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Biomedical subjects

B M Richards

Publications and source records attributed to B M Richards.

At least 19 recordsLinked to original sources
PubMed1992

Symmetry, flexibility and permeability in the structure of yeast retrotransposon virus-like particles.

The virus-like particles (VLPs) of the yeast retrotransposon Ty are genetically, structurally and functionally analogous to retroviral nucleocapsids or cores. Like retroviral cores Ty-VLPs package and possibly promote the enzyme activities for reverse transcription and integration, as well as encapsulating the RNA that is the intermediate in retrotransposition. Here we show that Ty-VLPs assemble into symmetrical structures across a broad distribution of particle sizes. This spread of sizes violates the principle of quasi-equivalent packing. In addition, RNase accessibility experiments suggest that these particles form an open structure that does not protect the encapsulated RNA. These features distinguish Ty-VLPs from typical spherical viral capsids in both structure and function.

DNA Transposable Elements↗
PubMed1992

Asthma severity: a factor analytic investigation.

PURPOSE: Reviewers of the asthma research literature have called for improved questionnaires and other measures, particularly for assessing the severity of asthma. To help meet this need, standard multivariate and psychometric techniques were used with data from asthma patients to develop and evaluate a series of scaled questions. Since there is no "gold standard" for assessing asthma severity, we hope this analysis will help improve our ability to more precisely define these important parameters. PATIENTS AND METHODS: Data were collected through interviews and review of clinic records for 199 adult patients with asthma from a university clinic population. For evaluating the severity of asthma, eight scales assessed asthma duration, the incidence of asthma symptoms, the extent to which asthma is an inconvenience to patients, the incidence of respiratory diseases, medication regimens, medication side effects, and health care utilization. Forced expiratory volume in 1 second as a percentage of predicted normal was included as an objective measure of pulmonary function. A physician rating scale assessed the severity of the underlying disease, not the severity of a particular episode, as either (1) mild (infrequent attacks with interim symptomatic treatment), (2) moderate (more frequent attacks with continuous daily treatment), and (3) severe (continuous symptom with continuous multiple drug regimen, including some systemic steroids). RESULTS: In the current analysis of data from adult asthma patients, the scales correlated positively with a physician judgment scale. Factor analysis with an oblique rotation yielded three factors that provided a concise summary of asthma severity. We have named the factors (A) Symptom Intensity, (B) Airflow Impairment, and (C) Management Intensity. CONCLUSION: Asthma severity appears to be multidimensional rather than unidimensional, including at least three components. The physician rating scale, in combination with measures of the three identified factors, could easily be included in other asthma research protocols to provide a standard, brief assessment of asthma severity and might thus promote greater comparability among studies.

Adult↗
PubMed1982

The molecular cloning and characterisation of cDNA coding for the alpha subunit of the acetylcholine receptor.

A rare cDNA coding for most of the alpha subunit of the Torpedo nicotinic acetylcholine receptor has been cloned into bacteria. The use of a mismatched oligonucleotide primer of reverse transcriptase facilitated the design of an efficient, specific probe for recombinant bacteria. DNA sequence analysis has enabled the elucidation of a large part of the polypeptide primary sequence which is discussed in relation to its acetylcholine binding activity and the location of receptor within the plasma membrane. When used as a radioactive probe, the cloned cDNA binds specifically to a single Torpedo mRNA species of about 2350 nucleotides in length but fails to show significant cross-hybridisation with alpha subunit mRNA extracted from cat muscle.

Amino Acid Sequence↗
PubMed1978

Treatment of HBsAg-positive chronic active hepatitis with human fibroblast interferon.

Two patients with HBsAg positive chronic active hepatitis have been treated with human fibroblast interferon 10(7) units daily for two weeks. Before treatment, both patients had high levels of hepatitis B surface antigen, core antibody, and DNA-binding antibody in the blood and one patient had a fourfold rise in serum AST. During treatment there was a striking fall in the core antibody titre and also in the DNA-binding antibody, which has been maintained for several months subsequently; in one patient the initially high AST level fell to normal. No significant adverse effects occurred, and these observations should encourage further trials of fibroblasts interferon in hepatitis B.

Adult↗
PubMed1977

Structural investigations of chromatin core protein by nuclear magnetic resonance.

A complex derived from chromatin containing one molecule of each of histones H2A, H2B, H3, and H4, termed core protein, was studied by 13C and 1H nuclear magnetic resonance. 13C line widths, when analyzed and compared with those of native and thermally unfolded representative globular proteins, showed that regions of the core protein possess considerable mobility. Studies of Calpha and Cbeta line widths, and Calpha spin-spin relaxation times, show that this mobility arises from sections of random-coil polypeptide. It is argued that these regions are N-terminal "tails", attached to C-terminal globular polypeptides. The 270-MHz 1H nuclear magnetic resonance spectrum shows numerous ring current shifted resonances, indicating that the C-terminal globular domain has a precise tertiary structure. The globular domain most likely forms the histone "core" of the chromatin monomer particle, whilst the basic tails probably wind around the grooves of the double helix, enabling the basic side chains to interact with the DNA phosphate groups. Some biological implications of this model are considered.

Animals↗
PubMed1977

Structural studies of encephalomyocarditis virus RNA both in situ and in free solution.

The secondary structure of encephalomyocarditis (EMC) virus RNA has been studied in situ and in free solution by absorbance-temperature relationships and by circular dichroism (CD). Extracted EMC virus RNA melts reversibly and has a hypochromicity of about 20%; analysis of CD spectra and formaldehyde treatment suggests that approx. 60% of the nucleotides are involved in base-pairing at 25 degrees C. It is shown that the RNA within the virus particle is less structured than when it exists in free solution, being partially stabilized by capsid protein against melting until the virion is disrupted to release the intact RNA. Upon clarification to remove denatured capsid protein, the released RNA gives a melting profile identical with that of phenol-extracted virus RNA. The results suggest that the intact structure of the virus is dependent upon intimate non-covalent bonds between RNA and protein together with hydrophobic bonds between the protein subunits.

Circular Dichroism↗
PubMed1975

An investigation of the conformational and self-aggregational processes of histones using 1H and 13C nuclear magnetic resonance.

Histone self-aggregation processes have been studied by 13C and 1H nuclear magnetic resonance (NMR) as a function of ionic strength and protein concentration. Thus has led to a model involving apolar aggregation between structured regions of these molecules. This analysis supports the validity of the acquistion of conformational data on histones by the simulation of 13C NMR spectra at high concentration. Solution conformations for histones F2B and F3 are presented.

Animals↗
PubMed1975

The total containment of a batch-type zonal centrifuge.

A batch-type zonal centrifuge has been modified and totally contained for use with biologically hazardous materials. A sealed cabinet encloses the centrifuge and the ancilliary equipment. It is operated with a flow of filtered air when the zonal system is on, decontaminated with ethylene oxide, and maintained at a negative pressure throughout. The centrifuge subsystems can be drained, flushed, and decontaminated with ethylene oxide before an engineer services the machine. The sample handling system within the cabinet is remotely controlled.

Centrifugation, Zonal↗
PubMed1975

Low-angle neutron scattering from chromatin subunit particles.

Monomer chromatin particles containing 140 base pairs of DNA and eight histone molecules have been studied by neutron scattering. From measurements in various H2O/D2O mixtures, radii of gyration and the average scattering density of the particle were determined. The radius of gyration under conditions when scattering from the DNA dominates is 50A, and when scattering from the protein dominates, 30A. Consequently the core of the particle is largely occupied by the histones while the outer shell consists of DNA together with some of the histone.

Animals↗