Expression of spatially regulated genes in the sea urchin embryo.

Spatially controlled genes expressed in the early sea urchin embryo have been characterized, and the patterns of expression in terms of the mechanisms by which this embryo accomplishes its initial set of founder cell specifications are the subject of current discussion. Sea urchin transcription factors that have been cloned are classified with respect to their target sites and the genes they regulate. Among the best known of the sea urchin cis-regulatory systems is that controlling expression of the Cyllla gene, which encodes an aboral ectoderm-specific cytoskeletal actin. The Cyllla regulatory domain includes approximately 20 sites of DNA-protein interaction, serviced by about ten different factors. Certain of these factors are known to negatively control spatial expression, while others positively regulate temporal activation and the level of Cyllla gene expression. Differential, lineage-specific gene expression is instituted in the sea urchin embryo by mid-late cleavage, prior to any cell migration or overt differentiation, and shortly following lineage segregation.

Combinatorial regulation of the Saccharomyces cerevisiae CAR1 (arginase) promoter in response to multiple environmental signals.

CAR1 (arginase) gene expression responds to multiple environmental signals; expression is induced in response to the intracellular accumulation of arginine and repressed when readily transported and catabolized nitrogen sources are available in the environment. Up to 14 cis-acting sites and 9 trans-acting factors have been implicated in regulated CAR1 transcription. In all but one case, the sites are redundant. To test whether these sites actually participate in CAR1 expression, each class of sites was inactivated by substitution mutations that retained the native spacing of the CAR1 cis-acting elements. Three types of sites function independently of the nitrogen source: two clusters of Abflp- and Rap1p-binding sites, and a GC-rich sequence. Two different sets of nitrogen source-dependent sites are also required: the first consists of two GATAA-containing UASNTR sites that mediate nitrogen catabolite repression-sensitive transcription, and the second is arginine dependent and consists of three UAS1 elements that activate transcription only when arginine is present. A single URS1 site mediates repression of CAR1 arginine-independent upstream activator site (UAS) activity in the absence of arginine and the presence of a poor nitrogen source (a condition under which the inducer-independent Gln3p can function in association with the UASNTR sites). When arginine is present, the combined activity of the UAS elements overcomes the negative effects mediated by URS1. Mutation of the classes of sites either singly or in combination markedly alters CAR1 promoter operation and control, supporting the idea that they function synergistically to regulate expression of the gene.

Gat1p, a GATA family protein whose production is sensitive to nitrogen catabolite repression, participates in transcriptional activation of nitrogen-catabolic genes in Saccharomyces cerevisiae.

Saccharomyces cerevisiae cells selectively use nitrogen sources in their environment. Nitrogen catabolite repression (NCR) is the basis of this selectivity. Until recently NCR was thought to be accomplished exclusively through the negative regulation of Gln3p function by Ure2p. The demonstration that NCR-sensitive expression of multiple nitrogen-catabolic genes occurs in a gln3 delta ure2 delta dal80::hisG triple mutant indicated that the prevailing view of the nitrogen regulatory circuit was in need of revision; additional components clearly existed. Here we demonstrate that another positive regulator, designated Gat1p, participates in the transcription of NCR-sensitive genes and is able to weakly activate transcription when tethered upstream of a reporter gene devoid of upstream activation sequence elements. Expression of GAT1 is shown to be NCR sensitive, partially Gln3p dependent, and Dal80p regulated. In agreement with this pattern of regulation, we also demonstrate the existence of Gln3p and Dal80p binding sites upstream of GAT1.

A GBF-binding site and a novel AT element define the minimal sequences sufficient to direct prespore-specific expression in Dictyostelium discoideum.

In order to better understand the molecular mechanisms of cellular differentiation in Dictyostelium discoideum, we have identified the minimum regulatory sequences of the prespore-specific gene SP60/cotC that are sufficient to confer cell-type-specific expression on a heterologous promoter. This region includes at least two essential cis-acting elements: a novel AT-rich element (or elements) and CAE3. The essential function of the AT element is confirmed through point mutations that decrease expression below the level of detection. CAE3 is one of three CA-rich elements (CAEs) required for the induction of SP60/cotC during development or in response to extracellular cyclic AMP. The CAEs have differential affinities for a specific developmentally induced nuclear activity (CAE1 > CAE2 >> CAE3). Here, we identify this activity as G-box-binding factor (GBF) and show that in vitro-transcribed and -translated GBF binds all three SP60/cotC CAEs in a sequence-specific manner. Previous studies have suggested that GBF mediates the induction of some prestalk genes, and these results demonstrate that it also has a specific role in prespore gene activation.

