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PubMed1989

Decreased reflection coefficient as a possible cause of low blood pressure in severe septicaemia.

A 44-year-old woman developed a septicaemia with low intra-arterially recorded blood pressure values despite vasoactive medication and optimal support. Sphygmomanometer cuff measurements showed higher values than intra-arterial blood pressure records. We suggest a low reflection coefficient of the capillary bed as the cause of this phenomenon. The constant pressure of the sphygmomanometer cuff on the venous tract appeared to create an increase of the reflection coefficient in our patient, thus causing higher blood pressure readings with the sphygmomanometer cuff measurements than expected.

Adult↗

PubMed1992

Protective effect of a prostaglandin oligomer on liver mitochondria in situ: time-shared measurements of fluorescence and reflectance in the cold-preserved rat liver.

The protective effect of a new oligomeric derivative of prostaglandin B2, known as OC-5186, was evaluated using time-sharing spectrofluorometry in the cold-preserved rat liver. Experiments were divided into three groups: in group A, a 5000 ng dose of OC-5186 was administered via the peripheral vein, 1000 ng via the portal vein, and 200 ng/ml in University of Wisconsin (UW) solution; in group B, the OC-5186 dosage was ten times greater than that in group A; in group C (control group), liver procurement and storage were performed without OC-5186. At 0, 12, and 24 h after cold preservation at 4 degrees C, the liver was perfused for 30 min at 12 degrees C with oxygenized Krebs-Henseleit solution, after which the perfusate was switched to deoxygenized Krebs-Henseleit solution. Time sharing spectrofluorometry was used to follow NADH fluorescence at 450 nm with a 360-nm excitation wavelength, as well as the reflectance of cytochrome aa3 with 605 minus 620 nm from oxidation to reduction. Rate constants of NADH fluorescence and cytochrome aa3 reflectance were used as indices of integrity of the mitochondrial respiratory chain. In group C, the rate constant of NADH fluorescence decreased significantly (P < 0.05) from the control value of 8.31 +/- 0.21 x 10(-3) (sec-1) to 4.97 +/- 0.15 x 10(-3) and 5.58 +/- 0.16 x 10(-3) (mean +/- SEM) at 12 and 24 h after cold preservation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1977

Equatorial x-ray reflections from contracting muscle after an applied stretch.

The equatorial X-ray reflections were recorded from contracting muscle after a slow stretch. The intensity ratio of the 1,0 to the 1,1 reflections (I10/I11) after the stretch was not significantly different from that during an isometric tetanus at the same sarcomere length, although the tension after the stretch was considerably greater than isometric. This suggests that an almost identical number of cross-bridges produce a greater tension after a slow stretch than during an isometric tetanus.

Animals↗

PubMed1987

Quantitative evaluation of optical reflection spectra of blood-free perfused guinea pig brain using a nonlinear multicomponent analysis.

After developing a blood-free perfused preparation of the guinea pig brain a nonlinear multicomponent analysis (NLMCA) of the reflection spectra of the brain surface was worked out by which the redox state of cytochrome aa3, c, and b could be evaluated quantitatively and almost continuously. The NLMCA allowed to simulate the tissue reflection spectra in such a way that only a small statistical error remained between the recorded and the computed spectra. Using redox states of cytochrome aa3 and c as an intracellular oxygen probe it was found that in order to supply the guinea brain with sufficient oxygen by a saline medium equilibrated with 95% oxygen and 5% CO2 the temperature had to be reduced to 18-20 degrees C. At this temperature cytochrome aa3 was 95% oxidized.

Animals↗

PubMed1980

Visual and auditory selective attention and reflection-impulsivity in normal and learning-disabled boys at two age levels.

