Cardiovascular haemodynamic response to repeated mental stress in normotensive subjects at genetic risk of hypertension: evidence of enhanced reactivity, blunted adaptation, and delayed recovery.

To identify unique cardiovascular responses to stressors in a population at genetic risk of hypertension, we studied haemodynamic responses in initial reactivity to, subsequent adaptation to, and final recovery from repeated active mental stress in young, normotensive individuals stratified by hypertension parental history (PH). Two groups (n=21/group) of normotensive white males underwent stress testing. One group (N+PH) had a hypertensive parent, while the other group (N-PH) did not. Cardiovascular response was measured before, during, and after repeated serial-subtraction math. Initial reactivity was measured as the difference between baseline and initial stress response, subsequent adaptation as the difference in response to repeated trials, and final recovery was assessed by the difference between baseline and postbaseline levels. The influence of PH on reactivity, adaptation, and recovery was assessed by repeated measures ANOVA for stroke volume, cardiac output, pre-ejection period, total peripheral resistance, mean successive heartbeat time difference, blood pressure, and heart rate. Multivariate analysis of variance (MANOVA) determined the effect of PH on overall reactivity, adaptation, and recovery. As compared to the N-PH group, initial reactivity was higher in the N+PH group for cardiac index (P<0.05) and pre-ejection period (P<0.05). Subsequent adaptation in the N+PH group was significantly slower for pre-ejection period (P=0.03). Finally, the N+PH group showed delayed recovery in heart rate (P=0.03), diastolic blood pressure (P<0.05), and pre-ejection period (P=0.007). In conclusion, the heightened reactivity, lack of adaptation, and delayed recovery occur in the sympathetic system of normotensive subjects at genetic risk of hypertension, specifically in beta-adrenergic responses (pre-ejection period). The parasympathetic response (mean successive heartbeat time difference) was not different. Increased cardiac output reactivity in the N+PH group (P<0.05) thus precedes any difference in blood pressure reactivity (P<0.99). Delayed recovery of diastolic blood pressure is also found in the N+PH group (P<0.05), which suggests lower baroreceptor sensitivity. Since delayed recovery in heart rate (P=0.03), and diastolic blood pressure (P<0.05) occur in N+PH subjects even before the corresponding changes in reactivity (P>0.10) or adaptation (P>0.07) are seen, these recovery impairments may be among the earliest precursors to the development of essential hypertension in this population. Finally, PH group haemodynamic differences suggest that these traits (reactivity, adaptation, and recovery) may constitute early 'intermediate' phenotypes in the pathogenesis of hypertension.

In vitro biocompatibility of oxirane/polyol dental composites with promising physical properties.

OBJECTIVES: Visible light cure oxirane/polyol resins of Cyracure UVR-6105 with pTHF-250 has been previously shown useful for development of dental composites. This oxirane/polyol (4016) in combination with other oxiranes were formulated into composites (4016E, 4016G and 4016GB) containing 72.9-74.9% quartz filler. The main objective of the study was to evaluate some of the physical properties and the biocompatibility of the composites. RESULTS: PhotoDSC analysis of composites demonstrated twice the enthalphy values of Z100 (31J/g). Composites 4016E and 4016G showed compressive strengths similar to Z100 (337+/-35Mpa), P>0.05. Discs of composite 4016E, containing Epon 825 oxirane (E), and composite 4016G containing Araldite GY 281 oxirane (G) were non-cytotoxic (-) while the composite 4016GB, containing G and Ebecryl 1830 (B), was mildly (+) cytotoxic to L929 cells in the agar diffusion assay. Seven-day extracts of 4016GB composite were cytotoxic while extracts of 4016E and 4016G were less cytotoxic to L929 cells in the MTT assay. Extracts were obtained from 7 day incubations of composite (3 cm(2) surface area/ml) in acetone or ethanol/saline (1:20) at 37 degrees C. All composite extracts were non-mutagenic to Ames strains TA100, TA98, TA97a and TA1535. The overall results with composite 4016GB suggest that leachable components were cytotoxic but non-mutagenic. With the exception of oxirane components, G and E, the oxirane Cyracure UVR-6105 and other components were non-mutagenic. From cytotoxicity studies, the photoinitiator, Sarcat CD 1012, was the most cytotoxic (TC(50)=14 microM) component. Components G (TC(50)=17 microM), E (TC(50)=50 microM) and B (TC(50)=151 microM) were significantly (p < 0.05) more cytotoxic than Cyracure UVR-6105 (1488 microM) and the polyol, pTHF-250 (TC(50)=6072 microM). SIGNIFICANCE: Favorable results obtained with composites 4016G and 4016E indicates that suitable oxirane/polyol formulations can be designed and optimized for development of dental composites with acceptable mechanical properties and biocompatibility. However, leachable analysis of extracts obtained from longer incubation periods is needed before final conclusions could be drawn about the leachability of oxirane components.

