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Biomedical subjects

G Stephenson

Publications and source records attributed to G Stephenson.

At least 19 recordsLinked to original sources
PubMed1998

Adult cutaneous Langerhans cell histiocytosis.

A 24-year-old male presented with a 4 year history of a crusted erythematous papular eruption of the scalp and external auditory meati and a 12 month history of painful perianal ulceration. A diagnosis of Langerhans cell histiocytosis was made and confirmed by skin histology. Extensive investigation revealed no systemic involvement. Rapid improvement occurred after intravenous 2-chlorodeoxyadenosine but relapse of perianal lesions occurred within 5 months. Local radiotherapy to the perianal region resulted in a complete remission sustained over 12 months.

Adult↗
PubMed1997

Visual impairment in very low birthweight children.

AIMS: To compare the visual function of a cohort of very low birthweight (VLBW) children in early adolescence with that of their normal birthweight peers; to correlate visual impairment in this group with available perinatal data; and to examine the relation between the visual ability of VLBW children and their cognitive and motor skills. METHODS: As part of a long term neurodevelopmental study, 137 VLBW children and 163 normal birthweight controls were visually assessed between the ages of 11 and 13 years. Their eyes were examined for strabismus and movement disorders, and the use of visual correction for refractive errors was noted. Measures were made of visual acuity, stereopsis, and contrast sensitivity. All children had standardised tests of motor ability and cognitive skills. Perinatal data, including cranial ultrasonography results, had been obtained from the children's notes. No data were available however, regarding retinopathy of prematurity as screening was not established when these infants were born. RESULTS: On all measures, the visual function of the VLBW children was poorer than that of the controls. Reduced visual function was present in 63.5% of VLBW children compared with 36% of controls. Poor contrast sensitivity and strabismus were predictive of poor motor skills in the VLBW children. Poor contrast sensitivity and poor visual acuity (at 0.3 metres) were predictive of lower IQ. Low birthweight, intraventricular haemorrhage, intrauterine growth retardation and low 1 minute Apgar scores predicted reduced visual function. CONCLUSIONS: VLBW children have a high incidence of impaired vision. Stereopsis and contrast sensitivity are useful additions to the screening of this high risk group. They identified impaired vision that was not detected by normal screening and were related to impaired neurodevelopmental outcome.

Adolescent↗
PubMed1995

Spontaneous recovery rates for unilateral sixth nerve palsies.

Two hundred and thirteen patients with unilateral isolated sixth nerve palsies were assessed to determine what proportion of them underwent spontaneous recovery and over what period of time this recovery occurred. All were primary ophthalmic referrals from which trauma was excluded. In all, 78.4% of patients experienced spontaneous recovery of their palsy, 36.6% recovering by 8 weeks and 73.7% by 24 weeks. Only 16.4% failed to recover. Of this group, however, nearly 40% had serious underlying pathology accounting for their palsy.

Abducens Nerve↗
PubMed1991

Human immunodeficiency virus (HIV) sero-prevalence in sexually transmitted disease clinic populations.

Two HIV sero-prevalence surveys conducted during 1989 in public sexually transmitted disease clinics in the Kansas City SMSA tested 1,561 males and 1.043 females. There were 23 sero-positive males; no sero-positive females. The rate for males using the Missouri clinic was nearly triple that of males using the Kansas clinic. Among males the sero-prevalence rate for white males was 8.4 times that for black males. Of the 14 HIV sero-positive males for whom risk factor information was available, 12 were gay or bisexual and two were heterosexual intravenous drug users.

Adult↗
PubMed1989

Acute spontaneous subdural haematoma of arterial origin.

Spontaneous arterial subdural haematoma is arguably a rare condition. We report on three patients who presented with progressive neurological deficit or coma and who had been initially diagnosed as strokes. Explanations for the development of this condition are reviewed and it is suggested that it is not as rare as previously thought.

Aged↗
PubMed1989

Evidence that coupling factor B is bound to the matrix side of the inner mitochondrial membrane.

