A ROENTGENOGRAPHIC STUDY OF FACIAL MORPHOLOGY IN A TRIBE OF CENTRAL AUSTRALIAN ABORIGINES.
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Australia↗
Biomedical subjects
T Brown
Publications and source records attributed to T Brown.
TOOTH ERUPTION SEQUENCE IN A TRIBE OF CENTRAL AUSTRALIAN ABORIGINES.
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Australia↗
Psychologic factors in low-back pain.
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Back Pain↗
Genetic amniocentesis in multiple gestations.
Thirty-one genetic amniocenteses involving multiple gestations were performed in the genetics unit between 1976 and 1982. Three sets of triplets were included. Precise locations of the sacs were determined using real-time ultrasonography and successful sampling of all sacs was accomplished. Spontaneous abortions occurred in two normal twins and one normal triplet gestation. Two therapeutic abortions were performed for fetal abnormalities. Two cases of discordance for trisomy 21 (one twin and one triplet) were allowed to continue; the twin case terminated at 25 weeks' gestation with neonatal deaths and the triplets are alive and well.
Amniocentesis↗
Correlation between liver iron content and magnetic resonance imaging in rats.
Currently, serum ferritin concentration is the best noninvasive estimator of liver iron content. This study investigated the ability of magnetic resonance imaging to determine hepatic iron concentration. Fisher rats were treated with either parenteral iron to increase levels of phlebotomy to lower them and achieved a wide range of liver iron concentrations. Rats were imaged using a clinical whole body scanner at 1.5 Tesla with a 15-cm Helmholtz surface coil and a 23-cm field of view. The ratio of signal intensity of liver to skeletal muscle from images of the live intact rats correlated well with chemically measured iron concentration of the liver (r = -.89, p less than .0001, linear regression analysis). Transverse relaxation rates (1/calculated T2 relaxation times) also correlated with liver iron content (r = .66, p less than .0001). The observation of a significant correlation between liver iron content and both signal intensities and T2 relaxation rates, obtained by magnetic resonance imaging, may have considerable clinical relevance. If adapted to humans, this technique would have obvious applications in the diagnosis and management of diseases associated with iron overload as well as in the investigation of the overall role of iron in various human liver diseases.
Animals↗
Chevron bunionectomy with microplate and screw fixation: a retrospective follow-up of 26 feet.
The authors report the results of 21 patients (26 feet) who had Chevron osteotomy of the first metatarsal head to correct hallux valgus. Fixation was achieved by using a small plating system consisting of one L-plate (8.5 mm x 17 mm x 0.8 mm) and four screws (1.6 mm). Results showed no capital fragment displacement, avascular necrosis, or plate deformation. One case of screw loosening was noted on x-rays. This patient noted occasional irritation over the plate while wearing shoes. Symptoms did not cause the patient to seek removal of the plate and screws. The small plate system allows the surgeon to perform the osteotomy as originally described by Austin, with the added security of rigid internal fixation.
Adult↗
Implementation of a case coordinator role: a focused ethnographic study.
This study was a focused ethnography of a 21-bed, inpatient psychiatric unit. Patient care was provided by a multidisciplinary team, and a case coordinator role was developed to coordinate the team's efforts. The purpose of the study was to describe perceptions of the implementation of the case coordinator role. Data collection methods included document review, participant and nonparticipant observation, and personal interviews of key informants. Field notes and transcriptions were analyzed throughout data collection. Three themes were identified: role development, role confusion, and role expectation. Role development was defined as the process of recognizing the need for and instituting the position of case coordinator. Role confusion was defined as the lack of a clear distinction between the role of the case coordinator and the role of the staff nurse. Role expectation was defined as the process of directing the development of the role based on individuals' perceptions of the role. Although the role as implemented had not met initial expectations, team members were confident the role would evolve to fulfill the unit's needs.
Anthropology, Cultural↗
High-resolution structure of a DNA helix containing mismatched base pairs.
