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Biomedical subjects

S McLeod

Publications and source records attributed to S McLeod.

At least 19 recordsLinked to original sources
PubMed2006

Rapid identification of single nucleotide polymorphisms and estimation of allele frequencies using sequence traces from DNA pools.

Millions of single nucleotide polymorphisms (SNP) are now known in the chicken, but the ones that segregate may differ among populations. The current study characterized a simple method to simultaneously identify SNP in populations and to estimate allele frequencies by using relative peak heights of nucleotides in sequencing traces from DNA pools. In the first experiment, known concentration gradients of alleles were produced by measured admixture of DNA from highly inbred individual chickens. In the second experiment, pools of DNA from 100 individuals of each of 3 populations were produced, and the estimated frequencies were compared with those from genotyping of individuals sampled from the same populations. Linear relationships (slope = 0.93 to 1.02) were demonstrated between relative peak heights of nucleotide sequence traces and allelic frequency from both types of experimental samples. The correlation of frequency estimates from pools and individual genotyping was 0.917 to 0.997. Therefore, relative peak heights of nucleotides in sequence traces from DNA isolated from blood pools provide accurate estimates of SNP frequencies of the population from which the pool individuals were sampled and can, therefore, increase efficiency of selecting SNP to genotype in specific populations.

Alleles↗
PubMed2001

Real-time measurement of glutamate release from the ischemic penumbra of the rat cerebral cortex using a focal middle cerebral artery occlusion model.

Following permanent middle cerebral artery occlusion, extracellular penumbral glutamate levels, measured by a real-time glutamate electrode, increased in two different patterns. In 7/11 rats, glutamate increased from baseline levels of 19+/-4 (mean+/-SEM) to 208+/-29 microM and then declined towards baseline levels. Blood flow in the penumbral area declined to 30% of pre-ischemic levels with recovery to 60 and 70% of baseline values by 3 and 6 h, respectively. Four of 11 rats in the study also exhibited late peaks of glutamate release (120+/-40 microM ) 2 h after the onset of ischemia. There were no changes in the EEG recordings or cerebral blood flow during these late glutamate peaks.

Animals↗
PubMed2001

Psycholinguistic models of speech development and their application to clinical practice.

This article presents an introduction to psycholinguistic models of speech development. Two specific types of models are addressed: box-and-arrow models and connectionist or neural network models. We review some historical and some current models and discuss recent applications of such models to the management of speech impairment in children. We suggest that there are two ways in which a psycholinguistic approach can influence clinical practice: by directly supplementing a speech-language pathologist's repertoire of assessment and treatment approaches and by offering a new way to conceptualize speech impairment in children.

Brain↗
PubMed2001

Consonant cluster development in two-year-olds: general trends and individual difference.

A holistic view of phonological development can be attained only through exploration of the relationship between universal developmental sequences, to establish a general pattern of development and individual learning and to provide information regarding variability. This study examined consonant cluster production, looking specifically at the relationship between general trends and individual differences as children acquire these sounds. The spontaneous speech of 16 normally developing Anglo-Australian 2-year-olds was elicited monthly for 6 months, and the corpus of 96 samples was examined using independent and relational phonological analyses. Data demonstrated that 2-year-olds were able to produce a range of consonant clusters in word-initial and word-final position, but few of the younger participants could produce consonant clusters correctly. Only half of the participants showed an increase in the percent of consonant clusters produced correctly over the 6-month period; however, their developing phonological maturity was revealed in the increase in the range and diversity of their repertoire of consonant clusters and by their closer approximations to the adult target. Specific findings of the study were compared to 10 trends for children's acquisition of consonant clusters emerging from the literature over the last 70 years.

Child Language↗
PubMed1998

Choriocapillaris degeneration and related pathologic changes in human diabetic eyes.

