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Schizophrenia: solving the puzzle.

BACKGROUND: Schizophrenia is a common mental illness with an incidence of 15 new cases per 100,000 population per year. AIM: To review evidence for current neurodevelopmental models of the aetiology of schizophrenia. METHODS: We performed a literature search using Medline and PsychINFO. We evaluated the relevance of each article and tracked other relevant articles through references. RESULTS: There is considerable evidence to support neurodevelopmental models of the aetiology of schizophrenia. One or more aetiological events occur between conception and birth that disturb central nervous system (CNS) development, leading to persisting alterations in brain structure and function. These early events, acting in concert with genetic loading and later influences or insults, predispose to the development of schizophrenia in early adulthood. CONCLUSIONS: There have been considerable advances in schizophrenia research over the past 20 years. Future study of Indices of neural development will help advance our understanding of this common, disabling mental illness.

Central Nervous System↗

The ABC Schizophrenia Study: a preliminary overview of the results.

The ABC Schizophrenia Study, a large-scale epidemiological and neurobiological research project commenced in 1987, initially pursued two aims: (1) to elucidate the possible causes of the sex difference in age at first admission for schizophrenia and (2) to analyse the early course of the disorder from onset until first contact and its implications for further course and outcome. First, transnational case-register data (for Denmark and Germany) were compared, second, a population-based sample of first-episode cases of schizophrenia (n = 232) were selected and third, the results obtained were compared with data from the WHO Determinants of Outcome Study by using a systematic methodology. A consistent result was a 3-4 years higher age of onset for women by any definition of onset, which was not explainable by social variables, such as differences in the male-female societal roles. A sensitivity-reducing effect of oestrogen on central D2 receptors was identified as the underlying neurobiological mechanism in animal experiments. Applicability to humans with schizophrenia was established in a controlled clinical study. A comparison of familial and sporadic cases showed that in cases with a high genetic load, the sex difference in age of onset disappeared due to a clearly reduced age of onset in women, whereas in sporadic cases it increased. To analyse early course retrospectively, a semistructured interview, IRAOS, was developed. The early stages of the disorder were reconstructed in comparison with age- and sex-matched controls from the same population of origin. The initial signs consisted mainly of negative and affective symptoms, which accumulated exponentially until the first episode, as did the later emerging positive symptoms. Social disability appeared 2-4 years before first admission on average. In early-onset cases, social course and outcome, studied prospectively over 5 years, was determined by the level of social development at onset through social stagnation. In late-onset cases, decline from initially high social statuses occurred. Socially negative illness behaviour contributed to the poor social outcome of young men. Symptomatology and other proxy variables of the disorder showed stable courses and no sex differences. Further aspects tested were the sequence of onset and the influence of substance abuse on the course of schizophrenia, primary and secondary negative symptoms, structural models and symptom clusters from onset until 5 years after first admission.

Adolescent↗

Paragenetic suppressors of suppressor genes--a new class of oncodeterminants.

Impairment or loss of suppressor genes is a common event permitting the oncogene/suppressor gene machinery to develop neoplasia. Following prenatal treatment with X-rays and UV-B, we detected a new class of oncodeterminants that could not be specified as genes. This points to paragenetic elements that suppress suppressorgenes and thus provoke melanoma at earlier ages of onset as expected, with increased severity and increased number of incidences in successive generations, in the absence of further treatment. These elements were isolated from a xiphophorine DNA library by endogenously labeled long terminal repeats (LTR) of a xiphophorine retrovirus, and were characterized as retrotransposons by Southern and Northern blotting and reverse transcription/polymerase chain reaction and transient transfection studies, in situ hybridization, and sequencing. They appear in multiple copies in the telomeric chromosome regions, where they can extend. Three open reading frames (ORF) are flanked by LTR that contain genetically active regulatory elements, and are inducible by UV-B. ORF 3 shows nests of CG dinucleotides and CGG trinucleotides, which are reminiscent of CGG nests predisposing subjects to anticipation of certain human diseases involving tumor generation. Genetic anticipation as defined by Nettleship (1909) or Warren (1996) including an increase of neoplasia might represent an acquired genetic load in preceding generations, which might provide a lead to a molecular understanding of the worldwide increase of incidences of human tumor.

