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Biomedical subjects

R Shoemaker

Publications and source records attributed to R Shoemaker.

33 records · Page 2Linked to original sources
PubMed1986

Use of nude mouse xenografts as preclinical drug screens. Further studies on in vitro growth of xenograft tumor colony-forming cells.

Previous studies suggested tumor colony-forming cells (CFC) grown from xenografts might be useful as a preclinical, in vitro drug screen. To further evaluate this possibility, eight melanoma and six ovarian carcinoma xenografts were established from untreated patients and tested for in vitro CFC growth. For each tumor, linear relationships between cells plated and colony (30 cells or greater than 75 micron diameter) and cluster (10-30 cells or 50-75 micron) growth were observed. All eight melanomas grew sufficient colonies (greater than or equal to 30) for in vitro drug assessment, although four required hypoxic (pO2 = 40) incubation to reliably attain this level of growth. Only one in six of the ovary xenografts consistently grew enough colonies, and growth was not significantly improved by hypoxic incubation, or addition of luteinizing hormone, follicle-stimulating hormone, or steroid hormones. Cloning efficiencies (colonies + clusters/cells plated) for tumors demonstrating adequate growth ranged from 0.01% to 0.3%. For most tumors, no direct relationship was observed between characteristics of xenograft tumors (size) or their resulting cell suspensions (viabilities, cell yield) and CFC growth. Cell suspensions were incubated with a 3 log concentration of nine established chemotherapeutic agents. Resulting dose-effect curves were linear and showed no plateaus of drug effect. Analyzing 447 in vitro drug trials on six melanomas and one ovarian carcinoma, interexperiment variability was high. Cell lines were established from three xenografts using a low concentration of fetal bovine serum (1%), and also examined for in vitro drug sensitivity. Using both liquid culture isotope incorporation and a colony-forming assay, drug sensitivity profiles for the cell lines were nearly identical to those for parent xenograft CFC. However, assays performed using the cell lines were more reproducible than those using xenograft tissue. The authors conclude that tumor CFC can be reliably grown from melanoma xenografts, but in vitro drug assays using these xenografts are poorly reproducible. The xenografts are a resource for establishing cell lines, and drug assays performed using these lines are highly reproducible. Similarities in drug sensitivity profiles for parent xenograft CFC and derived cell lines suggest that, despite poor reproducibility, repetitive assays using melanoma CFC accurately reflect some properties of cells which sustain tumor cell growth.

Animals↗
PubMed1986

Metabolic stability of experimental chemotherapeutic agents in hepatocyte:tumor cell co-cultures.

A U.S. National Cancer Institute screening program for new anticancer drugs, based on the growth of primary human tumor cells in an in vitro soft agar colony formation assay, has resulted in the identification of a number of compounds that have cytotoxic activity against primary human tumor cells in vitro but are inactive in the conventional in vivo murine P388 leukemia animal model pre-screen. To investigate whether metabolic inactivation ov the compounds might be a factor in the lack of in vivo cytotoxicity we have co-cultured rat hepatocytes with A204 rhabdomyosarcoma and murine P388 leukemia cell lines in the soft agarose colony formation assay for 24 h during exposure to the compounds. Twenty compounds with a range of in vitro activities were studied. Thirteen compounds exhibited cytotoxicity against A204 cells in culture; nine of them were less active when co-cultured with hepatocytes, two were activated by hepatocyte co-culture, and two showed no effect of hepatocyte co-culture. P388 cells were more sensitive to the antiproliferative effects of the compounds than A204 cells. Two compounds that were not active against A204 cells exhibited cytotoxicity against P388 cells. One compound was inactivated by hepatocyte co-culture and one showed no effect. Five compounds showed no cytotoxicity toward either A204 cells or P388 cells. Two of the compounds showing hepatocyte inactivation in vitro possess activity in one or more in vivo tumor models. Thus, evidence for metabolic inactivation in hepatocyte co-culture is not always an indication for lack of in vivo antitumor activity. Hepatocyte co-culture methodology provides a simple and objective means, amenable to large-scale screening, of distinguishing metabolic activation or inactivation of a given compound from other pharmacokinetic and pharmacodynamic factors with a minimum of material.

Animals↗
PubMed1981

Aggressive treatment of acquired phrenic nerve paralysis in infants and small children.

