Biomedical subjects

H Koo

Publications and source records attributed to H Koo.

At least 19 recordsLinked to original sources

PubMed2006

Influence of cranberry juice on glucan-mediated processes involved in Streptococcus mutans biofilm development.

Cranberry juice (CJ) has biological properties that may provide health benefits. In this study, we investigated the influence of CJ (pH 5.5) on several activities in vitro associated with the development of Streptococcus mutans UA159 biofilms. The ability of CJ to influence the adherence of S. mutans to either saliva- (sHA) or glucan-coated hydroxyapatite (gsHA), and to inhibit the glucan production by purified glucosyltransferases adsorbed to sHA was determined. For the adherence assays, we used both uncoated and saliva-coated bacterial cells. Furthermore, we examined whether CJ interferes with the viability, development, polysaccharide composition and acidogenicity of S. mutans biofilms. A solution containing equivalent amounts of glucose, fructose and organic acids at pH 5.5 was used as negative control. The adherence of S. mutans (uncoated and saliva-coated) to either sHA or gsHA treated with 25% CJ (v/v) was remarkably reduced (40-85% inhibition compared to control: p < 0.05), indicating that CJ effectively blocked the bacterial adherence to binding sites in salivary pellicle and in glucans. In contrast, when the bacterial cells alone were treated with CJ they adhered to the similar untreated surfaces. Cranberry juice (25%, v/v) also inhibited the activities of surface-adsorbed GTF B and C (70-80% inhibition compared to control, p < 0.05). The effect of CJ on the viability of microorganisms in biofilms was not significant. Biofilm formation and accumulation were significantly reduced by topical applications of 25% CJ (v/v) twice daily with 1-min exposures (p < 0.05). The biomass and insoluble glucan content of the biofilms in addition to its acidogenicity were significantly reduced by cranberry treatments (p < 0.05). Our data show that cranberry juice inhibited glucan-mediated biofilm development and acid production, and holds promise as a natural product to prevent biofilm-related oral diseases.

Analysis of Variance↗

PubMed2006

Effect of sucrose concentration on dental biofilm formed in situ and on enamel demineralization.

The relationship between sucrose concentration and cariogenic potential was studied in situ. Adult volunteers wore intraoral palatal appliances containing human dental enamel blocks, which were extraorally submitted 8 times a day for 14 days, to the treatments: deionized distilled water and sucrose solutions from 1 to 40%. The biofilm formed was analyzed with respect to acidogenicity and biochemical composition; enamel demineralization was evaluated by microhardness. The results showed that 1% sucrose is less cariogenic than 5% or higher concentrations, although sucrose solution at 40% was still able to increase the concentration of insoluble polysaccharide in the biofilm formed. The findings suggest that the threshold of sucrose solution concentration for the formation of a cariogenic biofilm is 5%, which provided the same cariogenic potential as that observed for 10 and 20% sucrose solution.

Adult↗

PubMed2006

The role of sucrose in cariogenic dental biofilm formation--new insight.

Dental caries is a biofilm-dependent oral disease, and fermentable dietary carbohydrates are the key environmental factors involved in its initiation and development. However, among the carbohydrates, sucrose is considered the most cariogenic, because, in addition to being fermented by oral bacteria, it is a substrate for the synthesis of extracellular (EPS) and intracellular (IPS) polysaccharides. Therefore, while the low pH environment triggers the shift of the resident plaque microflora to a more cariogenic one, EPS promote changes in the composition of the biofilms' matrix. Furthermore, it has recently been shown that the biofilm formed in the presence of sucrose presents low concentrations of Ca, P(i), and F, which are critical ions involved in de- and remineralization of enamel and dentin in the oral environment. Thus, the aim of this review is to explore the broad role of sucrose in the cariogenicity of biofilms, and to present a new insight into its influence on the pathogenesis of dental caries.

Biofilms↗

PubMed2005

Two missense mutations of EGR2 R359W and GJB1 V136A in a Charcot-Marie-Tooth disease family.

