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PubMed2000

Meiosis and the Neo-XY system of Dichroplus vittatus (Melanoplinae, Acrididae): a comparison between sexes.

The origin of neo-XY sex systems in Acrididae is usually explained through an X-autosome centric fusion, and the behaviour of the neo-sex chromosomes has been solely studied in males. In this paper we analysed male and female Dichroplus vittatus. The karyotype comprises 2n = 20 chromosomes including 9 pairs of autosomes and a sex chromosome pair that includes a large metacentric neo-X and a small telocentric neo-Y. We compared the meiotic behaviour of the sex bivalent between both sexes. Mean cell autosomal chiasma frequency was low in both sexes and slightly but significantly higher in males than in females. Chiasma frequency of females increased significantly when the sex-bivalent was included. Chiasma distribution was basically distal in both sexes. Behaviour of the neo-XY pair is complex as a priori suggested by its structure, which was analysed in mitosis and meiosis of diploid and polyploid cells. During meiosis, orientation of the neo-XY is highly irregular; only 21% of the metaphase I spermatocytes show standard orientation. In the rest of cells, the alternate or simultaneous activity of an extra kinetochore in the distal end of the short arm (XL) of the neo-X, determined unusual MI orientations and a high frequency of non-disjunction and lagging of the sex-chromosomes. In females, the neo-XX bivalent had a more regular behaviour but showed 17% asynapsis in the XL arm which, in those cases orientated its distal ends towards opposite spindle poles suggesting, again, the activity of a second kinetochore. The dicentric nature and the unstable meiotic behaviour of the sex neo-chromosomes of D. vittatus suggest a recent origin of the sex determination mechanism, with presumable adaptive advantages which could compensate their potential negative heterosis. Our observations suggest that the origin of the neo-sex system was a tandem fusion of two original telocentric X-chromosomes followed by another tandem fusion with the small megameric bivalent and a further pericentric inversion of the neo-X. The remaining autosomal homolog resulted in the neo-Y chromosome.

Animals↗

PubMed2002

The medicalization of female sexual dysfunction: the need for caution.

The use of drugs such as Viagra to treat sexual dysfunction in women may be beneficial in a proportion of cases. However, there are a number of barriers to understanding and predicting which women are likely to benefit, and caution is required in approaching this clinical issue. Three relevant issues are discussed: (1) Male-female differences in sexuality. Three complimentary ways in which male and female sexuality differs are considered--women have less need for their sexuality to be influenced by reproductive hormones; their needs for sexual enjoyment and orgasm are not well met by conventional vaginal intercourse; and, as a result of the disjunction between female sexual response and reproduction and a possibly greater propensity for central inhibition of sexual response, women are more susceptible to the repressive effects of social constraints on sexuality; (2) Sex therapy. While conventional forms of sex therapy are well designed to address the particular psychological needs of women as well as men, the interface between psychological processes and physiological response is not well understood. For the same reason, we should expect difficulty in predicting when pharmacological effects on sexual response will be beneficial; (3) When is a sexual problem a sexual dysfunction? It is likely that many cases of impaired sexual response or interest in women are psychologically understandable and hence adaptive reactions to problems in the sexual relationship, and hence not dysfunctions. Until we can distinguish between such adaptive inhibitions of response and those that are maladaptive dysfunctions, we will have difficulty in predicting when pharmacological treatment will be helpful.

Androgens↗

PubMed2002

A probabilistic methodology to assess the risk of groundwater quality degradation.

An approach to assess the risk of groundwater quality degradation with regard to fixed standards. based on Disjunctive Kriging (DK) is presented. The DK allows one to evaluate the Conditional Probability (CP) of overriding a given threshold of concentration of a pollutant at a given time, and at a generic point in a considered groundwater system. The result of such investigation over the considered area can be plotted in form of maps of spatial risk. By repeating this analysis at different times, several spatial risk maps will be produced, one for each considered time. By means of non-parametric statistics, the temporal trend of the CPs can be evaluated at every point of the considered area. The trend index, assessed by means of a sort of classification of the trend values obtained as described above, can be superimposed on the most recent values of the spatial risk (i.e.: the most recent values of probability). Consequently a classification of the risk of groundwater quality degradation results with which to weigh both the spatial distribution and the temporal behaviour of the probability to exceed a given standard threshold. The methodology has been applied to values of nitrate concentration sampled in the monitoring well network of the Modena plain, northern Italy. This area is characterised by intensive agricultural exploitation and hog breeding along with industrial and civil developments. The influence of agriculture on groundwater results in a high nitrate pollution that limits its use for potable purposes.

