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Biomedical subjects

L L Lin

Publications and source records attributed to L L Lin.

At least 55 records · Page 3Linked to original sources
PubMed1997

A gene encoding for an alpha-amylase from thermophilic Bacillus sp. strain TS-23 and its expression in Escherichia coli.

An alpha-amylase gene from Bacillus sp. strain TS-23 was cloned and expressed by using its own promoter on the recombinant plasmid pTS917 in Escherichia coli. A cell fractionation experiment revealed that approximately 60% of the amylase activity was in the periplasmic space. Analysis and activity staining of the concentrated supernatant fraction by SDS-polyacrylamide gel electrophoresis showed an apparent protein band with a mol. wt of approximately 65,000. The amylase gene (amyA) consisted of an open reading frame of 1,845 bp encoding a protein of 613 amino acids with a calculated mol. wt of 69,543. The predicted amino acid sequence showed high homology with Bacillus species, E. coli and Salmonella typhimurium alpha-amylases. Deletion of 96 amino acids from the C-terminal portion of the amylase did not result in the loss of amylolytic activity. The truncated amylase, deletion of the first 50 amino acids from the N-terminus, was overexpressed in E. coli system and refolded to yield an activable enzyme.

Amino Acid Sequence↗
PubMed1997

Lactose-induced expression of Bacillus sp. TS-23 amylase gene in Escherichia coli regulated by a T7 promoter.

Bacillus sp. TS-23 amylase gene was amplified by polymerase chain reaction and cloned into the pET23(+) transcription vector. Lactose induction of Escherichia coli BL21(DE3) cells harbouring this recombinant plasmid resulted in the extracellular production of gene products. By the addition of 20 mmol l-1 lactose, the amylase activity of fermentation broth had a specific activity of 21 U mg-1 of protein.

Bacillus↗
PubMed1997

The choroidal blood flow response after flicker stimulation in chicks.

Form-deprivation myopia (FDM) can be prevented by exposing the animal to stroboscopic illumination (10 Hz). Flicker illumination is known to stimulate the release of dopamine (DA) from the retina. We hypothesize that DA was released and diffused into the choroid. To prove this hypothesis, we decided to undertake an investigation in chicks and measure choroidal blood flow (ChBF) during stimulation of the ocular fundus with diffuse flicker. White Leghorn chicks (2 weeks old) were used for this study. Different flash stimulations (5 Hz approximately 50 Hz) were given for 3 minutes, then ChBF was recorded with the PeriFlux flowmeter simultaneously and continuously for 5 minutes. Some birds are recorded up to 120 minutes to find out any late-onset effect. The ChBF was increased after flicker stimulation. The difference was statistically significant in 10 Hz, 20 Hz, and 30 Hz. The ChBF can maintain 20% higher for 60 minutes. Therefore, flicker illumination preventing FDM may be induced by the hyperactivity of ganglion cells, then stimulates the release of DA from the retina and suppresses the development of myopia.

Animals↗
PubMed1997

The regulation of the scleral growth associated with deprivation myopia in chicks.

The mechanism of axial elongation caused by experimental or clinical myopia is still unknown. We sought to explore the changes of scleral chondrocytes during myopia formation through the cell biology model. White Leghorn chicks were used for this study. The right eye was covered with a translucent goggle after hatching, and the left eye was left uncovered for control. The chicks were maintained on 12 hours light-dark cycle for two weeks, then sacrificed every other day and the eyeballs removed for study. Our results in the primary culture of scleral chondrocytes showed that the densities of chondrocytes on myopic eyes were significantly higher than those of the controlled non-myopic eyes, and 3H-thymidine incorporation rate also increased with the increasing of the concentration of fetal bovine serum. The PCNA index of chondrocytes in myopic eyes was also higher than that of the controlled non-myopic eyes. Thus, axial elongation of experimental myopia in the chick is the result of active tissue remodeling rather than passive scleral stretching alone.

Animals↗
PubMed1997

The effectiveness of 0.5% atropine in controlling high myopia in children.

Twenty highly myopic children (> or = -6.0 D) were treated with 0.5% atropine eyedrops once per night. Twelve subjects were initially treated with a short-acting cycloplegic agent, tropicamide (0.5%) (Group A), and the other eight subjects did not receive any myopic therapy before atropine (Group B). These cases were followed for up to five years. In Group A, the mean myopic progression rate after 0.5% atropine treatment was -0.01 +/- 0.04 D/M (Diopter/Month), which was significantly lower than that of the period during tropicamide treatment (-0.12 +/- 0.09 D/M) (p < 0.05). In Group B, the mean myopic progression rate after atropine therapy was begun was -0.04 +/- 0.06 D/M, which was also significantly slower than that of non-medication, -0.14 +/- 0.07 D/M (p < 0.05). The results suggested that 0.5% atropine is effective for slowing down myopic progression, even in highly myopic children.

