMP Signalling in the Hippocampus

In the hippocampus of freely-moving rats, basal extracellular levels of cGMP are inhibited by L-NARG or ODQ whereas they are increased by NO donors or phosphodiesterase inhibitors. Activation of NMDA receptors also augments cGMP dialysate levels in a MK-801 and L-NARG sensitive manner, an effect dramatically diminished during ageing. Experiments with AMPA, AMPA receptor antagonists and cyclothiazide revealed complex relationships with GABAergic circuits that potently control the NO/cGMP pathway. Furthermore, the activity of this neurochemical cascade is also modulated by hippocampal nicotinic receptors via enhancement of endogenous glutamate release and stimulation of NMDA receptors. From a behavioural point of view, increased hippocampal excitation leads to the appearance of epileptic-like manifestations that, however, seem unrelated to the increase of NO/cGMP formation.     

Animal and worker exposure to dust and biological particles in animal care houses

An aerobiological study was performed to evaluate the potential exposure of animals and workers to dust constituents generated during routine animal house work. Different rooms of air conditioned (A, control) and passively ventilated (B, non-air conditioned) animal facilities were sampled, in order to evaluate total airborne culturable fungi and bacteria, fungal spore concentrations and particle levels. Airborne room particles were analyzed gravimetrically and for endotoxin content. All parameters, except for culturable fungi, were higher in facility B and statistically significant, with respect to those from the control facility A. Median values for airborne particle concentration, endotoxin and fungal spores in facility B were: 115 µg m^–3, 25 EU m^–3, and 2173 spores m^–3, respectively. Median values for facility A were: 66 µg m^–3, 9 EU m^–3, and 248 fungal spores m^–3. Broncheoalveolar lavage from rats kept in the rat room of B, presented median concentrations of total cells and lactate dehydrogenase, higher than those found in the control facility (4.4 × 10⁵ vs. 1.1 × 10⁵ and 2.7 UmL^-1 vs. 0.39 UmL^–1, respectively). Values of total and biological particles of both facilities, as well as the time spent in different rooms, showed that worker exposure was higher during cage washing. It was especially high in the passively ventilated facility (airborne particles 686 µg m^–3 3.5 h^–1 vs. 976 µg m^–3 3.5 h^–1, endotoxin 70 EU m^–3 3.5 h^–1 vs. 108 EU m^–3 3.5 h^–1). The type of basidiospores and ascospores found, as well as the significant correlation between particle levels and endotoxin contents suggests that wood chip bedding disturbance during cage washing is an important source for airborne biological particles. The changes in broncheoalveolar lavage components found in rats from these facilities and previously reported changes in pro-inflammatory cellular responses found in workers, indicate that these relatively low levels of exposure are enough to induce a biological response. Studies considering the composition of mixed organic dusts, would be needed to reevaluate current occupational standards.     

Bildung von Mitochondrien in der regenerierenden Leber der Maus

Zusammenfassung 46 Stunden nach der Teilhepatektomie, d.h. während des Höhepunktes der progressiven Phase der Regeneration der Leber, ist das endoplasmatische Retikulum der Parenchymzellen örtlich stark erweitert. Durch eine progressive Transformation der erweiterten Cisternen entstehen durch Bildung von Doppelmembranen, Cristae und einer Matrix über mehrere Zwischenstationen regelrechte Mitochondrien.Neben Unterbrechungen der äußeren Mitochondrienmembran und der Membran des endoplasmatischen Retikulum wurde auch beobachtet, daß die Membranen ineinander übergehen können. Diese Verbindungen könnten durch einen membrane flow einen aktiven Transport von Substanzen in das Innere der Mitochondrien ermöglichen.Die morphologischen Befunde, die für eine Entstehung der Mitochondrien aus dem endoplasmatischen Retikulum und die Bildung der microbodies im glatten Anteil desselben sprechen, werden im Zusammenhng mit einigen biochemischen Ergebnissen der Literatur diskutiert.Jefe de Trabajos Prácticos del Instituto de Patología General y Experimental, Mendoza, Argentina, zur Zeit Stipendiat der Alexander von Humboldt-Stiftung.     

Robertsonian polymorphism in house mouse<Emphasis Type="Italic">Mus musculus domesticus</Emphasis> from an area of intense seismic activity

This paper presents a case study of the chromosomal complement of 16 miceMus musculus domesticus Linnaeus, 1758 from the region near one of the most recent disastrous earthquakes in Italy (named Umbria-Marche 1997), with the aim of examining chromosomal variability among the mice from the seismically active zones. For the present investigation, the sampling sites were chosen in the vicinity of some active faults, supposedly the main earthquake generators in the area. In the three localities, that lie approximately on the fault lines, mice with a reduced chromosomal number (2n = 36 to 39) were trapped. This reduction is due to the presence of three different Robertsonian metacentrics — Rb(9.14), Rb(10.12) and Rb(15.17) — in both the homozygous and heterozygous states. Mice trapped in four localities more distant from the fault zone only had the standard karyotype (2n = 40). These results increase the need to analyze in more detail the distribution of karyotypes in relation with active faults.     

Evolution of a climbing habit promotes diversification in flowering plants

Key innovations are traits that are associated with the particular evolutionary 'success' of some taxonomic groups. Climbing plants depend on the availability of physical support to reach the canopy and thereby prevent shading by neighbouring plants. The present article shows that the evolution of a climbing habit in flowering plants constitutes a key innovation. A literature survey identified 48 pairs of sister groups from 45 families of flowering plants for which information on phylogenetic relationships, growth habit and species richness was available. In 38 cases, the climbing taxa were more diverse than their non-climbing sister groups. This pattern was highly significant. The same result was found when separate analyses were carried out for herbaceous and woody climbing plants, which differ in their constraints for successfully reaching a support.     

