Functional optical topography analysis using statistical parametric mapping (SPM) methodology with and without physiological confounds.

Functional optical topography (OT) measures the changes in oxygenated and deoxygenated hemoglobin (HbO(2), HHb) across multiple brain sites which occur in response to neuronal activation of the cerebral cortex. However, identification of areas of cortical activation is a complex task due to intrinsic physiological noise and systemic interference and careful statistical analysis is therefore required. A total of 10 young healthy adults were studied. The activation paradigm comprised of anagrams followed by finger tapping. 12 channels of the OT system were positioned over the frontal cortex and 12 channels over the motor cortex while the systemic physiology (mean blood pressure (MBP), heart rate (HR), scalp flux) was simultaneously monitored. Analysis was done using the functional Optical Signal Analysis (fOSA) software and Statistical Parametric Mapping (SPM), where we utilized two approaches: (i) using only HbO(2) as a regressor in the general linear model (GLM) and (ii) using all of the explanatory variables (HbO(2), MBP, HR and scalp flux) as regressors. Group analysis using SPM showed significant correlation in a large number of OT channels between HbO(2) and systemic regressors; however no differences in activation areas were seen between the two approaches.

Inorganic pyrophosphate: energy source for sulfate-reducing bacteria of the genus desulfotomaculum.

Sulfate-reducing bacteria belonging to the genus Desulfotomaculum utilized inorganic pyrophosphate as a source of energy for growth in the presence of fixed carbon (acetate and yeast extract) and sulfate. Pyrophosphate does not support the growth of Desulfovibrio under the same growth conditions. Over a limited range of concentrations, growth is proportional to pyrophosphate, and extracts of bacteria grown on pyrophosphate medium have enzymatic activities similar to extracts prepared from bacteria grown on medium containing lactate plus sulfate. The variety of cell types observed in crude anaerobic pyrophosphate-enrichment cultures from a marine environment suggests that this unique type of energy metabolism is not restricted to the sulfate-reducing bacteria of the genus Desulfotomaculum.

Development of a dynamic test phantom for optical topography.

Optical topography (OT) is a near infrared spectroscopy (NIRS) technique that provides spatial maps of haemodynamic and oxygenation changes. When developing, testing and calibrating OT systems it is often necessary to use tissue simulating phantoms that are capable of providing realistic changes in attenuation properties. We present a novel dynamic tissue phantom that enables spatially and temporally varying tissue properties to be reproduced in a controlled manner. This new dynamic test phantom consists of a modified liquid crystal display (LCD) (enabling flexible and rapid changes in attenuation across different regions of the phantom) sandwiched between two layers of tissue simulating epoxy resin (providing static and homogeneous optical absorption and scattering). By activating different pixels in the liquid crystal display it is possible to produce highly localised and dynamic changes in attenuation which can be used to simulate the changes associated with the cerebral haemodynamic response to functional activation. The reproducibility of the dynamic phantom will be described with examples of its use with an OT system.

False positives in functional near-infrared topography.

Functional cranial near-infrared spectroscopy (NIRS) has been widely used to investigate the haemodynamic changes which occur in response to functional activation. The technique exploits the different absorption spectra of oxy- and deoxy-haemoglobin ([HbO2] [HHb]) in the near-infrared region to measure the changes in oxygenation and haemodynamics in the cortical tissue. The aim of this study was to use an optical topography system to produce topographic maps of the haemodynamic response of both frontal cortex (FC) and motor cortex (MC) during anagram solving while simultaneously monitoring the systemic physiology (mean blood pressure, heart rate, scalp flux). A total of 22 young healthy adults were studied. The activation paradigm comprised of 4-, 6- and 8- letter anagrams. 12 channels of the optical topography system were positioned over the FC and 12 channels over the MC. During the task 12 subjects demonstrated a significant change in at least one systemic variable (p < or = 0.05). Statistical analysis of task-related changes in [HbO2] and [HHb], based on a Student's t-test was insufficient to distinguish between cortical haemodynamic activation and systemic interference. This lead to false positive haemodynamic maps of activation. It is therefore necessary to use statistical testing that incorporates the systemic changes that occur during brain activation.

Functional optical signal analysis: a software tool for near-infrared spectroscopy data processing incorporating statistical parametric mapping.