Animals↗

High frequency of unusual gastric/duodenal ulcers in patients with Behçet's disease in Taiwan: a possible correlation of MHC molecules with the development of gastric/duodenal ulcers.

The gastrointestinal (GI) involvement of Behçet's disease (BD) mainly affects the ileocecal region and colon. The gastroduodenal mucosa appears to be the least frequently involved segment of the gastrointestinal tract. The objective of this study was to assess the severity of gastric/duodenal involvement in BD patients in Taiwan. Behçet's disease was diagnosed according to the diagnostic criteria issued by the International Study Group for Behçet's Disease. We obtained and recorded clinical and laboratory data. A routine endoscopic examination with a urease test for Helicobacter pylori infection was arranged. Furthermore, HLA tissue typing was also performed by polymerase chain reaction with sequence-specific primers to evaluate the possible genetic loads associated with ulcer development. A total 28 BD patients, diagnosed at DaLin TzuChi hospital from 1999 to 2002, were enrolled in this study. The prevalence rate of gastric/duodenal ulceration was 43% (six patients had combined gastric and duodenal ulcers, three patients had simple gastric ulcers, and three patients had simple duodenal ulcers). No risk factors of nonsteroidal anti-inflammatory drug (NSAID) or H. pylori infection were found to be associated with gastrointestinal ulcers in our BD patients. All patients with peptic ulcers responded well to systemic steroids and immunosuppressant treatment in this preliminary observation. Furthermore, 7 of 12 gastric/duodenal ulcer patients (58%) carried an A2/B46/Cw1 or A11/B46/Cw1 genotype. Our data indicated that gastric/duodenal ulcers were a common manifestation in Chinese patients with BD in Taiwan in close association with the distinct genotypes of A2/B46/Cw1 or A11/B46/Cw1. A good response to systemic steroids, rather than conventional H2 blockers, might be due to downregulation of the vasculitis.

Adult↗

Hybridization and the colonization of novel habitats by annual sunflowers.

Although invasive plant species often have a hybrid ancestry, unambiguous evidence that hybridization has stimulated the evolution of invasive behaviors has been difficult to come by. Here, we briefly review how hybridization might contribute to the colonization of novel habitats, range expansions, and invasiveness and then describe work on hybrid sunflowers that forges a direct link between hybridization and ecological divergence. We first discuss the invasion of Texas by the common sunflower and show that the introgression of chromosomal segments from a locally adapted species may have facilitated range expansion. We then present evidence that the colonization of sand dune, desert floor, and salt marsh habitats by three hybrid sunflower species was made possible by selection on extreme or "transgressive" phenotypes generated by hybridization. This body of work corroborates earlier claims regarding the role of hybridization in adaptive evolution and provides an experimental and conceptual framework for ongoing studies in this area.

Biological Evolution↗

Bacterial artificial chromosome (BAC) library resource for positional cloning of pest and disease resistance genes in cassava (Manihot esculenta Crantz).

Pest and disease problems are important constraints of cassava production and host plant resistance is the most efficient method of combating them. Breeding for host plant resistance is considerably slowed down by the crop's biological constraints of a long growth cycle, high levels of heterozygosity and a large genetic load. More efficient methods such as gene cloning and transgenesis are required to deploy resistance genes. To facilitate the cloning of resistance genes, bacterial artificial chromosome (BAC) library resources have been developed for cassava. Two libraries were constructed from the cassava clones, TMS 30001, resistant to the cassava mosaic disease (CMD) and the cassava bacterial blight (CBB), and MECU72, resistant to cassava white fly. The TMS30001 library has 55, 296 clones with an insert size range of 40-150 kb with an average of 80 kb, while the MECU72 library consists of 92 160 clones and an insert size range of 25-250 kb average of 93 kb. Based on a genome size of 772 Mb, the TMS30001 and MECU72 libraries have a 5 and 11.3 haploid genome equivalents and a 95 and 99 chance of finding any sequence, respectively. To demonstrate the potential of the libraries, the TMS30001 library was screened by southern hybridization using a cassava analog (CBB1) of the Xa21 gene from rice that maps to a region containing a QTL for resistance to CBB as probe. Five BAC clones that hybridized to CBB1 were isolated and a Hind III fingerprint revealed 2-3 copies of the gene in individual BAC clones. A larger scale analysis of resistance gene analogs (RGAs) in cassava has also been conducted in order to understand the number and organization of RGAs. To scan for gene and repeat DNA content in the libraries, end-sequencing was performed on 2,301 clones from the MECU72 library. A total of 1705 unique sequences were obtained with an average size of 715 bp. Database homology searches using BLAST revealed that 458 sequences had significant homology with known proteins and 321 with transposable elements. The use of the library in positional cloning of pest and disease resistance genes is discussed.

