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Biomedical subjects

J Lin

Publications and source records attributed to J Lin.

At least 307 records · Page 17Linked to original sources
PubMed1999

A pacemaker working status telemonitoring algorithm.

To extend the application of a previously developed home ECG and blood pressure telemonitoring system for pacemaker users, a specially designed pacemaker working status analysis algorithm is developed in this paper. This paper includes four sections. First, a pacing beat and spontaneous beat recognition algorithm are established in which a FIR filter and three threshold methods are used to pick up the pacing spikes and a dynamic threshold modification method is proposed for error elimination. Second, a beat classification algorithm is developed based on decision rules for six commonly used pacemaker types. Third, a pacemaker malfunction recognition algorithm is established to evaluate the pacemaker working status. Fourth, the statistics of the analysis and the report are also provided. To validate the algorithm, clinical data were collected and manually classified by specialists. Then, the classification and recognition results were obtained with the clinical data. Results show that the algorithm can achieve a recognition rate of 98.4%. Results also indicate that the algorithm is capable of working in real-time speed. The algorithm has been incorporated into the telemonitoring system, and trial application cases are also reported.

Algorithms↗
PubMed1999

Fractal analysis of radiographs: assessment of trabecular bone structure and prediction of elastic modulus and strength.

The purpose of this study was to determine whether fractal dimension of radiographs provide measures of trabecular bone structure which correlate with bone mineral density (BMD) and bone biomechanics, and whether these relationships depend on the technique used to calculate the fractal dimension. Eighty seven cubic specimen of human trabecular bone were obtained from the vertebrae and femur. The cubes were radiographed along all three orientations--superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP), digitized, corrected for background variations, and fractal based techniques were applied to quantify trabecular structure. Three different techniques namely, semivariance, surface area, and power spectral methods were used. The specimens were tested in compression along three orientations and the Young's modulus (YM) was determined. Compressive strength was measured along the SI direction. Quantitative computed tomography was used to measure trabecular BMD. High-resolution magnetic-resonance images were used to obtain three-dimensional measures of trabecular architecture such as the apparent bone volume fraction, trabecular thickness, spacing, and number. The measures of trabecular structure computed in the different directions showed significant differences (p<0.05). The correlation between BMD, YM, strength, and the fractal dimension were direction and technique dependent. The trends of variation of the fractal dimension with BMD and biomechanical properties also depended on the technique and the range of resolutions over which the data was analyzed. The fractal dimension showed varying trends with bone mineral density changes, and these trends also depended on the range of frequencies over which the fractal dimension was measured. For example, using the power spectral method the fractal dimension increased with BMD when computed over a lower range of spatial frequencies and decreased for higher ranges. However, for the surface area technique the fractal dimension increased with increasing BMD. Fractal measures showed better correlation with trabecular spacing and number, compared to trabecular thickness. In a multivariate regression model inclusion of some of the fractal measures in addition to BMD improved the prediction of strength and elastic modulus. Thus, fractal based texture analysis of radiographs are technique dependent, but may be used to quantify trabecular structure and have a potentially valuable impact in the study of osteoporosis.

Biomechanical Phenomena↗
PubMed1999

Antigenic homology of the inducible ferric citrate receptor (FecA) of coliform bacteria isolated from herds with naturally occurring bovine intramammary infections.

Expression of ferric citrate receptor FecA by Escherichia coli and Klebsiella pneumoniae isolated from bovine mastitis was investigated. Transformant E. coli UT5600/pSV66, which produces large quantities of FecA in the presence of citrate, was constructed. The FecA of E. coli UT5600/pSV66 was purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and used to prepare polyclonal antiserum in rabbits. All coliform isolates of E. coli (n = 18) and K. pneumoniae (n = 17) from naturally occurring bovine intramammary infections in five herds induced iron-regulated outer membrane proteins when grown in Trypticase soy broth containing 200 microM alpha-alpha'-dipyridyl and 1 mM citrate. Polyclonal antiserum against FecA was used in conjunction with an immunoblot technique to determine the degree of antigenic homology of FecA among isolates. In the presence of citrate, each isolate expressed FecA that reacted with the anti-FecA polyclonal antiserum. The molecular mass of FecA ( approximately 80.5 kDa) was also highly conserved among isolates. Therefore, the ferric citrate iron transport may be induced in coliform bacteria and utilized to acquire iron in milk for survival and growth. The FecA is an attractive vaccine component for controlling coliform mastitis during the lactation period.

Animals↗
PubMed1999

Expression of intestinal trefoil factor in developing rat intestine.

