Biomedical subjects

H Chen

Publications and source records attributed to H Chen.

At least 127 records · Page 7Linked to original sources

PubMed2003

The effect of tension on esophagogastric anastomotic wound healing in rats.

AIM: The effect of tension on the occurrence of esophagogastric anastomotic leaks has been controversial for along time. We used a rat model and investigated the effect of tension on the esophagogastric anastomotic wound healing. METHODS: Eighty Sprague-Dawley rats were divided into 8 groups and each group has 10 rats. A side-to-side single layer esophagogastric anastomosis was constructed using interrupted sutures through laparotomy. Anastomoses were excised on day 0, 3, 5, 7, 14, mounted in an Instronmini-44 Tension meter and distracted at 10 mm/min to measure breaking strength. On the other hand, the increased anastomotic tensions were obtained by increasing the distance between esophageal incision and gastrotomy, and anastomotic leak rates in different anastomotic tension groups were investigated. RESULTS: A total of 11 rats were excluded from the studies because of pulmonary complication. Breaking strength on day 0, 3, 5, 7, 14 were 3.35+/-0.89, 1.18+/-0.31, 1.92+/-0.46,3.47+/-0.83, 5.06+/-1.22 (Newton), respectively. The breaking strength is significantly different between day 0 and day 3, day 5 and day 7, day 7 and day 14 (p<0.05). There is no difference between day 3 and day 5, day 0 and day 7(p>0.05). Breaking strength is lowest on day 3 and close to culmination on day 14. Esophagogastric anastomotic leaks increased along with anastomotic tension increasing. CONCLUSION: Anastomotic tension could be a key factor resulting in esophagogastric anastomotic leaks.

Anastomosis, Surgical↗

PubMed2002

Intakes of vitamins E and C, carotenoids, vitamin supplements, and PD risk.

BACKGROUND: Oxidative damage has been implicated in the pathogenesis of PD. Limited and mostly retrospective epidemiologic data suggest a reduction or no change in risk of PD associated with high vitamin E intake. OBJECTIVE: To examine prospectively the associations between intakes of vitamins E and C, carotenoids, vitamin supplements, and risk of PD. METHODS: The authors documented the occurrence of PD within two large cohorts of men and women who completed detailed and validated semiquantitative food frequency questionnaires. A total of 371 incident PD cases were ascertained in the Nurses' Health Study, which comprised 76,890 women who were followed for 14 years, and the Health Professionals Follow-Up Study, which comprised 47,331 men who were followed for 12 years. RESULTS: Neither intake of total vitamins E or C or use of vitamin E or vitamin C supplements or multivitamins was significantly associated with risk of PD. The risk of PD, however, was significantly reduced among men and women with high intake of dietary vitamin E (from foods only). The pooled multivariate relative risk (RR) comparing individuals in the highest quintile with those in the lowest quintile was 0.68 (95% CI, 0.49 to 0.93). Consumption of nuts was also significantly associated with a reduced risk of PD (for >or=5/week vs <1/month, pooled RR, 0.57; 95% CI, 0.34 to 0.95). Intakes of dietary vitamin C and carotenoids were not significantly associated with risk of PD. CONCLUSIONS: Use of vitamin supplements and high intake of carotenoids do not appear to reduce the risk of PD. The reduction in risk of PD associated with high dietary vitamin E intake suggests that other constituents of foods rich in vitamin E may be protective. Alternatively, moderate amounts of vitamin E may reduce risk of PD, but this benefit may be lost with higher intakes.

Adult↗

PubMed2002

Binding of dentin noncollagenous matrix proteins to biological mineral crystals: an atomic force microscopy study.

