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Biomedical subjects

D A Smith

Publications and source records attributed to D A Smith.

At least 307 records · Page 17Linked to original sources
PubMed1986

Theory of the rotational contribution to facilitated diffusion.

Gros and others have recently shown experimentally that the facilitated diffusion of protons carried by a form of haemoglobin is enhanced by rotational diffusion of the carrier, whereas facilitated diffusion of oxygen by the same carrier is not. In this paper the theory of facilitated transport by rotating carriers is developed from first principles. The theory confirms Gros's findings that (i) the rotational contribution appears only when the angle of rotational diffusion over the average time the proton remains bound is small and (ii) under these conditions rotation enhances the normal translational contribution by a factor 1/2 at the lowest carrier concentrations. The theory also shows that there must be a rotational boundary layer.

Binding Sites↗
PubMed1986

Exercise capacity in chronic renal failure patients managed by continuous ambulatory peritoneal dialysis.

Exercise capacity is documented to be poor in patients with end stage renal failure undergoing regular hemodialysis, but there is little information about exercise capacity in patients on continuous ambulatory peritoneal dialysis (CAPD). We studied a group of 18 patients undergoing CAPD, with a variety of cardiorespiratory disorders, using a progressive load treadmill exercise test. The influence of intraperitoneal fluid on work capacity was also assessed. The mean maximum oxygen uptake (VO2max) of the CAPD patients was reduced considerably (14.6 ml kg-1 min-1) compared with matched control subjects (33.6 ml kg-1 min-1). This corresponded to the difficulty experienced by these patients in carrying out daily activities. There was no significant change in VO2max or in maximum heart rate with the peritoneal cavity full. We conclude that physical fitness is poor in CAPD patients and that the infusion of dialysis fluid into the peritoneal cavity does not affect physical work capacity further.

Adult↗
PubMed1986

In vivo regulation of beta-adrenergic receptors on human mononuclear leukocytes: assessment of receptor number, location, and function after posture change, exercise, and isoproterenol infusion.

We studied the regulation of beta-adrenergic receptors in human mononuclear leukocytes (MNL). Total receptor number was determined as specific binding at 4 C of [3H] dihydroalprenolol or [125I]iodopindolol, and redistributed receptors were defined as those binding sites to which the hydrophilic antagonist CGP-12177 did not have access. Receptor function was assessed as cAMP accumulation stimulated by isoproterenol. In in vitro experiments, high concentrations of isoproterenol desensitized receptor function and promoted redistribution of about 80% of the receptors away from the cell surface. However, three in vivo protocols (upright posture for 3 h, moderate exercise, and infusion of isoproterenol for 30 min) redistributed few beta-adrenergic receptors on MNL. The 30-min isoproterenol infusion did not alter later cAMP accumulation, but posture change and exercise increased isoproterenol-stimulated cAMP accumulation in intact MNL. Infusion of isoproterenol for 120 min redistributed 9 +/- 2% (+/- SEM) of the receptors and decreased isoproterenol-stimulated cAMP accumulation by 19 +/- 6%. Isoproterenol-stimulated adenylate cyclase activity in membranes isolated from MNL previously was found to be decreased with upright posture, and we confirmed these findings in assays that did not include exogenous GTP, but instead relied upon guanine nucleotides retained in the membrane preparation. However, when excess GTP was included, isoproterenol-stimulated adenylate cyclase activity in MNL membranes was not altered by posture change. We conclude that substantial receptor redistribution of beta-receptors on MNL does not readily occur in physiological situations.

Adenylyl Cyclases↗
PubMed1986

Transoral unilateral facetectomy in the management of unilateral anterior rotatory atlantoaxial fracture/dislocation: a case report.

An unusual case of unilateral anterior rotatory atlantoaxial fracture/dislocation with neurological deficit is presented. The injury could not be reduced by skeletal traction, but was successfully reduced by partial facetectomy at C-1, C-2 accomplished through a transoral exposure of the atlantoaxial region combined with labiomandibularglossotomy. To the best of our knowledge, this is the first instance of an injury of this type to be so managed. The details of the operative procedure are described, and the subject of rotatory atlantoaxial dislocation is reviewed.

