The microvascular unit size for fractal flow heterogeneity relevant for oxygen transport.

In this study we used a computer model for oxygen transport in heterogeneously perfused tissue to define the microvascular unit size of relevance to oxygen transport. Flow within this unit is presumably heterogeneous, but this internal heterogeneity is by definition of negligible importance for the oxygen tension distribution. In saline-perfused heart the linear dimension of the thus defined unit is 500 microns, in blood-perfused heart it is 100 microns.

Function of isolated rabbit hearts perfused with erythrocyte suspension is not stable but improvement may be feasible with hemoglobin solution.

In the present study isolated rabbit hearts were perfused with erythrocyte suspensions (hematocrit 21.5 +/- 0.5%) or hemoglobin solutions according to Langendorff with a constant flow at 37 degrees C.

Hypochondriasis in ENT practice.

In this study the incidence of hypochondriasis among new ENT out-patients was investigated. A validated questionnaire, which was administered twice with an interval of 3 months, was used to make the diagnosis. Medical information also played a part in the assessment.

Dynamics of myocardial lactate efflux after a step in heart rate in isolated rabbit hearts.

We investigated whether a glycolytic burst contributes to the initial adaptation of ATP synthesis to increased cardiac metabolic demand. Six isolated rabbit hearts were perfused with glucose-containing Tyrode solution at 28 degrees C. In venous and arterial samples the lactate concentration was determined with a sensitive enzymatic cycling method.

Adaptation speed of cardiac mitochondrial oxygen consumption decreases with higher heart rate.

The purpose of the present study was to determine whether the mean response time of cardiac mitochondrial oxygen consumption after a step in metabolic demand is constant in heart muscle, as has already been found for skeletal muscle. The mean response time reflects the average delay between the change in ATP hydrolysis due to a heart rate step and mitochondrial ATP production. Isolated rabbit hearts with a water-filled balloon in the left ventricle were perfused according to Langendorff with a constant flow of Tyrode solution at 28 degrees C.

Pilot study on light dosimetry for endobronchial photodynamic therapy.

Endobronchial photodynamic therapy (EB-PDT) using photofrin as the photosensitizer is currently being evaluated as a new treatment modality for inoperable endobronchial tumors. One of the current problems with EB-PDT is the lack of adequate light dosimetry, which hampers proper interpretation of treatment results. In this study exploratory light dosimetry experiments were performed in plastic bronchus models using either a microlens-tipped fiber (suitable for illumination of small superficial tumors) or a cylindrical diffuser fiber (suitable for intraluminal illumination or interstitial illumination of partially obstructing tumors).

Adverse patient occurrences in a university hospital: a comparison of screening results registered by specialists and by external review.

A quality assurance system for generic screening of patient care has been developed in a university hospital in The Netherlands. This system is based on the Medical Management Analysis System, developed in the United States. Patient care is systematically screened for adverse patient occurrences (APOs).

Acidosis slows the response of oxidative phosphorylation to metabolic demand in isolated rabbit heart.

The purpose of this study was to investigate the effect of acidosis on the mean response time of mitochondrial oxygen consumption to steps in heart rate and in left ventricular balloon volume. The mean response time may be viewed as the average delay between a change in adenosine triphosphate (ATP) hydrolysis and oxygen consumption. The mean response time is calculated by subtracting the transport time, required for diffusion of oxygen and for convective transport through the coronary vessels, from the response time measured in the coronary venous effluent.

Oxygen measurement inside an NMR magnet with a catheter electrode.

In this study we show the possibility of continuous oxygen tension measurement inside an NMR magnet without disturbance of simultaneous NMR data acquisition. Our modified Clark-type oxygen electrode has a fast response (2 s) and can be inserted deep into small bore NMR systems thanks to its small diameter (2 mm).

Continuous pneumothorax monitoring by remittance measurement.

The feasibility of a noninvasive method, based on a remittance measurement, to monitor continuously for the occurrence of pneumothorax in neonates under ventilation, was investigated through animal experiments. Light from a He-Ne laser (632.8 nm) or a semiconductor laser (790 nm) was incident on the chest wall of rabbits and piglets.

Double-integrating-sphere system for measuring the optical properties of tissue.

A system is described and evaluated for the simultaneous measurement of the intrinsic optical properties of tissue: the scattering coefficient, the absorption coefficient, and the anisotropy factor. This system synthesizes the theory of two integrating spheres and an intervening scattering sample with the inverse adding-doubling algorithm, which employs the adding-doubling solution of the radiative transfer equation to determine the optical properties from the measurement of the light flux within each sphere and of the unscattered transmission. The optical properties may be determined simultaneously, which allows for measurements to be made while the sample undergoes heating, chemical change, or some otherexternal stimulus.

Modeling the effect of wavelength on the pulsed dye laser treatment of port wine stains.

