MR of the brain in Sjögren-Larsson syndrome.

Cerebral MR was performed in three patients with Sjögren-Larsson syndrome. In each case, a 1.5-T system was used, and the patient was under general anesthesia. The MR findings included confluent hyperintense white matter lesions in the periventricular and deep white matter of the centrum semiovale, with sparing of the subcortical U fibers. The topography of the white matter abnormalities correlated well with the clinical signs and symptoms.

Comparison of imaging TNM [(i)TNM] and pathological TNM [pTNM] in staging of bronchogenic carcinoma.

OBJECTIVE: Precise tumor (T) and nodal (N) staging is imperative in non-small cell lung cancer (NSCLC) as it determines subsequent treatment, certainly when considering neoadjuvant treatment for stage IIIA or IIIB disease. To determine the accuracy of present-day computed tomographic (CT) scanning a prospective study was performed comparing imaging TNM [(i)TNM] and pathological TNM [pTNM]. METHODS: In 74 patients with NSCLC without distant metastases (i)TNM was determined on CT findings. The TNM system advocated by the American Joint Committee on Cancer was used. All patients underwent cervical mediastinoscopy. When superior mediastinal nodes were negative this was followed by thoracotomy and pathological examination of the resected specimen and lymph nodes to determine pTNM. RESULTS: The agreement between (i)TNM and pTNM was only 35.1%. The primary tumor (T) was correctly staged in 54.1%, overstaged in 27.0% and understaged in 18.9% of the patients. Invasion of chest wall, pericardium and of major mediastinal structures (T3, T4) was not reliably detected by CT scan. Sensitivity and specificity of CT regarding hilar and mediastinal lymph node staging were 48.3 and 53.3%, positive and negative predictive value 40 and 61.1% and its overall accuracy 51.4%. The nodal (N) factor was correctly determined by CT scan in 35.1%, overstaged in 44.6%, and understaged in 20.3% of the patients. CONCLUSIONS: Even with present-day CT scanners (i)TNM provides no accurate staging and routine mediastinoscopy is necessary for precise mediastinal lymph node staging. Likewise, (i)T3 and (i)T4 determinations are unreliable and should not contraindicate thoracotomy.

Prospective evaluation of computed tomography and mediastinoscopy in mediastinal lymph node staging.

Precise mediastinal lymph node (LN) staging is imperative in otherwise operable non-small cell lung cancer (NSCLC), as it determines subsequent treatment and possible inclusion in a neoadjuvant trial. The roles of mediastinoscopy and computed tomography (CT) remain controversial. To determine the accuracy of current CT scanners, a prospective study was performed. From April 1993 until September 1995, 100 consecutive patients with NSCLC without distant metastases underwent staging by CT and cervical mediastinoscopy. Naruke's map was used for classification, and LNs larger than 1 cm were considered CT positive. There were 91 males and 9 females, with a mean age of 64 (range 45-82) yrs. Fifty nine tumours were central and 41 peripheral, 64 right-sided and 36 left-sided. Thoracotomy with mediastinal LN sampling was performed in 74 patients, nonoperated patients having multilevel stage IIIA or stage IIIB disease. Twenty five (25%) mediastinoscopies were positive and three were false-negative (3%). There were 29 false-positive CT scans and 12 false-negative. Overall sensitivity and specificity of CT were 63 and 57%, respectively, and of mediastinoscopy 89 and 100%, respectively. Positive and negative predictive values of CT were 41 and 77%, respectively, and of mediastinoscopy 100 and 96%, respectively. Accuracy of CT was 59% and of mediastinoscopy 97%. Accuracy of CT was lowest for left-sided and centrally located tumours, and for LN station 7. Even with current computed tomography scanners, sensitivity and specificity remain low. Although overall cost may increase, routine cervical mediastinoscopy is necessary for precise staging of non-small cell lung cancer, and subcarinal lymph nodes should be routinely sampled.

Charge recombination reactions in photosystem II. 2. Transient absorbance difference spectra and their temperature dependence.

