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Biomedical subjects

R Ackerman

Publications and source records attributed to R Ackerman.

18 recordsLinked to original sources
PubMed2005

Ergonomics and human factors in endoscopic surgery: a comparison of manual vs telerobotic simulation systems.

BACKGROUND: Minimally invasive surgical techniques expose surgeons to a variety of occupational hazards that may promote musculoskeletal disorders. Telerobotic systems for minimally invasive surgery may help to reduce these stressors. The objective of this study was to compare manual and telerobotic endoscopic surgery in terms of postural and mental stress. METHODS: Thirteen participants with no experience as primary surgeons in endoscopic surgery performed a set of simulated surgical tasks using two different techniques--a telerobotic master--slave system and a manual endoscopic surgery system. The tasks consisted of passing a soft spherical object through a series of parallel rings, suturing along a line 5-cm long, running a 32-in ribbon, and cannulation. The Job Strain Index (JSI) and Rapid Upper Limb Assessment (RULA) were used to quantify upper extremity exposure to postural and force risk factors. Task duration was quantified in seconds. A questionnaire provided measures of the participants' intuitiveness and mental stress. RESULTS: The JSI and RULA scores for all four tasks were significantly lower for the telerobotic technique than for the manual one. Task duration was significantly longer for telerobotic than for manual tasks. Participants reported that the telerobotic technique was as intuitive as, and no more stressful than, the manual technique. CONCLUSIONS: Given identical tasks, the time to completion is longer using the telerobotic technique than its manual counterpart. For the given simulated tasks in the laboratory setting, the better scores for the upper extremity postural analysis indicate that telerobotic surgery provides a more comfortable environment for the surgeon without any additional mental stress.

Arm↗
PubMed1996

Acyl CoA and lipid synthesis from ketone bodies by the extramitochondrial fraction of hepatoma tissue.

The compartmentation of the pathway for the synthesis of lipids from ketone bodies was examined in a cell free, post-mitochondrial supernatant fraction of malignant Morris hepatoma 7777 tissue. A fortified supernatant system effectively incorporated radioactive D(-)-3-hydroxybutyrate and acetoacetate into cholesterol and fatty acids, and both ketone bodies were directly converted to their CoA thioesters. Furthermore, a microsome-free (100,000 x g) cytosolic fraction was also able to acylate 3-hydroxybutyrate to 3-hydroxybutyryl CoA. No previous identification of this enzyme activity has been described. These results which characterize a distinct extramitochondrial pathway for conversion of 3-hydroxybutyrate as well as acetoacetate into lipids also suggest the possibility of a previously undetected enzymatic activity for utilization of this ketone body.

3-Hydroxybutyric Acid↗
PubMed1994

HPLC determination of 1,2-diethyl-3-hydroxypyridin-4-one (CP94), its iron complex [Fe(III) (CP94)3] and glucuronide conjugate [CP94-GLUC] in serum and urine of thalassaemic patients.

Sensitive and selective high performance liquid chromatographic (HPLC) methods for the quantification of 1,2-diethyl-3-hydroxypyridin-4-one (CP94), its iron complex [Fe(III) (CP94)3] and glucuronide metabolite (CP94-GLUC) in urine and serum of thalassaemic patients are described. Three separate analyses are involved. The first assay quantifies both CP94 and its iron complex. This procedure requires the conversion of the iron complex to the free ligand and is carried out using diethylenetriaminepentaacetic acid (DTPA). CP94 and the internal standard, 1-propyl-2-ethyl-3-hydroxypyridin-4-one (CP95) present in either serum or urine are then extracted at pH 7.0 with dichloromethane. Extraction efficiency is 96.0 +/- 5.6% and 100 +/- 7.1% for CP94 and CP95, respectively, and 31.2 +/- 2.1% at 30 microM and 53.2 +/- 4.2% at 300 microM for the corresponding iron complex. In the second assay, samples are incubated (16 h) with beta-glucuronidase and processed as before. In this assay, the drug, its iron complex and glucuronide conjugate are measured. In the third assay the iron complex of CP94, [Fe(III) (CP94)3] is quantified. From the three separate analyses it is possible to calculate the individual concentrations of the three separate components present in serum and urine of thalassaemic patients. Calibration for both components, i.e. CP94 (assays 1 and 2) and its iron complex (assay 3) are linear with correlation coefficients > 0.99 and are reproducible over the required concentration range of 0-500 microM for the free ligand and 0-100 microM for the iron complex. The minimum quantifiable level is 0.5 microM for the free ligand and 1.0 microM for the iron complex.

