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PubMed1994

Stability determination of 3-bromo-2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)- 1,4-naphthoquinon-4-imine in ethanol by first-derivative spectrophotometry.

The degradation kinetics of a new potential tripanocidal and antibacterial agent, 3-bromo-2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4- naphthoquinon-4-imine (2), in 95% ethanol, was investigated between 35 and 50 degrees C under room-light and light-protected conditions. The decomposition product was isolated and identified as 2-hydroxy-N-(3,4-dimethyl- 5-isoxazolyl)-1,4-naphthoquinon-4-imine (1). A simple, rapid, and stability-indicating method for the determination of 2 in the presence of 1 using "zero crossing" first-derivative spectrophotometry is reported. The validity of this method was proved using synthetic mixtures of the intact drug with its decomposition product and by statistical analysis of the calibration data. Pseudo-first-order constants for the degradation reaction of 2, obtained from linear plots of the residual concentration logarithms vs time, the calculated activation parameters Ea, delta H not equal to, and delta S not equal to were similar under room-light and light-protected conditions. The in vitro antibacterial activity of 2 was also evaluated.

Anti-Bacterial Agents↗
PubMed1995

Determination of a quaternary mixture of vitamins B6, B1, and B12 and uridine 5'-triphosphate, by derivative spectrophotometry.

A new method for determining a quaternary mixture of vitamins B6, B1, and B12 and uridine 5'-triphosphate (UPT) using second-derivative spectrophotometry is described. Calibration graphs were linear up to 30 micrograms/mL of vitamin B6 at 307 nm (r = 0.9999) and vitamin B1 at 282.7 nm (r = 0.9997) and up to 35 micrograms/mL of vitamin B12 at 360.5-374 nm, peak-to-peak (r = 0.9999), and UTP at 261 nm (r = 1.0000). Detection limits at the p = 0.05 level of significance were calculated to be 0.20, 0.46, 0.22, and 0.20 microgram/mL for vitamins B6, B1, and B12 and UTP, respectively. An exhaustive statistical analysis of the experimental data was performed to confirm the validity of the method. The procedure does not require any separation step or solving of equations. The method was successfully applied for determining synthetic mixtures and commercial injections for these drugs.

Calibration↗
PubMed1991

Evaluation of BA1112 rhabdomyosarcoma oxygenation with microelectrodes, optical spectrophotometry, radiosensitivity, and magnetic resonance spectroscopy.

We studied tumor tissue oxygenation in the BA1112 rhabdomyosarcoma using micro-electrode pO2 measurements, optical spectrophotometry, analyses of cell survival after irradiation, and 31P magnetic resonance spectroscopy (MRS). Studies were carried out in WAG/Rij/Y rats breathing normoxic, hypoxic, and hyperoxic gas mixtures with and without iv administration of perfluorochemical. Significant changes in tissue oxygenation and metabolic status were found when pO2 values, optical measurements of hemoglobin saturation and cytochrome a, a3 reduction-oxidation, radiation cell survival determinations, and MRS measurements of phosphometabolite ratios were obtained in rats breathing different gas mixtures. Inhalation of 100% O2 caused increases in tumor pO2, hemoglobin saturation, cytochrome a, a3 oxidation, tumor radiosensitivity, and PCr/Pi, NTP/Pi, and PDE/Pi ratios. Such changes were augmented by pretreatment with iv perfluorochemicals. Inhalation of hypoxic gas mixtures resulted in reductions in the above parameters. These results indicate that tissue oxygenation can be manipulated reproducibly in the BA1112 rhabdomyosarcoma and suggest that 31P MRS can be used to monitor changes in tumor oxygenation in this model system.

Animals↗
PubMed2002

A thermodynamic characterization of the binding of thrombin inhibitors to human thrombin, combining biosensor technology, stopped-flow spectrophotometry, and microcalorimetry.