To determine the influence of wavelength on the depth of vascular injury in port wine stains following pulsed dye laser treatment, we calculated fluence rates at wavelengths varying from 415 to 590 nm in a two-layer Monte Carlo model representing the epidermis and the dermis. Calculations were made for four different volumetric fractions of blood in the dermis: 0%, 1%, 5%, and 10%. The depth of the selective vascular injury was determined to be the depth at which the rate of temperature rise at some point within the vessel just equals that at the epidermal-dermal junction.

Changes in the optical properties (at 632.8 nm) of slowly heated myocardium.

The three transport equation optical properties, the absorption coefficient, the scattering coefficient, and the average cosine of the scattering angle, or anisotropy factor have been measured (at 632.8 nm) for canine myocardium after it is heated in a water bath at room temperature and at 37-75 degrees C for 1000 s. The measurement system was a double integrating sphere with collimated light and utilized the adding-doubling solution to the equation of radiative transfer.

Mitochondrial dehydrogenase activity affects adaptation of cardiac oxygen consumption to demand.

The effect of regulation of mitochondrial dehydrogenase activities on the mean response time of mitochondrial oxygen consumption, which characterizes the delay between changes in ATP hydrolysis and changes in oxygen consumption, was investigated in isolated rabbit hearts and perfused with Tyrode solution at 28 degrees C. Perfusion with ruthenium red (RR) blocks mitochondrial calcium uptake and thus decreases mitochondrial dehydrogenase activities. Perfusion with pyruvate increases pyruvate dehydrogenase activity.

Optical properties of rat liver and tumor at 633 nm and 1064 nm: photofrin enhances scattering.

Predicting the effects of photodynamic therapy (PDT) and Nd: YAG laser coagulation requires knowledge of the light distribution in tumor and surrounding tissue. Therefore, absorption and scattering coefficients and the average cosine of the scattering angle (the anisotropy factor) were measured in rat liver and tumor at 632.8 and 1064 nm.

Calculation of oxygen diffusion across the surface of isolated perfused hearts.

Although exact mathematical descriptions of oxygen diffusion into unperfused isolated organs are known, no analytic solution is available for perfused organs. Here, we derive an equation for oxygen diffusion across the epicardial surface of perfused hearts. Our oxygen transport model incorporates oxygen delivery from the capillary perfusate, oxygen consumption, diffusion among adjacent capillary exchange regions, and diffusion across the epicardial surface.

Mapping strategy for resistance genes in tomato based on RFLPs between cultivars: Cf9 (resistance to Cladosporium fulvum) on chromosome 1.

The contribution of introgressed regions derived from wild species to the genetic variation within the species of Lycopersicon esculentum was investigated by comparing the RFLP patterns of 2 introgression-free, obsolete cultivars ('Moneymaker' and 'Premier') and a modern cultivar ('Sonatine') that carries at least 5 introgressed resistance genes. In this analysis 195 mapped nuclear markers were used in combination with 6 restriction enzymes. Among the 1170 probe-enzyme combinations tested, only 3 showed a polymorphism between the 2 introgression-free cultivars.

The early stages of polyp formation.

The purpose of this study is to describe polyp formation in the mucosa of the middle ear as a possible model for the pathogenesis of nasal polyps. In 65 Wistar rats, the eustachian tube was occluded on the left side for up to 20 months; 60 right-sided, nonoccluded ears served as controls. Following occlusion, the middle ear mucosa was examined for signs of polyps.

Influence of temperature on the response time of mitochondrial oxygen consumption in isolated rabbit heart.

1. In this study we determined the temperature dependence of the mean response time of cardiac mitochondrial oxygen consumption following steps in metabolic demand. Metabolic demand was altered by stepwise changes in heart rate or in left ventricular volume at 20 and 28 degrees C.

Effects of modified hemoglobin solutions on the isolated rabbit heart.

The effects of modified hemoglobin (Hb) solutions on the coronary vasculature were studied. Hearts were perfused according to Langendorff with constant flow of Tyrode solution. The solutions studied were stroma- free Hb, prepared by lysis of red blood cells in water (SFHb-lys), or prepared by swelling of red blood cells in hypotonic phosphate buffer (SFHb).

Polyploidy in pleomorphic adenomas with cytological atypia.

Occasionally, in fine-needle aspirates of pleomorphic salivary gland adenomas, considerable cytonuclear atypia is present, which may give rise to a false-positive diagnosis. In this study DNA cytophotometry was performed on Feulgen restained smears prepared from material obtained by needle aspirates of normal salivary glands (n = 4), pleomorphic adenomas with (n = 5) and without (n = 4) atypia and a carcinoma in a pleomorphic adenoma. The results showed a clear diploid DNA histogram in the specimens of normal salivary gland and pleomorphic adenomas without atypia.

Response time of cardiac mitochondrial oxygen consumption to heart rate steps.

We investigated the time course of cardiac mitochondrial O2 consumption following steps in heart rate in 16 isolated rabbit hearts perfused with Tyrode solution. The time course was characterized by the mean response time, i.e.