Cerebral cytochrome oxidase monitoring by near infrared spectroscopy during selective cerebral perfusion

To evaluate selective cerebral perfusion (SCP) for brain protection, the redox state of cytochrome oxidase (Cyt. aa3) in brain tissue were studied in 27 patients with thoracic aortic repair. The redox state of Cyt. aa3 was monitored by near infrared spectroscopy (NIRS) (OM-110, Shimazu). There were no significant changes in the Cyt. aa3 redox state in 13 (Group I), the oxidation state of Cyt. aa3 decreased then recovered to control levels in 12 (Group II), and the oxidation state decreased but did not recover in 2 patients (Group III). Postoperative cerebral damage was observed in 5 patients; blindness occurred in one patient in Group I (8.3%), 2 patients developed hemiplegia in Group II (15.4%), and the 2 patients in Group III failed to reawaken (100%). The incidence of cerebral damage was significantly higher in Group III than in Groups I and II (p < 0.05). We conclude that monitoring the redox state of Cyt. aa3 using NIRS is useful in predicting postoperative cerebral damage. However, it is necessary to increase the number of measurement sites since NIRS can reflect the state in only a small area of the brain.     

Quality control in manufacturing process by near infrared spectroscopy

The combination of a pattern recognition technique with near infrared spectroscopy (NIR) to determine the conformity of a pharmaceutical mixture can be used in the routine checking of a pharmaceutical product. All the chemical and physical characteristics of the product that influence the NIR spectrum affect the qualification. The qualification is used to determine several deviations in the process: moisture, particle size and non-homogeneity. This work presents a method for the qualification analysis of a pharmaceutical mixture using the standard software of the instrument and a new program (DISPLOT). This program allows the acquisition of the plot of the scaled distances with its sign vs the wavelength.     

Changes in tissue oxyhaemoglobin concentration measured using multichannel near infrared spectroscopy during internal carotid angiography

OBJECTIVE: To develop an in vivo model for testing spatially resolved spectroscopy and quantified near infrared spectroscopy (NIRS) cerebral blood flow measurements. METHOD: Multiple detector NIRS has been used to study changes in tissue oxyhaemoglobin (O2Hb) concentration during selective internal carotid angiography. A significant reduction in O2Hb occurred in tissue interrogated by detectors situated between 0.7 and 4.1 cm from the NIRS light source. RESULTS: The time course of O2Hb concentration change was consistent with displacement of oxygenated blood by the radiocontrast medium from vascular beds of differing flow and NIR light attenuation. Increasing changes in O2Hb concentration per unit photon path length--predicted to occur at greater emitter-detector separations if those changes had occurred predominantly in cerebral tissue--were found in the first four seconds after injection of radiocontrast medium. However, later changes (6-10 s) were larger and were not proportional to emitter-detector separation. CONCLUSION: The findings indicate that simple assumptions regarding the distribution of the internal carotid artery blood supply to cerebral and extracerebral tissues, the photon path length through those tissues, and their relative contributions to attenuation of NIR light may not be justified.     

Correlation of near infrared spectroscopy cerebral blood flow estimations and microsphere quantitations in newborn piglets

We compared cerebral blood flow (CBF) estimated using transmission mode near infrared spectroscopy (NIRS) and a modification of the Fick principle with CBF quantitations by radioactive microspheres (MSs) in newborn piglets. Thirteen piglets were studied during steady state, ischemia, and during two reflow periods. NIRS and MS flows were not significantly different during any measurement period. NIRS flows were compared to total brain blood flows and to regional brain blood flows quantitated with MSs and correlated best with temporal cortical flows. Linear regression analysis of the NIRS flows plotted against MS-quantitated temporal cortical flows showed r = 0.71. Thus, CBFs obtained with NIRS were not significantly different from, showed the same directional changes, and correlated acceptably with flows quantitated by MSs.     