Studies in imitative behavior: A generalization of the rashevsky model; Its mathematical properties

This paper is based on N. Rashevsky's theory of imitative behavior, the underlying idea being that performance of one reaction by a given individual produces an increased stimulation (or tendency) toward the same reaction in other individuals. For simplicity, consideration is limited to cases in which each individual may choose only between two (or two main categories of) reactions, denoted byA andB in the following. However, upon suggestion from Dr. Rashevsky and certainly in better agreement with actual facts, the strength of imitative interaction is assumed to vary from individual to individual. More precisely, if Ψ_i denotes the additional excitation caused by imitation in theith individual,PA_i the probability for performance of reactionA, andPB_i the probability for performance of reactionB by theith individual, we postulate that where the constants α _ik ^′ and β _ik ^′ (coefficients of imitative interaction) measure the amount of imitative influence exerted by thekth individual upon theith,N being the total number of individuals in the population. The term — α_i Ψ_i accounts for the spontaneous decay of excitation, and the quantities α _ik ^′ and α _ik ^′ are assumed to benon-negative. The expressions forPA_i andPB_i are obtained from H. D. Landahl's theory of conflicting stimuli; they depend non-linearly on the values Ψ_i. It is implicit in this formulation that the theory can only be applied if the frequency of contacts between individuals is not too small. Some further shortcomings and limitations of the model are outlined, and the discussion includes suggestions for reinterpretation and improvement of the theory. If all the quantities α _ik ^′ and α _ik ^′ have the same value, sayA, we return to the case treated by Rashevsky (and Landau, 1950); these authors, however, replace the sums in the equation above by integrals, which automatically restricts the validity of their results to very large values ofN. Their work may therefore be characterized by the assumption of uniform interaction in large populations. Our equations, on the other hand, are applicable even to very small groups, and therein lies one of their main advantages. In this paper the mathematical properties of the non-linear system of equations above are studied with particular reference to the existence and stability of steady states [dΨ_i/dt ≡ 0;, i = 1 , 2, . . . N]. A sufficient condition for the existence of only one stable steady state is derived. It may be formulated roughly by stating that all the coefficients of interaction should be sufficiently small. It that is not the case, there may exist a greater number of stationary states. In particular, two of them (called “extremal”) have the following properties: they arestable and such that the average number of individuals in the group performing one or the other reaction is the largest (or smallest) possible as compared with the other steady states. Hence the situation is qualitatively similar to that found by Rashevsky and Landau.Quantitatively, however, important differences may arise, depending on the nature of the matrix specifying the interaction. A stable state may be approached through damped oscillations, but this effect is important only if the damping is sufficiently small for the oscillations to become practically observable. Little information could be obtained on this point, due to mathematical difficulties. As mentioned above, the most interesting applications of this theory will be with respect to small populations or to populations partitioned into subgroups with varying amounts of imitative interaction within as well as between groups.     

Application of the disulfide trapping approach to explain the antiparallel assembly of dimeric rabbit uteroglobin: A preliminary study using short peptide models

The spontaneous air oxidation of the peptides H-GICPRFAHVIENLL- NH2 and Ac-LPQTTRENIMKLTEKIVKSPLCM-OH, whose sequences correspond to the helicoidal fragments 1–14 and 48–70 of the monomer of rabbit uteroglobin, was studied. While no oxidation products were observed in the absence of trifluoroethanol, the heterodimer was formed selectively in the presence of the structuring agent. Head-to-head and tail-to-tail homodimers were not detected under these conditions. These results suggest that the N- and C- terminal extremes of the monomer of uteroglobin might contain enough structural information to govern dimerization with a head-tail topology, through a selective helix-to-helix recognition process.     

Effects of experimental stress factors on probing behaviour by aphids

Probing behaviour of Aphis fabae Scopoli and Rhopalosiphum padi (L.) was tested in different stress situations normally occurring in aphid-plant studies such as interruption of feeding or starvation, transfer to a new plant, and attachment to the electrode wire. The DC electrical penetration graph (EPG) technique and a honeydew clock were used to collect data on behavioural effects of these stress conditions. As a general effect, an interruption of feeding behaviour acted as a reset, i.e., the same sequence and time course of probing events were shown, irrespective the interruptions duration, from 1–100 min. Nevertheless, some minor differences were found, especially in A. fabae. Increased interruption times (deprivation from the host plant) stimulated the aphids to insert their stylets earlier. When A. fabae was put back on its host plant after a one min interruption phloem feeding started earlier than with longer interruption times, but only when it was put back to the same plant and feeding site on which it fed before. It is concluded that this effect is at least partly due to memory of previous probing/feeding experience on the plant as it vanishes with longer interruption times. This explanation also holds for phloem salivation (E1) before starting sustained sap ingestion, which was reduced on the previous feeding site, but only after the one min interruption in A. fabae. The aphid-plant specificity appeared high in these effects. Both aphids were somewhat affected by wiring, resulting in earlier probing, longer total pathway phase, and less and later phloem feeding (as reflected by honeydew excretion). Thus confirming, that the evaluation of EPG results can be improved with supplementary data from free aphids.