Stimulation of intestinal mucosal adenyl cyclase by cholera enterotoxin and prostaglandins

The effects of several prostaglandins (PG) and a highly purified preparation of cholera enterotoxin (CT) on intestinal mucosal adenyl cyclase activity and the effect of CT on intestinal mucosal cyclic 3',5'-adenosine monophosphate concentration were determined in guinea pig and rabbit small intestine and were correlated with the effects of the same agents on ion transport. Adenyl cyclase activity, measured in a crude membrane fraction of the mucosa, was found at all levels of the small intestine with the highest activity per milligram protein in the duodenum. The prostaglandins, when added directly to the assay, increased adenyl cyclase activity; the greatest effect (2-fold increase) was obtained with PGE(1) (maximal effect at 0.03 mM) and PGE(2). The prostaglandins also increased short-circuit current (SCC) in isolated guinea pig ileal mucosa, with PGE(1) and PGE(2) again giving the greatest effects. The prior addition of theophylline (10 mM) reduced the subsequent SCC response to PGE(1) and vice versa. It was concluded, therefore, that the SCC response to PGE(1), like the response to theophylline, represented active Cl secretion. CT increased adenyl cyclase activity in guinea pig and rabbit ileal mucosa when preincubated with the mucosa from 1 to 2.5 hr in vitro or for 2.5 hr in vivo but not when added directly to the assay. The increments in activity caused by PGE(1) and NaF were the same in CT-treated and control mucosa. Cyclic 3',5'-AMP concentration in rabbit ileal mucosa was increased 3.5-fold after a 2 hr preincubation with CT in vitro. Phosphodiesterase activity in the crude membrane fraction of the mucosa was unaffected by either CT or PGE(1). A variety of other agents including insulin, glucagon, parathormone, thyroid-stimulating hormone, L-thyroxine, thyrocalcitonin, vasopressin, and epinephrine all failed to change adenyl cyclase activity. It is concluded that CT and certain prostaglandins produce small intestinal fluid secretion by increasing mucosal adenyl cyclase activity, thereby stimulating an active secretory process.

Removing batch effects in analysis of expression microarray data: an evaluation of six batch adjustment methods

The expression microarray is a frequently used approach to study gene expression on a genome-wide scale. However, the data produced by the thousands of microarray studies published annually are confounded by “batch effects,” the systematic error introduced when samples are processed in multiple batches. Although batch effects can be reduced by careful experimental design, they cannot be eliminated unless the whole study is done in a single batch. A number of programs are now available to adjust microarray data for batch effects prior to analysis. We systematically evaluated six of these programs using multiple measures of precision, accuracy and overall performance. ComBat, an Empirical Bayes method, outperformed the other five programs by most metrics. We also showed that it is essential to standardize expression data at the probe level when testing for correlation of expression profiles, due to a sizeable probe effect in microarray data that can inflate the correlation among replicates and unrelated samples.

Genome-wide association study of bipolar disorder in European American and African American individuals

To identify bipolar disorder (BD) genetic susceptibility factors, we conducted two genome-wide association (GWA) studies: one involving a sample of individuals of European ancestry (EA; n=1001 cases; n=1033 controls), and one involving a sample of individuals of African ancestry (AA; n=345 cases; n=670 controls). For the EA sample, single-nucleotide polymorphisms (SNPs) with the strongest statistical evidence for association included rs5907577 in an intergenic region at Xq27.1 (P=1.6 x 10(-6)) and rs10193871 in NAP5 at 2q21.2 (P=9.8 x 10(-6)). For the AA sample, SNPs with the strongest statistical evidence for association included rs2111504 in DPY19L3 at 19q13.11 (P=1.5 x 10(-6)) and rs2769605 in NTRK2 at 9q21.33 (P=4.5 x 10(-5)). We also investigated whether we could provide support for three regions previously associated with BD, and we showed that the ANK3 region replicates in our sample, along with some support for C15Orf53; other evidence implicates BD candidate genes such as SLITRK2. We also tested the hypothesis that BD susceptibility variants exhibit genetic background-dependent effects. SNPs with the strongest statistical evidence for genetic background effects included rs11208285 in ROR1 at 1p31.3 (P=1.4 x 10(-6)), rs4657247 in RGS5 at 1q23.3 (P=4.1 x 10(-6)), and rs7078071 in BTBD16 at 10q26.13 (P=4.5 x 10(-6)). This study is the first to conduct GWA of BD in individuals of AA and suggests that genetic variations that contribute to BD may vary as a function of ancestry.

