Ultrastructural evidence for communication between intramuscular vagal mechanoreceptors and interstitial cells of Cajal in the rat fundus.

To assess whether afferent vagal intramuscular arrays (IMAs), putative gastrointestinal mechanoreceptors, form contacts with interstitial cells of Cajal of the intramuscular type (ICC-IM) and to describe any such contacts, electron microscopic analyses were performed on the external muscle layers of the fundus containing dextran-labelled diaminobenzidin (DAB)-stained IMAs. Special staining and embedding techniques were developed to preserve ultrastructural features. Within the muscle layers, IMA varicosities were observed in nerve bundles traversing major septa without contact with ICC-IM, contacting unlabelled neurites and glial cells. IMA varicosities were encountered in minor septa in contact with ICC-IM which were not necessarily in close contact with muscle cells. In addition, IMA varicosities were observed within muscle bundles in close contact with ICC-IM which were in gap junction contact with muscle cells. IMAs formed varicosities containing predominantly small agranular vesicles, occasionally large granular vesicles and prejunctional thickenings in apposition to ICC-IM processes, indicating communication between ICC and IMA via synapse-like contacts. Taken together, these different morphological features are consistent with a hypothesized mechanoreceptor role for IMA-ICC complexes. Intraganglionic laminar ending varicosities contacted neuronal somata and dendrites in the myenteric plexus of the fundus, but no contacts with ICC associated with Auerbach's plexus were encountered.

Activating mutations in NOTCH1 in acute myeloid leukemia and lineage switch leukemias.

Activating mutations in NOTCH1 are found in over 50% of human T-cell lymphoblastic leukemias (T-ALLs). Here, we report the analysis for activating NOTCH1 mutations in a large number of acute myeloid leukemia (AML) primary samples and cell lines. We found activating mutations in NOTCH1 in a single M0 primary AML sample, in three (ML1, ML2 and CTV-1) out of 23 AML cell lines and in the diagnostic (myeloid) and relapsed (T-lymphoid) clones in a patient with lineage switch leukemia. Importantly, the ML1 and ML2 AML cell lines are derived from an AML relapse in a patient initially diagnosed with T-ALL. Overall, these results demonstrate that activating mutations in NOTCH1 are mostly restricted to T-ALL and are rare in AMLs. The presence of NOTCH1 mutations in myeloid and T-lymphoid clones in lineage switch leukemias establishes the common clonal origin of the diagnostic and relapse blast populations and suggests a stem cell origin of NOTCH1 mutations during the molecular pathogenesis of these tumors.

Characterization of hereditary nonpolyposis colorectal cancer families from a population-based series of cases.

BACKGROUND: The incidence of hereditary nonpolyposis colon cancer (HNPCC) in the general population is not well defined because of the lack of large population-based studies. We characterized the incidence of HNPCC in a large, population-based cohort of colorectal cancer probands and analyzed the location of colorectal tumors. METHODS: Of the participating 1134 probands from three counties in Southern California, 907 had a negative family history of colorectal cancer and 227 had a positive family history of colorectal cancer. In addition, 11 referral case subjects with HNPCC were used to study mutation frequencies in two mismatch repair genes (MSH2 and MLH1) and microsatellite instability. All statistical tests were two-sided. RESULTS: Among the probands diagnosed in Orange County during 1994 (population-based sample, all ages), five were consistent with the Amsterdam criteria for HNPCC (0.9%; 95% confidence interval [CI] = 0. 3%-2.1%). Among probands diagnosed at less than 65 years of age-from the wider three-county area and a longer time span-16 (2.1%; 95% CI = 1.2%-3.4%) had a clinical history consistent with the Amsterdam criteria for HNPCC. Five (approximately 45%) of 11 of the referral HNPCC case subjects had a mutation in MSH2 or MLH1 and also showed microsatellite instability. The family members of case subjects with mutations tended to show an earlier age at diagnosis of HNPCC and more multiple primary cancers than those of case subjects without detectable mutations. Many of the known characteristics of HNPCC, including the presence of ureteral and endometrial cancers, were seen in both sets of families. The previously reported proximal location of colorectal tumors in HNPCC kindreds was not seen in the population-based dataset but was similar to the location reported in the referral cases. CONCLUSIONS: On the basis of our data, we believe that the prevalence of HNPCC in the general population is likely to be closer to 1% than to 5%. Furthermore, our study suggests that some previously reported characteristics of HNPCC, such as the proximal location of tumors in the syndrome, may not always hold true in a population-based sample.

