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Biomedical subjects

D R Nelson

Publications and source records attributed to D R Nelson.

At least 199 records · Page 11Linked to original sources
PubMed1986

Plasma cortisol and norepinephrine concentrations in castrated male pigs maintained in pairs in outdoor pens and in a confinement finishing house: assessment of stress.

A catheter-backpack system was developed for repeated blood collection in pigs. Castrated male pigs (n = 12) were maintained in pairs in outdoor pens and later in a slotted-floor confinement finishing house. Blood collection required no restraint and appeared to be stress free. Serum cortisol concentration was unchanged by mode of maintenance. However, diurnal variation of cortisol was more pronounced when pigs were housed. A significant decrease (P less than 0.05) in serum norepinephrine concentration occurred during the housing period.

Animals↗
PubMed1985

Phospholipid and detergent effects on (Ca2+ + Mg2+)ATPase purified from human erythrocytes.

(Ca2+ + Mg2+)ATPase (EC 3.6.1.3) was solubilized from human erythrocyte membranes by detergent extraction with Triton N-101 (0.5 mg/mg membrane protein) and purified by calmodulin affinity chromatography. ATPase activity was assayed in mixtures of Triton N-101 and phospholipid, without reconstitution into bilayer vesicles. At low levels of phospholipid (5 micrograms/ml), the ATPase activity was highly sensitive to the detergent concentration, with maximal activity occurring at or near the critical micelle concentration of the detergent. With increased amounts of phospholipid (50 micrograms/ml), detergent concentrations greater than the critical micelle concentration were required for maximal activity. Detergent alone did not support ATPase activity. Sonicated phospholipid in the form of vesicles was equally ineffective. Activity seemed to be dependent on the presence of detergent/phospholipid mixed micelles. The acidic phospholipids, phosphatidylserine and phosphatidylinositol, as well as the commercial phospholipid preparation, Asolectin, gave activities five to eight times greater than the same amount of phosphatidylcholine. Mixtures of phosphatidylserine and phosphatidylcholine produced intermediate ATPase activities, with the maximal value dependent on the phosphatidylserine concentration. Addition of phosphatidylcholine to fixed concentrations of phosphatidylserine caused a rise in activity that was independent of the ratio of the two phospholipids or the total phospholipid concentration. Phosphatidylcholine may therefore be irreplaceable for some aspect of ATPase function. The number of phospholipid molecules present in mixed micelles at maximal ATPase activity was calculated to be near 50. This value implied that the hydrophobic surface of the ATPase molecule must be completely coated by a single layer of phospholipid molecules for maximum activity to occur.

Ca(2+) Mg(2+)-ATPase↗
PubMed1985

Stimulation of (Ca2+ + Mg2+)-ATPase activity in human erythrocyte membranes by synthetic lysophosphatidic acids and lysophosphatidylcholines. Effects of chain length and degree of unsaturation of the fatty acid groups.

Synthetic lysophosphatidic acids and lysophosphatidylcholines were examined for their effects on the (Ca2+ + Mg2+)-ATPase of human erythrocyte membranes. Addition of these compounds to erythrocyte ghosts caused significant changes in ATPase activity. The degree of unsaturation and the length of the sn-1 long chain hydrocarbon moiety were both contributing factors. All lysophosphatidic acids tested stimulated (Ca2+ + Mg2+)-ATPase activity. Of the species having a saturated acyl group, the most active was the myristoyl derivative. Linoleoyllysophosphatidic acid was the most potent of the unsaturated species. Saturated lysophosphatidylcholines with a short chain fatty acyl group (C10 to C14) exhibited only a moderate stimulatory activity, whereas the longer chain homologues, i.e., C16 and C18 were inhibitory at high concentrations. On the other hand, unsaturated lysophosphatidylcholines had stimulatory activities comparable to the unsaturated lysophosphatidic acids. These results suggest that the acidic moiety of lysophosphatidic acid is not an important structural determinant for expressing ATPase stimulatory activity in ghosts. Rather the nature of the hydrocarbon chain as well as the lyso structure of these compounds appear most critical under these conditions. The stimulatory effects of lysophosphatidic acids or lysophosphatidylcholines were additive to that induced with calmodulin, suggesting that these lysophospholipids affect the (Ca2+ + Mg2+)-ATPase by a mechanism which is different from that seen with calmodulin.

Adult↗
PubMed1985

Accuracy of an earpiece face-bow.

The validity of the Hanau ear-bow to transfer an arbitrary hinge axis to a Hanau articulator was clinically compared with a Hanau kinematic face-bow. The study was conducted with 18 randomly selected patients. This investigation demonstrated a significant statistical difference between the arbitrary axis located with an ear-bow and the terminal hinge axis. This discrepancy was significant in the anteroposterior direction but not in the superior-inferior direction. Only 50% of the arbitrary hinge axes were within a 5 mm radius of the terminal hinge axis, while 89% were within a 6 mm radius. Furthermore, the ear-bow method was not repeatable statistically. Additional study is needed to determine the practical value of the arbitrary face-bow and to pursue modifications to improve its accuracy.

