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Biomedical subjects

J Fang

Publications and source records attributed to J Fang.

At least 19 recordsLinked to original sources
PubMed2002

Developmental exposure to polychlorinated biphenyls affects sexual behavior of rats.

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that have the potential to disrupt reproduction through a variety of different pathways. In the present study, we investigated the effects of fetal and lactational PCB exposure on reproductive behavior in male and female laboratory rats. These pregnant rats were injected daily with either 2,4,2',4'-tetrachlorobiphenyl (PCB 47) at the dosage of 1 or 20 mg/kg body weight or 3,4,3',4'-tetrachlorobiphenyl (PCB 77) at the dosage of 0.25 or 1 mg/kg body weight or sesame oil (control group) from gestational days 7 to 18. Offspring were then tested for sexual behavior as adults. Exposure to both PCB 77 and PCB 47 reduced the level of sexual receptivity in the female offspring, but had no detectable effects on the sexual behavior of the male offspring. In addition to changes in adult sexual behavior in the females, both PCBs produced a significant increase in the females' anogenital distance, suggesting a modification of androgen responsiveness in females resulting from PCB exposure during development. Similar effects were not seen with the males.

Analysis of Variance↗
PubMed2002

Copper speciation and accumulation in the gill microenvironment of carp ( Cyprinus carpio) in the presence of kaolin particles.

Carp were exposed to copper adsorbed on kaolin particles at various concentrations (0-2.4 mg/L), and net accumulation due to elevated adsorbed copper in the surrounding water was observed. Copper speciation in the water and fish gill microenvironment was modeled in the presence and absence of kaolin using a chemical speciation program (MINTEQA2). The adsorption affinity constants of kaolin for copper at various pH values used in the speciation calculations were experimentally determined, and the quantitative relationship between the affinity constant and pH was modeled. Copper accumulations in fish gills exposed to kaolin-adsorbed copper was then observed. The results indicate that desorption occurred in the fish gill microenvironment due to both mucus competition of copper and slight increase in water pH. Furthermore, the available copper species increased as a result of desorption, causing a net accumulation of Cu by the gills.

Adsorption↗
PubMed2002

Isolation, characterization, and functional expression of kynurenine aminotransferase cDNA from the yellow fever mosquito, Aedes aegypti(1).

This study describes the molecular and biochemical characterization of kynurenine aminotransferase (KAT) from Aedes aegypti mosquitoes. Through screening an A. aegypti larval cDNA library, a 1695-bp full-length cDNA clone with a 1434-bp open reading frame (ORF) was isolated. Its deduced amino acid sequence consists of 477 amino acid residues with a predicted molecular mass of 53,490 and the amino acid sequence shares 47 and 42% identity with KATs from Homo sapiens and Rattus norvegicus, respectively. This putative A. aegypti KAT (AeKAT) has four potential N-glycosylation sites (Asn-Xxx-Trp/Ser) and a typical mitochondrial leader sequence consisting of 49 amino acids at its NH(2)-terminus with a putative cleavage site between Met-49 and Ser-50. A consensus pyridoxal 5'-phosphate (PLP) binding domain (Gly-Ser-Ala-Gly-Lys-Thr-Phe-Ser) is present in the central region of the ORF. Using a baculovirus/insect cell expression system, a full-length AeKAT and a truncated AeKAT, lacking the mitochondrial leader sequence, were expressed. The full-length AeKAT expressed in Sf9 insect cells is insoluble and has no detectable KAT activity, but the truncated AeKAT is soluble and capable of catalyzing the transamination of kynurenine to kynurenic acid in the presence of pyruvate as an amino group acceptor. However, the expressed truncated protein is not active to 3-hydroxykynurenine. Northern analysis indicates that transcription of the AeKAT occurs at all stages during mosquito development, but higher levels of mRNA are observed during the pupal and adult stages. Results indicate that a specific KAT is present in mosquitoes and the enzyme may play an important physiological role in A. aegypti.

Aedes↗
PubMed2002

A new case of CDG-x with stereotyped dystonic hand movements and optic atrophy.