Administration, Topical↗
PubMed1997

Influence of axial length on visual field defects in primary open-angle glaucoma.

With the high frequency of myopia in Taiwan, potential complications or associated conditions, such as glaucoma, are of great concern. To investigate the role of axial length in glaucoma, we enrolled 307 primary open-angle glaucoma (POAG) patients from 1986 through 1996. For the control group, 124 persons were recruited from a survey of a non-glaucoma population and the Ophthalmology Out-patient Department of the National Taiwan University Hospital. Routine eye examination, stereophotography of the optic disc, automated visual field tests, and A-scan ultrasonography were performed on each patient. The Glaucoma Hemifield test was used for analysis of visual field results. The mean axial length was longer in the POAG group than in the control group, especially in the younger age groups (40-59 yr). The POAG group was divided into a short-axial-length (SAL, axial length < 26 mm) group and a long-axial-length (LAL, axial length > or = 26 mm) group. Both subgroups had the deepest visual field defects in the upper and lower nasal areas. The LAL group had deeper visual field defects and the defects were more frequently involved in all sectors analyzed than the SAL group defects. The upper visual field had deteriorated more in the SAL group, whereas the depth of scotoma was similar in the upper and lower hemifields in the LAL group. Our results support the idea that glaucoma patients have a longer axial length than people without glaucoma, and that visual field defects are more pronounced in patients with LAL than in those with SAL.

Adult↗
PubMed1996

Traumatic cycloplegia and myopic anisometropia.

The pathogenesis of myopia and the mechanism of atropine in preventing myopic progression have long been widely discussed. Recent studies with animals have pointed to the possible role of the muscarinic receptor of the retina itself in regulating eye growth. This paper stresses that, for myopia in humans, the importance of accommodation still holds. Twenty-five recovered cases of previous traumatic hyphema, occurring under age 16, were collected. For four or more years, the patients were examined for ocular refraction, axial length, intraocular pressure, gonioscopy and accommodation time; the latter was measured with an accommodo-polyrecorder. Data from injured eyes and fellow eyes were compared and analyzed. The results indicated that, in the injured eyes the refractive status was invariably less myopic than in the fellow eye, and was not related to intraocular pressure. In injured eyes the accommodation time was highly correlated with the extent of angle recess. And the difference of anisometropia was also related to the extent of angle recess. These observations showed that there was a significant correlation between the degree of myopic anisometropia and the impairment of accommodation.

Accommodation, Ocular↗
PubMed1996

Changes in ocular refraction and its components among medical students--a 5-year longitudinal study.

PURPOSE: Myopic progression has been noted, especially during the period of puberty. It is interesting to investigate whether myopia will progress after the age of puberty and at what rate the changes in ocular components occur during its progression. METHODS: A 5-year longitudinal study was made of refraction and its components among 345 National Taiwan University medical students (690 eyes). The examinations included corneal curvature and cycloplegic refraction measured by auto-refractor and retinoscopy, and axial length measurement with A scan ultrasonography. The same procedures and instruments were used again after 5 years. RESULTS: The myopic prevalence increased from 92.8 to 95.8%; 21 new cases of myopia developed in the 5 years. The mean refractive error significantly increased from -4.26 +/- 2.66 D of freshmen to -4.94 +/- 2.70 D of clerks. The change in refractive error at the 5-year follow-up was 0.70 +/- 0.65 D more myopic for males and 0.54 +/- 0.64 D for females. The main change in the ocular components was in axial length, which increased from 25.54 to 26.05 mm in males and from 24.60 to 24.95 mm in females. Other optical components-including corneal curvature, anterior chamber depth, lens thickness-all remained relatively unchanged from the initial values. CONCLUSIONS: Myopia can progress after the age of puberty, but at a slower rate than during childhood. Axial elongation of the eyeball is the main component that changes in myopic progression.

Adolescent↗
PubMed1996

The blood-aqueous barrier in anisometropia and high myopia.

Functional disorder of the blood-ocular barrier has been suggested in cases of degenerative high myopia. Whether the blood-aqueous barrier among young high myopes with healthy vitreous suffers changes is worthy to be explored. Flare density was measured with the laser flare cell meter (Kowa) in highly myopic and anisometropic students. The mean flare density of highly myopic eyes in the myopic group (4.28 +/- 1.13 photon counts/ms) was similar to that of the emmetropic control group (4.24 +/- 1.79 photon counts/ms). Moreover, the difference in flare density between the two eyes of anisometropic patients was not statistically significant. Thus, the blood-aqueous barrier seems intact in young high myopes with healthy posterior vitreous and fundus.

Adolescent↗
PubMed1995

Calcium-mediated translocation of cytosolic phospholipase A2 to the nuclear envelope and endoplasmic reticulum.

Cytosolic phospholipase A2 (cPLA2) is activated by a wide variety of stimuli to release arachidonic acid, the precursor of the potent inflammatory mediators prostaglandin and leukotriene. Specifically, cPLA2 releases arachidonic acid in response to agents that increase intracellular Ca2+. In vitro data have suggested that these agents induce a translocation of cPLA2 from the cytosol to the cell membrane, where its substrate is localized. Here, we use immunofluorescence to visualize the translocation of cPLA2 to distinct cellular membranes. In Chinese hamster ovary cells that stably overexpress cPLA2, this enzyme translocates to the nuclear envelope upon stimulation with the calcium ionophore A23187. The pattern of staining observed in the cytoplasm suggests that cPLA2 also translocates to the endoplasmic reticulum. We find no evidence for cPLA2 localization to the plasma membrane. Translocation of cPLA2 is dependent on the calcium-dependent phospholipid binding domain, as a calcium-dependent phospholipid binding deletion mutant of cPLA2 (delta CII) fails to translocate in response to Ca2+. In contrast, cPLA2 mutated at Ser-505, the site of mitogen-activated protein kinase phosphorylation, translocates normally. This observation, combined with the observed phosphorylation of delta CII, establishes that translocation and phosphorylation function independently to regulate cPLA2. The effect of these mutations on cPLA2 translocation was confirmed by subcellular fractionation. Each of these mutations abolished the ability of cPLA2 to release arachidonic acid, establishing that cPLA2-mediated arachidonic acid release is strongly dependent on both phosphorylation and translocation. These data help to clarify the mechanisms by which cPLA2 is regulated in intact cells and establish the nuclear envelope and endoplasmic reticulum as primary sites for the liberation of arachidonic acid in the cell.

Animals↗
PubMed1995

Cytosolic phospholipase A2.

To summarize the regulation of cPLA2, we have proposed a model for the activation of cPLA2 based both on our previous studies (Clark et al., 1991; Lin et al., 1993) and the work of many others (Fig. 5). In this model, cPLA2 is tightly regulated by multiple pathways, including those that control Ca2+ concentration, phosphorylation states and cPLA2 protein levels, to exert both rapid and prolonged effects on cellular processes, such as inflammation. cPLA2 is rapidly activated by increased intracellular Ca2+ concentration and phosphorylation by MAP kinase. When cells are stimulated with a ligand for a receptor, such as ATP or PDGF, PLC is activated via either a G protein-dependent or -independent process, leading to the production of diacylglycerol (DAG) and inositol triphosphate (IP3). The rise in these intracellular messengers cause the activation of PKC and mobilization of intracellular Ca2+. Alternatively, the increase in intracellular Ca2+ can result from a Ca2+ influx. Increased Ca2+ acts through the CaLB domain to cause translocation of cPLA2 from the cytosol to the membrane where its substrate, phospholipid, is localized. This step is essential for the activation of cPLA2 and may account for the partial activation of cPLA2 in the absence of phosphorylation. MAP kinase activation can occur through both PKC-dependent and -independent mechanisms (Cobb et al., 1991; Posada and Cooper, 1992; Qiu and Leslie, 1994). In many cases, this pathway is also G protein-dependent. Activated MAP kinase phosphorylates cPLA2 at Ser-505, causing increased enzymatic activity of cPLA2, which is realized only upon translocation of cPLA2 to the membrane. Therefore, full activation of cPLA2 requires both increased cytosolic Ca2+ and cPLA2 phosphorylation at Ser-505. In a more delayed response, cPLA2 activity in the cells can be controlled by changes in its expression levels, such as in response to inflammatory cytokines and certain growth factors. Thus the expression level of cPLA2 is regulated by both transcriptional and post-transcriptional mechanisms.

Amino Acid Sequence↗
PubMed1995

Preoperative mitomycin-C subconjunctival injection and glaucoma filtering surgery.