OBJECTIVES: To measure the extent of choriocapillaris degeneration (CCD) in diabetic choroids and to study the association of CCD with choroidal neovascularization and pathologic changes in Bruch's membrane-like basal laminar deposits. MATERIALS AND METHODS: Human choroids from 10 postmortem subjects (diabetic, 5 [group 1]; nondiabetic, 5 [group 2]) were incubated for the histochemical demonstration of alkaline phosphatase and nonspecific esterase activities, permitting analysis of the choroidal vasculature and polymorphonuclear leukocytes, respectively. The tissue was then flat embedded and sectioned for structural analysis. Areas of CCD were measured in the flat perspective by computer-assisted image analysis and verified in cross-sections of flat-embedded tissue. RESULTS: The CCD in choroids from subjects with diabetes (group 1) appeared in 2 patterns: diffuse (partial loss of alkaline phosphatase activity in a poorly defined area, ie, degeneration of some capillary segments) and focal (complete degeneration of choriocapillaris or loss of alkaline phosphatase activity in a relatively well-defined area). The mean+/-SD percentage of the choroid with focal CCD in group 1 was 5.08%+/-1.13% of the total choroidal area vs 1. 16%+/-0.35% in group 2 (P<.001). Focal CCD in group 1 was more prominent in the posterior pole than in the peripheral choroid. Choroidal neovascularization was associated with some areas of diffuse CCD in group 1. Pathologic changes in Bruch's membrane-like basal laminar deposits were often associated with CCD; the thickness of the deposits was greater in group 1 than in group 2 and greater in areas with focal CCD than in areas with diffuse or no CCD. CONCLUSION: The percentage of choroid with focal CCD in group 1 choroids was more than 4-fold greater than that in nondiabetic choroids. The presence of CCD was related to basal laminar deposits and, in some cases, to choroidal neovascularization.

Aged↗
PubMed1998

Development and application of polymerase chain reaction (PCR) tests for the detection of subgroup J avian leukosis virus.

Subgroup J avian leukosis virus (ALV) is a recently identified avian retrovirus associated with myeloid leukosis in meat-type chickens. The env gene of the HPRS-103 strain of ALV, the prototype of this subgroup, differs considerably from that of other subgroups, but shows close homology to the env-like sequences of members of the EAV family of endogenous retroviruses. Polymerase chain reaction (PCR) tests using two sets of primers were developed for the specific detection of the members of this new subgroup along with another pair of primers for detecting other subgroup viruses. The specificity and sensitivity of this detection system was compared with the conventional detection methods in experimentally and naturally infected samples. The use of PCR was found to be rapid, specific and more sensitive than the conventional diagnostic tests for the detection of ALV. Moreover, the two subgroup J ALV-specific PCR tests were found to be capable of differentiating between 'prototype-like' viruses and more recent isolates which show extensive antigenic and sequence variations. The use of this test as a rapid and sensitive method of detection of viruses in epidemiological studies and eradication programs is discussed.

Animals↗
PubMed1998

Molecular characterization of multiresistant strains of Salmonella typhi from South Asia isolated in Ontario, Canada.

Two hundred and fourteen isolates of Salmonella typhi submitted to our laboratory between 1992 and 1996 were tested for susceptibility to 20 antimicrobial agents. Forty-eight of the 214 isolates (22.4%), recovered from individuals who had travelled in South Asia, were multiresistant. Forty-four of the 48 isolates were resistant to ampicillin, chloramphenicol, tetracycline, streptomycin, sulfamethoxazole, trimethoprim, cotrimoxazole, ticarcillin, and piperacillin; the other four isolates were resistant to four to six agents. Forty-two of the multiresistant isolates belonged to Vi phage type E1, two isolates from the Punjab State belonged to phage type A, another from the Punjab State belonged to phage type E3, one isolate from Pakistan belonged to type M1, and one isolate from India belonged to type J1. Plasmids from 45 of 48 isolates showed a temperature-sensitive mechanism of transfer to Escherichia coli K-12 strains, characteristic of H1 incompatibility group plasmids. The majority of plasmids had an estimated molecular weight of 120 MDa and encoded both citrate utilization and mercury resistance. Plasmids from three isolates had an estimated molecular weight of 112-115 MDa; one of these isolates encoded citrate utilization but not mercury resistance. Analysis of isolates by pulsed-field gel electrophoresis after digestion with XbaI and SpeI indicated that the majority of multiresistant isolates shared a common restriction profile, while four isolates had unique patterns.

Adolescent↗
PubMed1996

MMPI-2 patterns in African-American females.

Researchers have reported conflicting conclusions about the relation of the MMPI (MMPI-2) clinical scale elevations and race. Consequently, this study examined the concurrent validity of the MMPI-2 in evaluating African-American females. Seventy-eight (78) African American college student volunteers were administered the MMPI-2, along with other measures of personality, achievement, and coping style. Scores revealed 76% of the sample had elevated profiles. Subjects were divided into three groups based on frequency of clinical scale code type. Subjects with the 5/9 profile elevations functioned as well as normals on measures of coping skills and mood disorders. Discussion emphasizes the importance of clinical interpretation of MMPI data in research programs and the relationship of the data to coping style.