Noncollagenous matrix proteins (NCPs) of dental hard tissues (dentin, cementum) are involved, both temporally and spatially, in the mineralization of their collagen matrices. Two of the NCPs thought to initiate mineral nucleation and control crystal growth in dentin, are dentin phosphoproteins (DPP) and dentin sialoprotein (DSP). Control of crystal growth would depend on the binding capacity of these two molecules, which may be related to the charge domains on the crystals and/or the phosphorylation of the protein. Phosphophoryn (a highly phosphorylated DPP) and DSP were isolated, purified, and characterized from the immature root apicies of human teeth. Dephosphorylation of phosphophoryn was carried out using bovine intestinal alkaline phosphatase. Enamel crystals were prepared from the maturation stage of developing rat incisor enamel. Protein-coated crystals were prepared for viewing in an atomic force microscope fluid cell using tapping mode. Desorption of the proteins was achieved using a phosphate buffer and surface roughness measurements were obtained from all specimens. Time-lapsed images of the crystals showed "nanospheres" of protein distributed along the crystals but only the phosphophoryn-coated crystals showed a distinctive banding pattern, which was still visible after the phosphate desorption experiments. The surface roughness measurements were statistically greater (P <0.01) when compared to the control for only the phosphophoryn-coated specimens. It is hypothesized that the phosphophoryn binding may be associated with charge arrays on the crystal surface and its phosphorylation. Also, based on its affinity for the crystalsurfaces, phosphophoryn seems the most likely candidate for controlling dentin crystal growth and morphology.

Crystallization↗

PubMed2002

In vitro and in vivo activity and cross resistance profiles of novel ruthenium (II) organometallic arene complexes in human ovarian cancer.

Ruthenium complexes offer the potential of reduced toxicity, a novel mechanism of action, non-cross resistance and a different spectrum of activity compared to platinum containing compounds. Thirteen novel ruthenium(II) organometallic arene complexes have been evaluated for activity (in vitro and in vivo) in models of human ovarian cancer, and cross-resistance profiles established in cisplatin and multi-drug-resistant variants. A broad range of IC50 values was obtained (0.5 to >100 microM) in A2780 parental cells with two compounds (RM175 and HC29) equipotent to carboplatin (6 microM), and the most active compound (HC11) equipotent to cisplatin (0.6 microM). Stable bi-dentate chelating ligands (ethylenediamine), a more hydrophobic arene ligand (tetrahydroanthracene) and a single ligand exchange centre (chloride) were associated with increased activity. None of the six active ruthenium(II) compounds were cross-resistant in the A2780cis cell line, demonstrated to be 10-fold resistant to cisplatin/carboplatin by a mechanism involving, at least in part, silencing of MLH1 protein expression via methylation. Varying degrees of cross-resistance were observed in the P-170 glycoprotein overexpressing multi-drug-resistant cell line 2780AD that could be reversed by co-treatment with verapamil. In vivo activity was established with RM175 in the A2780 xenograft together with non-cross-resistance in the A2780cis xenograft and a lack of activity in the 2780AD xenograft. High activity coupled to non cross-resistance in cisplatin resistant models merit further development of this novel group of anticancer compounds.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2002

Soft-x-ray spectra of highly charged Kr ions in an electron beam ion trap.

Systematic variation of the electron-beam energy in the EBIT-II electron beam ion trap has been employed to produce soft-x-ray spectra (20-75 A) of Kr with well-defined maximum charge states ranging from Cu- to Al-like ions. Guided by large-scale relativistic atomic structure calculations, the strongest lines have been identified with Delta n=1 (n=3 to n(')=4) transitions from Ni- to P-like ions (Kr(8+)-Kr(21+)), as well as a number of 3p-4d and 3d-5f transitions.

Journal Article↗

PubMed2002

Microvascular permeability of rat cerebral pia mater by using image computer analysis.

