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Biomedical subjects

K I Norton

Publications and source records attributed to K I Norton.

At least 19 recordsLinked to original sources
PubMed1999

The evolution of Australian football.

Australian football has undergone considerable change over the past century. This evolution seems to have accelerated more recently since the introduction and major influence of the media, increased professionalism and the start of a national competition. In this study we have attempted to quantify the evolution in game 'style' by measuring events during elite football games (from video analysis) and gathering physical information on players involved at the highest level. These data are important to gain insight into the game demands so that player preparation may be enhanced and when predicting the nature of the game in the future. Understanding the patterns of play within the game may also be useful when assessing the possible impact of rule changes, for example, increasing the number of interchange players on the potential for injury. Four games were selected, one from each of the past 4 decades to determine the rate at which specific, measurable events occurred in the games. Height and mass data on players were also obtained from official records of registered players in the VFL/AFL competitions. The results indicate the 'speed' of the game has approximately doubled in the period 1961-1997. The proportion of the total game which involves 'play' time has been reduced significantly while breaks in play are more frequent and longer. Despite this pattern, however, the average game tempo has increased along with player height and mass and we present a case which suggests these are likely determinants of the increased incidence of player injuries and lost match time.

Athletic Injuries↗
PubMed1999

Diaphyseal medullary stenosis with malignant fibrous histiocytoma: a hereditary bone dysplasia/cancer syndrome maps to 9p21-22.

Diaphyseal medullary stenosis with malignant fibrous histiocytoma (DMS-MFH) is an autosomal dominant bone dysplasia/cancer syndrome of unknown etiology. This rare hereditary cancer syndrome is characterized by bone infarctions, cortical growth abnormalities, pathological fractures, and eventual painful debilitation. Notably, 35% of individuals with DMS develop MFH, a highly malignant bone sarcoma. A genome scan for the DMS-MFH gene locus in three unrelated families with DMS-MFH linked the syndrome to a region of approximately 3 cM on chromosome 9p21-22, with a maximal two-point LOD score of 5.49 (marker D9S171 at recombination fraction [theta].05). Interestingly, this region had previously been shown to be the site of chromosomal abnormalities in several other malignancies and contains a number of genes whose protein products are involved in growth regulation. Identification of this rare familial sarcoma-causing gene would be expected to simultaneously define the cause of the more common nonfamilial, or sporadic, form of MFH-a tumor that constitutes approximately 6% of all bone cancers and is the most frequently occurring adult soft-tissue sarcoma.

Bone Diseases, Developmental↗
PubMed1999

MR cholangiography in children and young adults with biliary disease.

OBJECTIVE: Our objective was to describe the MR cholangiography findings for young patients with suspected biliary disease who underwent half-Fourier acquisition fast spin-echo technique with respiratory triggering. SUBJECTS AND METHODS: Twenty-eight MR cholangiography studies were performed in 22 patients on a 1.5-T MR unit. Ten of these 22 patients had undergone liver transplantation. RESULTS: MR cholangiography revealed abnormalities of both the extrahepatic and the intrahepatic major and minor bile duct systems, despite the small diameter of the duct system in this group of patients. Four patterns of biliary disease were shown: global dilatation of extrahepatic or intrahepatic ducts (n = 7); segmental, uniform dilatation of central or peripheral intrahepatic ducts (n = 9); segmental, nonuniform dilatation of central or peripheral intrahepatic ducts (n = 2); and fusiform ectasia with segmental, irregular intrahepatic dilatation and bile lakes (n = 2). The findings of eight studies were interpreted as normal. The four patterns of abnormalities were correlated with the results from percutaneous transhepatic cholangiography, T-tube cholangiography, and liver biopsy and with clinical and surgical information, as available. CONCLUSION: MR cholangiography is a noninvasive technique for evaluation of biliary disease. The improved resolution afforded by respiratory triggering permits evaluation of both major and minor bile ducts, even in young, uncooperative subjects. Four patterns of abnormalities were prospectively identified, correlated with other information, and used to direct clinical treatment.