The concept of complementary base pairing, integral to the double-helical structure of DNA, provides an effective and elegant mechanism for the faithful transmission of genetic information. Implicit in this model, however, is the potential for incorporating non-complementary base pairs (mismatches) during replication or subsequently, for example, during genetic recombination. As such errors are usually damaging to the organism, they are generally detected and repaired. Occasionally, however, the propagation of erroneous copies of the genome confers a selective advantage, leading to genetic variation and evolutionary change. An understanding of the nature of base-pair mismatches at a molecular level, and the effect of incorporation of such errors on the secondary structure of DNA is thus of fundamental importance. We now report the first single-crystal X-ray analysis of a DNA fragment, d(GGGGCTCC), which contains two non-complementary G X T base pairs, and discuss the implications of the results for the in vivo recognition of base-pair mismatches.
Base Composition↗
Structure of an adenine-cytosine base pair in DNA and its implications for mismatch repair.
Mutational pathways rely on introducing changes in the DNA double helix. This may be achieved by the incorporation of a noncomplementary base on replication or during genetic recombination, leading to substitution mutation. In vivo studies have shown that most combinations of base-pair mismatches can be accommodated in the DNA double helix, albeit with varying efficiencies. Fidelity of replication requires the recognition and excision of mismatched bases by proofreading enzymes and post-replicative mismatch repair systems. Rates of excision vary with the type of mismatch and there is some evidence that these are influenced by the nature of the neighbouring sequences. However, there is little experimental information about the molecular structure of mismatches and their effect on the DNA double helix. We have recently determined the crystal structures of several DNA fragments with guanine X thymine and adenine X guanine mismatches in a full turn of a B-DNA helix and now report the nature of the base pairing between adenine and cytosine in an isomorphous fragment. The base pair found in the present study is novel and we believe has not previously been demonstrated. Our results suggest that the enzymatic recognition of mismatches is likely to occur at the level of the base pairs and that the efficiency of repair can be correlated with structural features.
Adenine↗
The crystal structure of d(GGATGGGAG): an essential part of the binding site for transcription factor IIIA.
Most genes in higher organisms are activated by the binding of proteins called transcription factors. One such protein, transcription factor IIIA (TFIIIA) from the frog, activates the gene for 5S RNA by binding to the region of the gene between nucleotides 45 and 97. This binding site has been defined by a variety of biochemical studies, including base-deletion experiments and DNase I footprinting. The protein also binds to the gene product: in immature frogs it is stored as a complex with 5S RNA. From the observation that TFIIIA can bind to either double-helical DNA or RNA, and from their own measurements, Rhodes and Klug have proposed that the DNA-binding site for TFIIIA has an RNA-like structure. Here we present the crystal structure analysis of a part of the DNA-binding site (nucleotides 81-89 of the gene) which forms a particularly strong interaction with the protein, and show that it has a conformation similar to the A' form of double-helical RNA.
Base Sequence↗
Adolescent growth in height of Australian aboriginals analysed by the Preece-Baines function: a longitudinal study.
Adolescent growth in height was studied in 62 Australian Aboriginal children enrolled in a longitudinal study at Yuendumu in the Northern Territory of Australia. A direct-search method for minimization of the Preece-Baines Model 1 function was used to estimate mean constants and biological parameters describing the adolescent growth. There were few differences between Aboriginal and British children in the ages at take-off (TO) and peak height velocity (PHV), in adolescent gain or in the percentages of adult height achieved at TO and PHV. Aboriginal boys, however, were shorter than British boys at TO, PHV and adulthood. PHVs in the Aboriginals, 10.3 cm/yr in boys and 8.4 cm/yr in girls, were higher than in British children. In the light of known levels of infant mortality and morbidity at Yuendumu between 1953 and 1970, it is suggested that the high PHVs may be indicative of 'catch-up' growth following early childhood retardation.
Adolescent↗
The Preece-Baines growth function demonstrated by personal computer: a teaching and research aid.
A group of programs was designed for execution on a personal computer to demonstrate the features of the Preece-Baines model applied to growth in height. Mean constant distance and velocity curves of four populations can be compared graphically or new curves fitted to data entered by keyboard or retrieved from diskette files. Biological parameters describing growth events are derived from the function coefficients.
Adolescent↗
Size and shape of mandibular first molars in Down syndrome.
