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Biomedical subjects

D E Brown

Publications and source records attributed to D E Brown.

At least 19 recordsLinked to original sources
PubMed2006

Global gene expression during nitrogen starvation in the rice blast fungus, Magnaporthe grisea.

Efficient regulation of nitrogen metabolism likely plays a role in the ability of fungi to exploit ecological niches. To learn about regulation of nitrogen metabolism in the rice blast pathogen Magnaporthe grisea, we undertook a genome-wide analysis of gene expression under nitrogen-limiting conditions. Five hundred and twenty genes showed increased transcript levels at 12 and 48 h after shifting the fungus to media lacking nitrate as a nitrogen source. Thirty-nine of these genes have putative functions in amino acid metabolism and uptake, and include the global nitrogen regulator in M. grisea, NUT1. Evaluation of seven nitrogen starvation-induced genes revealed that all were expressed during rice infection. Targeted gene replacement on one such gene, the vacuolar serine protease, SPM1, resulted in decreased sporulation and appressorial development as well as a greatly attenuated ability to cause disease. Data are discussed in the context of nitrogen metabolism under starvation conditions, as well as conditions potentially encountered during invasive growth in planta.

Amino Acids↗
PubMed2005

Abnormal neuronal metabolism and storage in mucopolysaccharidosis type VI (Maroteaux-Lamy) disease.

Mucopolysaccharidosis (MPS) type VI, also known as Maroteaux-Lamy disease, is an inherited disorder of glycosaminoglycan catabolism caused by deficient activity of the lysosomal hydrolase, N-acetylgalactosamine 4-sulphatase (4S). A variety of prominent visceral and skeletal defects are characteristic, but primary neurological involvement has generally been considered absent. We report here that the feline model of MPS VI exhibits abnormal lysosomal storage in occasional neurones and glia distributed throughout the cerebral cortex. Abnormal lysosomal inclusions were pleiomorphic with some resembling zebra bodies and dense core inclusions typical of other MPS diseases or the membranous storage bodies characteristic of the gangliosidoses. Pyramidal neurones were shown to contain abnormal amounts of GM2 and GM3 gangliosides by immunocytochemical staining and unesterified cholesterol by histochemical (filipin) staining. Further, Golgi staining of pyramidal neurones revealed that some possessed ectopic axon hillock neurites and meganeurites similar to those described in Tay-Sachs and other neuronal storage diseases with ganglioside storage. Some animals evaluated in this study also received allogeneic bone marrow transplants, but no significant differences in neuronal storage were noted between treated and untreated individuals. These studies demonstrate that deficiency of 4S activity can lead to metabolic abnormalities in the neurones of central nervous system in cats, and that these changes may not be readily amenable to correction by bone marrow transplantation. Given the close pathological and biochemical similarities between feline and human MPS VI, it is conceivable that children with this disease have similar neuronal involvement.

Animals↗
PubMed2001

BCL-2 cooperates with promyelocytic leukemia retinoic acid receptor alpha chimeric protein (PMLRARalpha) to block neutrophil differentiation and initiate acute leukemia.

The promyelocytic leukemia retinoic acid receptor alpha (PMLRARalpha) chimeric protein is associated with acute promyelocytic leukemia (APL). PMLRARalpha transgenic mice develop leukemia only after several months, suggesting that PMLRARalpha does not by itself confer a fully malignant phenotype. Suppression of apoptosis can have a central role in tumorigenesis; therefore, we assessed whether BCL-2 influenced the ability of PMLRARalpha to initiate leukemia. Evaluation of preleukemic animals showed that whereas PMLRARalpha alone modestly altered neutrophil maturation, the combination of PMLRARalpha and BCL-2 caused a marked accumulation of immature myeloid cells in bone marrow. Leukemias developed more rapidly in mice coexpressing PMLRARalpha and BCL-2 than in mice expressing PMLRARalpha alone, and all mice expressing both transgenes succumbed to leukemia by 7 mo. Although both preleukemic, doubly transgenic mice and leukemic animals had abundant promyelocytes in the bone marrow, only leukemic mice exhibited thrombocytopenia and dissemination of immature cells. Recurrent gain of chromosomes 7, 8, 10, and 15 and recurrent loss of chromosome 2 were identified in the leukemias. These chromosomal changes may be responsible for the suppression of normal hematopoiesis and dissemination characteristic of the acute leukemias. Our results indicate that genetic changes that inhibit apoptosis can cooperate with PMLRARalpha to initiate APL.

