Modification of microstructure and selected physicochemical properties of bacterial cellulose produced by bacterial isolate using hydrocolloid-fortified Hestrin–Schramm medium

Bacterial cellulose (BC) is a biopolymer with applications in numerous industries such as food and pharmaceutical sectors. In this study, various hydrocolloids including modified starches (oxidized starch—1404 and hydroxypropyl starch—1440), locust bean gum, xanthan gum (XG), guar gum, and carboxymethyl cellulose were added to the Hestrin-Schramm medium to improve the production performance and microstructure of BC by Gluconacetobacter entanii isolated from coconut water. After 14-day fermentation, medium supplemented with 0.1% carboxymethyl cellulose and 0.1% XG resulted in the highest BC yield with dry BC content of 9.82 and 6.06 g/L, respectively. In addition, scanning electron microscopy showed that all modified films have the characteristic three-dimensional network of cellulose nanofibers with dense structure and low porosity as well as larger fiber size compared to control. X-ray diffraction indicated that BC fortified with carboxymethyl cellulose exhibited lower crystallinity while Fourier infrared spectroscopy showed characteristic peaks of both control and modified BC films.     

The suicide assessment scale: Psychometric properties of a Norwegian language version

ABSTRACT: BACKGROUND: Rating scales are valuable tools in suicide research and can also be useful supplements to the clinical interview in suicide risk assessments. This study describes the psychometric properties of a Norwegian language version of the Suicide Assessment Scale Self-report version (SUAS-S). METHODS: Participants were fifty-two patients (mean age = 39.3 years, SD = 10.7) with major depression (53.8%), bipolar disorder (25.0%) and/or a personality disorder (63.5%) referred to a psychiatric outpatient clinic. The SUAS-S, the screening section of the Beck Scale for Suicidal Ideation (BSS-5), the Beck Depression Inventory (BDI), Beck's Hopelessness Scale (BHS), the Symptom Check-List-90 R (SCL-90R) and the Clinical Global Impression for Severity of Suicidality (CGI-SS) were administered. One week later, the patients completed the SUAS-S a second time. RESULTS: Cronbach's alpha for SUAS-S was 0.88 and the test-retest reliability was 0.95 (95% CI: 0.93- 0.97). SUAS-S was positively correlated with the BSS-5 (r = 0.66; 95% CI: 0.47-0.85) for the study sample as a whole and for the suicidal (r = 0.52) and non-suicidal groups (r = 0.50) respectively. There was no difference between the SUAS-S and the BSS-5 in the ability to identify suicidality. This ability was more pronounced when the suicide risk was high. There was a substantial intercorrelation between the score on the SUAS-S and the BDI (0.81) and the BHS (0.76). The sensitivity and specificity of the SUAS-S was explored and an appropriate clinical cut-off value was assessed. CONCLUSIONS: The study revealed good internal consistency, test-retest reliability and concurrent validity for the Suicide Assessment Scale Self-report version. The discriminatory ability for suicidality was comparable to that of the BSS-5.     

Biochemical and phylogenetic characterization of isocitrate dehydrogenase from a hyperthermophilic archaeon, Archaeoglobus fulgidus

A thermostable homodimeric isocitrate dehydrogenase from the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus was purified and characterized. The mol. mass of the isocitrate dehydrogenase subunit was 42 kDa as determined by SDS-PAGE. Following separation by SDS-PAGE, A. fulgidus isocitrate dehydrogenase could be renatured and detected in situ by activity staining. The enzyme showed dual coenzyme specificity with a high preference for NADP⁺. Optimal temperature for activity was 90° C or above, and a half-life of 22 min was found for the enzyme when incubated at 90° C in a 50 mM Tricine-KOH buffer (pH 8.0). Based on the N-terminal amino acid sequence, the gene encoding the isocitrate dehydrogenase was cloned. DNA sequencing identified the icd gene as an open reading frame encoding a protein of 412 amino acids with a molecular mass corresponding to that determined for the purified enzyme. The deduced amino acid sequence closely resembled that of the isocitrate dehydrogenase from the archaeon Caldococcus noboribetus (59% identity) and bacterial isocitrate dehydrogenases, with 57% identity with isocitrate dehydrogenase from Escherichia coli. All the amino acid residues directly contacting substrate and coenzyme (except Ile-320) in E. coli isocitrate dehydrogenase are conserved in the enzyme from A. fulgidus. The primary structure of A. fulgidus isocitrate dehydrogenase confirmes the presence of Bacteria-type isocitrate dehydrogenases among Archaea. Multiple alignment of all the available amino acid sequences of di- and multimeric isocitrate dehydrogenases from the three domains of life shows that they can be divided into three distinct phylogenetic groups. Received: 6 February 1997 / Accepted: 12 June 1997     