We report the clinical findings and the diagnostic work-up of a 17-month-old girl with CDG-x. Predominant clinical signs were, besides psychomotor retardation and truncal hypotonia, stereotyped dystonic hand movements and ophthalmological abnormalities such as optic atrophy, nystagmus and strabismus. Other symptoms that are often found in patients with CDG were not present, such as seizures, microcephaly, cerebellar hypoplasia, dysmorphic features, hepatointestinal disease, coagulopathy or multiorgan involvement. Isoelectric focusing (IEF) of the patient's serum showed a marked elevation of disialotransferrin, thus confirming an IEF type 1 pattern. A generalized glycosylation defect was confirmed also by IEF of a further glycoprotein (alpha1-antitrypsin), an increased carbohydrate deficient transferrin (CDT) serum concentration and an increased CDT/transferrin ratio. All known types of CDG-I, secondary glycosylation abnormalities and variants of amino acid sequence were excluded.

Dystonia↗
PubMed2002

Congenital disorder of glycosylation IId (CDG-IId) -- a new entity: clinical presentation with Dandy-Walker malformation and myopathy.

A 1.5-year-old boy with macrocephaly due to a Dandy-Walker malformation presented with progressive hydrocephalus, extensive muscular hypotonia, transient cholestatic syndrome, extensive coagulation abnormalities and elevated creatine kinase indicating myopathy. Diagnostic work-up indicated a congenital disorder of glycosylation (CDG, formerly carbohydrate deficient glycoprotein syndrome). The serum transferrin pattern obtained by automated isoelectric focusing (IEF) showed an hitherto unreported pattern with strongly elevated tri-, di-, mono- and asialotransferrin bands, increasing in this order together with markedly decreased tetrasialotransferrin. Investigation of two additional glycoproteins, alpha(1)-antitrypsin and alpha(1)-antichymotrypsin, confirmed a generalised defect of glycosylation. All known glycosylation defects could be ruled out by enzymatic analyses in either leukocytes or fibroblasts or by the results obtained by IEF. SDS-electrophoresis demonstrated a marked difference in the molecular weight of transferrin, suggesting the lack of parts or of all oligosaccharide chains. The defect could be delineated to a deficiency of beta-1,4-galactosyltransferase (E.C.2.4.1.38) due to a homozygous insertion (1031 - 1032 insC). Details of the biochemical and molecular findings will be described elsewhere.

Adolescent↗
PubMed2002

Sleep of transgenic mice producing excess rat growth hormone.

The effects of chronic excess of growth hormone (GH) on sleep-wake activity was determined in giant transgenic mice in which the metallothionein-1 promoter stimulates the expression of rat GH (MT-rGH mice) and in their normal littermates. In the MT-rGH mice, the time spent in spontaneous non-rapid eye movement sleep (NREMS) was enhanced moderately, and rapid eye movement sleep (REMS) time increased greatly during the light period. After a 12-h sleep deprivation, the MT-rGH mice continued to sleep more than the normal mice, but there were no differences in the increments in NREMS, REMS, and electroencephalogram (EEG) slow-wave activity (SWA) during NREMS between the two groups. Injection of the somatostatin analog octreotide elicited a prompt sleep suppression followed by increases in SWA during NREMS in normal mice. These changes were attenuated in the MT-rGH mice. The decreased responsiveness to octreotide is explained by a chronic suppression of hypothalamic GH-releasing hormone in the MT-rGH mice. Enhancements in spontaneous REMS are attributed to the REMS-promoting activity of GH. The increases in spontaneous NREMS are, however, not consistent with our current understanding of the role of somatotropic hormones in sleep regulation. Metabolic, neurotransmitter, or hormonal changes associated with chronic GH excess may indirectly influence sleep.

Animals↗
PubMed2001

Kynurenine aminotransferase and glutamine transaminase K of Escherichia coli: identity with aspartate aminotransferase.