Highly selective isolation of unknown mutations in diverse DNA fragments: toward new multiplex screening in cancer.

Cancer research would greatly benefit from technologies that allow simultaneous screening of several unknown gene mutations. Lack of such methods currently hampers the large-scale detection of genetic alterations in complex DNA samples. We present a novel mismatch-capture methodology for the highly efficient isolation and amplification of mutation-containing DNA from diverse nucleic acid fragments of unknown sequence. To demonstrate the potential of this method, heteroduplexes with a single A/G mismatch are formed via cross-hybridization of mutant (T-->G) and wild-type DNA-fragment populations. Aldehydes are uniquely introduced at the position of mismatched adenines via the Escherichia coli glycosylase, MutY. Subsequent treatment with a biotinylated hydroxylamine results in highly specific and covalent biotinylation of the site of mismatch. For PCR amplification, synthetic linkers are then ligated to the DNA fragments. Biotinylated DNA is then isolated and PCR amplified. Mutation-containing DNA fragments can subsequently be sequenced to identify type and position of mutation. This method correctly detects a single T-->G transversion introduced into a 7-kb plasmid containing full-length cDNA from the p53 gene. In the presence of a high excess wild-type DNA (1:1000 mutant:normal plasmids) or in the presence of diverse DNA fragment sizes, the DNA fragments containing the mutation are readily detectable and can be isolated and amplified. The present Aldehyde-Linker-Based Ultrasensitive Mismatch Scanning has a current limit of detection of one base substitution in 7 Mb of DNA and increases the limit for unknown mutation scanning by two to three orders of magnitude. Homozygous and heterozygous p53 regions (G-->T, exon 4) from genomic DNA are also examined, and correct identification of mutations is demonstrated. This method should allow large-scale detection of genetic alterations in cancer samples without any assumption as to the genes of interest.

Germ-line msh6 mutations in colorectal cancer families.

Hereditary nonpolyposis colorectal carcinoma (HNPCC) is due primarily to inherited mutations in two mismatch repair genes, MSH2 and MLH1, whereas germ-line mutations in other mismatch repair genes are rare. We examined the frequency of germ-line msh6 mutations in a population-based series of 140 colorectal cancer patients, including 45 sporadic cases, 91 familial non-HNPCC cases, and 4 HNPCC cases. Among the 91 population-based familial non-HNPCC cases, germ-line msh6 mutations were found in 6 patients (7.1% of probands analyzed; median age at diagnosis, 61 years). These mutations included a splice site mutation, a frameshift mutation, two missense mutations that were demonstrated to be loss of function mutations, and two missense mutations for which functional studies were not possible. In contrast, germ-line msh6 mutations were not found in any of the 45 sporadic cases and the 4 HNPCC cases in the population-based series or in the second series of 58 clinic-based, primarily HNPCC families. Our data suggest that germ-line msh6 mutations predispose individuals to primarily late-onset, familial colorectal carcinomas that do not fulfill classic criteria for HNPCC.

Neurotrophin-4 deficient mice have a loss of vagal intraganglionic mechanoreceptors from the small intestine and a disruption of short-term satiety.

Intraganglionic laminar endings (IGLEs) and intramuscular arrays (IMAs) are the two putative mechanoreceptors that the vagus nerve supplies to gastrointestinal smooth muscle. To examine whether neurotrophin-4 (NT-4)-deficient mice, which have only 45% of the normal number of nodose ganglion neurons, exhibit selective losses of these endings and potentially provide a model for assessing their functional roles, we inventoried IGLEs and IMAs in the gut wall. Vagal afferents were labeled by nodose ganglion injections of wheat germ agglutinin-horseradish peroxidase, and a standardized sampling protocol was used to map the terminals in the stomach, duodenum, and ileum. NT-4 mutants had a substantial organ-specific reduction of IGLEs; whereas the morphologies and densities of both IGLEs and IMAs in the stomach were similar to wild-type patterns, IGLEs were largely absent in the small intestine (90 and 81% losses in duodenum and ileum, respectively). Meal pattern analyses revealed that NT-4 mutants had increased meal durations with solid food and increased meal sizes with liquid food. However, daily total food intake and body weight remained normal because of compensatory changes in other meal parameters. These findings indicate that NT-4 knock-out mice have a selective vagal afferent loss and suggest that intestinal IGLEs (1) may participate in short-term satiety, probably by conveying feedback about intestinal distension or transit to the brain, (2) are not essential for long-term control of feeding and body weight, and (3) play different roles in regulation of solid and liquid diet intake.

