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Biomedical subjects

R Robertson

Publications and source records attributed to R Robertson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Thermal avoidance during flight in the locust Locusta migratoria

In this paper, thermal avoidance in tethered flying locusts is described for the first time. Changes in body posture examined using high-speed cinematography revealed that the animals responded to a laterally positioned heat source with contralaterally directed abdomen and hindleg ruddering, behavioural patterns resembling manoeuvres observed in collision avoidance and in response to auditory signals. The analysis also showed that, during stimulation, left and right forewing depression became asymmetrical during the downstroke but remained symmetrical during the upstroke. Hindwing depression and elevation remained symmetrical during stimulus presentations. Electromyographic recordings from the left and right first basalar muscles (M97; forewing depressors) showed that contralateral depressor muscle activity was advanced by 10­12 ms relative to that on the stimulated side. There was also an increase in burst duration on the contralaterally stimulated side and an increase in wingbeat frequency of approximately 3 Hz. Ablation experiments showed that removal of the antennal flagella, which are the site of previously described thermoreceptors, did not abolish thermal avoidance manoeuvres. We conclude that thermal avoidance is triggered by an infrared sensitivity that is not mediated by the compound eyes, the ocelli or the antennal flagella.

Journal Article↗
PubMed1996

Recovery of the flight system following ablation of the tegulae in immature adult locusts

The capacity of the flight system to recover from ablation of the tegulae was studied in immature adult Locusta migratoria and compared with recovery in mature adults. We ablated the hindwing tegulae or all tegulae in adult locusts either 1 day after the imaginal moult (immature locusts) or 2 weeks after the imaginal moult (mature locusts). We monitored recovery throughout the recovery period by using a stroboscope to measure the wingbeat frequency of tethered locusts. In addition, we measured other parameters of the flight motor pattern using electromyographic electrodes implanted into recovered locusts. Both methods of monitoring recovery yielded the same results. There was no reduction, during adult maturation, in the capacity of the locust flight system to recover from the loss of these proprioceptors. Plasticity of the locust flight system was therefore maintained in the mature adult locust. This suggests that the flight system is not fixed and simply implemented when the locust reaches adulthood, but that the circuitry can be remodelled throughout the animal's life to produce behaviour adapted to the needs and constraints of the individual.

Journal Article↗
PubMed1996

Validity of the Borg perceived exertion scale for use in semirecumbent ergometry during immersion in water.

This investigation examined the validity of the Borg 15-category Ratings of Perceived Exertion (RPE) scale during semirecumbent exercise in 32 degrees C water. 9 men undertook 12 8-min. trials at 3 power outputs and 4 pedal-crank rates. The power output was distributed between the arms (20%) and legs (80%). RPEs were measured for the arms, legs, chest, and over-all body. Correlation coefficients for RPE expressed as a function of power output and gross metabolic efficiency (MEG) ranged from .56 to .83 and .54 to .70, respectively, for each pedal-crank rate. Validity coefficients were greatest at those pedal-crank rates having the highest MEG. The Borg 15-category RPE scale is valid for use during semirecumbent exercise in water.

Adult↗
PubMed1996

The effects of hospital downsizing on staffing and quality of care.

Hospital managers are making aggressive changes in their caregiver staffs to meet challenges such as reductions in utilization and capitated care. Managers are doing this to decrease the cost of care while maintaining or improving quality of care. However, the literature addressing the impact of hospital staffing practices on quality of care indicates that these changes may negatively influence quality. Department administrators must be cautious, yet proactive in their approach to patient care restructuring in order to ensure continued quality as well as cost-effectiveness.

Cost Savings↗
PubMed1995

Severe acidosis alone does not predict mortality in the trauma patient.

BACKGROUND: Because severe acidosis is an indicator of poor prognosis in trauma patients, medical records of these patients were analyzed to determine whether aggressive resuscitation was appropriate. PATIENTS AND METHODS: Data from a level 1 trauma center registry were reviewed retrospectively to identify patients with a pH < or = 7.0. Thirty-seven patients were identified. Severely acidotic patients were compared to average trauma patients in terms of demographics, resuscitation, injury, and outcome. Surviving acidotic patients were also compared to nonsurviving acidotic patients. RESULTS: Half of the severely acidotic group survived initial resuscitation with approximately one third surviving to leave the hospital. There were no chronically disabled survivors. Nonsurviving acidotic patients were more unstable, more neurologically depressed, and more severely injured. Resuscitation efforts did not consume excessive hospital resources. CONCLUSION: Severe acidosis alone is not a sufficiently powerful predictor of outcome to justify withholding resuscitation; however, when combined with coma and shock, this condition had no survivors in this small series.