During mutational analysis of Charcot-Marie-Tooth (CMT) causative genes, we identified a CMT family with two missense mutations in different genes. A R359W mutation in EGR2 was shared by the affected daughter (proband) and her father. In addition, she had a V136A mutation in GJB1, which was determined to be a de novo mutation. The daughter with two different gene mutations showed more severe clinical, electrophysiological and histopathological phenotypes than her father who had only the EGR2 mutation. We suggest that these phenotypic differences between the proband and her father may have been caused by an altered effect of the genetic modifier in EGR2, or by the additive effect of the EGR2 and GJB1 mutations.

Age of Onset↗

PubMed2005

Some chemical composition and biological activity of northern Argentine propolis.

Twenty-five samples of propolis were collected from seven different regions in northern Argentina; ethanolic extracts of propolis were prepared from all samples, and the respective samples were examined for UV absorption spectra, RPHPTLC, RPHPLC, antimicrobial activity, antiradical activity, and total phenolic content. It was found that 16 of the 25 samples showed a phenolic profile similar to that found in samples from southern Brazil and corresponding to poplar-based propolis and that the rest of the samples showed a different profile and higher antimicrobial and antiradical activities.

Anti-Bacterial Agents↗

PubMed2005

Effects of Mikania genus plants on growth and cell adherence of mutans streptococci.

The present study evaluated the chemical composition and the antimicrobial activity of the extracts and fractions of Mikania laevigata and Mikania glomerata on growth and cell adherence of mutans streptococci. Ethanolic extract, hexane and ethyl acetate fractions of Mikania laevigata and Mikania glomerata were chemically identified by chromatographic methods and tested on mutans streptococci from culture collection and clinical isolates. Twenty-two compounds were identified in both Mikania extracts, including coumarin, 1-octadecene, and diterpenic, cupressenic and kaurenoic acids. Antimicrobial activity was assessed by determination of the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and inhibition of cell adherence to a glass surface. Hexane fraction from both plant extracts was the most effective in inhibiting the growth of the bacterial strains tested (MIC values between 12.5 microg/ml and 400 microg/ml, and MBC values between 25 microg/ml and 400 microg/ml). In addition, sub-MIC levels of the crude extracts and their hexane fractions significantly inhibited the adherence of the microorganisms to a glass surface. The data indicate that the biologically active compounds are present mostly in the hexane fraction of both Mikania species, which showed remarkable inhibitory activities against mutans streptococci. Mikania genus plant is a promising source for novel antimicrobial agents against oral pathogens.

Anti-Bacterial Agents↗

PubMed2005

Use of the Zung depression scale in patients with traumatic brain injury: 1 year post-injury.

OBJECTIVE: The purpose of this study was to examine if the physical disabilities of patients with traumatic brain injury (TBI) would influence the assessment of depression when using the Zung depression scale. METHOD: Patients with TBI (n=59) were assessed 1 year after injury for depression by both a psychiatrist and the use of the Zung depression scale. RESULTS: By psychiatric evaluation, seven of 17 (41%) patients with severe TBI and one of 20 (5%) of the patients with moderate TBI were diagnosed with major depressive disorder. With the Zung depression scale, 10 of 17 (59%) patients with severe TBI met the cut-off (scored >55) for depression, whereas none of the patients with moderate (n=20) or mild (n=22) TBI did. The mean (SD) scores of the somatic scale were 2.91 (0.93), 2.49 (0.92) and 1.25 (0.43) for each group. The mean scores of the affective scale were 2.58 (0.90), 1.85 (0.79) and 1.24 (0.46). For patients with moderate (p<0.05) and severe (p<0.10) TBI, scores on the somatic items exceeded scores on their affective items. No difference in somatic and affective scale scores was noted for the patients with mild TBI. CONCLUSION: The increased endorsement of somatic results may be the somatic difficulties associated with traumatic brain injury.

Adolescent↗

PubMed2005

Apigenin and tt-farnesol with fluoride effects on S. mutans biofilms and dental caries.

