Search PubMed⌕ Search

Biomedical subjects

J Qiu

Publications and source records attributed to J Qiu.

At least 163 records · Page 9Linked to original sources
PubMed1996

Gonocytes in testes of neonatal rats express the c-kit gene.

Information gathered from mutant mouse models and from studies on normal puberal and adult animals points to the product of the c-kit gene, a tyrosine kinase surface receptor, and the kit-ligand (KL) as important for gametogenesis in males. In fetuses, KL serves as a survival factor for primordial germ cells, at least in vitro, and in adults activity of the c-kit gene has been indirectly related to survival and subsequent development of differentiating spermatogonia. However, because of the structural complexity of the seminiferous epithelium in adults, c-kit mRNA has not yet been definitively localized to one or more types of spermatogenic cells. In addition, no information is currently available regarding the possible involvement of the c-kit protein and its ligand in mediating germ cell development and/or Sertoli-germ cell interactions immediately after birth when events critical for later onset of spermatogenesis are ongoing. Thus, the aims of the current study were (1) to determine whether the c-kit gene is expressed in testes of neonatal and adult rats and, if so, by what specific cell types, and (2) to determine if those cells expressing the gene also produce the c-kit receptor protein. For this, we isolated total RNA from testes of pups aged days 1-5 and from adult rat testes, and probed for the presence of c-kit mRNA with Northern analysis. We identified the cells containing the c-kit message by carrying out in situ hybridization with digoxigenin-labeled probes, thus allowing the colorimetric signal to be assigned beyond doubt to individual cells in sections of testes. We also utilized Western analysis and immunolocalization to confirm the presence of the c-kit receptor protein in testes at these ages and to identify those cells types producing it. Our findings indicate that (1) neonatal gonocytes express the c-kit gene and produce the receptor protein on postnatal days 1 through 5, spanning the time when they resume dividing and migrating, and (2) spermatogonia and, to a lesser extent, spermatocytes and spermatids of adults express the gene but c-kit protein is present in detectable amounts only in spermatogonia and possibly a few early primary spermatocytes.

Aging↗
PubMed1996

Direct determination of iron in ferritin using the polarographic catalytic current.

A new method for the determination of iron in ferritin using the polarographic catalytic current has been developed. Iron is released in NaOH and triethanolamine (TEA) solution and subsequently determined based on the polarographic catalytic wave in the presence of bromate with the peak potential of -1.0 V (vs.SCE). The 2.5-derivative peak height of iron is linearly proportional to its concentration in the range of 8.0 x 10(-8)-1.0 x 10(-6) g/ml with a correlation coefficient of 0.9991. The method has been applied to the determination of iron in human fetal liver and horse-spleen ferritin and the recovery is 95-112%.

Journal Article↗
PubMed1996

Investigation of a naphthalene pitch by high-resolution solid-state dynamic nuclear polarization.

The possibility of applying the dynamic nuclear polarization (DNP) technique to a study of char is explored with a naphthalene-derived pitch. It is shown that a 13C DNP enhancement factor of about 10(2) is obtained when the polarization is directly transferred from the unpaired electrons to the 13C nuclei. An undistorted spectrum with an enhancement factor of 8 is obtained by the DNP cross-polarization magic-angle spinning nuclear magnetic resonance (DNP-CP-MAS NMR) method. With such a high increase in S/N, it is possible to measure the 13C polarization time (Tp) and the spin-lattice relaxation time (T1) of the system in a reasonable experimental time. The resultant values are Tp = 19 s and T1 = 38 s, respectively. Based on the DNP enhancement as a function of the microwave frequency, it is found that the predominant DNP mechanism in the pitch is the solid-state effect.

Carbon Isotopes↗
PubMed1996

Lack of interference between IgA-binding proteins and IgA proteases of human pathogenic bacteria.