Effect of cortisone treatment on the active transport of calcium by the small intestine

It is generally recognized that glucocorticoid administration may diminish calcium absorption in vivo as well as the active transport of calcium by the intestine in vitro. Recent studies by others have emphasized the possibility of an alteration in the metabolism of vitamin D to 25-hydroxycholecalciferol in accounting for the steroid effects on calcium absorption. The results obtained in the present studies fail to support this hypothesis. The present studies confirm that the administration of cortisone or other glucocorticoids to the rat interferes with the active transport of calcium by duodenal gut sacs in vitro. This abnormality is not due to an alteration in the permeability of the intestine to calcium, and it cannot be corrected by the administration of either massive doses of vitamin D(2) or modest doses of 25-hydroxycholecalciferol. Experiments concerned with the effects of cortisone on the level of the vitamin D-dependent duodenal calcium-binding protein, the amount of bioassayable vitamin D activity in the mucosa, and the distribution and metabolism of (3)H-vitamin D(3), did not provide evidence in favor of a harmone-related defect in either the localization of vitamin D or its metabolism to 25-hydroxycholecalciferol. Alterations in the transport of iron and D-galactose, not dependent on vitamin D, suggest that cortisone treatment may be responsible for more than a simple antagonism to the effects of vitamin D. The results of the present studies indicate that cortisone administration affects the cellular mechanisms mediating calcium transport in a manner that is opposite to the effects of vitamin D, but seems to be independent of any direct interaction with the parent vitamin or its metabolites. If a disorder in vitamin D metabolism is at all involved, it is at a step subsequent to 25-hydroxylation.

A combined analysis of D22S278 marker alleles in affected sib-pairs: support for a susceptibility locus for schizophrenia at chromosome 22q12. Schizophrenia Collaborative Linkage Group (Chromosome 22)

Several groups have reported weak evidence for linkage between schizophrenia and genetic markers located on chromosome 22q using the lod score method of analysis. However these findings involved different genetic markers and methods of analysis, and so were not directly comparable. To resolve this issue we have performed a combined analysis of genotypic data from the marker D22S278 in multiply affected schizophrenic families derived from 11 independent research groups worldwide. This marker was chosen because it showed maximum evidence for linkage in three independent datasets (Vallada et al., Am J Med Genet 60:139-146, 1995; Polymeropoulos et al., Neuropsychiatr Genet 54:93-99, 1994; Lasseter et al., Am J Med Genet, 60:172-173, 1995. Using the affected sib-pair method as implemented by the program ESPA, the combined dataset showed 252 alleles shared compared with 188 alleles not share (chi-square 9.31, 1df, P = 0.001) where parental genotype data was completely known. When sib-pairs for whom parental data was assigned according to probability were included the number of alleles shared was 514.1 compared with 437.8 not shared (chi-square 6.12, 1df, P = 0.006). Similar results were obtained when a likelihood ratio method for sib-pair analysis was used. These results indicate that may be a susceptibility locus for schizophrenia at 22q12.

Effects of feedback and reinforcement on the control of human systolic blood pressure

An automatic procedure providing information about human systolic blood pressure at each successive heartbeat under routine laboratory conditions is described. Twenty normal male subjects were given feedback of their own systolic pressure, half operantly reinforced for increasing and half reinforced for decreasing their pressure. Significant differences in pressure were obtained in a single session. The apparatus and results suggest a possible approach to the treatment of essential hypertension.

