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Biomedical subjects

J A Mitchell

Publications and source records attributed to J A Mitchell.

At least 217 records · Page 12Linked to original sources
PubMed1987

Erythrocyte complement receptor type 1 (CR1) expression and circulating immune complex (CIC) levels in hydralazine-induced SLE.

Family studies were carried out to look at CR1 expression in 24 hydralazine-induced SLE patients (Hz Reactors), who had been off the drug for at least 1 year and were clinically well at the time of the study. Mean expression of CR1 was reduced by 27% in the group of hypertensives who had developed Hz-induced SLE compared with a group of 35 normal individuals. CR1 expression was also slightly reduced in the relatives of the Hz Reactors compared to the normal group. Using a solid-phase Clq binding assay, CIC levels were found to be elevated in the plasma of the Hz reactors and an inverse relationship was found between CR1 levels and CIC levels in this patient group. Both CR1 levels and CIC levels in Hz Reactors and normal individuals were constant over the 36 weeks studied. This study suggests that there is an association between an inability to deal efficiently with CIC and susceptibility to developing Hz-induced SLE.

Antigen-Antibody Complex↗
PubMed1986

CHARGE syndrome. Part II. Hearing loss.

CHARGE is a mnemonic for a syndrome with multiple congenital anomalies that occurs with normal chromosomes. The unique external ear anomalies have been described in CHARGE Syndrome Part I in this journal. This report describes the distinctive middle ear and sensorineural losses that occur in the syndrome, both of which can be progressive and, in most cases, are moderate to severe. There is evidence to indicate that these losses are due to congenital ossicular anomalies, eustachian tube dysfunction from craniofacial malformation, and cochlear involvement that is greatest for high frequencies.

Abnormalities, Multiple↗
PubMed1986

The spectrum of clinical features in CHARGE syndrome.

Fifteen patients with CHARGE syndrome are described, nine sporadic and six familial. A recognizable pattern of malformations is present which appears to constitute a syndrome rather than a non-random association. In addition to acronymic features of Coloboma, Heart disease, Atresia of the choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies, other important diagnostic features include facial paralysis and feeding problems suggestive of velopharyngeal incompetency. A square facial appearance with asymmetry and malar flattening is characteristic, and long philtrum or prominent nasal columella may be present. Characteristic external ear anomalies and a 'wedge'-shaped audiogram may be unique to this syndrome. Short stature and hypogonadism with genital hypoplasia is pituitary or possibly hypothalamic in origin. Each feature varies from normal to severe involvement including mental function, and no single feature appears to be necessary for diagnosis.

Abnormalities, Multiple↗
PubMed1985

Neurofibromatosis and fragile-X syndrome in the same patient.

We report on an 11 1/2-year-old boy with neurofibromatosis and the fragile-X syndrome. Clinical manifestation of neurofibromatosis include multiple cafe-au-lait spots, axillary freckles, congenital glaucoma, relative macrocephaly, radiologic findings of overtubulation of the long bones, and precocious puberty. The fragile-X syndrome manifests itself as mental retardation with behavior problems, macro-orchidism, and specific cytogenetic findings. The boy has normal serum hormone levels, but a greatly elevated FSH on a first morning void, which contains the nocturnally secreted gonadotropins. This seems to be the first reported occurrence of the fragile-X syndrome with another inherited disease.

Child, Preschool↗
PubMed1985

Use of an expert model to test diagnostic criteria in CHARGE syndrome.

AI/GEN is an expert model of the diagnosis of deaf-blind syndromes that uses the EXPERT system developed by Rutgers University. Its knowledge structure employs criteria tables for diagnosis of the three types of CHARGE syndrome. The system has been used to test the published diagnostic criteria against the revised expert criteria, the latter being significantly more accurate than the former. The two sets of criteria are also compared with respect to the specificity and sensitivity of diagnosis. Expert systems can be of direct use to experts in refining and revising their diagnostic criteria.

Abnormalities, Multiple↗
PubMed1985

Effects of high frequency oscillatory ventilation compared to conventional ventilation upon pulmonary vascular prostanoid production in neonatal piglets.