Animals↗
PubMed2001

Enzyme replacement therapy in feline mucopolysaccharidosis I.

Enzyme replacement therapy (ERT) has long been considered an approach to treating lysosomal storage disorders caused by deficiency of lysosomal enzymes. ERT is currently used to treat Gaucher disease and is being developed for several lysosomal storage disorders now that recombinant sources of the enzymes have become available. We have continued development of ERT for mucopolysaccharidosis I (MPS I) using the feline model. Recombinant alpha-L-iduronidase was administered intravenously at low dose (approximately 0.1 mg/kg or 25,000 units/kg) to four cats and high dose (0.5 mg/kg or 125,000 units/kg) to two cats on a weekly basis for 3- or 6-month terms. Clinical examinations showed distinct clearing of corneal clouding in one cat although clinical effects in the others were not evident. Biochemical studies of the cats showed that the enzyme was distributed to a variety of tissues although the liver and spleen contained the highest enzyme activities. Glycosaminoglycan storage was decreased in liver and spleen, and the histologic appearance improved in liver, spleen, and renal cortex. Enzyme was not consistently detected in cerebral cortex, brainstem, or cerebellum and the histologic appearance and ganglioside profiles did not improve. A variety of other tissues showed low variable uptake of enzyme and no distinct improvement. IgG antibodies to alpha-L-iduronidase were observed in five cats with higher titers noted when higher doses were administered. Mild complement activation occurred in three cats. Enzyme replacement therapy was effective in reversing storage in some tissues at the biochemical and histologic level in MPS I cats but an improved tissue distribution and prevention of a significant immune response could make the therapy more effective.

Animals↗
PubMed2001

Effects of dietary cholesterol restriction in a feline model of Niemann-Pick type C disease.

A feline model of Niemann-Pick disease type C (NPC) was employed to evaluate the effect of dietary cholesterol restriction on progression of disease. Two NPC-affected treated cats were fed a cholesterol-restricted diet beginning at 8 weeks of age; the cats remained on the diet for 150 and 270 days respectively. The study goal was to lower the amount of low density lipoprotein (LDL) available to cells, hypothetically reducing subsequent lysosomal accumulation of unesterified cholesterol and other lipids. Neurological progression of disease was not altered and dietary cholesterol restriction did not significantly decrease storage in NPC-affected treated cats. One NPC-affected treated cat had decreased serum alkaline phosphatase activity (ALP) and decreased serum cholesterol concentration. Liver lipid concentrations of unesterified cholesterol, cholesterol ester and phospholipids in NPC-affected treated cats were similar to those seen in NPC-affected untreated cats. Ganglioside concentrations in the NPC-affected treated cats and NPC-affected untreated cats were similar. Histological findings in liver sections from NPC-affected treated cats showed a diffuse uniform microvacuolar pattern within hepatocytes and Kupffer cells, in contrast to a heterogeneous macro/microvacuolar pattern and prominent nodular fibrosis in NPC-affected untreated cats. Similar differences in vacuolar patterns were seen in splenic macrophages. Although some hepatic parameters were modified, dietary cholesterol restriction did not appear to alter disease progression in NPC-affected kittens.

Alanine Transaminase↗
PubMed2001

Flavonoids act as negative regulators of auxin transport in vivo in arabidopsis.