Apigenin (Api) and tt-farnesol (Far) are two naturally occurring agents that affect the development of cariogenic biofilms. Fluoride (F) interferes physicochemically with caries development and also exhibits antibacterial activity. We examined whether the association of Api and Far enhance the anti-caries properties of F by acting cooperatively on the expression of virulence of Streptococcus mutans. The biological effects of each of the agents were greatly enhanced when used in combination with F. In general, biofilms treated with Api and/or Far in combination with F displayed less biomass and fewer insoluble glucans and iodophilic polysaccharides than did those treated with the test agents alone (P < 0.05). The combination of the test agents with F was highly effective in preventing caries development in rats, especially Api+Far+F, and results were comparable with those observed with chlorhexidine + F (positive control). Results from these studies showed that apigenin and tt-farnesol may enhance the cariostatic effectiveness of fluoride.

Animals↗

PubMed2003

Inhibition of Streptococcus mutans biofilm accumulation and polysaccharide production by apigenin and tt-farnesol.

OBJECTIVES: Apigenin is a potent inhibitor of glucosyltransferases and tt-farnesol affects the membrane integrity of Streptococcus mutans. We investigated the influence of apigenin and tt-farnesol, alone and in combination, on the accumulation, polysaccharide composition and viability of S. mutans UA159 biofilms. METHODS: Initially, biofilms were grown for 54 h; then, the early-formed biofilms were treated for 1 min twice daily with one of the following: (i). 1.33 mM tt-farnesol; (ii). 1.33 mM apigenin; (iii). apigenin + tt-farnesol (1.33 mM each); (iv). vehicle control (20% ethanol with 0.75% dimethyl sulphoxide); (v). 0.12% chlorhexidine (1.33 mM); or (vi). physiological saline (145 mM NaCl). The procedure was repeated at biofilm ages of 78 and 102 h, and biofilms were harvested at 126 h. The dry weight, protein concentration, number of cfu, and polysaccharide composition per biofilm were determined. RESULTS: The dry weights of the biofilms treated with the test agents were significantly less (30-50%) than those treated with vehicle control (P < 0.05). Biofilms treated with the test agents also resulted in lower amounts of extracellular alkali-soluble glucans, intracellular iodophilic polysaccharides and, to a lesser extent, fructans. The fructosyltransferase activity was affected only by apigenin and apigenin + tt-farnesol. The recoverable viable counts of S. mutans were slightly lower (0.5 to 1 log10 decrease in cfu/biofilm) after apigenin and tt-farnesol treatments compared with the vehicle control. Chlorhexidine displayed potent bactericidal activity, and virtually halted the further accumulation of early-formed (54 h old) biofilms. CONCLUSIONS: Apigenin and tt-farnesol affected the accumulation and polysaccharide content of S. mutans biofilms without major impact on the bacterial viability.

Anti-Infective Agents, Local↗

PubMed2003

Inhibition of human leukemia in an animal model with human antibodies directed against vascular endothelial growth factor receptor 2. Correlation between antibody affinity and biological activity.

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) have been implicated in promoting solid tumor growth and metastasis via stimulating tumor-associated angiogenesis. We recently showed that certain 'liquid' tumors such as leukemia not only produce VEGF, but also express functional VEGFR, resulting in an autocrine loop for tumor growth and propagation. A chimeric anti-VEGFR2 (or kinase insert domain-containing receptor, KDR) antibody, IMC-1C11, was shown to be able to inhibit VEGF-induced proliferation of human leukemia cells in vitro, and to prolong survival of nonobese diabetic-severe combined immune deficient (NOD-SCID) mice inoculated with human leukemia cells. Here we produced two fully human anti-KDR antibodies (IgG1), IMC-2C6 and IMC-1121, from Fab fragments originally isolated from a large antibody phage display library. These antibodies bind specifically to KDR with high affinities: 50 and 200 pM for IMC-1121 and IMC-2C6, respectively, as compared to 270 pM for IMC-1C11. Like IMC-1C11, both human antibodies block VEGF/KDR interaction with an IC(50) of approximately 1 nM, but IMC-1121 is a more potent inhibitor to VEGF-stimulated proliferation of human endothelial cells. These anti-KDR antibodies strongly inhibited VEGF-induced migration of human leukemia cells in vitro, and when administered in vivo, significantly prolonged survival of NOD-SCID mice inoculated with human leukemia cells. It is noteworthy that the mice treated with antibody of the highest affinity, IMC-1121, survived the longest period of time, followed by mice treated with IMC-2C6 and IMC-1C11. Taken together, our data suggest that anti-KDR antibodies may have broad applications in the treatment of both solid tumors and leukemia. It further underscores the efforts to identify antibodies of high affinity for enhanced antiangiogenic and antitumor activities.