Spatial and temporal expression of the Dictyostelium discoideum G alpha protein subunit G alpha 2: expression of a dominant negative protein inhibits proper prestalk to stalk differentiation.

Previous results have shown that the G alpha protein subunit G alpha 2 is required for aggregation in Dictyostelium discoideum and is essential for coupling cell-surface cAMP receptors to downstream effectors in vivo during this stage of development. G alpha 2 expresses at least four distinct transcripts that are differentially regulated during development; two of the transcripts are expressed exclusively in the multicellular stages and their expression is restricted to prestalk cells. We partially dissected the G alpha 2 promoter and identified a component that is expressed exclusively during the multicellular stages using luciferase gene fusions. When this promoter region is coupled to lacZ, beta-gal expression is restricted to the multicellular stages and localized in prestalk cells with a pattern similar to that of the ecmA prestalk-specific promoter. We show that expression in wild-type cells of the G alpha 2 mutant protein [G alpha 2(G206T)] during the early stages of development blocks aggregation and cAMP-mediated activation of adenylyl cyclase and guanylyl cyclase, suggesting it functions as a dominant negatively active G alpha subunit. When this mutant G alpha protein is expressed from the ecmA prestalk-specific promoter, abnormal stalk differentiation during culmination is observed. Expression of the mutant G alpha 2 from the SP60 prespore promoter or wild-type G alpha 2 from either the ecmA or the SP60 promoter results in no detectable phenotype. The results suggest that G alpha 2 plays an essential role during the culmination stage in prestalk cells and may mediate cAMP receptor activation of these processes during multicellular development.

Structural abnormalities in the frontal system in schizophrenia. A magnetic resonance imaging study.

Thirty-eight schizophrenics and 49 normal controls underwent magnetic resonance imaging. Midline sagittal cuts indicated that the schizophrenics had significantly smaller frontal lobes, as well as smaller cerebrums and craniums. The findings are consistent with some type of early developmental abnormality that might retard brain growth and therefore skull growth. These findings are confirmed on a smaller sample of patients on whom we have coronal cuts. Decreased cerebral and cranial size are associated with prominent negative symptoms, although decreased frontal size is not. Decreased cranial and cerebral size was also associated with impairment on some cognitive tests. These findings are consistent with the hypothesis that some schizophrenics may have a type of early developmental abnormality associated with prominent negative symptoms and cognitive impairment. Further, the results suggest that schizophrenics may have a type of structural frontal system impairment. Thus, they provide anatomic evidence for the "hypofrontality hypothesis."

Left hemispheric density deficits in chronic schizophrenia.

Regional determinations of mean cerebral tissue density were made for 50 chronic schizophrenics and compared with results in 24 normal controls. When values for corresponding left and right hemispheric regions were compared, 11 of 12 comparisons showed the left regional value to be significantly greater than the right for controls while only 6 of 12 comparisons among schizophrenics showed left values significantly greater than right. These data suggest an overall decreased relative density of the left cerebral hemisphere in schizophrenia. Further implications of the data are discussed.

Cognitive impairment and cerebral structure by MRI in bipolar disorder.

The distinction between bipolar disorder and schizophrenia customarily follows examination of the clinical symptomatology and course of illness. The presence of cognitive impairment has been held to be uncommon in bipolar disorder and more likely in schizophrenia. This study explored neuropsychological function in 30 ambulatory outpatients with a DSM-III-R diagnosis of bipolar affective disorder (all of whom had been psychotic during manic episodes), comparing their performance with that of controls. These bipolar patients proved to have significant levels of diffusely represented cognitive impairment when compared with controls. Further, the degree of impairment was significantly correlated with reduction in midsagittal areas of brain structures measured on magnetic resonance imaging scans. The implications of these findings in relation to bipolar disorder are discussed.

