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Biomedical subjects

M S Reddy

Publications and source records attributed to M S Reddy.

At least 73 records · Page 4Linked to original sources
PubMed1993

Sialochemistry: a diagnostic tool?

Saliva has proven to be a discriminating element in forensic arenas, an effective indicator of acute diseases of salivary glands, and a promising probe for drug monitoring. With the advent of sensitive immunochemical assays, the compositional profile of human salivary secretions has been expanded considerably. Thus, the establishment of a range of "normal values" for a variety of "intrinsic" and "extrinsic" salivary components represented the initial step to use saliva as a diagnostic tool of oral health status. Unfortunately, numerous cross-sectional studies have shown a wide individual variation in the salivary composition of healthy populations, thus precluding its use as a diagnostic chair-side test for the screening of the most common chronic oral diseases (e.g. caries and periodontal disease). A possible explanation may arise from the wide functional versatility of salivary molecules. For instance, it has been recognized recently that in addition to its digestive properties, salivary amylase may modulate bacterial colonization, whereas histatins are not only antifungal but also bactericidal. Thus, low levels of already known antimicrobial salivary molecules (e.g., secretory IgA, lactoferrin, and lysozyme) could be compensated with higher concentrations of other molecules with antimicrobial activity, such as amylase and histatins. Consequently, for caries and periodontal diseases, longitudinal sialochemical studies may yield more insight than cross-sectional studies.

Aged↗
PubMed1993

Digital subtraction radiography.

Subtraction radiography offers greater visualization of radiographic changes between a pair of radiographs by subtracting out the unchanging background distractions. Originally, subtraction was achieved by using positive and negative prints in angiography. The advent of digital imaging devices has led to validation of quantitative measurements from digital subtraction images. As well, computer software manipulations have allowed for more flexibility in the clinical application of subtraction imaging. The clinical application of digital subtraction radiography is discussed along with clinical cases.

Humans↗
PubMed1993

Periodontal disease progression.

The progression of periodontitis has been an area of active research during the past year. Prevalence and disease severity studies indicate that severe periodontitis remains a problem of considerable magnitude. The standard for evaluation of periodontitis progression is sequential attachment and bone-level measurements. A vast number of approaches to identify indicators of periodontal disease activity are under development. These include methods to detect bacterial infection or the breakdown of the periodontium. The number of proposed models of periodontal progression has expanded along with the identification of risk factors at the site, subject, and population levels. No model currently under consideration is predictive of future periodontal disease progression.

Age Factors↗
PubMed1992

Structural features of the low-molecular-mass human salivary mucin.

The low-molecular-mass human salivary mucin has at least two isoforms, MG2a and MG2b, that differ primarily in their sialic acid and fucose content. In this study, we characterize further these isoforms, particularly their peptide moieties. Trypsin digests of MG2a and MG2b yielded high- and low-molecular-mass glycopeptides following gel filtration on Sephacryl S-300. The larger glycopeptides from MG2a and MG2b had similar amino acid compositions and identical N-terminal sequences, suggesting common structural features between their peptides. An oligonucleotide probe generated from the amino acid sequence of the smaller glycopeptide from MG2a was employed in Northern-blot analysis. This probe specifically hybridized to two mRNA species from human submandibular and sublingual glands. A cDNA clone selected from a human submandibular gland cDNA expression library with antibody generated against deglycosylated MG2a also hybridized to these two mRNA species. In both cases, the larger mRNA was polydisperse, and the hybridization signal was more intense in the sublingual gland. In addition, the N-terminal amino acid sequence of the larger glycopeptide was found to be part of one of the selected MG2 cDNA clones.

Amino Acid Sequence↗
PubMed1992

Quantitative digital subtraction radiography for the assessment of peri-implant bone change.

The purpose of this study was to develop a digital subtraction technique to assess peri-implant bone change. The method uses subtraction radiography to enhance visualization of the area of change that has occurred between radiographic examinations, and superimposes the area of change on the original radiographs. Furthermore, a reference wedge allows calculation of the mass of the lesion. The method was validated using 21 small bony chips placed on 3 different skulls prior to the first radiograph. The chips were removed, a second radiograph taken, and the images subtracted. A morphologic method was used to isolate the lesion and the change in bone mass calculated. Overall, there was excellent correlation between the calculated lesion mass (mg) and actual lesion mass (r2 > 0.90). The utility of the method was demonstrated using a case that experienced implant failure. These data indicate that quantitative digital subtraction radiography may be of value in measuring peri-implant bone change in root form implants.

