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Biomedical subjects

W H McBride

Publications and source records attributed to W H McBride.

At least 19 recordsLinked to original sources
PubMed1995

Induction of acute phase gene expression by brain irradiation.

PURPOSE: To investigate the in vivo acute phase molecular response of the brain to ionizing radiation. METHODS AND MATERIALS: C3Hf/Sed/Kam mice were given midbrain or whole-body irradiation. Cerebral expression of interleukins (IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6), interferon (IFN-gamma), tumor necrosis factors (TNF-alpha and TNF-beta), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthetase (iNOS), von Willebrand factor (vWF), alpha 1-antichymotrypsin (EB22/5.3), and glial fibrillary acidic protein (GFAP) was measured at various times after various radiation doses by ribonuclease (RNase) protection assay. The effects of dexamethasone or pentoxifylline treatment of mice on radiation-induced gene expression were also examined. RESULTS: Levels of TNF-alpha, IL-1 beta, ICAM-1, EB22/5.3 and to a lesser extent IL-1 alpha and GFAP, messenger RNA were increased in the brain after irradiation, whether the dose was delivered to the whole body or only to the midbrain. Responses were radiation dose dependent, but were not found below 7 Gy; the exception being ICAM-1, which was increased by doses as low as 2 Gy. Most responses were rapid, peaking within 4-8 h, but antichymotrypsin and GFAP responses were delayed and still elevated at 24 h, by which time the others had subsided. Pretreatment of mice with dexamethasone or pentoxifylline suppressed radiation-induced gene expression, either partially or completely. Dexamethasone was more inhibitory than pentoxifylline at the doses chosen. CONCLUSIONS: The initial response of the brain to irradiation involves expression of inflammatory gene products, which are probably responsible for clinically observed early symptoms of brain radiotherapy. This mechanism explains the beneficial effects of the clinical use of steroids in such circumstances.

Animals↗
PubMed1995

Biologically effective dose distribution based on the linear quadratic model and its clinical relevance.

PURPOSE: Radiotherapy plans based on physical dose distributions do not necessarily entirely reflect the biological effects under various fractionation schemes. Over the past decade, the linear-quadratic (LQ) model has emerged as a convenient tool to quantify biological effects for radiotherapy. In this work, we set out to construct a mechanism to display biologically oriented dose distribution based on the LQ model. METHODS AND MATERIALS: A computer program that converts a physical dose distribution calculated by a commercially available treatment planning system to a biologically effective dose (BED) distribution has been developed and verified against theoretical calculations. This software accepts a user's input of biological parameters for each structure of interest (linear and quadratic dose-response and repopulation kinetic parameters), as well as treatment scheme factors (number of fractions, fractional dose, and treatment time). It then presents a two-dimensional BED display in conjunction with anatomical structures. Furthermore, to facilitate clinicians' intuitive comparison with conventional fractionation regimen, a conversion of BED to normalized isoeffective dose (NID) is also allowed. RESULTS: Two sample cases serve to illustrate the application of our tool in clinical practice. (a) For an orthogonal wedged pair of x-ray beams treating a maxillary sinus tumor, the biological effect at the ipsilateral mandible can be quantified, thus illustrates the so-called "double-trouble" effects very well. (b) For a typical four-field, evenly weighted prostate treatment using 10 MV x-rays, physical dosimetry predicts a comparable dose at the femoral necks between an alternate two-fields/day and four-fields/day setups. However, our BED display reveals an approximate 21% higher BED for the two-fields/day scheme. This excessive dose to the femoral necks can be eliminated if the treatment is delivered with a 3:2 (anterio-posterior/posterio-anterior (AP/PA): bilaterally opposed (BLO)) dose weighting. With Co-60 beams, the increase of BED with alternate two-fields/day, 1:1 setup was even more pronounced (26%). CONCLUSION: We have demonstrated the feasibility of constructing a biologically oriented dose distribution for clinical practice of radiotherapy. The discordance between physical dose distributions and the biological counterparts based on the given treatment schemes was quantified. The computerized display of BED at nonprescription points greatly enhanced the versatility of this tool. Although the routine use of this implementation in clinical radiotherapy should be cautiously done, depending largely on the accuracy of the published biological parameters, it may, nevertheless, help the clinicians derive an optimal treatment plan with a particular fractionation scheme or use it as a quantitative tool for outcome analysis in clinical research.

