Biomedical subjects
Publications and source records attributed to T C Brown.
Aneurysms of the inferior gluteal artery are uncommon, and have not previously been described in detail in the radiologic literature. The authors report the findings of computed tomography and angiography for a patient with a pseudoaneurysm of the inferior gluteal artery who was successfully treated by embolization alone.
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A double-blind study consisting of 339 randomly selected children investigated the effects of several premedicants on the preoperative and postoperative behaviour of children who underwent day-stay surgery. Patients were allocated into two groups. Group 1 consisted of 165 children aged between 6 and 47 months. Group 2 consisted of 174 children aged four years and older to a body weight of 50 kg. Each child received one premedicant. Both groups included alprazolam 0.005 mg/kg, midazolam 0.3 mg/kg and placebo. In addition Group 1 included chloral hydrate 40 mg/kg and Group 2 diazepam 0.25 mg/kg. Chloral hydrate produced superior conditions (more patients calm or asleep) at induction of anaesthesia. Postoperative behaviour and incidence of vomiting were similar for all drugs. No premedicant reduced anxiety in the older group. The time to awaken postoperatively with diazepam was longer than with placebo. Alprazolam and midazolam were unpalatable for children over four years and conferred no advantage over placebo.
Seventy neonatal to adolescent general surgical patients were studied to create an individual dose-response curve for the long-acting neuromuscular blocking agents, alcuronium and d-tubocurarine. The mean (SEM) ED95 of alcuronium was 196 (9), 271 (13) and 243 (8) micrograms/kg in infants, children and adolescents, respectively (P less than 0.01). d-tubocurarine showed a similar age dependent dose-response relationship. ED95 doses were 414 (40), 499 (41) and 445 (31) micrograms/kg, respectively. The onset time (time from intravenous administration to maximal effect) following equipotent dosages was 40-50% shorter in infants than in children or adolescents (1.5 vs 2.7 minutes, P less than 0.05).
Seventeen paediatric patients from 0.3 to 19 years old were studied to determine the individual dose-response curves and the maintenance requirements of alcuronium during N2O-O2-opioid anaesthesia. Alcuronium 300 micrograms/kg maintained the mean (SD) neuromuscular block at 90-95% for 62 34 min). This time was longest in patients of less than 1 year of age (92 min). The hourly maintenance requirement of alcuronium was 0.41 (0.12) times the individual ED95 dose. This value was comparable in infants, children and adolescents and indicates similar duration of effect of alcuronium in all paediatric age groups.
The rate of onset of action of d-tubocurarine (64 patients) or alcuronium (36 patients) was studied electromyographically in 100 children who had abdominal, bone or cerebral tumours. It was found that there was a significantly delayed onset (over three times longer than controls) or additional doses were required in patients with malignant liver, renal and bone tumours who received d-tubocurarine. The onset of alcuronium blockade was also prolonged but to a lesser extent. When tumours with an abnormal prolongation of onset of relaxation were successfully treated by chemotherapy and/or surgery, the response reverted to normal. Children with benign tumours or masses had normal responses. In contrast, neuroblastomas were associated with little prolongation of onset. Cerebral tumours showed a variable response, with the observed changes being unreliable indicators of degree of malignancy.
Myasthenia gravis, a rare disease in children, occurs in a variety of forms. The aetiology and clinical presentations are reviewed. Eight patients who were studied with electromyography are presented. The results show that, in general, patients with the usual pattern of disease are resistant to suxamethonium (ED95 3-4 times normal) and are sensitive to nondepolarizing relaxants. When the latter are used it is advisable to administer small increments with neuromuscular monitoring. One patient with the disease localised to the eyelid had normal EMG responses when monitored on the hand with ulnar nerve stimulation.
Suxamethonium was administered to 225 children aged from one to sixteen years, in doses varying from 0.1 to 0.5 mg/kg. Dose responses were determined. ED95 was 445 micrograms/kg in one to four year olds, 454 micrograms/kg in the five to ten years group and 270 micrograms/kg in eleven to fifteen year olds (P less than 0.05). There is a wider variability in patient responses to 0.1 and 0.2 mg/kg than to the higher doses. Sixty-two children in the three age groups were given suxamethonium 1 mg/kg. The time from injection to maximum block and to 50% recovery increased with increasing age (P less than 0.05).
Four patients with genetic cholinesterase abnormalities were studied with electromyography after being given suxamethonium 0.1 mg/kg. An abnormal homozygous patient was paralysed for 17 minutes. The duration of response in heterozygous patients was 2-4 minutes, being shorter when cholinesterase activity levels were near normal.
Suxamethonium is often used for intubation prior to the use of a nondepolarizing muscle relaxant. This study was performed to determine whether suxamethonium altered the dose of alcuronium required to produce neuromuscular block. The findings were that suxamethonium 1.0 mg/kg did not alter the depth, duration or reversibility of block if given before alcuronium 0.3 mg/kg. Reversal with neostigmine was more rapid following 50 micrograms/kg than after 25 micrograms/kg. If recovery from neuromuscular block was greater than 25 per cent, the lower dose produced satisfactory reversal, whether or not suxamethonium had been given previously.
