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Biomedical subjects

D E Hansen

Publications and source records attributed to D E Hansen.

49 records · Page 3Linked to original sources
PubMed1986

Factors affecting prerace dehydration and performance of racing greyhounds.

Several factors, including age, sex, race number, post position, and race class, were evaluated for relationships to prerace percentage body weight loss and performance in all Greyhounds racing during August 1983 in Oregon. The incidence of percentage body weight loss greater than or equal to 2.5% was low (5%). Race number had a direct effect on weight loss; the later the dogs raced, the more weight loss they experienced. Female dogs were 3 times more likely to lose greater than 2.4% of body weight than males. All dogs experiencing greater than 2.4% body weight loss were 2 times more likely to finish in the first 3 places when racing in the first 5 races overall. In addition, males losing greater than 2.4% of body weight performed better than females when racing together in the final 6 races. Males appeared to be better performers than females, as they were twice as likely to be in class A races. However, once in the race, males and females performed equally.

Age Factors↗
PubMed1986

Effects of acute lung injury and anesthesia on left ventricular mechanics.

Traditional left ventricular (LV) function curves are frequently depressed in patients with acute lung injury. Similar findings in pentobarbital sodium-anesthetized dogs with oleic acid lung injury (OALI) have been observed. To test the hypothesis that acute OALI produces a significant injury to the heart, the LV mechanics of pentobarbital-anesthetized dogs with (n = 6) and without (n = 6) OALI were evaluated. End-systolic force-length and force-velocity relations determined echocardiographically during afterload manipulation with sodium nitroprusside demonstrated a marked deterioration in LV shortening characteristics over 90 min in both groups of pentobarbital-anesthetized dogs. In contrast, LV mechanics studied using the same protocol in fentanyl-anesthetized dogs were unchanged in both the injured (n = 6) and noninjured (n = 6) lung groups. Comparisons with data acquired over a wide range of LV afterload from six conscious, instrumented dogs showed that LV contractile state was normal to slightly increased with fentanyl and markedly depressed with pentobarbital. Diastolic properties, as assessed by end-diastolic pressure-dimension relations, were essentially unchanged in all anesthetized animals. We conclude that OALI has no effect on LV systolic or diastolic mechanics; the LV dysfunction attributed to OALI in previous studies is due to an acute, severe cardiomyopathy induced by pentobarbital; and unlike pentobarbital, anesthesia with fentanyl has no discernible time-dependent effect on LV mechanics. These findings have important implications for future studies of canine cardiovascular physiology employing anesthetized animal preparations.

Anesthesia↗
PubMed1986

Valvular-ventricular interaction: importance of the mitral apparatus in canine left ventricular systolic performance.

As the mitral valvular apparatus tenses during systole, forces transmitted along the chordae tendineae to the left ventricular chamber may influence left ventricular performance. To test this hypothesis, 10 dogs anesthetized with fentanyl were studied during cardiopulmonary bypass. The importance of the mitral apparatus in left ventricular systolic function was assessed independent of load by means of the slope of the contractile state-dependent left ventricular peak isovolumetric pressure-volume relationship (Emax), which was measured at constant heart rate and aortic pressure with a micromanometer inside a left ventricular intracavitary balloon before and immediately after all chordae tendineae were severed. Herniation of the balloon was prevented by a disk secured to the mitral anulus. Emax decreased from 11.97 +/- 3.35 (+/- SD) to 6.38 +/- 0.96 mm Hg/ml (p less than .001) with chordal severing. The volume intercept (Vo) was unchanged. Fluoroscopic studies of the balloon contour in eight additional dogs revealed dyskinesia in the area of the papillary muscle insertion and substantial alterations in chamber geometry during systole after the chordae were severed. Accordingly, we conclude that global left ventricular systolic performance is impaired when chordal attachments of the mitral valve are disrupted. Changes in left ventricular geometry or loss of inward force normally transmitted to the left ventricular wall as the valve tense may underlie these changes. These findings suggest that postoperative left ventricular dysfunction after mitral valve replacement may be attributable, in part, to excision of the native mitral apparatus at the time of surgery and support efforts to spare chordae during mitral valve surgery.

Animals↗
PubMed1985

Factors associated with the spread of clinical vesicular stomatitis in California dairy cattle.

In 1983, vesicular stomatitis entered the state of California through infected cattle purchased in Idaho and sold to 5 California dairies. This study examined management, environmental, and host factors which were thought to be associated with disease spread. The use of coarse roughage and hard-pelleted concentrates, the presence of uneaten feed potentially contaminated with virus-laden saliva, increased interpen movement of cows, poor ground surface conditions, poor milking hygiene, and poor teat sanitation were management factors observed to be associated with clinical signs. The amount of milk production, age, or days in milk of individual cows seemed to have an important role in the spread of clinical disease. Recommendations are given for control and prevention of clinical signs and, therefore, the severity of disease during epizootics of vesicular stomatitis in California dairies.

Animals↗
PubMed1982

The stereochemical course at phosphorus of the reaction catalyzed by phosphoenolpyruvate carboxylase.