Adaptation, Psychological↗
PubMed1994

The effect of sampling condition on children's productions of consonant clusters.

An investigation was conducted to compare the effects of single word and connected speech sampling conditions on the production of consonant clusters. Speech samples were obtained from 40 children with speech sound impairments who were aged 3 years: 6 months to 5 years. The children's productions of 36 commonly occurring consonant clusters were compared across the two sampling conditions. Overall children's productions were more similar than different. Differences between the sampling conditions were apparent for three of the eight phonological processes studied, namely, cluster reduction, final consonant deletion, and epenthesis. Of 12 fine phonetic variations, only aspirated stops showed a significant difference between the sampling conditions. There was a wide range of individual variation.

Child Language↗
PubMed1993

Anxiolytic-like action of neuropeptide Y: mediation by Y1 receptors in amygdala, and dissociation from food intake effects.

Evidence from animal and human studies suggests that neuropeptide Y (NPY) may be a potent endogenous anxiolytic. The anatomic structures mediating this action of the peptide remain unknown. Furthermore, in addition to its anxiolytic-like effects, intracerebroventricular administration of NPY induces food intake through hypothalamic mechanisms, making the anxiolytic-like action of the peptide more difficult to interpret. The purpose of this study was to examine the anatomic substrate for the effects of NPY on anxiety, and to characterize the NPY receptors mediating these effects. Intracerebroventricular injection of NPY produced increased food intake in free-feeding animals, and dose-dependent anticonflict/anxiolytic-like effects in an established animal model of anxiety, the Geller-Seifter punished responding test. In contrast, microinjection of NPY into the central nucleus of the amygdala did not increase food intake in free-feeding animals, did not affect unpunished lever pressing for food, but did reproduce the anticonflict/anxiolytic-like effect with high potency. The selective NPY-Y1 agonist, p[Leu31,Pro34]NPY was approximately equipotent with native NPY in the conflict paradigm, and markedly more potent than the Y2 agonist, NPY13-36. Intrastriatal injections had no effect on conflict behavior. Thus, activation of Y1 receptors in the central nucleus of the amygdala produces effects similar to established anxiolytics without affecting food intake, suggesting that Y1-receptors in the amygdala may be a substrate for anxiolytic actions of NPY.

Amygdala↗
PubMed1992

Anxiolytic-like effect of neuropeptide Y (NPY), but not other peptides in an operant conflict test.

The peptide messengers neuropeptide Y (NPY), growth hormone-releasing hormone (GHRH), atrial natriuretic peptide (ANP) and beta-endorphin (BEND) were tested in an animal model of anxiety, the Geller-Seifter conflict test. Rats were subjected to a multiple schedule consisting of three components: in the first component, lever-pressing produced food-reward ('unpunished responding'). The second component was a time-out period, during which lever-pressing had no consequences. During the third component, lever-pressing produced food-reward, but was also punished by an incremental foot-shock ('punished responding'). After establishing a stable baseline of both unpunished and punished responding, animals were injected with various doses of NPY, GHRH, ANP, BEND, or with saline into the lateral cerebral ventricle, and testing was repeated. While changes in unpunished responding can reflect alterations in performance factors or motivational strength, increases in punished responding have previously been shown to be highly specific for anxiety-reducing drugs, such as the benzodiazepines. NPY markedly and dose-dependently increased punished responding. A smaller increase of unpunished responding was also seen. These results add further support to the hypothesis that NPY may be an endogenous anxiolytic. GHRH, ANP and END did not affect punished responding.

Analysis of Variance↗
PubMed1992

Pregnane steroid alphaxalone attenuates anxiogenic behavioral effects of corticotropin releasing factor and stress.

The 3 alpha-hydroxy A-ring-reduced steroid alphaxalone was examined for its ability to block stress-induced behavioral effects. Alphaxalone (3 and 6 mg/kg, IP) significantly antagonized the response-suppressing effects of corticotropin releasing factor (CRF) (0.5 micrograms, ICV) on punished responding in a conflict paradigm. In the plus maze, alphaxalone (3 and 6 mg/kg, IP) blocked the anxiogenic behavioral effects produced by a prior ambient-temperature swim stress. These doses of alphaxalone produced no intrinsic effects on plasma ACTH levels, nor did they attenuate CRF-induced increases in plasma ACTH. These findings support the hypothesis that some pregnane steroids may be involved in the modulation of an animal's behavioral response to stress and suggest that these effects may occur independently of the hypothalamic-pituitary-adrenocortical axis.

Adrenocorticotropic Hormone↗