Animals↗

Psychotic disorder and traumatic brain injury.

Traumatic brain injury (TBI) can result in serious and disabling neuropsychiatric disorders, such as cognitive deficits and personality change, as well as severe and chronic psychosis. This review focuses on the relationship between TBI and schizophrenia-like psychosis (SLP) including its epidemiology, diagnostic criteria, clinical presentation, psychopathology, risk factors, and pathophysiology. The relationships between post-traumatic epilepsy and SLP, and brain trauma and schizophrenia, are also discussed. The risk of SLP does increase after TBI. The clinical presentation has considerable overlap with primary schizophrenic disorder, with a prominence of persecutory and other delusions and auditory hallucinations, as well as a lack of negative symptoms. The onset is often gradual, with a subacute or chronic course. More severe and diffuse brain injury, especially of the temporal and frontal lobes, is the most prominent risk factor. Genetic load may also play a role, but presence of epilepsy could be a protective factor. Further large and systematic longitudinal studies are needed.

Brain Injuries↗

Gout in Maoris.

Historical evidence suggests that the Maori people of New Zealand were virtually untroubled by gout or obesity at a time when these disorders, along with other elements of the gouty diathesis, were rife in the best fed and hardest drinking sections of the Northern European population. By the mid 20th century, however, the apparent decline of the gout in Europe and North America and the breakup of the gouty diathesis in those lands had been more than compensated by their large-scale reappearance in the Maori and in other indigenous inhabitants of the Pacific Basin who, at first sight, appeared to have become one large gouty family. Half the Polynesian population of New Zealand, Rarotonga, Puka Puka, and the Tokelau Islands proved to be hyperuricemic by accepted European and North American standards, the associated gout rate reaching 10.2% in Maori males aged 20 and over. The trends towards hyperuricemia and gout, on the one hand, and towards obesity, diabetes mellitus, hypertension, and associated degenerative vascular disorders, on the other hand, which manifest themselves separately in some Polynesian Pacific Islanders, run together in the Maori and Samoan people, presenting a combined problem of considerable importance to the public health. The appearance of these traits under conditions of plenty in the descendants of hardy and wide-ranging Polynesian voyagers, suggests the emergence of a formerly favorable ancestral polygenic variation through selection for survival under harder conditions. This may now have lost its primitive survival value with a paradoxic shift towards increased prevalence of obesity and the gouty diathesis in more affluent environmental conditions. This may now constitute a genetic load, with recent environmentally determined increase in morbidity and mortality rates from degenerative vascular disorders. There is no satisfactory evidence that overproduction of uric acid differs in mechanism from its European counterparts, although more work remains to be done to determine whether there is any difficulty in renal handling of an increased uric acid load. A high Maori morbidity rate from gout and morbidity and mortality rates from associated components of the gouty diathesis in the face of readily available skilled medical advice and care, indicate the need for greater future attention to help education and health care delivery, at least while conditions of plenty continue. Continuation of previous epidemiologic surveillance may then be required in order to provide a continuing index of the effectiveness of these measures, as well as an opportunity for further research into the interrelationships of these associated disorders.

Adult↗

EEG abnormalities in bipolar affective disorder.

