Balancing Detection and Eradication for Control of Epidemics: Sudden Oak Death in Mixed-Species Stands

Culling of infected individuals is a widely used measure for the control of several plant and animal pathogens but culling first requires detection of often cryptically-infected hosts. In this paper, we address the problem of how to allocate resources between detection and culling when the budget for disease management is limited. The results are generic but we motivate the problem for the control of a botanical epidemic in a natural ecosystem: sudden oak death in mixed evergreen forests in coastal California, in which species composition is generally dominated by a spreader species (bay laurel) and a second host species (coast live oak) that is an epidemiological dead-end in that it does not transmit infection but which is frequently a target for preservation. Using a combination of an epidemiological model for two host species with a common pathogen together with optimal control theory we address the problem of how to balance the allocation of resources for detection and epidemic control in order to preserve both host species in the ecosystem. Contrary to simple expectations our results show that an intermediate level of detection is optimal. Low levels of detection, characteristic of low effort expended on searching and detection of diseased trees, and high detection levels, exemplified by the deployment of large amounts of resources to identify diseased trees, fail to bring the epidemic under control. Importantly, we show that a slight change in the balance between the resources allocated to detection and those allocated to control may lead to drastic inefficiencies in control strategies. The results hold when quarantine is introduced to reduce the ingress of infected material into the region of interest.     

Chromosomal localization of the human histamine H1-receptor gene

We have assigned the human histamine H₁-receptor gene to chromosome 3 by Southern blot analysis of a chromosome mapping panel constructed from humanhamster somatic cell hybrids. This assignment was confirmed by in situ hybridization on metaphase chromosomes and involved bands 3p14–p21.     

Use of nuclear morphometry characteristics to distinguish between normal and abnormal cervical glandular histologies.

This is a methodological study exploring the use of quantitative histopathology applied to the cervix to discriminate between normal and cancerous (consisting of adenocarcinoma and adenocarcinoma in situ) tissue samples. The goal is classifying tissue samples, which are populations of cells, from measurements on the cells. Our method uses one particular feature, the IODs-Index, to create a tissue level feature. The specific goal of this study is to find a threshold for the IODs-Index that is used to create the tissue level feature. The main statistical tool is Receiver Operating Characteristic (ROC) curve analysis. When applied to the data, our method achieved promising results with good estimated sensitivity and specificity for our data set. The optimal threshold for the IODs-Index was found to be 2.12.     

Continuous hybridoma culture in a low-protein serum-free medium supplemented with liposomes

A homemade serum-free medium containing a low protein level under 0.1 g l⁻¹ has been proved to support long-term cultures of VO 208 hybridoma cells successfully up to 50 days. The low protein level was achieved by supplying the lipids through liposomes containing cholesterol, oleic acid, - dipalmitoyl phosphatidylcholine, and bovine serum albumin. The influence of the liposome content in the feeding medium was studied in a continuous culture performed with step variations of the liposomes level, from 7.5 to 30 ml l⁻¹. The cell density decreased at the highest liposomes content while it became higher with 7.5 or 12 ml l⁻¹ of liposomes. For each step variation appeared a transitory activation of the specific rates of nutrient consumption, metabolite production and antibody secretion, as well as a transitory decrease of the specific cell growth rate. The overall structure of the antibodies was not affected during the culture.     

Lactate dehydrogenase (LDH) activity of the cultured eukaryotic cells as marker of the number of dead cells in the medium [corrected]

One significant problem in monitoring a culture's evolution is to assess change in cell viability. We have demonstrated that LDH release could be a good indicator of cellular damage of many cell lines, especially during shear stress or sonication. Moreover, we have found a significant correlation between the number of dead cells, determined by Trypan Blue staining, and LDH activity measurements in the supernatant of hybridoma strains, whatever the culture conditions. We have also shown that when viability is still near 100% no LDH is released even at high cell concentrations. Therefore, LDH should serve as a potential marker of cell injury and death.     

Influence of inoculum age on hybridoma culture kinetics

To determine the influence of the inoculum age on the kinetics of hybridoma growth and metabolism, spinner flasks have been inoculated with cells previously propagated in T flasks for 43, 52, 62 and 71 hr respectively. Increasing the age of the inoculum is found to result in a longer lag phase, in a lower maximum specific growth rate and in a reduced maximal cell density. During the growth phase specific rates of glucose and glutamine uptake and of ammonia and lactate production are similar. However, with the older inoculum, much higher metabolic activities are observed during the lag phase. The production of antibodies is delayed with increasing inoculum age, but the final antibody concentrations are similar, which indicates a higher specific antibody production rate when inoculating with older cells.