Adult↗
PubMed1986

Precision of measurement of bone density with a special purpose computed tomography scanner.

A new, special purpose, low-dose computed tomography scanner has been developed for the precise measurement of bone density in the distal radius. The instrument includes an 125I source and four scintillation detectors which are scanned across a section of the forearm to produce a cross-sectional image. A number of innovative features have been included to improve patient comfort and scanner precision. The reproducibility for trabecular bone measurement was 0.5% for repeated scans in 22 subjects. The long-term precision in a group of normal subjects was better than 5 mg cm-3. The high precision and the separate measurement of trabecular bone make this technique suitable for the longitudinal study of bone density in metabolic bone disease.

Adult↗
PubMed1986

The law and intensive care. The role of the courts in the ethical decision-making process.

As intensive care decision making has become more complex in light of continuing technologic advances, our legal system has become increasingly involved in defining the legal parameters of the decision-making process. Although the law differs substantially from state to state, certain standards of broad applicability appear to be emerging. The medical community must strive to ensure that it is responsive to the legitimate need of government to set appropriate standards, in order to forestall the imposition of unnecessarily restrictive standards.

Adult↗
PubMed1986

Use of purified lyophilized human lactate dehydrogenase isoenzymes in a study of the measurement of lactate dehydrogenase activity.

We examined the stability of human lactate dehydrogenase (EC 1.1.1.27; LD) isoenzymes 1, 2, and 3--purified to specific activities of about 200 kU/g--when lyophilized in a buffered stabilized matrix of bovine albumin. Each isoenzyme was prepared at two activity concentrations and stored at -20, 4, 20, 37, and 56 degrees C for as long as six months. LD-1 activity decayed with zero-order kinetics, LD-2 and LD-3 with first-order kinetics. The extrapolated half-lives of these preparations at -20 degrees C varied between 80 and 530 years. Stability of reconstituted samples stored at 4 degrees C was excellent for LD-1 but poor for LD-2 and LD-3. We suggest that preparations of human LD-1 be further investigated as a possible reference material.

Freeze Drying↗
PubMed1986

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Attitude of Health Personnel↗
PubMed1985

Exercise heart rates at different serum digoxin concentrations in patients with atrial fibrillation.

Heart rate at rest and during increasing workloads was measured in a double blind study of 12 patients with chronic atrial fibrillation when serum concentrations of digoxin were nil and at low and high therapeutic values. Twelve normal subjects were studied for comparison. The heart rate at all levels of exercise in most patients with atrial fibrillation was not adequately controlled by any serum digoxin concentration tested despite a reduction in heart rate with increasing serum digoxin concentrations. Control of the resting heart rate, even in patients with high serum digoxin concentrations, did not ensure adequate control of the heart rate during work rates equivalent to regular daily activities.

Adult↗
PubMed1985

Immunocytochemistry of cerebellar astrocytomas: with a special note on Rosenthal fibres.

Two astrocytic immunocytochemical markers, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS), were demonstrated in cerebellar astrocytomas. The staining pattern for both antigens was similar, but GFAP demonstrated astrocytic processes better, while GS staining was stronger in poorly fibrillated cells. The various astrocytic forms, bipolar, stellate, bi- and multi-nucleate cells, displayed different immunostaining. Rosenthal fibres also showed a varying pattern of reaction: larger fibres were entirely negative or had a narrow peripheral ring of dense reaction product, but occasional smaller fibres were positive. The varying proportion of filamentous and amorphous material within Rosenthal fibres could be responsible for this finding. The pale granular bodies possessed a GFAP-positive limiting membrane and GS-positive contents, suggestive of their astrocytic origin. Immunohistochemistry of GFAP and GS has contributed to the knowledge of cellular differentiation and secondary changes in cerebellar astrocytomas.

Astrocytoma↗
PubMed1985

Mutations in genes encoding essential mitotic functions in Drosophila melanogaster.