Polar transport of the plant hormone auxin controls many aspects of plant growth and development. A number of synthetic compounds have been shown to block the process of auxin transport by inhibition of the auxin efflux carrier complex. These synthetic auxin transport inhibitors may act by mimicking endogenous molecules. Flavonoids, a class of secondary plant metabolic compounds, have been suggested to be auxin transport inhibitors based on their in vitro activity. The hypothesis that flavonoids regulate auxin transport in vivo was tested in Arabidopsis by comparing wild-type (WT) and transparent testa (tt4) plants with a mutation in the gene encoding the first enzyme in flavonoid biosynthesis, chalcone synthase. In a comparison between tt4 and WT plants, phenotypic differences were observed, including three times as many secondary inflorescence stems, reduced plant height, decreased stem diameter, and increased secondary root development. Growth of WT Arabidopsis plants on naringenin, a biosynthetic precursor to those flavonoids with auxin transport inhibitor activity in vitro, leads to a reduction in root growth and gravitropism, similar to the effects of synthetic auxin transport inhibitors. Analyses of auxin transport in the inflorescence and hypocotyl of independent tt4 alleles indicate that auxin transport is elevated in plants with a tt4 mutation. In hypocotyls of tt4, this elevated transport is reversed when flavonoids are synthesized by growth of plants on the flavonoid precursor, naringenin. These results are consistent with a role for flavonoids as endogenous regulators of auxin transport.

Alleles↗
PubMed2001

Flavonoid accumulation patterns of transparent testa mutants of arabidopsis.

Flavonoids have been implicated in the regulation of auxin movements in Arabidopsis. To understand when and where flavonoids may be acting to control auxin movement, the flavonoid accumulation pattern was examined in young seedlings and mature tissues of wild-type Arabidopsis. Using a variety of biochemical and visualization techniques, flavonoid accumulation in mature plants was localized in cauline leaves, pollen, stigmata, and floral primordia, and in the stems of young, actively growing inflorescences. In young Landsberg erecta seedlings, aglycone flavonols accumulated developmentally in three regions, the cotyledonary node, the hypocotyl-root transition zone, and the root tip. Aglycone flavonols accumulated at the hypocotyl-root transition zone in a developmental and tissue-specific manner with kaempferol in the epidermis and quercetin in the cortex. Quercetin localized subcellularly in the nuclear region, plasma membrane, and endomembrane system, whereas kaempferol localized in the nuclear region and plasma membrane. The flavonoid accumulation pattern was also examined in transparent testa mutants blocked at different steps in the flavonoid biosynthesis pathway. The transparent testa mutants were shown to have precursor accumulation patterns similar to those of end product flavonoids in wild-type Landsberg erecta, suggesting that synthesis and end product accumulation occur in the same cells.

Arabidopsis↗
PubMed2000

Synthesis and spectroscopy of N3P3X5OCH=CH2 (X = Cl, F, OCH3, OCH2CF3, N(CH3)2) and N3P3X4(OCH=CH2)2 (X = Cl, N(CH3)2). Correlations of ultraviolet photoelectron spectroscopy and nuclear magnetic resonance data to electronic and geometrical structure.

The syntheses of the vinyloxycyclotriphosphazene derivatives N3P3X5OCH=CH2 (X = OMe, OCH2CF3) and the N3P3(NMe2)4(OCH=CH2)2 isomeric mixture along with improved preparations of N3P3X5OCH=CH2 (X = F, NMe2) are reported. The interactions between the vinyloxy function and the cyclophosphazene in these and the previously reported N3P3Cl5 (OCH=CH2) and N3P3F6-n(OCH=CH2)n (n = 1-4) have been examined by ultraviolet photoelectron spectroscopy (UPS) and NMR spectroscopy. The UPS data for the chloro and fluoro derivatives show a strong electron-withdrawing effect of the phosphazene on the olefin that is mediated with decreasing halogen substitution. The 1H and 13C NMR data for N3P3X5OCH=CH2 (X = F, Cl, OMe, OCH2CF3, NMe2) show significant changes as a function of the phosphazene substituent. There is a linear correlation between the beta-carbon chemical shift on the vinyloxy unit and the phosphorus chemical shift at the vinyloxyphosphorus centers. The chemical shifts of the different phosphorus centers on each ring are also related in a linear fashion. These relationships may be understood in terms of the relative electron donor-acceptor abilities of the substituents on the phosphazene ring. The 1H NMR spectra of the N3P3(NMe2)4(OCH-CH2)2 isomeric mixture allow for assignment of the relative amounts of cis and trans isomers. A model for the observed cis preference in the formation of N3P3Cl4(OCH=CH)2 is presented.