Forty-six patients with bipolar illness were evaluated with scalp-recorded electroencephalograms. Familial pattern of psychopathology was evaluated between groups with clinically normal and abnormal EEG tracings. Those with abnormal EEGs were noted to have a significantly negative family history of affective disorder when compared to the EEG normal group. These results may support the concept of some patients with mania having an acquired illness which occurs independent from its genetic loading.

Bipolar Disorder↗

Can schizophrenia with premorbid asociality be genetically distinguished from the other forms of schizophrenia?

Sufficient data exist to establish a genetic basis for some forms of schizophrenia. However, genetic factors may not account for all the variance, and subtle forms of central nervous system (CNS) damage may have etiological significance for some schizophrenic subtypes. One such subtype may be chronic schizophrenia with premorbid asociality (SPA). To test this hypothesis, the risk of schizophrenia among relatives of probands who did or did not meet the criteria for SPA was examined. The incidence of schizophrenia in the relatives of SPA probands was lower than that in the relatives of non-SPA probands. This difference approached but did not reach statistical significance. Because most studies have found a higher familial genetic loading in chronic forms of schizophrenia, the apparently lower incidence of disorder in relatives of chronic schizophrenics with premorbid asociality seems to be a heuristic lead worth pursuing.

Antisocial Personality Disorder↗

P3 in alcoholics with disordered regulation of aggression.

Alcoholics have been found to show deficits in the P3 component of event-related potentials obtained using information-processing paradigms. However, alcoholic patients form a heterogeneous population. In a study of P3 voltages in subgroups of alcoholics with disorders in mood and aggression control, we observed significant decrements in these voltages in patients with lifelong histories of aggressive behavior. Patients with histories of incarceration for crimes involving physical violence had the lowest P3 amplitudes. The same patients also had a rate of paternal alcoholism significantly higher than that observed in the rest of the population. They could thus be classified as type 2 alcoholics, as a tendency to antisocial behavior and a high genetic loading for alcoholism have been described in this alcoholic subtype. These data could indicate that decrements in P3 amplitude characterize a subgroup of alcoholics with a disordered regulation of aggression. Alternatively, P3 deficits could be associated with some psychopathological conditions in individuals who abuse alcohol rather than with alcoholism, per se.

Adult↗

T-cell receptor BV6S1 null alleles and HLA-DR1 haplotypes in polyarticular outcome juvenile rheumatoid arthritis.

JRA is a complex of disease subtypes which are normally identified by clinical features such as age of onset and extent of joint involvement both at onset and during the course of the disease. We previously identified an association between TCR BV6S1 null allele and one subgroup of early-onset pauciarticular patients positive for HLA-DQA1*0101, an HLA haplotype predisposing to a polyarticular course of the disease. In this report we extend this observation by identifying an increased prevalence of this nonfunctional or null allele in the patients with a polyarticular disease course regardless of the mode of onset. This increase was most prominent in clinical subsets that have early onset of the disease and a polyarticular outcome. In one clinical group, stratification of patients by the HLA allele DQA1*0101 strengthened the association considerably. This implies that there is an increased genetic load defined by specific alleles of both MHC and TCR genes.

Alleles↗

Family study of acute intermittent porphyria and hereditary coproporphyria in Niigata and Akita Prefectures, Japan.

Simple screening tests, urinary porphobilinogen (PBG) for acute intermittent porphyria (AIP) and fecal coproporphyrin for hereditary coproporphyria (HCP), were performed in a family study of AIP and HCP. Urinary PBG was positive in 93 of 211 members of 10 AIP families, but was negative in 568 of 572 controls. Fecal coproporphyrin was positive in 54 of 108 members of 10 HCP families, but was negative in 188 controls. A dominant inheritance was assumed by a chi-square test and Weinberg segregation ratio. Worsening factors around puberty were suggested by the onset age and cumulative percentage of genetically loaded cases. Sex-related expression of symptoms was also inferred by a higher incidence of both porphyrias in females than in males. Fitness and penetrance of both porphyrias were good. An l-triiodothyronine loading test was the most useful for the detection of masked carriers of AIP. In conclusion, AIP and HCP in Japan show a dominant inheritance with sex-related metabolic and clinical manifestations.

Adolescent↗

Transcription factors in autoimmunity.

