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Biomedical subjects

V A Johnson

Publications and source records attributed to V A Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1990

The effect of meconium on neonatal and fetal reflectance pulse oximetry.

Reflectance probes are being developed for neonatal use and obstetricians are beginning to use reflectance pulse oximetry to monitor the fetus. When a reflectance probe was used to monitor the arterial oxygen saturation of a baby whose skin was stained with meconium an artificially low result was obtained. This is because meconium absorbs more red than infra-red light and acts as a red light filter between the vascular bed and the probe. This effect may be reproduced by interposing a red filter between a reflectance pulse oximetry probe and the skin. Obstetricians who use a pulse oximeter to assess the fetus through intact membranes will record an erroneously low result if they are stained with meconium. Similarly neonatologists should avoid placing a reflectance pulse oximetry probe on babies skin which is stained with meconium.

False Negative Reactions↗
PubMed1989

Flurbiprofen in post-partum women: plasma and breast milk disposition.

The plasma and milk disposition of flurbiprofen (FB) was assessed in healthy women during the early post-partum period after multiple doses of FB. The results confirmed that a pragmatic study design is an attainable requirement for definitive statements about the excretion of FB in transitional milk. Nine doses of FB (50 mg per dose) were administered during three days. Paired milk and plasma samples were obtained during this period of dosing as well as after the last dose. The plasma data were used to derive an equation, which was then used to simulate cumulative plasma profiles for multiple doses given at unequal time intervals. The observed data corresponded to the simulated cumulative profiles of FB in plasma. The plasma elimination half-life of FB during early lactation was slightly prolonged (mean 4.8 hrs) as compared to reported values for normal adult men. The peak plasma concentrations of FB were comparable to those reported for healthy volunteers. In 10 of 12 women (3-5 days post-partum) the FB concentration in breast milk was less than 0.050 micrograms/ml. In two women the milk concentrations of FB were 0.06, 0.07 and 0.07 micrograms/ml as found in only three samples. We conclude that, on the basis of dose found in milk, FB is safe for women breast feeding their infants in the early post-partum period.

Adult↗
PubMed1989

Synergistic inhibition of human immunodeficiency virus type 1 (HIV-1) replication in vitro by recombinant soluble CD4 and 3'-azido-3'-deoxythymidine.

A combination of antiviral therapies that target different sites in the human immunodeficiency virus type 1 (HIV-1) replicative cycle may be necessary for optimal treatment of HIV-1 infections. We evaluated the interactions of a soluble virus receptor (recombinant soluble CD4 or rsT4) and a reverse transcriptase inhibitor (azidothymidine, AZT) against HIV-1 replication in vitro. A variety of cell types was studied including peripheral blood mononuclear cells, a CD4-positive T-cell line, and a CD4-positive human monocyte cell line. The combination of rsT4 and AZT inhibited HIV-1 synergistically over a broad range of drug concentrations and multiplicities of infection in several different HIV-1 replication assays. Drug interactions were evaluated by the median-effect principle and the isobologram technique using a computer analysis. In all of the cell types tested, combinations of rsT4 and AZT were synergistic in vitro, without additive cytotoxicity.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Synergistic inhibition of human immunodeficiency virus type 1 and type 2 replication in vitro by castanospermine and 3'-azido-3'-deoxythymidine.

Castanospermine and 3'-azido-3'-deoxythymidine (zidovudine) were evaluated in combination against human immunodeficiency virus (HIV) replication in vitro. Castanospermine and 3'-azido-3'-deoxythymidine inhibited HIV type 1 synergistically in acutely infected H9 cells. In addition, they synergistically inhibited both HIV type 1 and HIV type 2 in peripheral blood mononuclear cells. There were no additional toxic effects of these agents in combination. Drug interactions were evaluated by the median-effect principle and the isobologram technique. Combinations of a glycosylation inhibitor, such as castanospermine, with 3'-azido-3'-deoxythymidine deserve consideration for HIV-related chemotherapeutic intervention.

Alkaloids↗
PubMed1988

HIV infection is blocked in vitro by recombinant soluble CD4.

The T-cell surface glycoprotein, CD4 (T4), acts as the cellular receptor for human immunodeficiency virus, type 1 (HIV-1), the first member of the family of viruses that cause acquired immunodeficiency syndrome. HIV recognition of CD4 is probably mediated through the virus envelope glycoprotein (gp120) as shown by co-immunoprecipitation of CD4 and gp120 (ref.5) and by experiments using recombinant gp120 as a binding probe. Here we demonstrate that recombinant soluble CD4(rsT4) purified from the conditioned medium of a stably transfected Chinese hamster ovary cell line is a potent inhibitor of both virus replication and virus-induced cell fusion (syncytium formation). These results suggest that rsT4 is sufficient to bind HIV, and that it represents a potential anti-viral therapy for HIV infection.

Animals↗
PubMed1987

Pharmacologic factors contributing to variance in the milk to plasma ratio for acetaminophen in the goat.