Sensitivity and specificity of clinical criteria for hereditary non-polyposis colorectal cancer associated mutations in MSH2 and MLH1.

BACKGROUND AND AIMS: There are multiple criteria for the clinical diagnosis of hereditary non-polyposis colorectal cancer (HNPCC). The value of several of the newer proposed diagnostic criteria in identifying subjects with mutations in HNPCC associated mismatch repair genes has not been evaluated, and the performance of the different criteria have not been formally compared with one another. METHODS: We classified 70 families with suspected hereditary colorectal cancer (excluding familial adenomatous polyposis) by several existing clinical criteria for HNPCC, including the Amsterdam criteria, the Modified Amsterdam criteria, the Amsterdam II criteria, and the Bethesda criteria. The results of analysis of the mismatch repair genes MSH2 and MLH1 by full gene sequencing were available for a proband with colorectal neoplasia in each family. The sensitivity and specificity of each of the clinical criteria for the presence of MSH2 and MLH1 mutations were calculated. RESULTS: Of the 70 families, 28 families fulfilled the Amsterdam criteria, 39 fulfilled the Modified Amsterdam Criteria, 34 fulfilled the Amsterdam II criteria, and 56 fulfilled at least one of the seven Bethesda Guidelines for the identification of HNPCC patients. The sensitivity and specificity of the Amsterdam criteria were 61% (95% CI 43-79) and 67% (95% CI 50-85). The sensitivity of the Modified Amsterdam and Amsterdam II criteria were 72% (95% CI 58-86) and 78% (95% CI 64-92), respectively. Overall, the most sensitive criteria for identifying families with pathogenic mutations were the Bethesda criteria, with a sensitivity of 94% (95% CI 88-100); the specificity of these criteria was 25% (95% CI 14-36). Use of the first three criteria of the Bethesda guidelines only was associated with a sensitivity of 94% and a specificity of 49% (95% CI 34-64). CONCLUSIONS: The Amsterdam criteria for HNPCC are neither sufficiently sensitive nor specific for use as a sole criterion for determining which families should undergo testing for MSH2 and MLH1 mutations. The Modified Amsterdam and the Amsterdam II criteria increase sensitivity, but still miss many families with mutations. The most sensitive clinical criteria for identifying subjects with pathogenic MSH2 and MLH1 mutations were the Bethesda Guidelines; a streamlined version of the Bethesda Guidelines may be more specific and easier to use in clinical practice.

Morphology of identified preganglionic neurons in the dorsal motor nucleus of the vagus.

To determine the degree of variation of neuronal morphology both within and between the subnuclei of the dorsal motor nucleus of the vagus (dmnX), structural features of the preganglionic neurons of each of the five primary subnuclei in the rat dmnX were characterized quantitatively. Each of the columnar subnuclei was separately labeled by application of the retrograde tracer fast blue to its corresponding subdiaphragmatic vagal branch. Fixed brain slices of 100 microns thickness were then prepared in coronal, sagittal, and horizontal orientations. Next, randomly selected fast blue labeled neurons (n = 1,256) were injected with Lucifer yellow, drawn with camera lucida, and digitized. For each cell, three features of the perikaryon and twelve of the dendritic tree were measured. Dorsal motor nucleus neurons with up to eight primary dendrites, 30 dendritic segments, and seventh order dendritic branches were observed. Throughout the dmnX, the dendrites of preganglionic neurons were preferentially oriented in the horizontal plane. Consistent with an organizing role for the columnar subnuclei, most dendrites remained within their column of origin. However, between 5 and 30% of the neurons in each of the columns projected dendrites into adjacent dmnX subnuclei or other brainstem nuclei, including the nucleus of the solitary tract (NTS). The cyto- and dendroarchitectural analyses revealed systematic gradations in morphology, although they did not support the idea that the dmnX was composed of multiple distinct preganglionic types. The most parsimonious interpretation of the data is that dmnX motorneurons are variants of a single prototype, with dendrites varying widely in length and degree of ramification. The extent of an individual preganglionic neuron's dendritic field was predicted by three factors: the cell's rostrocaudal position within the dmnX, its location within a transverse plane (i.e., its coronal position within or ectopic to the dmnX), and its subnucleus of origin. Neurons at rostral and midlongitudinal levels of each column had more extensive dendritic arbors than those at caudal levels. Ectopic neurons had more extensive dendritic fields than similar cells in the corresponding columns; in fact, of all vagal preganglionic neurons, ectopics had the most extensive dendritic fields. Somata and dendrites of celiac column neurons were more extensive than those of hepatic and gastric column cells. These differential regional distributions of vagal preganglionics suggest that their structure and function are correlated.