Transthoracic diaphragmatic plication is a simple and effective means of treatment for phrenic nerve injury and resultant diaphragmatic paralysis, and should be undertaken as soon as the diagnosis of diaphragmatic paralysis is established in a child with substantial respiratory difficulty. Seven of more than 1,500 patients sustained phrenic nerve injury during operation for congenital heart disease at our institution over the past five years. All but 1 patient were less than 5 months old, and the average weight was 3.8 kg. Five of the 7 could not be weaned from the ventilator, and the other 2 had persistent postoperative tachypnea and stridor. Before 1980, 3 patients were intubated for an average of 16 days prior to diagnosis by fluoroscopy. Since then, 4 patients have been intubated for an average of 7.8 days before diagnosis. All 7 underwent transthoracic diaphragmatic plication and were extubated by 6 days after operation (mean, 3.7 days). Six patients survived and are doing well. The 1 death occurred in 1976 in a premature infant with multiple congenital cardiac lesions; diagnosis was delayed until the twenty-eighth day after intubation and transthoracic diaphragmatic plication, until the sixty-second day. This infant died of pneumonia one month after extubation. These data support our policy of establishing an early diagnosis of phrenic nerve injury and early treatment utilizing transthoracic diaphragmatic plication in symptomatic children.

Cardiac Surgical Procedures↗
PubMed1981

Carotid artery aneurysms: another approach to therapy.

A patient had a large internal carotid artery aneurysm with extension to the base of the skull. Resection and reconstitution of flow was thought to be hazardous because of the difficulty in obtaining distal control. After assessment of collateral flow to the brain, placement of a Selverstone clamp resulted in gradual occlusion of the aneurysm. The aneurysm was subsequently resected.

Aneurysm↗
PubMed1979

Ultrafast laser scanner microscope.

Advances in monolayer deposition of cervical cells have removed one of the last serious obstacles to the design of high-resolution automated diagnostic assessment systems. In this article, we describe the design considerations for a system that is capable of acquiring, within 60 sec, a 0.5 micron digitized image of a 4 cm2 area on a standard glass slide. The most feasible approach is found to be a system using a rotating polygon to sweep the focused spot from a laser across a 2-mm scan line while the slide is uniformly translated perpendicular to the scan direction the use of laser sources (a helium-neon laser at 632 nm and a krypton ion laser at 568 and/or 476 nm) as compared to the incoherent light sources used in conventional microscope systems alleviates many of the optical design problems and provides the proper wavelengths needed for recognition of Papanicolaou stained cells. We also find that focus control of the scanning spot should be achievable using a technique involving a holographic grating. Other relevant considerations such as sample heating problems, multiphoton absorption by the sample, detector signal-to-noise ratios, laser amplitude noise control, and the digitization and buffering of the data stream are also discussed.

Computers↗
PubMedDate not supplied

Treatment of persistent Pfiesteria-human illness syndrome.

Patients with exposure to Pfiesteria toxin have developed an illness, Pfiesteria-human illness syndrome, characterized by skin lesions, headache, myalgias, conjunctival irritation, bronchospasm, abdominal pain, secretory diarrhea, recent memory loss, and difficulties with number sequencing. Not all patients demonstrated all features of the syndrome. The natural history of Pfiesteria-human illness syndrome shows that most patients' symptoms improve without treatment. This article reports the improvement of symptoms that had persisted for over one month in five patients, which the author attributes to treatment with cholestyramine. These patients were self-referred to the Pocomoke River Rash and Associated Illness Center, a clinic that opened on August 6, 1997, in response to the need for a central facility for diagnosis of human illness acquired from Pfiesteria. Until the Pfiesteria toxin(s) is isolated and characterized, and laboratory diagnostic tests are available, physicians must be able to recognize Pfiesteria-human illness syndrome and intervene when symptoms, particularly memory loss and diarrhea, cause significant impairment in daily activities. There are no precedents for the treatment of Pfiesteria or any dinoflagellate toxin-related human illness reported in the literature. The successful use of cholestyramine reported here may provide a model for understanding dinoflagellate toxin physiology in the human body. This paper reports an uncontrolled observational study. When identification of the toxin is completed, a basis for properly controlled studies will be available.

Administration, Oral↗