Absorbance difference spectra of the transient states in photosystem II (PS II) have been examined in the Qv absorption region between 660 and 700 nm. The P680+Pheo-/P680Pheo, 3P680/P680, and P680+QA-/P680QA spectra were measured in O2-evolving PS II core complexes from Synechococcus and PS II-enriched membrane fragments from spinach. The low-temperature absorbance difference spectra vary only slightly between both PS II preparations. The 3P680/P680 spectrum is characterized by a bleaching at 685 nm at 25 K and indicates weak exciton coupling with neighboring pigment(s). We conclude that P680 absorbs at 685 nm in more intact PS II preparations at cryogenic temperature. The difference spectra of the radical pairs are strongly temperature dependent. At low temperature the P680+QA-/P680QA- spectrum exhibits the strongest bleaching at 675 nm whereas the P680+Phe-/P680Pheo spectra show two distinct bleaching bands at 674 and 684 nm. It is suggested that an electrochronic red shift resulting in a bleaching at 675 nm and an absorbance increase at about 682 nm dominates the spectral features of the charge-separated states. On the basis of the present results and those in the literature, we conclude that the interactions between the pigments and especially the organization of the primary donor must be quite different in PS II compared to bacterial reaction centers, although the basic structural arrangement of the pigments might be similar. Spectral data obtained with samples in the presence of singly and doubly reduced QA indicate that the primary photochemistry in PS II is not strongly influenced by the redox state of QA at low temperature and confirm the results of the accompanying paper [Van Mieghem, F. J. E., Brettel, K., Hillmann, B., Kamlowski, A., Rutherford, A. W., & Schlodder, E. (1995) Biochemistry 34, 4798-4813]. The spectra of the primary radical pair and the reaction center triplet obtained with more intact PS II preparations differ widely from those of D1/D2/cyt b-559 complexes. In the latter sample, where 3P680 formation results in a bleaching at 680 nm, the P680+Pheo-/P680Pheo spectrum shows only one broad bleaching band at about 680 nm, and the main bleaching due to photoaccumulation of Pheo- at 77 K appears at 682 nm instead of 685 nm in PS II core complexes. This indicates that the removal of the core antenna which is accompanied by the loss of QA causes also structural changes of the reaction center.

Charge recombination reactions in photosystem II. I. Yields, recombination pathways, and kinetics of the primary pair.

Recombination reactions of the primary radical pair in photosystem II (PS II) have been studied in the nanosecond to millisecond time scales by flash absorption spectroscopy. Samples in which the first quinone acceptor (QA) was in the semiquinone form (QA-) or in the doubly reduced state (presumably QAH2) were used. The redox state of QA and the long-lived triplet state of the primary electron donor chlorophyll (3P680) were monitored by EPR. The following results were obtained at cryogenic temperatures (around 20 K). (1) the primary radical pair, P680+Pheo-, is formed with a high yield irrespective of the redox state of QA. (2) The decay of the primary pair is faster with QA- than with QAH2 and could be described biexponentially with t1/2 approximately 20 ns (approximately 65%)/150 ns (approximately 35%) and t1/2 approximately 60 ns (approximately 35%)/250 ns (approximately 65%), respectively. The different kinetics may be due to electrostatic and/or magnetic effects of QA- on charge recombination or due to conformational changes caused by the double reduction treatment. (3) The yield of the triplet state 3P680 was high both with QA- and QAH2. (4) The triplet decay was much faster with QA- [t1/2 approximately 2 microseconds (approximately 50%)/20 microseconds (approximately 50%)] than with QAH2 [t1/2 approximately 1 ms (approximately 65%)/3 ms (approximately 35%)]. The short lifetime of the triplet with QA- explains why it was not detected earlier. The mechanism of triplet quenching in the presence of QA- is not understood; however it may represent a protective process in PS II. (5) Almost identical data were obtained for PS II-enriched membranes from spinach and PS II core preparations from Synechococcus. Room temperature optical studies were performed on the Synechococcus preparation. In samples containing sodium dithionite to form QA- in the dark, EPR controls showed that multiple excitation flashes given at room temperature led to a decrease of the QA-Fe2+ signal, indicating double reduction of QA. During the first few flashes, QA- was still present in the large majority of the centers. In this case, the yield of the primary pair at room temperature was around 50%, and its decay could be described monoexponentially with t1/2 approximately 8 ns (a slightly better fit was obtained with two exponentials: t1/2 approximately 4 ns (approximately 80%)/25 ns (approximately 20%).(ABSTRACT TRUNCATED AT 400 WORDS)

Crohn's disease and sclerosing cholangitis: CT and PTC diagnosis, with MR findings.

Computed tomography (CT), percutaneous transhepatic cholangiography (PTC) and magnetic resonance imaging (MRI) findings in a case of sclerosing cholangitis associated with Crohn's disease of the colon and terminal ileum are described. CT gives additional information on dilatation of peripheral bile ducts and confirms findings of PTC, i.e. a decreased arborization of the biliary tree, a nodular appearance of the common bile duct and multifocal bile duct strictures. CT findings could be recognized on MRI which provided no additional information.

CT imaging of soft tissue pathology of the ankle. A pictorial essay.

Despite the increasing importance of MR imaging, CT investigation remains a very useful and frequently applied method in the study of ankle pathology. In a short pictorial essay, the contribution of this technique to the diagnosis of soft tissue pathology of the ankle is discussed and illustrated.