Vagal afferent innervation of smooth muscle in the stomach and duodenum of the mouse: morphology and topography.

Intraganglionic laminar endings (IGLEs) and intramuscular arrays (IMAs), the two putative mechanoreceptors that the vagus nerve supplies to the gastrointestinal smooth muscle, have been characterized almost exclusively in the rat. To provide normative inventories of these afferents for the mouse, the authors examined the endings in the stomach and small intestine of three strains used as backgrounds for gene manipulations (i.e., C57, 129/SvJ, and WBB6). Animals received nodose ganglion injections of wheat germ agglutinin-horseradish peroxidase or dextran-tetramethylrhodamine conjugated to biotin. The horseradish peroxidase tissue was processed with tetramethylbenzidine and was used to map the distributions and densities of the two endings; the dextran material was counterstained with c-Kit immunohistochemistry to assess interactions between intramuscular arrays and interstitial cells of Cajal. IGLEs and IMAs constituted the vagal innervation of mouse gastric and duodenal smooth muscle. IGLE morphology and distributions, with peak densities in the corpus-antrum, were similar in the three strains of mice and comparable to those observed in rats. IMAs varied in complexity from region to region but tended to be simpler (fewer telodendria) in mice than in rats. IMAs were most concentrated in the forestomach and sphincters in mice, as in rats, but the topographic distributions of the endings varied both between strains of mice (subtly) and between species (more dramatically). IMAs appeared to make appositions with both interstitial cells and smooth muscle fibers. This survey should make it practical to assay the effects of genetic (e.g., knockout) and experimental (e.g., regeneration) manipulations affecting visceral afferents and their target tissues.

T-cell blast crisis in chronic myelogenous leukemia. Immunophenotypic and molecular biologic findings.

T-cell blast crisis in chronic myelogenous leukemia is rare. We examined three patients (ages 35 to 72 years) in whom T-cell blast crisis developed 11 to 36 months (mean, 25 months) after diagnosis of chronic myelogenous leukemia and who died 4 to 12 months (mean, 7 months) thereafter. Two patients had diffuse lymphadenopathy, and the third had marked lymphocytosis (white blood cell count 217,000/microL, with 90% circulating blasts). In all three patients, neoplastic cells had the appearance of lymphoblasts and were immunoreactive for T-cell markers by immunohistochemical or flow cytometric analysis or both. Molecular diagnostic studies revealed the presence of a bcr-abl oncogene rearrangement in all three cases, but none exhibited a clonal T-cell receptor delta, beta, or gamma chain gene rearrangement. One case exhibited deletion of the J delta 1 region of both delta chain genes. The significance of these findings is discussed, and they are compared with those of other reported cases of T-cell blast crisis in chronic myelogenous leukemia.

A retrograde tracer strategy using True Blue to label the preganglionic parasympathetic innervation of the abdominal viscera.

A simple and reliable method for labeling the preganglionic neurons which innervate the abdominal viscera is described. Infusion of a True Blue (TB) suspension in several different concentrations directly into the peritoneal cavity consistently labeled the medullary vagal nuclei including the dorsal motor nucleus (DMN), nucleus ambiguus (NA), and retrofacial nucleus (RFN). Quantitative analysis of cell labeling after 30 microliters infusions of a large range of concentrations of TB (0.001-20.0%) showed that: (1) as little as 0.0075 mg of TB was sufficient to label DMN cells distinctly while only 0.075 mg (or larger) doses of TB were adequate for labeling cells of the NA and the RFN, and (2) doses of 3.0 mg (or greater) labeled the maximum number of cells in the DMN, NA, and RFN. Qualitative analysis suggested that medium range doses (0.075-0.75 mg) were optimal for discerning cell size and type throughout each of these nuclei.