Adolescent↗
PubMed1997

Leiomyosarcoma of the kidney in an HIV-infected child.

Spindle cell tumors (leiomyoma and leiomyosarcoma) have been described in immunocompromised children after transplantation and in association with HIV infection. Previous reports have described tumors of respiratory (lung, bronchi), gastrointestinal (stomach, bowel, liver), and subcutaneous origins. We report a case of leiomyosarcoma of the kidney in an HIV-infected child.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Chest radiographic data acquisition and quality assurance in multicenter studies.

BACKGROUND: Multicenter studies rely on data derived from different institutions. Forms can be designed to standardize the reporting process allowing reliable comparison of data. OBJECTIVE: The purpose of the report is to provide a standardized method, developed as a part of a multicenter study of vertically transmitted HIV, for assessing chest radiographic results. MATERIALS AND METHODS: Eight hundred and five infants and children were studied at five centers; 3057 chest radiographs were scored. Data were entered using a forced-choice, graded response for 12 findings. Quality assurance measures and inter-rater agreement statistics are reported. RESULTS: The form used for reporting chest radiographic results is presented. Inter-rater agreement was moderate to high for most findings, with the best correlation reported for the presence of bronchovascular markings and/or reticular densities addressed as a composite question (kappa = 0.71). The presence of nodular densities (kappa = 0.56) and parenchymal consolidation (kappa = 0.57) had moderate agreement. Agreement for lung volume was low. CONCLUSION: The current tool, developed for use in the pediatric population, is applicable to any study involving the assessment of pediatric chest radiographs for a large population, whether at one or many centers.

Child↗
PubMed1997

Reduced performance of male and female athletes at 580 m altitude.

This study examined the effect of mild hypobaria (MH) on the peak oxygen consumption (VO2peak) and performance of ten trained male athletes [x (SEM); VO2peak = 72.4 (2.2) ml x kg(-1) x min(-1)] and ten trained female athletes [VO2peak = 60.8 (2.1) ml x kg(-1) x min(-1)]. Subjects performed 5-min maximal work tests on a cycle ergometer within a hypobaric chamber at both normobaria (N, 99.33 kPa) and at MH (92.66 kPa), using a counter-balanced design. MH was equivalent to 580 m altitude. VO2peak at MH decreased significantly compared with N in both men [-5.9 (0.9)%] and women [-3.7 (1.0)%]. Performance (total kJ) at MH was also reduced significantly in men [-3.6 (0.8)%] and women [-3.8 (1.2)%]. Arterial oxyhaemoglobin saturation (SaO2) at VO2peak was significantly lower at MH compared with N in both men [90.1 (0.6)% versus 92.0 (0.6)%] and women [89.7 (3.1)% versus 92.1 (3.0)%]. While SaO2 at VO2peak was not different between men and women, it was concluded that relative, rather than absolute. VO2peak may be a more appropriate predictor of exercise-induced hypoxaemia. For men and women, it was calculated that 67-76% of the decrease in VO2peak could be accounted for by a decrease in O2 delivery, which indicates that reduced O2 tension at mild altitude (580 m) leads to impairment of exercise performance in a maximal work bout lasting approximately 5 min.

Adult↗
PubMed1997

Subcutaneous fat necrosis of the newborn: CT findings of head and neck involvement.

We present the CT findings in two newborns with subcutaneous fat necrosis. This is an uncommon disease that occurs in neonates who have had difficult deliveries. The CT findings varied from discrete subcutaneous nodules to a diffuse subcutaneous fullness. Although the subcutaneous disease tends to spontaneously resolve within weeks to months, an associated hypercalcemia may have a fatal outcome.

Cheek↗
PubMed1997

Accuracy of two pulse oximeters during maximal cycling exercise.

