Biochemical characterization and structural insights into the high substrate affinity of a dimeric and Ca2+ independent Bacillus subtilis α-amylase

An extracellular amylase (AmyKS) produced by a newly isolated Bacillus subtilis strain US572 was purified and characterized. AmyKS showed maximal activity at pH 6 and 60°C with a half-life of 10 min at 70°C. It is a Ca²⁺ independent enzyme and able to hydrolyze soluble starch into oligosaccharides consisting mainly of maltose and maltotriose. When compared to the studied α-amylases, AmyKS presents a high affinity toward soluble starch with a K_m value of 0.252 mg ml⁻¹. Coupled with the size-exclusion chromatography data, MALDI–TOF/MS analysis indicated that the purified amylase is a dimer with a molecular mass of 136,938.18 Da. It is an unusual feature of a non-maltogenic α-amylase. A 3D model and a dimeric model of AmyKS were generated showing the presence of an additional domain suspected to be involved in the dimerization process. This dimer arrangement could explain the high substrate affinity and catalytic efficiency of this enzyme.     

Some structural features of sargassan,a sulphated heteropolysaccharide from Sargassum linifolium

The acid-extractable, water-soluble, sulphated heteropolysaccharide, sargassan, contains residues of D-glucuronic acid, D-mannose, D-galactose, D-xylose, and L-fucose, and a protein moiety. Partial, acid hydrolysis of sargassan and auto-hydrolysis of the free-acid polysaccharide have been studied. Several acidic and neutral oligosaccharides were subsequently isolated. Evidence is advanced for the presence of ester sulphate on some galactose and fucose residues. It is concluded that the carbohydrate moiety of sargassan involves a backbone chain of D-glucuronic acid and D-mannose residues, and side chains involving residues of D-galactose, D-xylose, and L-fucose with sulphate attached to some galactose and fucose residues.     

Effect of saliva from sheep that have ingested quebracho tannins on the in vitro rumen fermentation activity to digest tannin-containing shrubs

This work was designed to assess the nutritional influence of pre-incubation in saliva on in vitro fermentative activity when some tanniniferous shrubs were incubated in batch cultures of mixed ruminal microorganisms. Saliva was collected from eight Merino sheep allocated in two experimental groups, namely control (SC) and quebracho (SQ) groups fed one kg alfalfa hay daily. Sheep of SQ group were given daily alfalfa hay supplemented with 50 g quebracho/kg dry matter for 60 days, whereas sheep of SC group were always given unsupplemented alfalfa hay. Foliage of six shrub species (Cytisus scoparius (Scotch broom), Genista florida (Iberian silver-leaved broom), Rosa canina (wild dog rose), Quercus pyrenaica (hoary oak), Cistus laurifolius (laurel-leaved rock-rose) and Erica australis (Spanish heath)) was collected from uplands in the province of León (Norwest Spain) in spring and in summer/autumn and used in the study. Samples were pre-incubated in each saliva source for 4 h at 39 °C, followed by an incubation in buffered rumen fluid to determine their in vitro dry matter digestibility (IVD) and gas production kinetics. For all treatments, rumen fluid was obtained from sheep of control group. Regardless the large differences among the plant browse species used in the study in their tannin contents, IVD and rate and extent of degradation (based on gas production parameters), there were no significant differences between SC and SQ saliva in any of the variables studied. Accordingly, it was suggested that sheep supplemented with quebracho tannins did not produce salivary proteins to protect against negative effects of tannins on digestion of plant material, and that the feedback mechanism may not have evolved or may have become lost. Further studies on the effect of tannins on saliva chemical composition in sheep would be timely.     

Balancing selected medication costs with total number of daily injections: a preference analysis of GnRH-agonist and antagonist protocols by IVF patients

ABSTRACT: BACKGROUND: During in vitro fertilization (IVF), fertility patients are expected to self-administer many injections as part of this treatment. While newer medications have been developed to substantially reduce the number of these injections, such agents are typically much more expensive. Considering these differences in both cost and number of injections, this study compared patient preferences between GnRH-agonist and GnRH-antagonist based protocols in IVF. METHODS: Data were collected by voluntary, anonymous questionnaire at first consultation appointment. Patient opinion concerning total number of s.c. injections as a function of non-reimbursed patient cost associated with GnRH-agonist [A] and GnRH-antagonist [B] protocols in IVF was studied. RESULTS: Completed questionnaires (n = 71) revealed a mean +/[MINUS SIGN] SD patient age of 34 +/[MINUS SIGN] 4.1 yrs. Most (83.1 %) had no prior IVF experience; 2.8 % reported another medical condition requiring self-administration of subcutaneous medication(s). When out-of-pocket cost for [A] and [B] were identical, preference for [B] was registered by 50.7 % patients. The tendency to favor protocol [B] was weaker among patients with a health occupation. Estimated patient costs for [A] and [B] were $259.82 +/[MINUS SIGN] 11.75 and $654.55 +/[MINUS SIGN] 106.34, respectively (p < 0.005). Measured patient preference for [B] diminished as the cost difference increased. CONCLUSIONS: This investigation found consistently higher non-reimbursed direct medication costs for GnRH-antagonist IVF vs. GnRH-agonist IVF protocols. A conditional preference to minimize downregulation (using GnRH-antagonist) was noted among some, but not all, IVF patient sub-groups. Compared to IVF patients with a health occupation, the preference for GnRH-antagonist was weaker than for other patients. While reducing total number of injections by using GnRH-antagonist is a desirable goal, it appears this advantage is not perceived equally by all IVF patients and its utility is likely discounted heavily by patients when nonreimbursed medication costs reach a critical level.     

Salivary exosomes as a new therapy to ameliorate diabetes mellitus and combat xerostomia and submandibular salivary glands dysfunction in diabetic rats

Journal of Molecular Histology - Diabetes mellitus (DM) is one of the major metabolic diseases. Xerostomia and salivary gland dysfunction are of its common oral complications. Exosomes, as a new...