Acidosis↗
PubMed1995

Metabolic and perceptual responses during arm and leg ergometry in water and air.

This investigation determined metabolic (i.e., kcal.min-1) responses and ratings of perceived exertion (RPE) for varying pedal-crank rates (PCR) and power outputs (PO) during arm and leg exercise in thermoneutral air (TA) and water (TW). Nine males (age 28.2 yr; leg cycle VO2peak 3.4 l.min-1) undertook the 24 exercise trials. During the TW trials kcal.min-1 were less (P < 0.05): at 50 W for 40 (X +/- SE; 10.9 +/- 0.8) than 50 (8.2 +/- 0.2), 60 (8.2 +/- 0.6), or 70 (7.4 +/- 0.3) rev.min-1 and at 100 W for 40 (15.2 +/- 0.7), 50 (14.0 +/- 1.1), and 60 (13.8 +/- 0.7) than 70 (12.1 +/- 0.5) rev.min-1. All other comparisons of kcal.min-1 between PCR at the three PO were not significant. During the TA trials kcal.min-1 were less (P < 0.05): at 50 W for 40 (11.4 +/- 0.3) than 60 (9.7 +/- 0.4) and 70 (9.1 +/- 0.4) rev.min-1 and for 50 (11.0 +/- 0.5) than 70 rev.min-1. During the TW trials: RPE-Arms and RPE-Overall at 50 W were lower (P < 0.05) for 40 (8.1 +/- 0.5; 8.3 +/- 0.4) than 60 (9.6 +/- 0.5; 9.8 +/- 0.6) and 70 (9.3 +/- 0.5; 9.9 +/- 0.7) rev.min-1, RPE-Legs at 50 W was lower (P < 0.05) for 40 (8.3 +/- 0.4) than 70 (9.9 +/- 0.7) rev.min-1. All other comparisons of RPE between PCR at the three PO were not significant.

Adult↗
PubMed1993

Prenatal diagnosis of colon atresia.

We report a case of colon atresia diagnosed pre-natally at 32 weeks' gestation. The fetal transverse colon was dilated. Complete atresia of the middle transverse colon was confirmed after birth. Small bowel dilatation (and clinical obstruction) did not develop until after 24 h of age.

Adult↗
PubMed1993

The effects of cue level, hypnotizability, and state instruction on responses to leading questions.

Two sessions were conducted in which independent groups of 86 high- and 85 low-susceptible subjects, responding individually under waking or hypnotic instruction, answered high- and low-cued leading questions about a video event that depicted shooting at an airport. The two sessions were separated by 1 week, and the same questions were asked in both sessions. It was predicted that highly susceptible subjects responding under hypnotic instruction would show the most evidence of accepting false information via strongly cued leading questions. Results showed general effects for leading questions and level of susceptibility but no firm support for the involvement of hypnosis. Data are discussed in terms of both the linguistic and social factors that appear to have operated on subjects in the study, results overall highlight the strong influence of level of susceptibility on subjects' acceptance of false information.

Adult↗
PubMed1993

Light and heavy lysosomes: characterization of N-acetyl-beta-D-hexosaminidase isolated from normal and I-cell disease lymphoblasts.

We previously reported that I-cell disease lymphoblasts maintain normal or near-normal intracellular levels of lysosomal enzymes, even though N-acetylglucosamine-1-phosphotransferase activity is severely depressed or absent (Little et al., Biochem. J., 248, 151-159, 1987). The present study, employing subcellular fractionation on colloidal silica gradients, indicates that both light and heavy lysosomes isolated from I-cell disease and pseudo-Hurler polydystrophy lymphoblasts possess normal specific activity levels of N-acetyl-beta-D-hexosaminidase, alpha-D-mannosidase and beta-D-glucuronidase. These current findings are in contrast to those of cultured fibroblasts from the same patients, where decreased intralysosomal enzyme activities are found. Column chromatography on Ricinus communis revealed that N-acetyl-beta-D-hexosaminidase in both heavy and light I-cell disease lysosomal fractions from lymphoblasts possesses an increased number of accessible galactose residues (30-50%) as compared to the enzyme from the corresponding normal controls. Endo-beta-N-acetylglucosaminidase H treatment of N-acetyl-beta-D-hexosaminidase from the I-cell lysosomal fractions suggests that the majority of newly synthesized high-mannose-type oligosaccharide chains are modified to complex-type carbohydrates prior to being transported to lysosomes. This result from lymphoblasts differs from previous findings with fibroblasts, where N-acetyl-beta-D-hexosaminidase from I-cell disease and pseudo-Hurler polydystrophy lysosomes exhibited properties associated with predominantly high-mannose-type oligosaccharide chains.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Substitution of l-leucovorin for d,l-leucovorin in the rescue from high-dose methotrexate treatment in patients with osteosarcoma.