Optical topography (OT) relies on the near infrared spectroscopy (NIRS) technique to provide noninvasively a spatial map of functional brain activity. OT has advantages over conventional fMRI in terms of its simple approach to measuring the hemodynamic response, its ability to distinguish between changes in oxy- and deoxy-hemoglobin and the range of human participants that can be readily investigated. We offer a new software tool, functional optical signal analysis (fOSA), for analyzing the spatially resolved optical signals that provides statistical inference capabilities about the distribution of brain activity in space and time and by experimental condition. It does this by mapping the signal into a standard functional neuroimaging analysis software, statistical parametric mapping (SPM), and forms, in effect, a new SPM toolbox specifically designed for NIRS in an OT configuration. The validity of the program has been tested using synthetic data, and its applicability is demonstrated with experimental data.

Discriminant analysis of trace element distribution in normal and malignant human tissues.

Discriminant analysis of 16 trace element levels measured by ultramicro energy dispersive X-ray fluorescence in malignant and histologically normal human breast, colon, and lung tissues is shown to be a potentially valuable methodology for making malignant-normal and tissue-type classifications. Linear composites of trace elements producing optimal malignant-normal discriminations are found to differ with respect to the number and identity of elements included in the composite for breast, colon, and lung tissues. Nine-, 10-, and 11-element discriminant functions produced overall classification accuracies of 98% for breast, 100% for colon, and 100% for lung tissues, respectively. Elements found to be most important in distinguishing between malignant and normal tissues are Ca, Rb, and Zn in breast, Ca, Zn, and Fe in colon, and Fe, Mn, and Cu in lung samples. Three-group discriminations between breast, colon, and lung tissues were 85% accurate using trace element levels in paired malignant-normal tissues and 91% accurate using trace element levels in tumor tissues only.

Comparison between concentrations of trace elements in normal and neoplastic human breast tissue.

Histologically normal and neoplastic human breast tissues obtained from 25 patients at the time of mastectomy were homogenized (200 mg/ml) in distilled water and 5-microliter aliquots dried on Formvar films for trace element analysis by energy-dispersive X-ray fluorescence. The elements measured were calcium, vanadium, copper, zinc, iron, chromium, manganese, nickel, selenium, molybdenum, bromine, rubidium, strontium, mercury, arsenic, and lead. In general, significantly large increases (p less than 0.001) in calcium, vanadium, copper, zinc, selenium, and rubidium were found in breast tumors, with a less significant increase (p less than 0.05) for nickel. When a comparison was made between histologically normal and neoplastic tissues from the same individual, zinc and rubidium were found to be consistently higher in the tumor, whereas calcium, copper, and vanadium levels varied from normal to high. In no instance were the tissue changes in calcium, copper, zinc, or rubidium reflected in the blood levels, which were within normal limits. The distribution of calcium, copper, and zinc in urine varied among individuals with primary tumors; however, rubidium levels tended to be consistently elevated. An attempt is being made to correlate these various differences with the extent of the primary disease at the time of surgery, the postoperative tumor-free interval, and subsequent therapy.

Structure-function relationships among the nickel-containing hydrogenases.

The enzymology of the heterodimeric (NiFe) and (NiFeSe) hydrogenases, the monomeric nickel-containing hydrogenases plus the multimeric F420-(NiFe) and NAD(+)-(NiFe) hydrogenases are summarized and discussed in terms of subunit localization of the redox-active nickel and non-heme iron clusters. It is proposed that nickel is ligated solely by amino acid residues of the large subunit and that the non-heme iron clusters are ligated by other cysteine-rich polypeptides encoded in the hydrogenase operons which are not necessarily homologous in either structure or function. Comparison of the hydrogenase operons or putative operons and their hydrogenase genes indicate that the arrangement, number and types of genes in these operons are not conserved among the various types of hydrogenases except for the gene encoding the large subunit. Thus, the presence of the gene for the large subunit is the sole feature common to all known nickel-containing hydrogenases and unites these hydrogenases into a large but diverse gene family. Although the different genes for the large subunits may possess only nominal general derived amino acid homology, all large subunit genes sequenced to date have the sequence R-X-C-X-X-C fully conserved in the amino terminal region of the polypeptide chain and the sequence of D-P-C-X-X-C fully conserved in the carboxyl terminal region. It is proposed that these conserved motifs of amino acids provide the ligands required for the binding of the redox-active nickel. The existing EXAFS (Extended X-ray Absorption Fine Structure) information is summarized and discussed in terms of the numbers and types of ligands to the nickel and the various redox species of nickel defined by EPR spectroscopy. New information concerning the ligands to nickel is presented based on site-directed mutagenesis of the gene encoding the large subunit of the (NiFe) hydrogenase-1 of Escherichia coli. Based on considerations of the biochemical, molecular and biophysical information, ligand environments of the nickel in different redox states of the (NiFe) hydrogenase are proposed.

