Biomedical subjects
Publications and source records attributed to M J Boland.
Aqueous phase separations offer a novel and different means of extracting and purifying proteins from animal tissue at industrial scale. This article gives an overview of aqueous phase separations in relation to animal tissue, describes some pilot-scale work, and discusses the strengths, weaknesses and future prospects for this technology.
Genetic selection of cattle by selective breeding patterns dates back to prehistoric times and has resulted in the diversity of breeds we see today. Selection in New Zealand has been for fat production earlier in the century, and more recently for protein production as well as fat. There is a lot of interest today in the naturally occurring variants of the milk proteins, as these can confer interesting differences in the molecular behaviour of the proteins as well as being correlated with compositional differences in the milk. Genetic modification holds great promise for the future in the dairy industry, but present constraints due to cost, lack of basic knowledge, and difficulty in producing genetically-modified calves, mean that only the biopharmaceutical area is likely to be affected in the near future. Coupled to this is an apparent lack of acceptance of food from genetically-modified animals by consumers. It will therefore need a change in public attitude as well as some development in science and technology before dairy products from genetically modified cattle become a commercial reality.
Pilot scale trials have been carried out to assess the feasibility of using PEG-salt aqueous phase systems for extraction and purification of enzymes from animal tissue on an industrial scale. Comminuted bovine liver was used as a starting material, and it was easy to separate a clear upper phase containing proteins of interest from a mixture containing 20% biomass, 15% PEG and 8% phosphate using a disc separator. Similar attempts with decanters were unsuccessful. Second-phase separation was simply accomplished by the addition of salt to the separated, clear upper layer and standing or allowing passage through a disc separator. The method was tested using continuous mixing on the GBF continuous mixing aqueous phase extraction plant, with and without computer control. Good separations were achieved. The enzyme superoxide dismutase was purified using this method yielding a 4-fold purification factor with respect to soluble protein and a recovery rate of 83%, with the enzyme in a clarified solution suitable for further processing by chromatographic methods. The general applicability of this method, its economics and its potential application in industry are discussed.
Benazepril HCl is an orally effective angiotensin converting enzyme (ACE) inhibitor previously shown to have significant acute hemodynamic benefits in patients with congestive heart failure. In this study, 21 patients with New York Heart Association Class III or IV congestive heart failure were treated with 2 to 15 mg of benazepril HCl as a single daily oral dose for 28 days to determine the clinical and hemodynamic value of chronic therapy. Each patient underwent clinical evaluation during the 28-day period, as well as invasive hemodynamic studies on the first two and last two days of the trial. Plasma ACE activity and aldosterone levels fell significantly and renin levels rose after therapy. Benazepril HCl produced significant (p less than 0.01) reductions in arterial pressure and systemic vascular resistance, with corresponding increases in cardiac output and decreases in pulmonary artery wedge pressure. Responses after 28 days of therapy were equivalent to those after the initial doses. Clinical effects included reduced rest, exertional and paroxysmal nocturnal dyspnea, as well as reduced peripheral edema. Only one patient developed symptomatic orthostatic hypotension. Thus, benazepril HCl, given once daily, is an effective and well tolerated oral agent for the chronic treatment of advanced congestive heart failure.
Animal tissue is likely to continue to be an important source of enzymes and protein hormones well into the 21st century. Aqueous phase systems show considerable potential and specific advantages for extractive purification of proteins from animal tissue. Although no industrial process is yet in place for commercial production of a protein from animal tissue, the potential for the system has, however, been demonstrated at laboratory scale for a number of enzymes, and at pilot scale for a few, using simple phase systems and also affinity partitioning systems. Pertinent features of these systems are reviewed, and process and economic aspects discussed.
