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Biomedical subjects

F Dong

Publications and source records attributed to F Dong.

At least 127 records · Page 7Linked to original sources
PubMed1995

[Changes of proteoglycans in lumbar intervertebral disc of bipedal rats with aging].

Using a computer based image analysis system and histological sections stained with Safranin O, we investigated systematically the variation of proteoglycans (PG) contents in the low lumbar discs of bipedal rats. Topographically, the PG concentration increased from the outer annulus to the inner nucleus pulposus region, which possesses the highest PG concentration. The PG content decreased with age, and a significant loss of PG was observed in the lumbar discs of bipedal rats as compared with controls, especially in the nucleus pulposus. These observations support the view that the higher abnormal mechanical stress accelerates disc degeneration.

Aging↗
PubMed1995

[An experimental study on the relationship between disc nutrition and disc degeneration].

Micro-angiography, scanning electron microscopy and hydrogen washout technique were used to investigate the disc nutrition condition and the nutritional pathway of endplate in bipedal rats with agting. Compared with the controls, the nutrition condition of bipedal rats underwent deterioration and the number of vascular distribution under the endplate decreased significantly, but no increase in thickness of endplate caused by microfractures of subchondral bone and callus formed during the healing process was observed. The abnormal stress may bring about vertebral body intra-osseous circulation disorder and then consequent decrease of vascular channels which related to the disturbance of disc nutrition. This strongly suggested that nutrition conditions of nucleus pulposus were not deteriorated by impaired diffusion capacity, but by decrease of vasculature that contacts with endplate.

Angiography↗
PubMed1995

Hematopoietic growth factor receptors: structure variations and alternatives of receptor complex formation in normal hematopoiesis and in hematopoietic disorders.

Receptors of most hematopoietic growth factors are structurally related and grouped in the hematopoietin or cytokine receptor superfamily. In this paper, we will first review the general principles of hematopoietin receptor complex formation and cytoplasmic signaling. Subsequently, the significance of defective hematopoietic growth factor receptors for the development of hematological diseases will be discussed.

Amino Acid Sequence↗
PubMed1995

[Posterior chamber intraocular lens implantation in the absence of posterior capsular support].

The authors retrospectively studied the clinical records of 15 eyes without posterior capsular support receiving transscleral ciliary sulcus fixation of posterior chamber intraocular lenses. Postoperative followup period range from 2 weeks to 8 months, an average of 2.2 months. Postoperative visual acuity improved in all patients, 20% of which had 0.6 or better and 40%-between 0.2 and 0.5. Lens rotation was the primary complication and accounted for poor acuity in some cases. The results indicate that ciliary sulcus fixation in the absence of posterior capsular support appears to be safe and effective and may represent a significant advance in anterior segment surgery.

Adolescent↗
PubMed1995

Regulation of cyclin E and p27kip during mitosis in BALB/c 3T3 cells.

We have examined the level of cyclin E, a G1 cyclin, and p27kip, a cyclin-dependent kinase inhibitor, in BALB/c 3T3 cells. Cell populations stimulated to undergo cell cycle traverse displayed little change in the level of cyclin E, while p27kip was found to be reduced 50-80% in proliferating cells. Analysis of mitotic cells, however, revealed that cyclin E is virtually absent and begins to reaccumulate soon after mitosis is complete, as does p27kip. Immunoprecipitation experiments revealed that p27kip is associated with cyclin E in quiescent but not proliferating cells, indicating that it may function to prevent development of cyclin E activity in the absence of growth factors. Based on our characterization of cyclin E and p27kip in BALB/c 3T3 cells during progression of the cell cycle, we propose a model of growth regulation controlling the G1 phase of growing and quiescent cells involving mitotic degradation of cyclin E and recovery of p27kip inhibitory activity in a late or postmitotic interval.

3T3 Cells↗
PubMed1994

Identification of a nonsense mutation in the granulocyte-colony-stimulating factor receptor in severe congenital neutropenia.

Severe congenital neutropenia (Kostmann syndrome) is characterized by profound absolute neutropenia and a maturation arrest of marrow progenitor cells at the promyelocyte-myelocyte stage. Marrow cells from such patients frequently display a reduced responsiveness to granulocyte-colony-stimulating factor (G-CSF). G-CSF binds to and activates a specific receptor which transduces signals critical for the proliferation and maturation of granulocytic progenitor cells. Here we report the identification of a somatic point mutation in one allele of the G-CSF receptor gene in a patient with severe congenital neutropenia. The mutation results in a cytoplasmic truncation of the receptor. When expressed in murine myeloid cells, the mutant receptor transduced a strong growth signal but, in contrast to the wild-type G-CSF receptor, was defective in maturation induction. The mutant receptor chain may act in a dominant negative manner to block granulocytic maturation.

Antibodies, Monoclonal↗
PubMed1994

[Comparative study of three different hip function evaluation systems].

