Search PubMed⌕ Search

Biomedical subjects

C R Johnson

Publications and source records attributed to C R Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1984

A graduate program designed for medical and other doctoral degree applicants.

The data collected during the evaluation of the natural science program at Roswell Park revealed a high rate of success in preparing students to enter health and science related careers. An average of 50 percent of the entering students each year had been unsuccessful medical school applicants or students preparing to enter Ph.D. programs following an initial research experience. The program assists students in admission to medical and research programs and encourages research participation. Many graduate programs will not accept or find difficulty dealing with students who have career goals in medicine and are not necessarily in research. This is understandable, especially in Ph.D. granting programs with substantial investments of faculty time and funding. The philosophy of the program reported here is to assist the students to enter the career of their choice; however, at the same time, the faculty members insist on a high level of scholarship in course work and research during the program. With this philosophy, the program continues to be successful in attracting students of high quality.

Education, Graduate↗
PubMed1984

Photosynthate partitioning in split-root citrus seedlings with mycorrhizal and nonmycorrhizal root systems.

Photosynthate partitioning was examined in seedings of sour orange (Citrus aurantium L.) and Carrizo citrange (Poncirus trifoliata [L.] Raf. x C. sinensis [L.] Osbeck) grown with split root systems inoculated on one side with vesicular-arbuscular mycorrhizal fungus (Glomus intraradices Schenck and Smith). Source-sink relations were studied without mitigating differences in mineral content or physiological age that can occur in separate plant comparisons, because phosphorus was evenly distributed between leaves on opposite sides of the seedlings. Above-ground portions of each plant were exposed to (14)CO(2) for 8.5 minutes and ambient air for 2 hours, followed by extraction and identification of labeled assimilates. Mycorrhizal halves of root systems accumulated 66 and 68% of the (14)C-labeled photosynthates translocated to roots of sour orange and ;Carrizo' citrange, respectively, as well as an average of 77% greater disintegrations per minute per gram fresh weight. Distribution of (14)C-labeled assimilates was independent of phosphorus effects on photosynthate partitioning in leaves and did not reflect fresh or dry weights of roots or degree of mycorrhizal dependency of the species. Differences in radioactivity between mycorrhizal and nonmycorrhizal root halves after 2 hours indicated at least 3 to 5% of the whole plant (14)C-labeled photosynthates were allocated to mycorrhizae-related events on one side and that twice this amount, or 6 to 10%, might be expected if the entire root system was infected.

Journal Article↗
PubMed1983

A method for the derivation and continuous propagation of cloned murine bone marrow macrophages.

A method is proposed for the initiation and long term propagation of clonal macrophage cell lines descended from single bone marrow precursor cells. The cells were cloned in soft agar at low cell density, and the resultant colonies were picked from the agar and expanded in liquid culture. The optimal medium for liquid culture contained 75% Dulbecco's Modified Eagle's Medium with high glucose/high bicarbonate, 10% fetal calf serum, 5% horse serum, and 10% L cell conditioned medium. During growth in liquid culture, the cells were plastic adherent but they were easily removed from polymethylpentene or polystyrene culture dishes by means of a jet of cold medium directed through a 25-gauge needle. More than 50 cell lines from 17 mouse strains have been subcultured continuously for many months, some for more than 2.5 years with no evidence of culture senescence or appreciable change in exponential growth rates. Cells from these lines were all adherent, phagocytic, Fc receptor positive, and esterase positive. Cells from each cell line tested expressed MHC-encoded surface antigens and were able to stimulate allogeneic mixed lymphocyte reactions. Using these methods of continuous culture, pure, functionally active normal macrophages could be repeatedly harvested in large numbers from any of the lines.

Animals↗
PubMed1982

Quaternary heterocyclylamino beta-lactams: a generic alternative to the classical acylamino side chain.