Agriculture↗

PubMed2002

How theories became knowledge: Morgan's chromosome theory of heredity in America and Britain.

T. H. Morgan, A. H. Sturtevant, H. J. Muller and C. B. Bridges published their comprehensive treatise The Mechanism of Mendelian Heredity in 1915. By 1920 Morgan's "Chromosome Theory of Heredity" was generally accepted by geneticists in the United States, and by British geneticists by 1925. By 1930 it had been incorporated into most general biology, botany, and zoology textbooks as established knowledge. In this paper, I examine the reasons why it was accepted as part of a series of comparative studies of theory-acceptance in the sciences. In this context it is of interest to look at the persuasiveness of confirmed novel predictions, a factor often regarded by philosophers of science as the most important way to justify a theory. Here it turns out to play a role in the decision of some geneticists to accept the theory, but is generally less important than the CTH's ability to explain Mendelian inheritance, sex-linked inheritance, non-disjunction, and the connection between linkage groups and the number of chromosome pairs; in other words, to establish a firm connection between genetics and cytology. It is remarkable that geneticists were willing to accept the CTH as applicable to all organisms at a time when it had been confirmed only for Drosophila. The construction of maps showing the location on the chromosomes of genes for specific characters was especially convincing for non-geneticists.

Chromosomes↗

PubMed2003

Splenic lymphocytes of adult Xenopus respond differentially to PMA in vitro by either dying or dividing: significance for cancer resistance in this species.

Wild-type populations of amphibians, unlike mammalians, appear to be resistant to spontaneous and chemically induced neoplasms. Few true cancers have been reported for non-isogeneic members of Xenopus laevis, despite their widespread use in laboratories around the world. Injection of even the most powerful direct mammalian oncogens e.g. N-methyl N-nitrosourea, that depleted specific populations of T lymphocytes, did not induce cancer. Phorbol diesters, e.g. PMA, are mitogens and apoptogens in both amphibian, and mammalian immunocytes. In mammalian cells, regulation of the cell cycle and of apoptosis are often intimately linked, however, a disjunction in time between early apoptosis and later cell cycling, has been observed with PMA-treated Xenopus splenocytes. Thus, a particular difference between amphibians and mammals may be the requirement to enter the cell cycle before a progression to death by apoptosis. This hypothesis was tested here using dual staining flow cytometry. Xenopus laevis splenocytes were cultured for 8, 24 and 48 hours with phorbol 12-myristate 13-acetate (PMA), previously shown to be mitogenic and apoptotic with mature Xenopus lymphocytes. The cells were stained with FITC-conjugated Annexin V or with FITC-labeled deoxyuridine triphosphates (FITC-dUTP) to assay for the apoptotic markers phosphotidylserine or DNA strand breaks respectively. Phycoerythrin (PE)-conjugated anti-human proliferating cell nuclear antigen (PE-PCNA) was used as a cell cycle marker that is present during the entire cell cycle. Propidium iodide (PI) binds DNA and was used to assay for late stage apoptosis, as well as to assess DNA content. Significantly higher levels of apoptosis develop rapidly in PMA-exposed splenocytes and are maintained at 24 hours, declining by 48 hours. Cells expressing PCNA or incorporating PI in excess of the normal genomic level were found by 48 hours following PMA exposure. The absence of any significant rise in a small (<5%) dual staining cell population indicates that the apoptotic cell population remained distinct from cells already in the cell cycle from the onset of PMA exposure. Thus, Xenopus splenocytes respond differentially to PMA. Those that undergo apoptosis rapidly were quiescent, non-cycling small lymphocytes. Moreover, the cells that eventually begin division, following PMA exposure, were unaffected by the early apoptosis and do not themselves die while in the cell cycle. The rapid apoptotic response of X. laevis cells to PMA may confer a natural cancer resistance in this species, as cells that fail to enter the cell cycle after exposure to cancer promoting reagents cannot express genetic destabilization that might have led to transformation.

Animals↗

PubMed1998

Preimplantation diagnosis of common aneuploidies by the first- and second-polar body FISH analysis.

