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Biomedical subjects

M S Reddy

Publications and source records attributed to M S Reddy.

At least 37 records · Page 2Linked to original sources
PubMed2000

Diurnal regulation of plastid genes in Populus deltoides.

Light regulates leaf and chloroplast development, together with overall chloroplast gene expression at various levels. Plants respond to diurnal and seasonal changes in light by changing expression of photosynthesis genes and metabolism. In Populus deltoides, a deciduous tree species, leaf development begins in the month of March and leaf maturation is attained by summer, which is subsequently followed by autumnal senescence and fall. In the present study, diurnal changes in the steady state transcript levels of plastid genes were examined in the fully developed leaves during summer season. Our results show that steady state level of the psaA/B, psbA, psbEFLJ and petA transcripts showed differential accumulation during diurnal cycle in summer. However, there was no significant change in the pigment composition during the day/night cycle. Our studies suggest that the diurnal regulation of steady state mRNA accumulation may play a crucial role during daily adjustments in plants life with rapidly changing light irradiance and temperature.

Circadian Rhythm↗
PubMed1999

Guanine-rich telomeric sequences stimulate DNA polymerase activity in vitro.

Guanine-rich oligonucleotides and short telomeric DNA sequences can self-associate into G-quartet stabilized complexes. We discovered that this self-association can occur in sequencing reactions and that higher-order structures stimulate DNA polymerase to synthesize extended DNA strands. Base analogues were used to identify Hoogsteen base pairings as stabilizing forces in these stimulatory DNA structures. Scanning force microscopy confirmed that quartet-DNA was formed from these oligomers and that these extended, four-stranded structures could be bound by DNA polymerase. Since guanine quartet-stabilized structures are proposed to exist in vivo, such structures may stimulate DNA polymerization in vivo.

2-Aminopurine↗
PubMed1999

Radiographic determinants of implant performance.

This paper reviews and compares the strengths and weaknesses of radiographic techniques including periapical, occlusal, panoramic, direct digital, motion tomography, and computed tomography. Practical considerations for each method, including availability and accessibility, are discussed. To date, digital subtraction radiography is the most versatile and sensitive method for measuring boss loss. It can detect both bone height and bone mass changes on root-form or blade-form dental implants. Criteria for implant success have changed substantially over the past two decades. In clinical trials of dental implants, the outcomes require certain radiographic analyses to address the hypothesis or clinical question adequately. Radiographic methods best suited to the objective assessment of implant performance and hypothesis were reviewed.

Alveolar Bone Loss↗
PubMed1998

Synthesis and evaluation of analogues of the partial agonist 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC) and the full agonist 6-(benzyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (Zk 93423) at wild type and recombinant GABAA receptors.

A pharmacophore and an alignment rule have previously been reported for BzR agonist ligands. The design and synthesis of 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC, 24, IC50 = 8.1 nM) was based on this pharmacophore. When evaluated in vivo this ligand exhibited anticonvulsant/anxiolytic activity but was devoid of the muscle relaxant/ataxic effects of "classical" 1,4-benzodiazepines (i.e., diazepam). Significantly, 6-PBC 24 also reversed diazepam-induced muscle relaxation in mice. The 3-substituted analogues 40-46 and 48 of 6-PBC 24 and Zk 93423 27(IC50 = 1 nM) were synthesized and evaluated in vitro to determine what affect these modifications would have on the binding affinity at recombinant BzR subtypes. With the exception of the 3-amino ligands 40 and 41, all the beta-carbolines were found to exhibit high binding affinity at BzR sites. The 3-propyl ether derivative 45 was also evaluated in vivo and found to be devoid of any proconvulsant or anticonvulsant activity at doses up to 40 mg/kg. The 6-(1-naphthylmethyloxy) and 6-octyloxy analogues 25, 26, 28, and 29 of 6-PBC 24 were synthesized to further evaluate the proposed alignment of agonists vs inverse agonists in the pharmacophore of the BzR. In addition, ligands 26 and 29 were designed to probe the dimensions of lipophilic pocket L3 at the agonist site. The activity of 29 was evaluated in vivo; however, this analogue elicited no pharmacological effects at doses up to 80 mg/kg. These and other related beta-carbolines were also examined in five recombinant GABAA receptor subtypes. Ligands 52-61 all exhibited moderate to high affinity at GABAA receptors containing alpha1 subunits. These ligands will be useful in further defining the pharmacophore at alpha1 beta3 gamma2 receptors.