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We exposed SV40-infected monkey kidney cells to 0, 30 or 150 J/m2 of UV-radiation, and isolated viral minichromosomes at various times after irradiation. Analysis of minichromosome-associated proteins by SDS-PAGE revealed the presence of two proteins, of 220 kD and 230 kD associated with minichromosomes from irradiated cells, but not from unirradiated controls. The larger protein was the less abundant, and was most evident in preparations from more heavily irradiated cells. Neither protein was associated with minichromosomes isolated 30 min after irradiation, but were apparent in minichromosome preparations isolated 1-4 h after UV treatment.
Cytosine spontaneously deaminates to form uracil, generating G/U pairs in DNA. We studied the repair of these lesions by introducing specific G/U pairs into the genome of SV40 and determining the fate of the mispaired bases in Simian cells. Analysis of 135 plaques obtained after transfection of the modified viral DNA indicates that G/U lesions were repaired to G/C in every case. This result indicates that G/U lesions are corrected with greater efficiency and specificity than any combination of DNA base/base mispairs, in transfected SV40 DNA.
Mammalian cells respond to UV-radiation by inducing an increased ability to support the survival of UV-damaged virus. We have tested whether the induction of enhanced viral reactivation (ER) reflects heightened UV-resistance of specific viral functions. For this, we examined the extent of ER for SV40 containing UV-damage in three functionally distinct regions of the SV40 genome: (i) the viral regulatory region, (ii) the early genes region and (iii) the late genes region. ER corresponding to a dose reduction factor of 43% was observed for damage in the early genes region. No ER was observed for damage in the regulatory or late genes regions. We conclude that ER in SV40 reverses the lethal disruption of an essential function peculiar to the viral early genes region. This function is almost certainly transcription.
The purpose of this study is to examine the usefulness of blood pressure recovery curves after submaximal exercise in apparently normotensive young adults as an early predictor for hypertension. Twenty-six college age males in 1977, with normal blood pressures at rest, were given the Harvard Step Test and postexercise blood pressures were recorded. Criteria were set that differentiated a hypertensive from a normotensive response to exercise. In 1987, these individuals were contacted regarding their blood pressure status. Nine out of ten subjects who demonstrated a hypertensive response to exercise in 1977, now have been given the diagnosis of hypertension. Eleven out of twelve subjects who demonstrated a normotensive response to exercise in 1977, now are still considered to be normotensive. A proposed hypothesis is that during the course of this disease, exercise can unmask hypertension in subjects who have the potential for developing hypertension but currently have a normal resting blood pressure.
The aim of this study was to determine whether certain characteristics of the follicular biochemistry, previously shown by us to be associated with oocyte developmental capacity, also reflected differences in oocyte appearance, and to determine the range of oocyte characteristics induced by ovarian stimulation. A representative sample of 33 human oocytes and associated follicular fluids was obtained after a follicular growth period considered suitable for IVF. Individual follicular fluid protein and proteoglycan levels, and follicular volume were compared with the morphological characteristics of each oocyte. Oocytes which retained the germinal vesicle nuclear status after exposure to human chorionic gonadotrophin tended to occur in small follicles (less than or equal to 2 ml) and to be highly vacuolated and with characteristic predicted a low potential for cleavage. Among those oocytes which had progressed to MII nuclear maturity [in the medium (2.5-6.5 ml) and large (greater than or equal to 7 ml) volume follicles] the degree of oocyte vacuolation was negatively correlated with alpha 1-antitrypsin level, while the degree of organelle clumping was correlated with proteoglycan and immunoglobulin levels. Only five of the oocytes (15%) in this sample had follicular characteristics consistent with a normal potential for pregnancy. These MII oocytes occurred within the medium volume range, had low vacuolation levels, and a low degree of organelle clumping. In contrast, those oocytes with a low potential for cleavage based on their follicular biochemistry, showed high cytoplasmic vacuolation levels.
Mismatched heteroduplexes arise as intermediates of several dissimilar genetic processes. The outcome of these genetic events will therefore be influenced by the efficiency and specificity of mismatch repair. We have studied the correction of base-base mispairs in simian and human fibroblasts by transfecting the cells with derivatives of SV40 DNA, each harboring a single mispair in a defined orientation. Analysis of plaques revealed that correction efficiencies for homomispairs followed the pattern G.G greater than C.C greater than or equal to A.A greater than T.T. Repair bias was influenced by flanking sequences. Correction efficiences for heteromispairs followed the pattern of G.T greater than A.C greater than C.T greater than A.G and repair favored the retention of G + C by a substantial margin. This repair specificity could lead to a gene conversion bias favoring the accumulation of G + C in sequences subject to high levels of recombination or unequal exchange.