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Biomedical subjects

B R Jennings

Publications and source records attributed to B R Jennings.

At least 37 records · Page 2Linked to original sources
PubMed1982

Beta-lactamase testing of staphylococci in a commercial broth microdilution minimum inhibitory concentration system.

Beta-Lactamase testing of clinical isolates of staphylococci may be performed in commercial broth microdilution minimum inhibitory concentration plates, using a chromogenic cephalosporin reagent directly in a well containing a noninhibitory concentration of a semisynthetic penicillin which serves as an inducer. A total of 115 staphylococcal isolates tested in 0.25 to 0.50 microgram of methicillin per ml in Mueller-Hinton broth showed 100% correlation with beta-lactamase tests performed on Mueller-Hinton agar, using 1-microgram oxacillin disk as an inducer.

Cephalosporins↗
PubMed1978

Characterization of proteoglycan and the proteoglycan--hyaluronic acid complex by electric birefringence.

An electric field causes partial alignment of macromolecules in a dilute solution. The accompanying changes in the solution birefringence offer a sensitive and quick means of monitoring the rates of particle orientation and hence the size of the solute molecules. Such measurements are reported for dilute solutions of proteoglycans in the absence and presence of added hyaluronic acid. The proteoglycan molecules are shown to be some 580 nm long. In the presence of hyaluronic acid they form aggregates that appear to be consistent with the model previously proposed in which the proteoglycans attach radially to the extended hyaluronic acid chain. The electric-birefringence relaxation rates indicate aggregates of similar length to that of the extended hyaluronic acid chain, with the proteoglycans spaced on average at 29nm intervals. A proteoglycan sample the cystine residues of which had been reduced and alkylated showed no evidence of aggregation with hyaluronic acid up to the concentrations of the acid corresponding to 1% of the total uronic acid content. The electric-birefringence method is shown to have a large potential in the study of associating polysaccharide solutions.

Alkylation↗
PubMed1977

The effect of antibiotics on the electrical polarisability of aqueous suspensions of bacteria.

The orientation of washed Escherichia coli bacteria in suspension induced by applied a.c. electric fields has been monitored by observing the accompanying changes in the intensity of light scattered by the suspension. The data enable the anisotropy of electrical polarisability deltaalpha to be determined. Changes in deltaalpha due to the addition of various antibiotics to the suspension have been measured as a function of both the antibiotic concentration and the temperature of the suspension. The results are taken to indicate that there is an accumulation of the antibiotic molecules at the bacterial surface.

Adsorption↗
PubMed1977

T-lymphocytes and survival of head and neck squamous cell carcinoma.

The thymus-dependent lymphocytes (T cells) were enumerated in the peripheral circulation of 38 patients with histologically demonstrated squamous cell carcinoma of the head and neck. We have previously shown that this "total" T-cell count correlates well with degree of tumor involvement. A lower percentage of T cells were shown in patients with more advanced malignant neoplasms. Here we present follow-up data on these patients to evaluate the efficiency of the T-cell test in determining survival prognoses. We found no evidence that results of this test can extend prognostic abilities above those based on clinical staging. The survival data from six patients treated with a chemoimmunotherapy regimen of BCG vaccine, methotrexate sodium, and isoniazid did not demonstrate an increased survival time compared to patients at similar clinical stages who were treated by conventional use of surgery and irradiation.

Adult↗
PubMed1976

T-cell rosette test in squamous cell carcinoma of the head and neck.

The percentage of total T-lymphocytes was measured in 38 patients with histologically diagnosed squamous cell carcinoma of the head and neck. This measure of cellular immunity, which appears to be important in tumor-cell destruction, is demonstrably lowered in advanced stages of this disease. With the use of this test, the effect of a combined chemoimmunotherapeutic regimen consisting of methotrexate sodium, isoniazid, and BCG vaccine was sutdied. In this small series, no decrease of the T-cell count following treatment by methotrexate was demonstrated, except when a high dosage followed by leucovorin calcium was used. The BCG vaccine appeared to enhance T-cell counts, and one patient who was treated with cryosurgery had a dramatic increase in circulating T-lymphocytes. The T-cell test may be of clinical importance in the development of treatment sequences that provide maximum reduction of tumor cell mass while preserving host T cells.

Adult↗
PubMed1976

An electro-optic study of the effect of certain aminoglycoside antibiotics on the electrical polarizability of sensitive, dependent and resistant strains of Escherichia coli.

A study has been made of the effect of certain aminoglycoside antibiotics on the electrical properties of the surfaces of one sensitive, two resistant and one dependent form of E. coli K-12. The method employed was to observe the change in scattered light produced when the bacteria in suspension are orientated by an applied a. c. electric field. The effect of the antibiotics has been analysed in terms of drug accumulation at the bacterial surface. Differences have been noted in the responses of the sensitive form to different aminoglycosides and an attempt has been made to correlate these differences with mimimum inhibitory concentrations. Differences have also been noted in the response of certain resistant and dependent forms of E. coli to streptomycin.

Anti-Bacterial Agents↗
PubMed1975

The effect of neomycin and streptomycin on the electrical polarisability of aqueous suspensions of Escherichia coli.

Aqueous suspensions of bacteria scatter light strongly. In addition, the bacteria exhibit strong induced dipole moments in an electric field. In this note we report how, by measuring the intensity of the scattered light, the electric polarisability (alpha) of Escherichia coli could be monitored as small quantities of antibiotics were added to the suspensions. The effect of the presence of quite small quantities of antibiotic on the electrical polarisability, which gave rise to the induced dipole, was dramatic. From the hypothesis that alpha had its origins in the bacteria-solvent interface, a theory is presented which adequately accounts for both alpha and its changes in the presence of these antibiotics. The study is taken to suggest that the antibiotic molecules were adsorbed on to the bacterial surface thereby reducing the surface charge. This in turn reduces the number of counterions and the apparent induced dipole moment. Because the electric-field scattering method is both quick and sensitive to changes in alpha, it may prove a valuable method for the study of antibiotic action on cell and microorganism surfaces.

Escherichia coli↗
PubMed1975

Infrared scattering: a method for evaluating the mass and size of bacteria.

In the realm of biophysics and biochemistry, light scattering is used extensively to evaluate the molecular weight and size of macromolecules and particles in suspension. Bacteria scatter strongly but are too large for the conventional procedures. By extending the wavelength lambda of the incident radiation into the infrared, we show that the effective size of the bacteria (relative to lambda) is reduced, and the usual Zimm plot measurements and procedure can be applied to evaluate the molecular weight and size. Details of the apparatus, its alignment, calibration and use are given along with data for aqueous suspensions of the three species Serratia marcescens, Escherichia coli and Thiobacillus ferrooxidans. The method has the advantages of being suitable for rod-like or ellipsoid-like bacteria as well as spheres, for polydisperse samples and for monitoring the effects of environment, antibodies and chemical therapeutic agents on the bacteria.

Escherichia coli↗
PubMed1974

Protein patterns during regeneration and wound healing in the adult newt: a comparative study using gel electrophoresis.

Gel electrophoresis was performed on tissue extracts made from regenerating tails, limbs and deep razor blade wounds to the back of adult newts. In general, 3 types of changes appeared in posttrauma gels: decrease in density of some bands, increase in others, and "new" bands. Patterns were very similar in limb and tail regeneration suggesting that the two processes do not differ significantly with regard to alterations in the major soluble proteins. The patterns further indicated that certain wound-healing events also occur in regeneration. Some of these events are prolonged in the latter, while others are long-lasting in both. The results also suggest the existence of a regeneration-specific protein.

Amputation, Surgical↗