The size and shape characteristics of permanent mandibular first molars were compared in a group of young males with Down syndrome (DS) and a control group of normal males. Generalized size was quantified by the log transforms of five intercusp distances and shape by a principal component analysis of the log distances scaled to constant size. On average the DS molars were smaller than the controls by 8%, the most marked reduction being in the distance between the distal and distolingual cusps. The scores on two of the four components of shape also differed between the DS and control teeth. These two shape components, which accounted for over 41% of the total shape variation, were determined specially by the occlusal morphology of the distal crown region. Discriminant function analyses also indicated the importance of the distal regions in discriminating between control and DS molars. Evidence suggests that trisomy 21 is associated with a general retardation in growth. The observed features of DS molars were consistent with decreased cellular activity in the developing tooth germs, producing morphological changes that were more pronounced in the later-forming crown regions.
Adult↗
The mechanism of DNA repair by uracil-DNA glycosylase: studies using nucleotide analogues.
2',4'-Dideoxy-4'-methyleneuridine incorporated into oligodeoxynucleotides forms regular B-DNA duplexes as shown by Tm and CD measurements. Such oligomers are not cleaved by the DNA repair enzyme, UDG, which cleaves the glycosylic bond in dU but not in dT nor in dC nucleosides in single stranded and double stranded DNA. Differential binding of oligomers containing carbadU, 4'-thiodU, and dU residues to wild type and mutant UDG proteins identify an essential role for the furanose 4'-oxygen in recognition and cleavage of dU residues in DNA.
Base Sequence↗
Calcified synovial cyst of the cervical spine: CT and MR evaluation.
A case of calcified synovial cyst of the cervical spine was diagnosed by a combination of imaging modalities. Curvilinear calcification associated with posterior elements, well seen by CT, suggested the correct diagnosis. Magnetic resonance showed a curvilinear region of low signal intensity corresponding to the calcification.
Calcinosis↗
Should there be laws mandating domestic violence reporting?
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Adult↗
The major components of human energy balance during chronic beta-adrenergic blockade.
PURPOSE: The authors compare the major components of energy balance--dietary food intake, resting metabolic rate, and physical energy expenditure--in patients receiving beta-blocking medications and healthy controls. METHODS: The authors recruited subjects who were receiving beta-blocking agents (n = 22) from local hospitals and clinics. Twenty-two healthy controls were matched to each patient based on age, weight, and gender. Resting metabolic rates were determined using indirect calorimetry. Three-day dietary intakes and physical activity assessments were analyzed. RESULTS: There were no between-group differences in calories ingested or self-reported physical activity patterns. However, resting metabolic rates were lower in the beta-blocked subjects (beta-blocked = 1,541 +/- 464 kcals/day; controls = 1,817 +/- 426 kcals/day; P < 0.05). CONCLUSIONS: beta-adrenergic blockade causes a reduction in resting metabolic rate. Therefore, beta-blocked individuals should increase physical activity, decrease dietary intake, or both to maintain daily energy balance and prevent weight gain that accompanies a reduction in metabolic rate.
Adrenergic beta-Antagonists↗
Rate-responsive pacing improves exercise tolerance in heart transplant recipients: a pilot study.
BACKGROUND: Chronotropic incompetence is one cause of diminished exercise capacity in heart transplant recipients. If reinnervation occurs, it often is late after transplantation and is not always accompanied by functional improvements in peak heart rate and appropriate tachycardia during exercise. To determine the efficacy of rate-responsive pacing on peak heart rate and exercise capacity, the authors studied eight male heart transplant recipients (age 57 +/- 12 years; 23 +/- 9 months after transplantation) that had either atrial or dual-chambered pacemakers. METHODS: All subjects completed two maximal graded exercise tests (GXT) using the Naughton treadmill protocol. During the first GXT, pacemakers were programmed for bradycardia support only and without rate responsiveness (unpaced). After a 14-day regimen of beta blockade with metoprolol to nullify the influence of circulating catecholamines on heart rate, subjects performed the second GXT with pacemakers programmed to respond optimally in the rate-responsive mode (paced). RESULTS: Peak heart rate (149 versus 129 bpm), peak oxygen uptake (18.9 versus 15.4 mL/kg/min), treadmill time to exhaustion (14.6 versus 12.4 min), and minute ventilation (76.7 versus 66.2 L/min) were significantly increased (P < or = 0.05) during the paced versus unpaced GXT. CONCLUSIONS: The results of this study demonstrate that chronotropic support of the transplanted heart using a rate-responsive pacemaker, with activity-based sensors programmed for maximal sensitivity, improves both peak heart rate and exercise capacity in heart transplant recipients significantly more than circulating catecholamines alone.
Adrenergic beta-Antagonists↗