Journal Article↗
PubMed2000

A novel approach to the assessment of variations in the human platelet count.

This is the first report of a method to assess the significance of numerical changes in the platelet count based upon a result exceeding the normal intra-individual variation in platelet numbers. Serial platelet counts from 3,789 subjects were analysed to determine the intra-individual variation in platelet numbers. A platelet count difference of 98 x 10(9)/L in males was found to represent a change that would occur by chance in less than 1 in 1,000 platelet count determinations. Tables to determine the significance of platelet number variations, given N previous observations, are provided at two probability levels. The repeatability of the platelet count was calculated as 0.871 (males) and 0.849 (females) indicating that the heritability of platelet count is high and that the platelet count is predominantly genetically determined. A seasonal variation in platelet count was found with a 'winter' versus 'summer' difference of 5.10 X 10(9)/L (males) and 5.82 x 10(9)/L (females).

Analysis of Variance↗
PubMed1999

Functional and structural diversity of the human Dickkopf gene family.

Wnt proteins influence many aspects of embryonic development, and their activity is regulated by several secreted antagonists, including the Xenopus Dickkopf-1 (xDkk-1) protein. xDkk-1 inhibits Wnt activities in Xenopus embryos and may play a role in induction of head structures. Here, we characterize a family of human Dkk-related genes composed of Dkk-1, Dkk-2, Dkk-3, and Dkk-4, together with a unique Dkk-3 related protein termed Soggy (Sgy). hDkks 1-4 contain two distinct cysteine-rich domains in which the positions of 10 cysteine residues are highly conserved between family members. Sgy is a novel secreted protein related to Dkk-3 but which lacks the cysteine-rich domains. Members of the Dkk-related family display unique patterns of mRNA expression in human and mouse tissues, and are secreted when expressed in 293T cells. Furthermore, secreted hDkk-2 and hDkk-4 undergo proteolytic processing which results in cleavage of the second cysteine-rich domain from the full-length protein. Members of the human Dkk-related family differ not only in their structures and expression patterns, but also in their abilities to inhibit Wnt signaling. hDkk-1 and hDkk-4, but not hDkk-2, hDkk-3 or Sgy, suppress Wnt-induced secondary axis induction in Xenopus embryos. hDkk-1 and hDkk-4 do not block axis induction triggered either by Xenopus Dishevelled (Xdsh) or Xenopus Frizzled-8 (Xfz8), both of which function to transduce signals from Wnt ligands. Thus, hDkks 1 and 4 may inhibit Wnt activity by a mechanism upstream of Frizzled. Our findings highlight the structural and functional heterogeneity of human Dkk-related proteins.

Amino Acid Sequence↗
PubMed1999

Natural experimental models: the global search for biomedical paradigms among traditional, modernizing, and modern populations.

During the past four decades, biomedical scientists have slowly begun to recognize the unique opportunities for studying biomedical processes, disease etiology, and mechanisms of pathogenesis in populations with unusual genetic structures, physiological characteristics, focal endemic disease, or special circumstances. Such populations greatly extend our research capabilities and provide a natural laboratory for studying relationships among biobehavioral, genetic, and ecological processes that are involved in the development of disease. The models presented illustrate three different types of natural experiments: those occurring in traditionally living, modernizing, and modern populations. The examples are drawn from current research that involves population mechanisms of adaptation among East African Turkana pastoralists; a search for etiology and mechanisms of pathogenesis of an emerging disease among the Yakut people of Siberia; and psychosocial stress, hypertension, and cardiovascular disease in women working outside the home in New York City and among subpopulations in Hawaii. The models in general, and the examples in specific, represent natural laboratories in which relatively small intrapopulation differences and large interpopulation differences can be used to evaluate health and disease outcomes.