Opioid blockade improves human recognition memory following physiological arousal.

RATIONALE: States of heightened emotion and arousal, such as those that may occur during crimes or traumatic accidents, can impair human memory. Animal models suggest that such memory alterations may be mediated by opioid neuropeptides. In some experimental paradigms, opioid blockade reverses memory impairments related to arousal. OBJECTIVES: The present study evaluated the hypothesis that, under conditions of heightened arousal, opioid blockade would enhance memory in human subjects. METHODS: Memory for story information was evaluated among subjects randomized to one of four study groups (two orthogonal study conditions): (1) no arousal+no opioid blockade, (2) no arousal+opioid blockade, (3) arousal+no opioid blockade, and (4) arousal+opioid blockade. Both free recall and recognition memory were assessed. Opioid receptor blockade was achieved using a single oral dose of naltrexone. RESULTS: With heightened arousal, subjects receiving naltrexone performed better than those receiving placebo on tests of total and incidental recognition memory. In contrast, with emotionally neutral stimuli, naltrexone subjects performed worse than placebo subjects. CONCLUSIONS: These findings demonstrate that opioid peptides mediate alterations in specific aspects of human memory during heightened emotional states, and help to explain why memories may be selectively deficient under conditions of stress.

The role of convexity in perceptual completion: beyond good continuation.

Since the seminal work of the Gestalt psychologists, there has been great interest in understanding what factors determine the perceptual organization of images. While the Gestaltists demonstrated the significance of grouping cues such as similarity, proximity and good continuation, it has not been well understood whether their catalog of grouping cues is complete--in part due to the paucity of effective methodologies for examining the significance of various grouping cues. We describe a novel, objective method to study perceptual grouping of planar regions separated by an occluder. We demonstrate that the stronger the grouping between two such regions, the harder it will be to resolve their relative stereoscopic depth. We use this new method to call into question many existing theories of perceptual completion (Ullman, S. (1976). Biological Cybernetics, 25, 1-6; Shashua, A., & Ullman, S. (1988). 2nd International Conference on Computer Vision (pp. 321-327); Parent, P., & Zucker, S. (1989). IEEE Transactions on Pattern Analysis and Machine Intelligence, 11, 823-839; Kellman, P. J., & Shipley, T. F. (1991). Cognitive psychology, Liveright, New York; Heitger, R., & von der Heydt, R. (1993). A computational model of neural contour processing, figure-ground segregation and illusory contours. In Internal Conference Computer Vision (pp. 32-40); Mumford, D. (1994). Algebraic geometry and its applications, Springer, New York; Williams, L. R., & Jacobs, D. W. (1997). Neural Computation, 9, 837-858) that are based on Gestalt grouping cues by demonstrating that convexity plays a strong role in perceptual completion. In some cases convexity dominates the effects of the well known Gestalt cue of good continuation. While convexity has been known to play a role in figure/ground segmentation (Rubin, 1927; Kanizsa & Gerbino, 1976), this is the first demonstration of its importance in perceptual completion.

Stochastic completion fields; a neural model of illusory contour shape and salience.

We describe an algorithm- and representation-level theory of illusory contour shape and salience. Unlike previous theories, our model is derived from a single assumption: that the prior probability distribution of boundary completion shape can be modeled by a random walk in a lattice whose points are positions and orientations in the image plane (i.e., the space that one can reasonably assume is represented by neurons of the mammalian visual cortex). Our model does not employ numerical relaxation or other explicit minimization, but instead relies on the fact that the probability that a particle following a random walk will pass through a given position and orientation on a path joining two boundary fragments can be computed directly as the product of two vector-field convolutions. We show that for the random walk we define, the maximum likelihood paths are curves of least energy, that is, on average, random walks follow paths commonly assumed to model the shape of illusory contours. A computer model is demonstrated on numerous illusory contour stimuli from the literature.

Gallium scintigraphy in the diagnosis and total lymphoid irradiation of Takayasu's arteritis.

Takayasu's arteritis (TA) in children causes appreciable morbidity and mortality, predominantly as a result of the complication of renovascular hypertension (RVH). Ten children with TA, complicated by RVH, were treated at our centre over the past decade. An initial raised erythrocyte sedimentation rate (ESR) and a purified protein derivative greater than 15 mm were present in every case. More recently, gallium scintigraphy has been used to demonstrate sites of active inflammation in affected vessels (3/4 patients) which became negative after total lymphoid irradiation (TLI). The latter was used in the last 6 children, and appeared to be effective in controlling disease activity as evinced in the normalisation of their ESRs and negative findings on gallium scintigraphy (in all 3 patients with prior active inflammation). Because of vascular damage caused by the vasculitic process, surgical intervention is often required to improve organ perfusion, particularly of the kidney/s. Renal autografting (or allografting) seems preferable (6/11 kidneys functional) to renal bypass grafting (5/5 kidneys clotted). Patient survival improved when TLI was used in addition to standard surgical and medical therapy; this included steroids and antituberculous therapy with TLI, and steroids and cyclophosphamide in the two relapses. Five of 6 patients treated with TLI were alive after 32-54 months' follow-up, while 4 patients who received standard medical and surgical therapy but not TLI all died within 18 months of diagnosis. Gallium scintigraphy is a helpful diagnostic tool in assessing vasculitic activity in TA; TLI is an important mode of immunosuppression, but still needs to be compared with cyclophosphamide as the major immunosuppressive.