[(S)-16O,17O]Thiophosphoenolpyruvate has been used as a substrate in H218O for the reaction catalyzed by phosphoenolpyruvate carboxylase, and the absolute configuration of the product, inorganic [16O,17O,18O]thiophosphate, has been determined. The reaction proceeds with inversion of configuration at phosphorus, thus ruling out the cyclic mechanism that has been proposed for this enzyme. The stereochemical result is consistent with a stepwise mechanism involving the intermediate formation of carboxyphosphate.

Carboxy-Lyases↗
PubMed1982

Stereochemical course of the reactions catalyzed by the bacterial phosphoenolpyruvate:glucose phosphotransferase system.

The overall stereochemical course of the reactions leading to the phosphorylation of methyl alpha-D-glucopyranoside by the glucose-specific enzyme II (enzyme IIGlc) of the Escherichia coli phosphotransferase system has been investigated. With [(R)-16O,17O,18O]phosphoenolpyruvate as the phosphoryl donor and in the presence of enzyme I, HPr, and enzyme IIIGlc of the phosphotransferase system, membranes from E. coli containing enzyme IIGlc catalyzed the formation of methyl alpha-D-glucopyranoside 6-phosphate with overall inversion of the configuration at phosphorus (with respect to phosphoenolpyruvate). It has previously been shown that sequential covalent transfer of the phosphoryl group of phosphoenolpyruvate to enzyme I, to HPr, and to enzyme IIIGlc occurs before the final transfer from phospho-enzyme IIIGlc to the sugar, catalyzed by enzyme IIGlc. Because overall inversion of the configuration of the chiral phospho group of phosphoenolpyruvate implies an odd number of transfer steps, the phospho group has been transferred at least five times, and transfer from phospho-enzyme IIIGlc to the sugar must occur in two steps (or a multiple thereof). On the basis that no membrane protein other than enzyme IIGlc is directly involved in the final phospho transfer steps, our results imply that a covalent phospho-enzyme IIGlc is an intermediate during transport and phosphorylation of glucose by the E. coli phosphotransferase system.

Biological Transport↗
PubMed1981

The stereochemical course of the reaction catalyzed by creatine kinase.

Adenosine [gamma-(S)-16O, 17O, 18O]triphosphate has been used as a substrate in the reaction catalyzed by creatine kinase, and the configuration at phosphorus in the product [16O, 17O, 18O]phosphocreatine has been determined. The reaction proceeds with inversion of the configuration, consistent with the emerging pattern of behavior among the phosphokinases. This result, coupled with recently published data from NMR, ESR, and infrared studies of ternary and quaternary complexes od creatine kinase with its substrates and inhibitors, defines the enzyme-catalyzed transphosphorylation as an associative in-line transfer of the phosphoryl group between the bound substrates.

Adenosine Triphosphate↗
PubMedDate not supplied

Initial experience with a universal-length copolymer ureteral stent.

A universal-length ureteral stent made of a biocompatible copolymer was designed specifically for easy antegrade internal placement. The double-looped distal end of the stent eliminates the need to measure the distance from the ureteropelvic to ureterovesical junction. If additional length is required, a portion of the distal loop is incorporated into the stent shaft. Interventional radiology practices benefit economically, as the universal-length stent is the only size required for the treatment of most ureteral obstructions.

Adolescent↗
PubMedDate not supplied

An approach to sequence-specific antibody proteases. The use of haptens mimicking both a transition state and a distorted ground state.

We describe here a novel strategy for the isolation of antibodies with sequence-specific protease activity: the synthesis of dipeptide haptens in which the targeted peptide bond has been replaced by a ring-strained or torsionally strained hydroxyethylene transition-state analog. Thus, the analogs mimic both a peptide bond in a distorted, reactive conformation and the transition state for peptide bond hydrolysis. In order to obtain sequence-specific antibody proteases, these analogs have been flanked with additional amino acid residues in preparation for immunization. In particular, we have synthesized peptides containing analogs such as 2-cis-amino-3-cis-hydroxycyclobutane carboxylic acid and endo-(3-amino-2-hydroxy)bicyclo[2.2.1]-heptane-7-anti-carboxylic acid. We have also prepared a series of peptide derivatives containing analogs, such as 2-[3-amino-2-oxo-1-azetidinyl]-3-methylbutanoic acid, in which the targeted peptide bond has been incorporated into a beta-lactam ring. Since the "peptide bond" has been left intact, these species mimic only a distorted ground state. At present, antibodies are being elicited against a number of the above peptide derivatives.

Antibodies, Catalytic↗
PubMedDate not supplied

Autoimmune hemolytic anemia with predominance of IgA autoantibody.

A 71-year-old woman with severe autoimmune hemolytic anemia had negative direct antiglobulin tests using commercial broad spectrum antisera. Her unwashed cells agglutinated spontaneously in the potentiating medium polyvinylpyrrolidone (PVP) solution or in hexadimethrine bromide (Polybrene) solution. A strongly positive direct antiglobulin test was obtained with specific antihuman IgA sea with or without PVP. In PVP solution, small amounts of IgG, IgM, and complement components were also detected on her cells. The findings illustrate the ability of anti-human IgA to detect autoimmune red blood cell sensitization when other immunoglobulin classes of autoantibody are below detectable levels or absent. Also illustrated is the value of PVP and Polybrene in detecting agglutination in the evaluation of "antiglobulin negative" hemolytic anemia.

Aged↗