Harris's, Charnley's and Beijing's numerical rating systems were used to evaluate the functional results of 42 cases of bipolar type artificial femoral head replacement. The results of assessment of the three methods were compared statistically and proved that the results are comparable. Before the overall evaluation, the patients should be divided into three groups (according to Charnley's method) on the basis of their original capacity of locomotion. The score results of the three groups should not be mixed up. The calculation method of total score of Beijing system may need certain modification. The advantages and disadvantages of the three systems, the significance of capacity assessment of daily activity and radiological evaluation are discussed on the basis of the results of analysis.

Aged↗
PubMed1993

Synthesis, characterization, and antioxidative activity of new vitamin B6 triethanolamine rare earth (III) complexes.

A series of new vitamin B6 triethanolamine rare earth (III) complexes Re(PN)3(TEA)(NO3)2Cl (PN = pyridoxol; TEA = triethanolamine; Re = La1, Ce2, Pr3, Nd4, Sm5, Tb6, Dy7, Ho8, Er9, Y10), were synthesized and characterized by elemental analysis, molar conductance, TGA-DTA, UV, IR, and 1H NMR spectroscopic techniques. The suppression ratio of complexes for the hydroxyl radical (OH.) and the superoxide radical (O2-.) were determined, the results show that these complexes possess scavenging effects on OH. and O2(-.). In this paper we also discuss the effect of complex conc. for the suppression ratio on superoxide radical O2(-.).

Antioxidants↗
PubMed1993

Distinct cytoplasmic regions of the human granulocyte colony-stimulating factor receptor involved in induction of proliferation and maturation.

The granulocyte colony-stimulating factor receptor (G-CSF-R) transduces signals important for the proliferation and maturation of myeloid progenitor cells. To identify functionally important regions in the cytoplasmic domain of the G-CSF-R, we compared the actions of the wild-type receptor, two mutants, and a natural splice variant in transfectants of the mouse pro-B cell line BAF3 and two myeloid cell lines, 32D and L-GM. A region of 55 amino acids adjacent to the transmembrane domain was found to be sufficient for generating a growth signal. The immediate downstream sequence of 30 amino acids substantially enhanced the growth signaling in the three cell lines. In contrast, the carboxy-terminal part of 98 amino acids strongly inhibited growth signaling in the two myeloid cell lines but not in BAF3 cells. Truncation of this region lead to an inability of the G-CSF-R to transduce maturation signals in L-GM cells. An alternative carboxy tail present in a splice variant of the G-CSF-R also inhibited growth signaling, notably in both the myeloid cells and BAF3 cells, but appeared not to be involved in maturation.

Animals↗
PubMed1993

[The contributions of facet joint to the stiffness of the lumbar spine].

In this paper, the changes in the stiffness of eight lumbar spinal segments, as affected by left unilateral partial or total facetectomy, were investigated by means of an electro-mechanical technique. The results showed that with unilateral facetectomy, the stiffness of lumbar spinal segment was 39% less in axial rotation, 14% less in extension, 13% less in lateral bending and 9% less in flexion. This observation suggests that in general clinical practice, close attention must be paid to the patients with facet injury, because in this situation the ability of lumbar spine in resisting torque may be decreased significantly.

Adult↗
PubMed1992

Role of the histone "tails" in the folding of oligonucleosomes depleted of histone H1.

An oligonucleosome 12-mer was reconstituted in the absence of linker histones, onto a DNA template consisting of 12 tandemly arranged 208-base pair fragments of the 5 S rRNA gene from the sea urchin Ly-techinus variegatus (Simpson, R. T., Thoma, F. S., and Burbaker, J. M. (1985) Cell 42, 799-808). The ionic strength-dependent folding of this nucleohistone complex was compared with that of a native oligonucleosome fraction obtained from chicken erythrocyte chromatin, which had been carefully stripped of linker histones and fractionated in sucrose gradients. The DNA of this native fraction exhibited a narrow size distribution centered around the length of the 208-12 DNA template used in the reconstituted complex. These two complexes displayed very similar hydrodynamic behavior as judged by sedimentation velocity analysis. By combining these data with electron microscopy analysis, it was shown that the salt-dependent folding of oligonucleosomes in the absence of linker histones involves the bending of the linker DNA region connecting adjacent nucleosomes. It was also found that selective removal by trypsin of the N-terminal regions ("tails") of the core histones prevents the oligonucleosome chains from folding. Thus, in the absence of these histone domains, the bending of the linker DNA necessary to bring the nucleosomes in contact is completely abolished. In addition to the complete lack of folding, removal of the histone tails results in an unwinding at low salt of a 20-base pair region at each flanking side of the nucleosome core particle. The possible functional relevance of these results is discussed.

Animals↗
PubMed1992

[The biological fixation strength of the bone particle impregnated bone cement].

This article reports the result of the comparative study on the biological fixation strength of two kinds of bone particle impregnated bone cement. Organic and inorganic bone particle impregnated bone cement were implanted into alternative side of the upper femurs of New Zealand rabbits. The cancellous bone and cortical bone segments of the implanted femurs removed at intervals of 1, 2 and 3 months after operation were subjected to push-out test. In cancellous bone segment, shearing strength of cement-bone interface was increased gradually, but no significant difference between these two kinds of cement after 3 months operation. In cortical bone segment, the interface shearing strength was lower than that of the cancellous bone, but it increased rapidly from 1 month, especially for the organic bone particle bone cement, after 3 months operation the interface shearing strength had a significant difference between the two kinds of cement. More prominent biological fixation effect showed in the organic bone particle group.