Effects of prostaglandins and cholera enterotoxin on intestinal mucosal cyclic AMP accumulation. Evidence against an essential role for prostaglandins in the action of toxin

Both cholera enterotoxin and certain prostaglandins have been shown to stimulate intestinal fluid secretion in vivo, to cause ion flux changes in vitro similar to those caused by addition of cyclic 3',5'-adenosine monophosphate (cyclic AMP), and to activate intestinal mucosal adenyl cyclase. It has been suggested that the effects of the enterotoxin on intestinal cyclic AMP metabolism may be indirect, and that locally synthesized prostaglandins may serve as required intermediates for the effects of the enterotoxin in activating intestinal mucosal adenyl cyclase. In order to clarify certain aspects of the mechanisms by which these two agents alter intestinal mucosal cyclic AMP metabolism and ion transport, their effects on cyclic AMP accumulation in rabbit ileal mucosa were examined in vitro. Addition of 5 mug per ml (75 mug per 150 mg mucosa) of purified cholera enterotoxin produced a peak increase in cyclic AMP level in 3 h but there was a time delay of at least 30 min before any effect was observed. Inhibition of cyclic nucleotide phosphodiesterase with theophylline failed to reduce this time delay. In contrast, addition of prostaglandin E(1) (PGE(1)) increased the cyclic AMP level rapidly, a peak effect being observed in 2 min. The time of the peak prostaglandin-induced changes in cyclic AMP level and short-circuit current correlated closely. A maximal increment in cyclic AMP level was achieved with 5 x 10(-5) M PGE(1). When 10(-4) M PGE(1) was added to mucosa already maximally stimulated with cholera toxin, the resulting cyclic AMP level was equal to the sum of the levels reached when each agent was added alone. Furthermore, the effects of the enterotoxin on mucosal cyclic AMP levels were not influenced by indomethacin under conditions where mucosal prostaglandins synthesis was inhibited. The results suggest that endogenous prostaglandins do not provide an essential link in the activation of intestinal mucosal adenyl cyclase by cholera enterotoxin. The present study also indicates that the effect of cholera enterotoxin on intestinal mucosal cyclic AMP metabolism involves a definite time delay which is not due to cyclic nucleotide phosphodiesterase activity.

Comorbid bipolar disorder and panic disorder in families with a high prevalence of bipolar disorder

OBJECTIVE

Panic attacks are a common complication of affective disorder, although the etiologic relationship of panic and affective symptoms has not been determined. Evidence from a family study suggests that panic attacks and panic disorder may be related genetically to bipolar disorder. This study used diagnostic data from the NIMH Bipolar Disorder Genetics Initiative to assess in a separate, larger family set the familiality of panic combined with bipolar disorder.

METHOD

First-degree relatives (N=966) of probands with bipolar I disorder (N=192) and schizoaffective disorder, bipolar type, (N=11) were included in the study. All subjects were interviewed directly and were assigned best-estimate diagnoses for major affective and other psychiatric disorders. The risk of a family member being diagnosed with panic disorder if the proband with bipolar disorder had panic attacks or panic disorder was calculated with logistic regression analysis with generalized estimating equations that controlled for sex and affective disorder subdiagnosis.

RESULTS

More than 90% of the probands and first-degree relatives with panic disorder also had an affective disorder diagnosis. Panic disorder was present in 17% of the relatives with recurrent major affective disorder and in 3% of the relatives without recurrent major affective disorder. Risk of panic disorder in relatives with bipolar disorder was increased significantly if the proband had panic attacks or panic disorder.

CONCLUSIONS

Risk for panic disorder with familial bipolar disorder appears to be inherited. Inherited risk for panic disorder with bipolar disorder may indicate a shared genetic etiology for both disorders in some families. The patterns of bipolar disorder and panic disorder comorbidity observed in families imply a complex genetic etiology, which may be elucidated by using endophenotypes.

