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M R White

Publications and source records attributed to M R White.

At least 37 records · Page 2Linked to original sources
PubMed2000

Functional analysis of the human MCL-1 gene.

We have isolated a 6.5-kb human genomic fragment that encodes the MCL-1 gene. Comparison of the coding region with the published full-length cDNA reveals that the gene contains three exons and two introns, and that our clone contains 370 bp of the 3'-untranslated region. We have mapped a major transcriptional start site to 80 residues upstream of the translation initiation codon. Reporter gene assays indicate that regulatory sequences responsible for phorbol ester (PMA)-stimulated activity and granulocyte-macrophage-colony-stimulating factor (GM-CSF)-stimulated activity were located within the first 294 bp of the 5'-flanking region upstream from the transcription start site. A deletion mutant was generated that lacked 47 bp between residues --215 and -- 168: in this mutant, six out of seven GGCCCC repeats and two GCTCA repeats were deleted. Serum-stimulated and GM-CSF-stimulated reporter activity were greatly decreased in this deletion mutant and PMA-stimulated activity was slightly decreased. While the coding and 3'-untranslated regions of the human and mouse genes have significant sequence similarity, there was very little sequence similarity in the 5'-flanking regions of the genes from these two species. Nevertheless, some consensus sequences for a number of transcription-factor-binding sites were detected in the two genes, indicating that transcription may be regulated by similar signalling pathways in these different species.

Amino Acid Sequence↗
PubMed2000

Inhibition of denitrification by ultraviolet radiation.

It has been shown that UV-A (lambda=320-400 nm) and UV-B (lambda=280-320 nm) inhibit photosynthesis, nitrogen fixation and nitrification. The purpose of this study was to determine the effects, if any, on denitrification in a microbial community inhabiting the intertidal. The community studied is the microbial mat consisting primarily of Lyngbya that inhabits the Pacific marine intertidal, Baja California, Mexico. Rates of denitrification were determined using the acetylene blockage technique. Pseudomonas fluorescens (ATCC #17400) was used as a control organism, and treated similarly to the mat samples. Samples were incubated either beneath a PAR transparent, UV opaque screen (OP3), or a mylar screen to block UV-B, or a UV transparent screen (UVT) for 2 to 3 hours. Sets of samples were also treated with nitrapyrin to inhibit nitrification, or DCMU to inhibit photosynthesis and treated similarly. Denitrification rates were greater in the UV protected samples than in the UV exposed samples the mat samples as well as for the Ps fluorescens cultures. Killed controls exhibited no activity. In the DCMU and nitrapyrin treated samples denitrification rates were the same as in the untreated samples. These data indicate that denitrification is directly inhibited by UV radiation.

Ammonia↗
PubMed2000

Choline is required by tilapia when methionine is not in excess.

Choline is essential in diets fed to most young vertebrates, but previous studies did not confirm the essentiality of choline in diets fed to tilapia. Two experiments were conducted to evaluate the essentiality of dietary choline in such diets. The basal diet used in both experiments contained 32 g crude protein/100 g diet (10.1 g crude protein from casein and gelatin, and 21.9 g from a crystalline L-amino acid mixture). The total sulfur amino acid (TSAA) concentration of the basal diet was 0.28 g/100 g diet, Met:Cys 89:11. In Experiment 1, a 4x2 design was used in which crystalline L-methionine was added to the basal diet resulting in four levels of TSAA (0.28, 0.50, 0.75 or 1.0 g/100 g diet, Met:Cys 89:11, 94:6, 96:4, or 97:3, respectively). At each level of TSAA, diets also contained either 0 or 1 g choline/kg diet supplied as choline chloride. Weight gain, feed efficiency (FE) and serum methionine concentrations were significantly affected by dietary TSAA concentration, but not by dietary choline concentration or the interaction between TSAA and choline. Weight gain, feed efficiency and serum methionine concentrations indicated that the TSAA requirement was 0.5 g/100 g diet. In the second experiment, diets were formulated to contain either 0.28 or 0.5 g TSAA/100 g diet, Met:Cys 89:11 or 94:6, respectively, and graded levels of choline ranging from 1 to 4 g/kg diet in gradations of 1 g/kg. Dietary methionine significantly affected weight gain and FE, whereas dietary choline significantly affected weight gain, FE and survival, and the interaction of methionine and choline significantly affected weight gain. Fish fed diets containing 0.5 g TSAA/100 g diet and 3 g choline chloride/kg diet exhibited the highest weight gain, feed efficiency and survival. On the basis of these data, it seems clear that juvenile tilapia require choline in certain dietary formulations.