This study compared the measurement of oxygen saturation of haemoglobin (SaO2) by two pulse oximeters (Ohmeda Biox 3700e and Criticare 504 USP) with the measurement of SaO2 in arterial blood samples by CO-oximetry. Unlike many previous validation studies, arterial blood was sampled in ground glass rather than plastic syringes. Twenty men, 11 well-trained cyclists (mean +/- SE, age = 23.3 +/- 1.5 years, mass = 71.4 +/- 1.1 kg VO2max = 77 +/- 1 ml.kg1.min-1) and 9 relatively untrained subjects (age = 27.1 +/- 2.8 years, mass = 78.1 +/- 2.2 kg VO2max = 51 +/- 3 ml.kg 1.min-1) performed two maximal cycle ergometer tests each in an hypobaric chamber. The tests were at 745 mm Hg or 695 mm Hg with simultaneous measurement of SaO2 by the pulse oximeters and the CO-oximeter at rest, minute 7 of exercise and at VO2max. The best correlations, to the Co-oximeter measurement (SCO-OXO2) were found when all data from rest and exercise were combined (Criticare: r = 0.94; Ohmeda: r = 0.91). The bias measurements showed the Ohmeda underestimated SCO-OXO2 at all levels (mean = -2.5 +/- 1.9%) and the Criticare overestimated SCO-OXO2 at all levels, although to a lesser degree (mean = 0.9 +/- 1.5%). In conclusion, these results highlight the need for validation of individual pulse oximeters and that the effect of dyshaemoglobins must also be considered.

Adult↗
PubMed1996

Diaphyseal medullary stenosis (sclerosis) with bone malignancy (malignant fibrous histiocytoma): Hardcastle syndrome.

Hardcastle syndrome is a rare, autosomally dominant inherited skeletal dysplasia, characterized by diaphyseal sclerosis, medullary stenosis, pathological fractures, bony infarction, and malignant transformation. A 19-year-old proband is presented and discussed, adding a fourth family to the world literature. Radiographic screening of family members is suggested from puberty onward. Thallium scanning is proposed as a more tumor-sensitive screening agent in affected individuals.

Adult↗
PubMed1996

Regression of skeletal changes in type 1 Gaucher disease with enzyme replacement therapy.

A 9-year-old patient presented with an acute onset of pain of the right femur showing destructive changes with periosteal elevation mimicking osteomyelitis. Technetium-99m sulfur colloid (99mTc SC) marrow scan revealed lack of uptake in the right femoral head and the entire shaft of the right femur. Eight months following enzyme replacement therapy, radiography showed almost complete reconstitution of the femoral shaft, and 99mTc SC marrow scan uptake returned to normal.

Bone Marrow↗
PubMed1996

Increased arterial desaturation in trained cyclists during maximal exercise at 580 m altitude.

This study utilized a hypobaric chamber to compare the effects of mild hypobaria (MH; 50 mmHg, approximately 580 m altitude) on blood O2 status and maximal O2 consumption (VO2max) in 9 untrained and 11 trained (T) cyclists with VO2max values of 51 +/- 3 and 77 +/- 1 ml.kg-1.min-1, respectively. In both groups, arterial O2 saturation (SaO2) decreased significantly during maximal exercise, and this effect was enhanced with MH. Both these responses were significantly greater in the T cyclists in whom the final SaO2 during MH was 86.5 +/- 0.9%. When the group data were combined, approximately 65% of the variance in SaO2 could be attributed to a widened alveolar-arterial Po2 difference. The arterial PO2 during maximal exercise at sea level in the T group was on the steeper portion of the hemoglobin-O2-loading curve (T, 68.3 +/- 1.3 Torr; untrained, 89.0 +/- 2.9 Torr) such that a similar decrease in arterial PO2 in the two groups in response to MH resulted in a significantly greater fall in both SaO2 and calculated O2 content in the T group. As a consequence, the VO2max fell significantly only in the T group (mean change, -6.8 +/- 1.5%; range, + 1.2 to - 12.3%), with approximately 70% of this decrease being due to a fall in O2 content. This is the lowest altitude reported to decrease VO2max, suggesting that T athletes are more susceptible to a fall in inspired PO2.