Association of Choroid Plexus Enlargement With Cognitive, Inflammatory, and Structural Phenotypes Across the Psychosis Spectrum

OBJECTIVE

The choroid plexus is an important physiological barrier and produces CSF and neurotrophic, angiogenic, and inflammatory factors involved in brain development. Choroid plexus abnormalities have been implicated in both schizophrenia and bipolar disorder. A previous choroid plexus transcriptomic analysis of schizophrenia identified an upregulation of immune and inflammatory genes that correlated with peripheral inflammatory markers. The purpose of this study was to examine choroid plexus volume in probands across the psychosis spectrum and in their first-degree and axis II cluster A relatives, as well as choroid plexus familiality and choroid plexus covariance with clinical, cognitive, brain, and peripheral marker measures.

METHODS

Choroid plexus volume was quantified (using FreeSurfer) in psychosis probands, their first-degree and axis II cluster A relatives, and healthy control subjects, organized by DSM-IV-TR diagnosis. Analyte, structural connectivity, and genotype data were collected from a subset of study subjects.

RESULTS

Choroid plexus volume was significantly larger in probands compared with first-degree relatives or healthy control subjects; first-degree relatives had intermediate enlargement compared with healthy control subjects; and total choroid plexus volume was significantly heritable. Larger volume was associated with worse cognition, smaller total gray matter and amygdala volume, larger lateral ventricle volume, and lower structural connectivity in probands. Associations between larger volume and higher levels of interleukin 6 in probands was also observed.

CONCLUSIONS

These findings suggest the involvement of the choroid plexus across the psychosis spectrum with a potential pathophysiological mechanism involving the neuroimmune axis, which functions in maintaining brain homeostasis and interacting with the peripheral immune and inflammatory system. The choroid plexus may be an important target in future research.

Supersensitivity to melatonin suppression by light in young people at high risk for affective disorder. A preliminary report

Affective illness aggregates in families and appears to be heritable. Bipolar affective patients have been found to be supersensitive to the suppressive effect of light on the nocturnal secretion of melatonin, both in ill and well states. We tested young people aged 15 to 25 years with one manic-depressive parent (n = 18), major affective disorder on both sides of the family (n = 7), and age-matched controls (n = 20). The subjects in the high-risk groups were more likely to show supersensitivity in melatonin response to light at night than controls. Follow-up studies are necessary to assess the predictive value of this response.

Rapid switching of mood in families with multiple cases of bipolar disorder

BACKGROUND

Heterogeneity within the diagnostic construct of bipolar disorder is most likely an obstacle to discovering its causes. Phenomena in the bipolar spectrum, including rapid cycling, cyclothymia, and affective instability of borderline personality, may be important markers of etiologic heterogeneity. Rapid switching of mood may be central to these phenomena.

METHODS

We performed a case-control study, using diagnostic data from a multisite bipolar disorder linkage study, to explore clinical and demographic factors potentially related to rapid switching in bipolar disorder. Participants were 18 years or older and members of a family in which 2 or more first-degree relatives had bipolar disorder. Of 718 individuals interviewed and diagnosed as having bipolar disorder, 603 gave sufficient information about rapid switching and thus constituted the study group (60% female; mean age, 41 years; and mean education level, 13.8 years).

RESULTS

Rapid switching of mood was reported by 44% of interviewees and was associated with early age at onset of bipolar disorder, higher risk of anxiety and substance abuse or dependence comorbidity, suicide attempts, antidepressant drug use, and having a relative with rapid switching.

CONCLUSIONS

Rapid switching is associated with a complex clinical course of bipolar disorder. These results extend previous associations among rapid switching, anxiety, substance abuse, and early onset of bipolar disorder to a family study population. Rapid switching of mood seems to be the core phenomenon behind several variants of non-DSM-IV rapid cycling, DSM-III-R mixed states, and borderline personality disorder and the link connecting comorbidity, suicide, and early onset of bipolar disorder. Further biological investigation of the rapid-switching phenomenon is justified on epidemiologic grounds.