Animals↗
PubMed1998

Binding of the pili of Pseudomonas aeruginosa to a low-molecular-weight mucin and neutral cystatin of human submandibular-sublingual saliva.

In previous experiments, we have shown that [125I]pili of Pseudomonas aeruginosa exhibited specific binding to a low-molecular-weight mucin (MG2) of human submandibular-sublingual saliva (HSMSL; Reddy MS, Levine MJ, Paranchych W. Crit Rev Oral Biol Med 4:315-323, 1993). In the present study, I have utilized unlabeled pili and immunostaining to identify the receptor molecules in HSMSL. In addition to MG2, pili also bound to neutral cystatin (CsnSN). Binding of unlabeled pili to MG2 and CsnSN could be abolished by treatment of HSMSL with trypsin to hydrolyze the peptide moieties or N-acetylation to neutralize the positive charges of the lysine residues. Reductive methylation of HSMSL, which modifies the lysine residues to methyl lysines while retaining the positive charges, did not affect the binding of pili to either MG2 or CsnSN. Further, pili also exhibited binding to a recombinant MG2 peptide (aa 1-86). Collectively, the data suggested that a protein-to-protein interaction via electrostatic forces mediates the binding of the pili to MG2 and CsnSN. Iodination of pili, which modifies tyrosine-24 and/or -27 residues to O-iodotyrosine(s), abolished its binding to CsnSN but not to MG2. These results suggested that the conformation of pili also plays a role in interaction with CsnSN. Conformational change(s) of pili induced by iodination also made it susceptible to hydrolysis with trypsin.

Cystatins↗
PubMed1998

Semiautomated image registration for digital subtraction radiography.

OBJECTIVE: The purpose of this study was to evaluate the semiautomatic alignment and correction of affine geometric discrepancies for digital subtraction radiography. STUDY DESIGN: Algorithms were tested in vitro to determine their ability to semiautomatically select reference points on a second image based on points selected on a first (reference) image. A preserved human mandible was imaged with and without bone-equivalent material chips at varying degrees of angulation. Each chip had a mass of less than 10 mg and was no more than 0.3 mm thick. High levels of specificity and sensitivity for chip detection were achieved with 6 degrees of angular discrepancy or less. The algorithms were then applied to radiographs from six human subjects through use of the bone-chip validation model. RESULTS: Sensitivity was 89% and 100% for the three-point and four-point affine warp algorithms, respectively. Specificity for both algorithms was 100%. CONCLUSIONS: The data indicate that semiautomated alignment algorithms may enhance the efficacy of digital subtraction radiography while maintaining diagnostic efficacy in clinical trials.

Algorithms↗
PubMed1998

Structural features of the human salivary mucin, MUC7.

Human salivary mucin (MUC7) is characterized by a single polypeptide chain of 357 aa. Detailed analysis of the derived MUC7 peptide sequence reveals five distinct regions or domains: (1) an N-terminal basic, histatin-like domain which has a leucine-zipper segment, (2) a moderately glycosylated domain, (3) six heavily glycosylated tandem repeats each consisting of 23 aa, (4) another heavily glycosylated MUC1- and MUC2-like domain, and (5) a C-terminal leucine-zipper segment. Chemical analysis and semi-empirical prediction algorithms for O-glycosylation suggested that 86/105 (83%) Ser/Thr residues were O-glycosylated with the majority located in the tandem repeats. The high (approximately 25%) proline content of MUC7 including 19 diproline segments suggested the presence of polyproline type structures. CD studies of natural and synthetic diproline-rich peptides and glycopeptides indicated that polyproline type structures do play a significant role in the conformational dynamics of MUC7. In addition, crystal structure analysis of a synthetic diproline segment (Boc-Ala-Pro-OBzl) revealed a polyproline type II extended structure. Collectively, the data indicate that the polyproline type II structure, dispersed throughout the tandem repeats, may impart a stiffening of the backbone and could act in consort with the glycosylated segments to keep MUC7 in a semi-rigid, rod shaped conformation resembling a 'bottle-brush' model.

