Biomedical subjects

J C Steiner

Publications and source records attributed to J C Steiner.

At least 19 recordsLinked to original sources

PubMed2005

In situ determination of refractive index and size of Bacillus spores by light transmission.

Light-extinction measurements in the wavelength range of 400 to 1000 nm are performed in situ on Bacillus subtilis endospores during heat-shock-induced activation. Simultaneous information on particle size and refractive indices during activation is calculated from the transmission spectra by use of the Gaussian ray approximation of anomalous diffraction theory. During activation the refractive index of the core decreases from 1.51 to 1.39, and the size increases from 0.38 to 0.6 microm.

Bacillus subtilis↗

PubMed1999

A comparison of instrumentation using Naviflex and Profile nickel-titanium engine-driven rotary instruments.

This study was designed to compare the changes in canal configuration resulting from instrumentation by either Profile or Naviflex instruments. Forty mesial canals in extracted human molar teeth were embedded and sectioned at two root levels. Reassembled teeth were instrumented with a modified crown-down technique as described in the Profile training video for Profile files and in a similar manner for Naviflex instruments. Superimposed pre- and postinstrumented cross-sectional root images were projected, traced, and scanned into a computer for analysis. Canal movement, in relation to the furca, and canal area change were recorded. The results showed no significant difference in canal center movement or canal area change between the Profile or Naviflex groups. The degree of canal curvature had no effect on canal center movement or canal area change.

Dental High-Speed Technique↗

PubMed1998

A comparison of curved canal transportation with balanced force versus lightspeed.

The Flex-R file was compared with the Lightspeed nickel-titanium file in respect to canal center movement and final canal area after instrumentation. Thirty-eight root canals in extracted human molars were divided into two equal groups of 19, in all of which the angle of curvature ranged from 20 to 35 degrees. After mounting in a mold, each root was sectioned at two locations, providing an apical and coronal section. Pre- and postinstrumentation 35 mm photographic slides of each section were projected, traced, and then scanned into a computer. From these computerized pre- and postinstrumentation images, the movement of the canal center and the area of each canal were computed at both the apical and coronal sections. Results showed significant difference in the apical canal center movement and postinstrumentation area with the Lightspeed yielding smaller values in both cases. Coronally, the Flex-R Lightspeed instruments demonstrated no significant difference in canal movement or postinstrumentation area. No significant correlation was found between the angle of root curvature and canal movement or the angle of root curvature and postinstrumentation canal area.

Dental Instruments↗

PubMed1997

Effect of chronic ethanol on reproductive and growth hormones in the peripubertal male rat.

Ethanol (EtOH) has previously been shown to have profound effects on various endocrine systems. The present study further investigates the action of EtOH on testosterone and on the GH-IGF-I axis. Since these hormones are particularly important in male rats progressing through puberty, we examined the effect of 10 days of EtOH treatment at three different ages (35, 50 and 65 days old) as male rats progressed through puberty into adulthood. After 10 days of feeding a 6% EtOH liquid diet, serum testosterone levels were markedly decreased in all three ages (P < 0.02 at 35 days, P < 0.01 at 50 days and P < 0.03 at 65 days). IGF-I was assessed and was differentially affected at each age. At 35 days IGF-I levels were suppressed by EtOH (P < 0.0002), at 50 days no change was apparent, and at 65 days levels were significantly higher in EtOH-treated (P < 0.01) compared with liquid-fed controls. The levels of IGF-I in the EtOH-treated animals paralleled pituitary GH mRNA levels with a significant fall in the expression of GH mRNA levels noted at 35 days (P < 0.04), no change at 50 days and a significant rise observed at 65 days (P < 0.03). At the hypothalamic level, GH-releasing hormone (GRF) mRNA was significantly reduced in the two younger EtOH-treated age groups compared with controls (P < 0.04 at 35 days; P < 0.02 at 50 days). At 65 days of age, EtOH did not alter GRF mRNA levels. No EtOH-induced changes were seen in GRF content at any age. These observations indicate definite age-related alterations in hormonal gene expression and circulating serum hormone levels and emphasize the importance of studying these critical peripubertal ages after chronic EtOH exposure.

Animals↗

PubMed1996

Comparison of stainless steel and nickel-titanium instruments in molar root canal preparation.

Forty mesial canals in extracted human molar teeth were embedded and sectioned at two root levels. Reassembled teeth were instrumented using a step-back technique with stainless steel (SS) or nickel-titanium (NT) K-type files. Superimposed pre- and postinstrumented cross-sectional root images were projected, traced, and scanned into a computer for analysis. The amount and direction of canal center movement, canal area change, and final canal shape were recorded. The results showed no significant difference in canal center movement or canal area change between the SS and NT groups. All canal centers deviated toward the furcation region at the height of curvature and in the opposite direction in apical sections. The degree of canal curvature had no correlation to canal center movement or canal area change. Fifty-three percent of SS and 68% of NT instrument preparations were classified as oval.

Alloys↗

PubMed1996

A comparison of curved canal instrumentation using nickel-titanium or stainless steel files with the balanced-force technique.