Chromatography, High Pressure Liquid↗
PubMed1993

Characterisation of mutations in the Klebsiella pneumoniae nitrogen fixation regulatory gene nifL which impair oxygen regulation.

The nifL gene product of Klebsiella pneumoniae inhibits the activity of the positive activator protein NifA in response to increased levels either of fixed nitrogen or of oxygen in the medium. In order to demonstrate that the responses to these two effectors are discrete we have subjected nifL to hydroxylamine mutagenesis and isolated nifL mutants that are impaired in their ability to respond to oxygen but not to fixed nitrogen. Two such mutations were sequenced and shown to be single base pair changes located in different parts of nifL. The amino acid sequence of NifL shows limited homology to the histidine protein kinases which comprise the sensing component of bacterial two-component regulatory systems. In the light of the location of one of the oxygen-insensitive mutations (Leu294Phe) we have reassessed this homology and we suggest that the Gln273-Leu317 region of NifL may facilitate interactions between NifL and NifA.

Amino Acid Sequence↗
PubMed1992

Quantification of desferrioxamine and its iron chelating metabolites by high-performance liquid chromatography and simultaneous ultraviolet-visible/radioactive detection.

An HPLC-based method for quantification of desferrioxamine (DFO) and its iron chelating metabolites in plasma has been developed. This assay overcomes stability problems associated with DFO by the addition of radioactive iron to convert unbound drug and metabolites to radio-iron-bound species. A dual detection system utilizing uv-vis absorption and radioactive (beta-particle) detector was used to quantify total and radio-iron-bound species. The use of octadecyl silanol solid phase extraction cartridges permits concentration of samples and allows accurate quantification of drug and metabolites down to 0.1 nmol/ml.

Chromatography, High Pressure Liquid↗
PubMed1985

Pheochromocytoma and the normal adrenal medulla: improved visualization with I-123 MIBG scintigraphy.

The radiopharmaceutical iodine 131 metaiodobenzylguanidine (I-131 MIBG) has been shown to locate pheochromocytomas scintigraphically with a false-negative rate of approximately 13%. To improve image quality and reduce the false-negative rate, I-123 was examined as a radioactive label for MIBG, as it has many advantages over I-131, including superior dosimetry and better detection efficiency. Diagnostic doses of 0.5 mCi (18.5 MBq) I-131 MIBG and 10.0 mCi (370.0 MBq) I-123 MIBG with nearly equivalent radiation dosimetries were compared in 18 patients with known or suspected pheochromocytomas. Images of superior quality were obtained with I-123 MIBG in 18 of 18 patients, and in eight cases lesions not visualized on I-131 MIBG scintigraphy were portrayed. A further advantage of I-123 MIBG is that it permits single photon emission computed tomography (SPECT). This was performed in six cases and provided additional information in three cases. The adrenal medullae were definitely visualized using I-123 scintigraphy in eight of 14 patients still possessing adrenal glands, whereas I-131 MIBG images portrayed the adrenal medulla in only one of 14 cases. Five remaining patients had multiple abdominal tumor deposits that were difficult to differentiate from normal adrenal medullae.

3-Iodobenzylguanidine↗
PubMed1984

Hepatotoxic reactions in a patient treated with etretinate.

Hepatotoxic reactions and eosinophilia developed in a 74-year-old woman who had been treated with an aromatic retinoid compound, etretinate, for severe psoriasis palmaris et plantaris. Rapid improvement in her condition followed discontinuation of the drug therapy. Liver enzyme elevations recurred after reinstitution of etretinate therapy; these levels quickly returned to normal after the drug therapy was again discontinued. Our patient's reaction to etretinate may have been a hypersensitivity reaction.

Aged↗
PubMed1983

Effect of maternal nutritional status on immunological substances in human colostrum and milk.