Alveolar Bone Loss↗
PubMed1992

A semi-automated computer-assisted method for measuring bone loss adjacent to dental implants.

The purpose of this study was to develop a repeatable method for measurement of bone support around root form and blade implants suitable for use in high-quality but unstandardized radiographs. 10 phantoms were fabricated to simulate progressive osseous defects around implants. Radiographs were taken in triplicate and digitized. Specialized software was written which placed a grid of known dimensions over the implant so that the top and the bottom of the grid were at the neck and the base of the implant, respectively. The investigators selected the edge of the bone at each point where the grid intersected the implant and the software automatically detected the implant edge. The software also outlined and displayed the defect on the computer monitor. Measurements were performed 5 times and the standard deviation was taken as a measure of the repeatability of the method. Repeatability for blades and root forms was 0.19 +/- 0.07 mm and 0.08 +/- 0.03 mm, respectively. There was no significant difference in the ability to measure bone loss in the blade versus the root form (p = 0.17, NS). These results indicate that this semi-automated computer-assisted method for measuring bone loss around implants is repeatable and may be of value for clinical trials using either root form or blade implants.

Alveolar Bone Loss↗
PubMed1992

Human tracheobronchial mucin: purification and binding to Pseudomonas aeruginosa.

Colonization of the respiratory tract with Pseudomonas aeruginosa is a serious problem in cystic fibrosis and seriously ill hospitalized patients. Human tracheobronchial mucin (HTBM), the major glycoprotein of human tracheobronchial secretions, is known to interact with this pathogen, which may then be cleared by mucociliary action. However, the mechanism of interaction is not known. To understand this process, pure HTBM was isolated from tracheobronchial secretions of a laryngectomee. Following initial fractionation on Sepharose CL-2B, the HTBM-containing fraction was subjected to reductive methylation and then gel filtration. Pure HTBM was employed in an overlay binding assay to identify the bacterial adhesin(s) and mucin receptors that participate in mucin-P. aeruginosa interactions. An approximately 16-kDa nonpilus protein component(s) of P. aeruginosa was found to be the adhesin(s) for HTBM. The mucin receptor for the 16-kDa component(s) was found in the peptide moiety. This study confirms that P. aeruginosa utilizes the nonpilus adhesin(s) to bind to HTBM. Identification of the specificity of the HTBM-P. aeruginosa interactions can lead to a better understanding of the predominance of P. aeruginosa colonization in individuals with cystic fibrosis.

Aged↗
PubMed1992

Radiographic methods in the evaluation of periodontal therapy.

Radiographic methods are commonly utilized to assess periodontal bone changes in clinical trials. Radiographs are unique as a data source in that they provide a permanent visual record of the bone support and allow for linear, area, and volume measurements of periodontal lesions. The major limiting factors in the use of radiographic outcomes measures are geometric distortion and radiographic processing errors. The use of standardized methods and computer algorithms has reduced the effect of these errors on data from radiographs. Radiographic analysis in clinical trials is largely done in digital format by indirect digitizing film with a video camera. Direct digital detectors are now available for intra-oral use. The use of a direct detector eliminates the need for film processing and allows for dose reduction. The detectors currently available are limited in size and resolution. Subtraction radiography allows for area and volume estimates of bone gain or loss. The subtraction methods are highly precise, but are also technically exacting and labor intensive. The clinical trial hypothesis, size, length, and accuracy required should be the final consideration in choosing a radiographic method.

Alveolar Bone Loss↗
PubMed1992

Digital subtraction radiography for the assessment of bone changes in rheumatoid arthritis.

A digital subtraction radiography (DSR) method was developed to assess changes of bony erosions in the hands of patients with rheumatoid arthritis (RA). The method initially was validated in vitro using simulated lesions in cadaver hands. The sensitivity, specificity and accuracy in detecting simulated lesions were 84.6, 100, and 92.3%, respectively. This technique was then pilot tested clinically using 17 patients with RA and 5 controls with no arthritis. All subjects received the nonsteroidal antiinflammatory drug, flurbiprofen, during the 6-month study period. No progressive changes in bone were observed in the control group; however, 18% of the target joints studied in the group with RA showed significant erosive changes (positive or negative) which correlated with the clinical assessment. The results indicate that DSR may be useful in detecting small changes in erosions on hand/wrist radiographs of patients with RA.

Adult↗
PubMed1991

Large-scale purification and characterization of the major phosphoproteins and mucins of human submandibular-sublingual saliva.

The major components of human submandibular-sublingual saliva (HSMSL) are mucins, amylases, cystatins, proline-rich proteins and statherin. Structure-function studies of these molecules have been hampered by the small amounts of purified materials that can be isolated from human secretions. The present study describes an integrated purification protocol for the large-scale preparation of many of these molecules. To dissociate partially heterotypic complexes among salivary molecules, HSMSL was initially fractionated into four pools by gel filtration with 6 M-guanidine hydrochloride. Subsequent fractionation of these four pools by gel-filtration and ion-exchange chromatography resulted in the purification of high- and low-Mr mucins, neutral and acidic cystatins, acidic and basic proline-rich proteins and statherin. Many variants or isoforms of these salivary molecules have been identified and biochemically characterized. Biochemical studies indicated that the low-Mr mucin exists as two isoforms which vary in their sialic acid to fucose ratios. Three isoforms of acidic cystatin S were characterized which differ in their phosphate content. Two isoforms of a basic proline-rich peptide were identified; the smaller peptide was a truncated form missing the first seven amino acids.

Adult↗
PubMed1991

Immunochemistry and immunogenicity of low molecular weight human salivary mucin.

The purposes of this study were to examine the immunogenicity of the low molecular weight human salivary mucin (MG2) and determine its distribution within major and minor human salivary glands. Anti-MG2 sera were produced in Balb/c mice by a variety of immunization schedules. Chromatographically or electrophoretically purified MG2 and partially purified mucin chromatographic fractions exposed to mild denaturing conditions were not immunogenic. Only MG2 without prior exposure to urea or guanidine was able to elicit an immune response. A murine anti-MG2 monoclonal antibody (clone 1/F9) was produced and its monospecificity confirmed by immuno-dot blotting and SDS-PAGE Western transfer. Clone 1/F9 (IgG1; kappa) was of moderate affinity and was directed to a Pronase- and TPCK trypsin-sensitive but periodate-resistant epitope which was not blood group- or sialic acid-specific. Immunocytochemical studies of frozen tissue sections with clone 1/F9 using both indirect and direct methods revealed that MG2 was more heterogeneously distributed within submandibular than labial glands and was not found in parotid or palatine glands. The use of a polyclonal rabbit anti-MG2 reagent in either frozen or paraffin-embedded tissues gave the same immunocytochemical results as those obtained with the monoclonal antibody.

Adult↗
PubMed1991

Contrast enhancement as an aid to interpretation in digital subtraction radiography.

An initial study was performed to demonstrate the feasibility of pseudocolor contrast enhancement technique in digital subtraction radiography (DSR). DSR is an electronic image processing technique that has been shown to be of greater diagnostic value in the detection of small periodontal bone lesions than conventional radiography. Pseudocolor enhancement involves selectively assigning a unique color to each shade of gray present in a black-and-white subtracted image. Two image enhancement techniques were developed and tested in a phantom system consisting of extracted teeth set in blocks of plaster mixed with sawdust to simulate trabecular bone. It was found that experimentally induced periodontal lesions were more readily detected by the average clinician in both types of enhanced subtraction images than unenhanced subtractions. Furthermore, both enhancement techniques were of significantly greater diagnostic value for lesions smaller than 1.0 mm (p less than 0.001). The technique that colored an isolated area of interest was significantly more diagnostic at all depths tested (p less than 0.001 at 0.5 and 1.0 mm, and p less than 0.05 at 0.5 mm). Contrast enhancement may be a significant aid to the average clinician for the interpretation of DSR and the detection of small periodontal defects.

Chi-Square Distribution↗
PubMed1991

Inhibition of alveolar bone loss in beagles with the NSAID naproxen.