Oxygen-evolving photosystem II preparation from wild type and photosystem II mutants of Synechocystis sp. PCC 6803.

We present here a simple and rapid method which allows relatively large quantities of oxygen-evolving photosystem II- (PS-II-) enriched particles to be obtained from wild-type and mutants of the cyanobacterium Synechocystis 6803. This method is based on that of Burnap et al. [Burnap, R., Koike, H., Sotiropoulou, G., Sherman, L. A., & Inoue, Y. (1989) Photosynth. Res. 22, 123-130] but is modified so that the whole preparation, from cells to PS-II particles, is achieved in 10 h and involves only one purification step. The purified preparation exhibits a 5-6-fold increase of O2-evolution activity on a chlorophyll basis over the thylakoids. The ratio of PS-I to PS-II is about 0.14:1 in the preparation. The secondary quinone electron acceptor, QB, is present in this preparation as demonstrated by thermoluminescence studies. These PS-II particles are well-suited to spectroscopic studies as demonstrated by the range of EPR signals arising from components of PS-II that are easily detectable. Among the EPR signals presented are those from a formal S3-state, attributed to an oxidized amino acid interacting magnetically with the Mn complex in Ca(2+)-deficient PS-II particles, and from S2 modified by the replacement of Ca2+ by Sr2+. Neither of these signals has been previously reported in cyanobacteria. Their detection under these conditions indicates a similar lesion caused by Ca2+ depletion in both plants and cyanobacteria. The protocol has also been applied to mutants which have site-specific changes in PS-II. Data are presented on mutants having changes on the electron donor (Y160F) and electron acceptor (G215W) side of the D2 polypeptide.

Computed tomography of major salivary gland tumors. A retrospective study of 31 cases.

To assess the value of computed tomography (CT) in grading (benign versus malignant) and characterization of salivary gland tumors we retrospectively analysed the CT examinations of 31 histologically proven cases (15 pleomorphic adenomas, 6 cystadenolymphomas, 1 lipoma, 4 malignant tumors, 4 cysts, and 1 abscess). Subsequently we studied the localization, size, shape, margins, intratumoral calcification, central lucency, local invasion, homogeneity, density, degree and pattern of enhancement after intravenous contrast injection, and presence of enlarged locoregional lymph nodes. A lesion with ill-defined margins, local invasion, diffuse spread throughout the gland and enlarged locoregional lymph nodes was considered malignant. All malignant lesions were correctly diagnosed (no false negative) but 3 benign lesions had malignant features on CT (3 false positives). Further characterization between pleomorphic adenomas and cystadenolymphomas is often impossible. A cystic lesion with papillary contrast-enhancing projections was found in 2 out of 6 cystadenolymphomas and not in other lesions.

Repetitive action potentials in isolated nerve terminals in the presence of 4-aminopyridine: effects on cytosolic free Ca2+ and glutamate release.

The mechanisms by which an elevated KCl level and the K+-channel inhibitor 4-aminopyridine induce release of transmitter glutamate from guinea-pig cerebral cortical synaptosomes are contrasted. KCl at 30 mM caused an initial spike in the cytosolic free Ca2+ concentration ([Ca2+]c), followed by a partial recovery to a plateau 112 +/- 13 nM above the polarized control. The Ca2+-dependent release of endogenous glutamate, determined by continuous fluorimetry, was largely complete by 3 min, by which time 1.70 +/- 0.35 nmol/mg was released. [Ca2+]c elevation and glutamate release were both insensitive to tetrodotoxin. KCl-induced elevation in [Ca2+]c could be observed in both low-Na+ medium and in the presence of low concentrations of veratridine. 4-Aminopyridine at 1 mM increased [Ca2+]c by 143 +/- 18 nM to a plateau similar to that following 30 mM KCl. The initial rate of increase in [Ca2+]c following 4-aminopyridine administration was slower than that following 30 mM KCl, and a transient spike was less apparent. Consistent with this, the 4-aminopyridine-induced net uptake of 45Ca2+ is much lower than that following an elevated KCl level. 4-Aminopyridine induced the Ca2+-dependent release of glutamate, although with somewhat slower kinetics than that for KCl. The measured release was 0.81 nmol of glutamate/mg in the first 3 min of 4-aminopyridine action. In contrast to KCl, glutamate release and the increase in [Ca2+]c with 4-aminopyridine were almost entirely blocked by tetrodotoxin, a result indicating repetitive firing of Na+ channels. Basal [Ca2+]c and glutamate release from polarized synaptosomes were also significantly lowered by tetrodotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)