A single-point estimate of the milk to plasma (M/P) drug ratio presupposes an invariant ratio. This may lead to erroneous conclusions about the amount of drug excreted in breast milk. A variance of the M/P ratio with regard to time has been shown for acetaminophen under standardized biologic conditions in the lactating goat. This ratio is potentially confounded by such factors as route of administration, dose amount and duration of exposure to the drug. Each factor was evaluated by computer simulations of the M/P ratio and by derivation of a ratio from empirical data in the goat. Route of administration was found to influence both the pattern and magnitude of the M/P ratio after acetaminophen dosing in the goat. Similar, but less, effects were found for duration of dosing. Dose itself did not influence the ratio. A temporal basis exists for each confounding factor. We thus propose that the M/P ratio is fundamentally variant with time under a standard set of biologic conditions. The contributing variance of confounding factors must be assessed if drug in milk dosing of the infant is to be accurately evaluated by use of the M/P ratio.

Acetaminophen↗
PubMed1982

Development of on-line real-time menu management system.

An on-line, real-time menu management system was developed as a module of the integrated computer-assisted food management system implemented at the University of Missouri-Columbia Health Sciences Center Department of Nutrition and Dietetics. This system supplants a former automated form generating system and permits flexibility in menu design. The major data base in the system is the Master Menu File, which is updated using real-time processing. This file contains data about each occurrence of menu items and is interfaced with existing recipe files to produce numerous printed documents and to display the menu on a video display terminal. The major benefits of the system are flexibility and elimination of typing of worksheets. Entering a new menu or changes to the menu require only a brief amount of time; new revised documents relative to the menu can be generated on the same day. Some of the types of documents available from this system are: master menu, nutrient syllabi, menu audit, and food production forms. The menu is available on-line at all times for reference by dietitians and supervisors. The Master Menu File will be utilized more fully as new modules are designed to interface with the Menu Management System. Production forecasting, patient menu printing, and individualized diet planning are three potential enhancements to the system which will utilize data in the Master Menu File. The file was designed to accommodate additional data as the system in further matured.

Food Service, Hospital↗
PubMed1981

The ultimate prognosis after valve replacement: an assessment at twenty years.

Our experience over a 20-year period consists of 2,135 patients with initial caged-ball valve replacement: 52% aortic, 34% mitral, 12% double, and 2% triple-valve replacements, with 59.2, 39.8, 10.3, and 2.7 patient-centuries of follow-up, respectively. Fifteen-year actuarial survival (+/- standard error) was 43 +/- 2% for aortic and 44 +/- 3% for mitral valve replacement, and 27 +/- 5% for double-valve and 23 +/- 7% for triple-valve replacement. Restricting attention to patients operated on since 1973 divides the series almost in half and does not dramatically improve the 5-year actuarial survival (from 66 +/- 2% to 71 +/- 3% and from 70 +/- 2% to 78 +/- 3% for aortic valve replacement and mitral valve replacement, respectively). There was some alteration in the causes of late death: the largest percentage of deaths in both the earlier and current groups, 52%, was cardiac related whereas only 24% and 13%, respectively, were valve related. Over the past two decades operative mortality has declined and, to a lesser extent, late survival after mitral valve replacement has improved. The incidence of embolism has decreased significantly, most notably with the Silastic ball valves. Dramatic improvements in late results will occur primarily by modifying the cardiac-related death rate through earlier operation and improvements in the medical management of postoperative arrhythmias and congestive heart failure.

Actuarial Analysis↗
PubMed1978

Improvement of wheat protein quality and quantity by breeding.

Substantial genetic, variability for grain protein content in wheat has been identified. In appropriate combinations known genes can increase protein content of wheat grain by 5 percentage points. Productive high protein experimental lines with good agronomic traits and satisfactory processing attributes have been identified. A high protein hard red winter variety developed in Nebraska was released for commercial production in 1975 under the name "Lancota". The high protein of Lancota resides entirely in the starchy endosperm portion of the kernel and is fully transmissible to white milled flour. The high protein of Lancota results from elevated NO3 reductase activity, increased N-absorption by the roots, and more complete translocation of N to the grain. Despite strong environmental influence on wheat protein level, genes for high protein have been demonstrated to effectively increase protein content in many different production environments. Lysine % of protein decreases but lysine % of grain increases as protein is increased. Genetic variability for lysine of sufficient magnitude to overcome the normal depression of lysine % of protein as protein is increased has been uncovered. Experimental lines have been developed in the ARS-Nebraska program in which genes for high protein and high lysine were combined. The lines have been widely distributed for use in other breeding programs.

Breeding↗
PubMed1978

Comparative protein quality as measured by human and small animal bioassays of three lines of winter wheat.

Incomplete information on factors contributing to apparent protein quality and to value of food products as sources of protein and how these factors interact necessitate the use of bioassay procedures. Ideally bioassay procedures should be done using the animal species for which the protein is intended. Practical considerations dictate the use of small animal bioassay rather than human bioassays for routine use in protein product evaluation. To be of real value for routine use in protein product evaluation. To be of real value for assays of food products designed for human use, animal bioassays must accurately predict human performance. Surprisingly little information is available on this topic. In the current project three Nebraska winter wheats of similar genetic backgrounds were evaluated for protein value and for value of the wheats as sources of proteins. Chemical, weanling mouse, adult human and growing human bioassay techniques were employed. Rankings of the grains were similar regardless of species used for protein quality evaluations. Similar rankings were found regardless of species used for protein quality/quantity evaluations. However, ranking varied between methods designed to evaluate protein quality and those designed to measure protein quality/quantity interrelationships. The results stress the importance of matching appropriate methodology with information desired. In a latter project, wheats of dissimilar genetic background were not as uniformily evaluated. This suggests that other factors known to affect protein quality and value were more variable in these wheats.

Animals↗