Biomedical subjects

A S Brown

Publications and source records attributed to A S Brown.

At least 19 recordsLinked to original sources

PubMed1992

Insulin-like growth factor-1, growth hormone-dependent insulin-like growth factor-binding protein and growth in children with chronic renal failure.

Insulin-like growth factor-binding protein-3 (IGFBP-3) and insulin-like growth factor-1 (IGF-1) levels were measured by specific radioimmunoassays in children with all degrees of chronic renal failure (CRF). Study group 1 comprised 29 children (10 on dialysis) who had been studied one to four times over 2 years to determine whether IGF-1 and IGFBP-3 levels differed from those in age-matched healthy children and to examine the relationship between these levels and heights. IGF-1 and IGFBP-3 levels did not differ from those in normal children. IGF-1 and IGFBP-3 were significantly correlated, increased with pubertal stage in all children and with age in non-dialysis patients. IGF-1, but not IGFBP-3, correlated with age in dialysis patients. There was no correlation between IGF-1 or IGFBP-3 levels (corrected for age) and height standard deviation score (SDS) in either non-dialysis or dialysis patients. Study group 2 comprised 19 children (7 on dialysis) who were studied prospectively for 1-2 years to examine the relationship between IGF-1 and IGFBP-3 levels, growth rates and nutritional parameters. Mean values of IGF-1 and IGFBP-3 (corrected for age) did not change over 1-year periods, while height SDS fell by -0.38 +/- 0.21 SD/year in dialysis patients and by -0.11 +/- 0.29 SD/year in non-dialysis patients. No significant correlations were found between IGF-1 or IGFBP-3 levels and growth rates or nutritional parameters. Thus growth retardation in children with CRF is not related to circulating levels of IGF-1 or IGFBP-3.

Adolescent↗

PubMed1992

Endozepine/diazepam binding inhibitor in adrenocortical and Leydig cell lines: absence of hormonal regulation.

One of the many effects which have been attributed to the peptide endozepine/diazepam binding inhibitor (Ep/DBI) is the stimulation of adrenocortical and testicular Leydig cell mitochondrial steroidogenesis. We have used two cell lines (Y-1 mouse adrenal cell tumour and MA-10 mouse Leydig cell tumour), both of which exhibit hormone stimulated steroid production, to investigate the role of Ep/DBI in acute hormone stimulated steroidogenesis. The time course of incorporation of 35S-translabel into Ep/DBI and its turnover rate when the isotope was removed were examined. Cell samples were extracted and separated on Sep-Pak C18 columns and analysed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis followed by fluorography as well as by direct scintillation counting. This allowed us to estimate the in vivo half-life of Ep/DBI and also to investigate the hormonal dependence of the peptide. Data presented here suggest that (i) Ep/DBI levels are not regulated by trophic hormones in these steroidogenic cell lines, and (ii) that the peptide has a relatively long half-life (greater than 3 h), a finding incompatible with suggestions of it having a rapid turnover. Therefore, it seems unlikely that control of Ep/DBI steroidogenic effects is via hormonal modulation of the peptide levels.

Adrenal Cortex↗

PubMed1992

Ophthalmologic examination of the normal eye of the koala.

The ophthalmic examination of the koala (Phascolarctos cinereus) was undertaken to describe the normal in vivo structure. Twenty-two of 28 koalas examined were found to have normal eyes. Slit-lamp examination revealed unusual lamellae in the cornea, and mean keratometric readings were 59.3 +/- 3 diopters, corneal endothelial cell area of 381.4 microns2 +/- with a standard deviation of 46.8 microns2. No particular features were seen which would explain the susceptibility of this animal to ocular infection by Chlamydia psittaci.

Animals↗

PubMed1992

Keratitis in free-ranging koalas (Phascolarctos cinereus) on Magnetic Island, Townsville.

Seventy free-ranging koalas (Phascolarctos cinereus) from Magnetic Island (Queensland, Australia) underwent an ocular examination, blood collection and serological examination for Chlamydia psittaci antibodies, and an examination of their teeth and genitalia. In 12 koalas long-standing unilateral keratitis was noted and in another 10 animals long-standing bilateral keratitis was observed. All animals were seronegative for Chlamydia psittaci and apart from some nasal discharge and a variety of assorted medical findings there was no sign of chlamydial infection. These ocular findings probably represent a new disease of unknown etiology.

Animals↗

PubMed1992

Is routine cervical spine radiographic evaluation indicated in patients with mandibular fractures?