Adult↗
PubMed1995

Exercise stimulus increases ventilation from maximal to supramaximal intensity.

This study investigated the influence of an exercise stimulus on pulmonary ventilation (VE) during severe levels of exercise in a group of ten athletes. The altered ventilation was assessed in relation to its effect on blood gas status, in particular to the incidence and severity of exercise induced hypoxaemia. Direct measurements of arterial blood were made at rest and during the last 15 s of two intense periods of cycling; once at an intensity found to elicit maximal oxygen uptake (VO2max; MAX) and once at an intensity established to require 115% of VO2max (SMAX). Oxygen uptake (VO2) and ventilatory markers were continually recorded during the exercise and respiratory flow-volume loops were measured at rest and during the final 30 s of each minute for both exercise intensities. When compared to MAX exercise, the subjects had higher ventilation and partial pressure of arterial oxygen (PaO2) during the SMAX intensity. Regression analysis for both conditions indicated the levels of PaO2 and oxygen saturation of arterial blood (SaO2) were positively correlated with relative levels of ventilation during exercise. It was apparent that mechanical constraints to ventilate further were not present during the MAX test since the subjects were able to elevate VE during SMAX and attenuate the level of hypoxaemia. This was also confirmed by analysis of the flow volume recordings. These data support the conclusions firstly, that overwhelming mechanical constraints on VE were not present during the MAX exercise, secondly, the subjects exhibiting the most severe hypoxaemia had no consistent relationship with any measure of expiratory flow limitation, and thirdly, ventilatory patterns during intense exercise are strong predictors of blood gas status.

Adolescent↗
PubMed1995

The effects of altered exercise distribution on lymphocyte subpopulations.

The effects of exercise distribution on lymphocyte count, lymphocyte subpopulations and plasma cortisol concentration in peripheral blood were assessed in 19 healthy subjects. The subjects were randomly divided into group A (n = 10) or group B (n = 9) according to exercise distribution. Both groups underwent a 10-week programme involving 5 x 2-week blocks: baseline (B), training period 1 (TP1), stabilisation 1 (S1), training period 2 (TP2), and stabilisation 2 (S2). During B, S1 and S2 normal training was undertaken. During TP1 and TP2 the subjects increased the amount of training by 50% in week 1 and by 100% in week 2. During TP1 subjects in group A exercised 6 days.week-1, while during TP2 these subjects exercised on 3 alternate days.week-1, but doubled the duration of each training session. The subjects in group B reversed this training order. Blood was collected 36-42 h following exercise period B, and at the end of periods TP1, S1, TP2 and S2, and also 12-18 h following completion of exercise at the end of TP1 and TP2. There were no significant differences (P > 0.05) between the 6 day.week-1 programme and the 3 alternate day.week-1 programme in total lymphocyte count, CD3+, CD4+, CD8+, CD16+, or CD19+ cells, the CD4:CD8 ratio, HLA-DR+ (activated) T cells or plasma cortisol concentrations. Following both TP1 and TP2 there was a nonsignificant decrease in lymphocyte subpopulations. However following both S1 and S2 (baseline training) there was a significant increase in total lymphocyte count, CD3+, CD4+ and CD8+ lymphocytes. The S2 variables statistically significant from B were: total lymphocyte count (P < 0.01), CD3+ T-cells and percentage of circulating lymphocytes (P < 0.01), CD4+ cells (P < or = 0.0001), CD8+ cells (P < 0.05), and HLA-DR+ (activated) T-cells (P < 0.05). The results indicated that provided the amount of exercise is constant for a given period, then exercise distribution is not a critical variable in the alteration of lymphocyte subpopulations that may occur in response to overload training. However 2 weeks of overload training followed by 2 weeks of active recovery (baseline) training may induce an increase in the lymphocyte count.

Adult↗
PubMed1995

Influence of test duration and event specificity on maximal accumulated oxygen deficit of high performance track cyclists.