PURPOSE: A low pregnancy rate in in vitro fertilization (IVF) patients of advanced maternal age may be caused by aneuploidies originating from non disjunction in the first or second meiotic divisions. We introduced genetic testing of oocytes by sampling and fluorescent in situ hybridization (FISH) analysis of the first and second polar bodies, to avoid fertilization and transfer of aneuploid oocytes in IVF patients of advanced maternal age. METHODS: Three hundred and sixty-three IVF patients 34 years and older participated in the study. Using micromanipulation procedures, the first and second polar bodies were removed following their extrusion from the oocytes and studied by FISH, using probes specific for chromosomes 13, 18, and 21 to detect oocytes with common aneuploidies. RESULTS: Of a total of 538 IVF cycles, 3250 oocytes were available for FISH analysis, with conclusive FISH results in 2742 oocytes (84.3%). As many as 1102 (40%) of oocytes were predicted to be aneuploid and not transferred. Of 1640 embryos predicted to be normal, 1145 were transferred in 467 treatment cycles, resulting in 107 pregnancies (23%), from which 67 healthy children have been born, 32 pregnancies spontaneously aborted, and 15 pregnancies are ongoing after being confirmed normal by prenatal diagnosis. CONCLUSIONS: Preimplantation diagnosis by first- and second-polar body FISH analysis allows us to avoid the age-related risk of common aneuploidies in IVF patients of advanced maternal age.

Aneuploidy↗

PubMed2003

Who are the comorbid adolescents? Agreement between psychiatric diagnosis, youth, parent, and teacher report.

The investigators examined the rates of psychiatric comorbidity for externalizing and internalizing behavior problems, using semistructured diagnostic interview and parent, teacher, and youth report on the Achenbach checklists. The study also evaluated the effects of conjunctive, compensatory, and disjunctive data combination strategies. Using the same data and identical diagnostic thresholds, between 5 and 74% of 189 youths presenting to an outpatient clinic were identified as having comorbid internalizing and externalizing problems. Parent report and semistructured interview indicated the highest comorbidity rates. Despite good cross-source agreement (rs .29-.58), there was very little agreement about which specific youths presented with comorbid internalizing and externalizing problems (kappas .14-.40). Results also indicate that single DSM-IV disorders, such as bipolar disorder, can manifest "comorbid" patterns of behavior problems on checklists.

Adolescent↗

PubMed2003

Comorbidity and child psychopathology: recommendations for the next decade.

This special section exemplifies and offers a number of important methodologic and conceptual advances that should provide investigators new tools for understanding comorbidity of child and adolescent psychopathology, including (a) the importance of making careful methodologic distinctions in how comorbidity is defined and operationalized, (b) specifying and justifying how data from different sources are combined, (c) teasing out the impact of potentially confounding risk factors that lead to symptom and syndrome overlaps, and (d) exploring the effects of time, timing, and order of disorder emergence on variable manifestations of comorbidity. These advances are much needed, but may still prove insufficient, given the daunting challenges in fully understanding comorbidity. Thus, future studies should be characterized by (a) more focused search for subgrouping factors and interactions related to the emergence of comorbidity, (b) careful exploration of setting- and/or informant-specific types of psychopathology, (c) development of studies that explore not just phenotypes and genotypes, but also environtypes and trajectory-types, (d) more discriminative use of information sources, including explicit efforts to reconcile (rather than combine) discrepant information, (e) clear descriptions and logical justification of when conjunctive, disjunctive, additive, and discriminative combinatorial approaches are used, (f) increased use of multidisciplinary research methods and teams, (g) increased application of multiple lines of evidence in comorbidity studies, (h) increased focus on understanding illness processes rather than just psychopathologic states, (i) development of creative new research designs, and (j) redrawing disorder boundaries when warranted.

Adolescent↗

PubMed1998

Analysis of mechanisms and frequency of CDKN2A/B gene loss during progression of RAS-transformed rat embryo fibroblast clones.