Fractures of the mandible are commonly seen in most urban trauma centers. Over the past decade, the authors have seen a rise in these injuries secondary to an increase in drug and alcohol abuse, violent crime, and high-speed motor vehicle accidents. Several reports have described an association between mandibular fractures and cervical spine injuries and recommend routine cervical spine radiographs in all patients with mandibular injuries. These studies have failed to show a "cause and effect" relationship because of concomitant injuries found in these patients. This study reviews mandibular fractures and cervical spine injury retrospectively and prospectively over a 3-year period. The retrospective study included patients with isolated mandibular fractures who came to Cooper Hospital/University Medical Center Emergency Room in 1987. Thirty patients were identified, 18 of whom had cervical spine x rays. No patients had a significant radiologic or clinical cervical spine injury. The prospective study included all patients with mandibular fractures seen in the emergency room during 1988 and 1989. Seventy-three patients were identified, 44 of whom had mandibular and cervical spine radiographs. None had a significant radiologic or clinical cervical spine injury. The authors conclude that routine cervical spine x rays are costly and unnecessary. Also, any patient with a suspicion of concomitant cervical spine injury (i.e., patients with a loss of consciousness, multi-organ system injury, cervical pain or tenderness, or intoxication from alcohol use) should have cervical spine x rays, including anteroposterior, lateral, and open-mouth odontoid views.

Academic Medical Centers↗

PubMed1991

Recanalization of chronically occluded aortocoronary saphenous vein bypass grafts by extended infusion of urokinase: initial results and short-term clinical follow-up.

Chronic occlusion of saphenous vein aortocoronary bypass grafts is a common problem. Although percutaneous transluminal angioplasty of a saphenous vein with a stenotic lesion is feasible, angioplasty alone of a totally occluded vein graft yields uniformly poor results. Patients with such occlusion are often subjected to repeat aortocoronary bypass surgery. Experience with a new technique that allows angioplasty to be performed in a totally occluded saphenous vein bypass graft is reported. This technique utilizes infusion of prolonged low dose urokinase directly into the proximal portion of the occluded graft. Forty-six consecutive patients with 47 totally occluded grafts were studied. Patients had undergone end to side saphenous vein bypass grafting 1 to 13 (mean 7) years previously. All patients presented with new or worsening angina pectoris with ST-T changes or non-Q wave acute myocardial infarction and all had a totally occluded saphenous vein bypass graft. The new technique entailed the positioning of an angiographic catheter into the stub of the occluded graft and the advancement of an infusion wire into the graft. Patients were returned to the coronary care unit, where urokinase was delivered at a dose of 100,000 to 250,000 U/h. The total dose of urokinase ranged from 0.7 to 9.8 million U over 7.5 to 77 h (mean 31). After therapy, recanalization was seen in 37 (79%) of the 47 grafts. In 20 successfully treated patients, angiography was performed 1 to 24 (mean 11) months after treatment; 13 (65%) of these grafts were patent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1991

Stimulation by endozepine of the side-chain cleavage of cholesterol in a reconstituted enzyme system.

Addition of endozepine in nanomolar concentrations to a system for side-chain cleavage reconstituted from highly purified P-450scc and electron carriers (adrenodoxin reductase and adrenodoxin) stimulates the conversion of cholesterol to pregnenolone (side-chain cleavage). This response is concentration and time-dependent and specific to the extent that a second steroidogenic P-450 located in the inner mitochondrial membrane (ie 11 beta-hydroxylase) was not stimulated by endozepine. Homogeneous endozepine prepared from bovine brain, the corresponding genetically engineered peptide and des(glu-ilu)-endozepine isolated from bovine adrenal cortex are all approximately equipotent in this system. Moreover, endozepine accelerates the rate of reduction of P-450scc by NADPH and the electron carriers. The results suggest that endozepine acts directly on P-450 and hence the rate of side-chain cleavage.

Adrenal Cortex↗

PubMed1991

The effect of predilatation on coronary angioplasty-induced vessel wall injury.

Fifty-four patients presenting with stenotic lesions in a major coronary artery visually estimated by diagnostic angiography to be greater than 90% but less than 100% were randomized to one of two angioplasty regimens, predilatation (group 1) or no predilatation (group 2). In group 1, the artery was initially dilated with a 2 mm balloon followed by a balloon that was considered by the operator to be the definitive size to fully dilate the target vessel. In group 2, the artery was dilated with a balloon deemed the definitive size to complete the angioplasty procedure. There were no statistical differences between groups with respect to age, sex, history of unstable angina, or prior acute myocardial infarction. There were also no significant differences in the angiographic characteristics of the coronary lesions including artery location, lesion length, concentric or eccentric morphology, tubular versus discrete stenosis, calcium in lesions, or lesions on a bend. Following angioplasty, luminal filling defects were present in 5% of the predilated group and in 9% of the nonpredilated group (p = NS). The incidence of luminal border haziness at the dilatation site did not differ between groups, seven (35%) in group 1 versus eight (24%) in group 2. Angiographic evidence of a linear dissection at the angioplasty site was also similar between groups, one (5%) in group 1 versus five (15%) in group 2. Occlusive complications were witnessed in 10% of the predilated group and 12% of the nonpredilated group (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗

PubMed1991

Transfer of processing in repetition priming: some inappropriate findings.

