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Biomedical subjects

J Q Chen

Publications and source records attributed to J Q Chen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Historical total and respirable silica dust exposure levels in mines and pottery factories in China.

Historical exposure estimates of total dust and respirable silica were made in a recent nested case-referent study of lung cancer among mine and pottery workers in China. Exposure to total dust and respirable silica was assessed in 20 mines and 9 pottery factories. The average total dust concentration was 7.26 mg center dot m-3, with a range from 17.68 mg center dot m-3 in the 1950s to 3.85 mg center dot m-3 in the 1980s, while the average respirable silica dust was 1.22 mg center dot m-3, with a range from 3.89 mg center dot m-3 in the 1950s to 0.43 mg center dot m-3 in the 1980s. The highest respirable silica dust occurred in the underground mining operations (1.43 mg center dot m-3), particularly for manual drillers (9.03 mg center dot m-3). Among all facility types, tungsten mines had the highest respirable silica dust exposure (1.75 mg center dot m-3), while the lowest exposure occurred in copper-iron mines (0.32 mg center dot m-3).

Ceramics↗
PubMed1994

Indirect validation of a retrospective method of exposure assessment used in a nested case-control study of lung cancer and silica exposure.

Validations of retrospective methods of assessment used in occupational epidemiological studies have rarely been published. This study is an indirect validation of a quantitative retrospective assessment of exposure to silica used in a nested case-control study of lung cancer among workers at 29 metal mines and pottery factories in China. Indices of cumulative total dust and cumulative respirable dust were calculated by merging work histories with the historical exposure profile for each subject. To validate indirectly the methods of exposure assessment used in the study of lung cancer, trends for exposure response relation between the two indices of exposure to silica and risk of silicosis were evaluated with 376 patients with silicosis from the study population as the cases, and 1262 controls without silicosis for comparison. Age adjusted odds ratios (ORs) as a measure of risk of silicosis showed striking trends with both indices of exposure to silica. For cumulative respirable dust, the OR (95% confidence interval) rose from 7.6 (5.1-11.4) for low exposure to 20.0 (13.2-30.6) for medium exposure, and to 51.7 (31.0-86.8) for high exposure. The strength of the association between exposure to silica and risk of silicosis suggests that the retrospective assessment of exposure used in the case-control study of lung cancer would accurately reflect an exposure response relation between silica and lung cancer, if it existed.

Case-Control Studies↗
PubMed1994

Effects of Panax notoginseng saponins on myocardial adenosinetriphosphatase.

Effects of total Panax notoginseng saponins (PNS) and Panax notoginseng saponin monomers Rb1 and Rg1 (Rb1, Rg1) on total ATPase and Na(+)-K(+)-exchanging ATPase of guinea pig heart were studied. It was found that PNS inhibited the total myocardial ATPase, but had no significant effect on the myocardial Na(+)-K(+)-exchanging ATPase. The total ATPase was inhibited by Rg1, and more clearly by Rb1. The automaticity and contractility of isolated guinea pig atria were inhibited by Rb1. Rg1 decreased the spontaneous frequency of isolated guinea pig right atrium, but not markedly the contractility of the left atrium. These results demonstrate that Rb1 is the main ingredient in PNS.

Adenosine Triphosphatases↗
PubMed1994

[Homoplastic keratomileusis for aphakic eyes with corneal leucoma].

We performed homoplastic keratomileusis on 6 aphakic eyes with central corneal leucoma. The results showed that the post-operative corrected visual acuities were markedly increased to 0.3-0.5 in 3 cases and to 0.1-0.2 in another 3 cases. Since such patients were neither indicated to undergo intraocular lens implantation or penetrating keratoplasty for various reasons nor indicated for epikeratoplasty, homoplastic keratomileusis can be chosen for them.

Adult↗
PubMed1994

[Effects of different lymph node clearances on long-term survival in patients with gastric carcinoma].

From 1980 to 1987, radical gastrectomy plus R2 or R3 lymph node clearance was performed in 309 cases of gastric carcinoma of which 179 were with R2 and 130 with R3. The 1, 3, 5 years survival rate of R3 was statistically higher than that of R2. The 5 years survival rate of R2 was nearly the same as R3 in patients at stage I (I a, I b) and borrmann type I and II, While R3 yields better results than R2 at stage II and III a, it was even 25.5% higher by R3 than by R2 at II b and IV. R3 still benefits patients at stage II with serosa infiltration, R3 should also be performed in advanced cases with poorly biologic behavior, such as diffuse growth pattern; undifferentiated cancer and lymphatic cancerous embosis. The recovery time, complications and mortalities of patients with R2 or R3 were mainly related to the model of gastrectomy not to the extent of lymph node clearance.

Adult↗
PubMed1994

[Corneal topography of keratoconus].

A computerized video keratoscope (TMS-1) was used to determine the topographic findings of 6 eyes of 4 patients with keratoconus and they were compared with those of 18 normal eyes. The results show that in keratoconus the central corneal refractive power is greater, the difference between the refractive powers of the bilateral central corneas of a case is larger and the inferior cornea is steeper than the superior cornea. The above topographic findings are possibly the characteristics of the corneal topography of keratoconus.

Adolescent↗
PubMed1994

[An immunohistochemical study of cornea and adjacent bulbar conjunctiva in Mooren's ulcer].

The specimens of the corneal lesions and their adjacent bulbar conjunctivas taken from 14 cases with Mooren's ulcers were studied by immunohistochemical techniques to investigate the expression of HLA-DR antigen and the subgroups of lymphocytes. It is discovered that there is an aberrant expression of HLA-DR antigen in a large amount of keratoconjunctival epithelial cells and stromal keratocytes and simultaneously, the CD4/CD8 ratio is significantly higher than that of the normal control group. The results suggest that the aberrant expression of MHC-II antigen in the resident cells at the peripheral cornea and its adjacent conjunctiva and a raised local TH/TS ratio leading to an excessive autoimmune reactivity be possibly the direct cause of the pathogenesis of the Mooren's ulcer.

Adult↗
PubMed1994

[Factors of graft failure after chemical corneal injury].

83 cases (97 eyes) of keratoplasty after chemical corneal injury were followed up for a mean 14 months with the results that 21 (21.6%) grafts were transparent and 76 (78.4%) opaque or semitransparent. The success rate depended on the severity of the chemical injury; it was 87.5% for type A corneal scarring and 15.7% for type B. The causes of graft failure were postoperative epithelial erosion (70.7%) and corneal rejection (28.0%). Most patients with epithelial erosion had problems of insufficient tear secretion and tear-film defects. The prevention and management of graft failure were discussed.

Adolescent↗
PubMed1994

[Vitrectomy under temporary keratoprosthesis].

In vitreoretinal disorders complicated by corneal opacity, a temporary keratoprosthesis device is placed into a trephined opening in the cornea to provide a clear stable view which permits the performance of pars plana vitrectomy and immediately following the vitrectomy, the keratoprosthesis is replaced by a corneal graft. Using this technique, we have saved blind eyes with corneal and vitreoretinal disorders in one surgical procedure, being a new approach for rehabilitation of eye sight. Since 1990, the operation has been performed on 10 patients of whom 9 obtained satisfactory results. They were the patients who had been impossible to be saved by other methods and had been abandoned. The patient with the best result had been followed for 15 months and his visual acuity achieved and maintained 0.3. In six cases, the operation was combined with multiple procedures in the vitreous, such as gas fluid exchange, internal drainage of subretinal fluid, injection of silicone oil, etc. to facilitate the reattachment of the complicated retinal detachment.

Cornea↗
PubMed1994

[Experimental pharmacokinetic studies of carboplatin intraperitoneal chemotherapy].

High performance liquid chromatography was used to study the performances of carboplatin by intraperitoneal (ip) administration in six dogs. 30 mg/kg carboplatin in 500ml 0.9% sodium chloride was injected ip quickly. Drug levels in the peritoneal fluid and blood of the portal vein and femoral vein were measured at different time intervals. The results showed a high drug concentration in the peritoneal fluid within 240 minutes after large dose and volume of carboplatin administered ip. The peak and mean concentrations of carboplatin in the peritoneal fluid were 139 and 64 times that of blood in the femoral vein, respectively. The peak and mean concentrations of the drug in the portal vein were 13.3 and 6.8 times those in the femoral vein. Intraperitoneal chemotherapy of carboplatin can maintain a stable and persistent high drug level in the peritoneal cavity, portal vein as well as liver. Systemic toxic effects were decreased due to low level of drug in the systemic circulation. These pharmacokinetic properties of carboplatin are of advantage in preventing and treating tumor recurrence in the peritoneal cavity and hepatic metastases.

Animals↗
PubMed1994

[Penetrating keratoplasty in the treatment of corneal perforation].