The present study describes the isolation of a protein from Escherichia coli possessing kynurenine aminotransferase (KAT) activity and its identification as aspartate aminotransferase (AspAT). KAT catalyses the transamination of kynurenine and 3-hydroxykynurenine to kynurenic acid and xanthurenic acid respectively, and the enzyme activity can be easily detected in E. coli cells. Separation of the E. coli protein possessing KAT activity through various chromatographic steps led to the isolation of the enzyme. N-terminal sequencing of the purified protein determined its first 10 N-terminal amino acid residues, which were identical with those of the E. coli AspAT. Recombinant AspAT (R-AspAT), homologously expressed in an E. coli/pET22b expression system, was capable of catalysing the transamination of both l-kynurenine (K(m)=3 mM; V(max)=7.9 micromol.min(-1).mg(-1)) and 3-hydroxy-dl-kynurenine (K(m)=3.7 mM; V(max)=1.25 micromol.min(-1).mg(-1)) in the presence of pyruvate as an amino acceptor, and exhibited its maximum activity at temperatures between 50-60 degrees C and at a pH of approx. 7.0. Like mammalian KATs, R-AspAT also displayed high glutamine transaminase K activity when l-phenylalanine was used as an amino donor (K(m)=8 mM; V(max)=20.6 micromol.min(-1).mg(-1)). The exact match of the first ten N-terminal amino acid residues of the KAT-active protein with that of AspAT, in conjunction with the high KAT activity of R-AspAT, provides convincing evidence that the identity of the E. coli protein is AspAT.

Aspartate Aminotransferases↗
PubMed2001

Chemical modifications of the (1-->3)-alpha-D-glucan from spores of Ganoderma lucidum and investigation of their physicochemical properties and immunological activity.

A linear (1-->3)-alpha-D-glucan was isolated from the spores of Ganoderma lucidum (Fr.) Karst. Six different functionalized derivatives of the (1-->3)-alpha-D-glucan-aminopropylated, hydroxyethylated, sulfated, carboxymethylated, carboxymethylated and sulfated, and benzylamidated-carboxymethylated-with varying degrees of substitution were synthesized. The structural features and physicochemical properties of all derivatives were investigated by means of chemical and spectral analyses, and their effects on lymphocyte proliferation and antibody production were tested in vitro and in vivo. In general, the structural and physicochemical properties, and lymphocyte proliferation activity of all samples varied with the functionalized groups and the degree of substitution. The results of immunological assays indicated that some modified derivatives had potent stimulating effects on lymphocyte proliferation and antibody production and the introduction of carboxymethyl group with low degree of substitution (DS<0.28) was the best choice on the improvement of the immunostimulating activity.

Adjuvants, Immunologic↗
PubMed2001

HIF-1alpha-mediated up-regulation of vascular endothelial growth factor, independent of basic fibroblast growth factor, is important in the switch to the angiogenic phenotype during early tumorigenesis.

The switch to the angiogenic phenotype represents a critical checkpoint during tumor progression. The acquisition of new capillary vessels provides newly vascularized tumor nodules with a distinct biological advantage over their avascular counterparts by conferring upon them the ability to expand and develop both locally and metastatically. To identify the molecules and mechanisms underlying this rate-limiting step in successful tumorigenesis, we have developed an in vivo tumor model that reproducibly recapitulates the angiogenic switch. Using this model, we have analyzed vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hypoxia-inducible factor-1alpha (HIF-1alpha) expression and activity in both avascular and vascular growth phases of the tumor. A significantly higher level of VEGF protein was detected in avascular tumor nodules compared with vascular nodules. As avascular tumors became vascularized, VEGF levels decreased approximately 10-fold. In contrast, bFGF levels were not elevated in avascular nodules but rather were detected at levels approximately 2 times higher in vascular nodules compared with the avascular tumor nodules. Given that VEGF is transcriptionally regulated by HIF-1alpha, immunohistochemical studies of chondrosarcoma nodules were conducted and revealed that the nuclear translocation of HIF-1alpha was detected exclusively in avascular tumor nodules. This study implicates HIF-1alpha-mediated up-regulation of VEGF but not bFGF in the switch to the angiogenic phenotype during tumorigenesis.

Animals↗
PubMed2001

Changes in forest biomass carbon storage in China between 1949 and 1998.

