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Biomedical subjects

B Howard

Publications and source records attributed to B Howard.

At least 19 recordsLinked to original sources
PubMed1998

Structural and functional changes in proteins induced by free radical-mediated oxidative stress and protective action of the antioxidants N-tert-butyl-alpha-phenylnitrone and vitamin E.

The free radical theory of aging proposes that reactive oxygen species (ROS) cause oxidative damage over the lifetime of the subject. It is the cumulative and potentially increasing amount of accumulated damage that accounts for the dysfunctions and pathologies seen in normal aging. We have previously demonstrated that both normal rodent brain aging and normal human brain aging are associated with an increase in oxidative modification of proteins and in changes in plasma membrane lipids. Several lines of investigation indicate that one of the likely sources of ROS is the mitochondria. There is an increase in oxidative damage to the mitochondrial genome in aging and a decreased expression of mitochondrial mRNA in aging. We have used a multidisciplinary approach to the characterization of the changes that occur in aging and in the modeling of brain aging, both in vitro and in vivo. Exposure of rodents to acute normobaric hyperoxia for up to 24 h results in oxidative modifications in cytosolic proteins and loss of activity for the oxidation-sensitive enzymes glutamine synthetase and creatine kinase. Cytoskeletal protein spin labeling also reveals synaptosomal membrane protein oxidation following hyperoxia. These changes are similar to the changes seen in senescent brains, compared to young adult controls. The antioxidant spin-trapping compound N-tert-butyl-alpha-phenylnitrone (PBN) was effective in preventing all of these changes. In a related study, we characterized the changes in brain protein spin labeling and cytosolic enzyme activity in a series of phenotypically selected senescence-accelerated mice (SAMP), compared to a resistant line (SAMR1) that was derived from the same original parents. In general, the SAM mice demonstrated greater oxidative changes in brain proteins. In a sequel study, a group of mice from the SAMP8-sensitive line were compared to the SAMR1-resistant mice following 14 days of daily PBN treatment at a dose of 30 mg/kg. PBN treatment resulted in an improvement in the cytoskeletal protein labeling toward that of the normal control line (SAMR1). The results of these and related studies indicate that the changes in brain function seen in several different studies may be related to the progressive oxidation of critical brain proteins and lipids. These components may be critical targets for the beneficial effects of gerontotherapeutics both in normal aging and in disease of aging.

Adult↗
PubMed1997

Cytokines and particle-induced inflammatory cell recruitment.

The inflammatory response is a key component of host defense. However, excessive or persistent inflammation can contribute to the pathogenesis of disease. Inflammation is regulated, in part, by cytokines, which are small, typically glycosylated proteins that interact with membrane receptors to regulate cellular processes such as proliferation, differentiation, and secretion. During the past 10 years studies in humans and experimental animals have demonstrated that a cytokine called tumor necrosis factor alpha (TNF-alpha) plays a key role in the initiation of inflammatory responses in the lung and other tissues, including inflammation resulting from inhalation of noxious particles. There is now compelling evidence that one of the pathways by which inhaled particles stimulate the recruitment and subsequent activation of inflammatory cells is through the activation of lung macrophages to release TNF-alpha. TNF-alpha then acts via paracrine and autocrine pathways to stimulate cells to release other cytokines known as chemokines, which are directly chemotactic to leukocytes and other cells that participate in inflammatory and wound healing responses. In addition to a TNF-alpha-mediated pathway, there is growing evidence that some particles such as quartz and crocidolite can directly activate lung epithelial cells to release chemokines such as macrophage inflammatory protein-2, cytokine-induced neutrophil chemoattractant, and interleukin-8. A direct stimulatory effect of particles on lung epithelium may represent an additional or alternate pathway by which inhaled particles may elicit inflammation in the lung. Recent studies have suggested that oxidative stress may be a component of the mechanism by which particles activate cytokine production in cells such as macrophages and epithelial cells. The contribution of oxidative stress to particle-induced cytokine gene expression appears to be mediated, at least in part, through activation of the transcription factor nuclear factor kappa B.