Age-related changes in the electrophysiological response to visual stimulus novelty: a topographical approach

The relationship of task relevance and stimulus probability to P300 morphology, latency and distribution was assessed. Eight year olds and adults completed visual oddball tasks of recognition memory with frequent non-target (60%), infrequent target (20%), and infrequent novel (20%) stimuli. Stimuli consisted of 2 female faces posing neutral expressions, and 40 trial unique novel photographs depicting scenes, animals, objects or abstract patterns. Event-related potentials were recorded from 17 electrodes over frontal, central and parietal scalp, including lateral temporal sites. All stimuli elicited P300 responses at parietal electrodes, with the largest responses to the target stimuli (relevant and infrequent). The P300 responses of adults and children were morphologically dissimilar, with children showing broader peaks and latency shifts across electrodes. In addition, the eight year olds displayed a frontal negativity to novel stimuli which was absent in the responses of adult participants. Results suggest that different anatomical or functional circuitry may be involved in the processing of novelty for adults as compared to eight year olds.     

Near infrared spectroscopy detects cerebral ischemia during hypotension in piglets

OBJECTIVE: To determine if platelet angiotensin II binding density during the second or third trimester of pregnancy can be used as a marker for early detection of women who will develop preeclampsia. METHODS: We collected blood samples from 412 nulliparous pregnant women during their second or third trimesters. They were classified in four groups after delivery: normotensive (n=297), transient hypertensive (n=54), preeclamptic (n=39), and chronic hypertensive (n=22). We also studied 35 nonpregnant women and 122 women in the peripartum period. The binding capacity of platelet angiotensin II receptors was analyzed in each patient. RESULTS: In normotensive pregnancies, there was a significant decrease in mean (+/-standard error of the mean [SEM]) platelet binding in the second trimester (1.6+/-0.2 fmol/10(9) cells) compared with nonpregnant women (3.3+/-0.7 fmol/10[9] cells). No statistical differences were observed in the mean (+/-SEM) number of platelet angiotensin II binding sites between the groups studied in the third trimester (normal: 1.7+/-0.1 fmol/10(9) cells; transient hypertensive: 2.3+/-0.4 fmol/10(9) cells; preeclamptic: 1.6+/-0.4 fmol/10(9) cells, and chronic hypertensive: 1.6+/-0.6 fmol/10(9) cells), nor were any significant differences found in second-trimester values. At cutoff levels providing identical sensitivities, angiotensin II binding showed significantly lower positive predictive values than mean arterial pressure (P < .05). With this study's sample size, we could have demonstrated an improvement in positive predictive values of 20% with a statistical power (1-beta) of 90%. CONCLUSION: The measurement of platelet angiotensin II receptor density cannot be recommended for the early detection of preeclampsia.     

Conformation of phosphatidylserine in bilayers as studied by Fourier transform infrared spectroscopy

The 13C labeled lipid 1[1'-13C]DPPS-NH4+ and its metal salts were used to unambiguously assign all carbonyl vibrations in the infrared spectrum of phosphatidylserines. It is shown that the C=O stretching band at 1741 cm-1 of phosphatidylserines previously assigned to the sn-1 C = O vibration contains contributions from both the sn-1 and the sn-2 carbonyls. The C=O stretching band at frequencies between 1715 and 1730 cm-1 previously assigned to the sn-2 C=O vibration also contains contributions from both carbonyl groups. The frequency dependence observed with the ester carbonyls primarily reflects hydrogen bonding and the polarity of the immediate vicinity. Conformational changes are accounted for in terms of frequency shifts if the conformational change involves the disposition of the C=O groups and in turn the hydrogen bonding properties. The infrared spectra of phospholipids dispersed in aqueous medium in the liquid crystalline state are inconsistent with a simple phospholipid conformation, e.g., with a conformation as found in the single-crystal structure of 1,2-dimyristoyl-sn-phosphatidylcholine and 1,2-dilauroyl-rac-phosphatidylethanolamine. The spectra support the hypothesis proposed earlier (Hauser et al., Biochemistry, 1988) on the basis of existing single-crystal phospholipid structures and NMR evidence. The hypothesis states that several conformations are present in liquid crystalline phospholipid dispersions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regional cerebral blood flow measured by 99mTc-HMPAO SPECT differs in subgroups of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous entity. Identifying AD subtypes might have impact in patients' response to different treatment strategies. We designed a study to examine regional cerebral blood flow (rCBF) in AD subtypes. To identify AD subtypes, we performed a cluster analysis including performance on memory, language, visuospatial, praxic, and executive functions. The rCBF measured by 99mTc-HMPAO SPECT was referred to the cerebellum. We examined 35 patients fulfilling the NINCDS-ADRDA criteria of probable AD and 13 age and sex-matched healthy cognitively intact controls. AD patients were at the early stage of the disease, their mean Mini-Mental Status (MMS) score (S.D.) was 22.5 (3.6). The cluster analysis revealed two AD subgroups: AD1 (N = 12) and AD2 (N = 23). The subgroups did not differ in age, sex, or global clinical severity as assessed by MMS and Brief Cognitive Rating Scale (BCRS). Both subgroups had equally impaired memory. The AD2 group was inferior to the AD1 group on verbal, visuospatial, praxic, and executive functions. The AD1 group showed reduced rCBF ratios in the temporal and parietal cortices and the amygdala compared to controls. The AD2 group differed from controls in the rCBF ratios of frontal, temporal, parietal, occipital, basal ganglia, and amygdaloid regions bilateral and from AD1 in the rCBF ratios of frontal and temporal cortices. In AD patients, the rCBF ratios did not correlate with MMS or BCRS scores. In contrast, several significant correlations were found between decreases rCBF ratios and impairment of memory and other cognitive functions. In conclusion, a cluster analysis on neuropsychological test performance identified two AD subgroups that differed on the neuropsychological profile and on the rCBF in spite of similar global clinical severity.     