Ionotropic and metabotropic components of electrophysiological response of cerebellar Purkinje neurons to excitatory amino acids.

Cerebellar Purkinje neurons possess AMPA ((RS)-alpha-amino-3-hydroxyl-5- methyl-4-isoxazolepropionic acid)-sensitive ionotropic glutamate receptors (AMPA GluRs) and ACPD ((1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid)-sensitive metabotropic glutamate receptors (mGluRs). The contributions of these receptors to responses elicited by dual receptor activation in cultured cerebellar Purkinje neurons were delineated by quantitative analysis of agonist-induced single unit activity. Responses to co-activation using Quis or AMPA + ACPD were biphasic, consisting of a dramatic increase in firing rate (excitatory phase) followed by a temporary decrease (inhibitory phase). In half of the cells tested bursting was induced during both the excitatory and inhibitory phases and the duration of each phase was prolonged relative to responses observed in non-bursting cells. Quantitative comparisons of these responses and responses produced by selective activation of AMPA GluRs and mGluRs revealed that: (a) AMPA GluRs mediated the dramatic changes in firing rate, (b) mGluRs mediated the dramatic increases in bursting and the extended duration of each phase and (c) these AMPA GluR and mGluR mediated effects were largely additive when simultaneously activated. Nevertheless, interactions did occur with repeated co-activation of AMPA GluRs and mGluRs, as indicated by selective changes in the mGluR-mediated bursting component of the response. Such modulation may contribute to synaptic regulation of Purkinje neuron excitability, for example, that associated with long term depression.

Longitudinal columnar organization within the dorsal motor nucleus represents separate branches of the abdominal vagus.

To identify the distribution of central preganglionics associated with each branch of the subdiaphragmatic vagus, the fluorescent tracer True Blue (TB) was administered intraperitoneally to rats with 4 out of 5 branches cauterized, and then, after 72 h, the animals were sacrificed for histological analysis. Each vagal branch contained the axons of a topographically distinct column of cells within the dorsal motor nucleus of the vagus (DMN). The columns representing the 4 branches with the largest numbers of efferents are organized as paired, bilaterally symmetrical, longitudinal distributions on either side of the medulla. Each DMN side contains a column occupying the medial two-thirds or more of the nucleus and corresponding to one of the gastric branches (left DMN, anterior gastric; right DMN, posterior gastric). Also on each side, the lateral pole of the DMN consists of a coherent cell column corresponding to one of the celiac branches (left DMN, accessory celiac; right DMN, celiac). The fifth branch, the hepatic, is represented by a limited number of somata forming a diffuse column largely coextensive with that representing the anterior gastric branch. At some levels of the DMN, the columns overlap. Labeled cells observed in the reticular formation were correlated in number, left-right ratios and response to vagotomy with those in the DMN, which suggests that they are displaced cells of the nucleus. Distributions of labeled cells in the nucleus ambiguus and the retrofacial nucleus were not tightly correlated with those of the DMN. An analysis of cell counts obtained for each of the individual branches suggests that vagal axons do not generally send collaterals through more than one branch.

Vagotomy does not alter circannual body weight cycles in the hibernator Citellus lateralis.

To evaluate a hypothesized role of the vagus in the circannual metabolic cycle of hibernators, measures of annual weight gain, weight loss and cycle period were taken for the ground squirrel, Citellus lateralis, maintained in constant environmental conditions before and after subdiaphragmatic vagotomy. The surgery did not alter the peak weights attained, the lowest weights reached, or the period of the circannual cycle.

The previously identified r3/r5 repressor may require the cooperation of additional negative elements for rhombomere restriction of Hoxb1.