Morphological changes in the male accessory glands and testes in Vespula vulgaris (Hymenoptera,Vespidae) during sexual maturation

Abstract. The present study documents the pace of accessory gland and testes degeneration in the wasp Vespula vulgaris by means of a histological and metric approach, that has not been carried out for social wasps so far. To a certain extent, comparison is made with the degenerative processes of the mucus glands of the honeybee drone. In V. vulgaris, no generative tissue is left by the end of 9 d of age, and so degeneration is a fast process. The three different parts of the accessory glands (muscle layer, gland epithelium, and lumen) change with respect to age. The secretory cells of the epithelium reach their maximum activity during the first days of adult life, which results in a maximally filled gland lumen by 9 d. We also provide, for the first time, a histological study of testes degeneration for this species. At eclosion, well‐defined cystic structures are still visible, whereas at 9 d, it is no longer possible to distinguish different cystic structures. The diameter of the testes decreases with respect to age.     

Induction and purification of a thermophilic chitinase produced byAeromonas sp. DYU-too7 using glucosamine

In the presence of chitin,Aeromonas sp. DYU-Too7 can produce extra-cellular, chitin-degrading enzymes. Chitin analogues and other carbon sources can be used to cultivate this bacterial strain. The chitinases produced by the strain were higher in the GIcN (glucosamine) medium than those in other media. The maximal chitinase activity occurred in the medium containing 0.1% GIcN. Cultivation ofAeromonas sp. DYU-Too7 in the GIcN medium sped up the chitinase production; however the same result did not appear when it was cultivated in the (Chitin+GIcN) medium. This result may indicate that GIcN can be utilized byAeromonas sp. DYU-Too7 as a carbon source and an inducer to produce chitinases. A chitinase with a molecular mass of 36 kDa was further purified and characterized to have an optimal reacting pH of 5.0 and an optimal reacting temperature of 50°C. This chitinase showed high stability in the proximity of 30°C and also high stability in the proximity of pH 7.0. The hydrolysates of colloidal chitin, with the aid of the 36-kDa chitinase, were analyzed by an HPLC and found to be chitobiose.     

Effect of uncouplers on anaerobic adaptation of hydrogenase activity in C., reinhardtii

An anaerobic incubation period of varying duration is required to induce hydrogenase activity in $\text{C.}\text{,}\text{reinhardtii}$. Inclusion of sodium acetate, a metabolizable carbonaceous substrate, in the medium during anaerobic incubation accelerates the activation process. Thus, in the presence of sodium acetate, hydrogen photoproduction is detected within 7 to 15 minutes after the onset of anaerobiosis. On the contrary, if an uncoupler of phosphorylation, such as CCCP or sodium arsenate, is present during anaerobic incubation, little activation of the hydrogenase is observed even after hours of anaerobic adaptation. Since the uncouplers had no inhibitory effect on hydrogen photoproduction by the alga when added to previously activated cells, they are not inhibitors of activated hydrogenase. The uncouplers interfere, most likely, with the activation of hydrogenase. Similar effects of uncouplers on the hydrogenase activation process were obtained using a cell-free assay of hydrogenase activity. These observations provide strong evidence that anaerobic activation of the hydrogenase is an energy requiring process.     

Ectoparasite‐induced increase in Drosophila host metabolic rate

Parasites exert numerous effects upon their hosts, including physiological and metabolic changes that can in turn influence various aspects of host life history. Using flow‐through respirometry, we investigated how infection intensity of an ectoparasitic mite (Macrocheles subbadius) affects the respiratory rate (CO₂ production) of its host Drosophila nigrospiracula. Mean fly respiratory rate increased with infection intensity with the strongest effect, a 40% increase relative to uninfected controls, occurring with three mites attached. We also verified the causal relationship between elevated respiration rate and mite attachment by examining changes in host respiration before and after mite exposure. We found that the rate of CO₂ production increased by 11% for individual flies following parasite attachment. Fly locomotor activity was not significantly different between infected and uninfected individuals. Metabolic rate of hosts increased as a result of infection in an intensity dependent manner and was not simply due to changes in host activity. These results demonstrate that parasites can have a significant influence on the energy requirements of their host, which may account for the parasite‐mediated loss in host fitness.