The identification of two transcription factors that, when mutated, are responsible for severe autoimmune disease in humans is leading to a better understanding of the fundamental processes involved in T-cell tolerance. Both AIRE and FOXP3, identified initially via their association with genetically manipulated mice, are critically involved in tolerance induction in humans. Although mutations in these genes may cause rare but serious diseases, it is likely that other transcription factors will contribute to the genetic load that predisposes certain individuals to disease.

Animals↗

Magnetic resonance relaxometry in monozygotic twins discordant and concordant for schizophrenia.

T1 and T2 relaxation times were examined in four pairs of monozygotic (MZ) twins discordant and concordant for schizophrenia with low and high genetic loading for the illness and five healthy control MZ twin pairs. Patients with schizophrenia (n = 11) showed significant prolongation in T1 relaxation times in the globus pallidus (GP) bilaterally (P < 0.005, Bonferroni corrected) when compared to 14 healthy MZ twins.

Adult↗

Secondary verbal memory: a potential endophenotype of schizophrenia.

This study aimed at identifying neuropsychological endophenotypes of schizophrenia which met the criteria of stability and sensitivity. Twenty-six non-schizophrenic first-degree relatives together with their affected family members (all simplex-families) underwent assessment with a comprehensive neuropsychological test battery both at baseline and 13 months follow-up. Follow-up patients were in a state of stable remission. Further, 21 unrelated, demographically balanced, non-vulnerable controls were tested one at a time. A principal components analysis of our test battery resulted in four factors: (1) Vigilance, attention, and psychomotor, (2) secondary verbal memory, (3) immediate and working memory, and (3) abstraction and problem solving. At baseline testing our study revealed a pattern of selective cognitive deficits in the relative group that is less pronounced, yet qualitatively similar, to that found in the patient sample. The most severe deficits displayed both the patients and their relatives in the secondary verbal memory domain. The dysfunctions in secondary verbal memory at baseline testing significantly correlated with negative symptoms only. Secondary verbal memory deficits proved to be relatively independent of age at onset of illness, illness duration, and neuroleptic dosage. Longitudinally, dysfunctions in the patients' secondary verbal memory fluctuated over time and with negative symptoms, and persisted in remitted patients at the same level as in their relatives. In conclusion, the secondary verbal memory met the criteria of relative stability and sensitivity in our sample of simplex-families. Thus, the secondary verbal memory seems to be a potential endophenotypic marker of schizophrenia, even for cases with a hypothetically lower genetic loading.

Adult↗

Seasonality effects on schizophrenic births in multiplex families in a tropical island.

Many studies have found that individuals with schizophrenia have been born in winter months in disproportionately high numbers. Temperature and weather effects, such as hot summers or cold winters, have been among the suggested explanations for this seasonality effect. We studied the relationship between schizophrenia and season of birth in Puerto Rico, a tropical island with mild seasonal variation of temperature and virtually no cold periods. Our sample consisted of 132 subjects (57 with schizophrenia, 75 without) from 24 multiplex families. Schizophrenic family members were significantly more likely to be born during the winter months (21/57; 36.8%) than their unaffected relatives (16/75; 21.3%). These results suggest that extreme temperatures are not a sufficient explanation for the seasonality effect and that other factors associated with seasonality may have an effect on the later development of schizophrenia. The fact that a seasonality effect was found in a group likely to have an increased genetic loading for schizophrenia suggests that seasonality may be associated with a second, environmental "hit" in a "two-hit hypothesis" of schizophrenia.

Adult↗

Genetic sex determination and extinction.

Genetic factors can affect the probability of extinction either by increasing the effect of detrimental variants or by decreasing the potential for future adaptive responses. In a recent paper, Zayed and Packer demonstrate that low variation at a specific locus, the complementary sex determination (csd) locus in Hymenoptera (ants, bees and wasps), can result in a sharply increased probability of extinction. Their findings illustrate situations in which there is a feedback process between decreased genetic variation at the csd locus owing to genetic drift and decreased population growth, resulting in an extreme type of extinction vortex for these ecologically important organisms.

Animals↗