The binding of a series of low-molecular-mass, active-site-directed thrombin inhibitors (399-575 Da) to human alpha-thrombin was investigated by surface plasmon resonance technology (BIACORE), stopped-flow spectrophotometry, and isothermal titration microcalorimetry (ITC). The equilibrium constants K(D) (nM to microM range) at 25 degrees C obtained from the BIACORE analysis correlated well with the inhibition constants K(i) in a chromogenic inhibition assay. The interactions between thrombin and three potent inhibitors, melagatran, inogatran, and CH-248, were further investigated at temperatures between 278 and 310K. A one-to-one binding stoichiometry found with ITC was supported by BIACORE data. K(i) and K(D) values increased with the temperature, mainly due to higher values for dissociation rate constants. The changes in enthalpy, DeltaH, and entropy, DeltaS, determined from the linear van't Hoff plots (R coefficient > 0.99), were linearly correlated by chemical compensation. Both techniques indicated clear differences in DeltaS for the three inhibitors, with a strong correlation to the number of rotational bonds. Immobilization of thrombin increased the binding stability at higher temperature and reduced the DeltaH by 20 kJ mol(-1). DeltaH values obtained from the inhibition kinetics and BIACORE were thus not identical, but correlated well with ITC data obtained at 37 degrees C. The two thermodynamic techniques allowed further differentiation between compounds of similar affinity; furthermore, kinetic analysis, hence analysis of the transition state, is complementary to ITC. A direct BIACORE binding assay might be a useful alternative to more elaborate inhibition studies.

Binding Sites↗
PubMed1997

Synergistic interactions between neuropeptide and histamine on the capillary permeability in rat skin: evaluation by reflectance spectrophotometry.

Effects of neuropeptides on capillary permeability and their interactions with histamine (HIS) in rat skin were investigated. The capillary permeability was measured continuously by reflectance spectrophotometry after intravenous (iv) injection of Evans blue dye. The capillary permeability was increased dose-dependently by the intradermal injection of HIS (0.3-100 microg/site) and substance P (SP; 25-250 ng/site). Calcitonin gene-related peptide (80-800 ng/site) elicited a significant but less increase than did SP. Capsaicin (30 microg/site) also increased capillary permeability slightly but significantly, suggesting the release of endogenous neuropeptides. Both diphenhydramine (DPH; 3 mg/kg, iv) and cimetidine (CIM; 30 mg/kg, iv) reduced HIS-induced responses. DPH also reduced the SP-induced response significantly, but CIM did not. An SP antagonist, [D-Pro2, D-Trp7,9]-SP (1.3 mg/kg, iv), reduced not only SP- but also HIS-induced responses. Furthermore, the HIS-induced response was attenuated by pretreatment with epicutaneous capsaicin for 4 days, depleting endogenous SP. These results delineate the synergistic interactions between SP and HIS in rat skin and suggest the participation of neuropeptides in increasing capillary permeability.

Administration, Cutaneous↗
PubMed1992

Cerebral oxygenation state in chemically-induced seizures in the rat--study by near infrared spectrophotometry.

The hemoglobin oxygenation state and the redox state of Cyt.ox. in the rat brain during and after seizure induced by PTZ were measured by using near-infrared spectrophotometry. PTZ administration caused transient reduction of Cyt.ox. in the brain, which might be a trigger for the increase of CBF during seizure. In postictal phase, although BP remained high, Cyt.ox. was in the certain reduced state, which might be due to A-V shunt. Hypoxic loading during seizure caused more reduction of Cyt.ox. than under non-epileptic conditions, which meant that seizure even under mild hypoxic conditions could cause severe hypoxic brain damage.

Animals↗
PubMed1985

Near infrared spectrophotometry: potential role during increased intracranial pressure.

Two experiments were conducted to assess the feasibility of near infrared spectrophotometry (niroscopy) to directly monitor the effects of increased intracranial pressure on brain metabolism. Intracranial pressure (ICP) was increased in cats by subarachnoid infusion of a "mock" CSF solution. Cytochrome a,a3 redox state, oxyhemoglobin, deoxyhemoglobin and cerebral blood flow were non-invasively and continuously monitored by niroscopy. The results of both experiments indicated that untreated increases in ICP correlated with a reduction in cytochrome a,a3 redox state (p less than 0.01), a decrease in the quantity of oxyhemoglobin and cerebral blood flow (p less than 0.01), and an increase in deoxyhemoglobin. This study suggests that niroscopy has the potential for providing noninvasively and continuously data assessing brain metabolic activity. The excellent correlations obtained with simultaneous direct measurements of intracranial pressure make this an attractive method for eventual application to humans at risk for increased intracranial pressure. The value of niroscopy is even more evident in Exp. II where it can be seen that knowledge only of ICP would give the physician a false sense of security, whereas direct, non-invasive, continuous assessment of brain perfusion and oxygenation may well prove to be more appropriate parameters to monitor.