Selective attention to visual and auditory stimuli and reflection-impulsivity were studied in normal and learning-disabled 8- and 12-year-old boys. Multivariate analyses, followed by univariate and paired-comparison tests, indicated that the normal children increased in selective attention efficiency with age to both visual and auditory stimuli. Learning-disabled children increased in selective attention efficiency with age to auditory, but not to visual, stimuli. Both groups increased with age in reflection as measured by Kagan's Matching Familiar Figures Test (MFF). The 8-year-old learning-disabled children were more impulsive than the 8-year-old normals on MFF error scores, but not on MFF latency scores. No difference occurred between the 12-year-old learning-disabled and normal children on either MFF error or MFF latency scores. Correlations between the selective attention scores and MFF error and latency scores were not significant.

Age Factors↗

PubMed1986

Estimated hepatic oxygen consumption in patients with chronic liver diseases as assessed by organ reflectance spectrophotometry.

We investigated the estimated hepatic oxygen consumption by reflectance spectrophotometry during peritoneoscopy and the rate of in vitro oxygen consumption of liver slices obtained by liver biopsy using the oxygen electrode apparatus in patients with chronic liver diseases. The estimated hepatic oxygen consumption decreased concomitantly with the decrease in blood supply, expressed as the regional hepatic blood hemoglobin concentration, and it was significantly decreased in cirrhosis compared to chronic hepatitis. The estimated hepatic oxygen consumption also was significantly correlated with the serum albumin level, 15-min retention rate of indocyanine green, and prothrombin time. There was no correlation between the estimated hepatic oxygen consumption calculated from the reflectance spectra and the rate of in vitro oxygen consumption measured by the oxygen electrode apparatus. Most cirrhotic liver slices had a respiratory rate comparable to that in chronic hepatitis. Thus, it is concluded that the reduction of estimated hepatic oxygen consumption in cirrhosis of the liver is mainly due to the reduction of oxygen supply secondary to the decrease of hepatic blood flow.

Adult↗

PubMed1999

Evolutionary changes reflected by the cellular amino acid composition.

Comparison of the amino acid composition of cell-proteins using 17 amino acids has been used to investigate the biological evolution of organisms such as bacteria, blue-green alga, green alga, fungi, slime mold, protozoa and vertebrates. The degree of difference in the amino acid ratios between any two groups reflects the degree of divergency in biological evolution. The amino acid composition of the Gram-negative bacteria (Escherichia coli, Klebsiella, Proteus, and Vibrio alginolyticus) was identical. However, the amino acid composition of Staphylococcus aureus and Bacillus subtilis, which are Gram-positive bacteria, differed from each other and from the Gram-negative bacteria. The amino acid composition of the blue-green alga (Cyanobacterium, Chroococidiopsis) was quite similar to that of E. coli. A marked difference in the amino acid composition was observed between E. coli and green alga (Chlorella), and significant differences were observed between E. coli and other organisms, such as fungi, protozoa (Tetrahymena), slime mold (Dictyostelium discoideum) and vertebrates. In conclusion, the change in cellular amino acid composition reflects the divergence which has occurred during biological evolution, whereas a basic pattern of amino acid composition is maintained in spite of a long period of evolutional divergence among the various organisms. Thus, it is proposed that the primitive life forms established at the end of prebiotic evolution had a similar amino acid composition.

Amino Acids↗

PubMed1990

Effect of submucosal epinephrine injection on local gastric blood flow. A study using laser Doppler flowmetry and reflectance spectrophotometry.

Clinical studies have demonstrated the efficacy of submucosal epinephrine injection in the control of bleeding ulcers. Since endoscopic techniques for assessing gastroduodenal blood flow are limited, we employed an animal model to study the mechanism of control of bleeding. The effect of submucosal epinephrine injection on local gastric blood flow was studied in the rat using laser Doppler flowmetry and reflectance spectrophotometry. Submucosal injection of 0.1 ml of 1/10,000 epinephrine caused a significantly greater drop in local gastric blood flow (laser Doppler flowmetry) compared with vehicle (10% sodium metabisulfite) injection. The reduction persisted for up to 120 min. This vasoconstrictive effect of epinephrine was confirmed by observations with reflectance spectrophotometry, which documented a pattern of ischemia without congestion (lower index of hemoglobin concentration, lower index of oxygen saturation). The autoregulatory escape from adrenergic vasoconstriction was not evident in either instance. We conclude that, after submucosal injection of epinephrine, the absence of autoregulatory escape from adrenergic vasoconstriction and the marked and prolonged decrease in local gastric blood flow enhance the homeostatic mechanisms (eg, platelets and other coagulative factors) to effect hemostasis in bleeding ulcers.