Rotenone-sensitive NADH dehydrogenase activity and Lubrol stimulation of cytochrome oxidase activity were measured to assess the opposite membrane polarity of beef heart mitoplast and inside-out particle preparations. The ATP-Pi exchange activity of mitoplasts was not affected by their incubation at pH 8.9 in the presence of 5 mM EDTA (a treatment known to extract coupling factor B (F beta) from submitochondrial particles), nor was it stimulated by the addition of F beta to intact and alkaline treated mitoplast preparations. In contrast, the exchange activity of inside-out particles was decreased 18 fold by the alkaline/EDTA treatment and was almost completely restored by the addition of F beta to F beta-depleted particles. From these results it is concluded that in beef heart mitochondria, the coupling factor F beta is bound to the matrix-side of the inner mitochondrial membrane.

Adenosine Triphosphatases↗
PubMed1989

Decision rules for infant feeding: the influence of maternal expertise, regulating functions, and feeding method.

Decision rules used by mothers to determine actions for tasks and events of infant feeding were described and factors contributing to their use (mothers' functions in regulating the feeding, maternal experience, and feeding method) were explored. A telephone interview surveyed 122 mothers of healthy term infants 14-60 days old. Both Decision Rules and Regulating Function (Maternal-, Infant-, or Mutual-Regulation) varied by feeding task or event examined. Decision Rules and Regulating Functions were associated only for burping during a feeding. Maternal experience (primiparity, multiparity) was not associated with either Decision Rule or Regulating Functions. For several feeding tasks or events, Decision Rule was more likely to be predicted by Regulating Function when feeding method (breast, bottle) was controlled. A mother's agenda for the feeding may be an important component of her internal working model of infant feeding and a factor in making decisions for action.

Adolescent↗
PubMed1987

A method for the purification of Leishmania promastigotes from infected phlebotomine sandflies.

We describe a method for the purification of Leishmania promastigotes, isolated from infected sandflies (Lutzomyia longipalpis) using a discontinuous density centrifugation gradient (Percoll/Homem). The sandflies, infected seven days previously with Leishmania donovani chagasi or Leishmania mexicana mexicana from culture, were homogenized and centrifuged on a Percoll discontinuous gradient. Five interface bands were formed, and most of the promastigotes settled out at the interface between the (30% and 40%) Percoll concentrations. An extraction of 3.5 x 10(4) promastigotes from 90 female flies was achieved using this technique.

Animals↗
PubMed1987

Hippocampal and renal type I receptors are differentially regulated.

Previously, we have shown that renal mineralocorticoid receptors and hippocampal "corticosterone-perferring" sites have identical intrinsic steroid specificity in vitro. Others have shown that the aldosterone binding species in kidney and hippocampus have identical trypsin fragmentation patterns on isoelectric focusing. To further explore possible areas of identity, we determined levels of type I receptors in hippocampus, renal outer medulla cortex, and renal inner medulla papilla from 22 min to 16 days after adrenalectomy. Available type I sites in kidney fractions increased postadrenalectomy to plateau levels in 22 (inner medulla papilla) or 90 min (outer medulla cortex). In contrast, available hippocampal receptors attained maximal levels 24-48 h postadrenalectomy. Animals, 24-h adrenalectomized, showed no differences in steroid uptake or washout between kidney and hippocampus, determined by in vitro tracer binding 22 or 90 min after intravenous aldosterone or corticosterone. We interpret the marked difference in receptor levels between kidney and hippocampus postadrenalectomy as evidence for tissue-specific differences in the control of receptor levels by endogenous steroids.

Adrenalectomy↗
PubMed1984

Extravascular CBG-like sites in rat kidney and mineralocorticoid receptor specificity.

To determine the intrarenal distribution of extravascular corticosteroid-binding globulin- (CBG) like sites, we measured the specific binding of [3H]corticosterone to supernatants prepared from papilla-inner medulla, outer medulla, and cortex from adrenalectomized rats. Renal papilla-inner medulla of exhaustively perfused kidneys contained 8-20 times higher concentrations of such sites than cortex or outer medulla. The ontogeny and steroid specificities of such sites were identical to those of plasma CBG; their molar concentration in the inner medulla-papilla was 4 times that of plasma CBG, consistent with local accumulation of CBG. Cytosols from all three zones bound [3H]aldosterone in the presence of RU-26988, a highly specific synthetic glucocorticoid, with high affinity (Kd 4 degrees C, 0.3-0.4 X 10(-9) M) and limited capacity (papilla-inner medulla, 23-34; outer medulla, 15-16; cortex, 12-17 fmol/mg). In papilla-inner medulla the apparent specificity of such [3H]aldosterone binding sites was aldosterone greater than corticosterone greater than dexamethasone, in contrast to aldosterone = corticosterone greater than dexamethasone in outer medulla and cortex. We propose that extravascular CBG confers mineralocorticoid specificity on the papilla-inner medulla [3H]aldosterone binding sites. In addition, given the higher levels of extravascular than intravascular CBG and the recurrent vascular architecture of the renal medulla-papilla, a countercurrent exchange model is proposed for renewable sequestration of corticosterone in the region.

