Search PubMed⌕ Search

Biomedical subjects

J M Connor

Publications and source records attributed to J M Connor.

175 records · Page 10Linked to original sources
PubMed1978

Responses of boys and girls to aggressive, assertive, and passive behaviors of male and female characters.

Boys and girls in grades 4, 6, and 8 answered five questions after reading stories in which a male or female character behaved aggressively, assertively, or passively. As hypothesized, the results indicated differential degrees of approval for aggressive, assertive, and passive behavior depending upon the sex of the character engaged in the behavior. Boys and girls also responded in different ways to the three types of behavior. Developmental trends indicated an increasingly positive evaluation of the effectiveness of passive behavior by females and an increasingly negative evaluation by males with age. The implications for the acquisition of sex-stereotyped behavior patterns are discussed.

Adolescent↗
PubMed1978

Sex-related differences in response to practice on a visual-spatial test and generalization to a related test.

93 first graders (mean age 6.5 years) were given a pretest and posttest on half of the items from the Children's Embedded Figures Test. Half of the children were randomly assigned to a training condition and received a brief training procedure on visual-spatial disembedding prior to the administration of the posttest. Children in the control condition received no training. The performance of girls improved significantly more from pretest to posttest than the performance of boys. Boys and girls showed similar beneficial effects of training in addition to the benefit of direct practice. The tendency that was observed for boys to perform higher than girls on the pretest, p less than .10, was not evident on the posttest. Scores on the pretest predicted scores on a different measure of visual-spatial ability only for children in the control group. The results are interpreted in terms of current theories of sex differences in visual-spatial perception.

Child↗
PubMed1978

Training visual-spatial ability in EMR children.

Educable mentally retarded children were randomly assigned to either a visual-spatial training condition or a control group. The children who received training showed a gain from pretest to posttest on the Children's Embedded Figures Test that corresponds to approximately 4 years of maturation in nonretarded children. The performance of the children in the control group on the posttest was not significantly different from their performance on the pretest. Correlations between measures of visual-spatial ability and the employment adjustment of retarded persons obtained by other investigators suggest the potential importance of developing the visual-spatial skills of this population.

Adolescent↗
PubMed1978

Developmental trends in the processing of multidimensional stimuli.

The ability to process variations in two dimensions of a visual stimulus as efficiently as variations in one dimension was examined in a choice--reaction-time paradigm. Kindergarten children (N = 23), second graders (N = 37), fourth graders (N = 36), and college students (N = 29) were asked to determine which of three simultaneously presented geometric stimuli was different from the other two. The number of dimensions on which the different stimulus was unlike the other two was varied. Sets of trials were also either homogeneous or heterogeneous with respect to the type of dimensional variation presented in the set. The results indicated a developmental change, which is essentially complete by ten years of age, from serial to parallel processing of dimensions.

Adult↗
PubMed1977

Similarities and differences in encoding processes in chronic schizophrenics and normals.

The encoding of visual stimuli was compared for 9 female chronic nonparanoid schizophrenics and 9 normals using the Sternberg paradigm. This paradigm allows an examination of several hypothetical stages in information processing using a reaction time measurement. Degradation level (degraded vs nondegraded), type faces of letter stimuli (varied versus constant type face), and order of degradation levels (mixed or constant level across a block of trials) were manipulated in order to examine differences in encoding process between the two groups. Results suggest two subprocesses in encoding, only one of which is defient in schizophrenics. Additional processing of encoded information at a memory stage may be comparable in normal schiziphrenics. Chronic schizophrenics are also more easily disrupted by the context of varying stimulus conditions such as mixing degradation levels and type faces. This finding suggests schizophrenic perseveration in encoding processes.

Adult↗
PubMed1977

Abstraction and use of categorical and physical information: a developmental study.

Children in nursery school and Grades 1, 3, and 5 (total N equal to 75) were asked to match one of two picture choices to a previously presented stimulus. Two types of matches were based upon the physical information in the stimuli and two types of matches were based upon categorical information. A comparison of mean reaction time for the two physical matches indicated a large change between nursery school and Grade 1 in the ability to use specific visual information in the matching of pictures of familiar objects. The efficiency of matches based upon category information showed a steady increase across the ages tested. Category matches based upon pictorial information were as efficient as category matches based upon verbal information for all groups.

Age Factors↗
PubMedDate not supplied

Linkage analysis in a large family with nonspecific X-linked mental retardation.

We report on a large 5-generation family with "nonspecific" X-linked mental retardation. Nine living affected males have an IQ between 50 and 70 but have normal stature, facial appearance, and testicular volumes and no other abnormalities. Two obligate carrier females had borderline intellectual abilities and visual-psychomotor difficulties similar to those seen in affected males. Results of chromosome studies, including fragile X, were normal in males and females. Linkage analysis was undertaken, with 19 X-specific chromosomal restriction fragment length polymorphisms (RFLPs), giving a maximal LOD score of 1.60 at a 0.10 recombination fraction for F9, suggesting a localization to distal Xq for the mutant gene in this family.

DNA Probes↗
PubMedDate not supplied

Linkage analysis in the fragile X syndrome using multiple distal Xq polymorphic DNA markers.