The three classes of hydrogenases from sulfate-reducing bacteria of the genus Desulfovibrio.

Three types of hydrogenases have been isolated from the sulfate-reducing bacteria of the genus Desulfovibrio. They differ in their subunit and metal compositions, physico-chemical characteristics, amino acid sequences, immunological reactivities, gene structures and their catalytic properties. Broadly, the hydrogenases can be considered as 'iron only' hydrogenases and nickel-containing hydrogenases. The iron-sulfur-containing hydrogenase ([Fe] hydrogenase) contains two ferredoxin-type (4Fe-4S) clusters and an atypical iron-sulfur center believed to be involved in the activation of H2. The [Fe] hydrogenase has the highest specific activity in the evolution and consumption of hydrogen and in the proton-deuterium exchange reaction and this enzyme is the most sensitive to CO and NO2-. It is not present in all species of Desulfovibrio. The nickel-(iron-sulfur)-containing hydrogenases [( NiFe] hydrogenases) possess two (4Fe-4S) centers and one (3Fe-xS) cluster in addition to nickel and have been found in all species of Desulfovibrio so far investigated. The redox active nickel is ligated by at least two cysteinyl thiolate residues and the [NiFe] hydrogenases are particularly resistant to inhibitors such as CO and NO2-. The genes encoding the large and small subunits of a periplasmic and a membrane-bound species of the [NiFe] hydrogenase have been cloned in Escherichia (E.) coli and sequenced. Their derived amino acid sequences exhibit a high degree of homology (70%); however, they show no obvious metal-binding sites or homology with the derived amino acid sequence of the [Fe] hydrogenase. The third class is represented by the nickel-(iron-sulfur)-selenium-containing hydrogenases [( NiFe-Se] hydrogenases) which contain nickel and selenium in equimolecular amounts plus (4Fe-4S) centers and are only found in some species of Desulfovibrio. The genes encoding the large and small subunits of the periplasmic hydrogenase from Desulfovibrio (D.) baculatus (DSM 1743) have been cloned in E. coli and sequenced. The derived amino acid sequence exhibits homology (40%) with the sequence of the [NiFe] hydrogenase and the carboxy-terminus of the gene for the large subunit contains a codon (TGA) for selenocysteine in a position homologous to a codon (TGC) for cysteine in the large subunit of the [NiFe] hydrogenase. EXAFS and EPR studies with the 77Se-enriched D. baculatus hydrogenase indicate that selenium is a ligand to nickel and suggest that the redox active nickel is ligated by at least two cysteinyl thiolate and one selenocysteine selenolate residues.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of D. desulfuricans (ATCC 27774) [NiFe] hydrogenase EPR and redox properties of the native and the dihydrogen reacted states.

Redox intermediates of D. desulfuricans ATCC 27774 [NiFe] hydrogenase were generated under dihydrogen. Detailed redox titrations, coupled to EPR measurements, give access to the mid-point redox potentials of the iron-sulfur centers and of the Nickel-B signal that represents the ready form of the enzyme. The interaction between the dihydrogen molecule and the nickel centre was probed by the observation of an isotopic effect on the EPR signals detected in turnover conditions, by comparison of the H2O/H2 and D2O/D2-reacted samples.

Cloning of the 3'-phosphoadenylyl sulfate reductase and sulfite reductase genes from Escherichia coli K-12.

The structural genes for 3'-phosphoadenylyl sulfate (PAPS) reductase (cysH) and sulfite reductase (alpha and beta subunits; EC 1.8.1.2)(cysI and cysJ) of Escherichia coli K-12 have been cloned by complementation. pCYSI contains two PstI fragments (18.3 and 2.9 kb) which complement cysH-, cysI-, and cysJ- mutants. Subcloning showed that the cysH gene is located on a 1.6-kb ClaI subfragment (pCYSI-3) whereas cysI and most of cysJ are carried on a 3.7-kb ClaI subfragment (pCYSI-5). The PAPS reductase gene is closely linked to the sulfite reductase genes, but its expression is regulated by a unique promoter. The cysI and cysJ genes, on the other hand, are transcribed as an operon and the promoter precedes the cysI gene. Maxicell analysis demonstrated that pCYSI encodes three polypeptides of Mr 27,000, 57,000, and 60,000, in addition to the tetracycline-resistance determinant. The 60- and 57-kDa proteins are most likely the alpha and beta subunits, respectively, of E. coli sulfite reductase while the 27-kDa protein is putatively identified as PAPS reductase. Preliminary data suggest that the alpha and beta subunits of sulfite reductase are encoded by cysI and cysJ, respectively.

