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D W Levine

Publications and source records attributed to D W Levine.

23 records · Page 2Linked to original sources
PubMed1977

Microcarrier cell culture: new methods for research-scale application.

A positive-charge-carrying, dextran microsphere has been developed which serves as an excellent surface for the attachment and growth of anchorage-dependent cells in microcarrier culture. With standard cell culture media, saturation cell concentrations in excess of 4 X 10(6) cells/ml are routinely obtained for secondary chicken embryo fibroblasts or normal diploid human fibroblasts. The use of microcarriers reduces the time, expense, and apparatus complexity required for the routine propagation of anchorage-dependent cells.

Cells, Cultured↗
PubMed1977

Virus production with a newly developed microcarrier system.

Primary cell cultures as well as established lines have been grown on a recently developed microcarrier configuration that overcomes the problem of toxicity attendant on earlier developments in this technology. Virus yields from these cells propagated on the new microcarriers have been measured. Microcarrier-grown cells, when compared to roller-bottle-grown cells, gave virus yields on a per-cell basis that varied from slightly greater with the Sindbis virus-Chinese hamster ovary cells and polio-WI-38 combinations to approximately one-third with Moloney murine leukemia virus-Cl-1 mouse cells and vesicular stomatitis virus-chicken embryo fibroblasts. Yields ranged from 8.0 X 10(7) to 3.6 X 10(8) cells per 100-ml microcarrier culture and from 3.7 X 10(7) to 4.1 X 20(8) cells per roller-bottle culture. Secondary chicken embryo fibroblast yields were approximately four times as great in microcarrier cultures as in standard roller-bottle cultures, per unit volume of medium consumed. In spite of the reduced virus yields per cell seen in some instances, the greater cellular productivity of microcarrier cultures appears to hold great promise for large-scale virus production. Optimizing microcarrier conditions for specific cell-virus systems should result in improved yields.

Cell Division↗
PubMed1973

Isolation and characterization of a thermotolerant methanol-utilizing yeast.

A yeast capable of growth on methanol as its sole carbon-energy source was isoalted from soil samples and identified as a strain of Hansenula polymorpha. A continuous enrichment culture at 37 C with a simple mineral salts medium was used to select this organism. The isolate, designated DL-1, has a maximal specific growth rate of 0.22 per h, at pH 4.5 to 5.5 and temperatures of 37 to 42 C, in simple mineral salts medium with methanol (0.5%), biotin, and thiamine. Growth occurred in a chemostat at temperatures up to 50 C, with strong growth at 45 C. The maximal growth yield of the yeast on methanol was 0.36 g of dry cell weight per g of methanol, and the yield on oxygen was 0.37 g of dry cell weight per g of O(2). Protein content of the isolate is 46%, and total nucleic acid content varies from 5.0 to 7.0% with increasing growth rate from 0.08 to 0.20 per h. The amino acid profile of this yeast protein indicates that it could serve as a good source of food protein. Feeding studies with rats show the yeast to have no toxic effects.

Amino Acids↗
PubMedDate not supplied

Measurement of continuous ambulatory peritoneal dialysis prescription adherence using a novel approach.

OBJECTIVE: The purpose of the study was to test a novel approach to monitoring the adherence of continuous ambulatory peritoneal dialysis (CAPD) patients to their dialysis prescription. DESIGN: A descriptive observational study was done in which exchange behaviors were monitored over a 2-week period of time. SETTING: Patients were recruited from an outpatient dialysis center. PARTICIPANTS: A convenience sample of patients undergoing CAPD at Piedmont Dialysis Center in Winston-Salem, North Carolina was recruited for the study. Of 31 CAPD patients, 20 (64.5%) agreed to participate. MEASURES: Adherence of CAPD patients to their dialysis prescription was monitored using daily logs and an electronic monitoring device (the Medication Event Monitoring System, or MEMS; APREX, Menlo Park, California, U.S.A.). Patients recorded in their logs their exchange activities during the 2-week observation period. Concurrently, patients were instructed to deposit the pull tab from their dialysate bag into a MEMS bottle immediately after performing each exchange. The MEMS bottle was closed with a cap containing a computer chip that recorded the date and time each time the bottle was opened. RESULTS: One individual's MEMS device malfunctioned and thus the data presented in this report are based upon the remaining 19 patients. A significant discrepancy was found between log data and MEMS data, with MEMS data indicating a greater number and percentage of missed exchanges. MEMS data indicated that some patients concentrated their exchange activities during the day, with shortened dwell times between exchanges. Three indices were developed for this study: a measure of the average time spent in noncompliance, and indices of consistency in the timing of exchanges within and between days. Patients who were defined as consistent had lower scores on the noncompliance index compared to patients defined as inconsistent (p = 0.015). CONCLUSIONS: This study describes a methodology that may be useful in assessing adherence to the peritoneal dialysis regimen. Of particular significance is the ability to assess the timing of exchanges over the course of a day. Clinical implications are limited due to issues of data reliability and validity, the short-term nature of the study, the small sample, and the fact that clinical outcomes were not considered in this methodology study. Additional research is needed to further develop this data-collection approach.

Adult↗