Effects of cortisone administration on the metabolism and localization of 25-hydroxycholecalciferol in the rat

Glucocorticoid administration is known to decrease calcium absorption in vivo and the vitamin D-dependent active transport of calcium by rat duodenum in vitro. The basis for this antivitamin D-like effect of glucocorticoids is unclear. Previous studies in the rat failed to demonstrate an effect of glucocorticoid treatment on the hepatic conversion of the parent vitamin to 25-hydroxycholecalciferol (25-HCC). Moreover, pharmacologic doses of 25-HCC did not restore intestinal calcium transport to normal. The results of these experiments suggested that if indeed glucocorticoids interfere with the metabolism of vitamin D, the step involved must be subsequent to 25-hydroxylation. The present studies demonstrate that the administration of cortisone to vitamin D-deficient rats does not affect the rate of conversion of a physiologic dose of [(3)H]25-HCC to the biologically important metabolite, 1,25-dihydroxycholecalciferol (1,25-DHCC). Furthermore, pretreatment with glucocorticoids affects neither the tissue distribution nor the subcellular localization on or in intestinal mucosal cell nuclei of 1,25-DHCC. Of note is the fact that 1,25-DHCC is currently considered to be the "tissue-active" form of the vitamin in the intestine. Whereas tissues from cortisone-treated animals had increased concentrations of the biologically less active 24,25-DHCC, the physiologic significance of this observation remains unclear. The results of the present studies strongly support the concept that the antivitamin D-like effects of glucocorticoids in the intestine are due to hormonal influences on the biochemical reactions responsible for calcium transport. While the effects of these hormones are opposite in direction to those of vitamin D, they occur by a mechanism that is independent of a direct interaction with either the vitamin or its biologically active metabolites.

Modulation of cardiac Ca2+ channels in Xenopus oocytes by protein kinase C

L-Type calcium channel was expressed in Xenopus laevis oocytes injected with RNAs coding for different cardiac Ca2+ channel subunits, or with total heart RNA. The effects of activation of protein kinase C (PKC) by the phorbol ester PMA (4 beta-phorbol 12-myristate 13-acetate) were studied. Currents through channels composed of the main (alpha 1) subunit alone were initially increased and then decreased by PMA. A similar biphasic modulation was observed when the alpha 1 subunit was expressed in combination with alpha 2/delta, beta and/or gamma subunits, and when the channels were expressed following injection of total rat heart RNA. No effects on the voltage dependence of activation were observed. The effects of PMA were blocked by staurosporine, a protein kinase inhibitor. beta subunit moderate the enhancement caused by PMA. We conclude that both enhancement and inhibition of cardiac L-type Ca2+ currents by PKC are mediated via an effect on the alpha 1 subunit, while the beta subunit may play a mild modulatory role.

The Pharmacogenomics of Bipolar Disorder study (PGBD): identification of genes for lithium response in a prospective sample

BACKGROUND

Bipolar disorder is a serious and common psychiatric disorder characterized by manic and depressive mood switches and a relapsing and remitting course. The cornerstone of clinical management is stabilization and prophylaxis using mood-stabilizing medications to reduce both manic and depressive symptoms. Lithium remains the gold standard of treatment with the strongest data for both efficacy and suicide prevention. However, many patients do not respond to this medication, and clinically there is a great need for tools to aid the clinician in selecting the correct treatment. Large genome wide association studies (GWAS) investigating retrospectively the effect of lithium response are in the pipeline; however, few large prospective studies on genetic predictors to of lithium response have yet been conducted. The purpose of this project is to identify genes that are associated with lithium response in a large prospective cohort of bipolar patients and to better understand the mechanism of action of lithium and the variation in the genome that influences clinical response.