The measurement of peripheral venous oxyhemoglobin saturation in newborn infants by near infrared spectroscopy with venous occlusion

A novel, noninvasive method for measuring peripheral venous oxygen saturation (Svo2) in newborn infants using near infrared spectroscopy (NIRS) with venous occlusion is described, along with a comparison with co-oximetry of peripheral venous blood. Peripheral Svo2 was measured in 16 newborn infants by NIRS with venous occlusion, and the results were compared with those obtained by co-oximetry of blood from a forearm vein. There was a significant correlation between the two measurements (r = 0.85, p < 0.0001) and close agreement between the two techniques (mean difference (co-oximeter-NIRS) 6%, limits of agreement-5.1% to 17.1%). Three different methods for analysis of the NIRS data were examined to determine which period during the venous occlusion provided the most accurate measurement. The agreement was the same for all methods of analysis.     

Developmental changes in the effectiveness of stimulus intensity on infant visual attention.

Tested the hypothesis that the effectiveness of stimulus intensity declines with age. Stimulus intensity was manipulated by varying the size of pairs of bull's-eye and striped patterns. 50 infants from 6 wks to 24 wks of age were shown 18 pairs of stimuli in which there were 5 different sizes of each pattern. Infants 10 wks and younger responded on the basis of size, looking more at the larger sizes. The older Ss looked more at the bull's-eye regardless of its size or the size of the striped pattern paired with it. Possible mechanisms underlying this shift are discussed, and the concept of stimulus intensity is considered. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of key sources of variability in the measurement of pharmaceutical drug products by near infrared reflectance spectroscopy

Potential sources of variability in the measurement of solid oral drug products by near infrared reflectance spectroscopy were evaluated with statistical experimental design. Spectra were collected for two different tablet types according to the data collection and treatment parameters defined by the experimental design. Each tablet had three different dose-levels. Libraries were constructed using second-derivative spectra. Key figures-of-merit generated during internal and external library validation were used to calculate which parameters most strongly influence the library performance for dose-level discrimination. These responses and their corresponding experimental conditions were evaluated with the screening model in the JMP program. Segment value used for the second-derivative calculation was an an influential factor and had a complex effect. Orientation on the sampling platform also had an influential effect for embossed tablets. Collection of spectra over fewer days decreased variability within the library. More frequent reference spectrum collection improved the performance of libraries to a small degree. A larger sample population increased the range of spectral variability within a dose-level but apparently not the overall performance of the library. The number of scans averaged per spectrum was not an influential factor in this study. These results are summarized and used to recommend an approach to dose-level discrimination.     

Regional variations in cerebral proton spectroscopy in patients with chronic hepatic encephalopathy

Regional variations in proton magnetic resonance spectroscopy (MRS) were assessed in 26 patients and 14 healthy volunteers using a two dimensional chemical shift imaging technique. Patients were classified as being neuropsychiatrically unimpaired, or as having subclinical or overt chronic hepatic encephalopathy (CHE). Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate (NAA) relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr were observed in the patient population, which correlated with the severity of CHE. There were significant regional variations in these metabolite ratios with the mean Cho/Cr lowest in the occipital cortex and the mean Glx/Cr highest in the basal ganglia. NAA/Cr remained relatively constant in all areas of the brain analysed. The regional variation in the metabolite ratios suggests that spectral information from more than one voxel may be useful in the assessment of patients with CHE.     