Analysis of Variance↗
PubMed2000

Enhanced anti-influenza activity of a surfactant protein D and serum conglutinin fusion protein.

We previously demonstrated that bovine serum conglutinin has markedly greater ability to inhibit influenza A virus (IAV) infectivity than other collectins. We now show that recombinant conglutinin and a chimeric protein containing the NH(2) terminus and collagen domain of rat pulmonary surfactant protein D (rSP-D) fused to the neck region and carbohydrate recognition domain (CRD) of conglutinin (termed SP-D/Cong(neck+CRD)) have markedly greater ability to inhibit infectivity of IAV than wild-type recombinant rSP-D, confirming that the potent IAV-neutralizing activity of conglutinin resides in its neck region and CRD. Furthermore, by virtue of incorporation of the NH(2) terminus and collagen domain of SP-D, SP-D/Cong(neck+CRD) caused substantially greater aggregation of IAV particles and enhancement of neutrophil binding of, and H(2)O(2) responses to, IAV than recombinant conglutinin or recombinant rSP-D. Hence, SP-D/Cong(neck+CRD) combined favorable antiviral and opsonic properties of conglutinin and SP-D. This study demonstrates an association of specific structural domains of SP-D and conglutinin with specific functional properties and illustrates that antimicrobial activities of wild-type collectins can be enhanced through recombinant strategies.

Animals↗
PubMed1999

Influenza A virus accelerates neutrophil apoptosis and markedly potentiates apoptotic effects of bacteria.

Neutrophils are recruited into the airway in the early phase of uncomplicated influenza A virus (IAV) infection and during the bacterial superinfections that are a significant cause of morbidity and mortality in IAV-infected subjects. In this report, we show that IAV accelerates neutrophil apoptosis. Unopsonized Escherichia coli had similar effects, although apoptotic effects of opsonized E coli were greater. When neutrophils were treated with both IAV and unopsonized E coli, a marked enhancement of the rate and extent of neutrophil apoptosis occurred as compared with that caused by either pathogen alone. Treatment of neutrophils with IAV markedly increased phagocytosis of E coli. Simultaneous treatment of neutrophils with IAV and E coli also elicited greater hydrogen peroxide production than did either pathogen alone. IAV increased neutrophil expression of Fas antigen and Fas ligand, and it also increased release of Fas ligand into the cell supernatant. These findings may have relevance to the understanding of inflammatory responses to IAV in vivo and of bacterial superinfection of IAV-infected subjects.

Apoptosis↗
PubMed1999

Edible mushroom (Agaricus bisporus) lectin, which reversibly inhibits epithelial cell proliferation, blocks nuclear localization sequence-dependent nuclear protein import.

The Galbeta1-3GalNAcalpha (TF antigen)-binding lectin (ABL) from the common edible mushroom (Agaricus bisporus) has a potent anti-proliferative effect without any apparent cytotoxicity. This unusual combination of properties prompted investigation of its mechanism of action. In contrast to soluble lectin, agarose-immobilized, and hence noninternalizable ABL had no effect on proliferation of HT29 colon cancer cells. Electron microscopy of HT29 cells incubated with fluorescein- and gold-conjugated ABL showed internalization of the lectin into endocytotic vesicles and multivesicular bodies. Confocal microscopy showed perinuclear accumulation of fluorescein isothiocyanate-conjugated lectin, which also inhibits HT29 cell proliferation, raising the possibility that the lectin might interfere with nuclear pore function. Transport of heat shock protein 70 into the nucleus in response to heat shock was blocked by preincubation of HT29 cells for 6 h with 40 micrograms/ml ABL. In digitonin-permeabilized cells, nuclear uptake of bovine albumin conjugated to a nuclear localization sequence (NLS)-containing peptide was also inhibited by a 15-min preincubation with 40-100 micrograms/ml ABL. In contrast, serum-stimulated nuclear translocation of mitogen-activated protein kinase, which is NLS-independent, was not affected by pretreatment of cells with the lectin. These results suggest that the anti-proliferative effect of ABL is likely to be a consequence of the lectin trafficking to the nuclear periphery, where it blocks NLS-dependent protein uptake into the nucleus.

Adult↗
PubMed1999

Influenza A virus up-regulates neutrophil adhesion molecules and adhesion to biological surfaces.