Animals↗

PubMed1978

Voltage-induced reflectivity relaxation of bilayer lipid membranes: on changes of bilayer thickness.

Temporal and voltage-induced changes of reflectivity (R), the optical phase difference in transmitted polarized light, of tension and total capacity of bilayer lipid membrane (BLM) were studied. The membranes were mainly formed from total brain phospholipids (TP) in n-alkanes. 1) Reflectivity of "black" regions of films made of TP in decane and hexadecane decreases by several percent with a time constant (tauR) of about 30 min, whereas that of membranes with hexane and heptane does not depend on time (with an accuracy up to 1--2%). The BLM tension decreases appreciably in the course of time and reaches its steady-state value in tens of minutes after complete blackening of the membrane. 2) Under prolonged (up to tens of minutes) action of voltage (V) no R changes of BLMs with hexane, heptane, and hexadecane were revealed at a noise level of 0.2%. Blms with decane usually respond to voltage application, first by a rapid (jump-like) and then by a slow decrease of R with a value spread from 0.2% to 3%. 3) With higher amplitude and temporal resolutions of the signal (signal averaging method) it can be seen that after voltage jump R decreases down to a new steady-state value: at V = 100 mV, deltaR/R = -(2--4) . 10(-4) and tauR approximately 0.1 msec for BLMs from TP in heptane, and deltaR/R = -(3--6) . 10(-2) and tauR approximately 2 msec for BLMs from oxidized cholesterol in decane. It is shown in the latter case that the great value of deltaR/R is due to the contribution of invisible microlenses. In all the cases deltaR approximately V2. 4) It is concluded that at voltage jump a bilayer first becomes thinner due to volumic compression of its hydrocarbon core; then it spreads with a time constant of the order of 0.1 msec, getting thinner until a new equilibrium state is reached. Complete change of bilayer thickness is detah/h approximately -10(-4) at 100 mV.

Alkanes↗

PubMedDate not supplied

Measurement of upper airway movement by acoustic reflection.

The acoustic reflection method provides a noninvasive way to determine the airway geometry. Based on a discrete upper airway model, an inverse scheme is developed to infer the upper airway area as a function of distance. We incorporate this scheme into a system that can generate multiple acoustic pulses to sample the upper airway geometry at a maximum frequency of 30 Hz, making possible determination of the airway area-distance relation as a function of time. Therefore, we can monitor the dynamic behavior of the upper airway during breathing. To validate the approach, we visualized vocal cord movements in three normal subjects via laryngoscopy; simultaneously acoustic measurements were made at 10 Hz. Video images of vocal cord movement were recorded and digitized. We compared the laryngeal area from analysis of the video images with the acoustic assessment at the level of the glottis. Linear regression analysis shows that the correlation coefficients are between 0.85 and 0.9 for all three subjects. We conclude that the acoustic reflection method is a useful tool for measuring vocal cord movement without the use of laryngoscopy, and the approach promises to be a useful one to measure the movement of the whole upper airway. This paper also discusses the limitations inherent in the algorithm and some useful procedures to ensure accurate and reliable area computation during implementation.

Acoustics↗

PubMed1991

Evaluation of a new reflectance pulse oximeter for clinical applications.

The design of a noninvasive reflectance pulse oximeter that uses the same principle of transmittance pulse oximeter and analyses the oxygen saturation of arterial blood was described. Four sets of red and infra-red LEDs were used as light sources. The respective reflectance photoelectric outputs were used to make an internal calibration curve of the instrument relative to the arterial oxygen saturation values measured with a Co-Oximeter (OSM-3) in five healthy nonsmoking subjects during steady-state hypoxaemia. The accuracy of the present instrument was studied in six patients with respiratory failure. From 22 samples, a good correlation coefficient (0.98) with a standard deviation of 1.42 was obtained in the range between 73 and 100 per cent between the arterial oxygen saturation measured with the present instrument and that with the Co-Oximeter. The result strongly suggests the usefulness of this oximeter in monitoring patients with hypoxaemia.