Animals↗
PubMed1987

Airborne and groundbased spectrophotometry of comet P/Halley from 5-13 micrometers.

Spectrophotometry from 5-10 micrometers (delta lambda/lambda approximately 0.02) of comet Halley was obtained from the Kuiper Airborne Observatory on 1985 December 12.1 and 1986 April 8.6 and 10.5, UT. 8-13 micrometers data were obtained on 17.2 December 1985 from the Nickel Telescope at Lick Observatory. The spectra show a strong broad emission band at 10 micrometers and a weak feature at 6.8 micrometers. We do not confirm the strong 7.5 micrometers emission feature observed by the Vega 1 spacecraft. The 10 micrometers band, identified with silicate materials, has substructure indicative of crystalline material. The band can be fitted by combining spectra data from a sample of interplanetary dust particles. The primary component of the silicate emission is due to olivine. The 6.8 micrometers emission feature can be due either to carbonates or the C-H deformation mode in organic molecules. The lack of other emission bands is used to place limits on the types of organic molecules responsible for the emission observed by others at 3.4 micrometers. Color temperatures significantly higher than the equilibrium blackbody temperature indicate that small particles are abundant in the coma. Significant spatial and temporal variations in the spectrum have been observed and show trends similar to those observed by the spacecraft and from the ground. Temporal variability of the silicate emission relative to the 5-8 micrometers continuum suggests that there are at least two physically separated components of the dust.

Astronomical Phenomena↗
PubMed1987

Intact organ spectrophotometry and single-photon counting.

In toxicology, it is of interest not only to assess enzyme levels and capacities for potential fluxes, but it is also useful to develop methods for determining actual concentrations and fluxes in the intact cell and organ. To this end, several noninvasive techniques have been developed over the years. Our interest has been largely in photometric techniques. Transmission spectrophotometry through solid organs permits monitoring of the cytochromes of the mitochondrial respiratory chain and cytochrome P-450 as well as other pigments of biological interest. Furthermore, the steady state level of catalase Compound I in liver provides information on rates of H2O2 production. These are in the nM to microM concentration range. More recently, the monitoring of photoemission from intact organs has been useful in toxicological problems. The major photoemissive species, singlet molecular oxygen and excited carbonyls, can now be monitored with good signal/noise ratio. Redox cycling of quinones and the generation of photoemissive species were studied in menadione metabolism. Inhibition of phase II led to a significant increase in the steady state level of singlet oxygen, as did the inhibition of two-electron reduction by using the inhibitor dicoumarol for DT diaphorase. Conversely, the induction of DT diaphorase by pretreatment with BHA protected by decreasing the level of reactive oxygen species.

Radiation↗
PubMed1982

Alternative method for quantitative enzyme histochemistry of muscle fibers. Application of photographic densitometry combined with atomic absorption spectrophotometry.

The present study examines the use of photographic densitometry combined with atomic absorption spectrophotometry for the quantitation of enzyme activities (SDH and ATPase) in fresh frozen sections of rat tibialis anterior muscles. The technique eliminates some difficulties which are inherent in other methods. The reliability of the technique was found to be in the 98% range; the results were precise for all samples studied. The use of SDH to separate muscle fibers into "types" was found to be totally inaccurate since a full spectrum of activities was observed. ATPase activities could separate easily into two groups, but a continuum of ATPase activities was observed in the fast-twitch fibers. The simultaneous use of both enzymes was capable of separating the FG, FOG and SO fibers; however, variation within a single type was considerable and a great deal of information was lost when using any classification system. The continuum of SDH activities indicates the motor units are arranged as a spectrum of fatigue-resistant contractile units. The range of ATPase activities observed is comparable to ranges of motor unit contraction times emphasizing the importance of this enzyme in the regulation of contraction speed.

Adenosine Triphosphatases↗
PubMed1985

Fibre-optic spectrophotometry of immature bovine skeletal muscles and the cellular distribution of myoglobin and succinate dehydrogenase.

