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Biomedical subjects

D J Anderson

Publications and source records attributed to D J Anderson.

At least 397 records · Page 22Linked to original sources
PubMed1984

Parametric analysis of dynamic postural responses.

A detailed theoretical understanding of postural control mechanisms must be preceded by careful quantification of both the deterministic and stochastic aspects of postural behavior of normal and abnormal subjects under various dynamic conditions. Toward this end, concise parametric transfer function plus noise models were derived for both shoulder and waist position data obtained by applying a linear anterior-posterior bandlimited pseudorandom disturbance to the base of support of human subjects. Model orders as well as model parameters were determined empirically. One advantage of this modeling procedure is the conciseness of the postural models, permitting easy statistical analysis of the data obtained under different dynamic conditions from many subjects. Model features, including pole and zero locations, from 6 normal subjects each tested on 5 consecutive days under 3 input amplitudes and eyes open and closed conditions are presented. The resulting transfer function models consist of only 1 or 2 poles near the integration position on the Z plane unit circle and 0 to 2 zeros. Locations of the poles indicate that the eyes closed responses are more oscillatory, less damped, and with higher gains than the eyes open responses. These transfer functions are similar to nonparametric ones of other authors. The noise model orders are also small. Their spectra are those of low pass systems. Also, the quantity and frequency range of the postural noise is positively related to the amplitude of platform motion as well as related to the presence or absence of vision.

Adult↗
PubMed1984

Protein diffusion coefficient measurements by laminar flow analysis: method and applications.

Laminar flow in an open tube leads to solute band spreading. This process is opposed by radial diffusion. The translational diffusion coefficient of a solute can be calculated from the band dispersion, tube length, and flow rate. No calibration is necessary. A simple apparatus was used to measure the diffusion coefficients of several small solutes and 18 proteins. Most results were within +/- 10% of literature values. Each determination required 7-90 min, depending on the magnitude of the diffusion coefficient. The amount of protein needed was approximately 25 micrograms. The diffusion coefficient data were useful for the estimation of molecular weights.

Chemical Phenomena↗
PubMed1984

Histocompatibility antigens (HLA-A,B,C) are not detectable in molar villous fluid.

Cell-free villous fluid from healthy and necrotic molar villi did not contain detectable soluble HLA Class I (HLA-A,B,C) antigens; therefore, HLA sensitization of the maternal host is probably not attributable to shedding of HLA antigens by viable or degenerating HLA-positive stromal cells. The method developed for this study, a combination of immunoprecipitation and Western blot techniques, employed specific antibodies for positive identification of the HLA heavy chain. The pathogenesis of complete molar pregnancy may be better understood through further study of the mechanisms of HLA sensitization of the maternal host and the host's response to these foreign antigens.

Female↗
PubMed1984

Antagonism of the effects of midazolam on phrenic nerve activity in the dog by Ro 15-1788 and Ro 15-3505.

Experiments were performed on 14 anaesthetized, artifically ventilated dogs, in which efferent activity in the phrenic nerve was recorded and blood-gas tensions, arterial pH and core temperature were controlled. Doses of midazolam between 0.2 mg kg-1 and 2 mg kg-1 abolished phrenic nerve activity for periods between 30 and 90 min. Ro 15-1788 in doses between 0.06 mg kg-1 and 1 mg kg-1 and Ro 15-3505 0.2-2 mg kg-1 reversed the effects of midazolam on phrenic nerve activity. Prior administration of these drugs either abolished or greatly inhibited the action of midazolam. When the preparations were observed for up to 2 h, there was no evidence of return of the action of midazolam, suggesting that both antagonists had a duration of action at least as long as that of midazolam.

Action Potentials↗
PubMed1984

Behavioral effects of diazepam and propranolol in patients with panic disorder and agoraphobia.

The effects of oral doses of diazepam (single dose of 10 mg and a median dose of 30 mg/day for 2 weeks) and propranolol (single dose of 80 mg and a median dose of 240 mg/day for 2 weeks) on psychological performance of patients with panic disorders and agoraphobia were investigated in a double-blind, randomized and crossover design. Both drugs impaired immediate free recall but the decrease was greater for diazepam than propranolol. Delayed free recall was also impaired but the two drugs did not differ. Patients tapped faster after propranolol than diazepam and they were more sedated after diazepam than propranolol. After 2 weeks of treatment, patients tested 5-8 h after the last dose of medication did not show any decrement of performance. These results are similar to those previously found in healthy subjects. Accumulation of drugs was not reflected in prolonged behavioral impairment.

Adult↗
PubMed1984

A comparison of panic disorder and generalized anxiety disorder.

Subjects from a family study who had panic disorder and generalized anxiety disorder were compared on the pattern of their symptoms, age and type of onset, personality characteristics, course of illness, and outcome. Subjects with generalized anxiety disorder were shown to have fewer autonomic symptoms and an earlier, more gradual onset. Their illness was also observed to have a more chronic course and a more favorable outcome, although these differences were not statistically significant. The validity of generalized anxiety disorder and panic disorder as discrete diagnostic entities is supported.

Adult↗
PubMed1984

Immunobiology of molar pregnancy and gestational trophoblastic tumors.

Because all the chromosomes in complete molar pregnancy are of paternal origin, complete moles are complete allografts (transplants). Complete moles may therefore be expected to induce a vigorous maternal host immunologic response. Further understanding of the relationships between the normal placenta, mole and choriocarcinoma may provide important insights into the basic mechanisms of teratogenesis and carcinogenesis.