Adult↗

PubMed1991

Experimental studies on the prediction and prevention of stress ulcers using tonometry, reflectance spectrophotometry and oxygenated perfluorochemicals.

The present study investigates whether oxygenated perfluorochemicals protect the gastric mucosa against hemorrhage-induced stress ulceration. The influence of oxygenated perfluorochemicals on both macroscopic and microscopic lesion formation, gastric intramural pH, index of oxygen saturation and index of hemoglobin saturation of the gastric mucosa was studied. To assess the severity of gastric mucosal ischemia, intramural pH was directly measured using a pH sensitive microelectrode and indirectly by utilizing hollow viscus tonometry, and the indices of oxygen saturation and hemoglobin saturation were measured by reflectance spectrophotometry. Oxygenated perfluorochemicals (30 ml/kg/h) significantly protected the gastric mucosa against both gross (lesion index 0.85 +/- 0.2 vs 2.23 +/- 0.31) and microscopic (lesion index 0.52 +/- 0.02 vs 2.04 +/- 0.03) injuries. This protection was associated with a significantly decreased acidification of the mucosa during shock (intramural pH 7.24 +/- 0.02 vs 6.97 +/- 0.02) and significantly increased oxygen saturation of the gastric mucosa (30 +/- 6 vs 5 +/- 2). These data indicate that topical oxygenated perfluorochemicals protect the gastric mucosa against mucosal damage provoked by hemorrhagic shock, and this protection seems to be mediated by an increased oxygen saturation of the gastric mucosa. Tonometry and reflectance spectrophotometry thus are able to predict the critical level of gastric mucosal ischemia.

Animals↗

PubMed1995

Impedance and wave reflection in arterial system: simulation with geometrically tapered T-tubes.

The aortic input impedance is simulated by an asymmetric T-tube model loaded with complex loads. A geometric tapering is incorporated to represent the vasculature, assuming a triangular distribution of the wave transmission paths. Parametric analyses using physiological data demonstrate that the predicted impedance and reflection coefficient spectrum (RCS) closely mimic the experimental data. The simulation also reveals several significant features. As diameter tapering can minimise the presence and influence of wave reflections, the impedance modulus stays relatively constant with two distinct minima. The frequency of first minimum of impedance modulus is evidence of the tube elasticity and load compliance in the lower extremity, and the frequency of second minimum is evidence of those in the upper extremity. The high-frequency portion of the impedance modulus is affected by the tube elasticity, but not by the load compliance. The impedance spectrum at higher frequencies shows no notable fluctuations corresponding to a decrease in blood or wall viscosity. Furthermore, the low-frequency range in RCS is dominated by the longer lower body tube, and the high-frequency range by the shorter upper body tube. This geometrically tapered T-tube is considered a more natural model for the description of the systemic arterial system.

Arteries↗

PubMed1989

Significance of lateral node dissection for advanced rectal carcinoma at or below the peritoneal reflection.

Two hundred thirty two patients with rectal cancer at or below the peritoneal reflection, who underwent extended systematic lymphadenectomy, especially lateral node dissection, were reviewed with respect to survival rate, degree of surgical technique, and mode of recurrence. On the basis of the extent of lateral node spread, two types of lateral node dissection were performed, consisting of preservation of internal iliac vessels (conventional) and en bloc excision of these vessels (extended). The overall disease-free five-year survival rate was 69.4 percent in all patients--75.8 percent for those who underwent extended resection and 67.4 percent for those who underwent conventional resection an excellent survival rate of 49 percent of patients with lateral node metastasis was obtained. The analysis was carried out with regard to prognostic factors such as number of node metastases, obesity index, mode of recurrence, etc. We would recommend that systemic lymphadenectomy with lateral node dissection be performed for advanced rectal cancer at or below the peritoneal reflection.