The Flex-R file was compared with the Onyx nickel-titanium file in respect to canal center movement and final canal area after balanced-force instrumentation. Forty-two root canals in extracted human molars were divided into two equal groups of 21, in all of which the angle of curvature ranged from 20 to 40 degrees. After mounting in a mold, each root was sectioned at two locations, providing an apical and a coronal section. Pre- and postinstrumentational 35-mm photographic slides of each section were superimposed, projected, traced, and then scanned into a computer. From these computerized pre- and postinstrumentation images, the movement of the canal center and the area of each canal were computed at both the apical and coronal sections. Results showed no significant difference in canal center movement or postinstrumentation area when Flex-R or Onyx files were used at the apical section. Coronally, the Flex-R files demonstrated more movement of the canal center. No significant correlation was found between the angle of root curvature and canal movement or the angle of root curvature and postinstrumentation canal area.

Dental Instruments↗

PubMed1996

Sustained effects of a single injection of ethanol on the hypothalamic-pituitary-gonadal axis in the male rat.

The hormones responsible for regulating the hypothalamic-pituitary-gonadal axis are essential for proper reproductive function. Ethanol (EtOH) has been shown to exert its effect at all three levels of this axis. The present study defines striking differences in the time course of recovery of luteinizing hormone (LH) in gonadally intact, compared with, castrated male rats after acute EtOH administration. Serum levels of LH and testosterone were measured at various time points up to 2 weeks (1.5, 3, 24, 48, 72, 96, 168, and 336 hr) after a single intraperitoneal injection of either saline or 3 g/kg of EtOH in intact adult male rats. One EtOH injection significantly suppressed testosterone levels as low as 20% (p < 0.01) of saline-injected intact rats. This occurred as early as 1.5 hr after EtOH administration (the first measured time point), and statistically significant suppression was sustained for 96 hr. Similarly, LH levels showed a significant decrease. However, this significant fall in LH did not begin until 3 hr (p < 0.05) and continued up to 96 hr (p < 0.01), with a gradual return to control levels at 168 and 336 hr after treatment. Despite the significant and prolonged fall in testosterone levels in the EtOH-treated intact rats, beta-LH mRNA levels were inappropriately not elevated, as would be expected in the context of low circulating testosterone. However, at 168 and 336 hr, steady-state levels of beta-LH mRNA were significantly higher than seen in saline-injected controls (p < 0.05 and p < 0.01, respectively), temporally correlating with the return of serum LH to control. LH levels in the castrated animals were significantly suppressed at 1.5 hr (p < 0.05) and 3 hr (p < 0.01) after EtOH treatment, compared with controls, yet they returned much more quickly by 24 hr after treatment. beta-LH mRNA levels of castrated animals also showed a significant depression at 1.5 and 3 hr, and returned to control levels by 24 hr. In these rats, the hypothalamic LH-releasing hormone mRNA levels were not altered by a single EtOH injection at any time point. However, in the intact animals, there was a transient increase in LH-releasing hormone mRNA at 72 and 96 hr (p < 0.01 and p < 0.05, respectively) that may lead to the upregulation of beta-LH mRNA expression. These studies indicate that EtOH causes prolonged decreases in important serum hormones that are essential to the reproductive axis of the adult male rat.

Animals↗

PubMed1992

In vivo and in vitro glycosaminoglycans from human dental pulp.

A qualitative assessment was made of the type of glycosaminoglycans (GAG) present in normal human dental pulp using electrophoresis on cellulose-acetate plates. A comparison was also made between the GAG derived directly from the dental pulp (in vivo) and those derived from cultured pulp fibroblasts from the same individual (in vitro). The results of this study showed four main types of GAG in normal human dental pulp tissue, which were dermatan sulfate, heparan sulfate, hyaluronic acid, and chondroitin sulfate. GAG synthesis from cultured pulp fibroblasts in vitro was different from the GAG present in the dental pulp (in vivo). Extracellular GAG, as well as pericellular GAG consisted of dermatan sulfate, hyaluronic acid, chondroitin sulfate, and heparin. Cellular GAG, however, contained only dermatan sulfate, hyaluronic acid, and chondroitin sulfate. There was no difference in type of GAG from the second and fourth passaged pulp fibroblasts.

Adolescent↗

PubMed1991

Flow cytometric analysis of human dental pulp tissue.

Existing knowledge regarding the cellular components of the dental pulp has been derived primarily from classical methods of histology and biochemistry. Since observations made from prepared tissue sections are static, it is not clear whether this accurately reflects the cellular dynamics of living pulp tissue. Therefore, we developed a method to analyze vital human pulpal tissue by flow cytometry. To test this method, two analyses of the prepared pulpal tissue were performed. First, the prepared tissue was stained with monoclonal antibodies to detect lymphocyte subpopulations. Second, the tissue was processed for DNA analysis of individual cells. Results demonstrated that lymphocytes bearing CD4 and CD8 antigens were clearly detected in pulpal tissue by this method. No B cells were found in any sample. DNA analysis revealed two distinct cell populations. Approximately 88% were small and 12% were large. According to DNA content, 90% of all cells were noncycling and 10% were cycling. These results demonstrate the feasibility of using flow cytometric analysis to examine, at a quantitative level, the cellular heterogeneity of the human dental pulp.

Antibodies, Monoclonal↗

PubMed1988