Seismic signal transmission between burrows of the Cape mole-rat,Georychus capensis

Summary Both seismic and auditory signals were tested for their propagation characteristics in a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by alternately drumming its hind legs on the burrow floor. Signal production in this species is sexually dimorphic, and mate attraction is likely mediated primarily by seismic signalling between individuals in neighboring burrows. Measurements within, and at various distances away from, natural burrows suggest that seismic signals propagate at least an order of magnitude better than auditory signals. Moreover, using a mechanical thumper which could be triggered from a tape recording of the mole-rat's seismic signals, we established that the vertically-polarized surface wave (Rayleigh wave) propagates with less attenuation than either of the two horizontally-polarized waves. Thus, we tentatively hypothesize that Rayleigh waves subserve intraspecific communication in this species.Abbreviations PPM pulses per min - SB simulated burrow - SD standard deviation - SPL sound pressure level     

Plant oligoadenylates: enzymatic synthesis, isolation, and biological activities

An enzyme that converts [3H, 32P]ATP, with a 3H:32P ratio of 1:1, to oligoadenylates with the same 3H:32P ratio was increased in plants following treatment with human leukocyte interferon or plant antiviral factor or inoculation with tobacco mosaic virus. The enzyme was extracted from tobacco leaves, callus tissue cultures, or cell suspension cultures. The enzyme, a putative plant oligoadenylate synthetase, was immobilized on poly(rI) . poly(rC)-agarose columns and converted ATP into plant oligoadenylates. These oligoadenylates were displaced from DEAE-cellulose columns with 350 mM KCl buffer, dialyzed, and further purified by high-performance liquid chromatography (HPLC) and DEAE-cellulose gradient chromatography. In all steps of purification, the ratio of 3H:32P in the oligoadenylates remained 1:1. The plant oligoadenylates isolated by displacement with 350 mM KCl had a molecular weight greater than 1000. The plant oligoadenylates had charges of 5- and 6-. HPLC resolved five peaks, three of which inhibited protein synthesis in reticulocyte and wheat germ systems. Partial structural elucidation of the plant oligoadenylates has been determined by enzymatic and chemical treatments. An adenylate with a 3',5'-phosphodiester and/or a pyrophosphoryl linkage with either 3'- or 5'-terminal phosphates is postulated on the basis of treatment of the oligoadenylates with T2 RNase, snake venom phosphodiesterase, and bacterial alkaline phosphatase and acid and alkaline hydrolyses. The plant oligoadenylates at 8 X 10(-7) M inhibit protein synthesis by 75% in lysates from rabbit reticulocytes and 45% in wheat germ cell-free systems.(ABSTRACT TRUNCATED AT 250 WORDS)     

The biochemical and behavioral effects of phospholipase A2 and morphine microinjections in the periaqueductal gray of the rat

In order to characterize the in vivo action of phospholipase A2 (PLA2) on opiate receptors and opiate-induced behaviors, the effects of injections of PLA2 into the periaqueductal gray region (PAG) of the rat were assessed on free fatty acid (FFA) release, opiate-binding levels, and morphine-induced behaviors. Rats received bilateral PAG injections of 2 micrograms of PLA2 while anesthetized. One hour later, regions around the cannulae tracts in PLA2-treated rats contained over 2.5 times more FFA than saline-injected controls, and 3H-dihydromorphine binding was reduced on average more than 70%. In another series of experiments, conscious rats were given 2 micrograms of PLA2 prior to 10 micrograms of morphine through cannulae chronically implanted into the PAG. PLA2 did not significantly attenuate morphine-induced analgesia as measured by the tail-flick test to radiant heat, but did prevent the explosive motor behavior observed following morphine injections alone. PLA2 by itself did not induce analgesia, but did cause explosive motor behavior 2 hr after the injections. Neither lysophosphatidylcholine nor trypsin resulted in motor seizures following PAG injections. It was concluded that the behavioral effects of PLA2 result from the unique properties of the enzyme, rather than generalized membrane damage, and that the opioid sites and mechanisms that mediate analgesia are different from those associated with explosive motor behavior.     

Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence

Natural selection, in the form of balancing selection or selective sweeps, can result in a decoupling of the amounts of molecular polymorphism and divergence. Thus natural selection can cause some areas of DNA sequence to have greater silent polymorphism, relative to divergence between species, than other areas. It would be useful to have a statistical test for heterogeneity in the polymorphism to divergence ratio across a region of DNA sequence, one that could identify heterogeneity greater than that expected from the neutral processes of mutation, drift, and recombination. The only currently available test requires that a region be arbitrarily divided into sections that are compared with each other, and the subjectivity of this division could be problematic. Here a test is proposed in which runs of polymorphic and fixed sites are counted, where a "run" is a set of one or more sites of one type preceded and followed by the other type. The number of runs is smaller than otherwise expected if polymorphisms are clumped together. By simulating neutral evolution and comparing the observed number of runs to the simulations, a statistical test is possible which does not require any a priori decisions about subdivision.      

The Influence of Antimicrobial Peptides and Mucolytics on the Integrity of Biofilms Consisting of Bacteria and Yeasts as Affecting Voice Prosthetic Air Flow Resistances

The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses after biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance.