Search PubMed⌕ Search

Biomedical subjects

L Tao

Publications and source records attributed to L Tao.

198 records · Page 11Linked to original sources
PubMed1988

Factors influencing cell shape in the mutans group of streptococci.

Electron and light microscopic and growth studies of representatives of the diverse species of mutans streptococci revealed the cells to be either bacillary or coccoid in shape. Some strains changed from bacillary to coccoid if the HCO3-/K+ ratio of the media was increased and from coccoid to bacillary if the ratio was decreased. Doubling times of rods and cocci were the same despite an HCO3-/K+ ratio change between 0.008 and 2.84. For strain 10449S, no tested anions or cations substituted for HCO3- or K+ to produce this effect, except for B4O7(2-). Strain 10449S grown at a high B4O7(2-)/K+ ratio became ellipsoid, and this phenomenon was associated with slower doubling times. Up to three incomplete septa could be observed in one rod, but no more than one incomplete septum could be observed in either ellipsoid or spherical cells. Interseptal distances were greatest in rods, shorter in spheres, and shortest in ellipses. All of the above differences were statistically significant (P less than 0.001).

Microscopy, Electron↗
PubMed1988

Comparison of in vivo vs. in vitro bonding of composite resin to the dentin of canine teeth.

Dogs were utilized in a study to compare the bond strengths of dentin bonding agents made to dentin in vivo and then again in vitro in the same teeth 30 min, one day, one week, and one month post-extraction. No statistically significant differences were observed between bonds made in vivo and those made in vitro at any time period. Contamination of the dentin surfaces with blood or saliva lowered the bond strengths, but these could be restored to control values by re-surfacing of the dentin with a bur.

Animals↗
PubMed1987

Bicarbonate and potassium regulation of the shape of Streptococcus mutans NCTC 10449S.

Morphological changes of S. mutans NCTC 10449S associated with growth in modified Jordan medium and FMC medium (Terleckyj et al., Infect. Immun. 11:649-655, 1975) were studied by scanning electron microscopy. The cells were bacillary in Jordan medium, but coccoid and of unequal size in FMC. Transfer of the cells from Jordan medium to FMC and vice versa reversed their shapes, as did salt exchange between these media. Morphological changes could not be ascribed to either medium pH, concentration of P, or Na+/K+ ratio. However, they were growth dependent, since the changes did not occur when the cells were suspended in salt components alone or in media supplemented with protein synthesis inhibitors. Only a high bicarbonate/K+ ratio, as in FMC, produced spherical cells, whereas cells remained bacillary in medium with a low bicarbonate/K+ ratio, as in Jordan medium. Manipulating this ratio in other media resulted in similar shape changes. Thus, the shape of S. mutans 10449S can be dictated by the ratio of bicarbonate to K+ in the growth medium.

Bicarbonates↗
PubMed1986

Circadian stage-dependent prolongation by cyclosporine of segmental pancreatic allograft function in the rat.

While the toxicity of many drugs has been reduced by their administration at certain circadian rhythm stages (if not at certain times of day), as shown herein, direct therapeutic benefit from the improvement of the desired effect can be obtained by the circadian timing of intraperitoneal cyclosporine (Cs) for Lewis rats bearing an ACI segmental pancreas allograft. Under conditions of light (L) and darkness (D) alternating at 12-hour intervals, staggered by 8 h in 3 rooms kept at 24 degrees C, the effect of Cs in delaying graft rejection was improved by timing. When the mean time to rejection during the L span is equated to 100%, graft function is prolonged by 40% at the right time (injection daily during the D span) as compared to the wrong time (injection daily during the L span).

Animals↗
PubMed1986

Investigation of bilirubin removal by NK-110 resin hemoperfusion in jaundiced dogs.

A jaundiced dog model was made by common bile duct-inferior vena cava shunt with a silicon rubber tube. Blood bilirubin levels increased from 0.25 +/- 0.16 (SD) mg% to 15 +/- 1.4 (SD) mg%. These dog models were treated with a column containing 200 gm of macroreticular resin NK-110 which was linked between the femoral artery and vein. The rate of blood flow through the column was 200 ml/min. It was shown that total bilirubin reduced from 15 +/- 1.4 (SD) to 7.4 +/- 0.61 (SD), conjugated bilirubin decreased from 6.97 +/- 0.63 to 3.5 +/- 0.33 (SD) and unconjugated bilirubin from 7.8 +/- 2.1 to 4.2 +/- 0.4 (SD). There were no significant changes in protein, electrolyte, blood gases and acid base balance. Results show that NK-110 resin has good blood-compatible and adsorption properties.

Adsorption↗
PubMed1985

Effect of surgery and efferent duct ligation on testicular blood flow and testicular steroidogenesis in the rat.

A moderate reduction in testicular blood flow was observed in both testes 24 h after unilateral efferent duct ligation without any corresponding change in testosterone secretion as indicated in the peripheral blood, in testicular venous blood, or in testicular tissue fluid. At 21 days a pronounced unilateral decrease in blood flow was associated with the extensive degeneration of tubules in the testis on the ligated side. These changes were also associated with decreased testosterone secretion by the testis on the ligated side, although Leydig cell function was not abolished since testosterone in the tissue increased rather than decreased. It is therefore concluded that testicular blood flow may play an important role in the changes of testosterone secretion that follow unilateral efferent duct ligation.

Animals↗
PubMed1975

Fertility reduction in an MCH/family planning program: a model for projection.