Protein structure in KBr pellets by infrared spectroscopy

The S14 ribosomal protein from the thermophilic organism Thermus thermophilus, which contains a zinc-finger-like motif, namely -C-X2-C-X12-C-X2-C- [Tsiboli, P. & Choli, T. (1995) Biol. Chem. Hoppe-Seyler 376, 127-130], has been overproduced, purified and investigated for its zinc content. According to atomic absorption experiments, the protein contains zinc at a molar ratio of one. Denaturation experiments with simultaneous use of denaturing and chelating agents (guanidine hydrochloride and EDTA), as well as renaturation experiments, have shown both that Zn is strongly bound to the protein and with 1:1 Zn/protein stoicheiometry. These findings provide very strong evidence in support of the participation of the zinc-finger motif and the Zn in the formation of a zinc-finger domain.     

Microstructural changes as a result of temperature gradients in the Al-Al3Ni eutectic

The microstructural changes accompanying exposure of the Al-Al₃Ni eutectic to temperature gradients have been studied. It is observed that at high temperatures microstructural coarsening, as measured by transverse fiber density, is less during gradient as opposed to isothermal exposure. The converse holds to a much less degree at lower temperatures. The differences between the fiber densities during gradient and isothermal exposure are directly related to the temperature, the temperature gradient, and the time of exposure. Microchemical analysis was performed in an attempt to determine if there was redistribution of Al₃Ni along the temperature gradient during such exposure. Experimental results were not entirely conclusive, but do suggest that the Al₃Ni content is higher at the hot and cold ends in comparison to that in the center of the specimen. Numerical analysis was employed to test several theories relating to particle migration during elevated temperature exposure. It was found that a model of fiber migration controlled by diffusion along the fiber-matrix interfaces could account well for the observed values of fiber density and apparent redistribution of Al₃Ni along the specimen length. Moreover, if reasonable values of the heat of transport of Ni in aluminum are assumed, the diffusion coefficient necessary to predict observed results agrees well with recently determined interfacial diffusion coefficients in a comparable (Al-CuAl₂) system.     

Blood flow velocity changes in the middle cerebral artery induced by processing of hierarchical visual stimuli

Transcranial Doppler ultrasound was used to measure mean flow velocities in both middle cerebral arteries while 16 young subjects performed a visual task involving the processing of hierarchically structured stimuli. Specifically, large (global) letters composed of smaller (local) letters were presented, with the subjects' task being to attend either to the local or to the global level and press a button whenever a target on the designated level occurred. Each run was comprised of a 35-sec period of passive stimulation, followed by 65 sec of active task. A highly significant increase of blood flow was detected upon initiation of the active task, which was clearly present after ca. 4 sec. The flow velocity reached a maximum after 20 sec and remained stable for the remainder of the active condition. No hemispheric differences with respect to global or local conditions were observed.     

Regional cerebral blood flow changes in chronic alcoholic patients induced by naltrexone challenge during detoxification

A follow-up study was performed with the aim to evaluate all individuals surgically treated by the uvulopalatopharyngoplasty (UPPP) or laser uvulopalatoplasty (LUPP) method from a whole county in Sweden, 1-8 years after surgery, by assessing snoring occurrence and daytime sleepiness, as experienced by the patients and their cohabitants. Questionnaires were mailed to all operated people (n = 457) and were returned by 91% (346 men, 69 women) preoperatively diagnosed as habitual snorers (n = 255), cases of obstructive sleep apnea syndrome (n = 110) and unspecified snorers (n = 48). In addition 345 bedpartners participated. For outcome of surgery, no significant differences in diagnoses or sex were found. Improvement in snoring occurrence was reported by 89.6% of the patients, confirmed by 92% of the cohabitants (r = 0.84, p < 0.01). The remaining snoring occurrence was significantly dependent on the surgical method and the time after operation. Excessive daytime sleepiness (EDS) was experienced by 73.3% of the patients compared to 67% reported by the cohabitants. Of 415 patients operated on, 18% were free from snoring and 25% were free from EDS. Individuals with a shorter time since surgery reported less snoring. The UPPP method gave a significantly better result than LUPP for the symptom 'snoring'.