The non-steroidal anti-inflammatory drug(NSAID) naproxen was studied in 11 beagle dogs over a 13-month period to determine its effect on the progression of periodontitis. Following a 6-month pretreatment period, 5 dogs received naproxen daily at a dosage of 2.0 mg/kg for 1 month, then 0.2 mg/kg for 6 months. Six control dogs received a gelatin capsule daily as placebo. Standardized radiographs were used to measure the rate of bone loss during the pretreatment and treatment periods. In the control dogs, the rate of bone loss was seen to increase during the treatment period although the increase was not statistically significant. In dogs treated daily with naproxen, the rate of bone loss in the treatment period was significantly less at 4 months of treatment; however, at 7 months the difference, though lower than pretreatment rate, was not significant. When the percent change in rate of bone loss during the overall 7-month treatment period was compared with pretreatment rate, the control dogs demonstrated a 38% increase in rate of bone loss during the treatment period contrasting with a 61% decrease in bone loss rate in naproxen-treated dogs. The data indicate that the non-steroidal anti-inflammatory drug naproxen can significantly inhibit alveolar bone loss in beagles. At 4 months of treatment the rate of bone loss in the naproxen-treated dogs was significantly less than pretreatment, but at 7 months of treatment the rate was no longer statistically significantly less than baseline. This probably reflects a dose response to naproxen treatment for, after 30 days of the treatment period, the naproxen dosage was reduced 10-fold due to tolerance by the beagle.

Alveolar Bone Loss↗
PubMed1991

Interaction of a salivary mucin-secretory immunoglobulin A complex with mucosal pathogens.

This study examined the interaction of a human salivary low-molecular-weight mucin (MG2) with Staphylococcus aureus and Pseudomonas aeruginosa by using both solution-phase and solid-phase assays. In solution phase, MG2 in human submandibular-sublingual saliva (HSMSL) bound to the bacterial surface; however, the highly purified mucin isoforms (MG2a and MG2b) did not. Mucin binding appeared to be dependent on heterotypic complexing between MG2 and secretory immunoglobulin A (IgA), although other salivary molecules may also be involved. In contrast, in a solid-phase assay in which HSMSL, MG2-containing fractions with secretory IgA, and purified MG2 were immobilized onto a solid surface, there was minimal adherence of S. aureus. The collective results suggest that mucin binding to S. aureus and P. aeruginosa may be predicated on the formation of an MG2-secretory IgA complex. Such interactions may facilitate microbial clearance from the oral cavity and play an important role in preventing colonization of the oral cavity and the respiratory tract by potential pathogens.

Bacterial Adhesion↗
PubMed1991

Detection of periodontal disease activity with a scintillation camera.

The goal of this study was to assess the ability of a scintillation camera method to detect areas of active bone loss due to periodontitis. Technetium 99m methylene diphosphonate was used as the bone-seeking radiopharmaceutical. Bone-seeking radiopharmaceutical uptake (BSRU) was imaged and quantified in alveolar bone regions of interest with a scintillation camera and a computer. Analysis of the sequential radiographs over six months constituted the basis for determination of sites of active disease. The study was composed of two parts. First, 18 subjects, nine with adult periodontitis and nine controls, were enrolled in a cross-sectional study to determine whether the quantitative scintillation amera methodology detected differences in BSRU in periodontitis vs. periodontally healthy patients. Second, the nine patients with periodontitis were studied longitudinally in order to determine whether the BSRU examination was indicative of bone loss subsequently measured radiographically. In the cross-sectional study, the mean uptake ratio for the periodontitis group was significantly higher than that for the control group (1.63 +/- 0.06 and 1.42 +/- 0.04, respectively, p less than 0.01, t test). From the longitudinal study, the mean patient scintillation image uptake ratios were highly correlated with the mean bone loss determined from serial radiographs (p less than 0.01). The accuracy, sensitivity, and specificity of the quantitative gamma camera method for detecting site(s) of active bone loss within the region of interest were assessed relative to the longitudinal radiographic data. The accuracy, sensitivity, and specificity were 85%, 90%, and 79%, respectively. Alveolar bone scintigraphy with a gamma camera and computer may provide a simple and valid technique for the immediate indication of areas of periodontal disease activity.

Adult↗