In order to investigate the possibility that high-frequency oscillatory ventilation (HFO) might preferentially stimulate intrapulmonary prostacyclin (PGI2) synthesis thereby decreasing pulmonary vascular smooth muscle tone, we determined pulmonary prostacyclin and thromboxane production in neonatal piglets ventilated by conventional means and by HFO (8 Hz). There was no detectable release of prostacyclin or thromboxane into blood passing through the lungs (i.e., pulmonary arterial concentrations were greater than aortic concentrations) during ventilation by conventional means or during HFO. Furthermore, there were no differences between the two modes of ventilation in cardiac output, systemic or pulmonary vascular resistance, or pulmonary vascular response to hypoxia/hypercapnia. We conclude that HFO does not stimulate pulmonary prostacyclin production and does not affect pulmonary vascular resistance or the pulmonary vasoconstriction associated with alveolar hypoxia/hypercapnia when compared to conventional ventilation in anesthetized newborn piglets.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Response-reinforcer associations after caudate-putamen lesions in the rat: spatial discrimination and overshadowing-potentiation effects in instrumental learning.

Experiment 1 demonstrated that rats with caudate-putamen lesions show an impairment in the acquisition and reversal of a spatial maze task when compared with unoperated control subjects. Experiment 2 examined lever-press responding supported by a variable interval schedule in three groups of subjects: a group with caudate-putamen lesions, a group with lesions of the posterior cortex, and an unoperated control group. The presentation of a 0.5-s, response-contingent light correlated with reinforcement generated an elevated response rate in the two operated groups but tended to suppress responding in the control group, perhaps by overshadowing the response-reinforcer relation. Only the group with cortical lesions maintained the elevated rate when the light was uncorrelated with food delivery. Experiment 3 confirmed for these same subjects that caudate-putamen lesions produce a spatial learning deficit. No deficit was seen in the posterior cortex group. It is suggested that caudate-putamen lesions disrupt the mechanism underlying the response-reinforcer association upon which spatial maze learning and free operant responding in part depend.

Animals↗
PubMed1985

Partial trisomy 6p and partial monosomy 9p from a de novo translocation 46,XY, -9, +DER(9)T(6:9)(p211:p24).

This report describes an adult male with a partial trisomy 6p(p211-pter) and a partial monosomy 9p(9p24-pter) resulting from a de novo unbalanced translocation. This patient does not show the classical featured of the 9p partial monosomy syndrome, thus disputing the claim of Hoo et al. (1982) that 9p24 is the critical segment for the monosomy syndrome. Partial trisomy for 6p has only been previously reported in children. In addition to the chromosomal anomalies, the patient has autosomal recessive spinal muscular atrophy with a different age of onset than two affected sibs. Finally, he shows unusual audiologic and ophthalmologic signs nor previously reported as part of the 9p monosomy or 6p trisomy syndromes.

Abnormalities, Multiple↗
PubMed1985

Effects of nicotine on oviducal blood flow and embryo development in the rat.

Nicotine (5.0 mg/kg) was injected (s.c.) twice daily on Day 1 or Days 1-4 or 1-5 of pregnancy. Cumulative doses of nicotine retarded embryo cell cleavage and substantially reduced embryo cell number (saline vs nicotine: 42.5 +/- 1.7 vs 22.1 +/- 1.9 nuclei/embryo, at 12:00 h on Day 5; P less than 0.05). However, treatment for even 1 day (Day 1) significantly reduced cell number (saline vs nicotine: 42.5 +/- 1.7 vs 30.5 +/- 0.9, at 12:00 h day on Day 5; P less than 0.01). Nicotine injection also resulted in a marked and prolonged reduction in oviduct blood flow (pretreatment vs 90 min after nicotine: 0.61 +/- 0.06 vs 0.37 +/- 0.10 ml/min . g-1; P less than 0.005). The results indicate that, in the rat, even a brief exposure to nicotine, the chief alkaloid of tobacco, reduces oviducal blood flow and the rate of embryo cell proliferation. The embryo is therefore susceptible to the effects of nicotine before implantation.

Animals↗
PubMed1985

Dominant CHARGE association.

We had the opportunity to examine eight individuals in four generations of a family with dominant CHARGE association. In three generations there were five affected individuals. The 25-year old male proband had coloboma of the iris, retina and optic disc, mental retardation, hypogonadism, malformed ears, and mixed hearing loss. His 19-year old sister had colobomas of the retina, choroid, and disc, mental retardation and malformed ears. The mother of these two individuals had coloboma of the retina, choroid, and optic disc, dull mentality, and mixed hearing loss. The proband's maternal grandmother had peripapillary staphylomatous changes of the disc, mixed hearing loss, and malformed protruding ears. The proband's maternal uncle had mental retardation, hypogonadism, mixed hearing loss, protruding ears, but no colobomas. All of the affected individuals had a distinct configuration to the midface, including malar hypoplasia, prominent nasal columnella and a long nasal philtrum. The inheritance of the CHARGE association in this family would appear to be autosomal dominant. However, as the males have not reproduced, it is not possible to rule out X-linked dominant inheritance.