Animals↗

PubMed2003

Effects of fluoride and aluminum from ionomeric materials on S. mutans biofilm.

Ionomeric materials release different proportions of fluoride and aluminum. Their simultaneous effect on the acidogenicity and composition of S. mutans biofilm is unknown. Six cylindrical specimens of each material (Ketac-fil, Vitremer, Fuji-Ortho LC, F-2000, and Z-100) were incubated with S. mutans GS-5 in culture media containing 5% sucrose (w/v). The media were changed daily for seven days, during which the pH and concentrations of fluoride and aluminum were determined. Furthermore, the concentrations of these ions and insoluble polysaccharide were determined in the biofilm formed at the end of the experimental period. The results showed that all the materials tested released fluoride. However, Vitremer released the highest amount of aluminum and was the most effective in reducing the acidogenicity of S. mutans biofilms. It also significantly affected both biofilm formation and composition. Thus, this study suggests that aluminum released by ionomeric materials may enhance the biological effects of fluoride.

Acrylic Resins↗

PubMed2002

Effects of apigenin and tt-farnesol on glucosyltransferase activity, biofilm viability and caries development in rats.

Propolis, a resinous hive product secreted by Apis mellifera bees, has been shown to reduce the incidence of dental caries in rats. Several compounds, mainly polyphenolics, have been identified in propolis. Apigenin and tt-farnesol demonstrated biological activity against mutans streptococci. We determined here their effects, alone or in combination, on glucosyltransferase activity, biofilm viability, and development of caries in rats. Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and treated topically twice daily as follows: (1) tt-farnesol, (2) apigenin, (3) vehicle control, (4) fluoride, (5) apigenin +tt-farnesol, and (6) chlorhexidine. Apigenin (1.33 mM) inhibited the activity of glucosyltransferases in solution (90-95%) and on the surface of saliva-coated hydroxyapatite beads (35-58%); it was devoid of antibacterial activity. tt-Farnesol (1.33 mM) showed modest antibacterial activity against biofilms and its effects on glucosyltransferases were minimal. The incidence of smooth-surface caries was significantly reduced by apigenin +tt-farnesol (60%), fluoride (70%), and chlorhexidine (72%) treatments compared to control (P < 0.05).

Analysis of Variance↗

PubMed2001

Expression of glial cell line-derived neurotrophic factor (GDNF) in the developing human fetal brain.

GDNF expression was examined immunocytochemically in developing human fetal brains obtained from aborted fetuses ranging from 7 to 39 weeks in gestational age. At 7-8 weeks, strong immunoreactivity was noted within radial glial processes, glia limitans and choroid plexus of the telencephalic vesicle. By 10 weeks, ependymal cells, primitive matrix cells and early developing cortical plate neurons showed positive staining. By 15-16 weeks, migrating neurons in the subventricular and intermediate zones and in the cortical plate were strongly positive for GDNF. The glia limitans of the cerebral cortex and subependymal astrocytes remained positive at this time. As fetal age increased, GDNF expression shifted to neurons and glial cells in the deeper structures of the brain. The most prominent GDNF staining was observed in the cytoplasm and dendrites of Purkinje cells of the cerebellum by 25 weeks and thereafter. Pyramidal neurons of the CA1 region and granule cells of the dentate fascia of the hippocampus, neurons of the entorhinal cortex, and scattered neurons within the brain stem, medulla and spinal cord all showed strong GDNF staining by 25-35 weeks. Widespread GDNF expression in neuronal and non-neuronal cells with distinct developmental shifts suggests that GDNF may play a critical role in the survival, differentiation and maintenance of neurons at different stages of development in the developing human fetal brain.