The location and mechanisms responsible for the carbon sink in northern mid-latitude lands are uncertain. Here, we used an improved estimation method of forest biomass and a 50-year national forest resource inventory in China to estimate changes in the storage of living biomass between 1949 and 1998. Our results suggest that Chinese forests released about 0.68 petagram of carbon between 1949 and 1980, for an annual emission rate of 0.022 petagram of carbon. Carbon storage increased significantly after the late 1970s from 4.38 to 4.75 petagram of carbon by 1998, for a mean accumulation rate of 0.021 petagram of carbon per year, mainly due to forest expansion and regrowth. Since the mid-1970s, planted forests (afforestation and reforestation) have sequestered 0.45 petagram of carbon, and their average carbon density increased from 15.3 to 31.1 megagrams per hectare, while natural forests have lost an additional 0.14 petagram of carbon, suggesting that carbon sequestration through forest management practices addressed in the Kyoto Protocol could help offset industrial carbon dioxide emissions.

Biomass↗
PubMed2001

Structural and immunological studies of a major polysaccharide from spores of Ganoderma lucidum (Fr.) Karst.

A polysaccharide isolated from spores of the fungus, Ganoderma lucidum, was found to be a complex glucan. On the basis of compositional and methylation analyses, periodate oxidation, Smith degradation, 1D and 2D NMR, and ESIMS experiments of the native polysaccharide and its degraded products, the polysaccharide was shown to have a backbone of beta-(1-->3)-linked D-glucopyranosyl residues, with branches of mono-, di- and oligosaccharide side chains substituting at the C-6 of the glucosyl residues in the main chain. Conformational analysis in aqueous solution and immunological activities of the native and degraded glucans were also investigated. The results suggested that the degree of substitution on the main chain and the length of side chains may be very important factors in determining the conformation and the biological activities of beta-(1-->3)-linked glucans.

Animals↗
PubMed2001

Sleep modifies glutamate decarboxylase mRNA within the barrel cortex of rats after a mystacial whisker trim.

STUDY OBJECTIVES: Determine the effects of time of day and sleep deprivation on glutamate decarboxylase 67,000 MW (GAD67) mRNA during cortical synaptic reorganization induced by a unilateral trimming of the mystacial vibrissae in rats. DESIGN: Two experiments were conducted--One measured GAD67 mRNA in the barrel cortex at 3 or 6 h after a unilateral whisker cut at either light or dark onset; the other measured GAD67 mRNA after a unilateral whisker cut at light onset with or without sleep deprivation. SETTING: University-based Research Laboratory. PARTICIPANTS: Sprague-Dawley rats (250-350 g). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The reverse transcriptase polymerase chain reaction was used to measure the time of day changes in GAD67 mRNA after a unilateral whisker cut. GAD67 mRNA decreased in the barrel cortex at 3 and 6 h after a whisker trim at dark onset when the rats were mainly awake. No changes were observed in GAD67 mRNA levels after a whisker cut at light onset, a time when the rats mainly sleep. In situ hybridization for GAD67 mRNA supported these findings; no changes in GAD mRNA occurred in layer 4 of the barrel cortex that received input from the mystacial whiskers that were trimmed at light onset. However, when the rats were sleep-deprived, GAD67 mRNA increased in the barrel cortex receiving input from the lip hairs surrounding the trimmed mystacial whiskers. CONCLUSIONS: These data imply that sleep modifies GAD67 mRNA expression and that this effect is dependent upon the nature of the ongoing synaptic reorganization. They support the notion that sleep serves a synaptic function.

Animals↗
PubMed2001

Deficiency of growth hormone-releasing hormone signaling is associated with sleep alterations in the dwarf rat.

