Biomedical subjects
Publications and source records attributed to C J Singer.
The advent of "local delivery systems" now occurring throughout the nation will require a new applications portfolio for successful providers. These applications must address the key needs of the provider and patient community, including hospital information systems, physician practice systems, managed-care and insurance systems, electronic data interchange and the automated patient record. Any less just won't do.
Healthcare organizations stand to benefit greatly from facilities management. Nevertheless, there is a glaring lack of interest among organizations to consider this option. Healthcare consultant Charles Singer explores the potential advantages of bringing in a second party to handle part or all of a group's data processing operations.
Market surveys show that a dramatic organizational and economic restructuring of medical care delivery is taking place at the local level. These changes suggest a trend in which a finite number of umbrella corporations within each local area will be established and will control the majority of medical care provided. Information systems will play a critical role in determining the success or failure of these organizations.
Because it no longer seemed reasonable to us that the sole function of the steroid-binding proteins in plasma was to serve as a buffer reservoir for steroid hormones, we conducted experiments which sought out other possibilities. Both CBG and SHBG bind to cell membranes, and this interaction partakes of the general characteristics of peptide hormone-membrane receptor systems. Additionally, human CBG has the ability to cause an increase in the activity of membrane-bound adenylate cyclase in MCF-7 cells, and this, in turn, results in an increase in cellular cAMP content. Thus, CBG appears to be a protein hormone. As a first consideration, one might presume that because CBG's half-life is measured in days, it would be counted among the hormones which, for the most part, are tonic in their effects, e.g., thyroid hormone. However, two important considerations tend to believe this presumption: (1) CBG which is unoccupied by steroid is not hormonally active (Figure 5): (2) Depending upon the time of day, circulating CBG is approximately 0-60% occupied in normal humans. These observations result in a circumstance in which a substantial portion of circulating CBG is available for activation by bursts of cortisol secretion. It seems prudent to speculate that, because steroids are essential for CBG's activity, the hormonal role of CBG may be entwined with, or complementary to the steroids which it binds. Finally, we should comment on the impact that our model of CBG as a hormone has on the view that only unbound steroid can be hormonally active. First, it should be stated that we have not addressed this question experimentally. Although there is evidence that CBG may be required for cortisol action, we feel that an obligate role for it is not documented adequately. At this time, we believe that CBG's hormonal role is compatible with a hypothesis that encompasses the view that unbound steroid hormones can diffuse into cells in some tissues and that both free and bound steroid can enter cells in others. Obviously, the final word on these important topics, as always, awaits the proper experiments.
Specific binding sites for corticosteroid-binding globulin (CBG) were detected on membranes prepared from rat spleen. The binding sites are typical of membrane receptors; they are saturable, specific, have high affinity, and require Mg2+ or Ca2+ for binding. There was little specific binding at 4 C, and maximal binding was obtained at 37 C. Scatchard analysis revealed a single set of binding sites with an apparent Kd of 0.84 microM, and a binding capacity of 39 pmol/mg membrane protein. The sites were specific for CBG; binding of [125I]CBG was not inhibited by a 10,000-fold excess of either rat albumin or rat transferrin. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate of the membrane-bound [125I]CBG revealed the presence of lower mol wt iodinated products which were undetectable in the unbound [125I]CBG fraction. Further, whereas the electrophoretic patterns from uterine, pulmonary, and renal membranes showed that the less mobile band (mol wt, 60K) of the normal CBG doublet appeared to be metabolized to a greater extent than the more mobile band (mol wt, 52K), those from splenic membranes showed equal metabolism of both parts of the doublet.
The role of 11 beta,20-dihydroxy-3-oxopregna-4,17(20)-dien-21-al (F enol aldehyde) as an intermediate in the biological conversion of cortisol to a 17-deoxy-21-oic acid was studied in vitro with mouse liver as the source of enzyme. The substrate, [1,2-3H]F enol aldehyde, was synthesized and found to contain cis and trans isomeric forms in a ratio of approximately 3:1. Tritium labeled F enol aldehyde was incubated with mouse liver homogenates. The metabolic products were analyzed by TLC and HPLC. 11 beta,20-Dihydroxy-3-oxopregna-4-en-21-oic acid, a 17-deoxy-21-oic acid, was identified as a quantitatively significant metabolite of the cis isomer. Metabolic conversion of the trans isomer to acid metabolites did not occur. The results are consistent with our hypothesis that the metabolic 17-dehydroxylation of cortisol requires an enol aldehyde intermediate and indicate that the conversion of the enol aldehyde to hydroxy acid is stereospecific.
An automated medical record system (AMRS) at the Harvard Community Health Plan supports medical records membership and the management needs of the 146,000-member health maintenance organization. The ARMS is fully integrated into the operation of HCHP's health centers and into the clinical practice of the medical staff. User interviews conducted as part of a systems planning effort revealed a high level of satisfaction with the system. The acceptance of and enthusiasm for the AMRS was coupled with a variety of ideas for improvement and enhancements to the system. Most of these suggestions were not uniquely related to the automated technology supporting the system but rather addressed medical records issues familiar to conventional paper systems. While this distinction is subtle, it further confirms the viability of an automated system and suggests directions for future growth.
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Recent experiments in normal animals have shown that Tc-99m N,N'-bis(mercaptoacetamido)ethylenediamine (Tc-99m DADS) is a potential technetium-99m-labeled replacement for [131I]ortho-iodohippurate(I-131 Hipp). We compared the two agents in eleven patients with renal transplants (serum creatinine range: 0.9--5.7 mg/dl). Digital and analog images were recorded for 30 min and after voiding. The results indicate that the relative extraction efficiency index of Tc-99m DADS is 76% +/- 3 (mean +/- s.e.m.), that the leading-edge parenchymal transit time of Tc-99m DADS is 137% +/- 6, and that the percentage of injected Tc-99m DADS in the bladder at 30 min is 25% +/- 4 of that of I-131 Hipp (all p less than 0.05). Forty percent of patients showed some hepatobiliary excretion of Tc-99m DADS. We conclude that the biologic properties of Tc-99m DADS are inferior to those of I-131 Hipp and that analogs of Tc-99m DADS should be evaluated in an attempt to find a more suitable technetium-99m-labeled replacement for I-131 Hipp.
Procedures for the assay of chloramphenicol in milk, urine, serum, and muscle tissue are presented. The procedures specify an assay design with all standards as well as samples present on each plate, oxytetracycline in the buffer-diluent for greater sensitivity, a minimal medium to enhance the inhibitory effect of chloramphenicol on the assay organism, and a tetrazolium dye to improve the ability to measure the zones of inhibition. Recoveries of unbound chloramphenicol from bovine urine were 90.8%, from serum 88.3%, from milk 79.3%, from swine muscle 71.3%, and from beef and chicken muscle 61.0 and 61.4%, respectively. The lower levels of measurement in urine and serum were 0.25 microgram/mL, 0.025 microgram/mL in milk, and 0.10 microgram/g in muscle tissue.