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Biomedical subjects

X Zhu

Publications and source records attributed to X Zhu.

804 records · Page 45Linked to original sources
PubMedDate not supplied

Near-field mapping of the emission distribution in semiconductor microdiscs.

We have used a scanning near-field optical microscope to study the fluorescent light distribution in the near- and far-fields with two types of microdiscs, InGaP and GaN, fabricated in our laboratory. The InGaP microdisc has a radius of 2.5-5.0 microm, a thickness of 0.15-0.2 microm and a circular shape and the GaN disc has a radius of 5-8 microm with a thickness of 0.5-2 microm. Spontaneous emission enhancement in these microdiscs has been observed with emitting wavelengths of 650 and 550 nm respectively In both types of microdisc, the whispering-gallery mode (WCM) has been observed on the top surface using near-field optical and far-field microscopic methods. However, due to the different disc structures and optical confinements, the light distributions of the type types of disc are quite different. In the case of the InGaP disc, WGM is the dominant mode with a mixture of other modes. Interference-like ring intensities have been observed both inside the disc surface and outside, with a period ratio of 1:2. In addition, the propagating waves emitted from the side of the disc have been collected for the first time by using near-field optical microscopy. A theoretical calculation based on the theory of optical modes in microdisc lasers confirmed this observation. It also predicted the behaviour of the electric field distribution (transverse electric) inside and outside the disc, as well as the period of the wave propagation. In contrast, the near-field mapping of the GaN fluorescence showed not only a ring-like emission intensity along the circumference of the disc, an indication of WGM, but also an even intensity distribution inside the disc. This can be explained as the combination of the WGM with the Fabry-Perot mode of multi-reflection between the GaN layer and the substrate. The results also demonstrate the potential application of near-field optics to explore the light emission mode of a microdisc on a nanometre scale.

Journal Article↗
PubMedDate not supplied

Expression of cyclin-dependent kinase inhibitors, p21cip1 and p27kip1, during wound healing in rats.

Wound healing is a physiological process in which growth of cells is stringently regulated. Cell growth is controlled by cell cycle-related proteins in which the cyclin kinase inhibitors cause cell cycle arrest and inhibit proliferation. However, little is known about the expression and the role of cyclin kinase inhibitors during wound healing in vivo. This study was mainly designed to examine the expression of p21cip1 and p27kip1 in excisional wounds of full-thickness skin in rats. Concomitant expression of proliferation marker Ki67 was also examined. Proliferation predominantly occurred in the first week after injury, peaking at postwounding day 5. Expression of both p21cip1 and p27kip1 at the gene and protein levels did occur during wound healing and showed an inverse gradient to that of Ki67. Constitutive p27kip1 was expressed throughout wound healing with low levels during the proliferating period of days 3 and 5 and increased levels during post-mitotic and remodeling stages. In contrast, p21cip1 was expressed transiently with detectable levels only between days 7 and 14 by Western blot analysis. Immunohistochemically, epithelial cells, endothelial cells and fibroblasts all could express both p21cip1 and p27kip1. In conclusion, the overall results suggested that p21cip1 and p27kip1 may play a key role in supervising the growth resulting from cell proliferation in tissue repair.

Animals↗
PubMedDate not supplied

Upregulated surface expression of intracellularly sequestered Igepsilon receptors (FcepsilonRII/CD23) following activation in human peripheral blood eosinophils.

We investigated the regulation, secretion, and surface expression of the low-affinity FcepsilonRII receptor (CD23) in eosinophils isolated from human blood using multiple monoclonal antibodies (mAbs) directed at different epitopes of human CD23. Substantial surface expression of CD23 was not demonstrated in the resting state. Mean fluorescence intensity (MFI) measured by flow cytometry was 7. 1 +/- 0.8 for 9P25 mAb (p = NS) and 15.7 +/- 3.8 for BU38 mAb (p <. 04) versus 5.3 +/- 1.0 for IgG1 isotype control Ab. By contrast, MFI using BU38 mAb was 154 +/- 18 for JY-B lymphocytes (p <.0001 versus eosinophils). Despite weak surface expression, eosinophil permeabilization demonstrated substantial intracellular expression of CD23; MFI was 33.6 +/- 5.2 for 9P25 mAb versus 4.4 +/- 0.43 for IgG control (p <.001). Western blot analysis using both positive and negative controls demonstrated immunological identity with CD23 on JY-B lymphocytes. Activation of eosinophils caused rapid translocation of CD23 to the surface membrane (160 +/- 33 MFI; p <. 005), which was maximal within 30 sec. Secretory CD23 was detected within the perfusate also at 30 sec and was fully reinternalized at 10 min. This is the first demonstration of the presence of intracellular CD23 in human eosinophils. Our data indicate that eosinophils rarely express CD23 on their surface but are capable of transient high-level expression and secretion with rapid reuptake of intracellular stores of CD23.

