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Biomedical subjects

S E Phillips

Publications and source records attributed to S E Phillips.

98 records · Page 6Linked to original sources
PubMed1976

Modification of the Minitek Miniaturized Differentiation System for characterization of anaerobic bacteria.

The Minitek Miniaturized System (BBL) was modified for characterization of anaerobic bacteria. The modified system and the conventional Center for Disease Control method were used to test a variety of anaerobic bacteria, and results were compared. Tests performed by both techniques were indole and H2S production, esculin hydrolysis, nitrate reduction, and fermentation of glucose, mannitol, lactose, sucrose, maltose, salicin, glycerol, xylose, arabinose, mannose, rhamnose, and trehalose. The manufacturer's recommended procedure for the Minitek system was modified by using a new suspension medium (Lombard-Dowell broth) and an inoculum equivalent to the density of a McFarland no. 5 nephelometer standard. The Minitek results, recorded after 48 h, agreed satisfactorily with the conventional test results, usually recorded after 5 to 7 days of incubation. In the examination of 80 strains representing 22 different species or subspecies of anaerobic bacteria, with 16 biochemical tests performed in triplicate, 93.8% of the Minitek test results agreed with those of the corresponding conventional tests. Only tests for indole, H2S, and nitrate reduction gave less than 90% agreement. It was concluded that the modified Minitek system is a suitable substitute for the more expensive and time-consuming conventional procedure for determining carbohydrate fermentation and esculin hydrolysis by anaerobes. This system, when used in conjunction with other tests, can effectively aid in the definitive identification of commonly isolated anaerobes.

Anaerobiosis↗
PubMedDate not supplied

A proposal for the reliable culture of Borrelia burgdorferi from patients with chronic Lyme disease, even from those previously aggressively treated.

Since culture of Borrelia burgdorferi from patients with chronic Lyme disease has been an extraordinarily rare event, clarification of the nature of the illness and proving its etiology as infectious have been difficult. A method for reliably and reproducibly culturing B. burgdorferi from the blood of patients with chronic Lyme disease was therefore sought by making a controlled blood culture trial studying 47 patients with chronic Lyme disease. All had relapsed after long-term oral and intravenous antibiotics. 23 patients with other chronic illness formed the control group. Positive cultures were confirmed by fluorescent antibody immuno-electron microscopy using monoclonal antibody directed against Osp A, and Osp A PCR. 43/47 patients (91%) cultured positive. 23/23 controls (100%) cultured negative. Although persistent infection has been, to date, strongly suggested in chronic Lyme disease by positive PCR and antigen capture, there are major problems with these tests. This new method for culturing B. burgdorferi from patients with chronic Lyme disease certainly defines the nature of the illness and establishes that it is of chronic infectious etiology. This discovery should help to reestablish the gold standard in laboratory diagnosis of Lyme disease.

Bacteremia↗
PubMedDate not supplied

X-ray diffraction studies of an anti-azophenylarsonate antibody and of an antigen-antibody complex.

X-ray crystallographic studies of the Fab fragments of two murine monoclonal antibodies of predefined specificity are under way. Diffracted X-ray intensities of the crystalline native Fab fragment of an anti-azophenylarsonate antibody and of three heavy atom derivatives have been measured to a resolution of 3.5 A. A preliminary 6-A resolution electron density map has been obtained. The 6-A resolution structure of an antigen-antibody (hen lysozyme-Fab) complex has been determined. There are close contacts between the antigen and the antibody over a large contact area, about 20 X 25 A. At least two segments of the polypeptide chain of lysozyme, of about 10 amino acids each (positions 19-27 and 116-129), are involved in the contacts, as well as all six complementarity-determining regions of the antibody. No gross conformational changes are observed in the antigen at this resolution, although there are some smaller local changes in areas in contact with the antibody and elsewhere. The effects of amino acid substitutions on antigen recognition by the monoclonal anti-hen lysozyme antibody were investigated using different, closely related lysozymes. These effects can be readily explained in terms of the three-dimensional model presented here. A 3.5-A resolution electron density map has been calculated and is currently under study.

Animals↗
PubMedDate not supplied

Three-dimensional structure of an antigen-antibody complex at 6 A resolution.

Present understanding of the three-dimensional structure of antibody combining sites is based on X-ray diffraction studies of myeloma immunoglobulins. The structures of the antigen-binding fragment (Fab) complexes of two of these immunoglobulins with small ligands have also been determined. However, there is no crystallographic information concerning the interactions of an antibody with an antigen, nor do we know the precise structure of antigenic determinants on protein molecules. We now report the first structure determination of an antigen-antibody complex at 6 A resolution. The structure of the complex between hen egg-white lysozyme and the Fab of a monoclonal anti-lysozyme antibody (D1.3) shows that the combining site of antibodies is not merely a cleft delineated by the complementarity-determining regions of the variable regions of the light and heavy chains, but is a larger area extending beyond it. A correspondingly large area of the antigen makes close contacts with the antibody, in agreement with the notion of a 'topographical' rather than 'sequential' antigenic determinant. The structural basis of cross-reactivities of an antibody with heterologous antigens and the effect of a single amino acid substitution on antigenic specificity can thus be visualized in the structural model presented here.

Amino Acid Sequence↗
PubMedDate not supplied

Referral-to-placement ratio: a finding in need of reassessment?

Previous research has reported that the number of evaluated children placed in special education is as high as three out of four. The purpose of the present study is to reassess, extend, and update referral-to-placement research. Subjects consisted of 236 predominantly white children referred for special education evaluation from 12 suburban and rural school districts. Of the 236 pupils referred, 128 were diagnosed as learning disabled (LD) by a multidisciplinary team (MDT). The 128 students identified as eligible for services for students with LD had a mean IQ of 96.43 and a mean age of 10.2. The majority of the subjects were male (70%). The results suggest that the number of students referred who are actually placed is lower (approximately one out of two) than previously reported. It is concluded that further research is needed to verify the current referral-to-placement ratio and to explore the factors influencing this ratio.

Child↗