Amino Acid Sequence↗
PubMed1998

Coordinate production of PGE2 and IL-1 beta in the gingival crevicular fluid of adults with periodontitis: its relationship to alveolar bone loss and disruption by twice daily treatment with ketorolac tromethamine oral rinse.

The inflammatory mediators prostaglandin E2 (PGE2) and interleukin-1 beta (IL-1 beta) play critical roles in the inflammatory process leading to alveolar bone and connective tissue loss in periodontal disease. Data from a previously published 6-month clinical study demonstrated that twice daily use of 0.1% ketorolac tromethamine oral rinse prevented alveolar bone loss in adults with periodontitis. We further analyzed data from this study to examine the relationship between PGE2. IL-1 beta and bone loss. Patient mean PGE2 and IL-1 beta levels in gingival crevicular fluid (M-GCF) measured throughout the course of the study were directly compared to the maximum amount of alveolar bone height loss observed at a single study site in each patient. The maximum amount of bone loss measured was chosen for the analysis since the pattern of bone loss was clearly episodic in nature. A statistically significant correlation (r = 0.73, p = 0.001) exists between M-GCF PGE2 concentration and the maximum amount of bone height lost at individual patient study sites. The correlation between M-GCF IL-1 beta concentration and maximum bone height lost is also statistically significant (r = 0.66, p = 0.005). Over the 6-month duration of the study, both PGE2 and IL-1 beta were coordinately expressed in the placebo treatment group as reflected in the significant correlation between M-GCF concentrations of the 2 mediators (r = 0.81, p < 0.001). Treatment of patients with 0.1% ketorolac tromethamine twice daily for 6 months resulted in reductions of PGE2 in GCF and a negligible correlation between M-GCF PGE2 and M-GCF IL-1 beta (r = 0.42, p = 0.088). This lack of a strong association between the 2 mediators in the ketorolac treatment group provides a direct biochemical readout of the anti-inflammatory efficacy of ketorolac tromethamine oral rinse in patients with periodontitis. Further studies are warranted to determine the full diagnostic potential of M-GCF levels of PGE2 and IL-1 beta for predicting risk of alveolar bone loss in patients with periodontitis and monitoring periodontal therapy effectiveness.

Adult↗
PubMed1998

Periodontal healing of canine experimental grade-III furcation defects treated with autologous fibrinogen and absorbable barrier membrane.

OBJECTIVE: To determine the effects of autologous fibrinogen (AF) and absorbable barrier membrane (ABM) on periodontal healing of canine experimental grade-III furcation defects. ANIMALS: 18 conditioned, laboratory-source, adult Beagles. PROCEDURE: Defects were developed bilaterally at the second and fourth premolars and maintained for 12 weeks. Defects were treated with AF, ABM, AF and ABM, or debridement. Digital subtraction radiography, histologic evaluation, and histomorphometric analysis of defect healing was done at 1, 3, and 6 months after treatment to determine percentage increases in bone volume, height, area, and length of periodontal regeneration along the perimeter of the defect. RESULTS: Comparison of defects at post-treatment intervals indicated significantly greater healing of debridement and AF-treated defects, compared with ABM-treated defects at 3 months; however, by 6 months, there were no significant differences in defect healing for all histomorphometric variables. Defects treated with ABM were associated with significantly less root ankylosis than other treatments. Defects treated with debridement had significantly greater increases in bone volume at 6 months after treatment, compared with groups treated with ABM. There was a significant correlation between regenerated bone area, bone volume, and periodontal regeneration for all treatments at 3 and 6 months after treatment. CONCLUSION AND CLINICAL RELEVANCE: Use of AF and ABM did not enhance the amount of periodontal healing, compared with debridement only. The ABM-treated defects were essentially devoid of root ankylosis. Grade-III furcation defects may respond equally well to conservative periodontal surgery or guided tissue regenerative techniques. The prevention of root ankylosis is a substantial benefit favoring this latter method of treatment.

Absorption↗
PubMed1997

The microbial ecology and immunology of the adenoid: implications for otitis media.