The somatotropic axis, and particularly growth hormone-releasing hormone (GHRH), is implicated in the regulation of sleep-wake activity. To evaluate sleep in chronic somatotropic deficiency, sleep-wake activity was studied in dwarf (dw/dw) rats that are known to have a defective GHRH signaling mechanism in the pituitary and in normal Lewis rats, the parental strain of the dw/dw rats. In addition, expression of GHRH receptor (GHRH-R) mRNA in the hypothalamus/preoptic region and in the pituitary was also determined by means of reverse transcription-PCR, and GHRH content of the hypothalamus was measured. Hypothalamic/preoptic and pituitary GHRH-R mRNA levels were decreased in the dw/dw rats, indicating deficits in the central GHRHergic transmission. Hypothalamic GHRH content in dw/dw rats was also less than that found in Lewis rats. The dw/dw rats had less spontaneous nonrapid eye movement sleep (NREMS) (light and dark period) and rapid eye movement sleep (REMS) (light period) than did the control Lewis rats. After 4 hr of sleep deprivation, rebound increases in NREMS and REMS were normal in the dw/dw rat. As determined by fast Fourier analysis of the electroencephalogram (EEG), the sleep deprivation-induced enhancements in EEG slow-wave activity in the dw/dw rats were only one-half of the response in the Lewis rats. The results are compared with sleep findings previously obtained in GHRH-deficient transgenic mice. The alterations in NREMS are attributed to the defect in GHRH signaling, whereas the decreases in REMS might result from the growth hormone deficiency in the dw/dw rat.

Animals↗
PubMed2001

Sleep deprivation but not a whisker trim increases nerve growth factor within barrel cortical neurons.

Sleep is hypothesized to influence activity-driven changes in the brain microcircuitry. A change in the barrel cortex following the removal of the mystacial whiskers in rats is a model for synaptic plasticity. This model was combined with sleep deprivation and immunoreactivity for nerve growth factor (NGF) was determined. Sleep deprivation for 6 h after light onset significantly increased the number of NGF-immunoreactive pyramidal neurons in layer V of the barrel cortex. However, unilateral trimming of mystacial whiskers did not affect NGF immunoreactivity in the contralateral or ipsilateral barrel cortices when rats were allowed to sleep. If the rats received a unilateral whisker cut at light onset, and subsequently were deprived of sleep, increases in the NGF-immunoreactive neurons were only observed in the barrel cortex on the side that received input from the remaining intact whiskers. In contrast, NGF immunoreactivity on the side contralateral to the cut whiskers decreased in sleep-deprived animals to levels below those observed in the control animals that were allowed to sleep. These results suggest that NGF expression is influenced by the interaction of sleep, afferent input and the nature of ongoing synaptic reorganization. Further, results are consistent with the hypothesis that growth factors, such as NGF, form part of the mechanism responsible for sleep regulation and that they also form one facet of sleep-related synaptic plasticity.

Animals↗
PubMed2001

Structures of bovine glutamate dehydrogenase complexes elucidate the mechanism of purine regulation.

Glutamate dehydrogenase is found in all organisms and catalyses the oxidative deamination of l-glutamate to 2-oxoglutarate. However, only animal GDH utilizes both NAD(H) or NADP(H) with comparable efficacy and exhibits a complex pattern of allosteric inhibition by a wide variety of small molecules. The major allosteric inhibitors are GTP and NADH and the two main allosteric activators are ADP and NAD(+). The structures presented here have refined and modified the previous structural model of allosteric regulation inferred from the original boGDH.NADH.GLU.GTP complex. The boGDH.NAD(+).alpha-KG complex structure clearly demonstrates that the second coenzyme-binding site lies directly under the "pivot helix" of the NAD(+) binding domain. In this complex, phosphates are observed to occupy the inhibitory GTP site and may be responsible for the previously observed structural stabilization by polyanions. The boGDH.NADPH.GLU.GTP complex shows the location of the additional phosphate on the active site coenzyme molecule and the GTP molecule bound to the GTP inhibitory site. As expected, since NADPH does not bind well to the second coenzyme site, no evidence of a bound molecule is observed at the second coenzyme site under the pivot helix. Therefore, these results suggest that the inhibitory GTP site is as previously identified. However, ADP, NAD(+), and NADH all bind under the pivot helix, but a second GTP molecule does not. Kinetic analysis of a hyperinsulinism/hyperammonemia mutant strongly suggests that ATP can inhibit the reaction by binding to the GTP site. Finally, the fact that NADH, NAD(+), and ADP all bind to the same site requires a re-analysis of the previous models for NADH inhibition.

Adenosine Diphosphate↗