Animals↗
PubMed1997

Asbestos causes translocation of p65 protein and increases NF-kappa B DNA binding activity in rat lung epithelial and pleural mesothelial cells.

The mechanisms of cell signaling and altered gene expression by asbestos, a potent inflammatory, fibrogenic, and carcinogenic agent, are unclear. Activation of the transcription factor, nuclear factor (NF)-kappa B, is critical in up-regulating the expression of many genes linked to inflammation and proliferation. Inhalation models of crocidolite- and chrysotile-induced inflammation and asbestosis were used to study the localization of p65, a protein subunit of the NF-kappa B transcription factor, in sham control rats and those exposed to asbestos. In addition, we investigated, using electrophoretic mobility shift analysis, whether in vitro exposure of rat lung epithelial cells and rat pleural mesothelial cells to asbestos increased binding of nuclear proteins, including p65, to the NF-kappa B DNA response element. Furthermore, translocation of p65 into the nucleus was determined by confocal microscopy. In comparison with sham animals, striking increases in p65 immunofluorescence were observed in airway epithelial cells of rats at 5 days after inhalation of asbestos. These increases were diminished by 20 days, the time period necessary for development of fibrotic lesions. In contrast, although inter-animal variability was observed, immunoreactivity for p65 was more dramatic in the interstitial compartment of asbestos-exposed rat lungs at both 5 and 20 days. Changes in p65 expression in pleural mesothelial cells exposed to asbestos in inhalation experiments were unremarkable. Exposure to asbestos also caused significant increases in nuclear protein complexes that bind the NF-kappa B consensus DNA sequence in both rat lung epithelial and rat pleural mesothelial cells. Using confocal microscopy, we observed partial nuclear translocation of p65 in rat pleural mesothelial cells exposed to asbestos. This partial response contrasted with the effects of lipopolysaccharide, which caused rapid and complete translocation of p65 from cytoplasm to nucleus. Our studies are the first to show the presence of the NF-kappa B system in lung tissue and evidence of activation in vitro and in vivo after exposure to a potent inflammatory, fibrinogenic, and carcinogenic environmental agent.

Animals↗
PubMed1997

Hematologic and serum biochemical and electrolyte values in clinically normal domestically bred rhesus monkeys (Macaca mulatta) according to age, sex, and gravidity.

Age, sex, and gravidity significantly affect blood values in rhesus monkeys (Macaca mulatta). The objective of the study reported here was to provide clinicians and researchers with complete blood values for clinically normal, domestically reared rhesus monkeys of Indian origin and of different age, sex, and gravidity. Values were obtained from 527 healthy, domestically bred and reared rhesus monkeys at The University of Texas M. D. Anderson's Department of Veterinary Sciences, Bastrop, Texas. Because standardized reference values are vital when dealing with the healthcare of a breeding population of rhesus monkeys, it is imperative to have a comprehensive set of reference serum biochemical and hematologic values based on sex, age, and gravidity to determine the overall health status of an individual monkey or a colony used for breeding or research. Establishing reference values allows accurate interpretation of biochemical and hematologic values for normal, subclinical, or clinically ill animals.

Aging↗
PubMed1996

The SV40 large T antigen and adenovirus E1a oncoproteins interact with distinct isoforms of the transcriptional co-activator, p300.