Leukoaraiosis in asymptomatic adult offspring of individuals with Alzheimer's disease.

The presence of white matter changes on magnetic resonance imaging (MRI), which has been referred to by Hachinski (1987) as leukoaraiosis, is frequently noted in elderly individuals in conditions ranging from health to frank dementia. This study involved the use of MRI to document cerebral structure if 41 healthy 50-60-year-old individuals, 28 of whom were offspring of Alzheimer's disease victims. On visual inspection of spin-echo images, 13 of the 28 offspring showed white matter lesions whereas all of the controls were free of leukoaraiosis. This statistically significant difference suggests that the presence of leukoaraiosis might be of importance in understanding changes in the white matter among populations at increased risk for Alzheimer's disease.

Perinatal brain injury and cerebellar vermal lobules I-X in schizophrenia.

Several studies, including our own, have reported atrophy of the cerebellar vermis in some schizophrenic patients. A recent report by Courchesne et al (1988) of hypoplasia of a developmentally specific region of the cerebellar vermis in autism prompted us to hypothesize that the cerebellar "atrophy" in some schizophrenic patients may also have developmental origins. We measured the area of the vermal lobules in 30 male schizophrenics. Contrary to expectation, the patients as a group had consistently larger cerebellar structures than the controls. Patients with perinatal injury had smaller structures than the nonperinatally injured group, but these measures were still larger than in the control subjects. Patients without perinatal injury differed from controls, having larger lobules VI-VII (p less than 0.03). These preliminary findings tentatively suggest a role for developmental factors for cerebellar structures in schizophrenia. Further research is needed to clarify the cerebellar vermal changes observed in some schizophrenic patients.

A controlled magnetic resonance imaging study of corpus callosum thickness in schizophrenia.

Two previous postmortem studies reported an increased thickness of the corpus callosum in schizophrenic patients compared to psychiatric controls. We report an in vivo study of the corpus callosum in schizophrenic patients (n = 38) and healthy controls (n = 41) using magnetic resonance (MR) brain imaging. A significant increase in mean callosal thickness was found in the middle and anterior, but not the posterior, parts of the callosal body. However, when the patients and controls were compared by gender and handedness, schizophrenic men were found not to differ from control men in callosal thickness, regardless of handedness, whereas schizophrenic women were found to have a highly significant increase in callosal middle and anterior thickness compared to control women. The data suggest that increased callosal thickness in schizophrenia is gender related, a factor that is not considered by postmortem studies. The implications of increased callosal dimensions in female schizophrenics are discussed.

Plasma GABA levels in chronic alcoholics.

Ethanol intoxication has been noted to cause marked changes in brain and CSF levels of gamma-aminobutyric acid (GABA). Using plasma GABA levels to assess brain GABA activity, the authors found that 85 chronic alcoholics had significantly lower levels than control subjects.

Clinical effectiveness of oral and parenteral rapid neuroleptization.

A random assignment, double-blind, placebo-controlled evaluation was used to compare the effectiveness of rapid parenteral injections of fluphenazine hydrochloride with that of oral doses of the same drug in 16 patients with acute psychotic illnesses. Doses of fluphenazine hydrochloride were much higher in the parenteral neuroleptization group than in the oral administration group during the acute phase, although oral doses were equivalent during the continuation phase. The rate of improvement was not different for the two groups, but the rate of extrapyramidal side effects was higher in the parenteral neuroleptization group. The results suggest that rapid parenteral neuroleptization for the acute treatment of psychosis offers more risks than benefits.

Opiate antagonism fails to reverse post-ECT cognitive deficits.

The opiate antagonist naloxone has been reported to improve memory in animals and to produce partial improvement in Alzheimer's dementia. The usefulness of naloxone for reversing ECT-induced cognitive impairment was tested by comparing the effects of naloxone and placebo on several tests of cognitive performance in 10 patients who underwent bilateral ECT. No significant differences were found between naloxone and placebo. The results suggest that at the doses used, naloxone is not effective in reversing ECT-induced memory deficits.