6 beta-[(1-Substituted-4-pyridinio)amino]penam-3-carboxylates and 7 beta-[(1-substituted-4-pyridinio)amino]ceph-3-em-4-carboxylates have been found to be interesting new classes of antibacterial beta-lactams, readily available by SN2 Ar coupling of fluoro-substituted quaternized pyridines and appropriate amino lactam carboxylic acids. Compared to penicillin G, the penam 12c exhibited a spectrum extended to Gram-negative species, such as Escherichia, Shigella, Klebsiella and Enterobacter, offset by a loss of potency against Gram-positive species. Excluding Pseudomonas, many examples of the cephems showed excellent activity against the above Gram-negative organisms, and in some cases, such as 15i, the spectrum included good performance against the staphylococci and streptococci. With Serratia and many Proteus species, there was an adverse inoculum and medium effect which was not observed in the good Gram-positive reach of the cephem series.

Anti-Bacterial Agents↗
PubMed1980

Pathology data quality assurance and data retrieval at the National Center for Toxicological Research.

Automated experimental and pathology data collection and reporting systems are utilized at the National Center for Toxicological Research to increase the efficiency of the variety of research studies being performed. In order for the ED01 study to be conducted in an effective manner, usage of these automated systems was considered advantageous due to the study size, approximately 24,000 mice. The large volume of pathology and other experiment data generated in the study required detailed quality assurance and data retrieval, and the use of automated systems allowed this to be performed much more easily than with manual methods. This paper addresses the methods employed to ensure quality and to provide the data retrieval capabilities necessary for conducting and analyzing the ED01 study.

Government Agencies↗
PubMed1980

Logistics of conducting a chronic study with 24,192 mice.

Some of the logistical problems of conducting the ED01 study at the National Center for Toxicological Research are discussed, including problems in site preparation, animal production, support during the execution of the study, pathology support, and data analysis. In order to manage the vast amount of data that would be generated by a 24,192 mouse study, computer-assisted data collection systems and automated data storage and retrieval systems were developed. These systems, along with other procedures at NCTR, made the execution of a study of this magnitude possible and allowed timely experiment management. Preliminary data analysis during the course of the study resulted in a decision to extend the duration of one segment of the study.

Animal Husbandry↗
PubMed1978

Electron spin resonance studies of the solution structure of vanadyl amino acid complexes and mixed ligand complexes of oxalate.

Esr and electronic spectra of complexes of the general composition VO(AA)2 and VO(ox)(AA) have been characterized; AA = gly, his, cys, pro, val, met, asp amino acids. Spectra of the formulation VO(ox)(LL) (with LL = imidazole plus monodentate oxalate, histamine plus monodentate oxalate, histidine, cysteine, 4-imidazolepropionic acid, mercaptopropionic acid, ethylenediamine and ethanolamine) have been used to deduce a self-consistent assignment of AL, a ligand donor additivity constant contribution to the observed hyperfine splitting, Aiso. Values of AL are sensitive to inductive effects in the ligand structure. The solution structures and likely coordination geometries of VO(his)2, and VO(cys)22-- are discussed. The role of the imidazole moiety as a sigma donor and sulfhydryl sulfur as a pi acceptor is observed in VO(AA)2 and VO(ox)(AA) complexes.

Amino Acids↗
PubMed1975

Food satiation as a procedure to decelerate vomiting.

A food satiation procedure was used in two experiments to decelerate the frequency of vomiting responses in two profoundly retarded adults who exhibited well-defined vomiting-ruminatory response chains. For several years prior to this study, the subjects had exhibited a history of vomiting behavior. Satiation was accomplished during regular meals and consisted of allowing the subjects to eat until a satiation criterion of food refusal was achieved. The results revealed a 94 percent reduction of vomiting in Experiment 1 and a 50 percent response reduction in Experiment 2. Ten-day follow-up sessions indicated that the response reduction was maintained in both experiments. In Experiment 1 the subject exhibited a 4.99 kg weight gain at the 10-day follow-up with a total of 13.61 kg weight gain at a 4-week posttreatment weight check.

Feeding Behavior↗