Intestinal trefoil factor (ITF or TFF3), a small peptide secreted at the mucosal surface by goblet cells throughout the mature intestine, appears to play important roles in the maintenance and repair of the intestinal mucosal barrier. To study the expression of TFF3 during development, intestinal tissues were collected from rats at different development stages and examined by Northern blot analysis, Western blot analysis and immunohistochemical staining for TFF3 mRNA and protein expression. The results demonstrate that rat TFF3 mRNA is not detected until the 17th gestational day (term = 22 days), the expression is greater on gestational day 20 and increased further postnatally. TFF3 protein is first detected by Western blotting and immunohistochemical staining on gestational day 20. Further increases in TFF3 protein expression are demonstrated at around the weaning period. In conclusion, significant expression of rat TFF3 commences late in gestation and its expression is relatively deficient in immature rats. Expression of TFF3 may be deficient in premature infants and, therefore, may have a role in the development of necrotizing enterocolitis.

Animals↗
PubMed1999

Hemodialysis-related nodulocystic acne treated with isotretinoin.

Some hemodialysis patients, without taking any acnegenic agents, developed severe nodulocystic acne with unknown causes. Because nodulocystic acne poorly responds to conventional acne therapy and increases the black pigmentation in the face, it severely interferes with the quality of life of these patients. To investigate whether isotretinoin is effective in treating hemodialysis patients with severe nodulocystic acne, we undertook a prospective, randomized, single-blind study. A total of 20 patients with nodulocystic acne participated in the study, of whom 18 completed it. Ten patients received isotretinoin 10 mg/day (5 mg/capsule) for 3 months as a study group and the other 10 took placebo for 3 months as a control group. The severity of acne and treatment-related side effects were evaluated monthly by a questionnaire and laboratory evaluation which included liver function tests, blood lipids and blood platelet counts. The results showed isotretinoin treatment significantly reduced the severity of acne of the study group patients after 1 month (scales of acne severity: 4.0 +/- 0.0 vs. 3.13 +/- 0.35, p < 0. 01) and 3 months (4.0 +/- 0.0 vs. 1.5 +/- 0.76, p < 0.01) of follow-up. In addition, the severity of acne of the study group patients was significantly less than that of the control group patients after 1 month (3.13 +/- 0.35 vs. 3.80 +/- 0.42, p < 0.01) and 3 months (1.5 +/- 0.76 vs. 3.70 +/- 0.48, p < 0.001) of treatment. Only mild side effects were noted. No significant changes of biochemical evaluation were found except that a mild elevation of aspartate aminotransferase was noted in the study group patients. However, two study group patients withdrew from the trial because of isotretinoin-related side effects and toxic hepatitis. In summary, our study first demonstrated that the small dose of isotretinoin effectively treated nodulocystic acne of hemodialysis patients and the side effects were mild. This result suggests that isotretinoin may be the treatment of choice for nodulocystic acne in end-stage renal disease patients with renal replacement therapy. The liver function and other isotretinoin-related side effects in these patients should be carefully monitored.

Acne Vulgaris↗
PubMed1999

Myocardial injury and left ventricular performance after subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Electrocardiographic abnormalities and elevations of the creatine kinase myocardial isoenzyme (CK-MB) occur frequently after subarachnoid hemorrhage. In some patients, a reversible and presumably neurogenic form of left ventricular dysfunction is demonstrated by echocardiography. It is not known whether cardiac injury of this type adversely affects cardiovascular hemodynamic performance. METHODS: We retrospectively studied 72 patients admitted to our neuro-ICU for aneurysmal subarachnoid hemorrhage over a 2.5-year period. We selected patients who met the following criteria: (1) CK-MB levels measured within 3 days of onset, (2) pulmonary artery catheter placed, (3) echocardiogram performed, and (4) no history of preexisting cardiac disease. Hemodynamic profiles were recorded on the day after surgery (n=67) or on the day of echocardiography (n=5) if surgery was not performed (mean, 3. 3+/-1.7 days after onset). The severity of cardiac injury was classified as none (peak CK-MB <1%, n=36), mild (peak CK-MB 1% to 2%, n=21), moderate (peak CK-MB >2%, n=6), or severe (abnormal left ventricular wall motion, n=9). RESULTS: Abnormal left ventricular wall motion occurred exclusively in patients with peak CK-MB levels >2% (P<0.0001), poor neurological grade (P=0.002), and female sex (P=0.02). Left ventricular stroke volume index and stroke work index were elevated above the normal range in patients with peak CK-MB levels <1% and fell progressively as the severity of cardiac injury increased, with mean values for patients with abnormal wall motion below normal (both P<0.0001 by ANOVA). Cardiac index followed a similar trend, but the effect was less pronounced (P<0.0001). Using forward stepwise multiple logistic regression, we found that thick subarachnoid clot on the admission CT scan (odds ratio, 1.9; 95% confidence interval [95% CI], 1.0 to 3.4; P=0.04) and depressed cardiac index (odds ratio, 2.1; 95% CI, 1.0 to 4.1; P=0.04) were independent predictors of symptomatic vasospasm. CONCLUSIONS: Myocardial enzyme release and echocardiographic wall motion abnormalities are associated with impaired left ventricular performance after subarachnoid hemorrhage. In severely affected patients, reduction of cardiac output from normally elevated levels may increase the risk of cerebral ischemia related to vasospasm.