This study examined the relationship between the time required to fully utilise the maximal accumulated oxygen deficit (MAOD) and event specificity of track cyclists. Twelve track endurance and 6 sprint high performance track cyclists performed four treatments of 70 s, 120 s, 300 s and 115% VO2max of maximal cycling on an air-braked ergometer. Peak blood lactate was measured immediately after each test with VO2 kinetics being assessed during the 115% VO2max time to exhaustion test. When the two cycling groups were combined there was no significant difference in the MAOD when assessed under the four different exercise durations. However, when the groups were analysed separately the following results were apparent: (1) the sprint cyclists achieved a significantly greater MAOD (66.9 +/- 2.2 ml.kg-1) compared to the track endurance cyclists (57.6 +/- 6.7 ml.kg-1) when a 70 s test duration was employed (2) even though the track endurance cyclists achieved their greatest MAOD during the 300 s test protocol (62.1 +/- 11.0 ml.kg-1), it was not significantly different to the MAOD's measured during the three other test durations and (3) the sprint cyclists recorded their greatest MAOD during the 70 s supramaximal test protocol (66.9 +/- 2.2 ml.kg-1). This was not significantly different to the 120 s test MAOD, but it was significantly higher than the MAOD values recorded during the 115% VO2max and 300 s test durations. There was no significant difference between the two groups in the peak post-exercise blood lactate concentrations for any of the tests and only the 70 s test produced a significant correlation between peak blood lactate and the MAOD. The VO2 kinetics (VO2 t1/2) of the sprinters was significantly slower than that of the track endurance cyclists (26.3 +/- 2.3 vs 23.9 +/- 2.8 s.). The findings of this study demonstrate that sprint cyclists can fully express their anaerobic capacity within an event specific 70 s all-out test and that these cyclists progressively decrease their anaerobic capacity during a 120 s, 115% VO2max (mean time = 210 s) or 300 s test, despite giving all-out efforts. Conversely, track endurance cyclists achieve their highest mean score during an event specific 300 s test and their lowest during a 70 s test. These findings have important implications when testing high performance cyclists for determination of MAOD, with the implication that it is necessary to assess MAOD under exercise conditions (i.e., duration, pacing) specific to the cyclist's chosen event.

Adolescent↗
PubMed1995

Modeling road-cycling performance.

This paper presents a complete set of equations for a "first principles" mathematical model of road-cycling performance, including corrections for the effect of winds, tire pressure and wheel radius, altitude, relative humidity, rotational kinetic energy, drafting, and changed drag. The relevant physiological, biophysical, and environmental variables were measured in 41 experienced cyclists completing a 26-km road time trial. The correlation between actual and predicted times was 0.89 (P < or = 0.0001), with a mean difference of 0.74 min (1.73% of mean performance time) and a mean absolute difference of 1.65 min (3.87%). Multiple simulations were performed where model inputs were randomly varied using a normal distribution about the measured values with a SD equivalent to the estimated day-to-day variability or technical error of measurement in each of the inputs. This analysis yielded 95% confidence limits for the predicted times. The model suggests that the main physiological factors contributing to road-cycling performance are maximal O2 consumption, fractional utilization of maximal O2 consumption, mechanical efficiency, and projected frontal area. The model is then applied to some practical problems in road cycling: the effect of drafting, the advantage of using smaller front wheels, the effects of added mass, the importance of rotational kinetic energy, the effect of changes in drag due to changes in bicycle configuration, the normalization of performances under different conditions, and the limits of human performance.

Adolescent↗
PubMed1994

Inflammatory pseudotumor of the maxillary sinus in a 15-year-old boy.

Inflammatory pseudotumor is a benign neoplasm composed of fibroblasts, histiocytes, and inflammatory cells. Its occurrence in the paranasal sinuses is rare. We report a case of a 15-year-old boy with a maxillary sinus inflammatory pseudotumor that simulated an aggressive neoplasm on CT scan.

Adolescent↗