Benazepril hydrochloride is a nonsulfhydryl, long-acting angiotensin-converting enzyme inhibitor that is orally effective. This study was designed to determine the acute hemodynamic effects of this agent in patients with chronic congestive heart failure. Twenty-six patients with New York Heart Association class III or IV congestive heart failure and left ventricular ejection fractions less than 35%, cardiac indexes less than 2.1 L/min/m2, and pulmonary artery wedge pressures greater than 12 mm Hg were given 2 or 5 mg benazepril hydrochloride. All does produced significant (p less than 0.05) increases in cardiac output (26.7% to 31.6% above control) and heart rate (5.4% to 11.2% above control) and decreases in systemic (27.1% to 32.0% below control) and pulmonary (34.8% to 55.5% below control) vascular resistances, mean pulmonary (25.3% to 30.3% below control) and systemic (13.4% to 18.5% below control) arterial pressures, and pulmonary artery wedge pressure (46.9% to 51.1% below control). Twenty-four hours after an initial dose, systemic vascular resistance and pulmonary artery wedge pressures remained below control levels. Angiotensin-converting enzyme activity fell by 67.8% +/- 6.4%, with a 15.8% +/- 7.6% decline in aldosterone levels. Thus benazepril hydrochloride is an effective angiotensin-converting enzyme inhibitor that produces hemodynamic effects that persist for 24 hours after a single oral dose.
Given the utility of a multifactoral approach to cardiac rehabilitation and the importance of tailoring such an approach to the needs of the specific cardiac population being treated, early assessment of targeted risk factors and health-related practices is becoming increasingly indicated. The present article describes how, by using a paper-and-pencil multiple-risk-factor assessment instrument referred to as the Heart Health Assessment Questionnaire, the specific educational needs of an aging veteran population were more clearly identified. Among the health areas found in need of particular attention were patient smoking behavior, medication education, and reported tension and worry over health problems. In addition, given the large unemployment rate within this population, the need for the adoption of activities such as physical exercise and hobbies that could have a positive impact on self-esteem and quality of life was strongly indicated. These and other findings are discussed in relation to the pivotal role of the health education professional for older cardiac populations.
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A procedure for the purification of Mg2+ adenosine triphosphatase (EC 3.6.1.3) from free-living and bacteroid forms of Rhizobium lupini NZP2257 is described. The enzyme was released from cell envelopes using Triton X-100 and purified by gel filtration on Ultrogel AcA 22, followed by preparative gel electrophoresis on agarose. The purified ATPase had a molecular weight of about 355,000, as determined from sedimentation coefficients on sucrose gradients. Kinetic analysis of activity of the enzyme from free-living R. lupini showed it to be typical of F1-type Mg2+ ATPases from bacteria. Mg stimulated activity at pH 7.0, although, when present as the free ion, Mg caused non-competitive inhibition (K1 = 1.5 mM). Maximum activity with ATP occurred over a broad pH range from 6.0 to 10.5. ATP, GTP, and UTP, and, to a much lesser degree, CTP and ADP, were hydrolyzed by the enzyme. Hydrolysis of glucose 6-phosphate was not observed. The Km for ATP at pH 7.0 was 0.67 and for GTP 1.4 mM. ATPase activity was inhibited by ADP, and competitive with ATP (KI = 0.18 mM). Azide also caused inhibition but fluoride and DCCD had no effect. Native and sodium dodecyl sulfate-gel electrophoretic analysis revealed no obvious differences between ATPases from free-living and bacteroid forms of R. lupini.
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A 45-fold purification of uricase (urate:O2 oxidoreductase, EC 1.7.3.3) from soybean root nodules by ammonium sulfate fractionation, gel filtration, and affinity chromatography is described. Electrophoresis on nondenaturing gels using an activity stain or on sodium dodecyl sulfate (SDS) gels demonstrated that the enzyme obtained was nearly homogeneous. The subunit molecular weight of uricase estimated from SDS gels was 32,000 +/- 3000. Gel-filtration studies indicated that the native enzyme is a monomer at pH 7.5 which associates to form a dimer at pH 8.8. Enzyme activity was stabilized by the addition of dithiothreitol. The pH dependence of the enzyme showed an optimum of 9.5. Initial rate kinetics showed Km values of 10 and 31 microM for uric acid and oxygen, respectively, with an intersecting pattern of substrate dependence. Uricase activity was inhibited strongly by xanthine, which was competitive with respect to uric acid (Ki = 10 microM). No significant inhibition was observed in the presence of a variety of amino acids, ammonium, adenine, or allopurinol, in contrast with results reported for the cowpea enzyme. Gel-filtration chromatography and SDS-gel electrophoresis of uricase purified by the same method from cowpea nodules indicated that the native enzyme exists as a monomer of Mr 50,000 at pH 7.5.