Carboxy-terminal processing of the large subunit of [NiFe] hydrogenases.

Two electrophoretic forms of the large subunit of the soluble periplasmic [NiFe] hydrogenase from Desulfovibrio gigas have been detected by Western analysis. The faster moving form co-migrates with the large subunit from purified, active enzyme. Amino acid sequence and composition of the C-terminal tryptic peptide of the large subunit from purified hydrogenase revealed that it is 15 amino acids shorter than that predicted by the nucleotide sequence. Processing of the nascent large subunit occurs by C-terminal cleavage between His536 and Val537, residues which are highly conserved among [NiFe] hydrogenases. Mutagenesis of the analogous residues, His582 and Val583, in the E. coli hydrogenase-1 (HYD1) large subunit resulted in significant decrease in processing and HYD1 activity.

Comparative EPR studies on the nitrite reductases from Escherichia coli and Wolinella succinogenes.

Hexaheme nitrite reductases purified to homogeneity from Escherichia coli K-12 and Wolinella succinogenes were studied by low-temperature EPR spectroscopy. In their isolated states, the two enzymes revealed nearly identical EPR spectra when measured at 12 K. Both high-spin and low-spin ferric heme EPR resonances with g values of 9.7, 3.7, 2.9, 2.3 and 1.5 were observed. These signals disappeared upon reduction by dithionite. Reaction of reduced enzyme with nitrite resulted in the formation of ferrous heme-NO complexes with distinct EPR spectral characteristics. The heme-NO complexes formed with the two enzymes differed, however, in g values and line-shapes. When reacted with hydroxylamine, reduced enzymes also showed the formation of ferrous heme-NO complexes. These results suggested the involvement of an enzyme-bound NO intermediate during the six-electron reduction of nitrite to ammonia catalyzed by these two hexaheme nitrite reductases. Heme proteins that can either expose bound NO to reduction or release it are significant components of both assimilatory and dissimilatory metabolisms of nitrate. The different ferrous heme-NO complexes detected for the two enzymes indicated, nevertheless, their subtle variation in heme reactivity during the reduction reaction.

The relationship between activity and the axial g = 2.06 EPR signal induced by CO in the periplasmic (Fe) hydrogenase from Desulfovibrio vulgaris.

The effect of exposure to carbon monoxide on the activity of the (Fe) hydrogenase from Desulfovibrio vulgaris has been determined. Concentrations of carbon monoxide which completely inhibit hydrogenase activity and induce formation of the axial g = 2.06 EPR signal up to 0.8 spin/molecule do not cause irreversible inhibition of the (Fe) hydrogenase.

Reactivity of Desulfovibrio gigas hydrogenase toward artificial and natural electron donors or acceptors.

A purified preparation of hydrogenase from D. gigas was inactive toward ferredoxin, flavodoxin or rubredoxin in the absence of cytochrome c3 (M.W. 13,000), in an atmosphere of hydrogen, although direct reduction of benzyl viologen or FMN was possible. The hydrogen evolution reaction from dithionite was possible with methyl viologen. The same reaction also occured with cytochrome c3 (M.W. 13,000) or cytochrome c3 (M.W. 26,000). Addition of either ferredoxin or flavodoxin did not accelerate the reaction.

Radiographic features of Legionnaires' disease.

Serial chest radiographs of 35 patients with confirmed Legionnaires' disease were evaluated. A unilateral, unilobar alveolar infiltrate was, in general, the initial radiographic finding. Progression to consolidation or to new areas of involvement was typical. Every lobe was involved, but lower lobe involvement was most common. Pleural effusion was often present. Cavitation was not seen. Radiographic progression for several days following institution of therapy, and despite clinical response, was noted. In patients who survived, radiographic improvement of abnormalities was usually apparent within two weeks of therapy. Aradiographic spectrum exists and, although many features are typical, no single feature is pathognomonic.

Investigation of an outbreak of methicillin-resistant Staphylococcus aureus in patients with skin disease using DNA restriction patterns.

