Mary H. Smith: advocate for the underserved. Interview by Karna Bramble.
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Ill-Housed Persons↗
Biomedical subjects
M H Smith
Publications and source records attributed to M H Smith.
Sources of error associated with sample collection and preparation of nucleated blood cells for flow cytometric analysis.
Analysis of cellular DNA content by flow cytometry has been used to detect genetic changes associated with exposure to environmental contaminants. In lower vertebrates, nucleated red blood cells can be collected for analysis without harm to the animal. Because erythrocytes sampled from an individual should have identical amounts of DNA, the coefficient of variation (CV) around the G0/G1 peak should be small. Increases in CV can indicate genetic aberrations, but may also be caused by sample handling and preparation or problems with instrumentation. To increase confidence in associating increases in CV with external causes, artifactual changes in CV due to sample treatment and instrument parameters should be identified and minimized. We assessed the effects of various sampling and handling protocols on the CV of nucleated blood cells collected from largemouth bass (Micropterus salmoides). We also compared the distribution of cells among the G0/G1, S, and G2/M phases of the cell cycle to see whether these were affected by sampling or treatment protocols. Groups of 7 fish were bled on 7 consecutive days, and blood from each fish was analyzed by flow cytometry when freshly collected, and after freezing for 1 hour or 10 days. The same fish were bled again over a consecutive 7-day period, and the experiment was repeated. CV and cell cycle distribution were not affected by our freezing protocol. Repeat sampling from the same individual did not affect CV, but altered the distribution of cells in the cell cycle, suggesting increased hemopoiesis in response to blood sampling.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Cleavage of LexA repressor.
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Bacterial Proteins↗
Peptide sequences binding to MHC class I proteins.
Motifs for peptides which bind specifically to the human class I major histocompatibility complex molecules HLA-A2 and B7 were determined by sequence analysis of class I-bound peptides selected from a random synthetic library of nonamers. Thirteen individual peptides were sequenced for HLA-A2, twelve individual and nine pooled peptides were sequenced for HLA-B7. Analysis of sequence alignment implicated four peptide positions in potential contact with the class I HLA-A2 molecule and three positions for the HLA-B7 molecule. The results demonstrate that a synthetic peptide library can be used to identify allele-specific motifs for class I molecules, providing information comparable to the results obtained from sequencing endogenous peptides. This method utilizes denatured class I heavy chains, and similar results were obtained using a class I protein purified from mammalian cells or by expression in Escherichia coli. This method has the potential to detect peptides which may not be generated physiologically, but due to their binding properties, may be valuable to predict or engineer immunomodulatory T cell epitopes.
Amino Acid Sequence↗
Comparison of reactors for oxygen-sensitive reactions: reductive dechlorination of chlorophenols by vitamin b(12s).
Serum bottles are frequently used for studies of reductive dechlorination by vitamin B(12), but reducing conditions can be maintained only for several days. This time period is inadequate for evaluating the reductive dechlorination of some slow-reacting aromatic compounds. Sealed glass ampoules maintain reducing conditions for many months, but this method has the disadvantage of disallowing subsampling of the reaction mixture. A glass serum tube was modified for these experiments which not only maintained anoxic conditions for several days but also allowed subsamples to be removed during experiments. The modification was a restriction placed in the middle of the tube by heating in a flame, creating two chambers separated by a narrow neck. The lower chamber contained the oxygen-sensitive reaction mixture. The upper chamber, sealed with a septum and screw cap, was purged with purified nitrogen or argon introduced and vented through fused silica capillaries. Reductive dechlorination of chlorophenols by vitamin B(12) reduced with Ti(III) citrate was monitored in all three reactor types. Sealed ampoules maintained reducing conditions for up to 12 months. The two-chambered reactor maintained reducing conditions longer than the serum vials when frequent samples were taken.
Journal Article↗
Regiospecificity of chlorophenol reductive dechlorination by vitamin b(12s).
Vitamin B(12), reduced by titanium (III) citrate to vitamin B(12s), catalyzes the reductive dechlorination of chlorophenols. Reductive dechlorination of pentachlorophenol and of all tetrachlorophenol and trichlorophenol isomers was observed. Reaction of various chlorophenols with vitamin B(12) favored reductive dechlorination at positions adjacent to another chlorinated carbon, but chlorines ortho to the hydroxyl group of a phenol were particularly resistant to reductive dechlorination, even if they were also ortho to a chlorine. This resulted in a reductive dechlorination pattern favoring removal of para and meta chlorines, which differs substantially from the pattern exhibited by anaerobic microbial consortia.
Journal Article↗
Health care for the homeless: a family medicine perspective.