Acute Disease↗
PubMed1999

Mucin gene expression in the rat middle ear: an improved method for RNA harvest.

Mucins are heavily glycosylated proteins characterized by high molecular weight and heterogeneous structure. Mucin genes are expressed in a tissue- or epithelium-specific manner. Although mucins are known to be important structural components of the mucociliary transport system that protects epithelium against invading microorganisms, very little is known about mucin gene expression unique to the middle ear. This study demonstrated that middle ear messenger RNA specifically hybridized with rat MUC2 and human MUC2 (SMUC-41) complementary DNA probes. MUC3 and MUC5AC mucin genes, dominantly expressed in rodent intestine and trachea, were not detected in the rat middle ears in this study. The middle ear MUC2 messenger RNA harvested by lavage was characterized by a single transcript--unlike its counterpart in intestine and airways, which is characterized by polydispersity--suggestive of a better method for RNA analysis. It was concluded that rat middle ears possess a MUC2 mucin gene or homologue of human MUC2 (SMUC-41).

Animals↗
PubMed1999

Molecular mechanisms of photoaging in human skin in vivo and their prevention by all-trans retinoic acid.

Solar UV radiation damages human skin, affecting skin tone and resiliency and leading to premature aging (photoaging), the symptoms of which include leathery texture, wrinkles, mottled pigmentation, laxity and sallowness. We propose that photoaging results largely from UV induction of matrix metalloproteinases (MMP) that degrade skin collagen. We find that pretreatment of human skin with all-trans retinoic acid (tRA) inhibits UV induction of MMP, suggesting that tRA can protect against UV-induced collagen destruction and may therefore be able to lessen the effects of photoaging. The tRA prevents UV-induced accumulation of c-Jun protein, which is required for MMP gene expression. Activation of c-Jun transcriptional activity requires N-terminal phosphorylation. The majority of c-Jun in human skin in vivo is N-terminal phosphorylated. Topically applied tRA does not inhibit N-terminal phosphorylation by UV-induced c-Jun kinase activity in human skin. The tRA likely acts to reduce UV induction of c-Jun protein by stimulating its breakdown through the ubiquitin-proteasome pathway.

Adult↗
PubMed1999

Growth responses of coliform bacteria to purified immunoglobulin G from cows immunized with ferric enterobactin receptor FepA.

The ability of purified bovine immunoglobulin (Ig) G from cows immunized with ferric enterobactin receptor FepA to inhibit the growth of coliform bacteria derived from bovine intramammary infection was investigated in iron-restricted media. All isolates of Escherichia coli (n = 21) and Klebsiella pneumoniae (n = 21) were tested for growth in a chemically defined medium containing 0.5 mg/ml of apolactoferrin and in a pooled source of dry cow secretion. The addition of 4 mg/ml of purified bovine IgG directed against FepA in the synthetic medium resulted in significant growth inhibition for both E. coli and K. pneumoniae isolates. Growth reduction of E. coli was greater than that of K. pneumoniae. In dry cow secretions, the growth of each E. coli isolate but of less than half of K. pneumoniae isolates (43%) was inhibited by IgG from cows immunized with FepA. Purified bovine IgG from cows immunized with E. coli J5 had a minimal inhibitory effect on the growth of both E. coli and K. pneumoniae isolates in the synthetic medium. In dry cow secretions, IgG from cows immunized with E. coli and K. pneumoniae isolates. Supplementation with 50 microM of ferric chloride to the medium completely reversed the inhibitory effects of the antibodies and lactoferrin. Bovine IgG directed against FepA apparently inhibited the growth of coliform bacteria by interfering with the binding of the ferric enterobactin complex to the cell surface receptor FepA.