Cells, Cultured↗
PubMedDate not supplied

Solar ultraviolet radiation and skin damage: an epidemiological study among a Chinese population.

To explore skin damage resulting from solar ultraviolet radiation on Mongoloid people, we investigated 470 healthy people in northeast China. We assessed their skin texture and elastic fibers, number of Langerhans cells, and the incidence of p53 gene mutations. The results showed that solar ultraviolet radiation played a significant role in aging of skin in Chinese people; aging began at 30 y of age (i.e., 20 y later than in Caucasians). In the high-exposure group, aging of skin was twice as severe and occurred 10 y earlier than in the low-exposure group. The counts of Langerhans cells had a tendency to decrease in the high-exposure group. Neither p53 mutations nor solar keratosis were found in individuals of any age-findings that indicated a qualitative different pattern than that of Caucasians.

Adolescent↗
PubMedDate not supplied

Perimenstrual symptoms among Chinese women in an urban area of China.

We explored perimenstrual symptoms among 16 Chinese women in an urban area of southeastern China using a retrospective questionnaire, the Menstrual Distress Questionnaire (MDQ), and a prospective daily symptom diary, the Daily Health Diary (DHD), modified for cultural relevance. Mean scores on the DHD were significantly (p < .03) higher during the perimenstrual phase for the symptoms fatigue, increased sensitivity to cold, increased sleeping, abdominal pain/discomfort, painful or tender breasts, and decreased sexual desire. The women who reported higher DHD physical symptom scores prospectively were more likely to recall more severe physical symptoms retrospectively on the MDQ. However, there were remarkable discrepancies between the DHD and MDQ regarding psychoemotional symptoms. By retrospective MDQ, the percentages of women who experienced severe mood swings and irritability ranged from 13% to 25% during the premenstrual and menstrual phases; on the DHDs, however, these emotional symptoms were not statistically associated with the menstrual cycle. The failure of prospective charting to confirm the retrospective reports of cyclic psychoemotional symptoms agrees with findings of studies of U.S. samples. We conclude that perimenstrual distress in Chinese women may be affected by the data collection methods.

Adult↗
PubMedDate not supplied

Ribosomal RNA sequences of Enterocytozoon bieneusi, Septata intestinalis and Ameson michaelis: phylogenetic construction and structural correspondence.

The microsporidian species Enterocytozoon bieneusi, Septata intestinalis and Ameson michaelis were compared by using sequence data of their rRNA gene segments, which were amplified by polymerized chain reaction and directly sequenced. The forward primer 530f (5'-GTGCCATCCAGCCGCGG-3') was in the small subunit rRNA (SSU-rRNA) and the reverse primer 580r (5'-GGTCCGTGTTTCAAGACGG-3') was in the large subunit rRNA (LSU-rRNA). We have utilized these sequence data, the published data on Encephalitozoon cuniculi and Encephalitozoon hellem and our cloned SSU-rRNA genes from E. bieneusi and S. intestinalis to develop a phylogenetic tree for the microsporidia involved in human infection. The higher sequence similarities demonstrated between S. intestinalis and E. cuniculi support the placement of S. intestinalis in the family Encephalitozoonidae. This method of polymerized chain reaction rRNA phylogeny allows the establishment of phylogenetic relationships on limiting material where culture and electron microscopy are difficult or impossible and can be applied to archival material to expand the molecular phylogenetic analysis of the phylum Microspora. In addition, the highly variable region (E. coli numbering 590-650) and intergenic spacer regions in the microsporidia were noted to have structural correspondence, suggesting the possibility that they are coevolving.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Sequence homology among sperm antigens involved in mammalian fertilization: search for a common epitope for immunocontraception.