Africa, Eastern↗
PubMed1998

Comparison of factors affecting daily variation of blood pressure in Filipino-American and Caucasian nurses in Hawaii.

Although several studies have examined differences in daily blood pressure variability between African-American and Caucasian groups in the United States, little is known about the blood pressure variation of other ethnic groups. This study examined the effects of emotional state, setting, posture, and ethnicity on the ambulatory blood pressure of female health care workers (nurses and nurse's aides) from 2 ethnic groups: Filipino-Americans (N = 38) and Caucasians (N = 22). Ambulatory blood pressure measurements were obtained at 15-min intervals during a typical work day. Participants reported in a diary their setting (work or home), posture, mood, and specific activity at each measurement. The effects of these factors and ethnicity were examined using analysis of variance (ANOVA). The results show that for all subjects blood pressure was higher at work (P < 0.05), while standing (P < 0.05), during reports of negative moods (anxiety, anger, or sadness) (P < 0.05), and while engaging in activities such as interacting with fellow staff members at work and "washing up" at home. However, the Filipino-American women reported negative moods more frequently than their Caucasian counterparts (P < 0.05), had a greater proportion of readings taken while standing at work, and reacted differently than the Caucasian women to some specific activities; for instance, their blood pressure was not elevated when doing household chores. These results suggest that the extent of blood pressure variation in daily life may depend upon cognitive processes which are influenced by the cultural background and emotional state of the individual. They further suggest that ethnicity has an important impact on blood pressure variation.

Adult↗
PubMed1997

GABAergic neuroaxonal dystrophy and other cytopathological alterations in feline Niemann-Pick disease type C.

Feline Niemann-Pick disease type C (NPC) is an autosomal recessive lysosomal storage disease which shares many of the clinical, biochemical and pathological features of the corresponding human disorder. Cytopathological alterations in distinct neuronal cell populations were investigated in this animal model to gain a better understanding of the pathogenesis of brain dysfunction. Golgi and immunocytochemical methods were employed to characterize the cell architectural changes occurring in neuronal somata, dendrites and axons at different stages of disease progression. Cortical pyramidal neurons in laminae II, III, and V exhibited various degrees of meganeurite and/or swollen axon hillock formation with or without ectopic dendritogenesis. Enlarged axon hillock regions with neuritic processes and spines were recognized early in the progression of feline NPC but were less prevalent in mid to late stages of the disease. Glutamic acid decarboxylase (GAD) immunocytochemistry demonstrated immunoreactive spheroids in numerous GABAergic axons in neocortex, subcortical areas, and cerebellum. Parvalbumin-immunoreactive axonal spheroid distribution in brain closely mirrored results from the GAD studies, whereas calbindin D-28k-immunoreactive spheroids were conspicuously absent in most cortical and subcortical areas examined. Purkinje cell axonal spheroid formation progressed in a distal to proximal direction, with eventual involvement of recurrent axon collaterals. Purkinje cell death and a concomitant decrease in the numbers of spheroids in the cerebellum were observed late in the disease course. Clinical neurological signs in feline NPC occur in parallel with neuronal structural alterations and suggest that GABAergic neuroaxonal dystrophy is a contributor to brain dysfunction in this disease.

Age Factors↗
PubMed1997

Mechanisms of echinocytosis induced by Crotalus atrox venom.