Hoxb1 has several rhombomere-specific roles in hindbrain development and may contribute to development of a small number of tissues outside the hindbrain. To gain insight into the regulation of late Hoxb1 expression in these structures, several regions of the Hoxb1 locus were systematically evaluated for their ability to control late Hoxb1 expression in transgenic mouse embryos. This was achieved by progressive enlargement of the portion of the Hoxb1 locus used to control reporter gene expression. Unexpectedly, the previously identified rhombomere 4 (r4) enhancer and r3/r5 repressor that were thought to be sufficient for r4 restriction of Hoxb1 produced continuous expression throughout much of the length of the central nervous system (CNS) and in several structures outside the nervous system. However, adjacent regions of the Hoxb1 locus, in combination with the r4 enhancer and r3/r5 repressor were capable of restricting most expression to r4 in the hindbrain, and to gut epithelium/mesoderm, caudal spinal cord and caudal paraxial mesoderm outside the hindbrain. Expression that occurred outside r4 in the brains of the majority of founder embryos was confined to scattered cells in specific regions. These cells may have arisen in r4 and then migrated into adjacent brain regions as rhombomere lineage restrictions dissipated. Alternatively, these dispersed stained cells may have originated outside r4 implying that Hoxb1 cannot be accurately regulated in a consistent manner outside the Hox complex.

Corticotropin-releasing factor suppresses the afterhyperpolarization in cerebellar Purkinje neurons.

Corticotropin-releasing factor (CRF) is present in climbing fibers and their terminations on Purkinje neurons. To determine whether CRF may have a postsynaptic action in this pathway, CRF effects on the electrophysiological properties of cultured cerebellar Purkinje neurons were studied. CRF produced a dose-dependent reduction of the amplitude of the afterhyperpolarization (AHP) which follows a current-induced spike train. The effect of CRF on the AHP was specific in that CRF did not significantly alter input resistance, membrane potential, amplitude of the depolarizing-off response produced at the termination of a hyperpolarizing current pulse, or the number of depolarization-induced simple spikes. Suppression of the AHP by CRF may be one mechanism by which CRF regulates the response of Purkinje neurons to other transmitters in the climbing fiber pathway or in other inputs to Purkinje neurons.

Empathy in clinical dietitians and dietetic interns.

On the premise that empathy is important in patient care and nutrition counseling, the empathy levels of 217 clinical dietitians and 168 dietetic interns were measured using the Davis Interpersonal Reactivity Index. The Interpersonal Reactivity Index is designed to measure four aspects of empathy: empathic concern (EC), fantasy (FS), personal distress (PD), and perspective-taking (PT). Personal and professional characteristics were surveyed to determine possible influence on empathy. The instrument was mailed to 26 randomly selected internship programs. All of the dietetic interns and clinical dietitians who spend 80% of their time in patient care were requested to participate. The mean ages of the dietitians and interns were 35 and 25 years, respectively. Interns scored significantly higher on the EC (29.06, p less than .05) and FS (24.65, p less than .0005) scales than the dietitians (EC = 28.20, FS = 22.53). There was a highly significant negative correlation (r = -0.26, p less than .0001) between fantasy and age for dietitians and interns and between fantasy and experience for the dietitians (r = -0.23, p less than .0005). Dietitians and interns who had had graduate coursework in counselling, psychology, and/or educational psychology had significantly lower mean scores on the PD (17.14, p less than .05) and EC (27.82, p less than .05) scales and a significantly higher mean score on the PT (27.06, p less than .05) scale. Responses to an opinion question indicated that the mean for ideal percentage of time spent in direct patient contact was 70.1 for dietitians and 61.4 for interns, a highly significant difference (p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

C-Kit mutant mice have a selective loss of vagal intramuscular mechanoreceptors in the forestomach.