Midsagittal cerebral anatomy by magnetic resonance imaging. The importance of slice position and thickness.

Several recent studies of psychiatric patients have relied upon magnetic resonance imaging (MRI) to demonstrate features of cerebral anatomy in the midsagittal plane. Methodologies have varied somewhat in relation to thickness and position of planes of view. Due to concerns over the effects of slice thickness and position on measurements, the authors used a multislice thin plane method to assess these effects in 143 individuals (34 controls, 58 schizophrenics, and 51 with bipolar or schizoaffective disorder). Substantial variance in area measurements attributable to slice position emerged, especially in ventricular, cerebral and cerebellar area. Of greater importance would be the demonstrated interaction of position with diagnosis and sex in measures of several regions. The implications of these findings for MRI studies are discussed.

Interhemispheric differences in regional density of the normal brain.

In a study of regional variations in cerebral X-ray attenuation as measured by computed tomography, a relationship between bone-related beam hardening and lateralized hemispheric density differences was sought. The CT scans of 22 normal right-handed individuals were evaluated by calculating regional mean attenuation values and regional left-right differences in attenuation, comparing these to regional measurements of skull thickness. A statistically insignificant number of significant correlations was found. This is interpreted to mean that observed left-right hemispheric density differences are not due to beam-hardening through bone. It was also found that left-right differences in density persisted over the entirety of the evaluated slices, suggesting that this finding is due to inherent hemispheric structural differences.

Gender differences in schizophrenia on MRI brain scans.

There are many reports of clinical and biological gender differences in schizophrenia. Gender differences in structural brain abnormalities in schizophrenia have been reported on both computed tomographic (CT) and magnetic resonance imaging (MRI) scans. We present here a new MRI study of cerebral structures in schizophrenia. On the basis of previous findings, we hypothesized that schizophrenic males are more likely than females to show smaller brains and larger ventricles compared to their control counterparts. Our results indicated that the opposite was true: schizophrenic females, but not schizophrenic males, had smaller craniums and brains and larger lateral and third ventricles on MRI scans. The possible significance and implications of these data are discussed.

Event-related brain potentials in depressed patients treated with electroconvulsive therapy.

1. As impairment of attention has long been recognized as a clinical feature of depression, we undertook to evaluate in depressed subjects and controls a feature of the event-related brain potentials (ERP) the N100 wave which has been linked to attentional processes. 2. This study involved collection of EEG data in an "auditory oddball" ERP paradigm in 9 depressed subjects prior to and following a course of 6 electroconvulsive therapy (ECT) treatments, as well as 11 controls. Concurrent Hamilton depression rating scales provided a measure of symptomatic severity. 3. Pretreatment N100 amplitude was significantly lower in the depressed group while N100 latency was greater than among controls, with treatment differences from control values disappeared. Further a robust correlation (r = 0.85 p less than or equal to .0038) emerged between N100 amplitude (increased amplitude being lower) and severity of depression. 4. Those results provide evidence for a physiological attentional disturbance in depression and suggest that certain features of this disturbance relate directly to symptom severity.

Brain density patterns in schizophrenia and mania.

Regional brain density as measured by X-ray computed tomography was assessed in young schizophrenic (mean age 29.8 years) and manic (mean age 32.7 years) males in order to determine whether this parameter would distinguish between these groups of patients. Our findings reveal similar patterns of interhemispheric density differences in the two groups but significantly greater overall density among manics for the uppermost brain sections studied (16-24 mm above the slice intercepting the body of the lateral ventricles). Clinical implications of these findings are discussed.

Antipsychotic withdrawal phenomena in the medical-surgical setting.

The literature describing nondyskinetic antipsychotic withdrawal symptoms is reviewed. The withdrawal of antipsychotic agents can result in nausea, emesis, anorexia, diarrhea, rhinorrhea, diaphoresis, myalgias, paresthesias, anxiety, agitation, restlessness, and insomnia. Psychotic relapse is often presaged by increased anxiety, agitation, restlessness, and insomnia. However, the temporal relationship of these prodromal symptoms to reduction in the dosage or discontinuation of neuroleptics distinguishes them from the effects of abrupt withdrawal.