METHODS/DESIGN

This study is an 11-site prospective non-randomized open trial of lithium designed to ascertain a cohort of 700 subjects with bipolar I disorder who experience protocol-defined relapse prevention as a result of treatment with lithium monotherapy. All patients will be diagnosed using the Diagnostic Interview for Genetic Studies (DIGS) and will then enter a 2-year follow-up period on lithium monotherapy if and when they exhibit a score of 1 (normal, not ill), 2 (minimally ill) or 3 (mildly ill) on the Clinical Global Impressions of Severity Scale for Bipolar Disorder (CGI-S-BP Overall Bipolar Illness) for 4 of the 5 preceding weeks. Lithium will be titrated as clinically appropriate, not to exceed serum levels of 1.2 mEq/L. The sample will be evaluated longitudinally using a wide range of clinical scales, cognitive assessments and laboratory tests. On relapse, patients will be discontinued or crossed-over to treatment with valproic acid (VPA) or treatment as usual (TAU). Relapse is defined as a DSM-IV manic, major depressive or mixed episode or if the treating physician decides a change in medication is clinically necessary. The sample will be genotyped for GWAS. The outcome for lithium response will be analyzed as a time to event, where the event is defined as clinical relapse, using a Cox Proportional Hazards model. Positive single nucleotide polymorphisms (SNPs) from past genetic retrospective studies of lithium response, the Consortium on Lithium Genetics (ConLiGen), will be tested in this prospective study sample; a meta-analysis of these samples will then be performed. Finally, neurons will be derived from pluripotent stem cells from lithium responders and non-responders and tested in vivo for response to lithium by gene expression studies. SNPs in genes identified in these cellular studies will also be tested for association to response.

DISCUSSION

Lithium is an extraordinarily important therapeutic drug in the clinical management of patients suffering from bipolar disorder. However, a significant proportion of patients, 30-40 %, fail to respond, and there is currently no method to identify the good lithium responders before initiation of treatment. Converging evidence suggests that genetic factors play a strong role in the variation of response to lithium, but only a few genes have been tested and the samples have largely been retrospective or quite small. The current study will collect an entirely unique sample of 700 patients with bipolar disorder to be stabilized on lithium monotherapy and followed for up to 2 years. This study will produce useful information to improve the understanding of the mechanism of action of lithium and will add to the development of a method to predict individual response to lithium, thereby accelerating recovery and reducing suffering and cost.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01272531 Registered: January 6, 2011.

Evidence for a null allele at the esterase D (EC 3.1.1.1) locus

Electorphoretic and quantitative assays of esterase D in a Caucasian family demonstrate the inheritance of a null allele, which was observed in the heterozygous state in six individuals.

Effect of renal insufficiency on the active transport of calcium by the small intestine

The intestinal absorption of calcium is often depressed in patients with chronic renal insufficiency. Furthermore, the malabsorption of calcium and the osteodystrophy which occur in association with chronic renal disease are often "resistant" to vitamin D; the basis for this resistance remains uncertain however. Recent studies by others have emphasized the role of an abnormality in the metabolism of vitamin D in accounting for the alterations in the calcium absorption and the apparent vitamin D-resistance which accompany the uremic syndrome. The present studies with an experimentally uremic animal model demonstrate a defect in the active transport of calcium by duodenal gut sacs in vitro. This abnormality is not due to the semistarvation associated with renal insufficiency and cannot be corrected by the administration of physiologic amounts of vitamin D(3): it is reversed by massive doses of the vitamin. Neither the metabolism of vitamin D(3) nor the levels of calcium binding protein activity in the duodenal mucosa are affected by renal insufficiency under the conditions employed in the present studies. The results of the present studies strongly suggest that in addition to the recently proposed mechanism involving an interference with the metabolism of vitamin D renal insufficiency also affects the cellular mechanisms for calcium transport in a manner which, while opposite in direction to that of vitamin D, is independent of a direct interaction with the vitamin or its metabolites.