Intraoperative mitomycin-C application has been well accepted recently as a useful adjunctive procedure to enhance the filtering effect in glaucoma surgery. However, the exact dose of mitomycin-C left after such a procedure in the ocular tissue is variable and unclear. It is important to determine such residual because of potential long-term toxicity of mitomycin-C to the eye. Based on previous successful experience using preoperative mitomycin-C subconjunctival injection in the THC-YAG laser sclerostomy on rabbits, the effect of intraocular pressure (IOP) control and its clinical observation was studied in six eyes of six refractory and high risk glaucoma patients by subconjunctival 1.2 micrograms to 3.6 micrograms mitomycin-C injection 24 to 72 hours prior to classic, routine, limbal-based trabeculectomy surgery. After 18 months of satisfactory clinical observation of the first eye for IOP, functioning bleb appearance and smooth clinical course, the same procedure was used on an additional five eyes, with a follow-up period of more than five months. Average IOP was reduced from 27.8 mm Hg (range 24 to 34 mm Hg) preoperatively to 9.5 mm Hg (range 5 to 14 mm Hg) postoperatively, with a smooth clinical course. The advantages of such preoperative subconjunctival mitomycin-C injection are emphasized here.

Adolescent↗
PubMed1995

The effects of Qi-Qong ocular exercise on accommodation.

Visual-training methods in management of myopia are suggested as possibly leading to normal vision or an improvement in the refractive state. The purpose of this work was to investigate the hypothesis that a Qi-Qong ocular exercise improves visual function by training the accommodation bias. Variations of pupil size, accommodative amplitude, latency and speed of accommodative response and accommodative adaptation were evaluated objectively. The accommodative state was monitored with an objective infrared refractometer (Nidek AA-2000). Subjects were divided into two groups: experimental (n = 9), and control (n = 8). Subjects of the experimental group undertook the Qi-Qong ocular exercise for at least three years, and were able to perform the exercise smoothly and gently. Subjects of the control group had no knowledge of the Qi-Qong ocular exercise, but were given the same testing procedures as the experimental group. Results showed that Qi-Qong ocular exercise can improve the accommodative amplitude and accelerate the accommodative response slightly, but there was no effect on the latency of accommodative response. Furthermore, the level of accommodative adaptation was elevated, and the pupil became slight miotic. Therefore, the mechanism of visual improvement may undergo a great accommodative adaptation and produce a pinhole effect by miosis of the pupil. Methods of visual training can produce a false image of visual improvement from an enhanced parasympathetic response to a task, but this effect may be a factor that induces progression of myopia.

Accommodation, Ocular↗
PubMed1994

Encapsulated egg deposition pattern of Schistosoma japonicum in the peritoneal cavity of mice.

Thirty-four albino mice were each exposed to 20 cercariae of Schistosoma japonicum by the intraperitoneal or percutaneous route and killed after 60-127 days. The peritoneal cavity of each mouse was flushed and worms in the portal vein system were perfused with citrated saline. After sedimentation, washings were examined microscopically. Mature worms were only found in the portal vein system. The worm recovery rate was much higher by percutaneous infection (61.2%) than by intraperitoneal (37.1%). The encapsulated egg granulomas were observed either in the peritoneal cavity or on the intestinal wall; the mean number of encapsulated egg granulomas was also higher in the former (1.6) than in the latter (0.6). The average number of eggs per granuloma was very similar by both routes (10.7 and 11.4). The mean size of encapsulated egg granulomas (529 microns) was increased correspondingly with the number of eggs (range 181-985 microns). The percentage of viable eggs within the granulomas in the peritoneal cavity (77%) was much higher than those on the intestinal wall (18%). Encapsulated egg granulomas were usually ovoid although some had an irregular shape.

Animals↗
PubMed1994

Experimental myopia in chickens induced by corneal astigmatism.

Astigmatism has been suggested to be an important factor in the production and/or progression of myopia. Chickens have been used as a myopic animal model for several years. In the present investigation our aim was to evaluate the importance of surgically induced corneal astigmatism by peripheral corneal incision with compression suture in one eye, the right, of 3-day-old chicks. Vertical incision (2 mm) with compression suture (nylon 9-0, one stitch) induces against-the-rule astigmatism, horizontal incision with compression induces with-the-rule astigmatism. Four groups were studied 1) with one vertical cut, 2) one horizontal cut, 3) two vertical cuts, 4) two horizontal cuts. The eyes were measured by caliper after 8 weeks. Eye enlargements were induced in all groups, however, less by one cut (astigmatism around 5 diopters) than by two cuts (astigmatism 10 diopters, or more). In the latter groups the pattern of equatorial eye enlargement depended on the axis of the induced astigmatism, the greater elongation being associated with the strongest refracting corneal meridian. All considered, the results suggest that significant corneal astigmatism could be another factor in the production of myopia, possibly acting by way of optical degradation of retinal image quality.

Animals↗