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Biomedical subjects

G Zhang

Publications and source records attributed to G Zhang.

At least 703 records · Page 39Linked to original sources
PubMedDate not supplied

Localization of pre-mRNA splicing in mammalian nuclei.

In mammalian nuclei, precursor messenger RNA splicing factors are distributed non-uniformly. Antibodies directed against structural polypeptides of small nuclear ribonucleoprotein particles (snRNPs) and some non-snRNP splicing factors have shown that these components are concentrated in about 20-50 nuclear 'speckles'. These and other non-homogeneous distributions have been proposed to indicate nuclear 'compartments' that are distinct from the sites of transcription and in which RNA processing occurs. We have tested this idea using a new approach. Previous structural and biochemical data have shown that splicing can occur in association with transcription. Nascent RNA of specific genes can be detected by in situ hybridization as intense spots of nuclear stain which map to the sites of transcription. Here we identify active pre-mRNA splicing sites by localizing the nascent spliced mRNA of specific genes. We find that splicing occurs at the sites of transcription, which are not coincident with intranuclear speckles. We conclude that the nucleus is not compartmentalized with respect to transcription and pre-mRNA splicing.

Actins↗
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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↗
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Porcine antimicrobial peptides: new prospects for ancient molecules of host defense.

Antimicrobial peptides (AMPs) are small, endogenous, polycationic molecules that constitute a ubiquitous and significant component of innate immunity. These natural antibiotics have broad microbicidal activity against various bacteria, fungi, and enveloped viruses. Because most AMPs kill bacteria by physical disruption of cell membranes, which may prevent microorganisms from developing resistance against these agents, they are being explored as possible alternatives to conventional antibiotics. Pigs, like many other mammals, produce an impressive array of AMPs, which are synthesized predominantly by host leukocytic phagocytes or mucosal epithelial cells. Currently, more than a dozen distinct porcine AMPs have been identified and a majority belongs to the cathelicidin family. This review briefly summarizes recent advances in porcine AMP research with an emphasis on the diverse biological functions of each peptide. Mechanisms of action of these AMPs and their role in the resistance to infections are considered. Finally, the current status of pharmaceutical and agricultural uses of AMPs as well as future prospects for their application in the food animal industry is discussed.

Amino Acid Sequence↗
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An allelic variant at the ATM locus is implicated in breast cancer susceptibility.

We have tested a simple procedure, disease association by locus stratification, for identifying breast cancer patients with pathogenetic allelic variants at several candidate loci. The strategy was based on the assumption of epistatic interactions of the candidates. We analyzed 66 independent cases from sib pairs affected with breast cancer that had previously been collected during an investigation of pathogenetic-allele-sharing at the HRAS1 mini-satellite locus. An exon 24 polymorphism of ATM, substituting arginine for proline was associated with breast cancer in these cases with an overall odds ratio of 4.5 (95% confidence interval, 1.2-20.5, nominal p = 0.02, 2-tail Fisher exact test). In the presence of a rare HRAS1 allele, the odds ratio increased to 6.9 (95% CI, 1.2-38.3, p = 0.03). Thus, our procedure identified at least one allelic variant of ATM associated with breast cancer, and indicated that the ATM locus may interact with HRAS1.

Adult↗
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Induction of G1 arrest and differentiation in MDA-MB-231 breast cancer cell by boehmeriasin A, a novel compound from plant.

Boehmeriasin A is a new phenanthroquinolizidine alkaloid recently isolated from the Boehmeria siamensis Craib (Urticaceae). In vitro biological activity assay demonstrated that this novel compound has wide-range, strong antitumor activity. This study is aimed to determine the effects of boehmeriasin A on breast cancer cell (MDA-MB-231 cell line). Proliferation assay and fluorescence activated cell sorter (FACS) showed that cell growth inhibition and G1 phase arrest of cell cycle were caused by boehmeriasin A. The concentrations resulting in total and 50% growth inhibition are 0.007 and 0.0035 microg/mL, respectively. Exposed in 0.007 microg/mL boehmeriasin A for 12 h, the G1 phase cell percent increased from 44.8% pre-drug treatment to 66.3%. Consistent with G1 arrest and cell growth inhibition, cyclin E2 and cyclin D1 messenger RNA expression in the cell was down-regulated with drug treatment. Then, few apoptotic cells were detected, and most other cells underwent differentiation, which is characterized by specific changes in cell morphology, lots of lipid droplet accumulation, and increasing expression of adipocyte differentiation-related protein. The result first demonstrates that boehmeriasin A potently inhibits the proliferation of breast cancer cell MDA-MB-231 via the G1 phase cell cycle arrest and differentiation induction, and as such, may be considered as candidate chemotherapeutic and/or chemopreventive agent for breast cancer.

Apoptosis↗
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Role of apoptosis and Bcl-2/Bax in the development of tubulointerstitial fibrosis during experimental obstructive nephropathy.