Animals↗
PubMed1999

Effects of diagnostic levels of color Doppler ultrasound energy on the cell cycle of newborn rats.

Our objective was to evaluate the safety of diagnostic levels of color Doppler ultrasound energy in the field of obstetrics and to provide the experimental data for its clinical application. After insonating pregnant rats with diagnostic levels of color Doppler ultrasound energy, we studied the cell cycles of the newborn rats by flow cytometry and factorial analysis. We found that the deoxyribonucleic acid content was not affected in any phase of the cell cycle in newborn rats by any of the different insonation times and frequencies.

Animals↗
PubMed1999

Optical mapping of Plasmodium falciparum chromosome 2.

Detailed restriction maps of microbial genomes are a valuable resource in genome sequencing studies but are toilsome to construct by contig construction of maps derived from cloned DNA. Analysis of genomic DNA enables large stretches of the genome to be mapped and circumvents library construction and associated cloning artifacts. We used pulsed-field gel electrophoresis purified Plasmodium falciparum chromosome 2 DNA as the starting material for optical mapping, a system for making ordered restriction maps from ensembles of individual DNA molecules. DNA molecules were bound to derivatized glass surfaces, cleaved with NheI or BamHI, and imaged by digital fluorescence microscopy. Large pieces of the chromosome containing ordered DNA restriction fragments were mapped. Maps were assembled from 50 molecules producing an average contig depth of 15 molecules and high-resolution restriction maps covering the entire chromosome. Chromosome 2 was found to be 976 kb by optical mapping with NheI, and 946 kb with BamHI, which compares closely to the published size of 947 kb from large-scale sequencing. The maps were used to further verify assemblies from the plasmid library used for sequencing. Maps generated in silico from the sequence data were compared to the optical mapping data, and good correspondence was found. Such high-resolution restriction maps may become an indispensable resource for large-scale genome sequencing projects.

Animals↗
PubMed1999

[The relationship between polymorphism of LMP2 and LMP7 genes and the phenotype of ankylosing spondylitis].

OBJECTIVE: To evaluate the relationship of the polymorphism of LMP2 and LMP7 genes and the phenotype of patients with ankylosing spondylitis(AS). METHODS: One hundred and eighteen blood samples were collected from patients with AS and acute anterior uveitis(AAU). HLA-B(27) typing was performed and LMP2 and LMP7 amplified fragment length polymorphisms were determined after PCR and digestion with Cfo I restriction enzyme in the study. RESULTS: There was a significantly increased LMP2 BB genotype frequency in patients with AS+AAU(86.9%) and AAU(87%), compared with controls(53.3%) and AS patients(63.1%)(P<0.05); the odds ratio(OR) relating LMP2 BB and AAU was 5.83, and the OR for AS+AAU was 3.71. No difference was found between adult AS and junior AS and between AS patients with and without extraspinal arthritis. No difference was found in LMP7 genotype. CONCLUSION: The polymorphism of LMP2 gene is strongly associated with the development of AAU in AS patients and in uncomplicated AAU patients, but not with the age at onset and the type of joints affected.

Adolescent↗
PubMed1999

Purification and biochemical characteristics of beta-D-xylanase from a thermophilic fungus, Thermomyces lanuginosus-SSBP.

An extracellular xylanase was purified to homogeneity from the culture filtrate of a thermophilic fungus, Thermomyces lanuginosus-SSBP, and its biochemical characteristics were studied. A yield of 70-80% was achieved through the procedures of 80%-satd. ammonium sulphate precipitation, DEAE-Sephadex A25 and quaternary aminoethyl (QAE)-Sephadex A25 column chromatography. The molecular mass of the purified xylanase was 23.6 kDa, as analysed by SDS/PAGE, with a pI value of 3.8. The molar absorption coefficient of the absorbance at 280 nm was 6.8x10(4) M(-1).cm(-1). The specific activity, calculated using the dinitrosalicylic acid (DNS) method, was 3500 units/mg. The enzyme reactions followed Michaelis-Menten kinetics with K app m and V(max) values of 3.26 mg/ml and 6300 units/ml per mg of protein respectively, as obtained from a Lineweaver-Burk plot. The xylanase contained no other enzyme activity (cellulase, beta-glucosidase, beta-mannosidase, alpha-arabinofuranosidase, or beta-xylosidase) except for the hydrolysis of xylan substrate. The optimal temperature of the enzyme assay was 70-75 degrees C. The enzyme retained full activity after a 60 degrees C incubation for 3 h. The optimal pH of xylanase activity was 6.5 and the enzyme appeared to be stable over a broad pH range (pH 5-12) under the assay conditions. The majority of the metal ions tested had no effect on the enzyme activity, with the exception of Pb(2+) (modest inhibitor) and Hg(2+) (strong inhibitor). The results showed that one or two tryptophan residues oxidized by N-bromosuccinamide per enzyme molecule was sufficient to inhibit the enzyme activity completely, thus indicating that the tryptophan residues play an important role in the catalytical processes of the enzyme reaction. Because of the outstanding properties of the purified xylanase from the SSBP strain, this xylanase has a potential use in biopulping processes and other industrial applications.