Feasibility Studies↗
PubMed1995

Adhesive interactions between alternatively spliced CD44 isoforms.

Alternative splicing of a series of 10 contiguous exons present within the CD44 gene can generate a large number of differentially expressed CD44 isoforms that contain additional peptide sequences of varying length inserted into a single site within the extracellular domain of the molecule proximal to the membrane spanning domain. Although distinct functions have been ascribed to certain of these isoforms, the effect of particular inserted domains on the ligand-binding specificity of the CD44 molecule remains unclear. In the present study, we demonstrate that while CD44H, the major CD44 isoform expressed on resting hemopoietic cells, and CD44R1, an alternatively spliced isoform present on transformed epithelial cells and certain activated and/or malignant hemopoietic cell types, can both bind avidly to hyaluronan, only CD44R1 can promote homotypic cellular aggregation when expressed in the CD44-negative murine lymphoma cell line TIL1. Experiments in which TIL1 cells transduced with different CD44 isoforms were tested for their ability to adhere to one another or to COS7 cells transfected with CD44R1, indicated that CD44R1 can recognize and bind a common determinant present on both CD44H and CD44R1. Monoclonal antibody blocking studies suggest further, that the determinant recognized by CD44R1 is located in a region of the CD44 molecule distinct from that involved in hyaluronan binding.

Alternative Splicing↗
PubMed1995

Down-regulation of murine fibrosarcoma transforming growth factor-beta 1 expression by interleukin 7.

BACKGROUND: Cytokine genes encode proteins that modulate immune system responses. Modification of tumor cells by the introduction of cytokine genes has been used as a strategy to augment host immunity. Interleukin 7 (IL-7) gene transfer enhances the immune response to tumor cells and can result in tumor regression. Transforming growth factor-beta 1 (TGF-beta 1) is a potent immunosuppressive cytokine produced by many tumors. We have previously reported that recombinant IL-7 decreases the expression of TGF-beta 1 by murine macrophages. PURPOSE: This study investigates the inhibition of tumor-derived TGF-beta 1 production as a possible mechanism for the enhanced antitumor immunity that accompanies IL-7 gene transfer. METHODS: A fibrosarcoma cell line (FSA-JmIL-7) genetically modified to produce IL-7 was used to evaluate the effects of IL-7 on tumor production of TGF-beta 1. The control cell line (FSA-Jneo) originated from the same parental fibrosarcoma cell line (FSA) and was produced by transduction with the same retroviral vector without the IL-7 gene. FSA-Jneo and FSA-JmIL-7 tumor cells were evaluated for the expression of TGF-beta 1 messenger RNA (mRNA). To determine if the observed change in TGF-beta 1 mRNA was associated with an alteration in protein secretion, we compared supernatants from tumor cell cultures for TGF-beta 1 production. Specific anti-TGF-beta 1 monoclonal antibody (MAb) was used to confirm the role of TGF-beta 1 in these assays. RESULTS: Compared with FSA parental and FSA-Jneo cells, FSA-JmIL-7 cells expressed TGF-beta 1 mRNA at a lower level. Compared with supernatants from FSA-Jneo cells, FSA-JmIL-7 supernatants contained consistently lower levels of TGF-beta 1 activity (P < .05). In addition, FSA-Jneo supernatants suppressed lymphocyte proliferation to a significantly greater degree than supernatants from FSA-JmIL-7 cells (P < .05). Studies with anti-TGF-beta 1 MAb added to the supernatants confirmed the role of TGF-beta 1 in inhibition of lymphocyte proliferation. CONCLUSION: These findings suggest that IL-7 gene transfer inhibits the production of TGF-beta 1 by tumor cells and thus may enhance the efficacy of the host's antitumor immune response. IMPLICATION: The regulation of endogenous tumor-derived cytokines in response to cytokine gene transfer may contribute to altered immune responses in the tumor microenvironment and thus may be an important additional parameter to assess in gene therapy.