p300 is a nuclear phosphoprotein likely to be involved in the control of cell growth. Here we show that SV40 large T antigen (Tag) forms a specific complex with p300. In various Tag-expressing cell lines, the affinity of Tag for p300 was restricted to a newly identified unphosphorylated but ubiquitinated form of the protein. Further, Tag did not associate with p300 in an SV40 Tag-producing cell line (REV2) in which the original transformed phenotype (SV52) is reverted. Biochemical studies demonstrate that both the phosphorylation and the ubiquitination profile of p300 are altered in REV2 with respect to the wild-type fully transformed SV52 parental cells, wherein Tag-p300 complexes are readily detected. In contrast to Tag, the adenovirus early expression product E1a interacts with both phosphorylated and unphosphorylated forms of p300. In addition, when REV2 cells were infected with adenovirus, E1a-p300 complexes were detected, suggesting that the p300 expressed in REV2 has lost the affinity for Tag, but not for E1a. We then compared the ability of Tag and E1a to affect the transcription levels of the cAMP-responsive promoter (CRE), which is modulated in vivo by p300, in REV2 cells. We found that Tag repressed the CRE promoter in all of the cell lines in which Tag-p300 complexes were detected, but not in REV2 cells. In contrast, E1a efficiently inhibited CRE-directed transcription in this cell line. The data thus indicate that the different specificities exhibited by Tag and E1a towards the various forms of p300 are reflected in vivo as a difference in the ability of these viral oncoproteins to modulate the expression of CRE-containing genes.

Adenovirus E1A Proteins↗
PubMed1996

Adenoviral gene transfer of macrophage inflammatory protein-2 in rat lung.

Replication-defective adenoviral vectors are capable of localized transfer and expression of incorporated gene product in lung tissue. We have constructed an adenoviral vector that expresses rat macrophage inflammatory protein (MIP)-2, a C-X-C chemokine specifically chemotactic for neutrophils, Supernatants from 293 cells, infected with the adenoviral MIP-2 (ADMIP-2) construct, showed potent chemotactic activity and the ability of the ADMIP-2 vector to transcribe and make functional protein was confirmed. In vivo analysis of bronchoalveolar lavage fluid from rats after intratracheal instillation of ADMIP-2 (10(9) plaque-forming units) showed a 10-fold increase in the absolute number of neutrophils in bronchoalveolar lavage fluid as opposed to rats treated with an equal titer of an E1-disabled control virus expressing firefly luciferase (ADCA-18). Neutrophils constituted 65% of total BAL cells with alveolar macrophages being the other major cell type recovered. Rat MIP-2 protein was increased (nanograms per milliliter) in bronchoalveolar lavage fluid over a period of 7 days in ADMIP-2-treated animals. MIP-2 mRNA was demonstrated by Northern blot analysis in lung tissue, and histological analysis confirmed the presence of massive localized tissue neutrophilia. Evidence of chronic tissue injury and repair (ie, fibrosis) was not detected up to 2 weeks after the neutrophil infiltrate had resolved, subsequent to decreased chemokine presence. Adenoviral gene transfer proved an effective tool for the assessment of lung tissue expression of this chemokine in vivo and is useful in developing rodent models of tissue neutrophilia.

Adenoviridae↗
PubMed1994

Retrovirus-mediated gene transfer of the human gamma-IFN gene: a therapy for cancer.

A retroviral vector-mediated gene transfer system was used to introduce m gamma-IFN and h gamma-IFN genes into mouse and human tumor cells, respectively. Murine tumor cell lines and primary human melanoma tumor cells were successfully transduced with gamma-IFN vector, and these transduced cells secreted measurable levels of biologically active m gamma-IFN and h gamma-IFN, respectively. Both murine and human tumor cell lines that expressed gamma-IFN exhibited increased surface expression of HLA class I antigens when tested by Western blot and FACS analysis. gamma-IFN--transduced human melanoma cells were more active in stimulating tumor-specific cytolytic activity of CTLs from melanoma patients in vitro. m gamma-IFN--transduced tumor cells were substantially less tumorigenic than the corresponding parent tumor cell lines in immune-competent mice. In addition, injection of m gamma-IFN--transduced tumor cells resulted in activation of tumor-specific CTL in vivo. We plan to use gamma-IFN--transduced autologous tumor cells to boost host immune responses as a potential therapy for human melanoma.

Animals↗
PubMed1994

Effect of parathyroid hormone-related peptide supplementation of soy protein formulas in the neonatal pig model.