Rat embryo fibroblasts (REFs) are inefficiently transformed by RAS-oncogenes. Induction of p16INK4A expression by RAS has been suggested to contribute to this resistance. Glucocorticoid hormones, (DEX), enhance REF transformation by RAS and facilitates the isolation of transformed and immortal cell lines. We show that DEX induced cell proliferation is paralleled by a decrease in Cdkn2a gene transcripts, suggesting a mechanism for hormone promotion. The mechanisms of progression into hormone independent cell lines were examined. Twenty-two of 30 clones which reached a population size of approximately 10(6) cells could be established as cell lines. All lines studied showed homozygous deletions of the Cdkn2 loci (Cdkn2a and Cdkn2b) on RNO5. LOH was found for all RNO5 genetic markers examined in 7 of 19 cell lines, suggesting non-disjunction events. In the remaining 12 cell lines, both copies of Cdkn2 appeared to be lost by deletions/rearrangements, some of which could by demonstrated by karyotype analysis. We conclude that (i) clonal expansion of RAS-transfected REF by DEX is paralleled by down-regulation of Cdkn2a expression; (ii) homozygous deletion of Cdkn2 were estimated to occur at a frequency of 2 x 10(-8)/cell/generation or higher, and (iii) deletion/rearrangements and nondisjunction appear to be the main mechanisms leading to deletion of Cdkn2.

Animals↗

PubMed2000

Segregation of a supernumerary del(15) marker chromosome in sperm.

Supernumerary marker chromosomes (SMC) can be associated with both normal and abnormal phenotypes. In addition, SMC are found at higher frequency in males with infertility. We identified a SMC, characterized as a del(15)(q11.2) chromosome, in a phenotypically normal male. Using fluorescence in situ hybridization (FISH), we examined the segregation of the del(15) chromosome in sperm from this patient. Only 6.23% of sperm nuclei showed disomy using a chromosome 15 alpha-satellite FISH probe, instead of the expected 50%. In addition, FISH analysis showed no increase for non-disjunction of chromosome 18, excluding an interchromosomal effect for this chromosome. The significant decrease in sperm bearing the del(15) may be due to tissue-specific mosaicism or a result of some form of selection against the del(15) during spermatogenesis. This finding provides a basis for the observation that SMC(15) are less likely to be inherited from a paternal carrier.

Adult↗

PubMed2001

Cognitive subprocesses and schizophrenia. A. Reaction-time decomposition.

OBJECTIVE: The aim of the study is to demonstrate that deficits of information processing in schizophrenic patients can be isolated with reaction-time (RT) decomposition paradigms. METHOD: Three types of visually presented tasks were applied: simple, disjunctive and choice RT-tasks. RT were split into movement latency and time necessary to execute movements. Comparisons of three samples of schizophrenic patients (295.3) with individually matched (age, sex. education and handedness) healthy controls are presented: Sample 1: 10 drug-naive first-onset patients, Sample 2: 10 neuroleptically treated first-onset patients, Sample 3: 10 neuroleptically treated chronically ill patients. RESULTS: Findings indicate that schizophrenia affects primarily subprocesses in which percepts are translated into appropriate actions (response-selection). Neuroleptic treatment improves processing at this stage but is accompanied by slowing of movement execution. CONCLUSION: Response-selection is selectively impaired in first-onset patients. This disturbance, which might be specific for schizophrenia, can be regarded as indication of a disconnection between frontal and posterior areas.

Adult↗

PubMed1990

Conjunctive moderator variables in vulnerability and resiliency research: life stress, social support and coping skills, and adolescent sport injuries.

In life event research relating to vulnerability and resilience factors, single moderator variables have typically been the focus of study. Little is known about the ways in which moderator variables may interact with one another to increase vulnerability or resilience. We propose a distinction between conjunctive moderation, in which multiple moderators must co-occur in a specific combination or pattern to maximize a relation between a predictor and an outcome variable, and disjunctive moderation, in which any one of a number of moderators maximizes the predictor-criterion relation. Our results indicate that social support and psychological coping skills are statistically independent psychosocial resources and that they operate in a conjunctive manner to influence the relation between life stress and subsequent athletic injury in adolescents. Only athletes low in both coping skills and social support exhibited a significant stress-injury relation, and in that vulnerable subgroup, negative major life events accounted for up to 30% of the injury variance. Methodological considerations in the assessment of conjunctive moderator effects are discussed.

Adaptation, Psychological↗

PubMed1990

Close binding of identity and location in visual feature perception.

The binding of identity and location information in disjunctive feature search was studied. Ss searched a heterogeneous display for a color or a form target, and reported both target identity and location. To avoid better than chance guessing of target identity (by choosing the target less likely to have been seen), the difficulty of the two targets was equalized adaptively; a mathematical model was used to quantify residual effects. A spatial layout was used that minimized postperceptual errors in reporting location. Results showed strong binding of identity and location perception. After correction for guessing, no perception of identity without location was found. A weak trend was found for accurate perception of target location without identity. We propose that activated features generate attention-calling "interrupt" signals, specifying only location; attention then retrieves the properties at that location.