Some human bacterial pathogens produce specific immunoglobulin A1 (IgA1) proteases that cleave the heavy chain of human IgA1, generating intact Fab and Fc fragments. Other pathogenic bacterial species express surface proteins which bind to the Fc part of human IgA in a non-immune manner. To analyse whether IgA-binding proteins affect the activity of IgA1 proteases, the ability of seven different IgA1 proteases to hydrolyse IgA1 in the presence of either of two different bacterial IgA-binding proteins was tested. Data obtained in two different types of experiment suggest that IgA1 bound to IgA-binding proteins still functions as a substrate for IgA1 proteases. As Fc fragments produced by cleaving IgA1 with IgA1 proteases still bind to IgA-binding proteins, we conclude that these two types of bacterial protein act independently of each other.

Autoradiography↗
PubMed1996

Analysis of the specificity of bacterial immunoglobulin A (IgA) proteases by a comparative study of ape serum IgAs as substrates.

Immunoglobulin A (IgA) proteases are bacterial enzymes with substrate specificity for human serum and secretory IgAs. To further define the basis of this specificity, we examined the ability of IgA proteases of Clostridium ramosum, Streptococcus pneumoniae (EC 3.4.24.13), Neisseria meningitidis (EC 3.4.21.72), and Haemophilus influenzae (EC 3.4.21.72) to cleave serum IgAs of gorillas, chimpanzees, and orangutans. All enzymes cleaved the IgAs of the three apes despite differences in ape IgA1 hinge sequence relative to the human prototype. To directly compare the ape and human hinge cleavage sites, the sites were identified in eight ape IgA digests. This analysis confirmed that ape proteins were all cleaved in the IgA hinge region, in all but one case after proline residues. The exception, C. ramosum protease, cleaved gorilla and chimpanzee IgAs at peptide bonds having no proline, but the scissile bonds were in the same hinge location as the Pro-221-Val-222 cleaved in human IgA1. These data indicate that proline is not an invariant substrate requirement for all IgA proteases and that the location of the scissile bond, in addition to its composition, is a critical determinant of cleavage specificity.

Amino Acid Sequence↗
PubMed1996

per mRNA cycling is locked to lights-off under photoperiodic conditions that support circadian feedback loop function.

Circadian fluctuations in per mRNA and protein are central to the operation of a negative feedback loop that is necessary for setting the free-running period and for entraining the circadian oscillator to light-dark cycles. In this study, per mRNA cycling and locomotor activity rhythms were measured under different light and dark cycling regimes to determine how photoperiods affect the molecular feedback loop and circadian behavior, respectively. These experiments reveal that per mRNA peaks in abundance 4 h after lights-off in photoperiods of < or = 16 h, that, phase shifts in per mRNA cycling and behavioral rhythmicity occur rapidly after flies are transferred from one photoperiod to another, and that photoperiods longer than 20 h abolish locomotor activity rhythms and leave per mRNA at a median constitutive level. These results indicate that the per feedback loop uses lights-off as a phase reference point and suggest (along with previous findings for per01 and tim01) that per mRNA cycling is not regulated via simple negative feedback from the per protein.

Animals↗
PubMed1996

Developmental state and the circadian clock interact to influence the timing of eclosion in Drosophila melanogaster.

In Drosophila melanogaster, the emergence of adults from their pupal cases (eclosion) is gated by the circadian clock such that it occurs during a window of approximately 8-10 h starting 1-2 h before lights-on in 12-h light:12-h dark cycles (LD). This gate is shifted several hours earlier by the clock mutant per(s), indicating that the clock controls the phase of eclosion under these conditions. Both the day and the time of eclosion are determined by the interplay between developmental state and the circadian clock. At a certain phase of the circadian cycle, the circadian clock, either directly or through some circadian clock-controlled mechanism, measures development state, and those pharate adults that have reached a certain developmental state by this phase eclose during the first available gate, while those that have not wait until a subsequent gate. Using wing pigmentation as a late developmental state marker, an early boundary for when the circadian clock assesses developmental state occurs roughly at the time when lights go out during LD cycles. This event is shifted several hours earlier in per(s), showing that it is under circadian control. A fly's developmental state at the time of developmental assessment also influences when eclosion will occur (during the gate) in that flies whose wings have become pigmented early (12-24 h before assessment) will eclose earlier in the gate than those whose wings become pigmented late (0-12 h before assessment). These data suggest that the circadian clock (or some clock-controlled mechanism) measures developmental state (wing pigmentation) in wild-type flies between lights-off and expression of the first clock-regulated marker approximately 4-5 h before eclosion and that the developmental state of the fly determines both which gate is chosen for eclosion and when eclosion occurs during that gate.