Linkage data using the polymorphic loci F9, DXS105, DXS98, DXS52, DXS15, and F8 and the DNA probe 1A1 are presented from 14 families segregating for fragile X [fra(X)] syndrome. Recombination fractions corresponding to the maximum LOD scores obtained by two-point linkage analysis suggest that DXS98 (Zmax = 3.23, theta = 0.0) and DXS105 (Zmax = 2.09, theta = 0.0) are the closest markers proximal to FRAXA and that DXS52 is the closest distal marker (Zmax = 3.55, theta = 0.16). FRAXA is located within a 25 cM interval between F9 and DXS52, coincident with DXS98, on multipoint linkage analysis. Phase-known three way crossover information places F8 outside the cluster (DXS52, DXS15, 1A1). Confidence limits for the markers DXS98 and DXS52 are relatively wide (0.0-0.15 and 0.06-0.31, respectively), but when used in combination with cytogenetic examination offer improved carrier detection in comparison with cytogenetic analysis alone.

Blotting, Southern↗
PubMedDate not supplied

Detection of seven point mutations in the porphobilinogen deaminase gene in patients with acute intermittent porphyria, by direct sequencing of in vitro amplified cDNA.

Direct cDNA sequencing has been performed on asymmetrically amplified transcripts from the human porphobilinogen deaminase gene. Lymphocytes from 30 patients with acute intermittent porphyria were the source of mRNA; of the seven separate point mutations detected, three were silent, whereas four resulted in amino acid changes. Three of these changes involved highly conserved amino acids, and the remaining one a conserved charge. One of these mutations was predicted to cause structural alterations in the protein product. The application of this method to affected families allows the direct identification of these heterogeneous mutations, thus permitting the unequivocal detection of carriers.

Base Sequence↗
PubMedDate not supplied

Placental synthesis of oestriol in Down's syndrome pregnancies.

In the second trimester, oestriol is synthesized in the placenta and secreted into the maternal circulation. 16alpha-hydroxy dehydroepiandrosterone sulphate (16alpha-OH-DHEAS) is formed in the fetal liver by hydroxylation of dehydroepiandrosterone sulphate (DHEAS) and transported to the placenta where it undergoes desulphation by steroid sulphatase (STS) and aromatization to oestriol. Maternal serum levels of unconjugated oestriol (UE3) are lower in Down's syndrome pregnancies than in unaffected pregnancies in the second trimester. The underlying cause of this variation was investigated in placenta, fetal liver, maternal serum and amniotic fluid from Down's syndrome pregnancies by measuring the levels of UE3, DHEAS and STS in appropriate tissues and in corresponding samples from unaffected pregnancies. UE3 levels, expressed as multiples of the control median at the appropriate gestation (MOM), were lower in placental tissue (0.52 MOM), maternal serum (0.65 MOM) and amniotic fluid (0.61 MOM) than in unaffected pregnancies. There was a significant correlation between placental and maternal serum levels of UE3 in the Down's syndrome cases. The median STS activity in placental tissue from Down's syndrome pregnancies (1.14 MOM) was not significantly different from that of the control pregnancies (1. 01 MOM), suggesting that placental turnover of the fetal precursor DHEAS is not reduced. However, levels of DHEAS were reduced in maternal serum (0.69 MOM), placental tissue (0.54 MOM) and fetal liver (0.65 MOM) from Down's syndrome pregnancies. Thus, a diminished supply of the fetal precursor DHEAS may be the cause of the decreased placental production of UE3 in Down's syndrome pregnancies in the second trimester.

Arylsulfatases↗
PubMedDate not supplied

Placental and maternal serum inhibin-A and activin-A levels in Down's syndrome pregnancies.

The objective of this study was to analyse the levels of inhibin-A and activin-A in maternal serum and placental tissue from Down's syndrome (DS) pregnancies. Inhibin-A and activin-A levels were determined by specific immunoassays and individual results were expressed as multiples of the control median (MoM) at the appropriate gestation. Immunohistochemistry was used to localize inhibin alpha and beta(A)-subunits in a selection of placental sections. In DS pregnancies, median inhibin-A levels were found to be significantly elevated to 1.46 MoM (P< 0.05) in placental extracts, and 2.06 MoM (P< 0.0001) in maternal serum, when compared with uncomplicated pregnancies. Median activin-A MoMs were also elevated in placental extracts and maternal serum to 1.62 MoM (P< 0.01), and 1.26 MoM (P< 0.05), respectively. Immunohistochemistry revealed that the alpha subunit of inhibin-A and the beta(A)subunit of inhibin-A and activin-A were mainly localized to the trophoblastic layer of placental villi. Semiquantitative studies of staining intensity revealed a trend towards stronger staining of placental trophoblasts and stroma of DS tissues, although this was statistically significant only for beta(A)subunit staining of trophoblasts (P< 0.05). These results support the hypothesis that maternal serum levels of inhibin-A and activin-A are elevated due to increased production in the placenta, and increased immunostaining of trophoblasts suggests that this may be due to increased production in the trophoblasts.

Activins↗
PubMedDate not supplied

Identification of two novel mutations in the hydroxymethylbilane synthase gene in three patients from two unrelated families with acute intermittent porphyria.

We have screened the hydroxymethylbilane synthase cDNAs of 3 patients from 2 families suffering from acute intermittent porphyria (AIP) from Scotland and South Africa using heteroduplex and chemical cleavage of mismatch analyses. Direct sequencing was used to characterise the mutations. The two novel mutations identified were a missense mutation at nucleotide position 64 in exon 3 (R22C) and a single base-pair deletion in exon 15. These mutations are predicted to affect the normal function of the enzyme and, therefore, are expected to be the primary cause of disease in these patients.

Female↗