PTH-related peptide (PTHrP) is found in all milks, including human and pig. To define a role for PTHrP in milk, 2-day-old piglets were randomized to receive soy formula devoid of PTHrP or supplemented with 1 nM synthetic PTHrP(1-86) (n = 8 per group). The number of serum samples with detectable PTHrP by immunoassay (Incstar) and radiometric assay (Nichols) was 9 of 33 and 3 of 13 in PTHrP- and 8 of 27 and 3 of 15 in PTHrP+ formula-fed piglets and 8 of 14 and 7 of 12 in naturally suckling piglets, respectively. Serum and urine concentrations of calcium and magnesium and total and bone alkaline phosphatase were similar in both groups at 3, 6, 10, and 17 days of age. No differences were seen in bone mineral content of the tibia measured by single-photon absorptiometry (BMC 0.22 +/- 0.06 and 0.22 +/- 0.10) or dual x-ray absorption (BMC 1.43 +/- 0.36 and 1.31 +/- 0.78) either in vivo or on excised bone or by measurement of Ca, Mg, or P content or total bone ash (1.26 +/- 0.26 and 1.38 +/- 0.28 mg). Intestinal histology, serum intestinal alkaline phosphatase, and net absorption and retention of Ca, Mg, and P in balances from age 11-17 days were all similar. As in humans, however, a developmental pattern was seen for phosphorus regulation in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

A move from hospital to community-based homes for people with learning disabilities: activities outside the home.

Eighteen people with learning disabilities who moved from hospital to community-based homes were compared with a matched group of 18 who did not. A week-long time budget diary was used to record each occasion that the person left their home, the people accompanying them on each trip, their mode of transport and their destination. The diary was completed before they left the hospital and was repeated at least 1 year later. There was a strong correlation between the number of trips made from hospital wards at baseline and the number made at follow-up in both groups. Moving from the hospital had no significant effect on the number of trips made, but it did change their nature. Movers made more trips to unsegregated facilities; they made fewer trips alone and more in groups which included both staff and residents.

Activities of Daily Living↗
PubMed1993

Relative mitogenic activities of wild-type and retinoblastoma binding-defective SV40 T antigens in serum-deprived and senescent human diploid fibroblasts.

A novel gene transfer approach was used to investigate whether the retinoblastoma (Rb)-binding domain of simian virus 40 (SV40) T antigen is required for efficient T antigen-mediated stimulation of DNA synthesis is quiescent or senescent human embryo fibroblasts. In senescent cells, comparison between wild-type T antigen and a mutant defective in Rb binding (Glu-107-->Lys) revealed the latter to have approximately 15-fold lower activity. In contrast, comparison of wild-type and Rb- T antigens in serum-deprived quiescent cells revealed a much smaller (1.8-fold) difference. Surprisingly, an 18-fold differential could be induced by treating quiescent cells with the differentiating agent sodium butyrate. These results suggest that the role of Rb in control of the cell cycle is strongly dependent on the physiological state of the cell and the mechanism of growth arrest.

Antigens, Polyomavirus Transforming↗
PubMed1992

Congenital pseudarthrosis.

Five cases of congenital pseudarthrosis of the clavicle were treated with open reduction and fixation with appropriate-sized contoured plates and screws. Iliac bone grafts were used to bridge the gap in four patients; local bone graft was used in the fifth patient. Consolidation was noted an average of 3 months postoperatively in all five cases. The plate and screws were removed in all patients at an average of 16 months postoperatively. Average length of follow-up for the five patients is 4 years. Roentgenograms demonstrate that the clavicle has continued to grow normally. All five patients have pain-free full range of motion and are engaged in unrestricted activities.

Bone Plates↗
PubMed1992

A patient with Werner's syndrome and osteosarcoma presenting as scleroderma.

Werner's syndrome (WS) is often mistaken for scleroderma. We describe a patient with WS who presented with an enlarging, painful mass of the right knee that proved to be a juxtaarticular osteosarcoma of the distal femur. Recognition of WS and prompt investigation of any painful, enlarging masses to exclude sarcomatous degeneration will benefit these patients.

Bone Neoplasms↗