Adult↗

PubMed1997

Unpacking, repacking, and anchoring: advances in support theory.

Support theory represents probability judgment in terms of the support, or strength of evidence, of the focal relative to the alternative hypothesis. It assumes that the judged probability of an event generally increases when its description is unpacked into disjoint components (implicit subadditivity). This article presents a significant extension of the theory in which the judged probability of an explicit disjunction is less than or equal to the sum of the judged probabilities of its disjoint components (explicit subadditivity). Several studies of probability and frequency judgment demonstrate both implicit and explicit subadditivity. The former is attributed to enhanced availability, whereas the latter is attributed to repacking and anchoring.

Humans↗

PubMed2004

Demands on attention and the role of response priming in visual discrimination of feature conjunctions.

This study examined how response mapping of features within single- and multiple-feature targets affects decision-based processing and attentional capacity demands. Observers judged the presence or absence of 1 or 2 target features within an object either presented alone or with distractors. Judging the presence of 2 features relative to the less discriminable of these features alone was faster (conjunction benefits) when the task-relevant features differed in discriminability and were consistently mapped to responses. Conjunction benefits were attributed to asynchronous decision priming across attended, task-relevant dimensions. A failure to find conjunction benefits for disjunctive conjunctions was attributed to increased memory demands and variable feature-response mapping for 2- versus single-feature targets. Further, attentional demands were similar between single- and 2-feature targets when response mapping, memory demands, and discriminability of the task-relevant features were equated between targets. Implications of the findings for recent attention models are discussed.

Adolescent↗

PubMed2005

Perception of objects in natural scenes: is it really attention free?

Studies have suggested attention-free semantic processing of natural scenes in which concurrent tasks leave category detection unimpaired (e.g., F. Li, R. VanRullen, C. Koch, & P. Perona, 2002). Could this ability reflect detection of disjunctive feature sets rather than high-level binding? Participants detected an animal target in a rapid serial visual presentation (RSVP) sequence and then reported its identity and location. They frequently failed to identify or to localize targets that they had correctly detected, suggesting that detection was based only on partial processing. Detection of targets was considerably worse in sequences that also contained humans, presumably because of shared features. When 2 targets were presented in RSVP, a prolonged attentional blink appeared that was almost eliminated when both targets were detected without being identified. The results suggest rapid feature analysis mediating detection, followed by attention-demanding binding for identification and localization.

Adolescent↗

PubMed1997

Characteristics of perceptual grouping in rats.

Parametric analysis was made of the characteristics by which proximity and alignment serve as cues for perceptual grouping in rats. Rats were initially conditioned to discriminate a series of horizontal lines from vertical lines. Following training, rats were presented with test stimuli that consisted of bistable arrays of disjunct dots. A grouping cue (greater proximity, greater alignment, or both) was randomly assigned to either the horizontal or vertical orientation. The effectiveness of the cues was based on behavioral responses to the cued orientation. Results indicated that proximity served as a cue for perceptual grouping. The effectiveness of the proximity cue was less for rats than found previously in humans and, unlike humans, diminished with increased stimulus scale. Rats did not respond to alignment cues when used in isolation, although alignment facilitated grouping when used in conjunction with proximity cues. Diminished effectiveness of grouping cues likely reduces object recognition abilities, particularly for complex visual stimuli.

Animals↗

PubMed2006

Physician decision making and cardiac risk: effects of knowledge, risk perception, risk tolerance, and fuzzy processing.

Despite training, professionals sometimes make serious errors in risky decision making. The authors investigated judgments and decisions for 9 hypothetical patients at 3 levels of cardiac risk, comparing student and physician groups varying in domain-specific knowledge. Decisions were examined regarding whether they deviated from guidelines, how risk perceptions and risk tolerances determined decisions, and how the latter differed for knowledge groups. More knowledgeable professionals were better at discriminating levels of risk according to external correspondence criteria but committed similar errors in disjunctive probability judgments, violating internal coherence criteria. Also, higher knowledge groups relied on fewer dimensions of information than did lower knowledge groups. Consistent with fuzzy-trace theory, experts achieved better discrimination by processing less information and made sharper all-or-none distinctions among decision categories.

Adult↗