Influenza A virus (IAV) binds to sialylated neutrophil surface components (e.g., CD43 and sialyl Lewisx antigen) and induces both activation and functional depression of neutrophils. We report that IAV enhanced neutrophil adhesion to surfaces coated with serum or serum components, but not to uncoated plastic. IAV up-regulated expression of integrins (CD11b and CD11c) and carcinoembryonic-related antigens on neutrophils, while reducing expression of CD43, L-selectin, and P-selectin glycoprotein ligand (PSGL). Although treatment of neutrophils with elastase or Osialoglycoprotease decreased surface CD43 and PSGL, they did not reduce binding of IAV to neutrophils, implying that IAV can bind to alternate binding sites in the absence of CD43. Pretreatment of neutrophils with elastase also did not prevent IAV from increasing expression of integrins and enhancing adhesion. Up-regulation of adhesion molecules and adhesion are important, previously unrecognized, features of neutrophil activation by IAV. Further studies will be needed to clarify the mechanism of these effects.

Animals↗
PubMed1999

Controlling denitrification in closed artificial ecosystems.

Denitrification, the dissimilatory reduction of NO3- to N2O and N2, is found in a wide variety of organisms. In closed artificial systems, especially closed plant growth chambers, a significant loss of fixed-N occurs through denitrification, thereby decreasing the efficiency of the system and fouling the atmosphere with N2O. Denitrification is a form of anaerobic respiration. Whenever available, however, denitrifiers preferentially use O2 as their terminal electron acceptor. As a result, rates of denitrification and growth are a function of O2. Typically, in closed systems O2 consumption is greater than the diffusion of O2 through the medium to the cell, decreasing the O2 level near the cell and denitrification occurs. Using Pseudomonas fluorescens (ATCC # 17400) as a model organism grown in a two L bioreactor under varying levels of O2 we studied its effects on population growth and its ability to mitigate denitrification in closed systems. The results indicate that denitrification occurs in a closed system even when it is considered aerobic, that is well mixed and sparged with either air, or sufficient pure O2 to cause a complete turnover in the gaseous atmosphere in the bioreactor vessel every five minutes.

Air Conditioning↗
PubMed1999

Necropsy and histopathologic findings in 14 African hedgehogs (Atelerix albiventris): a retrospective study.

From fiscal years 1992 through 1996, 14 African hedgehog (Atelerix albiventris) cases were submitted to the Animal Disease Diagnostic Laboratory at Purdue University. The most common diagnoses were splenic extramedullary hematopoiesis (91%), hepatic lipidosis (50%), renal disease (50%), and neoplastic disease (29%). Other less frequent necropsy findings were myocarditis (21%), colitis (14%), bacterial septicemia (14%), and pneumonia (14%). The data indicate that splenic extramedullary hematopoiesis, hepatic lipidosis, renal disease, and neoplasms are frequent postmortem findings in hedgehogs.

Age Distribution↗
PubMed1998

Real-time imaging of gene expression in single living cells.

Recent advances in reporter gene technologies are now allowing us to image gene transcription at the single cell level, using either fluorescence or luminescence microscopy. Here, the basis of these techniques is outlined and their advantages and disadvantages in various biological systems are discussed.

Animals↗
PubMed1998

Pulmonary surfactant proteins A and D enhance neutrophil uptake of bacteria.

The collectins are a class of collagenous lectin proteins present in serum and pulmonary secretions [pulmonary surfactant protein (SP) A and SP-D] that are believed to participate in innate immune responses to various pathogens. With the use of flow cytometric and fluorescent-microscopic assays, SP-A and SP-D were shown to increase calcium-dependent neutrophil uptake of Escherichia coli, Streptococcus pneumoniae, and Staphylococcus aureus. Evidence is provided that the collectins enhanced bacterial uptake through a mechanism that involved both bacterial aggregation and direct actions on neutrophils. The degree of multimerization of SP-D preparations was a critical determinant of both aggregating activity and potency in enhancing bacterial uptake. The mechanisms of opsonizing activity of SP-D and SP-A differed in important respects from those of opsonizing antibodies. These results provide the first evidence that surfactant collectins may promote neutrophil-mediated clearance of bacteria in the lung independently of opsonizing antibody.

Animals↗
PubMed1998

Dynamic changes in prolactin promoter activation in individual living lactotrophic cells.

