No evidence for dependence of early cortical auditory processing on dopamine D(2)-receptor modulation: a whole-head magnetoencephalographic study.

Magnetoencephalography (MEG) was used to determine the effect of neuroleptic challenge on brain responses in healthy subjects. In a double-blind, randomized, placebo-controlled, cross-over design study, the dopamine D(2) receptor antagonist haloperidol (2 mg) was given orally to 12 healthy volunteers. The middle-latency auditory evoked magnetic fields (MAEF) were recorded 3 h after administration of haloperidol or placebo with a whole-head 122-channel MEG. Haloperidol did not significantly affect MAEF responses. The dipole moments and source locations of the responses were not significantly influenced by haloperidol. These results suggest that dopamine D(2) receptors are not involved in the early phases of auditory cortical processing.

The prevalence and distribution of white-matter changes on different MRI pulse sequences in a post-stroke cohort.

No uniform criteria currently exist for rating white-matter (WM) high-signal foci on MRI. Ratings are based on descriptive terms, different pulse sequences and different WM areas. Reports on the prevalence and clinical correlates of high-signal foci have been contradictory. We wanted to examine the contribution of the pulse sequence and WM area on rating WM changes. We analysed WM changes separately on T2-, protondensity (PD)- and T1-weighted images in periventricular, subcortical, watershed area and deep WM. The difference between T2- and PD-weighted images was significant for frontal caps, counting small foci or analysing subcortical changes. T1-weighted images showed significantly less change, but the number of foci detected was greater than previously thought. The prevalence of WM high-signal foci was greatest in the watershed zone and smallest in the subcortical area. There was a significant correlation between foci in different areas.

Magnetic resonance imaging white matter hyperintensities and mechanism of ischemic stroke.

BACKGROUND AND PURPOSE: We sought to determine the relations between infarct subtype and white matter hyperintensities (WMHIs) on MRI. MATERIALS AND METHODS: We studied 395 ischemic stroke patients with 1. 0-T MRI. The number of lacunar, border-zone, and cortical infarcts was registered. WMHIs were analyzed in 6 areas. Univariate and multivariate statistical analyses were used to find the risk factors for different infarct subtypes and to study the connections between WMHIs and brain infarcts. RESULTS: Lacunar infarcts were associated with hypertension (odds ratio [OR], 1.79; 95% CI, 1.17 to 2.73), alcohol consumption (OR, 1.96; 95% CI, 1.17 to 3.28), and age (OR, 1. 03; 95% CI, 1.00 to 1.06). Border-zone infarcts were associated with carotid atherosclerosis (OR, 2.20; 95% CI, 1.15 to 4.19). Atrial fibrillation (OR, 3.02; 95% CI, 1.66 to 5.50) and carotid atherosclerosis (OR, 1.94; 95% CI, 1.12 to 3.36) were independent positive predictors, and history of hyperlipidemia (OR, 0.44; 95% CI, 0.26 to 0.75) and migraine (OR, 0.48; 95% CI, 0.25 to 0.93) were negative predictors for cortical infarcts. Patients with lacunar infarcts had more severe WMHIs than patients with nonlacunar infarcts in all WM areas (P

3D spin-lock imaging of human gliomas.

We investigated whether the simultaneous use of paramagnetic contrast medium and 3D on-resonance spin lock (SL) imaging could improve the contrast of enhancing brain tumors at 0.1 T. A phantom containing serial concentrations of gadopentetate dimeglumine (Gd-DTPA) in cross-linked bovine serum albumin (BSA) was imaged. Eleven patients with histologically verified glioma were also studied. T1-weighted 3D gradient echo images with and without SL pulse were acquired before and after a Gd-DTPA injection. SL effect, contrast, and contrast-to-noise ratio (CNR) were calculated for each patient. In the glioma patients, the SL effect was significantly smaller in the tumor than in the white and gray matter both before (p = 0.001, p = 0.025, respectively), and after contrast medium injection (p < 0.001, p < 0.001, respectively). On post-contrast images, SL imaging significantly improved tumor contrast (p = 0.001) whereas tumor CNR decreased slightly (p = 0.024). The combined use of SL imaging and paramagnetic Gd-DTPA contrast agent offers a modality for improving tumor contrast in magnetic resonance imaging (MRI) of enhancing brain tumors. 3D gradient echo SL imaging has also shown potential to increase tissue characterization properties of MR imaging of human gliomas.

Isolation and characterization of a purC(orf)QLF operon from Lactococcus [correction of Lactobacillus] lactis MG1614.