Evaluation of urinary tract infection in malnourished black children.

Urinary tract infection (UTI) is a well recognized complication in malnourished children. The need to investigate these patients for underlying renal pathology has not been clearly defined. Seventy-five children with malnutrition were evaluated for UTI by culture of urine obtained suprapubically prior to antibiotic therapy. All patients with UTI were investigated with renal ultrasonography, intravenous pyelography (IVP) and voiding cystourethrography (VCU). Haemoglobin, white cell count, serum urea, creatinine and electrolytes were determined in all the children. The mean age of the children was 15.5 months (range 3-60 months). UTI was diagnosed in 26 (34.7%), of whom 21 (81%) were boys. The overall prevalence of UTI in those with kwashiorkor/marasmic kwashiorkor was 42%. Escherichia coli was the organism most commonly cultured (84.6%). Renal sonography, IVP and VCU were normal in all infected cases and vesicoureteric reflux was not detected in any. This study confirms the high prevalence of UTI in malnourished children. As no anatomical abnormalities were demonstrated in the patients with UTI, imaging of the renal tract other than real sonography does not appear to be indicated in the malnourished child in a first episode of UTI with normal renal function.

Skeletal manifestations of primary oxalosis.

We describe the clinical, radiographic and histological features of skeletal involvement in four patients with end-stage renal failure due to primary oxalosis. The clinical features were unrelenting bone pain, and in two patients multiple fractures. Radiographic features were, in chronological order: (1) radiodense metaphyses and other red marrow bone; (2) cortical defects in metaphyses; (3) spontaneous fracture-separations of epiphyses of long limb bones which healed poorly. The fractures occurred through crystal deposits, and fracture displacement was associated with extrusion of crystalline material from bone. On histological examination crystals were found to replace metaphyseal bone. Pericrystalline giant cell granulomata replaced bone marrow. Erosion surfaces near granulomas were increased. Subperiosteal and intra-osseous tophi of calcium oxalate were seen. Calcium oxalate appears to precipitate with greater facility than does physiological mineral. Bone showed the features of mixed uraemic osteodystrophy in all four patients. We conclude that: (1) the fractures occurred through heavy crystal deposits; (2) ununited fractures and intra-osseous and subperiosteal tophi contributed to the pain; (3) spontaneous fractures are of poor prognostic significance. We recommend that unstable fractures be internally fixed.

Management of severe hypertension in childhood Takayasu's arteritis.

Six children presented with severe hypertension caused by Takayasu's arteritis (TA), of whom four had bilateral renal artery narrowing and two coarctation syndrome. Two presented with hypertensive encephalopathy and four with congestive cardiac failure. All had a strongly positive skin reactions to purified protein derivative of mycobacterium tuberculosis. Bilateral renal arterial bypass grafts performed in two children resulted in prolonged normalization of their blood pressures, but the grafts clotted 12-18 months later. Primary renal autotransplantation was unsuccessful in two children, one with bilateral renal arterial narrowing and iliac vessel involvement and one with a long coarctation. Secondary renal autotransplantation was successful in a third child with localized aortitis. A successful aortic patch graft was performed in one child with coarctation of the aorta. Angiotensin-converting-enzyme inhibitors should be used with caution in treating the hypertension caused by TA, since bilateral renal arterial narrowing is common and their administration may result in renal insufficiency. The long-term prognosis is guarded in severely hypertensive children with extensive vascular disease due to TA.

Ultrastructure of the mesothelioma of the atrioventricular node.

In order to determine the histogenesis of tumors of the atrioventricular node, so-called conduction tumors, two such tumors were serially blocked for electron microscopy. Ultrastructurally these tumors were composed of nests of cells arranged in small channels and tubules set in a connective tissue stroma. The cells lining the tubules were flattened or low cuboidal and had abundant microvilli over the lumen surface. The cells were joined by specialized junctions along their lateral adjacent borders, especially at the luminal surfaces, and intercellular spaces delineated by specialized junctions were frequent. Microvilli, intercellular spaces bounded by tight junctions, and complex intercellular junctions are features of mesothelial cells, and especially of benign mesothelioma of the genital tract. These results strongly suggest that the cardiac conduction tumor is derived from mesothelial cells and is in fact a mesothelioma of the atrioventricular node.