Animals↗
PubMed1995

The effect of interleukin-1 beta or transforming growth factor-beta on radiation-impaired murine skin wound healing.

The ability of exogenous interleukin-1 beta (IL-1 beta) or transforming growth factor-beta (TGF-beta) to reverse radiation-induced defective wound healing was investigated. Mice were irradiated with 8.5 or 11 Gy to total body (TB), 12 or 16 Gy to hemibody (HB), or 20 or 26 Gy to skin alone immediately prior to surgical wounding in order to determine the effect of hematopoietic system depletion on cytokine action. A single dose of IL-1 beta or TGF-beta or vehicle control was applied to each wound. All radiation doses and types resulted in a deficit in wound healing when measured on Days 11 and 14. IL-1 beta enhanced wound tensile strength (WTS) in TB-irradiated mice, while TGF-beta enhanced WTS in HB-irradiated mice. Neither cytokine was effective at enhancing WTS in unirradiated or skin-only irradiated animals. In addition IL-1 beta and TGF-beta showed distinct differences in their effects on the kinetics of healing with time after wounding. The effects of TGF-beta appeared to be transient with compromise of the gain in WTS. The differences in the effects of these two cytokines in affecting wound healing reflect their involvement in different cellular events in the wound healing process.

Animals↗
PubMed1995

Single-dose compared with fractionated-dose radiation of the OM431 choroidal melanoma cell line.

PURPOSE: To compare single-dose and fractionated-dose radiotherapeutic effects on choroidal melanoma cells. METHODS: We determined the effects of gamma radiation on OM431 cell survival by exposing cells to either a single 9-Gy dose or two 4.5-Gy fractionated doses at intervals of 20 minutes to eight hours. The effects of single dosing and fractionated dosing at six hours were compared at doses of 2 to 12 Gy. RESULTS: Tumor cell repair was most rapid during the first two hours. Maximum repair had occurred by six hours after radiation. Cell survival curves showed doses greater than 3 Gy of single-dose gamma radiation resulted in a greater number of cells killed than did equivalent fractionated doses. CONCLUSIONS: Ocular melanoma in vitro is relatively radioresistant to low-dose fractionated radiotherapy. High single-dose radiotherapy would be more effective but would also result in more damage to normal tissue unless more focused modalities of radiotherapy are used.

Cell Survival↗
PubMed1995

Effects of gamma radiation on the OM431 human ocular melanoma cell line.

In order to determine the dose responsiveness to radiation of ocular melanoma, we conducted an in vitro dose-response study on a monolayer cell culture using a clonogenic assay. The effects on cell survival were determined relative to unirradiated controls. A human epithelioid ocular melanoma cell line, OM431, was maintained in tissue culture and serial dilutions of viable cells were plated in flasks, allowed to settle and attach for 48 h, and subsequently irradiated with 1-10 Gy in single fractions. After 2 weeks, the number of reproducing clones (forming colonies with greater than 32 cells or five generations) were counted. The surviving fractions of cells were plotted on a cell survival curve using the linear quadratic model. The survival curve showed a large initial shoulder followed by an exponential decline in growth. Our data suggest that the OM431 ocular melanoma cell line responds to irradiation in a manner similar to other melanoma cell lines and is relatively radioresistant especially at lower doses.

Cell Survival↗
PubMed1995

Radiotherapy for genes that cause cancer.

Many approaches to cancer gene radiotherapy are possible. Even existing strategies, devised with other goals in mind, can cause radiosensitization by altering the intrinsic radiosensitivity of tumour cells or by modifying the tumour microenvironment. Small increases in the levels of radiosensitization could, over a fractionated radiation course, have major effects on the probability of tumour cure. The clinical application of gene radiotherapy will require use of in vivo gene delivery systems that still need validation but, because radiation is effective at decreasing tumour burden, genes will not have to be expressed in all cells in order to achieve a cure.

Apoptosis↗
PubMed1995

Effect of nicotinamide and pentoxifylline on normal tissue and FSA tumor oxygenation.