Many factors contribute to the health problems of homeless persons, including exposure to adverse weather, trauma and crime, overcrowding in shelters, unusual sleeping accommodations, poor hygiene and nutritional status, alcoholism, drug abuse and psychiatric illness. It is common for homeless adults to have skin ailments, respiratory infections, traumatic injuries and chronic gastrointestinal, vascular, dental and neurologic disorders. Homeless children may have respiratory, ear and skin diseases, as well as special problems, including failure to thrive, developmental delay, neglect and abuse. Important questions to ask during history-taking include questions about sleeping conditions, sources of food, past psychiatric problems and substance abuse, and sources of social support. Special attention should be given to examination of the skin, teeth and feet. Supplemental food, immunizations, psychologic counseling and social service referrals should be considered for homeless pediatric patients.
Adult↗
In vitro analysis of mutant LexA proteins with an increased rate of specific cleavage.
Specific cleavage of LexA repressor plays a crucial role in the SOS response of Escherichia coli. In vivo, cleavage requires an activated form of RecA protein. However, previous work has shown that the mechanism of cleavage is unusual, in that the chemistry of cleavage is probably carried out by residues in the repressor, and not those in RecA; RecA appears to facilitate this reaction, acting as a coprotease. We recently described a new type of lexA mutation, a class termed lexA (IndS) and here called IndS, that confers an increased rate of in vivo cleavage. Here, we have characterized the in vitro cleavage of these IndS mutant proteins, and of several double mutant proteins containing an IndS mutation and one of several mutations, termed Ind-, that decrease the rate of cleavage. We found, first, that the autodigestion reaction for the IndS mutant proteins had a higher maximum rate and a lower apparent pKa than wild-type LexA. Second, the IndS mutations had little or no effect on the rate of RecA-mediated cleavage, measured at low protein concentrations, implying that the value of Kcat/Km was unaffected. Third, the rate of autodigestion for the double-mutant proteins, relative to wild-type, was about that rate predicted from the product of the effects of the two single mutations. Finally, by contrast, these proteins displayed the same rate of RecA-mediated cleavage as did the single Ind- mutant protein. We interpret these data to mean that the IndS mutations mimic to some extent the effect of RecA on cleavage, perhaps by favoring a conformational change in LexA. We present and analyze a model that embodies these conclusions.
Bacterial Proteins↗
NP shares experiences in ARNP Program.
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Clinical Competence↗
Tuberculosis in children in 1992.
In children, as in adults, tuberculosis is much commoner among minority population groups, in Louisiana particularly among blacks. Since 1986 tuberculosis in some states has increased notably; in Louisiana the increase is only now, in 1992, becoming apparent. Eighteen new cases in children under 20 were reported in 1991. Diagnosis in children still depends largely on history of contact and on the Mantoux tuberculin test. Treatment has changed markedly to a more intensive 6 month course including three or four drugs. Preventive treatment of tuberculin positive children is particularly emphasized because it will play an important role in achieving the stated public health goal of elimination of tuberculosis by the year 2010. With the increasing number of children exposed to tuberculosis, the increasing number of HIV-positive children at risk, and the rising number of multiresistant tubercle bacilli, vaccination with BCG must be considered.
Acquired Immunodeficiency Syndrome↗
The decline in geriatric long stay beds: who remains?
A day census of all long-term hospital patients in the Canterbury geriatric service area was carried out in 1984 (when there were 127 beds) and repeated in 1989 (when there were 66 beds). The patients in the 1989 census were more confused and physically more dependent than those in 1984. Comparison with residents in local residential and nursing homes in 1987 shows that a higher proportion of long-term hospital patients had severe mental and physical disability. There is a hard core of patients who are difficult to place outside hospital. This has predictable resource implications and in Canterbury such patients will continue to occupy National Health Service beds as there are no practicable alternatives.
Activities of Daily Living↗
Mutant LexA proteins with an increased rate of in vivo cleavage.
LexA repressor of Escherichia coli is inactivated by a specific cleavage reaction that requires activated RecA protein in vivo. This cleavage reaction can proceed in vitro in the presence of activated RecA or as an intramolecular RecA-independent reaction, termed autodigestion, that is stimulated by alkaline pH. Here we describe a set of LexA mutant proteins that undergo a greatly increased rate of specific cleavage in vivo, compared with wild-type LexA. Efficient in vivo cleavage of these mutant proteins also took place without RecA. Several lines of evidence suggest that cleavage occurred via a mechanism similar to autodigestion. These mutations changed Gln-92, which lies near the cleavage site, to tyrosine, phenylalanine, or tryptophan. The latter mutation increased the rate of cleavage approximately 500-fold. These findings imply that the rate of wild-type LexA cleavage has been optimized during evolution to make the SOS system properly responsive to DNA-damaging treatments. Availability of these mutants will aid in the understanding of rate-limiting steps in intramolecular reactions.
Amino Acid Sequence↗
Molecular characterization of biologically diverse envelope variants of human immunodeficiency virus type 1 derived from an individual.
The envelope genes of six viruses derived from a single sampling from an individual chronically infected with human immunodeficiency virus type 1 (RJS-4) have been analyzed. Here we present the nucleotide and predicted amino acid sequences of these variants and show a correlation between biological properties and disturbance of the envelope reading frame.
