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Biomedical subjects

C A Rohde

Publications and source records attributed to C A Rohde.

5 recordsLinked to original sources
PubMed1991

Dynamics of platelet-activating-factor release and uptake in a human neutrophil suspension.

The present study has examined the dynamics of platelet-activating-factor (PAF) synthesis, release and uptake in order to understand better the trafficking of PAF between cells and medium. Initial experiments indicated that the amount of PAF found on the outside of the cell remained constant well after the synthesis from a precursor had apparently stopped, and in spite of a continued capacity of the cell to take up and catabolize PAF. These results suggested that PAF produced and stored within the cell is eventually released to the outside of the cell at a rate proportional to that of cellular uptake. In order to estimate the amount of PAF released from the cell, the processes of PAF release and uptake were modelled using simple mathematical functions. It was found that, under the experimental conditions used in this study, the uptake of PAF could be expressed as an exponential function tending to a non-zero baseline. Utilizing this rate constant for the uptake of PAF with the amount of PAF outside the cell, the amount of total PAF released from the cell was estimated. Data from the model suggested PAF was released in amounts 10-fold higher than could actually be measured over 30 min. In fact, the model predicted more PAF could be released from the cell than is synthesized, suggesting that a portion of the PAF which is released is taken up and then released again to the outside of the cell. The potential for PAF and/or its intermediates to be recycled was verified by demonstrating that a large proportion of exogenously provided 1-alkyl-2-lyso-sn-glycero-3-phosphocholine is taken up by the neutrophil, converted into PAF and then released again by the cell. These results suggest that PAF trafficking between the cell and medium is complex and involves many processes, which include synthesis, release, uptake, catabolism and recycling.

Calcimycin↗
PubMed1987

Influence of serum cholesterol and albumin on partitioning of PCB congeners between human serum and adipose tissue.

The influence of serum lipids and proteins on partitioning of individual polychlorinated biphenyl (PCB) congener peaks between human serum and adipose tissue lipid was assessed using regression analysis. Subjects were 55 repair workers who were either currently or previously exposed, and 56 comparison workers without occupational exposure to PCBs. Seven congeners (2,4,5,4'-tetra CB, 2,3,5,2',3',6'-hexa CB, 2,3,4,2',3',6'-hexa CB, 2,3,4,2',4',5'-hexa CB, 3,4,5,3',4'-penta CB, 2,3,4,5,2',3',4'-hepta CB, and 2,3,4,5,2',3',4',5'-octa CB) which had been quantified in both serum and adipose tissue in at least one-third of the total study population were selected for evaluation. Initially the crude correlations between the serum PCB and certain candidate variables were assessed; more than one congener was correlated with serum cholesterol, albumin, triglycerides, low-density lipoproteins, very low-density lipoproteins, age, body fat content, and average servings of fish per day. Stepwise regression of log serum congener concentration on log adipose congener concentration and these variables was performed. Only cholesterol, albumin, and average servings of fish per day were significant for at least one congener peak. Congeners behaved in two groups, depending on their order of chromatographic elution. For 2,4,5,4'-tetra CB, 2,3,5,2',3',6'-hexa CB, and 2,3,4,2',3',6'-hexa CB, log serum concentration was not significantly correlated with log adipose congener concentration, and there was no consistent pattern for significant candidate variables. For congeners 2,3,4,2',4',5'-hexa CB, 3,4,5,3',4'-penta CB, 2,3,4,5,2',3',4'-hepta CB, and 2,3,4,5,2',3',4',5'-octa CB, log serum congener concentration was consistently significantly correlated with log adipose congener concentration and serum cholesterol positively, and with serum albumin negatively. For these four congeners the explanations of variation (R2) in serum congener concentration using adipose congener concentration alone were 3, 23, 20, and 30%, respectively, and after adding cholesterol and albumin were 13, 56, 43, and 46%. Thus we conclude that serum cholesterol and albumin can influence the distribution or partition of PCBs between serum and adipose tissue.

Adipose Tissue↗
PubMed1978

Medical economics survey-methods study: cost-effectiveness of alternative survey strategies.

The Medical Economics Survey-Methods Study was conducted under contract for the National Center for Health Statistics during 1975-76. The objective was to determine the cost-effectiveness of a variety of strategies under consideration for application in a national survey in 1977. Detailed data on health care utilization and expenditures were collected periodically from a panel of 691 Maryland households over a seven-month period. Issues tested through a random experimental design included the relative effectiveness of monthly versus bimonthly interviews and in-person versus telephone contact. Completeness and accuracy of information were determined through an extensive record check involving all providers and third party payers identified in the household check involving all providers and third party payers identified in the household survey. The results indicate that there are substantial deficiencies in the household reporting and that the household data for all types of medical services would benefit from the availability of record data in order to improve theri accuracy. The frequency of contact (monthly versus bimonthly) had little effect on the accuracy of reporting. Given the higher rate of attrition observed for the monthly procedures and their considerably greater cost, the bimonthly interval appears to offer advantages. In-person contact resulted in significantly better reporting compared with telephone contact in the Baltimore area, but no difference was found in more rural Washington County. Thus, the 10 per cent cost increase for in-person contact may well be justified by the improved accuracy of the data obtained for certain types of populations.

Cost-Benefit Analysis↗
PubMed1976

Composite sampling.

In sampling certain types of materials, such as bags of fertilizer, or subsampling large quantities of water, as might be done in investigating the density of plankton in certain environmental situations, it is customary to composite the samples. That is, several samples are drawn, mixed into a composite sample, and a sample taken from the composite is then used to determine relevant characteristics of the population. In this paper the results of Brown and Fisher [1972] are extended to more complex situations (e.g., more than one variance component present).

Biometry↗