Nicotinamide (NA) and pentoxifylline (PTX) sensitize experimental murine tumors to radiation without sensitizing normal tissues. They are presumed to exert this effect by reducing hypoxia in tumors. The present study evaluated the individual and combined effects of NA and PTX on oxygen levels in subcutaneous normal tissue and subcutaneous FSa fibrosarcoma tumors in the hind foot dorsum of C3H mice. Oxygen measurements were made using a polarographic needle electrode inserted into the tissue immediately before and/or 15-60 min after intraperitoneal administration of 500 mg/kg of NA, 50 mg/kg of PTX, or saline. The median tumor pO2 increased from a mean +/- S.E.M. of 4.1 +/- 1.1 mm Hg in saline-treated control mice to 6.8 +/- 1.9 mm Hg 15 min after NA, 7.6 +/- 1.4 mm Hg 60 min after PTX, and 6.7 +/- 1.1 mm Hg after NA and PTX in combination. PTX raised the median tumor pO2 level from 21% to 39% of the median subcutaneous normal tissue pO2 (p < 0.01). PTX also significantly reduced the proportion of tumor pO2 values < or = 2 mm Hg from 41 +/- 10% to 8 +/- 7% (p = 0.02). Although NA did increase the proportion of tumor that was well oxygenated, it did not significantly reduce the proportion of tumor pO2 values < or = 2 mm Hg (p = 0.34). The combination of NA and PTX did not add to the tumor oxygenation enhancement achieved by PTX alone. NA increased the median subcutaneous normal tissue pO2 by an average of 5.1 +/- 2.2 mm Hg from a baseline of 17.1 +/- 2.2 mm Hg (p = 0.04). PTX had no effect on the median normal tissue pO2 (p = 0.93). PTX showed greater therapeutic potential in this model system than did NA.

Analysis of Variance↗
PubMed1995

Modification of tumor microenvironment by cytokine gene transfer.

The tumor microenvironment is determined by the interactions between host and tumor cells, a process in which cytokines play a major role. We have used retroviral vectors to insert and express cytokine genes in tumor cells so as to induce predictable changes in the host cells that infiltrate tumors. This frequently caused changes in tumor cell phenotype through autocrine/intracrine pathways. We reasoned that cytokine-induced alterations in tumor cell phenotype and/or in infiltrating host cells might alter the in vitro and in vivo cellular response to irradiation. In the present paper we document some of the effects of expression of interleukin-6 (IL-6) and IL-7 genes in tumor cells in this regard. The studies support the hypothesis that cytokines may play a role in determining both intrinsic tumor radioresponsiveness and the tumor microenvironment and in these ways may influence in vivo tumor irradiation responses. Possible cytokine gene-mediated approaches to radiotherapy cancer are discussed.

Animals↗
PubMed1995

Postoperative irradiation impairs or enhances wound strength depending on time of administration.

Irradiation can complicate surgical wound healing, yet little is known of the importance of the time between surgery and irradiation on this process. This study investigated the impact of postoperative irradiation on gain in would tensile strength in a murine skin model. Irradiation on the same day as wounding or to 2-day-old wounds reduced wound tensile strength. In contrast, postoperative irradiation delivered at 7, 9 and 14 days transiently enhanced wound tensile strength, as measured 3 but not 4 or 5 weeks later. This effect was independent of the inclusion (hemibody) or exclusion (skin alone) of the hematopoietic system in the field of irradiation. Radiation-enhanced wound tensile strength was greater and occurred earlier after higher radiation doses. Even though the effect of irradiation in enhancing wound tensile strength is transitory, it could be important in assisting early wound healing.

Animals↗
PubMed1994

The extent, time course, and fraction size dependence of mouse spinal cord recovery from radiation injury.