Acquired Immunodeficiency Syndrome↗
A computer program for estimating imprecision characteristics of immunoassays.
A reliable numerical algorithm is described, together with a computer program written in FORTRAN IV and FORTRAN 77, for estimating a three-parameter variance function by approximate conditional likelihood. The function is sufficiently flexible to provide for a several thousand-fold relative change in variance and appears to be a good model for the severely heteroscedastic results obtained from immunoassays. The computer program is primarily intended for summarizing imprecision characteristics of immunoassays in the form of imprecision profiles, but the estimated variance functions have additional application whenever further parametric analysis of immunoassay results is undertaken (e.g., as a weighting function when immunoassay results are used in a least-squares regression analysis). The flexibility of the function implies useful application in any area where heteroscedasticity is particularly severe.
Algorithms↗
The conformational flexibility of class I H-2 molecules as revealed by anti-peptide antibodies specific for intracytoplasmic determinants: differential reactivity of beta 2-microglobulin "bound" and "free" H-2Kb heavy chains.
Immunoprecipitation experiments using anti-peptide antisera prepared against exon 6, exon 7 and exon 8-encoded intracytoplasmic regions of the H-2Kb gene product indicated that approximately 1/3 of the H-2Kb heavy chains in a cell surface-labelled glycoprotein fraction from EL-4 cells, or H-2b spleen cells, is not associated with beta 2-microglobulin (beta 2-m). This population of "free" H-2Kb heavy chains failed to react with alloantisera or monoclonal antibodies specific for conventional H-2Kb serological determinants, suggesting that significant conformational alterations were induced in the extracellular domains upon dissociation of beta 2-m. In addition, although antibodies to intracytoplasmic peptide 8 were able to react with both "free" and beta 2-m "bound" heavy chains, the determinants seen by anti-peptide 6 and anti-peptide 7 were only recognized in the "free" heavy chain. These data suggest that the conformational perturbation of the extracellular domains induced by beta 2-m dissociation can be "transmitted" to the intracytoplasmic region of the heavy chain. These results indicate the potential for a class I heavy chain-mediated transmembrane signalling event, and suggest that the "free" class I heavy chain might have a role to play in the major histocompatibility complex (MHC)-restricted presentation of T-cell determinants to cytotoxic T-lymphocytes.
Animals↗
Health, homelessness, and poverty. A study of clinic users.
When seeking medical care, homeless persons often turn to health centers that were designed to treat the poor who have homes. To provide for effective medical care, personnel in such facilities need to know how the health care needs of the homeless are different from those of other clinic users. To compare the physical health of these two groups, we conducted a health survey and screening physical examination of 464 patients who attended the general adult and homeless clinic sessions of one of the main neighborhood health centers in Los Angeles County, California. As compared with the poor who have homes, homeless persons were more likely to have dermatological problems (32% vs 21%), functional limitations (median, 2 vs 0 per person), seizures (14% vs 6%), chronic obstructive pulmonary disease (21% vs 12%), social isolation, serious vision problems (22% vs 12%), foot pain, and grossly decayed teeth (median, 1 vs 0 per person). We conclude that to care more optimally for homeless adults, health centers must pay attention to their functional disabilities, substance abuse, skin abnormalities, vision impairment, dental problems, and foot problems.
Adult↗
Effect on a geriatric service of opening a 25-bed ward on the district general hospital site: an audit.
Notes and discharge summaries of 2,560 patients were analysed in a pre-planned study to determine how the establishment of a 25-bed assessment ward on the district general hospital (DGH) site affected the work of a geriatric unit that had previously had no DGH beds. Throughput, changes in referrals and practice, and changes in outcome were measured using a computerised programme which examined the work of the unit for a year before and a year after the opening of the assessment ward. There were no changes in overall bed numbers or staffing, so changes were likely to be the direct result of establishing the DGH beds. The second year of the study showed a 33% increased throughput, with increased referrals from the accident and emergency department and evidence of more active investigation and treatment and a tendency towards a shorter length of stay. There was an increased number of transfers from all departments to the geriatric department for rehabilitation and a shortened time interval to transfer. Admissions to the general medical unit for patients aged 65-74 and 75+ did not change.
England↗
Use and abuse of imprecision profiles: some pitfalls illustrated by computing and plotting confidence intervals.
Published estimates of the imprecision characteristics of immunoassays are often based on quantities of data that seem to be inadequate. The increasing use of imprecision profiles has not necessarily improved the situation. We describe and illustrate a method of computing 95% confidence intervals for profiles estimated directly from replicated assay results. The data used were chosen to mimic the sort of data that are typically available in practice, either within laboratories or from external quality-assessment programs. Use of confidence intervals is an effective pictorial way of incorporating information about the quantity and the distribution of the data used for estimation. This is in keeping with an important property of imprecision profile plots: potentially complex information is summarized in a readily comprehensible way. A computer program is available for estimating and plotting profiles and their 95% confidence intervals.
Computer Simulation↗