Aging↗

PubMed2000

Effect of a new variety of Apis mellifera propolis on mutans Streptococci.

The effects of a new variety of propolis, from Northeastern Brazil (BA), on growth of mutans streptococci, cell adherence, and water-insoluble glucan (WIG) synthesis were evaluated. Propolis from Southeastern (MG) and Southern (RS) Brazil were also tested as an extension of our previous work. Ethanolic extracts of propolis (EEP) were prepared and analyzed by reversed-phase HPLC. For the antibacterial activity assays, minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of EEPs against Streptococcus mutans, S. sobrinus, and S. cricetus were determined. Cell adherence of S. mutans and S. sobrinus to a glass surface was measured spectrophotometrically at 550 nm. WIG synthesized from sucrose by glucosyltransferase (Gtf) was extracted and quantified by the phenol-sulfuric method. The HPLC profile of the new variety of propolis was entirely different from Southeastern and Southern propolis. Neither flavonoid aglycones nor p-coumaric acid were detected in EEP BA. All EEPs demonstrated biological activities against mutans streptococci; EEP BA showed the highest potency in all in vitro parameters evaluated in this study. The ranges of MIC values were 50 (EEP BA)-400 microg/ml (MG), for S. mutans; and 25 (BA)-400 microg/ml (MG), for S. sobrinus and S. cricetus. The bactericidal concentration of EEPs was four to eight times the MIC values. The adherence of S. mutans and S. sobrinus cells and WIG synthesis were markedly inhibited by EEPs, demonstrating significant inhibition at all concentrations compared with the control (80% ethanol) (p<0.05). EEP BA showed 80% inhibition of cell adherence and WIG synthesis at concentrations as low as 12.5 and 7.8 microg/ml, respectively. The results show that the new variety of propolis was exceptionally effective in all in vitro parameters tested against mutans streptococci; biological effects of propolis are likely not to be due solely to flavonoids and (hydroxy)cinnamic acid derivatives.

Animals↗

PubMed2000

In vitro antimicrobial activity of propolis and Arnica montana against oral pathogens.

Arnica and propolis have been used for thousands of years in folk medicine for several purposes. They possess several biological activities such as anti-inflammatory, antifungal, antiviral and tissue regenerative, among others. Although the antibacterial activity of propolis has already been demonstrated, very few studies have been done on bacteria of clinical relevance in dentistry. Also, the antimicrobial activity of Arnica has not been extensively investigated. Therefore the aim here was to evaluate in vitro the antimicrobial activity, inhibition of adherence of mutans streptococci and inhibition of formation of water-insoluble glucan by Arnica and propolis extracts. Arnica montana (10%, w/v) and propolis (10%, w/v) extracts from Minas Gerais State were compared with controls. Fifteen microorganisms were used as follows: Candida albicans--NTCC 3736, F72; Staphylococcus aureus--ATCC 25923; Enterococcus faecalis--ATCC 29212; Streptococcus sobrinus 6715; Strep. sanguis--ATCC 10556; Strep. cricetus--HS-6; Strep. mutans--Ingbritt 1600; Strep. mutans--OMZ 175; Actinomyces naeslundii--ATCC 12104, W 1053; Act. viscosus OMZ 105; Porphyromonas gingivalis; Porph. endodontalis and Prevotella denticola (the last three were clinical isolates). Antimicrobial activity was determined by the agar diffusion method and the zones of growth inhibition were measured. To assess cell adherence to a glass surface, the organisms were grown for 18 h at 37 degrees C in test-tubes at a 30 degree angle. To assay water-insoluble glucan formation, a mixture of crude glucosyltransferase and 0.125 M sucrose was incubated for 18 h at 37 degrees C in test-tubes at a 30 degree angle. Arnica and propolis extracts (20 microl) were added to these tubes to evaluate the % of inhibition of cell adherence and water-insoluble glucan formation. The propolis extract significantly inhibited all the microorganisms tested (p < 0.05), showing the largest inhibitory zone for Actinomyces spp. The Arnica extract did not demonstrate significant antimicrobial activity. Cell adherence and water-insoluble glucan formation were almost completely inhibited by the propolis extract at a final concentration of 400 microg/ml and 500 microg/ml, respectively. The Arnica extract showed slight inhibition of the adherence of the growing cells (19% for Strep. mutans and 15% for Strep. sobrinus) and of water-insoluble glucan formation (29%) at these same concentrations. Thus, the propolis extract showed in vitro antibacterial activity, inhibition of cell adherence and inhibition of water-insoluble glucan formation, while the Arnica extract was only slightly active in those three conditions.