BACKGROUND/AIMS: To examine the role of apoptosis in experimental unilateral ureteral obstruction (UUO). METHODS: Rat kidneys were examined 3, 7 and 11 days following UUO or sham operation (SO). Tissue was immunohistochemically stained for alpha-smooth muscle actin (alpha-SMA), proliferating cell nuclear antigen (PCNA), Bcl-2 and Bax proteins. Apoptotic analysis was carried out in kidney sections using in situ end labelling of endonuclease cleaved DNA. RESULTS: The relative volume (Vv) of cortical interstitium and interstitial alpha-SMA increased progressively following UUO. ED1-positive monocytes/macrophages peaked at day 7 and significantly decreased at day 11. PCNA-positive cells in tubulointerstitium were significantly increased on day 3. Staining returned to the level of the SO group by day 11, meanwhile those in the interstitium remained much higher than baseline. TUNEL-positive cells were persistently raised following UUO. Transient tubular cell proliferation seemed unable to counteract the apoptosis since tubular atrophy was apparently present by day 11 of UUO. However, interstitial cell proliferation was high enough to overwhelm apoptosis, particularly with respect ot myofibroblasts, since alpha-SMA immunostaining and Vv remained elevated. The ratio of the number of PCNA-positive cells to apoptotic cells formed a predictive pattern for the staining score of interstitial alpha-SMA (R(2) = 47.23%, p < 0.05) and Vv (R(2) = 49.93%, p < 0.05). Tubular Bcl-2 immunostaining peaked on day 3, and then gradually decreased to baseline by day 11. The expression of Bax protein was inhibited on day 3 when compared with that of the SO group, but increased with time following UUO. CONCLUSION: These findings suggest an important role for apoptosis and its regulatory proteins in the processes of tubular atrophy and fibrogenesis following UUO.

Actins↗
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Haptoglobin types in Chinese ethnic groups.

The distribution of haptoglobin (HP) types was examined in six different Chinese ethnic groups. The gene frequencies were compared among these groups and to those reported in other Chinese Han populations. The effects of sex and age on the distribution of HP types are also discussed.

Adolescent↗
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Haptoglobin groups and cirrhosis of the liver.

Haptoglobin (HP) groups were determined in Chinese patients suffering from eight different diseases and compared to those of 552 control subjects. Patients with cirrhosis of the liver showed a significant difference from controls in the distribution of HP types (p = 2 x 10(-4)), with increases in the HP*1 allele and HP1-1 phenotype frequencies. The relative risk for the HP1-1 phenotype was 3.3.

Alleles↗
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The laser two-photon photolysis of liquid carbon tetrachloride.

The two-photon photolysis of liquid CCl4 with 25 ps pulses of 266 nm light has been studied and compared with similar studies with high energy radiation. Both neutral and ionic species are produced from excited states and ionization. The emphasis of the study is on the ionic processes, while some data related to excited states and free radicals are presented. In both radiolysis and photolysis, a solvent separated charged pair, CCl3+ // Cl-, exhibiting a lambda(max) at 475 nm, is observed that exhibits a total growth over 38 to 100 ps. Solutes with ionization potentials less than that of CCl4 (11.47 eV) reduce the yield of the 475 nm species producing radical cations of the solute. The efficiency of this process is about 10-fold larger in radiolysis compared with photolysis. Analysis of the data suggest that the lower energy of two-photon photolysis produces a charge pair CCl4+ // CCl4-, which decays in about 3 ps to CCl4+ // Cl-. This species then decays to CCl3+ // Cl-. The lifetime of the growth of the 475 nm is measured as 46 ps. These studies clearly show areas where radiolysis and photolysis can be quite similar and also areas where the vast difference in excitation energy introduces stark differences in the observed radiation and photoinduced chemistry.

Carbon Tetrachloride↗
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Topographical distribution of electroretinographic potentials monitored by skin-electrodes.

Electroretinographic recordings were made from 20 different skin points by skin-electrodes when the eye was fixed in a straight forward, lateral and nasal gaze. Three dimensional distributions of the percent amplitude of the b-wave were made using a microcomputer. The best recordings were obtained upon lateral gaze from skin points on the lower eye lid or near the lateral canthus. The skin-electrode ERG recording from these skin points upon lateral gaze may provide a useful diagnostic tool, especially in young children.

Action Potentials↗
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Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part I--General considerations and summary of results.

Recurrent plantar ulceration is a common and serious complication occurring consequent to impairment of the tibial nerve in leprosy patients. In spite of many therapies and long therapeutic course, it is extremely difficult to abolish this complication in many cases because of extensive skin and soft tissue cushion loss due to repeated infection. Since the early 70's we have been using microscopic surgical techniques to reconstruct the ulcerated area using eight types of the flaps. In this series of papers we review our experience (76 patients). Post-operatively, the flaps survived in all cases, the long-term results have proved satisfactory, and recurrent ulceration occurred in only three patients.