The firefly luciferase gene has become widely used as a convenient reporter for studies of gene promoter regulation. Very recently, the development of ultralow-light imaging cameras has enabled the quantitative digital imaging of light signals resulting from luciferase activation in the presence of luciferin substrate. We have applied this technology to the study of PRL promoter activation in individual pituitary tumor cells to study the temporal and spatial characteristics of the expression of a well-characterized pituitary hormone gene. Rat pituitary GH3 cells were transfected by lipofection with a luciferase reporter gene linked to 5000 bp from the human PRL gene 5'-flanking region. A series of stably transfected cell clones were generated, and one of these was chosen for detailed study on the basis of appropriate regulation of high-level luciferase expression by a series of known stimuli including TRH, forskolin, the calcium channel agonist Bay K8644, and basic fibroblast growth factor (bFGF). These cells were subjected to direct imaging of luciferase activity using a Hamamatsu photon-counting camera linked to a Zeiss Axiovert microscope with an Argus-50 image processor. Cells were exposed to 1 mM luciferin, and images were integrated over 30-min periods for up to 72 h. The total photon count over a given field settled to steady levels within 10 h and then remained constant for over 55 h. Addition of forskolin, TRH, or bFGF increased the total photon count of fields of 20-100 cells by 2- to 4-fold consistent with previous data from transient expression assays using the human PRL promoter. Individual cells, on the other hand, showed marked marked temporal and spatial heterogeneity and variability of luciferase expression when studied at 3-h intervals. Unstimulated cells showed variable luciferase expression with up to 40-fold excursions in photon counts per single cell area within 12-h periods. Stimulation of cells with either TRH, forskolin, or bFGF resulted in smooth increases in photon output over fields of 20-100 cells, but again individual cell responses differed widely, with some cells showing slow progressive rises in photon output, others showing phasic or transient responses, and yet others showing no response. In conclusion, we found a surprising degree of heterogeneity and temporal variability in the level of gene expression in individual living pituitary tumor cells over long periods of time, with markedly divergent responses to hormonal or intracellular stimulation. The use of stably transfected clonal cell lines with extended periods of reporter gene imaging offers a valuable insight into control of gene expression in living cells in real time.

Animals↗
PubMed1998

Hospitalization rates of tuberculosis in U.S. Navy enlisted personnel: a 15-year perspective.

The epidemiology of tuberculosis in this country is changing because of a combination of biological and social factors. The recent use of DNA fingerprinting of Mycobacterium tuberculosis using restriction-fragment-length polymorphism analysis has suggested that nearly one-third of new cases of tuberculosis being reported in a large metropolitan city is a result of recent infection. The immunosuppression of individuals with the human immunodeficiency virus and the prevalence of multiple drug-resistant tuberculosis has resulted in a renewed interest in the epidemiology and prevention of this disease. To determine the magnitude of the problem in the U.S. Navy enlisted population, a computer search of more than one million inpatient hospitalization records from January 1980 to December 1994 was performed. Total first hospitalization rates for all cases of tuberculosis during this period ranged from 2.2 per 100,000 person-years at risk in white females to 27.5 per 100,000 person-years in males, race "other" (includes mostly Filipinos and Asian-Americans). First hospitalization rates across all cases of tuberculosis declined during this period from a high of 8.7 per 100,000 in 1980 to a low of 2.2 per 100,000 in 1994.

Adult↗
PubMed1997

Mechanisms of anti-influenza activity of surfactant proteins A and D: comparison with serum collectins.

The present study provides the first direct comparison of anti-influenza A virus (IAV) activities of the collectins surfactant protein (SP) A and SP-D, mannose-binding lectin (MBL), and conglutinin. SP-D, MBL, and conglutinin inhibited IAV hemagglutination activity with a greater potency than and by a distinct mechanism from SP-A. Although isolated trimeric SP-D carbohydrate recognition domains inhibited hemagglutination activity, preparations of SP-D also containing the collagen domain and NH2 terminus caused greater inhibition. In contrast to SP-A (or nonmultimerized SP-D), absence of the N-linked attachment did not effect interactions of multimerized SP-D with IAV. SP-D, SP-A, and conglutinin caused viral precipitation through formation of massive viral aggregates, whereas MBL formed aggregates of smaller size that did not precipitate. All of the collectins enhanced IAV binding to neutrophils; however, in the case of MBL, this effect was modest compared with the binding enhancement induced by SP-D or conglutinin. These studies clarify the structural requirements for viral inhibition by SP-D and reveal significant differences in the mechanisms of anti-IAV activity among the collectins.

Animals↗