UNLABELLED: Microcirculation viviperception and fluorescent tracer techniques were used and digital image analysis applied for quantitative measurement of fluorescein sodium (FiNa) permeability in microvessels of the cerebral pia mater. The diffusion permeation equations of FiNa within the blood vessels and through the vessel walls into the perivascular tissue of normal rats and ischemic rats were established with two vessels as study object, thus the permeation speed equations under different ischemic conditions were deduced. Based on analysis of the results, we deduced the relation between the permeability and the intersection angle of two vessels. RESULT: logarithm model showed a good fit of the experiment data. The permeation equation showed logarithmic distribution and then tended towards stability. FiNa could pass through microvessel walls with the highest speed in the one-hour ischemic rat group, and the permeation speed of FiNa in rats receiving reperfusion after twelve hours of ischemia was much faster than that in normal rats. CONCLUSION: the method can be useful for quantitative analysis of cerebral pia mater microvascular permeability

Algorithms↗

PubMed2002

Evaluation of thermal cycling and mechanical loading on bond strength of a self-etching primer system to dentin.

OBJECTIVE: The aim of this study was to evaluate the in vitro durability and fracture modes of the tooth-resin interface following thermal cycling, fatigue load cycling (FLC) and micro-tensile bond strength testing (MTBS). METHODS: Twenty-four human molars were divided into two groups. In group A, coronal dentin was ground flat with #600-grit SiC paper, Clearfil Linerbond.2V (LB.2V) adhesive was applied and a crown fabricated with Clearfil AP-X resin composite. Samples were loaded in the FLC simulator and thermal cycle device. In group B, Class I cavities were prepared with a diamond bur and the cavity restored with LB.2V/AP-X. Samples were simultaneously subjected to FLC and thermal cycling. After storage of the specimens in water for 1 week, MTBS tests were performed, and fracture modes examined by SEM. RESULTS: For group A, MTBS were approximately 40 MPa with cohesive failures in the bonding resin of all specimens. Neither thermal nor mechanical stressing altered bond strengths on flat dentin surfaces. In group B, MTBS in the unstressed control group was 21 MPa with cohesive failures in the resin. As both thermal and mechanical stresses increased, there was a significant decrease in bond strength (16 MPa, P<0.05) and the fractures were seen in the resin-dentin interface and hybrid layer. SIGNIFICANCE: Surface preparation, C-factor, cavity depth, the dentin substrate and character of the smear layer strongly influence the bond strength values after thermal and fatigue loading. The FLC simulator in combination with MTBS testing provides meaningful in vitro evaluation of dentin bonding durability.

Acid Etching, Dental↗

PubMed2002

Atomic configuration in core structure of Lomer dislocation in Si0.76Ge0.24/Si.

The core structure of a Lomer dislocation in SiGe/Si system has been revealed at atomic level. This is attained by applying the image deconvolution technique in combination with dynamical diffraction effect correction to the high-resolution image taken with a 200 kV field-emission gun high-resolution electron microscope. The Lomer dislocation has a Hornstra-like core. The contrast of the image simulated on the basis of derived atomic configuration is in agreement with that of the experimental image.

Journal Article↗

PubMed2002

Predictors of tolerance to chemotherapy in older cancer patients: a prospective pilot study.

Few data are available to help predict which older cancer patient is at risk of developing chemotherapy-related toxicity. This study was a pilot for a project designing a predictive risk score. Chemotherapy patients aged 70 years and older were prospectively enrolled. Chemotherapies were adjusted for their published toxicity. 60 patients were enrolled, 59 were evaluable. Mean dose-intensity was 90.3%, range 33.3-129.0%. 47% of the patients experienced grade 4 haematological and/or grade 3-4 non-haematological toxicity. Published toxicity (MAX2), diastolic blood pressure, marrow invasion and lactate dehydrogenase (LDH) were all associated with toxicity (P<0.1); Body Mass Index, previous chemotherapy, red blood cells, platelets, polymedication with dose-intensity; and polymedication with FACT-G change. After adjustment for the published toxicity, the variables retained their significance, except for LDH and polymedication (for dose-intensity). Although the size of this pilot study imposes a cautious interpretation, patient-related and chemotherapy-related variables correlated independently with toxicity. Designing a composite predictive score to use in assessing the toxicity of multiple chemotherapy regimens therefore appears to be a valid undertaking.