Animals↗
PubMed1996

[Observation on activity of carbonic anhydrase in the vestibule of guinea pigs].

The localization of carbonic anhydrase (CA) activity in the inner ear vestibule of guinea pigs were studied by histochemistry and cytochemistry. We found that numerous enzymatic reaction products were localized in the sterecocilia, cuticles of hair cells, no reaction product was seen in their cell bodies; revealed reaction products in the cell membrane, microvilli, lateral infolding and basolateral infolding of the supporting cell, dark cell, transitional cell and wall cell. It is suggeated that the CA is a membrane-associated CA and the membrane-associated CA plays an important role in the homeistasis of the vestibule and otolithic metabolism.

Animals↗
PubMed1995

Temporal and spatial expression of an adult cuticle protein gene from Drosophila suggests that its protein product may impart some specialized cuticle function.

An adult cuticle protein gene (Dacp-1) from Drosophila melanogaster has been isolated and characterized. This gene was classified as an adult cuticle protein gene because it maintains the conserved structure of other cuticle protein genes, the sequence of its conceptual translation product contains a repeated motif that is found almost exclusively in a subset of adult cuticle proteins from Locust migratoria, and the gene is expressed in the epidermis underlying the head and thoracic cuticle. The bulk of Dacp-1 expression starts approximately 72 hr after pupariation, peaks approximately 12 hr after eclosion, and decreases thereafter to undetectable levels by 3 days after eclosion. The stage specificity and spatial restriction of Dacp-1 expression as well as the physical properties of its conceptual translation product suggest that it may be involved in some specialized function such as thickening of the adult cuticle.

Amino Acid Sequence↗
PubMed1995

DNA topoisomerase II isozymes involved in anticancer drug action and resistance.

DNA topoisomerase II is a major protein of the nuclear matrix. The enzyme appears to have a central role in both DNA organization and replication. The importance of nuclear matrix topoisomerase II alpha as a target for certain anticancer agents was evaluated in CEM human leukemia cells. Studies were done to determine the extent to which the alpha (170 kDa) and beta (180 kDa) isozymes of topoisomerase II form covalent enzyme-DNA complexes in whole cells and in the nuclear matrix and nonmatrix fractions of CEM cells that are either sensitive or resistant to topoisomerase II-active anticancer agents. Topoisomerase II alpha was detected in both the high salt-soluble (nonmatrix) and matrix fractions of nuclei from parental CEM cells. Most of the matrix topoisomerase II alpha was tightly bound to DNA in cells incubated with VM-26. In contrast, topoisomerase II beta was detected only in the high salt-soluble (nonmatrix) fraction of the nucleus. The subnuclear distribution of the alpha and beta topoisomerase II isozymes in CEM/VM-1 cells resistant to topoisomerase-active drugs was similar to that in drug-sensitive CEM cells. However, the amount and activity of topoisomerase II alpha in nuclear matrices of CEM/VM-1 cells were decreased 3- to 6-fold relative to that of CEM cells. The differences observed in the subnuclear distribution and DNA binding pattern of the topoisomerase II isozymes support the hypotheses that each isozyme has a distinct cellular function. Furthermore, these results provide evidence that topoisomerase II alpha is the nuclear matrix target for VM-26, and that depletion of the nuclear matrix isozyme contributes to cellular resistance to this anticancer agent.

Adenosine Triphosphate↗
PubMed1995

Effects of chronic low-dose cyclophosphamide exposure on the nuclei of rat spermatozoa.