Relation of visual perception and visual-motor integration for clumsy children

The purpose of this study was to examine the relationship between visual perception and visual-motor integration in 30 normal children compared to 30 clumsy children. Difficulty in visual perception, as assessed by the Test of Visual-Perceptual Skills, accounts for about half the variance in the clumsy children's performance in visual-motor integration, as assessed by the Developmental Test of Visual Motor Integration. In contrast, the correlation between scores on these tests for normal control children was low and not significant. These results suggest that visual perception and visual-motor integration may be separate functions in normally developing children. When considering clumsy children, however, these functions cannot be considered as two independent skills.

Effects of cycloheximide on the response of intestinal mucosa to cholera enterotoxin

Prior studies have indicated that effects of cholera enterotoxin (CT) on the small intestine are delayed in onset and involve an interaction with adenyl cyclase in the mucosa. It has also been shown that the administration of cycloheximide to rabbits in doses which inhibit crypt cell mitoses (20 mg/kg), diminishes CT-induced fluid production in jejunal loops. These latter studies have been interpreted as indications that CT-related intestinal secretion is a crypt cell function and that it is mediated by a CT-induced protein. The present study was undertaken to delineate more precisely the nature of the interaction in the intestine between cycloheximide and cholera toxin. Pretreatment of rabbits with cycloheximide reduced by 60% the secretory response to CT in isolated ileal loops with intact blood supply. Sodium and chloride flux measurements on mucosa isolated from these and control loops indicated that this antisecretory effect of cycloheximide persists in vitro. Measurements of radioactive leucine incorporation into mucosal protein indicated that the dose of cycloheximide employed inhibited protein synthesis by 90%. This inhibitory effect was shown to be independent of any effect of cycloheximide on amino acid uptake across the brush border. Measurements of adenyl cyclase activity and cyclic AMP levels in ileal mucosa of cycloheximide pretreated and control animals indicated that cycloheximide did not diminish the CT-induced increases in these parameters. These observations demonstrate that cycloheximide reduces CT-induced intestinal fluid production without interfering with the CT-induced augmentation of adenyl cyclase activity or the consequent rise in cyclic. AMP concentration. Since the antisecretory effect of cycloheximide persists in vitro, it probably involves a direct interaction of the antibiotic with mucosal cell ion transport mechanisms rather than an indirect effect mediated by other humoral or neurogenic factors. The present observations also suggest that the secretory response of the intestine to CT involves neither the synthesis of new adenyl cyclase nor that of a protein modifying its activity.

Genome scan of a second wave of NIMH genetics initiative bipolar pedigrees: chromosomes 2, 11, 13, 14, and X

As part of the on-going NIMH Genetics Initiative on Bipolar Disorder, we have ascertained 153 multiplex bipolar pedigrees and genotyped them in two waves. We report here the genome scan results for chromosomes 2, 11, 13, 14, and X in the second wave of 56 families. A total of 354 individuals were genotyped and included in the current analyses, including 5 with schizoaffective/bipolar (SA/BP), 139 with bipolar I disorder (BPI), 41 with bipolar II disorder (BPII), and 43 with recurrent unipolar depression (RUP). Linkage analyses were carried out with multi-point parametric and non-parametric affected relative pair methods using three different definitions of the affected phenotype: (model 1) SA/BP and BPI; (model 2) SA/BP, BPI, and BPII; and (model 3) SA/BP, BPI, BPII, and RUP. The best findings were on 11p15.5 (NPL = 2.96, P = 0.002) and Xp11.3 (NPL = 2.19, P = 0.01). These findings did not reach conventional criteria for significance, but they were located near regions that have been identified in previous genetic studies of bipolar disorder. The relatively modest but consistent findings across studies may suggest that these loci harbor susceptibility genes of modest effect in a subset of families. Large samples such as that being collected by the NIMH Initiative will be necessary to examine the heterogeneity and identify these susceptibility genes.

