Influence of hydrodynamic environment on composition and macromolecular organization of structural polysaccharides in Egregia menziesii cell walls

To test whether secondary and tertiary structures of marine-algal structural polysaccharides may be altered during adaptive responses to hydrodynamic stresses, juvenile Egregia menziesii (Turn.) Aresch. sporophytes were cultured under three different regimes: (i) low-energy (LE) specimens were subjected to water motion produced by standard bubbling and circulation of tank water; (ii) high-energy (HE) specimens received additional movement in pumped streams of water; and (iii) stretched (STR) specimens were grown under low-energy conditions but also were subjected to constant, longitudinal tension (0.7 N). After 6–10 weeks growth, cell-wall structural polysaccharides from specimen blades were isolated by solubilizing less-ordered matrix polysaccharides. Neutral-sugar and uronic acid contents of these isolates were measured, and samples were analyzed by x-ray diffraction and by Raman and ¹³C-nuclear magnetic resonance (NMR) spectroscopy. On average, structural polysaccharides formed about 7.2% of dry-weight biomass. The portion of isolated mass accountable to neutral sugars ranged from an average of 85% for STR sporophytes to 94% for both LE and HE specimens. For all specimens, glucose composed an average of 99% of this fraction. Uronic acids could not be detected in isolates from any treatment group. Cellulose dominance in each isolate was indicated clearly in x-ray diffraction patterns and in Raman and ¹³C-NMR spectra. These data further demonstrated that both the cellulose I allomorph and the disordered form of the polymer were present in each isolate and that the STR isolate contained small quantities of the cellulose II allomorph. In general, the LE and HE samples had very similar crystallinity; lateral order was slightly more developed in LE samples. However, the STR treatment produced cellulose with lowest crystallinity and least lateral order. Results suggest that mechanical stress modified cellulose crystallinity in these kelps by altering levels of disordered cellulose and lateral dimensions of cellulose crystallites and, in one instance, changed the crystallinity qualitatively. Physical disturbances to cell plasma membranes may have instigated these trends. In the STR specimens in particular, such disturbances might have been supplemented by fundamental changes to kelp physiology, affecting both substantial decreases in crystallinity and production of the cellulose II allomorph. Changes in the nature of the cellulose cannot, however, account for changes in the elastic moduli.Abbreviations CP/MAS cross polarization/magic angle spinning - HE high energy - LE low energy - NMR nuclear magnetic resonance - STR stretched The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.     

The survival of some soil mites at different humidities and their reaction to humidity gradients

The survival at different humidities of 10 species of soil mites in larval, nymphal and adult stages has been investigated. The immature forms are almost as resistant as mature but differences exist between species. Moisture preferences were also investigated and some form of ortho-kinesis may explain the results.

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Zusammenfassung Acht Oribatiden- und zwei Uropodiden-Arten wurden einem Feuchtigkeitsgefälle von völliger Sättigung bis zu 13% rel. Luftfeuchtigkeit ausgesetzt. Erwachsene Pelops acromios, Cepheus dentatus und Odontocephus elongatus zeigten sowohl bei 10° wie bei 20° in allen Feuchtigkeitsstufen nach drei Tagen eine 100% ige Überlebensrate. Ceratoppia bipilis, Oribata gracilipes und Euzetes seminulum wiesen bei niederer Luftfeuchtigkeit erhöhte Sterblichkeit auf und bei 13% rel. Luftfeuchtigkeit betrugen ihre Überlebensraten nach drei Tagen 75, 55 bzw. 45%. Hermannia gibba, Platynothrus peltifer, Olodiscus integra und Cilliba cassidea zeigten unter 55% rel. Luftfeuchtigkeit alle einen plötzlichen Abfall der Überlebensrate und am Ende von drei Tagen blieben nur wenige Individuen am Leben. Die Fähigkeit der larvalen und Nymphenstadien, erniedrigte Luftfeuchtigkeit zu ertragen, war im allgemeinen etwas geringer als bei den Adulten, doch zeigten die Arten untereinander die gleiche relative Resistenz wie bei den Erwachsenen. In einer alternativen Wahlkammer, die ein Feuchtigkeitsgefälle aufwies, bevorzugten alle Arten die feuchtere Hälfte. Nur wenn die Wahl zwischen 94% und 100% rel. Luftfeuchtigkeit geboten wurde, bevorzugten P. acromios, C. dentatus und O. elongatus die geringere Feuchte. Die Ergebnisse weisen darauf hin, daß eine Form von Orthokinese vorliegt und noch kein Unterschied in der Anzahl der Individuen beobachtet wurde, die sich bei gleichmäßiger Feuchtigkeit von 10, 47 und 100% rel. Luftfeuchtigkeit bewegten. Im Vergleich zwischen feuchten und trockenen Bedingungen besteht kein wahr nehmbarer Sensibilitätsunterschied.

     

Neurophysiological study on possible protective and therapeutic effects of Sidr (Zizyphus spina-christi L.) leaf extract in male albino rats treated with pentylenetetrazol

In this study, anti-convulsant effect of Sidr leaf extract was examined by using pentylenetetrazol (PTZ) model on male albino rat by evaluating the changes in norepinephrine (NE), dopamine (DA) and serotonin (5-HT) contents in different brain regions (cerebellum, brainstem, striatum, cerebral cortex, hypothalamus and hippocampus). The administration of subconvulsive dose of PTZ (40 mg/kg i.p.) every other day for 9 days caused a significant decrease in monoamine content in different brain areas, this is may be due to the increase in nitric oxide levels, although antagonized the GABAA receptors which led to neurotransmitter release so the content is decreased. Administration of PTZ after treatment with Sidr (50 mg/kg i.p.) leaf extract for 3 weeks as a protective group and administration of Sidr leaf extract for 3 weeks after treatment of PTZ as a therapeutic group caused significant increase in NE, DA, and 5-HT contents in all tested brain regions at most of the time intervals studied. This may be due to the presence of peptide and cyclopeptide alkaloids in the extract which inhibit neurotransmitter activity which led to the inhibition of neurotransmitter release. From these results, we can say that the Sidr leaf extract has neuroprotective and therapeutic roles against pentylenetetrazol convulsant effect.     

Effects of photobiomodulation on bone defects grafted with bone substitutes: A systematic review of in vivo animal studies

A present, photobiomodulation therapy (PBMT) effectiveness in enhancing bone regeneration in bone defects grafted with or without biomaterials is unclear. This systematic review (PROSPERO, ref. CRD 42019148959) aimed to critically appraise animal in vivo published data and present the efficacy of PBMT and its potential synergistic effects on grafted bone defects. MEDLINE, CCCT, Scopus, Science Direct, Google Scholar, EMBASE, EBSCO were searched, utilizing the following keywords: bone repair; low-level laser therapy; LLLT; light emitting diode; LEDs; photobiomodulation therapy; in vivo animal studies, bone substitutes, to identify studies between 1994 and 2019. After applying the eligibility criteria, 38 papers included where the results reported according to “PRISMA.” The results revealed insufficient and incomplete PBM parameters, however, the outcomes with or without biomaterials have positive effects on bone healing. In conclusion, in vivo animal studies with a standardized protocol to elucidate the effects of PBMT on biomaterials are required initially prior to clinical studies.     

The effect of immigration of infectives on disease-free equilibria

Journal of Mathematical Biology - Many disease transmission models exhibit a threshold behaviour based on the basic reproduction number $${\mathcal {R}}_0$$ , where the disease-free equilibrium is...