Adenocarcinoma↗

PubMed1987

Osteochondroma induced by reflection of the perichondrial ring in young rat radii.

In order to investigate the effects of reflection of the perichondrial ring in osteochondroma formation, the perichondrial rings of the epiphyseal growth plates in 42 young rat radii were turned to the metaphyseal periosteum by means of blunt dissection. Seven days after surgery a small nest of chondrocytes appeared on the metaphyseal-diaphyseal bone surface at the level of the tip of the reflected perichondrial ring. From the 9th to the 15th days the histological pattern of the osteochondroma was established. The osteochondroma was not connected with the hypertrophic cartilage of the growth plate. During the third and fourth weeks the osteochondroma began to regress with the disappearance of the cartilage nest. During the development of the lesion the bone grew normally and the growth plate migrated distally while the lesion remained at its initial site. The growth plate zone devoid of perichondrial ring was covered by fibrous connective tissue and no removal of the perichondrial ring occurred. These results suggest that the origin of this osteochondroma is the perichondrial ring cells whose polarity has been surgically changed.

Animals↗

PubMed1986

Cyclic AMP in gastric juice does not reflect histamine H2 receptor activity in Heidenhain pouch dog.

It is strongly believed that cAMP mediates histamine H2 receptor activity, but does not mediate gastrin and acetylcholine stimulation of gastric acid secretion. Therefore, cAMP production could be a marker of H2 receptor activity. Whether endogenous histamine mediates gastrin and/or acetylcholine stimulation, at least partially, remains to be elucidated. If cAMP in the gastric juice reflects H2 receptor activity, we can investigate whether endogenous histamine mediates gastrin and/or acetylcholine stimulation in vivo. In this study, we investigated whether cAMP in the gastric juice reflected histamine H2 receptor activity in the Heidenhain pouch dog in vivo using different kinds of inhibitors of gastric secretion. Our hypothesis was as follows: Upon betazole stimulation, cimetidine, an H2 receptor antagonist, should decrease cAMP output into the gastric juice, but omeprazole, an H+, K+-ATPase blocker, should not, because it blocks at a site more peripheral than the H2 receptor and the production of cAMP. Sixty minutes after betazole administration, 4.0 mumol/kg of cimetidine and 0.18 mumol/kg omeprazole were administered intravenously and they inhibited gastric juice volume to a similar degree, that is, 49.6% and 52.1%, respectively. However, omeprazole caused a greater decrease in cAMP output than cimetidine. Inhibition with 4 mumol/kg/h of cimetidine or 0.2 mumol/kg of omeprazole from the beginning of betazole stimulation also caused similar decreases in gastric juice volume, 66.6% and 60.6%, respectively. Both inhibitors decreased cAMP output into the gastric juice in a similar fashion in the first two 30 minute periods. These results do not agree with our hypothesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Use of reflectance in soft laser densitometry in scanning opaque electrophoregrams. A high-resolution technique.

The present report describes a new approach in soft laser scanning densitometry performed on opaque electrophoregrams. The method employs a light reflectance system instead of absorption, which is commonly used. The data of this preliminary study were obtained by directly scanning a photograph of an electrophoregram exhibiting viral proteins separated by SDS-PAGE. Comparison of the two methods clearly demonstrate that laser reflectance offers finer resolution than laser absorbance when opaque materials are scanned.

Densitometry↗

PubMed1981

Use of reflection contrast microscopy in the analysis of cellular motility.

Recognition and determination of the following activities of living cancer cells on glass substrates can be greatly facilitated by the use of reflection contrast microscopy: 1. stationary versus translocative motility, 2. migration over/under other cells, 3. actual locomotory activity of cells with a polarized shape usually associated with this type of motility. In addition, reflection contrast is useful for recognizing the presence of fibroblasts in cancer cell populations.

Animals↗