Catalysis↗
PubMed1999

Purification and biochemical characteristics of beta-D-glucosidase from a thermophilic fungus, Thermomyces lanuginosus-SSBP.

The beta-D-glucosidase produced by Thermomyces lanuginosus-SSBP was purified to apparent homogeneity. The purified enzyme consisted of two identical subunits with a native molecular mass of 200 kDa. The purified beta-D-glucosidase only hydrolysed the glucoside substrates containing a terminal, non-reducing beta-D-glucose residue and was active on both aryl-beta-glucoside and cellobiose. This enzyme also exhibited less, but significant alpha-D-glucosidase activity and was capable of hydrolysing beta-1,6-linked diglucosides and gentiobiose. The Kapp m, V(max) and k(cat) values for p-nitrophenyl-beta-D-glucopyranoside were calculated to be 0.075 mM, 12.12 units/mg of protein and 44.44 glucose molecules released/s respectively. The beta-D-glucosidase retained its full activity after a 30 min incubation at 50 degrees C but was inactive after the same treatment at 70 degrees C. The enzyme appeared to be stable when the pH of the storage buffer was above 5.0. Maximal beta-D-glucosidase activity occurred at 65 degrees C and pH 6.0. This enzyme was competitively inhibited by glucose, cellobiose and salicin with K(i) values of 0.55, 0.52 and 0.81 mM respectively. The presence of Hg(2+) and N-bromosuccinimide inhibited the enzyme activity completely at 2 mM, while cysteine enhanced beta-D-glucosidase activity.

Amino Acids↗
PubMed1999

Ischemic preconditioning attenuates hypoperfusion after retinal ischemia in rats.

PURPOSE: Retinal blood flow (RBF) was measured in rats to test the hypotheses that hypoperfusion follows severe ischemia in the retina and that ischemic preconditioning (IPC) attenuates this change in blood flow. METHODS: Male Sprague-Dawley rats were anesthetized with halothane and mechanically ventilated by tracheostomy to maintain normocarbia and normoxia. Retinal ischemia was induced for 0, 5, 30, 60, 75, or 90 minutes. RBF was measured 60 and 150 minutes after the end of ischemia using the radioactive microsphere blood flow method, and electroretinography was performed during the first 120 minutes after ischemia to quantitate the extent of functional recovery. Additional groups received IPC (5 minutes of ischemia) 24 hours before 30, 60, or 75 minutes of ischemia. RESULTS: Control (0 minutes' ischemia) RBF was 22+/-3 ml/100 g per minute (mean +/- SE). At 60 minutes after 5, 30, 60, 75, or 90 minutes of ischemia, RBF was 15+/-2 (NS), 11+/-1, 8+/-2, 8+/-1, and 10+/-1 ml/100 g per minute, respectively (significance, P<0.05 versus control). At 150 minutes after 5, 30, 60, 75, or 90 minutes of ischemia, RBF was 18+/-3 (NS), 13+/-1, 12+/-3, 12+/-2, and 11+/-1 ml/100 g per minute respectively (significance, p<0.05 versus control). With prior IPC, RBF after 30 and 60 minutes of ischemia was 21+/-1 and 19+/-3 ml/100 g per minute (both NS compared with control; P<0.05 compared with 30 or 60 minutes of ischemia without IPC). When ischemia was 75 minutes in duration, IPC did not prevent postischemic hypoperfusion. The extent of recovery of the electroretinogram b wave was inversely related to the length of ischemia. CONCLUSIONS: Postischemic hypoperfusion is present in the rat retina 60 minutes after ischemia, does not resolve by 150 minutes after ischemia, and is attenuated by IPC when ischemia is 60 minutes or less in duration. Maintenance of postischemic perfusion in the retina may be one of the mechanisms involved in the neuroprotection afforded by IPC.

Animals↗