One of the important questions in an integrated maternal and child health/family planning program is the likely effects on fertility rates if given proportions of a stated target population can be reached and provided with family planning services. The question is easy, but the process of obtaining viable estimates of potential fertility decline from this type of program is complicated. First of all, the number of women in the target population must be estimated. Next, it is necessary to make various assumptions and estimates concering the types of contraceptives accepted, the age distribution of acceptors, the sets of continuation rates that go with each age/method specific group of women, and a variety of other factors. This article describes and illustrates a procedure for estimating potential fertility declines with an integrated maternal and child health/family planning program.

Age Factors↗
PubMedDate not supplied

Efficient and accurate time-stepping schemes for integrate-and-fire neuronal networks.

To avoid the numerical errors associated with resetting the potential following a spike in simulations of integrate-and-fire neuronal networks, Hansel et al. and Shelley independently developed a modified time-stepping method. Their particular scheme consists of second-order Runge-Kutta time-stepping, a linear interpolant to find spike times, and a recalibration of postspike potential using the spike times. Here we show analytically that such a scheme is second order, discuss the conditions under which efficient, higher-order algorithms can be constructed to treat resets, and develop a modified fourth-order scheme. To support our analysis, we simulate a system of integrate-and-fire conductance-based point neurons with all-to-all coupling. For six-digit accuracy, our modified Runge-Kutta fourth-order scheme needs a time-step of Delta(t) = 0.5 x 10(-3) seconds, whereas to achieve comparable accuracy using a recalibrated second-order or a first-order algorithm requires time-steps of 10(-5) seconds or 10(-9) seconds, respectively. Furthermore, since the cortico-cortical conductances in standard integrate-and-fire neuronal networks do not depend on the value of the membrane potential, we can attain fourth-order accuracy with computational costs normally associated with second-order schemes.

Action Potentials↗
PubMedDate not supplied

Electrolyte composition of rete testis fluid and cauda epididymal plasma and spermatozoa from rats following gossypol treatment.

This investigation was undertaken to study the potassium and sodium concentrations in rete testis fluid and cauda epididymal plasma and spermatozoa following gossypol treatment. Rats were treated orally with gossypol acetic acid at a dose of 15 mg/kg/day for 3 and 6 weeks respectively. There were not abnormal findings in the ionic concentrations of cauda epididymal plasma following 3 or 6-week-treatment. After 6 but not 3 weeks the spermatozoa in the cauda epididymidis were rendered almost completely immotile and malformed with a significant reduction in their potassium concentration and rise in their sodium concentration. No abnormal findings in the morphological picture of the germinal epithelium were observed under such circumstances and fluid and sperm from the rete testis were normal. Therefore, a direct action of gossypol may be exerted locally on the spermatozoa in the epididymis.

Animals↗
PubMedDate not supplied

Exposure limits for ultra-short wave radiation in work environments.

Exposure limit values for ultra-short wave radiation of humans were derived on the basis of epidemiological survey and experimental exposure of rabbits. Eighteen male rabbits were divided into 4 groups randomly. Three groups were irradiated with ultra-short waves (100 MHz) at 35, 1.5-3.5, and 0.07 mW/cm2 power density in an E-polarized TEM Cell at 24 +/- 4 degrees C ambient temperature. The last group in a sham chamber served as controls. Irradiation was performed 3 hours per day, 5 days per week for 24 weeks. Thermal effects occurred in the group irradiated at 35 mW/cm2. The thermal threshold limit value was set at 1.5 mW/cm2. An epidemiological survey was carried out on 136 factory workers and TV operators exposed over one year to ultra-short wave radiation at 0.2 mW/cm2. They were compared with 108 controls. The only complaint of the exposed group was neurosis. The exposure limit value (ELV) to short wave radiation was set at 0.2 mW/cm2 by using a 15- and 20-fold safety factor.

Animals↗
PubMedDate not supplied

Dentin permeability: effects of crown preparation.

Sequential crown reductions of extracted human teeth were made to evaluate both regional differences in dentin permeability and the effects of tooth reduction. Two different methods of tooth reduction were used. In group 1, tooth reduction was nonuniform but was done in a manner similar to conventional crown preparations. Maximum, total crown permeability was measured using a pressurized fluid filtration technique after removing the smear layer. Regional reductions in permeability were accomplished by creating smear layers on mesial, distal, buccal, lingual, and occlusal surfaces sequentially. Between each step, changes in dentin permeability were measured. In group 2, tooth reductions were uniform and regional permeability was reduced by localized application of potassium oxalate. Both methods demonstrated increased permeability of dentin as the prepared surfaces approached the pulp chamber. Generally, the mesial surfaces were more permeable than the distal surfaces. The occlusal and lingual surfaces were the least permeable regions.

Adult↗
PubMedDate not supplied

Comparison of Gluma bond strength to primary vs. permanent teeth.

The purpose of this study was to measure the shear bond strength of Gluma/Lumifor (Gluma and Lumifor--Columbus Dental, St. Louis, MO) to the occlusal dentin of primary first and second molars, permanent first and second molars and premolars. The data were examined for differences using a one-way analysis of variance and Duncan's Multiple Range test. The shear bond strength, (kc/cm2, x +/- SEM) to primary molars was 85.6 +/- 13.7, to permanent molars was 110.1 +/- 9.3, and to premolars was 124.0 +/- 9.3. Gluma/Lumifor provides moderately good bonding to dentin. The bond strengths of Gluma/Lumifor to primary molars was statistically significantly lower than to permanent teeth.

Analysis of Variance↗