Comparison of the spatial distribution of seven types of neuroendocrine neurons in the rat paraventricular nucleus: toward a global 3D model.

The paraventricular nucleus of the hypothalamus (PVH) coordinates neuroendocrine, autonomic, and behavioral responses to help maintain energy and body water balance. The rat paraventricular nucleus has three major divisions: descending with axonal projections to somatomotor-behavioral and autonomic circuitry, magnocellular neuroendocrine with projections directly to the posterior pituitary, and parvicellular neuroendocrine with projections to the median eminence for controlling anterior pituitary hormone secretion. The present work was undertaken to provide high-resolution mapping of spatial relationships among the two magnocellular neuroendocrine and five parvicellular neuroendocrine neuron types throughout the nucleus. Double immunohistochemical labeling for two neuron types combined with retrograde labeling to identify neuroendocrine neurons positively was used in individual sections spaced 45 mum apart, along with a grid transfer method for reducing plane of section artifacts when comparing staining pattern data between animals. The results indicate that whereas each neuroendocrine neuron phenotype displays a unique distribution pattern, there is extensive partial overlap in a complex pattern between small "hot spots" with a relatively high density of a particular neuron type and few if any other phenotypes. In addition, the distribution of non-neuroendocrine neurons staining with each of the markers (but not retrogradely labeled) was mapped and compared with each other and with the neuroendocrine neuron populations. This spatial organization raises important questions about the differential functional regulation of individual-and perhaps sets of-neuroendocrine motor neuron populations in the PVH by synaptic mechanisms and by less traditional mechanisms like dendritic neurotransmitter release and gap junctions within and between neuron types.

Comparing histological data from different brains: sources of error and strategies for minimizing them.

The recent development of brain atlases with computer graphics templates, and of huge databases of neurohistochemical data on the internet, has forced a systematic re-examination of errors associated with comparing histological features between adjacent sections of the same brain, between brains treated in the same way, and between brains from groups treated in different ways. The long-term goal is to compare as accurately as possible a broad array of data from experimental brains within the framework of reference atlases. Main sources of error, each of which ideally should be measured and minimized, include intrinsic biological variation, linear and nonlinear distortion of histological sections, plane of section differences between each brain, section alignment problems, and sampling errors. These variables are discussed, along with approaches to error estimation and minimization in terms of a specific example-the distribution of neuroendocrine neurons in the rat paraventricular nucleus. Based on the strategy developed here, the main conclusion is that the best long-term solution is a high-resolution 3D computer graphics model of the brain that can be sliced in any plane and used as the framework for quantitative neuroanatomy, databases, knowledge management systems, and structure-function modeling. However, any approach to the automatic annotation of neuroanatomical data-relating its spatial distribution to a reference atlas-should deal systematically with these sources of error, which reduce localization reliability.

High-resolution paraventricular nucleus serial section model constructed within a traditional rat brain atlas.

As a starting point for constructing a high-resolution, resliceable computer graphics model for the extraction, quantitative analysis, display, and modeling of neuroanatomical data the outer border and the boundaries of inner divisions and parts of the paraventricular nucleus have been drawn for all 39 serial histological sections prepared for a published reference atlas of the rat brain. This careful parceling revealed three new features of paraventricular nucleus topography: the full rostral extent of the anterior parvicellular part, the caudal end of the medial magnocellular part, and a thin rostrolateral extension of the dorsal medial parvicellular part composed at least in part of neurons expressing corticotropin-releasing hormone. The vector graphics drawings were aligned using the already established alignment of nine consecutive, relevant Atlas Levels, and then contours were smoothed to eliminate nonlinear distortions associated with histological mounting. This dataset was then used to create three-dimensional contour and surface models of the paraventricular nucleus, as well as two-dimensional horizontal and sagittal projections of its outer border. The computer graphics files containing raw and smoothed drawings for all 39 serial sections are supplied for use by researchers interested in developing new or better computer graphics analysis tools involving the paraventricular nucleus. This work may also stimulate the long range goal of creating a high-resolution, resliceable, computer graphics model of the whole brain, and eventually the whole nervous system, that is useful for quantitative analysis and topological transformation.

Profound hypokalemia: unusual presentation and management in a 12-year-old boy.

Hypokalemia is a frequent electrolyte abnormality that rarely requires more than oral supplementation to correct. We describe a case of profound hypokalemia and cardiac arrhythmia requiring unusually large amounts of "bolused" potassium to restore to normal sinus rhythm. Our patient presented with significant dehydration and electrolyte abnormalities after several days of emesis. Most alarming of these findings was a serum potassium level of 1.2 mEq/L. The electrocardiogram showed changes consistent with hypokalemia that rapidly degraded into pulseless ventricular tachycardia. Potassium chloride of 140 mEq was hand-pushed during the resuscitation with return of spontaneous rhythm. The patient was discharge 11 days later in his prearrest state.

Initial impact of drug-eluting stent use on the spectrum of patients undergoing percutaneous coronary intervention.

BACKGROUND: The availability of drug-eluting stents was expected to expand the application of percutaneous coronary intervention to a wider group of patients and lesion types. We sought to determine whether drug-eluting stents' availability has changed the practices of operators performing percutaneous coronary intervention with regard to patient selection and procedural factors. METHODS: We compared the clinical and angiographic characteristics of patients who underwent percutaneous coronary intervention at the Methodist Hospital, Houston, Texas, during three periods: June 2002-March 2003, June 2003-March 2004 and June 2004-March 2005. Sirolimus-eluting stents were available during the latter two periods. Paclitaxel eluting stents became available during the third period. RESULTS: A greater proportion of patients undergoing diagnostic catheterization were referred for percutaneous coronary intervention during the latter two periods (26.8%, 30.4%, 30.4%, respectively, P<0.0001). Patients undergoing stent placement during the latter two periods were more likely to have hypertension, hyperlipidemia or to have undergone previous percutaneous coronary intervention. The average implanted stent length was greater during the latter periods (14.5+/-4.6, 16.4+/-5.2, 16.8+/-5.5 mm, respectively, P<0.0001) and the average stent diameter was smaller (3.23+/-1.22, 3.13+/-1.16, 3.02+/-0.6 mm, respectively, P<0.0001). The frequency of percutaneous coronary intervention involving long lesions (>20 mm) and Left Anterior Descending (LAD) lesions was higher in the latter two periods and the frequency of multivessel stenting was higher in the last period. CONCLUSIONS: The spectrum of patients and coronary lesions that have undergone stenting has changed, particularly in the third period when both drug-eluting stent types were available. We observed a gradual shift toward higher-risk clinical and lesion characteristics following the introduction of drug-eluting stents.

Correlations among applicants' communication apprehension, argumentativeness, and verbal aggressiveness in selection interviews.

This study explored the influence of applicants' perceived apprehension during communication on self-reported argumentativeness and verbal aggressiveness in selection interviews. One week prior to selection interviews with corporate interviewers, 51 college students who were actively seeking career-oriented employment completed a questionnaire on their situational apprehension, trait argumentativeness, and trait verbal aggressiveness. The major findings were that (a) Trait Argumentativeness was significantly and negatively correlated with Trait Verbal Aggressiveness; (b) Apprehension was significantly and positively correlated with Trait Verbal Aggressiveness; (c) Apprehension was significantly and negatively correlated with Trait Argumentativeness; and (d) descriptive statistics indicated applicants experienced high Apprehension before the interviews.