Inhibition of the growth of cariogenic bacteria in vitro by plant falvanones

Phytoalexins, defensive compounds produced by plants against microbial infections, were purified fromSophora exigua (Leguminosae) and their growth inhibitory effects on oral cariogenic bacteria were determined in vitro. Among three isolated compounds, 5,7,2,4-tetrahydroxy-8-lavandulylflavanone completely inhibited the growth of oral bacteria including primary cariogenic mutans streptococci, other oral streptococci, actinomycetes, and lactobacilli, at concentrations of 1.56 to 6.25 g/ml.     

<Emphasis Type="Italic">Naja siamensis</Emphasis>, a cryptic species of venomous snake revealed by mtDNA sequencing

Because of possible variation in venom composition, an understanding of venomous snake systematics is of great importance for the optimization of antivenom treatment of snakebite patients. Intraspecific variation in the morphology of many venomous snakes complicates the definition and indentification of some species when allopatric populations are involved. Selectively neutral or near-neutral mtDNA sequences can reveal evolutionary relationships obscured by ecogenetically-caused morphological variation. We use comparative sequencing of the cytochrome oxidase subunit 1 gene to reveal the existence of a widespread, cryptic species of spiting cobra from southeast Asia. This species,Naja siamensis, is widely sympatric with other Asiatic cobra species. This may be of considerable medical significance, and calls for further research into venom composition in Asiatic cobras.     

Variability of sterol utilization in stored-products insects

A comparison of sterol utilization by 3 stored-products insects revealed very different capabilities. The fluor beetle,Tribolium castaneum dealkylates and converts dietary sitosterol to about equal amounts of cholesterol (43.7%) and 7-dehydrocholeterol (39.8%), whereas another flour beetle,Tenebrio molitor, produces considerably less 7-dehydrocholesterol (16.8%) and relatively more cholesterol (66.7%) from sitosterol. The lepidopteran,Plodia interpunctella, utilized dietary sterol very similar to plant-feeding lepidoptera, producing primarily cholesterol (86.5%) from sitosterol.     

A novel mechanism for jumping in the indian ant<Emphasis Type="Italic">Harpegnathos saltator</Emphasis> (Jerdon) (Formicidae,Ponerinae)

The Indian antHarpegnathos saltator may be unique among insects in using its jumping capacity not only as an escape mechanism but also as a normal means of locomotion, and for catching its prey in flight. High-speed cinematography used to analyse the various phases of the jump suggests thatHarpegnathos employs a novel jumping mechanism to mediate these behaviours: namely the synchronous activation of its middle and hindlegs. Electrophysiological recordings from muscles or nerves in pairs of middle and hindlegs show remarkably synchronous activity during fictive jumping, supporting the synchronous activation hypothesis.Harpegnathos is not the only ant to jump, and a cladistic analysis suggests that jumping behaviour evolved independently three times during ant evolutionary history.     

Influence of bistramide A on the twitch tension in rat atrial heart muscle

Bistramide A, a new toxin isolated from the UrochordateLissoclinum bistratum Sluiter, was applied to rat auricular heart muscle bundles. At a stimulation frequency of 0.2 Hz, the toxin induces a dose-dependent reduction of the stimulated twitch tension force; it decreases and shortens the duration of the plateau and the slow repolarizing phase of the action potential. In the control solution, switching from a stimulation frequency of 0.2 Hz to 1 Hz decreases the force with which a positive potentiation develops either at a maintained high frequency or after switching from 1 Hz to 0.2 Hz. Bistramide A reduces both the force evoked at 1 Hz and the potentiation. The data suggest that Bistramide A blocks Na⁺ conductance; inhibits Ca⁺⁺ channels in a time-and frequency-dependent manner; reduces Na⁺–Ca⁺⁺ exchange activity; but does not modify the ability of the sarcoplasmic reticulum to be refilled although the rate of Ca⁺⁺ accumulation is decreased.     