Sequence homology was searched among the nine cDNAs/deduced amino acid sequences encoding for the eight fertilization-related sperm antigens: namely, lactate dehydrogenase (LDH-C4), galactosyltransferase (GT), SP-10, rabbit sperm autoantigen (RSA), guinea pig (g)PH-20, cleavage signal protein (CS-1), HSA-63, human (h)PH-20, and AgX-1, respectively. Most significant identity (> 50%) was found between HSA-63 and SP-10 (59.8%), and between gPH-20 and hPH-20 (61.1%); followed by identity between SP-10 and GT (34.7%); and then between AgX-1 and hPH-20 (39.4%). All others had identity < 25%. The significance of these sequence homologies among the sperm antigens in the development of an antisperm contraceptive vaccine is discussed.

Animals↗
PubMedDate not supplied

Persantine improves acute pancreatitis in vitro.

Persantine combined with TNF-a enhances antiproliferative activity in human tumor cells. We hypothesized that the vasodilator persantine would ameliorate acute pancreatitis (AP) in vitro. Rat pancreatic ductal cells were cultured using standard techniques. Acute pancreatitis was induced by adding cerulein (10(-9) M) or TNF-a (200 ng/ml). AP was verified by increased amylase production. Persantine was added at concentrations from 0.1 uM to 100 uM post cerulein or TNF-a treatment. Statistical analysis was achieved by ANOVA. Amylase production was significantly increased (p < 0.05) compared with control upon stimulation with either cerulein or TNF-a. When persantine was added in graded concentrations from 0.1 uM to 100 uM to cerulein treated cells, it decreased amylase production significantly (p < 0.05) at 100 uM. However, when persantine was added to TNF-a treated cells, it decreased amylase production (p < 0.05) at the lower concentrations of 0.1 uM and 1 uM. We have shown for the first time that AP, resulting from either mild (cerulein) or severe (TNF-a) stimulation, is significantly improved by treatment with persantine.

Acute Disease↗
PubMedDate not supplied

Synthesis of the pro-peptide of subtilisin BPN'.

Subtilisin, a bacterial serine protease, is secreted as pre-pro-subtilisin. Previously, we demonstrated that the pro-peptide moiety of intact pro-subtilisin can guide the folding of inactive protein to active enzyme both in an intramolecular (6) and intermolecular manner (18). Herein is reported the total chemical synthesis of the pro-sequence (77 amino acids) of pre-pro-subtilisin BPN' carried out by solid phase methods. The structure was confirmed by both sequencing and amino acid analysis of the fragment peptides resulting from a V-8 protease digest. Preliminary studies indicate that the synthetic pro-peptide itself can renature denatured subtilisin BPN'. This study demonstrates a novel method for examining protein folding with the aid of exogenously added synthetic peptides.

Amino Acid Sequence↗
PubMedDate not supplied

Telomeres, telomerase and cancer: is the magic bullet real?

Nature recruited telomerase to compensate for the incomplete replication of chromosomal ends (telomeres). In higher organisms, telomeres are eroded at each cell division. Cancer cells frequently show chromosomal instability resulting in ring chromosomes, telomeric associations, and dicentric chromosomes. As a consequence of telomeric erosion, the ribonucleoprotein complex termed "telomerase" is reactive in a subpopulation of cells. Telomerase adds a hexameric repeat of the sequence 5' TTAGGG 3' to the ends of the chromosomes and hence stabilizes the telomeric length. Telomerase is active in vertebrates mostly in germ cells and the early stage embryo but is inactivated or repressed in somatic cells. Detection of telomerase activity in the overwhelming majority of advanced and metastatic human cancers but not in most somatic cells implies that telomerase-dependent immortalization could contribute to the malignancy. Future studies on the expression and regulation of the individual components of telomerase may enable us to clarify the diagnostic and therapeutic potential of telomerase in cancer.

Animals↗
PubMedDate not supplied

Success factors for the future survival of rural hospitals.

Rural hospitals are among those at greatest risk in the changing world of healthcare delivery. There are, however, those that are continuing to thrive despite the odds. The common thread among these are factors found in select Midwest rural hospitals.

Community-Institutional Relations↗