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Biomedical subjects

L Marks

Publications and source records attributed to L Marks.

At least 55 records · Page 3Linked to original sources
PubMed1990

Effect of multiple firing on the bond strength of selected matched porcelain-fused-to-metal combinations.

In this study two different opaque porcelain-metal combinations were evaluated for planar shear bond strength. Samples were tested after one, three, five, seven, and nine different firing cycles to evaluate the effect of repeated firing on shear bond strength. For the combination of Will Ceram/W1 and Vita/Olympia materials, no statistical difference was observed either between materials or after repeated firing. For apparently well-matched porcelain-metal combinations, no significant reduction in bond strength occurs during normal firing of the opaque porcelain to the metal.

Analysis of Variance↗
PubMed1990

Phenylalanine flux in adult men: estimates with different tracers and route of administration.

The kinetics of three different tracers of phenylalanine were studied when continuously infused together either by an intravenous (IV) or intragastric (IG) route in six young healthy men during a fasting state. During IV infusion, mean flux values were 39.2 +/- 1.8, 40 +/- 3, 41.8 +/- 3.6 mumol.kg-1.h-1 for L-[ring-2H5], [15N], and L-[1-13C]phenylalanine, respectively (differences not significant). Fluxes were higher (P less than .001) during IG than IV infusion, indicating a disappearance of tracer during the first pass through the splanchnic area. Also, higher fluxes were found for [ring-2H5]phenylalanine (74 +/- 6.23 mumol.kg-1.h-1) compared with [15N] and L-[1-13C]phenylalanine (54.24 +/- 4.7 and 61.15 +/- 5.3 mumol.kg-1.h-1) during IG infusion. Proton exchange might explain this difference, possibly limiting in vivo use of this label when the tracer is to be administered by the IG route.

Adult↗
PubMed1988

Infused and ingested labeled lysines: appearance in human-milk proteins.

Incorporation of two labeled forms of lysine into human-milk proteins was studied in fasted lactating subjects to determine whether highly labeled proteins could be produced for subsequent nutritional studies and whether the kinetics of milk synthesis could be studied in humans with stable isotope techniques. Five subjects, maintained on formula diets, received L-[13C1]lysine (27 mumol/kg) as an IV bolus and L-[15N2]lysine (27 mumol/kg) as an oral bolus 4 h postprandially. Milk samples were collected at 30, 45, 90, 150, 240, and 360 min. Tracer lysine levels in the hydrolysate of unfractionated milk protein were determined by gas chromatography-mass spectrometry isotope ratiometry. After a delay of at least 45 min, significant labeling of milk protein was detected and reached a maximum at 150 min with cumulative percent does recovery over 6 h of 0.5%. Human-milk proteins can be labeled for nutritional investigations and in vivo kinetics of milk protein synthesis can be studied with stable isotope techniques.

Administration, Oral↗
PubMed1988

Mobility after amputation for failed knee replacement.

Management of the failed total knee replacement is a formidable problem. In a 13-year period, 24 patients with above knee amputation following unsuccessful knee replacement were referred for prosthetic limb fitting. Adequate data was available for 23 patients. At review (or at the time of death), an average of 48.6 months after amputation, only seven of the 23 patients were regular daily walkers, although 10 patients had managed to walk for more than two years; 20 of the 23 used a wheelchair for some part of the day and 12 were confined to a wheelchair.

Activities of Daily Living↗
PubMed1986

New evidence for taurine biosynthesis in man obtained from 18O2 inhalation studies.

The ability of adult humans to synthesize taurine was assessed by measurement of the 18O content of urinary taurine in eight subjects following 60 minutes inhalation of 18O2 (97% 18O). All subjects had at least one 3-hour urine collection in which the mole ratio of 18O-taurine to taurine was at least three times greater than the standard deviation of the stable isotope measurement. The peak mole ratios of 18O-taurine/16O-taurine ranged from 0.0075 to 0.015. These data indicated that adult human subjects have a significant ability to synthesize taurine.

Adult↗
PubMed1986

Lysine and protein metabolism in young women. Subdivision based on the novel use of multiple stable isotopic labels.

A multitracer stable isotope study of lysine kinetics was carried out in fasted adult female volunteers to determine whether a multicompartmental model that partitions protein synthesis and breakdown into at least two types of tissue components can be constructed from plasma and breath data. Five female subjects, maintained on formula diets, received L-[13C1]lysine (27 mumol/kg) as an i.v. bolus and L-[15N2]lysine (27 mumol/kg) as an oral bolus 4 h postprandially. Plasma and breath samples were collected for 6 h. On an alternate day, subjects received NaH13CO3 (10 mumol/kg) as an i.v. bolus and breath samples were collected for 6 h. Plasma tracer lysine levels were determined by gas chromatography-mass spectrometry isotope ratiometry, and breath 13CO2 levels were measured by mass spectrometric gas isotope ratiometry. The tracer data could be fitted to a mammillary multicompartmental model that consisted of a lysine central compartment and slow- and fast-exchanging peripheral compartments containing 37, 38, and 324 mumol/kg, respectively. The rates of lysine oxidation, incorporation into protein, and release by protein breakdown were 21, 35, and 56 mmol/kg/h, respectively, in the fast-exchanging compartment, whereas the rates of protein synthesis and breakdown in the slow compartment were both 53 mmol/kg/min. These values corresponded to a whole-body lysine flux of 106 mmol/kg/h. The kinetic parameters were in excellent agreement with reported values obtained by constant-infusion methods. The measurements indicated that it will be possible to detect changes in amino acid pool sizes and protein synthesis and breakdown associated with the mobilization of protein stores from plasma and breath measurements in multitracer stable isotope experiments.

Administration, Oral↗
PubMed1983

Sales trends and survey findings: a study of smoking in 15 OECD countries.

Annual data on tobacco sales and recent information from surveys have been used to investigate smoking trends and patterns in 15 countries in the Organization for Economic Cooperation and Development (OECD). These national smoking profiles illustrate wide variations among countries in the consumption of tobacco per adult in the population and in the percentage of male and female smokers in the population. The sales data also illustrate that the development of the market for tobacco goods has displayed marked differences over time from one country to another.

Australia↗
PubMed1978

Pressor response to saralasin (1-sar-8-ala-angiotensin II) bolus injection in hypertensive patients.

A 10 mg bolus of the angiotensin blocker saralasin was injected 113 times in 68 subjects with essential or renovascular hypertension. Ninety percent of injections caused a transient increase in blood pressure, which correlated with plasma renin activity (PRA) (r = -0.54); Mean increase at 2 minutes was 21/13.4 mm Hg (P less than 0.001) and was independent of pre-injection control blood pressure, with a rapid decrease to or below control values thereafter. Thirty-seven subjects were studied on successive days before and after furosemide-induced sodium depletion (152 +/- 26 mEq [SE] sodium loss). In the low renin group, sodium depletion did not change PRA or the magnitude of the pressor response to saralasin, but significantly decreased control MAP by 13 mm Hg (P less than 0.01). In normal and high renin patients, MAP was unchanged after diuresis, but PRA increased significantly and the pressor response was attenuated. The net effect of sodium depletion was to reduce the pressor response to saralasin in all renin subgroups by 9 to 12 mm Hg. Saralasin bolus injection, unlike infusion, saturates available vascular receptors only briefly, eliminating prolonged pressor responses.

Adolescent↗