Xanthine dehydrogenase was purified from soybean nodules and the kinetic properties were studied at pH 7.5. Km values of 5.0 +/- 0.6 and 12.5 +/- 2.5 microM were obtained for xanthine and NAD+, respectively. The pattern of substrate dependence suggested a Ping-Pong mechanism. Reaction with hypoxanthine gave Km's of 52 +/- 3 and 20 +/- 2.5 microM for hypoxanthine and NAD+, respectively. The Vmax for this reaction was twice that for the xanthine-dependent reaction. The pH dependence of Vmax gave a pKa of 7.6 +/- 0.1 for either xanthine or hypoxanthine oxidation. In addition the Km for xanthine had a pKa of 7.5 consistent with the protonated form of xanthine being the true substrate. Km for hypoxanthine varied only 2.5-fold between pH 6 and 10.7. Product inhibition studies were carried out with urate and NADH. Both products gave mixed inhibition with respect to both substrates. Xanthine dehydrogenase was able to use APAD+ as an electron acceptor for xanthine oxidation, with a Km at pH 7.5 of 21.2 +/- 2.5 microM and Vmax the same as that obtained with NAD+. Reduction of APAD+ by NADH was also catalyzed by xanthine dehydrogenase with a Km of 102 +/- 15 microM; Vmax was approximately 2.5 times that for the xanthine-dependent reaction, and was independent of pH between 6 and 9. Reaction with group-specific reagents indicated the possibility of an essential histidyl group. A thiol-modifying reagent did not cause inactivation of the enzyme. A role for the histidyl side chain in catalysis is proposed.
A proplastid-containing fraction was rapidly prepared from soybean nodules by a combination of differential and step gradient centrifugation. This fraction was capable of incorporating [U-14C]glycine into purines in the presence of added phosphoribosylpyrophosphate or ribose 5-phosphate, glutamine, aspartate, ATP, bicarbonate, methenyl tetrahydrofolate, MgCl2, and KCl. The primary product was IMP; some inosine was also formed. Soluble and bacteroid fractions from soybean nodules gave considerably lower rates of incorporation. Labeled carbon from both [U-14C]serine and [3-14C]serine was incorporated into purines when tetrahydrofolate and NADP+ were substituted for methenyl tetrahydrofolate. In this case, small amounts of label were also found in AMP and xanthine monophosphate (XMP). Labeled bicarbonate was incorporated into IMP and inosine by the proplastid fraction. Labeled formate, however, was not a competent substrate for purine synthesis, indicating the absence of formyl tetrahydrofolate synthetase activity in this fraction. When labeled IMP was incubated with a proplastid preparation, most of the label appeared in inosine. XMP and xanthosine were also formed if NAD+ or NADP+ was added to the incubation mixture indicating the presence of IMP dehydrogenase activity in the proplastid fraction.
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The binding of substrate analogues including potential alternative substrates, to glutamate synthase (NADH) (L-glutamate: NAD+ oxidoreductase (transaminating) E.C. 1.4.1.14) has been investigated by studying competitive inhibition with respect ot 2-oxoglutarate. Binding requires two terminal carboxyl groups on a C5 straight chain molecule although some C4 molecules bind weakly. Bulky substituents at C2 decrease or prevent binding. Glutarate, the most potent inhibitor, binds much less tightly than the substrate. A 2-oxo group in a molecule other than the substrate does not appear to contribute significantly to binding. None of the analogues was able to act as an alternative substrate.
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