PURPOSE: This experiment was designed to assess: (a) the influence of fraction size and time interval between fractions on the tolerance of the spinal cord to high cumulative doses of radiation; and (b) the influence of the long-term recovery process on the tolerance of the spinal cord to reirradiation. METHODS AND MATERIALS: The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily, a prolonged fractionated regimen of 1.2 Gy once daily, a hyperfractionated regimen of 1.2 Gy twice daily, or a single dose of 12 Gy followed 0-190 days later by a second dose of 5-20 Gy. Mice in the multifractionated regimen groups were given a single 15 Gy top-up dose 24 h after reaching a cumulative fractionated dose of 24-70 Gy. Hind limb strength was measured weekly for 2 years after the completion of irradiation. RESULTS: Paralysis occurred in a bimodal time distribution, with peaks at 5-10 months and 15-23 months after the completion of irradiation. The cumulative radiation dose was directly associated with the incidence of paralysis in each radiation schedule (p < 0.0001) and inversely associated with the time to onset of paralysis in the 1.2 Gy b.i.d. (p = 0.0001) and 2.0 Gy q.d. schedules (p = 0.03). The median latency of paralysis in each group was inversely associated with the incidence of paralysis in that group (p < 0.001). Decreasing the fraction size from 2.0 to 1.2 Gy once daily markedly increased the radiation tolerance of the spinal cord (p < 0.0001), consistent with a very small alpha-beta value of -0.30 Gy (approximately 95% confidence interval -0.72, +0.18) in the linear-quadratic model. Decreasing the time interval from 24 h to alternating 8 and 16 h periods produced an offsetting diminuation in cord tolerance (p < 0.0001). The 1.2 Gy once daily schedule resulted in ED20 and ED50 values that were approximately double those of the 2.0 Gy once daily and the 1.2 Gy twice daily schedules and a relative risk of paralysis from a given dose that was 0.03 times the risk associated with the other two regimens (p < 0.0001). There was no significant difference between the 2.0 Gy once daily and the 1.2 Gy twice daily dose-paralysis curves (p = 0.86). The residual from a single 12 Gy radiation dose was 17% after 190 days, leaving the retreatment ED50 only 10% below the ED50 of previously unirradiated spinal cord. The relative risk of paralysis after 12 Gy plus a second radiation dose decreased from 1.00 with no time interval between doses to 0.51-0.73 with a 0.25, 1 or 3 day interval, 0.32 with a 7 day interval, 0.11 with a 30 day interval, and 0.06 with a 190 day interval. CONCLUSION: The increased radiation tolerance of the murine spinal cord produced by decreasing the fraction size from 2.0 to 1.2 Gy was offset by the diminished tolerance produced by decreasing the time interval between fractions from 24 to 8-16 h, resulting in no significant difference in the dose-paralysis curves of conventional and hyperfractionated radiation schedules. The rodent spinal cord eliminates the majority of the occult radiation injury produced by a radiation dose equal to half the ED50 during the months following irradiation. This permits retreatment of previously irradiated spinal cord to high doses without the induction of myelopathy.

Animals↗
PubMed1994

Adenovirus-mediated gene transfer in the transplant setting. I. Conditions for expression of transferred genes in cold-preserved hepatocytes.

Transplantation of genetically modified hepatocytes has been suggested as a therapeutic modality for impaired hepatocellular function. This study examined adenoviral-mediated gene transfer to isolated hepatocytes, under conditions mimicking clinical transplant preservation. Isolated rat hepatocytes were infected using replication-defective adenoviral vectors with an expression cassette containing the beta-galactosidase gene driven by a CMV promoter. Hepatocytes were infected in suspension immediately after isolation, then either cultured or transplanted immediately into a syngeneic host. Gene transfer efficiency was assessed by histochemical staining and FACS analysis for the gene product. The presence of viral DNA and mRNA, as well as viral-derived protein production, were assayed. Efficiency of gene transfer was examined as a function of several preservation conditions. Infection efficiency was best in cells preserved in UW solution, correlated directly with virus:hepatocyte ratio and with length of exposure to virus. Successful infection resulted in significant viral-derived protein production, persisting for at least two weeks in culture. These results demonstrate the versatility of adenoviral vectors in accomplishing rapid and efficient gene transfer into nondividing hepatocytes during cold preservation. Such genetically modified hepatocytes have potential use for immediate transplantation, without the need for further manipulation.

Adenoviridae↗
PubMed1994

Radiosensitivity of ataxia-telangiectasia, X-linked agammaglobulinemia, and related syndromes using a modified colony survival assay.

