Reentrainment of motor activity and spontaneous neuronal activity in the suprachiasmatic nucleus of Djungarian hamsters

Neurons in the suprachiasmatic nucleus (SCN) of the hypothalamus exhibit a daily rhythm in spontaneous electrical activity. Essentially two methods have been employed to record this circadian rhythm: (1) an in vitro brain slice technique and (2) in vivo multiunit recordings. Reentrainment of a circadian output to a shifted light:dark cycle commonly takes several cycles (depending on the amount of shift) until completed. Such a resetting kinetic has also been shown to be valid for SCN electrical activity if recorded in vivo. In an in vitro slice preparation, however, pharmacologically induced resetting is much faster and lacks transients; that is, a shift is completed within one cycle. This study was designed to probe for the presence of transients in the neuronal activity of the SCN in a brain slice preparation. The authors exposed Djungarian hamsters to an 8-h advanced or delayed light:dark cycle and monitored wheel-running activity during reentrainment. Additional groups of identically treated hamsters were used to record the pattern of spontaneous neuronal activity within the SCN using the brain slice preparation. Neuronal activity exhibited the usual rhythm with high firing rates during the projected day and low firing rates during the projected night. However, following 1 day of exposure to the 8-h advanced light:dark cycle, this rhythm disappeared in 6 of 7 slices. Rhythmicity was still absent following 3 days of exposure to the advanced light:dark cycle (n = 4). By contrast, 3 of 7 slices prepared from hamsters exposed to a delayed light:dark cycle for 3 days exhibited a daily rhythm in electrical activity. Although pharmacological agents reset the in vitro SCN neuronal activity almost instantaneously and in in vivo studies a stable phase relationship to a shifted light:dark cycle occurs gradually over several cycles, the authors did not detect either of these patterns. Such differences in resetting kinetics (e.g., rapid resetting, gradual reentrainment, temporary lack of measurable rhythmicity) may be due to (a) application of a resetting stimulus in vivo versus in vitro, (b) duration of the resetting stimulus, (c) the nature of the resetting stimulus, or (d) the recording technique employed.     

Computer simulation of the dynamics of a human arm and orthosis linkage mechanism

BACKGROUND: A prospective study was conducted to evaluate the clinical usefulness of three-dimensional (3D) surface-shaded maps for routine practice of myocardial perfusion single-photon emission computed tomography (SPECT) by comparison with 2D slices and 2D bull's-eye qualitative analysis. METHODS AND RESULTS: Angiograms were performed on 201 consecutive patients, 155 with coronary artery disease (CAD) and 46 with no significant CAD. One-day 201TI stress/rest-reinjection protocol was performed in 110 patients, and 1-day 99mTc-sestamibi or tetrofosmin stress/rest protocol was performed in 91. The stress protocol was either exercise or dipyridamole (0.56 mg/kg) infusion. Three-dimensional surface maps were obtained by using a threshold for the transaxial data at 50%, 55%, 60%, 65%, and 70% of the maximum pixel value in the first 60 patients. Interpretation of 3D maps was based on the presence of a complete (transmural-looking) perfusion hole within the myocardial wall; doubtful patterns were considered pathologic or normal. Good diagnostic values were found for the 50% to 60% thresholds, but the 60% setting showed the best concordance with multislice and bull's-eye analysis; higher values drastically degraded the specificity. Considering doubtful patterns as normal clarified interpretation and led to a small loss in sensitivity but high gain in specificity. Applied to the whole population, the 3D maps using a 60% threshold provided similar diagnostic value to detect CAD as did conventional and bull's-eye analysis. Moreover, the 3D maps showed a trend toward higher specificity and a proportionally smaller decrease in sensitivity (sensitivity: 92.9%, 90.3%, 89.7%; specificity: 45.6%, 50.0%, 58.7% for tomograms, bull's-eye analysis, and 3D maps, respectively), especially for the detection of left anterior descending and right CAD. Multivessel disease was detected in an identical manner. Three-dimensional maps might improve detection of perfusion defects in the basal regions. However, 3D maps were found to be less sensitive than slices and particularly bull's-eye analysis for the reversibility of stress defects. CONCLUSIONS: Three-dimensional surface display of myocardial perfusion is a valuable independent tool for determining presence, extent, and location of CAD. It can convey useful first-look information to the referring physician, especially through a cine-rotational motion (as done in our practice through use of a floppy disk.     