Antibody Formation↗
PubMed1983

Immunoprecipitation of proteins from cell-free translations.

A typical procedure for immunoprecipitating a protein (abundance ca 0.5%) synthesized in the wheat germ cell-free system is summarized below. 1. Two microliters of 25% SDS are added to 48 microliters of translation reaction mixture, and the sample is heated to 100 degrees for 4 min. 2. Four volumes (i.e., 200 microliters) of dilution buffer at 4 degrees are added to the above sample. Dilution buffer is 1.25% Triton X-100, 190 mM NaCl, 60 mM Tris-HCl, pH 7.4, 6 mM EDTA, 10 units of Trasylol per milliliter. 3. Five microliters of appropriate antisera are added, and the sample is incubated for at least 12 hr at 4 degrees. 4. The sample is spun for 2 min in a microcentrifuge, and the supernatant is transferred to a fresh tube. 5. Thirty microliters of a 1 : 1 suspension of protein A-Sepharose CL-4B (15 microliters of packed beads) are added, and the sample is incubated with end-over-end mixing at room temperature for 2 hr. 6. The Sepharose beads are pelleted by a 10-sec centrifugation in the microcentrifuge, and the supernatant is aspirated. 7. The beads are washed four times in 1 ml, per wash, of 0.1% Triton X-100, 0.02% SDS, 150 mM NaCl, 50 mM Tris-HCl, pH 7.5, 5 mM EDTA, 10 units of Trasylol per milliliter at room temperature with vortexing at each wash. 8. The beads are given a final wash with the above solution not containing detergent, and the supernatant is aspirated as completely as possible with a drawn-out Pasteur pipette. 9. Forty microliters of SDS-gel electrophoresis sample buffer containing 50 mM DTT are added to the beads, and the sample is heated for 4 min in a boiling water bath. 10. Free--SH groups are blocked by adding 10 microliters of 1.0 M iodoacetamide in sample buffer and incubating for 45 min at 37 degrees. 11. The beads are centrifuged out, and the supernatant is applied to an SDS-polyacrylamide slab gel.

Animals↗
PubMed1983

Biosynthesis of acetylcholine receptor in vitro.

Torpedo acetylcholine receptor is accessible to analysis by cell-free protein synthesis, like other membrane proteins studied previously. The factors deserving particular attention in this system are the small amounts of messenger RNA contained in electroplax tissue, the inherent complexity of an oligomeric membrane protein (necessitating the use of subunit-specific antibodies), the anomalous electrophoretic behavior of the primary translation products (attributable in part to the high--SH content of sAChRs), and the multiple glycosylated forms that appear upon processing by microsomal membranes. Although not all these complexities can be satisfactorily explained, they have been empirically characterized and can be well controlled if the appropriate procedures are followed.

Animals↗
PubMed1983

Identification of homo-oligomers as potential intermediates in acetylcholine receptor subunit assembly.

We have examined the sedimentation behavior, on sucrose density gradients, of acetylcholine receptor (AcChoR) subunits synthesized in vitro and integrated into heterologous rough microsomal membranes. In media containing nondenaturing detergents such as Triton X-100 or deoxycholate, the subunits appear to self-associate although, as previously reported, no heterologous interactions were detected. The sedimentation profiles assume a broad distribution in the region of 7-13 S. However, the peak fractions occupy the same region of the gradient as does native AcChoR, run in parallel. Such large homo-oligomers were not observed for another membrane protein, opsin, studied in the same way. This indicated that the associations are indeed between the AcChoR subunits and not simply between all newly synthesized membrane proteins. The homologous associations are interpreted to suggest a mechanism for maintaining the ionophore surfaces of the subunits in an energetically preferred, but metastable, configuration during the lengthy period of post-translational assembly.

Animals↗
PubMed1983

Mechanisms of integration of de novo-synthesized polypeptides into membranes: signal-recognition particle is required for integration into microsomal membranes of calcium ATPase and of lens MP26 but not of cytochrome b5.

We have investigated the in vitro integration into dog pancreas microsomal membranes of three integral membrane proteins that were synthesized de novo in a wheat germ cell-free translation system: calcium ATPase of rabbit sarcoplasmic reticulum, MP26 of bovine lens fiber plasma membrane, and rat liver cytochrome b5. Biosynthetically these proteins show a common feature in that they are synthesized without a transient NH2-terminal signal sequence. Two of these proteins, ATPase and MP26, were shown to require the recently discovered signal-recognition particle (SRP) [Walter, P. & Blobel, G. (1982) Nature (London) 299, 691-698] for integration. By this criterion, therefore, they each contain at least one uncleaved signal sequence. Surprisingly, however, the uncleaved signal sequence(s) of these two proteins did not induce the characteristic SRP-mediated translation arrest that was previously shown for a cleaved signal sequence. Unlike ATPase and MP26, cytochrome b5 did not require SRP for integration into microsomal membrane. Thus, the distinction between an "insertion" sequence (specifying unassisted and opportunistic integration into any exposed membrane) and a "signal" sequence (directing integration into a specific membrane by a receptor-mediated mechanism) is a valid one. By assaying for SRP dependence, the two mechanisms of integration can now be experimentally distinguished.

Animals↗