Aldosterone↗
PubMed1984

Ontogeny of renal mineralocorticoid receptors and urinary electrolyte responses in the rat.

We examined the ontogeny of cytosol mineralocorticoid receptors in renal inner medulla-papilla (IM-PAP) and outer medulla-cortex (OM-CX) and of a biological response to administered corticosteroids (urinary K+/Na+ ratio). Rats at early (7-9 days), intermediate (13-15 days), and late (23-30 days) stages of maturation were used. Young rats were found to be essentially insensitive to aldosterone, in contrast to rats aged 13-15 days and older. Scatchard analysis of IM-PAP and OM-CX cytosol showed equivalent high-affinity aldosterone binding sites at all ages. The affinity of these sites was constant (Kd, 4 degrees C approximately 0.5 nM) and their concentration varied only slightly over maturation. In a series of in vivo nuclear transfer studies, the hyposensitivity to aldosterone in young rats did not seem to be due to a difference in the nuclear binding of aldosterone-receptor complexes. The resistance of the immature (7-9 days) rat kidney to aldosterone thus appears to be a postreceptor phenomenon. The maturational events allowing expression of mineralocorticoid-inducible genes in the kidney remain to be determined.

Adrenalectomy↗
PubMed1983

A computer-compatible method for observing falling asleep behavior of hospitalized children.

A family-organizational linkage framework was used to conceptualize the nighttime separation behaviors of 18 hospitalized children, ages 3 to 8, whose parents did not room-in. All children were observed for three consecutive nights during the falling asleep period. A bedtime story, tape recorded by the parent, was played on the second and third nights for one group. Frequency and duration of falling asleep behaviors were recorded and analyzed with the Senders Signals and Receivers System, a computer-compatible method of recording behavioral data. Eight conceptual behavioral categories emerged from the data: sleepy, contact, active, inactive, neutral, communication, distress, and pleasure. The story-children fell asleep sooner (23 minutes vs. 28 minutes), exhibited more sleepy behaviors, and displayed fewer active behaviors. Duration of contact behaviors also was greater in this group (22 minutes vs. 14 minutes). Hospitalized children who hear a bedtime story recorded by a parent appear to use self-soothing behaviors to cope with the separation experience.

Child↗
PubMed1981

Biogenesis of mitochondria. Defective assembly of the proteolipid into the mitochondrial adenosine triphosphatase complex in an oli2 mit- mutant of Saccharomyces cerevisiae.

A single mutation in the oli2 region of the mitochondrial DNA causes a charge alteration in a mitochondrially translated subunit of the mitochondrial ATPase (subunit 6; apparent Mr 20 000; apparent pI 6.9 and 7.1). This alteration leads to the defective assembly of the proteolipid subunit into the enzyme complex. The mutant, which is able to grow only very slowly by oxidative metabolism at 28 degrees C offers new possibilities for studying the assembly of the membrane sector (F0) into the mitochondrial ATPase complex and the role of subunit 6 in this process.

Adenosine Triphosphatases↗
PubMed1981

mit-Mutations in the structural gene of subunit III of cytochrome oxidase in Saccharomyces cerevisiae.

Two-dimensional electrophoretic analysis of the mitochondrial translation products of four mit-mutants indicate that subunit III of cytochrome oxidase is the only mitochondrial translation product affected by mutations in the oxi2 region of the mtDNA. Mitochondria of two of these mutants synthesize new products which coprecipitate with an anticytochrome oxidase antiserum and produce proteolytic digests similar to those of subunit III of the enzyme complex. These data strongly support the suggestion that the oxi2 region of the yeast mtDNA contains the structural gene of subunit III of cytochrome oxidase.

Electron Transport Complex IV↗