Phylogenetic characterization of bacteria in the subsurface microbial culture collection

The Subsurface Microbial Culture Collection (SMCC) was established by the U.S. Dept. of Energy (DOE) and contains nearly 10,000 strains of microorganisms (mostly bacteria) isolated from terrestrial subsurface environments. Selected groups of bacterial isolates from three sample sites situated above geochemically and hydrologically different subsurface environments have been characterized by phylogenetic analysis of 16S ribosomal RNA (rRNA) gene nucleotide sequences. Among these isolates were members of six major phylogenetic groups of bacteria: the high-G+C and low-G+C Gram-positive bacteria; the alpha-, beta-, and gamma-subdivisions of the Proteobacteria; and the Flexibacter/Cytophaga/Bacteroides group. A small number of the SMCC strains may be members of new bacterial genera, but most of them could be placed with reasonable confidence into more than 35 previously described genera. The majority of the Gram-positive isolates were species of Arthrobacter, Bacillus, or Streptococcus, whereas Acinetobacter, Comamonas, Pseudomonas, Sphingomonas, and Variovorax were among the most frequently encountered Gram-negative genera. A high proportion of the strains were placed in fewer than 10 genera, implying that there is substantial duplication within the SMCC at the genus level. When groups of isolates assigned to Acinetobacter, Arthrobacter, or Sphingomonas were analyzed in more detail, however, it was found that each group consisted of subgroups of strains that probably differed at the species level. Restriction endonuclease analysis (applied to the strains from one sample site) indicated that additional diversity was present at the strain level. Most of the SMCC isolates assigned to some genera (e.g., Acinetobacter) were very closely related to previously described species in those genera, but most of the isolates assigned to other genera (e.g., Arthrobacter and Sphingomonas) appeared (or were shown) to be new species, thereby indicating that a reasonable amount of novelty is present within the SMCC at the species level.     

Cholesterol synthesis is increased in mixed hyperlipidaemia

We showed previously that hypertriglyceridaemia, but not hypercholesterolaemia, is correlated with increases in cholesterol synthesis and apolipoprotein B secretion in patients with secondary hypertriglyceridaemia. The aim of the present study was to compare the rate of cholesterol synthesis, using fasting plasma mevalonic acid (MVA) as an index, in patients with primary mixed hyperlipidaemia (type IIb phenotype, n=45) and primary hypercholesterolaemia (type IIa phenotype, n=92). LDL cholesterol was significantly higher in types IIa (6.38+/-0.18 mmol/l) and IIb (5.89+/-0.25 mmol/l) compared to 40 normolipidaemic controls (2. 99+/-0.1 mmol/l, P<0.0001), whereas serum triglyceride was higher in type IIb (2.62 (range 2.2-3.0) mmol/l) than type IIa (1.22 (range 0. 85-1.60) mmol/l, P<0.001) and controls (0.90 (range 0.68-1.24) mmol/l, P<0.001). Similarly, MVA was higher in type IIb (7.0+/-0.46 ng/ml) than IIa (5.6+/-0.23 ng/ml, P<0.0) and controls (5.6+/-0.36 ng/ml, P<0.05). Plasma MVA correlated positively with serum triglyceride (r=0.22, P=0.004) and negatively with LDL cholesterol (r=-0.21, P=0.014). These results are in accordance with previous observations that VLDL-apolipoprotein B secretion and cholesterol synthesis are linked and demonstrate that the latter is increased in mixed hyperlipidaemia.     

Management of renal trauma at a rural, level I trauma center

Eotaxin is a potent and selective CC chemokine for eosinophils and basophils. We established several monoclonal antibodies (Mabs) allowing the neutralization and measurement of human eotaxin. Using the Mabs as probes, we demonstrated that normal eosinophils contained intracellular granule-associated eotaxin. Quantification of cell-associated eotaxin in different leukocyte subsets revealed that it was principally expressed in eosinophils. Finally, we showed that normal eosinophils released eotaxin upon stimulation with either of two secretagogues, C5a or ionomycin. These findings raise the possibility that eosinophil-derived eotaxin contributes to the local accumulation of eosinophils at the site of inflammation.     

Synovial sarcoma of the vulva: a report of two cases

We report two cases of synovial sarcoma arising in the vulva. The patients were 30 and 37 years old and presented with a painless mass that was interpreted clinically as a cyst. The tumors were 2.0 and 1.2 cm in greatest diameter. Histologically, they were composed of epithelial cells forming solid nests and gland-like and papillary structures surrounded by spindle-shaped cells. Immunohistochemically, the epithelial cells stained for cytokeratin and the spindle-shaped cells for vimentin. Ultrastructurally, the epithelial cells had prominent intercellular junctions and narrow microvilli and were separated from the spindle-shaped cells by a basal lamina. The spindle-shaped cells were closely apposed with focal intercellular contacts. One tumor recurred locally 3.5 years after excision, but the patient was alive and well 1 year after a re-excision and radiation therapy. The other patient was alive and well 4 years after an excision. These tumors are the first reported examples of synovial sarcoma arising in the vulva.