Studies in which high-dose methotrexate (HDMTX) is used for the treatment of osteosarcoma have utilized commercial formulations of d,l-leucovorin (leucovorin calcium) for rescue from potential methotrexate (MTX) toxicity. These formulations are racemic mixtures containing equal amounts of d and l isomers of leucovorin. All of the available data indicate that the l isomer is the pharmacologically active diastereomer. A clinical study was conducted to determine if l-leucovorin was as safe and efficacious as d,l-leucovorin in the rescue of patients with osteosarcoma who were treated with HDMTX (12.5 g/m2 over 6 h). Because d,l-leucovorin consists of equal proportions of d and l isomers, l-leucovorin was administered at half the usual dose of d,l-leucovorin. In patients with delayed methotrexate excretion, l-leucovorin doses were escalated from 7.5 to 50 mg every 3 h until the MTX level was 0.3 mumol/l or less. Due to the low incidence of osteosarcoma, a control group of patients previously treated with d,l-leucovorin was utilized for comparison. Efficacy of l-leucovorin was determined by its ability to prevent HDMTX-associated toxicity. Demographic and clinical toxicity data from three patients who received 22 courses of MTX rescued with l-leucovorin were compared with data from six patients who had received 42 MTX courses rescued with d,l-leucovorin. Some liver function abnormalities and leukocyte elevations were found in both groups and were attributed to MTX administration. No clinical toxicity attributable to l-leucovorin was observed. l-Leucovorin in half the d,l-leucovorin dose was (equally) effective as a rescue treatment.

Adolescent↗
PubMed1992

Secondary acute non-lymphoblastic leukemia in two children following treatment with a cis-diamminedichloroplatinum-II-based regimen for osteosarcoma.

Acute nonlymphocytic leukemia (ANLL) developed in 2 of 142 pediatric patients with osteosarcoma treated with a cis-diamminedichloroplatinum-II (CDP)-based regimen: acute monomyelogenous leukemia (M4) with a normal female karyotype in one and acute myelogenous leukemia (M2) with t (8,21) in the other. The ANLLs occurred, respectively, in each patient 3 and 4 years after the initial diagnosis of osteosarcoma. In contrast to most of the adult experience and consistent with the majority of reported ANLL in children, the disease was characterized by an absence of the smoldering phase and cytogenetic findings similar to those seen in de novo ANLL.

Adolescent↗
PubMed1991

Results and complications of angioplasty in aortoiliac disease.

Percutaneous transluminal angioplasty was used to treat 340 aortoiliac lesions in 200 patients who were followed for as long as 90 months (mean, 28.7 months; median, 23 months). The initial success rate was 94.7% for lesions and 93.0% for patients. The indications for percutaneous transluminal angioplasty included claudication in 117 patients (58.5%), rest pain or ischemic night pain in 47 (23.5%), limb salvage in 33 (16.5%), and aiding in wound healing in three (1.5%). In the series, 70% of the patients had two or more cardiovascular risk factors. Angioplasty was initially unsuccessful in 14 patients, and 10 patients were lost to follow-up. Follow-up was obtained in 176 patients. The long-term results were analyzed using the life table method to determine cumulative patency. Fourteen patients were considered failures because of recurrent disease or symptoms. The projected 7.5-year cumulative patency rate was 85%. When the response to redilatation was considered, the projected 7.5-year cumulative patency rate was 92%. The results indicate that percutaneous transluminal angioplasty can successfully correct aortoiliac lesions and provide a long-term benefit for as long as 7.5 years.

Angioplasty, Balloon↗