Samples of diaphragm and pectoralis profundus were taken from nine calves with a range of blood haemoglobin levels of 4 to 8.5 g/100 ml. In both muscles, fibres with strong succinate dehydrogenase activity contained myoglobin, but in the pectoralis there were many fibres with strong alkaline ATPase activity and weak succinate dehydrogenase activity that had low or undetected levels of myoglobin. The whole cross-sectional area of individual fibres was scanned to map the distribution of succinate dehydrogenase activity. Among fibres with similar levels of ATPase activity, those from the diaphragm had greater succinate dehydrogenase activity than those from the pectoralis. Subsarcolemmal succinate dehydrogenase activity was greater than the axial succinate dehydrogenase activity, and radial gradients of succinate dehydrogenase activity were steepest in the diaphragm. For pectoralis fibres with weak ATPase, the mean and the axial succinate dehydrogenase activities were correlated with blood haemoglobin levels (r = 0.62 and r = 0.61, respectively; P less than 0.05 with a Student's t-test). Muscle colour was measured directly by fibre-optic spectrophotometry and correlations of absorbance with succinate dehydrogenase activity were obtained. Absorbance at 620 nm 24 h post-mortem was correlated with succinate dehydrogenase activity in pectoralis fibres with weak ATPase (r = 0.81; P less than 0.005).

Adenosine Triphosphatases↗
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↗
PubMed1994

Effects of repeated indomethacin administration on cerebral oxygenation and haemodynamics in preterm infants: combined near infrared spectrophotometry and Doppler ultrasound study.

The objectives of this study were to evaluate the effect of repeated indomethacin administration on cerebral oxygenation in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables. Fourteen preterm infants with patent ductus arteriosus were studied during three subsequent indomethacin bolus administrations with intervals of 12 and 24 h. Changes in concentration of oxyhaemoglobin (cO2Hb), deoxyhaemoglobin (cHHb) and oxidized cytochrome aa3 (cCyt.aa3) in cerebral tissue and changes in cerebral blood volume (CBV) were measured by near infrared spectrophotometry; changes in mean CBFV in the internal carotid artery were measured by pulsed Doppler ultrasound. Simultaneously heart rate, transcutaneous pO2 and pCO2, arterial O2 saturation and blood pressure were measured. All variables were continuously recorded until 60 min after indomethacin administration. Within 5 min after each indomethacin administration, significant decreases in CBFV, CBV and cO2Hb and cCyt.aa3 were observed which persisted for at least 60 min, while cHHb increased or did not change at all. There were no changes in the other variables recorded. These data demonstrate that indomethacin administration is accompanied by a reduction in cerebral tissue oxygenation due to decreased cerebral blood flow. Therefore, low arterial oxygen content, either caused by low arterial O2 saturation or by low haemoglobin concentration, may be a contraindication for indomethacin treatment in preterm infants.

Blood Flow Velocity↗
PubMed1995

Colonic mucosal hemodynamics and tissue oxygenation in patients with ulcerative colitis: investigation by organ reflectance spectrophotometry.

Colonic mucosal hemodynamics were investigated at the rectosigmoidal region of the colon in 46 patients with ulcerative colitis and in 18 normal subjects by organ reflectance spectrophotometry under colonoscopy. The value for the index of mucosal hemoglobin concentration (IHb) was significantly higher, and value for the index of mucosal hemoglobin oxygen saturation (ISO2) was significantly lower in patients with active ulcerative colitis than values in the normal controls or in patients with inactive ulcerative colitis. The results indicate mucosal congestion and hypoxemia in patients with active ulcerative colitis. The changes in IHb and ISO2 correlated well with the severity of ulcerative colitis scored by endoscopic findings and with the number of infiltrating inflammatory cells in the mucosa analyzed histologically in biopsy samples. In conclusion, the colonic mucosal microcirculation in patients with active ulcerative colitis was disturbed and showed congestion and hypoxemia. The analysis of hemodynamic changes may be helpful for assessing the activity of ulcerative colitis.

Adult↗
PubMed1996

Optimising the methodology of calculating the cerebral blood flow of newborn infants from near infra-red spectrophotometry data.