Aged↗

PubMed2002

Morphology of the dorsal lingual papillae in the Japanese macaque and Savanna monkey.

The dorsal lingual surfaces of infant Japanese macaque (Macaca fuscata) and adult savanna monkey (Cercopithecus aethiopus) were examined by scanning electron microscopy. Filiform, fungiform, foliate and vallate papillae were found. The filiform papillae were distributed over the entire dorsal surface of the tongue. The fungiform papillae were round in shape, and more densely distributed on the lingual apex. The foliate papillae were seen on the dorsolateral aspect of the tongue. The three vallate papillae were arranged like a triangle with the apex of the triangle directing caudally. Each papilla was surrounded by a groove. The rudiments of the fungiform, foliate and vallate papillae were visible earlier than those of the filiform papillae.

Animals↗

PubMed2002

Optometrists' examination and referral practices for patients presenting with flashes and floaters.

INTRODUCTION: Patients experiencing flashes and floaters commonly present to their optometrist. Some of these patients may have significant pathology, yet there is a great deal of variability with regard to examination technique and referral practice. METHODS: A questionnaire survey was undertaken to determine the current management of patients presenting to their optometrist with flashes and floaters. All practising community optometrists within Southern Derbyshire received a questionnaire and 74 (56.9%) completed replies were received. RESULTS: Optometrists estimated that an average of 14 patients per month per optometrist presented with symptoms of flashes and/or floaters. Mydriasis was utilised routinely for examination in approximately half of the patients. Mean relative confidence was 2.0 at identifying a vitreous haemorrhage and 6.5 for vitreous pigment (complete confidence = 0, complete lack of confidence = 10). Eight percent of responders were unfamiliar with the clinical sign of vitreous pigment, and 17% identifying this sign did not refer all such patients to the hospital services. CONCLUSIONS: Patients presenting to their optometrists with flashes and/or floaters make up a sizeable part of the community optometrist's workload and the management of these patients is highly variable. A large proportion of these patients are examined without mydriasis, even in the presence of various risk factors for retinal detachment. There is a relative lack of confidence amongst optometrists with regards the detection of vitreous pigment and the prognostic implications of this finding. Educational measures such as study days may help the level of understanding and heighten the appreciation of the implications of flashes and floaters and the various clinical signs encountered.

Clinical Competence↗

PubMed2002

The use of surgical facemasks during cataract surgery: is it necessary?

AIM: To assess whether facemask utilisation by the surgeon during cataract surgery has any effect on the bacterial load falling onto the operative site. METHOD: Prospective randomised masked study. Consent was obtained from 221 patients. Cases were randomised to wearing a new mask or not wearing any mask throughout the procedure. Blood agar settle plates were placed adjacent to the patient's head in the operative field. Duration of procedure was noted. Plates were incubated and read at 48 hours. Colony forming bacteria were counted and identified. RESULTS: There were significantly fewer organisms cultured when the surgeon used a facemask (p=0.0006). The majority of organisms were Staphylococcus epidermidis, Bacillus spp, and Diphtheroid spp; however Staphylococcus aureus and Pseudomonas aeruginosa were cultured on several occasions. There were no cases of infective complication. CONCLUSIONS: The main purpose of an operating mask is to prevent bacteria falling on to the operative site from the surgeon's oropharynx or nasopharynx with the concomitant theoretical risk of infective complication. Operating masks were shown to have a significant effect on the volume of bacterial organisms falling to the operative site; however, whether this is clinically significant is unknown.

Bacterial Infections↗

PubMed2002

Polyclonal nature of diffuse proliferation of interstitial cells of Cajal in patients with familial and multiple gastrointestinal stromal tumours.