Transient echinocytosis has been reported in association with snake envenomation in humans and dogs. An in vitro model of echinocytosis induced by venom of crotalus atrox (western diamondback rattlesnake) was established to characterize erythrocyte morphologic changes and to investigate potential mechanisms of echinocytic transformation. Erythrocyte morphologic changes produced after the addition of venom to canine, feline, equine, and human blood were characterized by dose-dependent echinocytosis. Type III echinocytosis were consistently induced in vitro at a dose comparable to in vivo envenomation; higher venom doses produced spheroechinocytic and spherocytic transformations. The changes could not be induced in vitro in the presence of ethylenediaminetraacetic acid but were observed in heparinized and citrated blood samples, suggesting the participation of calcium or a metalloprotein in echinocytic change. These findings suggest that phospholipase A2 (PLA2), a calcium-dependent enzyme in snake venom, may be responsible for echinocytic transformation via the production of lysolecithin, a known echinocytic agent. Purified PLA2 from C. atrox venom induced dose-dependent echinocytic change in vitro in canine blood. Other potential mechanisms of echinocytic change evaluated in canine blood included erythrocyte cation loss and erythrocyte ATP depletion. In canine blood mixed with venom, erythrocyte sodium and potassium concentrations were consistently less than those of controls, likely as a result of membrane alteration produced by the actions of PLA2. There was no difference in blood ATP concentrations from dogs with snakebite when compared with normal controls; however, the power of this comparison was low. Echinocytosis induced by rattlesnake venom is related to the degree of venom exposure and may correlate clinically with the amount of venom absorbed. Echinocytic transformation in vitro is induced by PLA2 present in venom.

Adenosine Triphosphate↗
PubMed1996

Identification of the quinone cofactor in a lysyl oxidase from Pichia pastoris.

A copper amine oxidase from Pichia pastoris is the only known non-mammalian lysyl oxidase [Tur, S.S. and Lerch, K. (1988) FEBS Lett. 238, 74-76]. Recently, the cofactor in mammalian lysyl oxidase has been identified as a novel lysine tyrosylquinone moiety [Wang, S.X., Mure, M., Medzihradszky, K.F., Burlingame, A.L., Brown, D.E., Dooley, D.M., Smith, A.J., Kagan, H.M. and Klinman, J.P. (1996) Science 273, 1078-1084]. In order to identify the cofactor in P. pastoris lysyl oxidase, we have isolated the phenylhydrazone-derivative of the active-site peptide. This peptide has the active-site sequence conserved among topa quinone containing amine oxidases. The resonance Raman spectra of the phenylhydrazone derivatives of the enzyme, active-site peptide, and a topa quinone model compound are essentially identical. Collectively, these results establish that P. pastoris lysyl oxidase is a topa quinone enzyme.

Amino Acid Sequence↗
PubMed1996

A crosslinked cofactor in lysyl oxidase: redox function for amino acid side chains.

A previously unknown redox cofactor has been identified in the active site of lysyl oxidase from the bovine aorta. Edman sequencing, mass spectrometry, ultraviolet-visible spectra, and resonance Raman studies showed that this cofactor is a quinone. Its structure is derived from the crosslinking of the epsilon-amino group of a peptidyl lysine with the modified side chain of a tyrosyl residue, and it has been designated lysine tyrosylquinone. This quinone appears to be the only example of a mammalian cofactor formed from the crosslinking of two amino acid side chains. This discovery expands the range of known quino-cofactor structures and has implications for the mechanism of their biogenesis.

Amino Acid Sequence↗
PubMed1996

Menarche age, fatness, and fat distribution in Hawaiian adolescents.

Menarche age was assessed in 93 adolescent females in a sample of public schools in East Hawaii. Native Hawaiian girls had significantly lower reported age at menarche than non-Hawaiian classmates. Age at menarche was significantly correlated with total fatness as measured by the sum of six skinfolds in girls who had reached menarche at least 2 years previous to measurement. When fatness was controlled in comparisons, the ethnic differences were not significant. Fat distribution, independent of fatness, was also significantly related to age at menarche. Socioeconomic, cultural, and admixture variables were not significantly related to age at menarche. Adiposity appears to be both a cause and a consequence of early age at menarche, with the relationship dependent on the elapsed time between menarche and measurement. This suggests that studies relating body composition to age at menarche must carefully control for the time interval between measurement and the date of menarche.

Adolescent↗