We have isolated genes encoding enzymes of the de novo purine nucleotide biosynthesis pathway from Lactococcus lactis MG1614 by colony hybridization using DIG-labeled DNA probes. The organization of the genes needed for the de novo biosynthesis of purine nucleotides in L. lactis differs from that found in other organisms. In L. lactis there is a gene cluster, which contains five out of the 11 genes needed for the de novo biosynthesis of IMP, namely purC, orf, purQ, purL and purF. These genes were shown to be transcribed as a single transcription unit by Northern hybridization analysis. The 5' end of the transcript of the purC(orf)QLF operon was determined by primer extension analysis using fluorescently end-labeled probes. The purC(orf)QLF operon of L. lactis is transcribed in Escherichia coli, and the gene product of the purF gene, glutamine phosphoribosylpyrophosphate amidotransferase (glutamine PRPP ATase, EC 2.4.2.14), can functionally complement the E. coli purF mutant strain TX158. We also show that the promoter of the purC(orf)QLF operon is regulated in response to exogenously added purines.

Variable agreement between visual rating scales for white matter hyperintensities on MRI. Comparison of 13 rating scales in a poststroke cohort.

BACKGROUND AND PURPOSE: Previous reports on the frequency, extent, and clinical correlates of white matter hyperintensities (WMHIs) have been contradictory. The purpose of this study was to test whether part of this variation could be explained by the different properties of the visual WMHI rating scales used. METHODS: The periventricular (PVHIs) and deep white matter (DWMHIs) hyperintensities of 395 poststroke patients were systematically analyzed and transformed to correspond to 13 different rating scales. The scales were compared with the use of Goodman-Kruskal measures of association. The relative frequencies, means, and medians of PVHI and DWMHI grades as well as Spearman rank correlations between WMHI grade and hypertension were calculated. RESULTS: At best more than 80% of the patients received an equivalent WMHI grade by different scales, but at worst the corresponding values were only 0.4% for PVHI and 18% for DWMHI. At best different scales categorized patients similarly in regard to WMHI grade, but at worst the corresponding values were 8% for PVHI and 57% for DWMHI ratings. The distribution of WMHI grades also varied, and when the effect of age on WMHI was assessed, some of the scales had a ceiling effect and some had a floor effect. Only 1 of the 7 PVHI, 5 of the 9 DWMHI, and 1 of the 3 combined rating scales showed a significant correlation with arterial hypertension, a putative risk factor for WMHIs. CONCLUSIONS: Some of the inconsistencies in previous studies of WMHIs are due to differences in visual rating scales. Our findings may warrant international debate regarding harmonization of WMHI ratings.

C-terminal truncations of a thermostable Bacillus stearothermophilus alpha-amylase.

A series of truncated proteins from a thermostable Bacillus stearothermophilus alpha-amylase was prepared to study the importance of the extension in the C-terminus compared with other liquefying Bacillus alpha-amylases. The mutations introducing new translation termination sites shortened the 515 amino acid residue-long wild type enzyme by 17, 32, 47, 73 or 93 residues. The longer the truncation, the lower the specific activity of the enzyme. Only the two longest mutant proteins were active: the specific activity of the 498 residue variant was 97% and protein 483 was 36% that of the parental enzyme. The Km values of starch hydrolysis changed from 1.09 for wild type enzyme to 0.35 and 0.21 for mutants 498 and 483, respectively, indicating altered substrate binding. The mutant enzymes had almost identical pH and temperature optima with the wild type amylase, but enhanced thermal stability and altered end product profile. The consequences of the truncation to the structure and function of the enzymes were explored with molecular modeling. The liquefying amylases seem to require approximately 480 residues to be active, whereas the C-terminal end of B.stearothermophilus amylase is required for increased activity.

Blood pressure reactivity in patients with neurocirculatory asthenia.

The hemodynamic reactions of 30 young men with neurocirculatory asthenia (NCA) were compared to those of 30 healthy controls in isometric handgrip test, orthostatic test, and cold pressor test in order to study the regulation of the central circulation of NCA patients. The measurements were made using sphygmomanometry, ECG, and impedance cardiography. In the isometric handgrip test the heart rate and the diastolic and mean blood pressure increased slightly more (P less than 0.05) in the NCA group than in the controls. In the NCA group the blood pressure rise was, on average, due to an increase in the peripheral vascular resistance, while in the control group it was caused by an elevation in the cardiac output. In the orthostatic and cold pressor tests the hemodynamic alterations were quite similar in the two groups. It is concluded that the NCA patients have in the orthostatic and cold pressor tests a normal ability to elevate the blood pressure by increasing the peripheral vascular resistance. The lack of rise in the cardiac output during the isometric handgrip test in the NCA group is an abnormal reaction, the reason of which remains to be studied.

Rapid changes in rate-corrected and uncorrected systolic time intervals during cold pressor test.

The changes in heart rate and systolic time intervals were studied in a group of 10 young healthy male volunteers during immersion of their hand in ice water for 1 min. The heart rate and systolic time intervals were measured from electro-, phono-, and impedance cardiograms in the standard way. When the cold immersion was done in the supine position the left ventricular ejection time (LVET) and the electromechanic systole (Q-S2Tc) shortened, and when corrected for the heart rate the Q-S2Tc lengthened in the beginning of the immersion. In the head-up position the Q-S2T shortened in the beginning of the immersion while the rate-corrected systolic time intervals remained unchanged. Most of the changes in the systolic time intervals disappeared before the last quarter of the cold immersion. It was observed that during the cold immersion the linear regression coefficients between the heart rate and the Q-S2T in the supine position as well as between the heart rate and the LVET, Q-S2T and the PEP in the head-up position were greater than the regression coefficients used in the rate correction.