Temperature-sensitive mutations at 15 loci that affect the fidelity of mitotic chromosome behavior have been isolated in Drosophila melanogaster. These mitotic mutants were detected in a collection of 168 EMS-induced X-linked temperature-sensitive (ts) lethal and semilethal mutants. Our screen for mutations with mitotic effects was based upon the reasoning that under semirestrictive conditions such mutations could cause an elevated frequency of mitotic chromosome misbehavior and that such events would be detectable with somatic cell genetic techniques. Males hemizygous for each ts lethal and heterozygous for the recessive autosomal cell marker mwh were reared under semirestrictive conditions, and the wings of those individuals surviving to adulthood were examined for an increased frequency of mwh clones. Those mutations producing elevated levels of chromosome instability during growth of the wing imaginal disc were also examined for their effects on chromosome behavior in the cell lineages producing the abdominal cuticle. Fifteen mutations affect chromosome behavior in both wing and abdominal cells and thus identify loci generally required for the fidelity of mitotic chromosome transmission. Mapping and complementation tests show that these mutations represent 15 loci. One mutant is an allele of a locus (mus-101) previously identified by mutagen-sensitive mutants and a second mutant is an allele of the lethal locus zw 10.--The 15 mutants were also examined cytologically for their effects on chromosomes in larval neuroblasts. Taken together, the results of our cytological and genetical studies show that these mutants identify loci with wild-type functions necessary for either maintenance of chromosome integrity or regular disjunction of chromosomes or chromosome condensation. Thus, these mutations define a broad spectrum of genes required for the normal execution of the mitotic chromosome cycle.

Alleles↗
PubMed1985

The nasal absorption of sodium cromoglycate in the albino rat.

The intranasal absorption of sodium cromoglycate has been investigated in the adult male COBS/Wistar rat. Sodium cromoglycate (1 mg kg-1) was instilled into the nasal cavities and for comparison animals were also similarly dosed intravenously or sub-lingually. Serial samples of blood or bile were collected. After intravenous administration, the area under the plasma concentration curve (AUC0-infinity) was 32 micrograms min ml-1 corresponding to a plasma clearance of 13 ml min-1 and an elimination rate constant of 0.049 min-1. Plasma concentrations of radioactivity after intranasal administration rose to a mean peak of 0.3 micrograms ml-1 approximately 20 min after dosing and fell to 0.03 micrograms min ml-1 at 3 h. The AUC0-3 was 19 micrograms min ml-1 corresponding to an absorption of 60% over 3 h. The absorption rate constant (ka) was 0.059 min-1. The total amount of sodium cromoglycate excreted in bile after intravenous administration was 56%. The amount of compound excreted in the bile was 30% after intranasal administration corresponding to an absorption of 53%. Plasma and bile data therefore show good agreement. Total excretion in the bile over 3 h after sub-lingual administration was 3%, demonstrating that this route made no significant contribution to the intranasal results. The absorption of sodium cromoglycate is independent of variations in the technique including changes in the orientation of the rat or blocking of the nasopalatine. The techniques used minimized other competing nasal clearance processes such as mucociliary clearance.

Absorption↗
PubMed1985

Conjugation of disodium 6-chloro-4-oxo-10-propyl-4H-pyrano[3,2-g]quinoline-2,8-dicarboxy late with glutathione in the rat.

Disodium 6-chloro-4-oxo-10-propyl-4H-pyrano[3,2-g]quinoline- 2,8-dicarboxylate (I) is conjugated with glutathione (GSH) both in vitro and in vivo by nucleophilic replacement of the chlorine substituent in (I). The reaction is catalysed by rat-liver supernatant. The GSH conjugate is the principal excretory product in the rat bile after i.v. administration of (I), accounting for approximately 60% of the dose and 95% of the biliary excretion. Its structure was determined by synthesis and spectroscopic analysis.

Animals↗
PubMed1985

Validation of the nursing diagnosis of urinary retention.

The literature was reviewed in an effort to find or develop a taxonomy for alterations in urinary elimination. A questionnaire was used to validate defining characteristics of one of these diagnosis. Support for the label was found. Examination of additional labels is useful in differentiating types of incontinence.

Evaluation Studies as Topic↗