Actinomyces↗

PubMed2000

Middle mediastinal lesions: imaging findings and pathologic correlation.

Lesions primarily involving the middle mediastinum are uncommon and include lymph node diseases, cystic lesions, neurogenic tumors, mesenchymal tumors, tumors of mediastinal organ, amd other benign processes. In this article, we illustrate imaging findings of a variety of middle mediastinal lesions with pathologic correlation.

Cysts↗

PubMed2000

Effect of saccharin on antibacterial activity of chlorhexidine gel.

Although chlorhexidine is the most effective agent against dental plaque it is extremely bitter. To prepare formulations, it is necessary to use flavoring and sweetening, which can inhibit the antibacterial effect of chlorhexidine. Saccharin has been considered a compatible substance to use in chlorhexidine rinse or gel preparations; however, the effect of a range of concentrations has not been studied. To evaluate the effect of different concentrations of saccharin on the antibacterial activity of chlorhexidine gel, hydroxy-ethyl-cellulose gels containing 1.0% chlorhexidine digluconate and 0.0 to 1.0% sodium saccharin were prepared. Activity against Streptococcus mutans was evaluated using the agar diffusion method and determination of MIC values. The inhibitory zones of growth were 7.83 +/- 0.54 mm when no saccharin was added to the chlorhexidine gel and 7.75 +/- 0.50, 7.63 +/- 0.48, 6.21 +/- 0.40, 4.13 +/- 0.38, when the concentrations of saccharin in the gels were 0.02, 0.10, 0.5, and 1.0%, respectively. The range of MIC values was 1-2 micrograms/ml, with saccharin concentrations of 0%, 0.02, and 0.1%. In contrast, the MIC values were 4-8 and 8-16 micrograms/ml with saccharin concentrations of 0.5% and 1.0%, respectively. The paired "t" test showed that 0.5 and 1.0% sodium saccharin inhibit the antibacterial activity of 1% digluconate chlorhexidine gel. These in vitro results suggest that saccharin may inhibit the efficacy of chlorhexidine against mutans streptococci, depending on the concentration.

Anti-Infective Agents, Local↗

PubMed1999

The effects of peripheral leukocytes on the hippocampal neuronal changes in transient global ischemia and unilateral cerebral hemispheric infarction.

The participation of activated leukocytes and subsequent production of chemical mediators has been well accepted in the pathophysiology of hypoxic-ischemic injury. This study was performed to see the effects of leukocytes on hippocampal neuronal damage in transient global ischemia induced by 10-min occlusion of bilateral common carotid arteries (CCAs) with reperfusion for various times, and in complete unilateral ischemia induced by 24-hr ligation of left CCA. Leukopenia was induced by intraperitoneal injection of cyclophosphamide for 4 days. The results showed that hippocampal neuronal damages were worse at 6-hr reperfusion in leukopenic experimental group than in the control group. In comparison, 24-hr and 3-day reperfusion leukopenic groups showed less numbers of damaged neurons and milder changes. The 5-day reperfusion group showed inconsistent changes. Unilateral CCA occlusion showed extensive infarction in 83.3% of gerbils in the control group, compared to 25% of gerbils in the experimental group (p<0.05). These results strongly suggest that the number of peripheral leukocytes were closely related to the development of delayed neuronal damage of hippocampus in transient global ischemia and the incidence of infarction induced by 24-hr unilateral CCA ligation.

Animals↗