Relationship between systolic time intervals and heart rate during four circulatory stress tests.

The linear regression equations between heart rate and systolic time intervals were calculated before and during a handgrip test, an orthostatic test, the Valsalva test and a cold pressor test. The subjects were 30 healthy men, average age 20 years. During the 1st min of orthostasis the regression line of the left ventricular ejection time (LVET) was significantly (P less than 0.05) steeper than at rest and that of the pre-ejection period (PEP) was significantly (P less than 0.01) less steep than at rest, and the regression between HR and the PEP/LVET ratio deviated significantly (P less than 0.001) from zero. During the Valsalva maneuver, the regression line of the LVET became significantly (P less than 0.001) steeper than at rest and the regression coefficient of the PEP changed from negative to positive, the difference being significant (P less than 0.001); the regression between HR and the PEP/LVET also deviated significantly (P less than 0.001) from zero. During the cold pressor test the regression line of the electromechanic systole (Q-S2 time) was significantly (P less than 0.01) less steep than at rest. It was concluded that the use of regression equations calculated for the systolic time intervals and heart rate at rest can lead to errors when applied to rate correction of systolic time intervals during an orthostatic, Valsalva, or a cold pressor test.

Delayed cord clamping in cesarean section with general anesthesia.

Delay in cord clamping after vaginal delivery increases the blood volume of the newborn. Similar effects have also been observed in cesarean section births. Other effects of delayed cord clamping in cesarean section have not been investigated. In a group of nineteen healthy mothers having elective cesarean sections the cord clamping time was increased from 0 minutes to 1.5 and 3 minutes. Significantly lowered PO2 and pH and elevated plasma lactate levels were observed in infants with 3 minutes' delay when compared with the early clamping group. We conclude that, when healthy mature newborns are considered, early clamping of umbilical cord in cesarean section with general anesthesia is preferable to late clamping.

Relationship between the changes in heart rate and cardiac output during the Valsalva maneuver.

Ten young (average age 20 years) healthy male volunteers performed the Valsalva maneuver (40 mmHg for 15 seconds) in the supine and the upright position. The heart rate (HR), stroke volume (SV) and the cardiac index (CI) were registered using ECG and impedance cardiography. During the expiratory strain of the Valsalva maneuver the HR increased about equally in the two positions while the decreases in the SV and the CI were in the supine position significantly greater than in the upright position. The CI decreased to equal levels in both positions after 15 seconds of strain. The rise in the HR due to the expiratory strain did not correlate significantly with the decrease in the CI in either position. The correlation between the HR rise and the SV decrease was almost significant (p less than 0.05) in the supine position and significant (p less than 0.01) in the upright position after 5 seconds of strain but not after 10 or 15 seconds. These observations suggest that the relationship between the rise in the HR and the decrease in the venous return does not remain constant during 15 seconds of expiratory strain. Perhaps the cardiopulmonary baroreceptor reflexes affect the HR after five seconds of strain more than they do after 10 or 15 seconds of strain.

Heart rate variability, cardiac mechanics, and subjectively evaluated stress during simulator flight.

The effects of a simulator flight task on the heart rate variation (HRV) and hemodynamic variables were studied in nine pilots with instrument flight ratings. An electrocardiogram (ECG), phonocardiogram (PCG), and impedance cardiogram (ICG) were recorded continuously during three successive flights. Indices of HRV, power spectra, and autocorrelograms were computed from the R-R interval signal. Stroke volume (SV), cardiac output (CO), and systolic time intervals (STI) were determined by means of the ECG, PCG, and ICG. A scaling method for a subjective evaluation of tiredness, effort, and success during the flight was used. The repeats of the flight task decreased the heart rate (HR), CO, and cardiac index (CI). The different phases of the flight altered the HR (mean 97 min-1, S.E.M. 4 min-1), total HRV (RMSM) (mean 33 ms, S.E.M. 5 ms), and the periodic HRV. Subjectively, the pilots felt only moderate stress. The subjectively evaluated tiredness was significantly associated with the STI. Moderate informative stress in the flight simulator affected the chronotropic parameters of the heart. The inotropic state of the heart was not affected by the different phases of the flight but possibly by the diminishing sympathetic drive with accommodation during the repeats.

Sudden unexpected infantile death (SUD) of a healthy boy occurring on the doctor's examining table at a well baby clinic.

The child described was 1 year 1 month, and was well developed and healthy. He underwent SUD following the doctor's examination in the presence of the doctor, nurse and mother. The case terminated fatally despite adequate resuscitation. The post mortem examination did not reveal the cause of death. The authors feel that the case supports their previously presented hypothesis of infant neurocirculatory dystony as the cause of SUD. When the infant mortality drops below 15% SUD remains as one of the chief causes of infant death.