The in vivo expression of the globin genes of theβ cistron in γ-,δ-, andδβ-thalassemia heterozygotes

There is considerable evidence suggesting that the switch from to and chain production after birth is due, in part, to silencing of the genes by stage-specific factors which bind to their promoters and to the competition from the adult ( and ) genes for a common enhancer element located in the locus control region. As a consequence one can expect that the increased Hb F production in adults with hereditary persistence of fetal hemoglobin or -thalassemia is directed mainly by -globin genes in cis to the deletion(s) responsible for these conditions. Here we review data on heterozygotes with -, -, or -thalassemia, who also had an^AT mutation, in cis or in trans, which was used as a marker of gene expression. The results show that a deletion affecting adult genes favors the expression of genes in cis, while the deletion of a single gene does not affect the expression of the gene in cis but leads to a faster switch postnatally.     

Detection of toxic metabolites in the hemolymph ofBeauveria bassiana infectedSpodoptera exigua larvae

Highly active metabolites have been detected in the hemolymph of the lepidopteranSpodoptera exigua infected with the mycopathogen,Beauveria bassiana. A combination of phenyl sepharose and CM ion exchange chromatography was utilized to extract the active metabolites from infected hemolymph samples. The active in vivo metabolites, having a molecular mass greater than 10 KDa, were thermolabile and were inactivated by proteinase K. These metabolites were characterized by their ability to disrupt metamorphosis, killing treated larvae at the wandering or pupal stage. Additionally, injection ofS. exigua larvae with active samples caused a reduction in the number of filopodial-producing hemocytes. The biological activities and biochemical properties suggest that novel compounds are produced duringB. bassiana mycosis.     

‘Action substances’ of peripheral nerve re-visited

Fifty years ago, four action substances were described as being liberated from peripheral nerve in the course of activity. An attempt has been made to update this information. Confirmatory evidence is available that acetylcholine and thiamine do play a role in the course of activity. However, the question of the relationship in time between their release and the electrical events, and the possible effect on specific ionic gating mechanisms, remains unclarified. The liberation of potassium has been found to be a transmembrane K efflux, and the question of the existence of another substance similar to thiamine has not been pursued.a member of the Editorial Board of EXPERIENTIA from 1974 to 1982     

Pineal ‘synaptic’ ribbon numbers and melatonin synthesis of rat are resistant to guanethidine sympathectomy

Chemical sympathectomy is widely used to study the impact of the noradrenergic system on neuronal and neuroendocrine circuits. We tested the effects of intraperitoneal injections of guanethidine, an adrenergic neuron blocking agent, on selected functional parameters of the rat pineal gland which are known to be under sympathetic influence. The reliability of the method was demonstrated by the clear enophthalmus developed by experimental animals. However, neither the numbers of synaptic ribbons nor melatonin synthesis differed between treated and control rats, both parameters exhibiting the nocturnal increase seen in intact animals. These results are in striking contrast to those obtained upon chemical sympathectomy with 6-hydroxydopamine or surgical superior cervical ganglionectomy. We conclude that guanethidine is not capable of sufficiently removing noradrenergic influence from the rat pineal gland, and that this substance is thus inferior to other experimental methods of sympathectomy.     

Presence of hsp65 in bacterial extracts (OM-89): A possible mediator of orally-induced tolerance?

Heat shock proteins (HSP) have been implicated in rodent models of autoimmunity, particularly arthritis, and there is suggestive though inconclusive evidence that they may also play a role in human autoimmune disease. The simplest hypothesis is based on molecular mimicry due to the amino-acid sequence homology between mammalian and microbial HSP. Recently OM-89, an extract of several strains ofEscherichia coli, has shown some efficacy in the treatment of rheumatoid arthritis (RA) when taken orally. Using species-specific antibodies, we show here that OM-89 contains the 65 kDa HSP (hsp65), while hsp65 was not detected in another bacterial extract containing other microorganisms, includingStaphylococcus aureus (OM-85). We suggest that if the human homologue of hsp65 is a relevant target antigen in the human disease, the efficacy of the preparation could be due to induction of oral tolerance or to switching the Th1 response towards Th2. Alternatively, even if the human hsp65 is not a target molecule in RA joints, OM-89 may evoke bystander suppression of joint inflammation via induction of TGF-secreting effector cells. These hypotheses should be tested in further studies.