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This article discusses the results of a research study conducted to determine the levels of magnesium present in human saliva using atomic absorption spectroscopy. The study finds the mean magnesium value of unstimulated saliva to be .502 milligrams (mg) per cent and of stimulated saliva to be .356 mg per cent.

This article discusses the results of a research study conducted to determine the levels of calcium present in human saliva using atomic absorption spectroscopy. The study finds the mean calcium value of unstimulated saliva to be 6.24 milligrams (mg) per cent and of stimulated saliva to be 5.87 mg per cent.

Examines the effect of changes in vasomotor tone on the volume distensibility of the femoral artery in the living dog. Topical application of acetylcholine or noradrenaline to induce alterations in the diameter of the exposed femoral artery; Use of electrical caliper to record the diameter; Similarity of the changes in mean diameter to the reported changes accompanying variations in sympathetic activity.

All possible combinations of four measurements of blood pressure, blood flow and vascular diameter are examined by transmission-line theory. It is found that only nine measurement combinations can give the attenuation coefficient gamma, reflection coefficient R and characteristic impedance Z0 simultaneously. At least one pressure measurement must be included. Their general expressions with arbitrary measuring locations are presented, together with some simplified forms which cover all the previous methods. A greater choice of method is thereby made available for use in practice. The results show that, regardless of the measurement locations, all combinations can be solved in the order gamma first, R second and Z0 last.

The purpose of this study was to assess the role of conductance catheter position within the right ventricle in obtaining adequate indications of phasic changes in ventricular volume. Possible applications of this technology are in rate responsive pacemakers and implantable defibrilators. The conductance catheter was placed in the right ventricle by cannulation of a jugular or femoral vein or a branch of the pulmonary artery. Position within the ventricle was documented from biplane fluoroscopy. Stroke volume was perturbed by: bolus injection of blood, vagal stimulation, venous infusion of methylcholine chloride, or isoprenaline. Four criteria were used to assess the quality of volume signals: (1) volume signal phase relative to the electrocardiogram; (2) magnitude parity of volume change from each electrode pair; (3) freedom from artifact; and (4) indication of stroke volume change during interventions. Greyhound dogs of either sex (n = 33), weight 20-32 kg. A total of 236 recordings from 14 distinct catheter positions were analyzed. Catheter positions originating from a femoral cannulation and one position from the pulmonary artery gave markedly superior volume transduction compared to those from the jugular route. Although right ventricular volume transduction was possible from all catheter trajectories, those resulting from the femoral approach were clearly superior. In the right ventricle, the inability to transduce a sufficient proportion of ventricular volume, in concert with the potential sensitivity of the catheter to atrial volume changes, may seriously limit the potential of the conductance technique in the applications envisaged.

A method is described for the quantitation of atherosclerotic lesion after excision and staining of the vessel. Essentially the device consists of a microscope with a computer-controlled stage which moves a photographic negative image over a square beam (o.1 mm sides) of light. At each translation-step of the stage a transmittance reading is taken using a photomultiplier tube for detection. The computer stores topographical values (typically around 6,000) and, by setting a threshold, can determine the fractional area of artery which is diseased.

A new microindentation technique using a small, loaded spherical probe (25 microns diameter) was developed to quantify early mechanical changes in the arterial intima during atherogenesis. Routine use of forces of 10 microN on normal intima for 10 S resulted in indentations of about 2.5 microns which gives an intimal compliance of 0.245 +/- 0.031 m/N. There was a decrease in intimal compliance in the proximal to distal direction in both the rabbit and the dog thoracic aorta. The region immediately distal to an intercostal orifice in the rabbit was often up to 1.6 times more compliant (softer) than surrounding areas while the corresponding region in the dog tended to be less compliant than elsewhere. Feeding a 1% cholesterol diet to rabbits for 8 weeks increased the intimal compliance to 0.368 +/- 0.041 m/N. The regions distal to the intercostal ostium were 32% more compliant after 4 weeks of cholesterol diet than non-orifice-related areas but after 8 weeks of the diet there was no significant difference between these regions. The time course of indentation (viscous component) was characterised by a rapid indentation phase which almost became non-exponentially asymptotic by 6 S and was 66 +/- 3% SD of this value by 1 S. Cholesterol feeding (8 weeks) altered this phase to 76 +/- 4% SD of the asymptotic value after 1 S of indentation, indicating a decrease in initial viscosity. A very slow indentation or creep was also found when the force continued for a period up to 25 min. Cholesterol feeding increased this rate of creep by approximately 15%. The results show that early atheromatous changes induced by cholesterol feeding are accompanied by softening and increased fluidity of the aortic intima.

The electrical conductivity of blood is sufficiently higher than that of myocardium to make feasible the detection of cardiac volume changes by measurement of intraventricular fluid conductance. An eight-electrode catheter was used to inject an alternating current (100 microA or less, at 1500 Hz) via the two electrodes nearest the ventricular base and apex, then the resulting five voltage differences between adjacent pairs of the six intervening electrodes were measured. When current amplitude was held constant, the cross-sectional area of the ventricular cavity slice defined by planes perpendicular to the catheter through the relevant pair of electrodes was inversely proportional (to the first order) to the voltage difference. Measurement of multiple segments compensated for isovolumic cavity shape changes. The technique had previously been shown to measure left ventricular volume successfully, but the geometry of the right ventricle made this measurement more problematical. Using open-chested, anesthetized greyhounds, we compared the catheter-measured right ventricular volume change with stroke volume as measured by a pulmonary arterial electromagnetic blood flowmeter. With optimal catheter placement, good correlation between stroke volume and catheter-measured volume changes was achieved when stroke volume was perturbed on a beat-to-beat basis. In six data records from three dogs, involving two different means of varying stroke volume (rapid injection of blood and sinus node irritation), the correlations yielded r2 values between 0.82 and 0.98.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulsatile pressure and flow were measured in the ascending aorta and other arteries of 22 anesthetized rabbits and 16 anesthetized guinea pigs. Pressure/flow relationships were expressed as vascular impedance. Aortic flow waves were almost identical in the two species, but pressure waves were quite different. Reflected pressure waves returned earlier from the periphery in guinea pigs, augmenting pressure during late systole and resulting in relatively high external left ventricular work, an inappropriately larger difference between mean systolic and mean diastolic pressure and absence of any aortic diastolic pressure wave. Values of impedance modulus and phase were similar but differed in the frequency at which maxima and minima occurred. In both species, impedance curves were interpreted to indicate a functionally discrete reflecting site in the lower body whose position corresponded to the region of the aortic bifurcation. In addition, rabbits showed evidence of an upper body reflecting site approximately one-third as far distant from the heart. As in dogs, the arterial system in both species can be represented by an asymmetrical T-shaped model of realistic dimensions.

A fully automated instrument was developed that measured the amount and time-course of indentation of arterial intima by a spherical tipped probe 25 micrometers in diameter loaded routinely by forces of 10 microN. The relationship of depth of indentation to time was non-exponential but reached an apparent asymptotic value in about 6 s. Routine indentations were recorded 10 s after loading, the relationship of indentation and force being essentially linear between 0-100 microN. The instrument is an order of magnitude more sensitive than one previously described (Gow and Vaishnav, 1975, J. Appl. Physiol. 38, 344-350) and produces indentations of 1-4 micrometers in the intima of rabbit thoracic aorta with a reproducibility of 1-2%. Preliminary usage of the new microindentor has shown increases in the compliance of the thoracic aorta intima in rabbits during cholesterol feeding.