Animals↗
PubMed1991

Nucleosome positioning is determined by the (H3-H4)2 tetramer.

It is demonstrated that the histone (H3-H4)2 tetramer can find specific positions on DNA, even in the absence of other histones. Purified histone (H3-H4)2 tetramers were reconstituted onto 208-base-pair (bp) DNA molecules containing a nucleosome-positioning sequence by using salt-gradient dialysis. The stoichiometry of histone tetramer to DNA was shown to be 1:1. Digestion with micrococcal nuclease led to formation of protected DNA fragments of approximately 73 bp. Cleavage of the 73-bp DNA with restriction enzymes produced a small set of defined bands, demonstrating positioning of the (H3-H4)2 tetramer on DNA. Analysis of the restriction digests shows that the 73-bp DNA corresponds mainly to two fragments, one lying on either side of the pseudo-dyad axis of the major position adopted by complete histone octamers on this DNA. This result means that a single (H3-H4)2 histone tetramer can fold approximately 146 bp of DNA with the same positioning as the complete octamer but that a region near the pseudo-dyad is only weakly protected against micrococcal nuclease attack in the absence of histones H2A and H2B.

Animals↗
PubMed1990

Analysis of the changes in the structure and hydration of the nucleosome core particle at moderate ionic strengths.

In order to better understand the conformational changes induced in the nucleosome core particle by changes in the ionic strength of the media in the range from 0.1 to 0.6 M NaCl, we have conducted a very detailed structural analysis, combining circular dichroism, DNase I digestion, and sedimentation equilibrium. The results of such analysis indicate that the secondary structure of both DNA and histones exhibits small (approximately 5%) but noticeable changes as the salt increases within this range. In the case of DNA, the data are consistent with a trend toward a more relaxed secondary structure. The DNase I pattern of digestion is also altered by the salt and suggests a DNA relaxation around the flanking ends. From the hydrodynamic measurements, we also observe a significant change in the virial coefficients of the particle as the salt increases, which in turn are in very good agreement with the theoretically expected values. Furthermore, the preferential hydration parameter is also found to increase with the salt. We believe that the self-dependent conformational change of the nucleosome core particle is the result of the conjunction of all these subtle changes. Yet, from the present data, their exact relationship to the tertiary structure of the whole particle at the different ionic strengths cannot be exactly defined.

Circular Dichroism↗
PubMed1990

DNA and protein determinants of nucleosome positioning on sea urchin 5S rRNA gene sequences in vitro.

DNA and protein determinants of nucleosome positioning have been examined after in vitro reconstitutions of native or modified histone octamers onto tandem repeats of 207- and 172-base-pair DNA sequences containing the Lytechinus variegatus 5S rRNA gene and onto monomeric sequences derived from these by digestion with various restriction endonucleases. In all cases, a major nucleosome position as well as a number of minor positions have been observed, which indicates that the generation of multiple positions is an inherent property of the 5S rRNA gene sequence. Interestingly, all positions observed differ by multiples of 10 base pairs. Data obtained under different reconstitution conditions demonstrate that the observed distributions of nucleosomes on these DNA templates are equilibrium distributions. This study has also examined the positioning of histone octamers from which histone "tails" had been removed by tryptic digestion. Results indicate that the histone tails are not determinants of nucleosome positioning. Although our results suggest that the mechanical properties of the 5S rDNA are the fundamental factors determining nucleosome positioning, they are insufficient to direct all nucleosomes into a single location.

Animals↗
PubMed1990

[Rapid detection of human cytomegalovirus DNA in urine samples by polymerase chain reaction in vitro gene amplification].

In the detection of human cytomegalovirus (HCMV) DNA in the urine by polymerase chain reaction (PCR). We have designed and synthesized two pairs of oligonucleotide primers (patent pending) corresponding to the specific and conserved DNA sequences of HCMV AD 169 strain. The sequences of the primers were checked that they did not have cross reaction with either normal human genomic DNA or with other herpesviruses. As less as 1fg of HCMV DNA (equal to the amount of DNA from four HCMV virions) in urine can be detected by the method A total of 47 urine specimens from infants suspected of HCMV infection was examined by PCR and conventional virus isolation simultaneously 31 samples were positive in both PCR and virus isolation; 12 samples were negative in either; 4 samples were positive in PCR but negative in virus isolation. So the samples were further examined by serology and the data showed that there was HCMV-specific IgM in all the virus isolation negative sera examined. The result suggests that HCMV in the above samples is possibly underdetected by virus isolation. Therefore the method described in the paper is a specific, sensitive, rapid conventional and non radioisotopic one for detection of HCMV in urine samples.

Cytomegalovirus↗