166 patients of corneal perforation from HSK, suppurative corneal ulcer and chemical or thermal burn were treated by penetrating keratoplasty. In the group of HSK, 69.8% of the grafts remained transparent and vision was restored to 0.05-1.0 in 81 cases (69.8); in the group of suppurative corneal ulcer, 40% of the grafts were transparent and vision was restored to 0.05 or better in 15 cases (37.5%); while in the group of burns, the grafts were clear only in 20% and vision was 0.05-0.6 in 3 cases (30%). The complications and causes for failure were similar to those in patients without perforation. These results indicate that timely penetrating keratoplasty is recommendable for the treatment of corneal perforations of various etiology.

Adolescent↗
PubMed1993

Estimating historical exposure to silica among mine and pottery workers in the People's Republic of China.

A quantitative retrospective exposure assessment method was developed for use in a nested case-control study of lung cancer among mine and pottery workers exposed to silica dust in the People's Republic of China. Exposure assessment was carried out in 20 mines (10 tungsten, 6 iron/copper, and 4 tin) and nine pottery factories. A job title dictionary was developed and used in both the collection of historical exposure information and work histories of 1,668 (316 cases and 1,352 controls) study subjects. Several data abstraction forms were developed to collect historical and current exposure information and employees' work histories, starting in 1950. A retrospective exposure matrix was developed on the basis of facility/job title/calendar year combinations using available historical exposure information and current exposure profiles. Information on the amount of respirable, thoracic, and free silica content in total dust was used in estimating exposure to silica. Starting in 1950, 6,805 historical estimates had been carried out for 14 calendar-year periods. We estimated the average total dust concentration to be 9 mg/M3, with a range from 28 mg/M3 in earlier years to 3 mg/M3 in recent years. Several exposure indices [such as cumulative dust, average dust, cumulative respirable (< 5 mu in particle size) and thoracic (< 10 mu in particle size) silica dust, average respirable and thoracic silica dust, exposure-weighted duration, and the highest/longest exposure] were calculated for individuals by merging work history and historical exposure matrix for each study subject. We developed these various measures of exposure to allow investigators to compare and contrast different indices of historical exposure to silica.

Case-Control Studies↗
PubMed1993

[Refractive evaluation of donor corneas from the newborn in aphakic penetrating keratoplasty].

Donor corneas from newborns aged 1-28 days were used in 30 cases of aphakic penetrating keratoplasty with good refractive results. After an average postoperative follow-up of 14.8 months, the mean visual acuity was 0.3 s.c. and 0.6 c.c; the mean keratometric corneal refraction was +53.04 DS (about 10.00 DS higher than that of the contralateral eye), and the mean corneal astigmatism was 2.84 DC. The postoperative specular corneal endothelial count averaged 3,324 cells/mm2 in 14 eyes.

Adolescent↗
PubMed1992

Biochemical and immunological properties of alkaline invertase isolated from sprouting soybean hypocotyls.

Alkaline invertase from sprouting soybean (Glycine max) hypocotyls was purified to apparent electrophoretic homogeneity by consecutive use of DEAE-cellulose, green 19 dye, and Cibacron blue 3GA dye affinity chromatography. This protocol produced about a 100-fold purification with about a 11% yield. The purified protein had a specific activity of 48 mumol of glucose produced mg-1 protein min-1 (pH 7.0) and showed a single protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) (58 kDa) and in native PAGE, as indicated by both protein and activity staining. The native enzyme molecular mass was about 240 kDa, suggesting a homotetrameric structure. The purified enzyme exhibited hyperbolic saturation kinetics with a Km (sucrose) near 10 mM and the enzyme did not utilize raffinose, maltose, lactose, or cellibose as a substrate. Impure alkaline invertase preparations, which contained acid invertase activity, on contrast, showed biphasic curves versus sucrose concentration. Combining equal activities of purified alkaline invertase with acid invertase resulted in a biphasic response, but there was a transition to hyperbolic saturation kinetics when the activity ratio, alkaline: acid invertase, was increased above unity. Alkaline invertase activity was inhibited by HgCl2, pridoxal phosphate, and Tris with respective Ki values near 2 microM, 5 microM, and 4 mM. Glycoprotein staining (periodic acid-Schiff method) was negative and alkaline invertase did not bind to two immobilized lectins, concanavalin A and wheat germ agglutinin; hence, the enzyme apparently is not a glycoprotein. The purified alkaline invertase, and a purified soybean acid invertase, was used to raise rabbit polyclonal antibodies. The alkaline invertase antibody preparation was specific for alkaline invertase and cross-reacted with alkaline invertases from other plants. Neither purified soybean alkaline invertases nor the crude enzyme from several plants cross-reacted with the soybean acid invertase antibody.