Adult↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part II--First toe web and dorsal foot flaps.

The first toe web flap consists of the skin and subcutaneous tissues of the contiguous sides between the great and second toes. It is based on the first dorsal metatarsal artery or the common plantar digital artery. This flap was used as artery pedicled island graft to reconstruct losses of skin and soft tissue cushion in the ball of the foot in the first and second metatarsal head region in 16 cases. Follow-up examination revealed that ulceration had recurred in one case due to dehiscence of the flap margin 12 months post-operatively. The other 15 patients have done well without recurrence at 48 to 124 months follow-up examination. The dorsal flap of the foot based on the dorsalis pedis artery, the corresponding veins and the deep peroneal nerve was designed in 1974 to resurface skin and soft tissue defects in the sole of the foot. This flap was used in 30 cases of leprosy with excellent results. During follow-up 36 to 120 months after surgery the plantar ulcer had recurred in only one case. All the others have done well. The long-term curative effect has thus proved satisfactory.

Foot Ulcer↗
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Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part III. Use of plantar skin or musculocutaneous flaps and anterior leg flap.

Anatomical studies suggest that five types of plantar flaps namely, the lateral and medial plantar flaps, the Abductor hallucis-, the Flexor digitorum brevis-, and the Abductor digiti minimi-myocutaneous flaps, can be incised from the central section of the sole. The advantages of a plantar flap are recognizable neurovascular bundles of the sole, wide calibre of constantly located blood vessels, identical histological structure of the donor and the recipient sites, hidden donor site and absence of functional deficit. We have used the plantar flaps in seven cases. There has been no recurrence of ulceration in any of them during the follow-up period of 12 to 108 months. An anterior leg flap based on the cutaneous branches of the anterior tibial artery, with firmly anchored vessels, a long pedicle with wide vessels may be used not only as a free flap graft for reconstruction of moderate degree distant defects but also as a retrograde island flap graft for the reconstruction of adjacent tissue defect. We have used the retrograde island flap graft based on the anterior tibial artery in five cases of plantar ulceration with satisfactory results. There was no recurrence of ulceration during the follow-up period of 48 to 72 months.

Foot↗
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Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part IV. Use of medial leg flap and medial knee flap.

The medial leg flap, based on the cutaneous branches of the posterior tibial artery is raised from the middle and lower regions of the medial aspect of the leg. It has a long pedicle, and it can be used as a free flap to reconstruct the distant soft tissue defects and also as an island flap. We have used this retrograde island flap for surfacing ulcerated areas in six leprosy patients. The flap survived in all cases. At 24 to 60 months follow-up examination, ulceration had not recurred in any of them. The medial knee flap consisting of the skin and subcutaneous tissue of the lower part of the medial side of the thigh and the upper part of the leg, is suitable for covering soft tissue cushion defects of the extremities because of the constant vessels, long pedicle, wide diameter, well-recognizable sensory nerves and less subcutaneous fat. We have used the medial knee flap for the resurfacing sizeable raw areas due to ulceration in three leprosy patients. The flap survived in all cases and there was no recurrence of ulceration during the 70-148 months follow-up period.

Foot Ulcer↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part V. Use of the flap in the inguinal region and latissimus dorsi musculocutaneous flap.

The area of distribution of the superficial circumflex iliac, superficial epigastric and superficial external pudental arteries is large and flaps based on them can meet the requirement of different recipient sites. We have transplanted free flaps based on the superficial epigastric artery for repairing plantar soft tissue defects in six leprosy patients. During the follow-up examination 58 to 118 months later there has been no recurrence of ulceration in any of these cases. The latissimus dorsi muscle, is mainly nourished by the thoracadorsal artery and the latissimus dorsi musculocutaneous flap is a large sized, composite structure with abundant blood provision and strong anti-infectious property. The latissimus dorsi flap can be used as an artery-pedicled island flap or as a free flap besides its use as a muscle graft, because of its constant vascular position, wide outer-diameter of the vessels and long pedicle. It can therefore be utilized for repairing soft tissue defect or replacement of paralyzed muscle. We have used the latissimus dorsi musculocutaneous free flap for repairing large skin and soft tissue defects resulting from plantar ulceration in three leprosy patients. During the follow-up period, one patient who had complete drop-foot and had refused corrective surgery had recurrence of the ulcer in the 12th post-operative month. No ulcers had recurred in the other two cases during the follow-up at 48 and 114 months.

Foot Ulcer↗
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Transplantation of fibula with vascular pedicle for fusion of ankle in leprotic drop-foot.

Devascularized bone grafts are pieces of dead bone and they simply serve as scaffolds for new bone to grow and fill the gap, taking a long time when they succeed in doing so. In contrast, vascularized grafts being living tissues have short healing time, great vitality and strong infection-resisting capacity. We report here the successful use of vascularized grafts of the lower end of fibula for fusing the ankle in five leprosy patients.

Adult↗