Previous studies from our laboratory have shown that chronic exposure of the father to low doses of cyclophosphamide results in a significant increase in early embryonic death with little effect on the male reproductive system in rats. Such effects on progeny outcome are hypothesized to be mediated by an action of the drug on the nucleus of spermatozoa. The purpose of the present studies was to investigate the effects of cyclophosphamide treatment for 1 or 6 wk on the pattern of decondensation of sperm nuclei and on the sulfhydryl content of sperm nuclear proteins. Adult male rats were treated with cyclophosphamide (6.1 mg/kg/day) daily for 1 or 6 wk. Cauda epididymal spermatozoa were collected, demembranated, and then incubated with dithiothreitol (DTT) and proteinase K. The in vitro decondensation pattern of the nuclei of spermatozoa was divided into two phases: nuclear swelling and nuclear elongation. Spermatozoa from animals treated for 1 wk with cyclophosphamide showed the same decondensation pattern as those treated with vehicle (saline) alone. However, spermatozoa from animals treated for 6 wk with cyclophosphamide showed normal initial nuclear swelling but had a markedly affected nuclear elongation pattern. The changes with time in the decondensation pattern of these spermatozoa were quantitated by morphometric analysis of the head region of the spermatozoa. The nuclear area, curvature, and length of spermatozoa obtained from chronically drug-treated males were all significantly smaller than for those obtained from controls, while cell diameter was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Damage to rat spermatozoal DNA after chronic cyclophosphamide exposure.

Treatment of male rats with low dosages of cyclophosphamide causes a dramatic increase in early embryo death among their progeny without significantly affecting the general health of the male. It is hypothesized that cyclophosphamide exerts its effects by targeting specific components of spermatozoal nuclei. The purpose of the present studies was to investigate the effects of chronic cyclophosphamide treatment on spermatozoal DNA. Two approaches were pursued. The first was to determine total DNA damage by using the alkaline elution method. The second was to study spermatozoal DNA template function by using an in vitro DNA synthesis system. Adult male rats were treated with saline or cyclophosphamide (6.1 mg/kg/day) daily for 1 or 6 wk. Cauda epididymal spermatozoa were collected and subjected to alkaline elution using DNA-DNA dot hybridization to quantify the fractionated DNA. One week of treatment with cyclophosphamide caused DNA single strand breaks that could be detected only in the presence of proteinase K in the lysis solution; no DNA cross-links were observed in the animals that received 1-wk drug treatment. In contrast, 6 wk of treatment with cyclophosphamide induced a significant increase in both DNA single strand breaks and cross-links in spermatozoal nuclei; the cross-links were attributable primarily to DNA-DNA linkages. The availability of spermatozoal DNA for template function was not affected by 1 wk of treatment with cyclophosphamide but was markedly affected after 6 wk of treatment with this drug. It is proposed that during chromatin transition processes the male genome may be in an open dynamic state with many exposed sites that are vulnerable to alkylating agents. Since there is no DNA repair during spermiogenesis, damage to the genome by alkylation at this stage may be cumulative, resulting in the production of dysfunctional germ cells.

Animals↗
PubMed1995

[Influence of PGE2 on the oxidative modification of LDL and the scavenger receptor activities of macrophages].

The influence of oxidized LDL (OX-LDL) on scavenger receptor of macrophages and the protective effects of PGE2 and selenium was studied by means of BA-ELISA technique, immunohistochemical methods and oil red O histochemistry. The results indicated that the scavenger receptor activities of macrophages in two treated groups were much lower than that of OX-LDL group. Oil red O staining showed that the macrophages in OX-LDL group were full of fatty drops and became foam cells while little lipid could be found in the treated groups. Immunohistochemical study revealed that the entry of OX-LDL into the macrophages was by way of scavenger receptors. The results confirmed that both PGE2 and selenium had marked antioxidizing effects and that PGE2 was slightly more effective than selenium.

Animals↗
PubMed1995

Experimental study on antiatherosclerotic treatment by PGE2 combined with vitamin E and estradiol.

The effects of single dose of PGE2 combined with vitamin E and with estradiol on experimental atherosclerosis were studied by means of morphological, ultrastructural, autoradiographic and several functional techniques. The results showed that two combined treatment groups had more coordinative inhibition on aortic and coronary atherosclerotic lesions, as well as on platelet aggregation, smooth muscle cell proliferation and lipid peroxidation than that of single dose of PGE2. It was revealed that the coordinative mechanism might be closely related to the synergistic inhibitory function of above-mentioned drugs on endothelial permeability, platelet aggregation, smooth muscle cell proliferation and lipid peroxidation.

Animals↗