Substances in colostrum and breast milk confer significant disease resistance to the breast-fed infant. The influence of maternal nutritional status on both immunological and nonimmunological milk factors was studied in a group of 23 Colombian women during the first 2 months of lactation. Maternal malnutrition was characterized by significantly lower weight/height ratio, creatinine/height index, total serum proteins, serum albumin, and serum IgG and IgA. The colostrum of malnourished mothers contained only one-third the normal concentration of immunoglobulin G and less than half the normal level of albumin. Significant reductions in colostrum levels of IgA and the fourth component of complement (C4) were also observed in the malnourished group. No differences were observed in colostral concentrations of lysozyme, C3 complement, or IgM. Titers of antibody in milk directed against respiratory syncytial virus were not influenced by maternal nutritional status. The differences noted above tended to disappear in mature milk, concomitant with improvement in the nutritional status of malnourished mothers during the first several weeks postpartum. We conclude that the protective qualities of colostrum and milk may be significantly influenced by maternal nutritional status.

Adult↗
PubMed1982

Levels of human chorionic gonadotropin in unruptured and ruptured ectopic pregnancy.

Eighty-eight presenting with signs and symptoms that suggested ectopic pregnancy, all of whom had a positive radioreceptorassay (Biocept-G), were studied. Sixty-one patients (69%) were found to have intrauterine pregnancy. Twelve (14%) had unruptured tubal ectopic pregnancy with a mean (+/- SEM) human chorionic gonadotropin (hCG) level of 1190 +/- 320 mIU/ml, whereas 15 (17%) with ruptured ectopic pregnancies had a mean hCG level of 4160 +/- 400 mIU/ml. Among these 2 types of ectopic pregnancy, the mean hCG levels were statistically different (t = 5.0, P less than .001). Possible reasons for these differences are suggested, and the clinical implications of this finding are discussed.

Chorionic Gonadotropin↗
PubMed1982

Pharmacokinetics of Damvar.

The pharmacokinetics of granulated Damvar (delta-(2-amino-6-hydroxy-3,4-dihydro-4-oxo-5-pyrimidinyl) valeric acid) after a single oral dose of 1000 mg was studied in 10 subjects with neoplastic disease. The rate of Damvar absorption from the digestive tract is not very fast. Maximal serum levels (13.5 micrograms/ml) were recorded 3 h after administration with minor interpersonal variations. The time course of Damvar serum concentrations coincides with its distribution in a two-compartmental pharmacokinetic model with biological half-life of 9.72 +/- 0.84 h. Only a small amount of Damvar is eliminated in urine during a period of 24 h (3.1% of the administered dose). Its renal clearance is also low (0.05 ml/s). The analysis of Damvar excretion in urine shows that kidneys play a minor role in its elimination from the body. Therefore the attention should be concentrated on the effect of Damvar administration in patients with disturbed metabolic functions.

Administration, Oral↗
PubMed1980

Distribution of ventilation in the turtle Pseudemys scripta.

Spontaneously ventilating turtles, Pseudemys scripta, were allowed to rebreathe 133Xe to equilibrium. Frequent gamma camera images were obtained and processed to allow regional evaluation of ventilation. The distribution of ventilation was markedly inhomogeneous, with washin to equilibrium most rapid in anterior lung compartments and slowest in posterior lung compartments. Similarly washout from equilibrium was most rapid in anterior compartments and slowest in posterior compartments. During apnea intercompartmental gas exchange occurred rapidly during spontaneous activity of the limbs or, more slowly, during episodes ascribed to regional contraction of lung smooth muscle. Despite inhomogeneous ventilation, overall washout of 133Xe could be monoexponential. A simple series model of the turtle lung is consistent with the inhomogeneous ventilation observed.

Animals↗
PubMedDate not supplied

Whole blood viscosity parameters and cerebral blood flow.

This report describes the statistical relationship of several whole blood viscosity parameters and cerebral blood flow (CBF) in 53 consecutive patients and normal controls. Significant correlations were present between CBF and serum fibrinogen (P = .05), hematocrit (P less than .05), and a relationship involving both fibrinogen and hematocrit (P less than .01). We conclude that heightened whole blood viscosity does correlate with decreased cerebral blood flow in the ranges measured in our patients, that both fibrinogen and hematocrit must be taken into consideration in viscosity determinations, and that changes in viscosity may have an important effect on CBF in regions of low flow.

Adult↗