Abnormalities, Multiple↗
PubMed1984

Optic neuritis.

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Adrenal Cortex Hormones↗
PubMed1984

Cardiovascular effects of leukotrienes in neonatal piglets. Role in hypoxic pulmonary vasoconstriction?

We investigated the effects of exogenous leukotriene D4, synthesis inhibitors, and a leukotriene receptor antagonist upon chloralose anesthetized, mechanically ventilated, neonatal piglets with constant left pulmonary blood flow and upon piglets with uncontrolled pulmonary blood flow. Leukotriene D4 (100-10,000 ng, intravenously) caused dose-dependent increases in peak tracheal pressure, pulmonary vascular resistance, and systemic arterial pressure. In a limited number of experiments, cardiovascular responses to exogenous leukotriene C4 were qualitatively similar but quantitatively less than those to leukotriene D4. Neither treatment with diethylcarbamazine or the lipoxygenase inhibitor nordihydroguaiaretic acid, nor with the leukotriene receptor antagonist, FPL55712, altered any baseline cardiovascular parameter measured, suggesting the absence of any influence of leukotrienes on resting hemodynamics. Hypoxia or hypoxia combined with mild hypercapnia caused pulmonary vasoconstriction. Neither treatment with diethylcarbamazine or the lipoxygenase inhibitor nordihydroguaiaretic acid, nor with the leukotriene receptor antagonist FPL55712, altered the pulmonary vasoconstrictor response to hypoxia or combined hypoxia/hypercapnia. We conclude that endogenous leukotrienes do not appear to have an influence on resting cardiovascular function, neither do they appear to be necessary for hypoxic pulmonary vasoconstriction in the neonatal piglet, although exogenous leukotrienes are capable of producing cardiovascular effects.

Animals↗
PubMed1983

Autoshaping and paleostriatal lesions in the pigeon.

Three experiments were conducted with the pigeon (Columbia livia) to investigate the effects of bilateral electrolytic lesions of the paleostriatum on classical conditioning paradigms. In Experiment 1 naive subjects were given autoshaping training to a white centre key light and it was found that paleostriatal pigeons showed higher peck rates than unoperated controls. A further group of naive paleostriatal pigeons showed higher rates of autoshaped responding but did not differ from controls on a successive autoshaping discrimination with colour (Experiment 2A) or striped (Experiment 2B) stimuli. In Experiment 3 paleostriatal pigeons performed better than controls on a go, no-go alternation. The higher response rates shown by paleostriatal pigeons during autoshaping could not readily be explained in terms of a (non-associative) motor disturbance such as a tremor which could have caused multiple key pecks to be emitted in view of the demonstrations of unimpaired discrimination (Experiment 2) and better alternation (Experiment 3). Instead, the results suggest that paleostriatal pigeons may show potentiated classical conditioning.

Animals↗
PubMed1983

Paleostriatal lesions in the pigeon (Columba livia) potentiate classical conditioning: evidence from fixed-interval responding, free operant go-no-go discrimination, and alternation.

The paleostriatum augmentatum was the major site of interest for four experiments in which pigeons were given bilateral electrolytic lesions. Experiment 1 investigated the effects of lesions on key pecking for reinforcement on a 1-min fixed-interval schedule. The lesions were found to increase total response rates, but response timing was not disrupted in paleostriatal pigeons. In Experiment 2, naive subjects were given variable-interval baseline training and, in contrast to the results of Experiment 1, paleostriatal lesions did not increase responding. Go-no-go discrimination, which followed baseline training, revealed enhanced positive behavioral contrast in paleostriatal subjects, which was explained in terms of additivity theory, and together, the results of Experiments 1 and 2 suggested potentiated classical conditioning and paleostriatal pigeons. In Experiment 3, naive subjects were given spatial alternation training, and performance was temporarily impaired following paleostriatal lesions. The same paleostriatal subjects showed superior differentiation performance in Experiment 4 with a classical go-no-go alternation procedure (which also suggested potentiated classical conditioning), and it is argued that disruption of (irrelevant) response-produced information may account for paleostriatal superiority.

Animals↗