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Biomedical subjects

D J Huber

Publications and source records attributed to D J Huber.

22 records · Page 2Linked to original sources
PubMed1977

Preparation and Properties of a beta-d-Glucanase for the Specific Hydrolysis of beta-d-Glucans.

A beta-d-glucanase highly specific for glucans containing a linkage sequence ... Glc 1 --> 4 Glc 1 --> 3 Glc 1 --> 4 Glc ... has been isolated from several commercial preparations of Bacillus subtilis alpha-amylase including one purified by repeated crystallization. The beta-d-glucanase will not hydrolyze cellulose or laminarin. Gel filtration on a Bio-Gel P-200 column results in separation of the glucanase from the alpha-amylase. The enzyme is of the endo type as changes in the substrate viscosity appear long before the appearance of detectable reducing sugars. No evidence of product inhibition was revealed and appropriate substrates were converted to oligosaccharides, the quantity of which approaches theoretical yields. The products of the reaction were separated according to molecular size by use of Bio-Gel P-2 gel filtration and found to be consistent with the action pattern of the enzyme. Kinetic studies show that the enzyme has an optimum activity at pH 6.5, a V(max) of 13.9 mug glucose equivalent released/mug protein.hour, and an apparent Km of 3.4 mg of lichenan per ml. Potential application of this enzyme for the structural characterization of plant cell wall glucans is discussed.

Journal Article↗
PubMed1977

beta-d-Glucan of Avena Coleoptile Cell Walls.

A specific glucanase was used to liberate a noncellulosic beta-d-glucan from isolated cell walls of Avena sativa coleoptile tissue. Cell walls of this tissue contain as much as 7 to 9 mg of glucan/100 mg of dry wall. Because of the specific action pattern of the enzyme, a linkage sequence of.. 1 --> 4 Glc 1 --> 3 Glc 1 --> 4 Glc.. is indicated and the predominance of trisaccharide and tetrasaccharide as hydrolytic products suggests a rather regular repeating pattern in the polysaccharide. The trisaccharide and the tetrasaccharide are tentatively identified as 3-O-beta-cellobiosyl-d-glucose and 3-O-beta-cellotriosyl-d-glucose, respectively. Recovery of these oligosaccharides following glucanase treatment of native wall material was feasible only after wall-bound glucosidases were inactivated. In the absence of enzyme inactivation the released fragments were recovered as glucose. The beta-d-glucan was not extracted from walls by either hot water or protease treatment.Cell walls prepared from auxin-treated Avena coleoptile segments yielded less glucan than did segments incubated in buffer suggesting an auxin effect on the quantity of this wall component. No IAA-induced change in the ratio of the trisaccharide and tetrasaccharide could be detected, suggesting no shift in the 1,3 to 1,4 linkage ratio. While the enzyme acts directly on the beta-d-glucan, no elongation response was apparent when Avena sections were treated with the purified glucanase. The presence of the glucan was not associated with any wound response which could be attributed to the preparation of coleoptile segments. The relationship of glucan metabolism to auxin growth responses is discussed.

Journal Article↗
PubMedDate not supplied

The effect of knotting method on the structural properties of large diameter nonabsorbable monofilament sutures.

OBJECTIVE: To evaluate the effect of knotting method on the mechanical properties of large diameter nonabsorbable monofilament suture materials. STUDY DESIGN: In vitro mechanical evaluation. METHODS: A conventional square knot was compared with the surgeon's knot, sliding half-hitch, and clamped square knot. Knotted suture loops were created in a uniform manner and acutely tensioned to failure (20 mm/min loading rate; n = 20 per knot type for each material). Stiffness, yield, and failure characteristics of USP #2 nylon, #2 polybutester, #2 polypropylene, 27 kg test monofilament nylon fishing line, and 27 kg nylon leader material were evaluated. RESULTS: Compared with a conventional square knot, a surgeon's knot decreased stiffness for #2 polypropylene, 27 kg fishing line, and 27 kg leader (P < .05). A sliding half-hitch weakened all materials except 27 kg leader (P < .05). Clamping the first throw of a square knot increased the stiffness of 27 kg leader loops (P < .05). CONCLUSIONS: Based on clinically relevant parameters (stiffness and yield), knotting method had no effect on #2 nylon and #2 polybutester. The surgeon's knot is not recommended for #2 polypropylene and 27 kg fishing line and leader material. A sliding half-hitch decreased the yield of leader material. Clamping the first throw of a square knot had no adverse effects on acute properties of tested materials; it increased the stiffness for leader material. CLINICAL RELEVANCE: Knotting method does influence the structural properties of suture materials and should be considered when tying knots under tension.

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