Dental Articulators↗
PubMed1985

Aluminum-based temporary removable partial dentures.

The fabrication of an aluminum-based temporary removable partial denture has been presented. The advantages of this type of prosthesis include compatibility with oral tissues, accuracy of fit, decreased bulk, and improved thermal conductivity.

Aluminum↗
PubMed1985

The cast round RPA clasp.

The incorporation of a cast round clasp into the RPA design has been presented. When properly used, the cast round clasp eliminates the need for blockout of the facial aspect of the terminal abutment normally required with the half-round clasp. This technique includes surveying the refractory cast, which ensures optimal placement of the round clasp in relation to the height of contour.

Dental Abutments↗
PubMed1985

Duplicate casts in fabrication of temporary removable partial dentures.

The use of blocked-out duplicate casts in the fabrication of temporary removable partial dentures has been described. Temporary removable partial dentures produced in this controlled manner fit properly and aid in minimizing intraoral damage. Accuracy of fit is assured because all relief is accomplished by block out on the surveyor during the laboratory phase rather than by random grinding of the prosthesis at insertion. In addition, the original cast is salvaged and can be used as a meaningful reference during the finishing process in the laboratory (Fig. 5).

Dental Casting Technique↗
PubMed1985

Modified finish line in distal extension maxillary removable partial dentures.

Finish line modifications provide adjustability and facilitate relining in the hamular notch as changes in tissue contour dictate. Time problems and inconvenience of dealing with a metal-acrylic resin junction, are eliminated while necessary postinsertion procedures are accomplished. In addition, the acrylic resin denture base is retained securely to the metal framework for the entire length of the external finish line.

Acrylic Resins↗
PubMed1985

Treatment of proximal hind-limb lameness in cattle.

Lameness of the hind limb (tarsus and proximal) in cattle is considered from the viewpoint of diagnosis and prognosis. Indications and techniques for radiography are discussed, as well as when indicated.

Animals↗
PubMed1984

Phospholipids as dynamic participants in biological processes.

Phospholipids are described as active biological molecules. Three distinctly different roles are examined. The first centers on protein-lipid interactions and the lipid requirement expressed by certain enzymes. This category is illustrated by two soluble proteins of the blood coagulation scheme, Factor IXa and Factor Xa, and by an integral membrane protein, the (Ca2+ + Mg2+)-ATPase of human erythrocytes. The next two examples depict phospholipids as active participants in membrane-mediated events. In the first of these, termed the phosphoinositide effect, a phospholipid becomes a substrate during membrane signaling, and its products presumably act as second messengers. In the second example, a phospholipid is a signal that, among other reactions, induces the phosphoinositide effect. Here, the phospholipid (platelet activating factor) serves as a lipid chemical mediator. These examples show that phospholipids behave not only as structural molecules but also as dynamic, functionally important components of cells.

Blood Coagulation↗
PubMed1984

Rabbit platelet calcium ATPase differs from the human erythrocyte (Ca2+ + Mg2+)-ATPase in its response to three purified phospholipases A2, exogenous phospholipids and calmodulin.

Human erythrocyte (Ca2+ + Mg2+)-ATPase and calcium ATPase of rabbit platelets were compared by their responses to a variety of treatments. These included three purified phospholipases A2 (acidic, neutral and basic) from Agkistrodon halys blomhoffii, as well as several phospholipids and lysophospholipids. The erythrocyte enzyme was stimulated 2-3-fold by all three phospholipases with maximal stimulation occurring at different concentrations of the three enzymes. The basic phospholipase was the most potent, followed by the neutral and acidic enzymes in that order. The calcium ATPase activity of the platelet was also stimulated by phospholipase treatment, but only by 10-20%. The stimulatory activity was attributable to hydrolysis of a very small portion of the total membrane phospholipid. Inactivation of the phospholipases by heating or chemical modification with p-bromophenacyl bromide abolished their ability to stimulate. Addition of polyphosphoinositides stimulated both ATPases. However, another acidic phospholipid, lysophosphatidic acid, stimulated only the erythrocyte enzyme and failed to affect the platelet calcium ATPase. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) had no effect on either enzyme, while the platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), its lyso compound and lysoPC inhibited both ATPases. Calmodulin stimulated the erythrocyte enzyme, but did not affect the platelet calcium ATPase. These results demonstrate that the protein-lipid interactions operative in the erythrocyte and platelet calcium ATPases are quite different.

Adenosine Triphosphatases↗
PubMed1984

Long chain oxoaldehydes and oxoalcohols from esters as major constituents of the surface lipids of Manduca sexta pupae in diapause.