BACKGROUND: Diffuse proliferation of interstitial cells of Cajal (ICCs) in the myenteric plexus layer of the intestine has been described in patients with familial and multiple gastrointestinal stromal tumours (GISTs). However, it is not fully understood whether proliferation is polyclonal or monoclonal. AIMS: To evaluate the clonal nature of diffuse ICC proliferation in familial and multiple GIST cases, we carried out clonal analysis using inactivation at the human androgen receptor (HUMARA) locus. MATERIALS AND METHODS: Diffuse ICC proliferation tissues from three female patients were microdissected using a laser capture microdissection (LCM) system. Normal intestinal mucosal tissues were also microdissected for polyclonal controls and GIST tissues for monoclonal controls from the same patients, and genomic DNA was extracted. After digestion by restriction enzyme HhaI, the HUMARA locus was amplified by a fluorescent polymerase chain reaction (PCR) procedure and the PCR products were analysed. RESULTS: One case was uninformative because it was homozygous at the HUMARA locus. In the two other cases, PCR products from the diffuse ICC proliferation showed two alleles as well as those from normal intestinal mucosal tissues, indicating that ICC proliferation was polyclonal. In contrast, PCR products from associated GIST tissues showed only one allele, indicating that GISTs were monoclonal. CONCLUSION: The results suggested that diffuse ICC proliferation in familial and multiple GIST cases was non-neoplastic hyperplasia.

Cell Division↗

PubMed2002

Most X;autosome translocations associated with premature ovarian failure do not interrupt X-linked genes.

Balanced translocations with breakpoints in a critical region of the X chromosome, Xq13-->q26, are associated with premature ovarian failure (POF). Translocations may cause POF either by affecting expression of specific X-linked genes essential for maintenance of normal ovarian function or by a chromosomal effect such as inhibition of meiotic pairing or altered X inactivation. We previously mapped seven Xq translocation breakpoints associated with POF to approximately 75-kb intervals. One translocation disrupted an aminopeptidase gene, XPNPEP2. We have now refined the map location of the remaining six breakpoints with respect to known genes and transcription units predicted from the draft human genome sequence. Only one of the six breakpoints disrupts a gene, DACH2, the human ortholog of a mouse gene expressed in embryonic nervous tissue, sensory organs, and limbs. DACH2 has no obvious relationship to ovarian function. The other five breakpoints fall in apparently intragenic regions. Our results are most consistent with models for POF associated with X;autosome translocations that involve generalized chromosome effects.

Amino Acid Sequence↗

PubMed2002

Effect of low or high dietary calcium on the morphology of the rat femur.

The present study compared the effect of a calcium deficit or surfeit on femurs. Young female rats were fed with the normal (1.18%), low (0.05%), or high (2.00%) calcium diet for 3, 7, 15 or 30 days. Two groups received the low calcium diet for the first 15 days and then were followed by the normal (L-N) or high calcium diets (L-H) for the sequential 15 days. The morphology of the femur was studied together with serum calcium, parathyroid hormone (PTH), calcitonin and bone mineral density (BMD). We did not find any significant changes in the serum PTH level and bone morphology in the high calcium group. In the low calcium group, the serum PTH level increased, BMD of the whole body, the femoral weight and the femoral trabecular bone decreased as compared with the normal calcium group. There was a greater proportion of resorbing surface, less resting surface and larger vascular canal openings in the femoral endosteal surfaces in the low calcium group. In the L-N or L-H group, the femoral trabecular bone increased and the femoral resorbing surface decreased as compared with those of the low calcium group. These findings suggest that high calcium intakes do not affect the bone mass, and low calcium intakes have a deleterious effect on bone status, which may be related to vascular alternations of the bone. Reversing the low income calcium intake by a higher calcium diet can partially improve the bone alternations induced by low calcium intake.

Animals↗

PubMed2002

Effects of cigarette smoke exposure on the ultrastructure of the golden hamster parathyroid gland.