Intramuscular arrays are one of two major classes of vagal afferent mechanoreceptors that innervate the smooth muscle wall of the proximal gastrointestinal tract. They consist of rectilinear telodendria that distribute in the muscle sheets, parallel to the long axes of muscle fibers. Intramuscular arrays appear to make direct contact with the muscle fibers, but they also course on, and form appositions with, intramuscular interstitial cells of Cajal. These complexes formed by intramuscular arrays and intramuscular interstitial cells of Cajal suggest that intramuscular arrays might require either structural or trophic support of the interstitial cells of Cajal for normal differentiation and/or maintenance. To evaluate this hypothesis, we have examined the morphology and distribution of vagal afferent endings in the c-Kit mutant mouse that lacks intramuscular interstitial cells of Cajal. Vagal afferents were labeled by nodose ganglion injection of either wheat germ agglutinin-horseradish peroxidase conjugate or a tagged dextran, and the labeled afferent terminals in the stomach were mapped using a standardized quantitative sampling scheme. Intramuscular arrays were dramatically reduced (in circular muscle by 63%; in longitudinal muscle by 78%) in the c-Kit mutant mice relative to their wild-type littermates. Additionally, a substantial number of the surviving axons and terminals in the mutant stomachs were morphologically aberrant. Moreover, the loss of intramuscular arrays in mutants appeared to be selective: the structure, distribution and density of intraganglionic laminar endings, i.e., the other vagal mechanoreceptors in smooth muscle, were not significantly altered. Finally, the conspicuous decrease in intramuscular array density in mutants was associated with a non-significant trend toward loss of nodose ganglion neurons. Collectively these findings suggest that interstitial cells are required for the normal development or maintenance of vagal intramuscular arrays. Therefore, the c-Kit mutant mouse will be valuable for determining the role(s) of interstitial cells in intramuscular array development as well as for providing an animal model with the intramuscular array class of vagal afferents selectively ablated.

Accurate, high-throughput "snapshot" detection of hMLH1 mutations by two-dimensional DNA electrophoresis.

The human genome and related projects have resulted in the isolation of a rapidly growing number of genes that cause susceptibility to human cancer. With rare exception, these genes are large and have disease-associated mutations scattered along the length of the genes. Therefore, the development of accurate and cost-efficient mutation detection tests that can scan entire genes singly or in combination is warranted. hMLH1, encoding a mismatch repair enzyme, is a susceptibility gene for hereditary nonpolyposis colon cancer syndrome. This gene comprises 19 exons; mutations are scattered, typical of many susceptibility genes. Here, we present a strategy that combines extensive PCR multiplexing and two-dimensional DNA electrophoresis (Two-Dimensional Gene Scanning, TDGS) to scan accurately for mutations that lie within the exons and splice junctions of hMLH1. All target fragments, designed to have optimal melting characteristics, were prepared in a two-stage PCR--a four-plex long-distance PCR followed by short PCR in two multiplex groups of 10 and 11 amplicons. The mixture of amplicons was subjected to two-dimensional electrophoresis: separation by size in the first dimension and by melting characteristics in the second. Using this design, 41 samples containing known hMLH1 sequence variants or no alterations were blindly subjected to TDGS. All mutations were detected; there were no genuine false-positive or false-negative results. These results confirm that TDGS is a generally applicable, rapid, accurate, and reproducible mutation detection technology that would serve large-scale molecular epidemiologic studies as well as clinical molecular diagnostic purposes.

Comparison of functional testing for resistance to activated protein C and molecular biological testing for factor V R506Q in 370 patients.

OBJECTIVE: To compare functional and molecular biological tests for resistance to activated protein C (APC)/factor V R506Q, the most common cause of familial thrombosis. METHODS: We developed functional and molecular biological tests for resistance to APC/factor V R506Q at our institution and correlated the results for 370 patients studied by both methods. The functional method is based on addition of exogenous APC to an activated partial thromboplastin time-based assay. The molecular biological method is based on polymerase chain reaction followed by endonuclease digestion. RESULTS: Considering the molecular biological test as definitive for detecting the factor V R506Q mutation, the sensitivity of the functional assay was 100%, and the specificity was 74%. The prevalence of the factor V mutation in the population studied was 12% (41 heterozygotes, two homozygotes), and the positive predictive value of the functional assay was 34%. Although a normalized sensitivity ratio (nAPC-SR) less than 0.84 is considered evidence of resistance to APC by functional testing, we found that all patients with factor V R506Q had an nAPC-SR less than or equal to 0.71. When this alternative positive cutoff was used, the specificity of the functional test for factor V R506Q increased to 87%, and the positive predictive value increased to 52%, which constituted a significant improvement. We compared clinical findings from patients with resistance to APC with or without the presence of factor V R506Q, and found that as a group, those with factor V R506Q had a higher incidence of hypercoagulability, but fewer additional risk factors for hypercoagulability. The mechanism of resistance to APC in factor V R506Q-negative individuals is unclear, but may be related to other risk factors for hypercoagulability. CONCLUSIONS: The functional assay for resistance to APC is an excellent screening test for factor V R506Q, but confirmatory molecular biological testing is necessary when the functional test is positive, because of the high false-positive rate.