OBJECTIVE: To investigate an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) among patients using chromosomal typing of the isolates. DESIGN: Comparison of epidemiological and clinical data to endonuclease restriction fragmentation analysis (RFA) of the MRSA isolates associated with an outbreak. Total DNA from the MRSA isolates was restricted with HINDIII and HAEIII for typing. SETTING: Tertiary care academic medical center. METHODS: An epidemiological investigation of an outbreak of MRSA among patients in private rooms was evaluated by routine infection control methods. The MRSA isolates from blood cultures of 7 patients and the nares of a nurse were collected during the outbreak. MRSA isolates from 23 patients not associated with the outbreak also were collected. The total DNA of the MRSA isolates were restricted with HINDIII and HAEIII and electrophoresed on 0.6% agarose gels. RESULTS: MRSA from 4 of the 7 bacteremic patients and the nurse on the outbreak unit had the same endonuclease restriction pattern. The patients were linked in that they were compromised by severe psoriasis or skin ulcers, were on the unit during the same period, and had oatmeal baths in a common bathtub. Of 50 staff members screened, the nurse was the only person detected as colonized by the strain. The other 3 patients on the unit as well as the 23 patients in other locations not associated with the outbreak had MRSA isolates with different RFA patterns. The use of the bathtub was discontinued and further transmission of MRSA was stopped. CONCLUSIONS: A comparison of the relatedness of MRSA by RFA demonstrated the uniqueness of the epidemiologically linked isolates and the utility of the RFA technique in the performance of routine infection control investigations.

Determination of trace elements in human serum by energy dispersive X-ray fluorescence.

A system of energy dispersive X-ray fluorescence spectrometry (EDXRF) has been described to measure the concentrations of iron, copper, zinc, bromine, selenium and arsenic in human serum of healthy adults. Methods of sample preparations, standardization, and analysis have been presented. Data have been presented to show the accuracy, precision and sensitivity of the EDXRF system. The major advantages of using this system for the determination of trace elements in biological tissues are the relatively small sample size, ease of sample preparation, and the ability to perform rapid multi-element analysis on a single sample. The need for multi-element analysis has become apparent from the increased knowledge of trace element interactions in biological systems. The EDXRF system provides a solution for this need. Although the present system was applied only to the measurement of six elements, in principle the concentrations of V, Cr, Mn, Ni and Ti could also be routinely determined with improvements in technology and sensitivity.

The occurrence of gamma-glutamylphenylalanine in the urine of newborn phenylketonurics.

The urine of untreated phenylketonurics in the first weeks of life contains gamma-glutamylphenylalanine (0.07--0.69 mmol/g creatinine, 12 samples) visible on the normal 2-dimensional electrophoreto-chromatogram. This compound is less prominent or absent when urine from older untreated phenylketonurics is examined and is not seen in normal urine.

The effect of dietary selenium deficiency on acute colorectal mucosal nucleotoxicity induced by several carcinogens in the rodent.

BACKGROUND: Selenium (SE) has been inversely associated with colon cancer risk. Two potential mechanisms of this effect were examined in a rodent short-term carcinogenesis assay: whether dietary SE deficiency altered the initiation aspect of carcinogenesis in the colon, and whether SE altered carcinogen metabolism. SETTING: Animal laboratory. SUBJECTS: 52 Sprague-Dawley rats, divided into a SE diet deficient group (0.002 parts per million; ppm) and a SE sufficient (0.2 ppm) group. ENDPOINTS: Weight, serum SE concentration, and karryorhectic index (KI), which is a measure of acute carcinogen induced nuclear toxicity in the colonic mucosa. METHODS: After three weeks of acclimation to the diets, eight animals from each dietary group were injected with one of the following: dimethylhydrazine (DMH), a colon specific carcinogen, its metabolite, methylazoxymethanol (MAM), or 0.9% sodium chloride. Twenty-four hours after injection the colons were removed, blood drawn, and the stained colons assayed for nuclear aberrations. RESULTS: No weight differences were generated by the dietary variations. Low-dietary SE resulted in serum SE declining markedly in the study period to 6 ng/ml versus 33 ng/ml in the SE sufficient group. Diet alone, and variations in weight gain, did not alter the KI. Both carcinogens greatly increased the KI in both the left and right colon. A SE-deficient diet was associated with a higher KI in both carcinogen groups in the right colon, with statistical significance for both the left and right colon in the MAM injection group. CONCLUSIONS: Dietary SE deficiency is associated with increased KI of the colon in MAM treated rats. SE, therefore, has a protective effect in the initiation phase of carcinogenesis.