Cigarette smoking has been identified as one of the risk factors to induce osteoporosis. However, we find no study on the morphology of the parathyroid gland under smoking exposure. We studied the ultrastructure of the parathyroid gland, lung and femur of the golden hamster exposed to cigarette smoke. Four-week-old male hamsters were housed in a plastic case (48x31x30 cm) and were exposed to cigarette smoke for 12 weeks, 5 minutes exposure, 4 times a day, 4 days a week. There were no differences in serum calcium level and the whole bone mineral density between the control and the smoke-exposed groups. In the parathyroid gland of the smoke-exposed animals, the Golgi complexes associated with many prosecretory granules were well developed and many secretory granules were located near the plasma membrane. Large lipid-like inclusion bodies were observed in the alveolar macrophages of the smoke-exposed animals. The femur morphology showed a wider area of resorbing surface in the smoke-exposed group than in the control group. From these findings, it is conceivable that the secretory activity of the parathyroid gland was stimulated with cigarette smoke exposure.

Animals↗

PubMed2002

Protection of sperm DNA against oxidative stress in vivo by accessory sex gland secretions in male hamsters.

Reactive oxygen species scavengers present in male accessory sex gland secretions might afford antioxidant protection to sperm DNA. This study was conducted to determine whether accessory sex gland secretions protect the genome and function of spermatozoa against oxidative damage in the uterus. Male golden hamsters were divided into four experimental groups: (i) all accessory sex glands removed; (ii) ampullary glands removed; (iii) ventral prostate gland removed and (iv) sham-operated controls. Ejaculated spermatozoa recovered from uteri 15-30 min after mating with experimental males and caput and cauda epididymal spermatozoa obtained from intact males were incubated in 0-20 mmol NADPH l(-1) for 2 h. These spermatozoa and untreated uterine spermatozoa were processed for two types of comet assay (single cell gel electrophoresis): alkaline comet assay (pH > 13) which revealed single-strand DNA breakage and neutral comet assay (pH 9) which revealed double-strand DNA breakage. In comparison with the sham-operated controls, spermatozoa that had not been exposed to accessory sex gland secretions had a higher incidence and more extensive single-strand DNA damage with increasing concentrations of NADPH. Spermatozoa from hamsters without ampullary glands and from hamsters without the ventral prostate glands were similar to those of the control group. After incubation with NADPH, the capacity of spermatozoa from hamsters without accessory glands and from sham-operated controls to fuse with oocytes in vitro was reduced. However, only hamsters without accessory glands showed a negative correlation between single-strand DNA damage and sperm-oocyte fusion. Cauda epididymal spermatozoa were less susceptible to NADPH treatment compared with caput epididymal spermatozoa. The results of the present study showed that male accessory sex gland secretions can preserve the integrity of the sperm genome.

Animals↗

PubMed2002

Characterisation of reconstituted equine cartilage formed in vitro.

Lesions in cartilage of equine weightbearing joints commonly result in lameness. Cell-based resurfacing techniques are currently being developed for human and veterinary applications. Biopsies of stifle joint cartilage (1 g) were harvested aseptically and chondrocytes were isolated by sequential enzyme digestion. The cells were grown in vitro on filter inserts. Analysis of cultures 8 weeks later showed that the cells had accumulated extracellular matrix and formed a continuous layer of cartilagenous tissue as determined histologically. The cells maintained their phenotype as they synthesised type II collagen and proteoglycans similar in size to those synthesised by chondrocytes in native cartilage, but this reconstituted tissue had more sulphated glycosaminoglycan and lower collagen content than native cartilage. This experiment tests the feasibility of growing equine cartilagenous tissue in vitro. This tissue may be useful in the management of chondral injuries in the horse in a scenario where the patient donates cells, the cells are propagated under laboratory conditions and the resulting tissue becomes the therapeutic agent.

Animals↗