Personal and social resources in children of patients with bipolar affective disorder and children of normal control subjects

The authors examined the personal resources (social problem-solving ability, internal locus of control, self-esteem, and self-perceived competence) and social resources (social network structure and support) in 23 children of patients with bipolar affective disorder (probands) and 33 children of normal control parents. Positive resource profiles were related to psychiatric well-being in the offspring. Nondisordered probands, in particular, demonstrated a strikingly positive profile of personal resources as well as a wide range of peer, sibling, and other kin supporters. Disordered probands had a strikingly negative set of personal resources and a relatively greater reliance on nonkin adult supporters. The absence of a supportive best friend was associated with affective disorder across offspring groups.

A family study of rapid-cycling bipolar illness

Twenty-nine out of 195 bipolar/episodic schizoaffective patients were judged to be rapid-cyclers (15%). Twenty-five of the 29 were female (86%). The age-corrected morbid risk for major affective disorder was 23.5% in 179 relatives of rapid-cyclers and 31.0% in 189 relatives of matched non-rapid cyclers (chi 2 = 2.6, NS). The prevalence of rapid-cycling itself was also not different in the two groups of relatives. Rapid-cycling thus appears to arise from factors which are separable from the genetic vulnerability to bipolar illness and which do not lead to aggregation within families.

Genome-wide linkage scan of 98 bipolar pedigrees and analysis of clinical covariates

Despite compelling evidence that genetic factors contribute to bipolar disorder (BP), attempts to identify susceptibility genes have met with limited success. This may be due to the genetic heterogeneity of the disorder. We sought to identify susceptibility loci for BP in a genome-wide linkage scan with and without clinical covariates that might reflect the underlying heterogeneity of the disorder. We genotyped 428 subjects in 98 BP families at the Center for Inherited Disease Research with 402 microsatellite markers. We first carried out a non-parametric linkage analysis with MERLIN, and then reanalyzed the data with LODPAL to incorporate clinical covariates for age at onset (AAO), psychosis and comorbid anxiety. We sought to further examine the top findings in the covariate analysis in an independent sample of 64 previously collected BP families. In the non-parametric linkage analysis, three loci were nominally significant under a narrow diagnostic model and seven other loci were nominally significant under a broader model. The top findings were on chromosomes 2q24 and 3q28. The covariate analyses yielded additional evidence for linkage on 3q28 with AAO in the primary and independent samples. Although none of the linked loci were genome-wide significant, their congruence with prior results and, for the covariate analyses, their identification in two separate samples increases the likelihood that they are true positives and deserve further investigation. These findings further demonstrate the value of considering clinical features that may reflect the underlying heterogeneity of disease in order to facilitate gene mapping.

Apparent replication of suggestive linkage on chromosome 16 in the NIMH genetics initiative bipolar pedigrees

Analyses of a replication sample of families collected as part of the National Institute of Mental Health (NIMH) Genetics Initiative for bipolar disorder provide further evidence for linkage to a region of chromosome 16. Families who had a bipolar I (BPI) proband and at least one BPI or schizoaffective, bipolar type (SABP) first-degree relative were ascertained for the purpose of identifying genes involved in bipolar affective disorder. A series of hierarchical models of affected status was used in linkage analyses. Initial genetic analyses of chromosomes 3, 5, 15, 16, 17, and 22, completed at Indiana University in 540 subjects from 97 families, suggested evidence of linkage to chromosomes 5, 16, and 22 [Edenberg et al., 1997: Am J Med Genet 74:238-246]. Genotyping was subsequently performed on these chromosomes in a replication sample of 353 individuals from 56 families. Nonparametric linkage analyses were performed using both affected relative and sibling pair methods. Analyses in the new sample on chromosome 16, using the broadest model of affected status, corroborate previously reported suggestive linkage to the marker D16S2619. Combining the initial and replication samples further increased the evidence of linkage to this region, with a peak lod score of 2.8.