Cerebral blood flow can be measured in neonates by near infra-red spectrophotometry. The tracer is oxyhaemoglobin. The purpose of the study is to compare the test-retest variability of two previously proposed methods (UCH and COP) of analysis, and to investigate the influence of sampling rates, smoothing and integration periods. Under clinical conditions good measurements are often difficult to obtain. Therefore, a second goal is to find ways of determining the quality of individual measurements. 380 cerebral blood flow measurements from 69 infants are analysed. The data set is optimised statistically for the lowest test-retest variability and the following results are obtained. The test-retest variability of measurements at 2 s sampling time data is considerably worse than at 0.5 s sampling time. Smoothing does not change the test retest variability. A 6 s integration period gives higher values and higher test-retest variability than an 8 s integration period. By applying the suggested criteria, a test-retest variability of 17% is achieved, if 50% of the measurements are rejected. The mean cerebral blood flow is 12.2 ml (100 g)-1 min-1 for the UCH method and 9.7 ml [corrected] (100 g)-1 min-1 for the COP method. The test-retest variability of both methods is comparable for 0.5 s sampling time. For 2 s sampling time the method proposed by Skov et al. is significantly better. These test retest variabilities represent maximum values, part of the observed variability may be due to physiological changes of unknown magnitude.

Cerebrovascular Circulation↗
PubMed1994

Non-invasive monitoring of brain oxygen sufficiency on cardiopulmonary bypass patients by near-infra-red laser spectrophotometry.

A new portable high-performance apparatus for near-infra-red (NIR) laser spectrophotometry was developed to monitor the oxygenation state in the human brain. Three different wavelengths of 780, 805 and 830 nm of the NIR light illuminated the head using a fibre-optic bundle, and the transmitted or reflected light was detected by a photodiode placed on the forehead. The oxygenated Hb (oxy Hb), deoxygenated Hb (deoxy Hb) content and the Hb (blood) volume changes in the brain were continuously monitored in cardiopulmonary bypass (CPB) patients in the reflectance mode. In hypothermic CPB with selective brain perfusion, the brain bypass flow rates of 0.5 L min-1 at 24-25 degrees C and 0.3 L min-1 at 21-22 degrees C were confirmed as the safe lower limits by our NIR monitoring. During deep hypothermic circulatory arrest, the brain oxy Hb and blood volume decreased significantly. The result indicates that brain Hb oxygenation decreases significantly during circulatory arrest. In the adult patients group, during moderate hypothermic CPB, the brain blood oxygenation level was maintained roughly constant at mean arterial perfusion pressure of over 60 mm Hg, whereas below 50-55 mmHg a progressive decline in the brain Hb oxygenation was observed. These findings led us to conclude that non-invasive monitoring of brain oxygenation using NIR light can provide valuable data at the bed-side regarding tissue metabolism, and it can allow for the proper management of critical patients.

Adolescent↗
PubMed1998

Direct determination of selenium in human blood plasma and seminal plasma by graphite furnace atomic absorption spectrophotometry and clinical application.

Direct determination of selenium (Se) in body fluids by graphite furnace atomic absorption spectrophotometry (GFAAS) may suffer from problems like severe background, matrix effects, preatomization losses, and spectral interferences. In this study we evaluate critically the influence on the accuracy of the direct determination of Se in blood plasma and seminal plasma by GFAAS, and propose a simple, rapid, and accurate method, suitable for routine clinical analysis. The method for blood plasma is mainly based on studies by the use of matched matrix and a Pd-Ni modifier, but for seminal plasma only a Pd modifier is required. The method developed was also applied to study the Se distribution in plasma protein fractions of patients with hepatocellular carcinoma. The Se in plasma of patients was significantly lower than that of the controls. The distribution pattern of Se in blood plasma fractions of patients was also different from that of the controls.

Adult↗
PubMed1996

Determination of zinc fractions in human blood and seminal plasma by ultrafiltration and atomic absorption spectrophotometry.

A simple and reliable method is described which combines ultrafiltration technique with atomic absorption spectrophotometry to determine the Zn fractions in human blood plasma and seminal plasma. Ultrafiltrable, loosely bound, and firmly bound Zn can be measured using this method in the presence or absence of ethylenediaminetetraacetic acid (EDTA). The YMT membranes for the ultrafiltration must be rinsed thoroughly before use. In contrast to Zn in blood plasma, a large part of Zn in the seminal plasma was found to be ultrafiltrable. This method can be applied to study the physiologically active part of Zn in body fluids related to various disease states.

Adult↗