Lipid constitutents of diapausing pupae of the tobacco hornworm, Manduca sexta (L), were identified by thin layer and gas-liquid chromatography, IR spectroscopy, and gas-liquid chromatography-mass spectrometry. Surface wax was a mixture of long chain polar compounds: oxoalcohol esters, oxoaldehydes, primary alcohol esters, and oxoalcohols, as listed in descending order of abundance. The distribution of the alcohols and aldehydes was C28 (75-85%), C27 (5%), and C26 (10-15%). The C26 compounds were largely 11-oxo isomers, but the C28 compounds consisted of similar amounts of 11- and 12-oxo isomers. The identities of the oxoaldehydes were confirmed by selective and complete NaBH4 reductions to yield oxoalcohols and diols, respectively. Mass spectral interpretations were verified with mass spectra of the oxoaldehyde, oxoalcohol, and diol synthesized from 12-hydroxystearic acid. Reduction of the total lipids with NaBH4 and hydrolysis of the product with ethanolic KOH gave oxoalcohols (85%), primary alcohols (8%), and oxoacids (5%); 30-40% of the oxoalcohols were derived from NaBH4-reduced oxoaldehydes, 5-10% were from free oxoalcohols, and 50% were from esters. Primary alcohols only existed as esters. Large quantities of fatty oxoalcohols relative to fatty oxoacids in the saponified mixture suggested the presence of esters other than those composed of long chain acids and alcohols. Oxoacids appeared to be mainly oxidation products of the oxoaldehydes.

Aldehydes↗
PubMed1984

Novel surface lipids of diapausing Manduca sexta pupae. Long chain oxoalcohol esters of acetoacetic, hydroxybutyric, and acetic acids.

Ester components in the surface wax from diapausing tobacco hornworm pupae, Manduca sexta L., were separated by thin layer chromatography and gas-liquid chromatography, and characterized by infrared spectroscopy and gas-liquid chromatography-mass spectrometry. Three groups of esters were identified as natural derivatives of acetic acid, acetoacetic acid, and 3-hydroxybutyric acid. The major ester fraction was identified as a mixture of C26 (10%), C27 (5%), and C28 (85%) oxoalcohol esters of acetoacetic acid. The major homolog consisted of equal amounts of 11-oxooctacosanyl 3-oxobutanoate and 12-oxooctacosanyl 3-oxobutanoate. Lesser amounts of 11- and 12-oxooctacosanyl and n-octacosanyl esters of acetic and 3-hydroxybutyric acids were also identified. The chain length distributions of these C26, C27, and C28 oxoalcohol and n-primary alcohol ester moieties, as well as the isomeric ratios for the 11- and 12-oxoalcohol isomers, were similar to the oxoaldehydes and unesterified oxoalcohols previously identified by Buckner et al (Buckner, J. S., Nelson, D. R., Haak, H., and Pomonis, J. G. (1984) J. Biol. Chem. 259, 8452-8470) as lipid components of the surface wax of M. sexta pupae.

Acetates↗
PubMed1984

Zinc deficiency in sheep and goats: three field cases.

Zinc deficiency was diagnosed in 2 flocks of sheep and a herd of goats. Alopecia and eating of wool were observed. Skin lesions were hyperkeratosis and parakeratosis. Abnormal hoof growth and a closed stance with arched back and bowed hindlimbs were seen. Anorexia, depression, and foot soreness diminished quickly after zinc supplementation. Skin lesions healed and hair and wool growth resumed. A cause for the deficiency could not be established.

Animals↗
PubMed1984

Role of nitrogen assimilation in seed development of soybean.

A nondestructive acetylene reduction assay for nitrogenase activity of soybean (Glycine max L. Merr) field plots is presented. Plots consisted of 120 x 150 x 30 centimeter boxes containing 65 plants. The plants were grown in a medium grade sand under controlled nutrient, moisture, and root temperature conditions. Acetylene at a concentration of 10 milliliters per liter was circulated through manifolds in the chambers; equilibration required 5 minutes, and activity was linear with time. Optimum growth and assay environments resulted in activity of 70 micromoles ethylene per plant per hour. Plant development and yield were comparable to soil-grown companion plots.The well accepted hypothesis that developing seeds deprive the nodules of carbohydrate was not substantiated. The nondestructive acetylene reduction profile did not decline until 30 days after the onset of seed development (R-5). This result was consistent with reports from the literature which indicated that 60% of seasonal nitrogen was fixed after R-5. Further, a high correlation shown between integrated seasonal acetylene reduction and yield (r = 0.999) suggested a cooperative relationship between the roots and shoot. A reduction in source:sink ratio (60% defoliation) after R-5 had no effect on acetylene reduction. This showed that neither an increase in sink demand by the pods nor a carbon shortage during podfill decreased dinitrogen fixation. A conceptual model relating seed growth with carbon and nitrogen assimilation is proposed.

Journal Article↗