The nasopharyngeal tonsil, or adenoid, is a major inductive site for the synthesis of J-chain-positive B cells that may migrate to other areas of the upper respiratory tract, such as the nasal mucosa, the parotid gland, the lacrimal gland, and the middle ear during inflammation. The production of secretory IgA by both the nasopharyngeal tonsil and the nasal mucosa plays a major role in local immune protection against bacteria and viruses. The release of cytokines from Th1 and Th2 lymphocytes must be appropriate for B cells to produce IgA. The factors or mechanisms responsible for this are not, at present, known, but it appears that there is a difference in the profiles of cytokine secretion by Th1 and Th2 lymphocytes in the adenoids in both otitis-prone, as well as nonotitis-prone children. We have suggested that if this specific immune system does not protect the host from invasion by potential pathogens, there are other modalities of therapy to protect the nasopharynx from colonization with pathogenic bacteria or viruses. These include the production of specific antibodies against bacterial surface proteins that have been identified as mucin-binding proteins. Alteration of the microbial flora with commensal organisms such as viridans streptococci can be utilized. These alpha-hemolytic streptococci probably function by producing an acid environment that prevents colonization of organisms such as nontypeable H. influenzae. Finally, the induction of specific SIgA by conserved outer membrane protein antigens of potential pathogens may be another strategy in the prevention of colonization of potential bacterial pathogens in the nasopharynx.

Adenoids↗
PubMed1997

Middle ear mucin glycoprotein: purification and interaction with nontypable Haemophilus influenzae and Moraxella catarrhalis.

Nontypable Haemophilus influenzae and Moraxella catarrhalis are important pathogens in children and adults. The mechanisms of their adherence to the epithelial cell surface and colonization are not clear. For the pathogen to adhere to the epithelial cell, it must first attach to and penetrate the mucus barrier. Mucin glycoproteins of the mucus layer generally are thought to be involved in bacterial attachment. To understand the precise mechanisms of middle ear mucin-bacterial interactions, we used an overlay binding assay with a highly purified middle ear mucin and outer membrane proteins of both nontypable H. influenzae and M. catarrhalis. Outer membrane proteins P2 and P5 were identified as the major components that medicate the binding between nontypable H. influenzae and human middle ear mucin. Moreover, the 57 kDa protein, CD, of the outer membrane protein of M. catarrhalis was found to be the only protein binding human middle ear mucin. Finally, it appears that a protein-oligosaccharide interaction is responsible for binding because asialo-mucin does not bind to either of the bacteria. Knowledge of the specific bacterial-mucin interaction may provide an understanding of the bacterial-epithelial cell colonization. Conversely, comprehension of this interaction between bacteria and purified mucin may be a strategy to prevent colonization of potential pathogens that cause otitis media and sinusitis in children.

Amino Acids↗
PubMed1997

Expression of chloroplastic genes during autumnal senescence in a deciduous tree Populus deltiodes.

In Populus deltoides, a deciduous tree, the development on new leaves starts in the month of March, the leaves reach maturity by October and fall by December. Changes in the composition and function of the photosynthetic apparatus were analysed during autumnal senescence. With the progress of senescence, there was an initial increase followed by a decrease in the steady state levels of psbA, psbD/C and psaA/B gene transcripts. Decrease in the steady state level of D1 protein was faster than that of Cytochrome f. The decline in LHCP level was seen only during late senescence. Although the leaves continue to look green and healthy till late November, the electron transport driven by individual photosystems started declining by October end suggesting the onset of senescence.

Blotting, Northern↗
PubMed1997

A comparison of manual and controlled-force attachment-level measurements.

This study compared the intra-examiner and inter-examiner error of 2 constant force probes to the reading of a conventional manual probe. 3 examiners made repeated examinations of attachment level using a modified Florida probe and a manual North Carolina probe (read to 1 mm or 0.5 mm); relative attachment level measurements were made using a Florida disk probe. One probe was used in each quadrant in 8 subjects with moderate to advanced periodontitis. Error was calculated as the mean of the absolute value of the difference between each examination, and the correlation between values at each examination calculated. Statistically-significant differences between probe type, examiners, and sites were detected using a repeated measures ANOVA accounting for the nesting within subjects. There was a significant difference in error by probe type (modified Florida probe 0.62 +/- 0.03 mm, r = 0.86; Florida stent probe 0.55 +/- 0.05 mm, r = 0.82; manual probe to 1 mm 0.39 +/- 0.02 mm, r = 0.88; manual probe to 0.5 mm 0.40 +/- 0.02 mm, r = 0.89; (p < 0.001). Significant differences were observed by examiners (p < 0.01). These data indicate that both manual and controlled-force probes can provide measurement within less than 1 mm of error; however, individual calibration of examiners remains important in the reduction of error.