Transfer effects in repetition priming were found with both picture and word naming, but varied with the type of prime list. Unmixed lists of word or picture primes produced equivalent intra-modal and cross-modal repetition priming in both picture-naming (Experiment 1) and word-naming (Experiment 5) tasks. However, mixing word and picture primes resulted in greater intra-modal than cross-modal priming for both picture-naming (Experiment 2) and word-naming (Experiment 6) tasks. This mixed-list difference between intra-modal and cross-modal priming was reduced by blocking prime types at input (Experiment 3). These findings suggest that differences in priming as a function of prime stimulus format should be cautiously interpreted when mixed prime lists are used.

Adult↗

PubMed1991

A review of the tip-of-the-tongue experience.

The tip-of-the-tongue experience (TOT) has intrigued psychologists for nearly a century. R. Brown and McNeil (1966) provided the first systematic exploration of the phenomenon, and the findings since their seminal study suggest that TOTs (a) are a nearly universal experience, (b) occur about once a week, (c) increase with age, (d) are frequently elicited by proper names, (e) often enable access to the target word's first letter, (f) are often accompanied by words related to the target, and (g) are resolved during the experience about half of the time. Important questions remain concerning TOTs: (a) Are emotional reactions necessary, (b) do only low frequency targets elicit TOTs, (c) do TOTs reflect incomplete target word activation or interference from related words, and (d) do spontaneous retrievals really occur? A more precise definition of the TOT experience is needed, as well as greater uniformity in the information gathered during TOTs.

Adult↗

PubMed1991

Age differences in retrieval consistency and response dominance.

The probability of generating dominant responses and producing the same response on two occasions was compared for older and younger adults over three different intervals. Continuous retrieval from broadly defined semantic and orthographic categories was examined in Experiment 1; single-word retrieval from restricted categories was tested in Experiment 2 using a picture-naming task. There was no age difference in the tendency to generate normatively dominant responses in either experiment, but there were age differences in consistency. For broad categories, older were less consistent than younger adults at each intersession interval. With restricted categories, older adults showed a systematic decline in consistency over increasing intersession interval, while younger adults showed no change. Unlike prior research, we failed to find evidence for a positive relationship between verbal ability and response dominance.

Adolescent↗

PubMed1990

Calcium-calmodulin-dependent phosphorylation of cytoskeletal proteins from adrenal cells.

We have identified a highly active Ca2+ calmodulin-dependent protein kinase in the cytoskeletons of normal (bovine fasciculata) and transformed (Y-1 mouse tumor) adrenal cells. In view of evidence for the involvement of calmodulin and microfilaments in the regulation of cholesterol transport and hence steroidogenesis, it is likely that this kinase is important in this process. The kinase activity was examined for its capacity to phosphorylate endogenous proteins analyzed by one- and two-dimensional gel electrophoresis, in the presence of saturating amounts of Ca2+ (5 mM) and calmodulin (5 microM). Three inhibitors of calmodulin (trifluoperazine, pimozide and W-7) inhibit steroidogenesis and Ca2(+)-calmodulin-dependent phosphorylation kinase activity with similar values for EC50 for the two processes. All three inhibitors inhibit the increased transport of cholesterol to mitochondria in response to ACTH. Two substrates for the kinase (alpha-spectrin and beta-tubulin) were identified and two others (51,000 and 60,000 molecular weight) were tentatively identified as the subunits of the kinase itself in cytoskeletons of both cell types. Calmodulin-binding proteins analyzed by [125I]iodocalmodulin overlay and calmodulin-Sepharose affinity chromatography were also identified in the same cytoskeletons including alpha-spectrin, the Ca2+ calmodulin-dependent phosphatase calcineurin and three that were tentatively identified as the two subunits of the kinase itself and myosin light chain kinase. It is concluded that calmodulin, by binding to the kinase and phosphatase, is capable of influencing the degree of phosphorylation of specific substrates in the cytoskeleton and of forming complexes with spectrin, actin and tubulin. These events may be involved in the regulation of the rate-limiting step of steroidogenesis, i.e. transport of cholesterol to mitochondria.

Adrenal Gland Neoplasms↗

PubMed1990

Dissociations between procedural and episodic memory: effects of time and aging.

The issue of multiple memory systems is explored. Young and older adults (mean ages = 20 and 71, respectively) named pictures and were tested immediately, 1, 7, or 21 days later. Episodic memory (recognition) for pictures was significantly lower in older relative to young adults and declined systematically across all retention intervals in both age groups. In contrast, procedural memory (repetition priming in picture naming) revealed no reliable age differences. In both age groups, priming declined within the first 24 hr, but unlike recognition, there was no further decrement from 1 to 21 days. There were also within-subject dissociations: The magnitude of priming was equivalent for remembered and forgotten items, and the relation between recognition and priming across intervals was nonmonotic, revealing a reversed association. The findings were interpreted within a multiple-memory-systems framework.

Adult↗

PubMed1990