Antibody Formation↗
PubMed1992

Influence of opioids on substance P release evoked by antidromic stimulation of primary afferent fibers in the hind instep of rats.

The effect of opioids on the release of immunoreactive substance P (iSP) following simultaneous electrical stimulation of the sectioned sciatic and saphenous nerves was examined by perfusion of the subcutaneous space in the rat instep. Antidromic stimulation of both the nerves caused an increase in iSP release, which was dependent on the intensity of stimulation, and an approx. 200% increase in Evans blue extravasation. Stimulation-induced iSP release and extravasation were suppressed by pretreatment with capsaicin (50 mg/kg s.c.) and spantide (10 mumol/kg i.p.), respectively. Intra-arterial infusion of morphine (30 mumol/kg) or ethylketocyclazocine (30 mumol/kg) or [D-Ala2,D-Leu5]enkephalin (30 mumol/kg) inhibited the increase in iSP release evoked by antidromic stimulation at 10 V. This inhibitory effect of morphine was antagonized by pretreatment with naloxone (2 mg/kg, i.p.). These results suggest existence of multiple types of opioid receptor on the peripheral endings of primary afferent fibers, that regulate SP release from the peripheral nerve endings into the extravascular space.

Afferent Pathways↗
PubMed1992

A comparison of radiographic interpretation of silica exposed workers using the 1963 and the 1986 Chinese roentgenodiagnostic criteria of pneumoconioses.

As part of a larger study relating to silica exposure, silicosis, and lung cancer mortality in Chinese mine and factory workers, 1936 old posterior-anterior chest X-rays were re-interpreted according to the 1986 Chinese Roentgenodiagnostic Criteria of pneumoconioses. Each film was independently read by three individuals from a panel of eleven radiologists, and this reading was compared to the original one. Subsequent to the independent readings, a groups of three readers interpreted the films together, called the consensus readings. Comparisons were made by Chinese stage of pneumoconiosis. For the entire cohort, there was a crude agreement of 57.4% between the old and the new interpretations. Agreement within one step of full agreement was 92.5%. The interpretations done by median reading and by consensus were very similar. In general, there was a tendency for the old readings to be slightly higher compared to the new interpretations. This tendency was most marked in the tin mines, followed in decreasing order by the iron/copper mines, the potteries, and the tungsten mines. The agreement between the old and new interpretations is felt to be satisfactory.

Humans↗
PubMed1992

Involvement of substance P present in primary afferent neurones in modulation of cutaneous blood flow in the instep of rat hind paw.

1. The participation of small-diameter afferent fibres in the microcirculatory haemodynamics of cutaneous tissue was examined by studies on the effects of antidromic stimulation of primary afferent neurones on cutaneous blood flow (CBF) and tachykinin release into the subcutaneous space in the instep of the hind paw of rats. 2. Antidromic stimulation of the sectioned sciatic nerve induced a biphasic flow response, an initial transient decrease followed by an increase, with no alteration in the blood pressure. 3. Neither phase was affected by pretreatment with phentolamine (0.1 mg kg-1, i.a.), propranolol (0.5 mg kg-1, i.a.), atropine (0.5 mg kg-1, i.a.), methysergide (0.5 mg kg-1, i.a.) or mepyramine (10 mg kg-1, i.a.) plus cimetidine (10 mg kg-1, i.a.), but both were significantly inhibited by pretreatment with capsaicin (50 mg kg-1, s.c.). 4. Spantide (1-2 mumol kg-1, i.a.), a substance P (SP) antagonist, reduced the basal CBF, and also inhibited both phases of the biphasic flow response evoked by antidromic stimulation of the sectioned sciatic nerve. 5. Intra-arterial infusion of SP (0.5 mumol kg-1, i.a.) induced a biphasic flow response similar to that elicited by antidromic stimulation of the sectioned sciatic nerve. 6. Antidromic stimulation of the sectioned sciatic nerve caused a marked increase in SP release into the subcutaneous perfusate of the instep of the rat hind paw, but no detectable increase in neurokinin A release.7. We suggest that SP and its receptors are mainly responsible for the vascular response induced by stimulation of the sectioned sciatic nerve, and that small-diameter afferent fibres containing SP tonically regulate vascular tone in cutaneous microvessels.

Animals↗