Alveolar Bone Loss↗
PubMed1997

The use of periodontal probes and radiographs in clinical trials of diagnostic tests.

Periodontal probing attachment level measurements and intraoral radiographs are used to assess the level of the clinical attachment and bone support in the diagnosis of periodontitis. Together these physical measurements of tooth support comprise the standard against which new diagnostic tests are compared. Since probing and radiographs provide a measure of the severity of attachment or bone loss at one point in time, serial measurements must be compared to determine whether periodontitis is progressive. Periodontal probing may be performed manually or by using controlled force electronic instruments. The resolution, depending on the instrument, will vary from 1.0 mm to 0.1 mm. Variations in probing force, size and shape of tip, location of tip placement, detection or reference landmarks for attachment level probing, degree of gingival inflammation, and transcription may adversely influence accuracy. Electronic probes offer the advantage of improved resolution, force control, and automatic recording, but the literature is inconsistent about the advantages in terms of repeatability and accuracy. Radiographic assessment of alveolar bone loss may be achieved by visual interpretation, measurement, or digital image analysis. While visual interpretation of unstandardized radiographs is insensitive to changes in bone, standardized radiographs can permit measurement of changes on the order of 0.2 mm when computerized methods are used. Newer techniques such as digital subtraction radiography permit detection of bony changes too small to be seen by the unaided eye and are over 95% sensitive and specific in detecting bony changes less than 10 mg.

Alveolar Bone Loss↗
PubMed1996

Role of type 1 fimbriae in the adhesion of Escherichia coli to salivary mucin and secretory immunoglobulin A.

Saliva is known to modulate the adhesion of bacteria in the oral cavity. The present work was performed to assess the effect of salivary components on the adhesion of Escherichia coli to a model oral surface. Several genetically engineered E. coli strains were used to examine the role of type 1 fimbriation in the interaction of these strains with salivary components in solution or adsorbed to hydroxyapatite. High (MG1) and low (MG2) molecular weight salivary mucins, and secretory immunoglobulin A (sIgA), were found to interact with the surface of E. coli, and these interactions were independent of the expression of fimbriae or capsule. In contrast, fimbriated strains of E. coli adhered to a greater extent to saliva-coated synthetic hydroxyapatite (HAP) than did nonfimbriated strains. Testing of salivary components separated by gel filtration chromatography revealed that only high-molecular-weight components promoted adhesion of E. coli to HAP. Additional studies found that purified MG2 and sIgA promoted the adhesion of E. coli to HAP. Expression of type 1 fimbriae enhanced adhesion, while mannose inhibited adhesion of fimbriated strains, to saliva-coated HAP and to HAP coated with MG2 and sIgA. We conclude that salivary MG2 and sIgA may provide receptors for the adhesion of type 1 fimbriated E. coli to oral surfaces.

Bacterial Adhesion↗
PubMed1996

Binding between Pseudomonas aeruginosa adhesins and human salivary, tracheobronchial and nasopharyngeal mucins.

Endogenous aspiration of nasooropharyngeal secretions is a major source of Pseudomonas aeruginosa to lungs. To understand the mechanism of binding between P. aeruginosa and nasooropharyngeal secretions, we have utilized an overlay binding assay employing P. aeruginosa nonpilus protein adhesins (18 kDa and 15 kDa) and mucins from human saliva, tracheobronchial and nasopharyngeal secretions. Nasopharyngeal mucin bound to both the 18 kDa and 15 kDa adhesins. A high molecular weight salivary mucin and tracheobronchial mucin bound only to the 18 kDa adhesin. On the other hand, asialonasopharyngeal and asialotracheobronchial mucins did not bind to either of the adhesins. Binding of nasopharyngeal mucin to the 18 kDa and 15 kDa was not inhibitable by glycoproteins, bovine submaxillary mucins and sialic acid. Further, a low molecular weight salivary mucin which contains sialylated oligosaccharides also did not bind to either of the adhesins. Collectively, the results suggest that binding between P. aeruginosa and mucins may involve specific receptors and adhesins.

Adhesins, Bacterial↗