We used a modified colony survival assay to measure the sensitivity to ionizing radiation of more than 50 lymphoblastoid cell lines from normal individuals and from patients with ataxia-telangiectasia, Nijmegen breakage syndrome variants, and X-linked agammaglobulinemia. All of these disorders are associated with an increased frequency of cancer. Lymphoblastoid cell lines from patients with ataxia-telangiectasia complementation groups A, C, D, and E; ATFresno; Nijmegen breakage syndrome variants V1 and V2; and X-linked agammaglobulinemia showed marked radiosensitivity, whereas ataxia-telangiectasia heterozygotes were similar to controls. Friedreich's ataxia is not associated with increased cancer risk; lymphoblastoid cell lines from two such patients showed normal radiosensitivity. Taken together, these results suggest that some forms of X-ray sensitivity and cancer susceptibility share a common mechanism, such as an enzyme that is necessary both for the repair of radiation damage to DNA and for gene rearrangements during V(D)J recombination.

Agammaglobulinemia↗
PubMed1994

Complications in the functional analysis of transfected MHC genes.

Analysis of the relationship between the structure of a protein molecule and its function often exploits the techniques of gene mutation and expression in transfected cell lines. This approach has been used extensively in the study of MHC molecules for testing predictions derived from structural models. Comparison of the functional properties of mutant molecules is difficult because MHC molecules interact with both peptides and T cell receptors. Functionality is commonly determined in biological assays which are dependent on T cell recognition of specific peptide/MHC complexes and measure secondary events triggered by T cell activation. In this study four L cell lines transfected with different combinations of alpha and beta chains from I-Ak and I-Au were used as antigen-presenting cells to activate two hen egg-white lysozyme-specific T cell clones. We compared several biological assays, namely, T cell proliferation, cytokine production, and cytotoxicity. Different assays indicated varying degrees of functionality for the same MHC molecule and thus demonstrated the difficulty in unambiguous interpretation of data from complex assays. Furthermore, we detected differences among the transfected lines which appeared unrelated to the expression of the introduced MHC genes.

Animals↗
PubMed1994

Tumor necrosis factor-alpha plays a central role in interleukin-2-induced pulmonary vascular leak and lymphocyte accumulation.

Administration of interleukin-2 (IL-2) leads to pulmonary vascular leak. This form of pulmonary edema has previously been postulated to be due to the in vivo induction of tumor necrosis factor-alpha (TNF-alpha). To determine whether TNF-alpha plays a role in IL-2-induced pulmonary vascular leak, we performed in situ hybridization of lung sections and reverse transcriptase-polymerase chain reaction of bronchoalveolar lavage macrophages from IL-2-challenged mice. The results confirm an in situ upregulation of TNF-alpha mRNA expression in the lungs associated with vascular leak. In addition, a significant increase in TNF-alpha protein production was found in the lung following IL-2 administration, as measured by TNF-alpha-specific ELISA of lung supernatants (P = 0.028). Intravenous administration of a soluble TNF receptor significantly diminished IL-2-induced pulmonary vascular leak (P = 0.006). These findings confirm a central role for TNF-alpha in mediating the pulmonary vascular leak associated with IL-2 toxicity.

Animals↗
PubMed1994

Inhibitory effect of locally produced and exogenous interleukin-6 on tumor growth in vivo.

In order to define the potential antitumor activity of the multifunctional cytokine interleukin-6 (IL-6), retrovirus-mediated gene transfer was used to introduce and express a cDNA encoding human IL-6 in the murine fibrosarcoma cell line Fsa-R. Although these genetically modified tumor cells appeared morphologically and phenotypically identical to control Fsa-R cells and had a similar plating efficiency in vitro, they were found to exhibit greatly reduced tumorigenicity in vivo following intravenous injection into syngeneic recipients. Exogenous IL-6 was shown to produce a similar inhibition of tumor growth in the lung if administered intraperitoneally. In contrast, tumor growth in subcutaneous sites was inhibited only if the tumor cells were engineered to express IL-6 locally, or if IL-6 was administered intratumorally. Intraperitoneal injection of IL-6 had no inhibitory effect. Tumors that did grow from IL-6-producing tumor cell inocula in subcutaneous sites were found to contain large numbers of macrophages. These results demonstrate that the antitumor activity of systemically administered IL-6 varies depending on the site of tumor growth and suggest an important role for IL-6 in the recruitment, proliferation and/or survival of tumor-associated macrophages.

Animals↗