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Biomedical subjects

M Peleg

Publications and source records attributed to M Peleg.

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

On estimating the probability of aperiodic outbursts of microbial populations from their fluctuating counts.

The irregular sequence of counts of a microbial population, in the absence of observable corresponding environmental changes (e.g., temperature), can be regarded as reflecting the interplay of several unknown or random factors that favor or inhibit growth. Since these factors tend to balance one another, the fluctuations usually remain within bounds, and only by a coincidence--when all or most act in unison--does an 'outburst' occur. This situation can be represented mathematically as a sequence of independent random variables governed by a probability distribution. The concept was applied to reported microbial counts of ground meat and wastewater. It is found that the lognormal distribution could serve as a model, and that simulations from this model are indistinguishable from actual records. The parameters of the lognormal (or other) distribution can then be used to estimate the probability of a population outburst, i.e., an increase above a given threshold. Direct estimation of the outburst probability based on frequency of occurrence is also possible, but in some situations requires an impractically large number of observations. We compare the efficiency of these two methods of estimation. Such methods enable translation of irregular records of microbial counts into actual probabilities of an outburst of a given magnitude. Thus, if the environment remains 'stable' or in dynamic equilibrium, the fluctuations should not be regarded merely as noise, but as a source of information and an indicator of potential population outbursts even where obvious signs do not exist.

Animals↗
PubMed2000

Pain in the neck after neck dissection.

BACKGROUND: Reports of disability after neck dissection have been directed toward shoulder dysfunction and pain. We could find no report addressing the issue of pain localized to the actual operative site. We have conducted a combined prospective and retrospective study of pain in patients undergoing neck dissection. METHODS: Eighty-eight disease-free patients were evaluated in 3 groups for neck pain. One group was followed up prospectively for 1 to 8 months after surgery, and 2 retrospective groups were followed up for more than 2 years or for 6 months to 2 years. Pain was assessed by a body map and visual analog scale. RESULTS: None of 31 patients followed up for more than 2 years reported neck pain. Four of 27 patients followed up for 6 to 24 months had pain, with a mean visual analog scale score of 3.7. Seventy percent of the prospective group of 30 patients had pain during the first postoperative week, and only 1 patient had pain persisting for more than 2 months. Shoulder pain and disability after radical neck dissection were encountered in all groups, comparable with the incidence reported in the literature. No postoperative neuromas were found. CONCLUSIONS: Chronic pain localized to the operative site is an uncommon occurrence even after radical neck dissection. Chronic pain in the shoulder region may follow radical neck dissection, whereas modified neck dissection is usually a painless procedure.

Adult↗
PubMed2000

Modeling microbial survival during exposure to a lethal agent with varying intensity.

Traditionally, the efficacy of preservation and disinfection processes has been assessed on the basis of the assumption that microbial mortality follows a first-order kinetic. However, as departures from this assumed kinetics are quite common, various other models, based on higher-order kinetics or population balance, have also been proposed. The database for either type of models is a set of survival curves of the targeted organism or spores determined under constant conditions, that is, constant temperature, chemical agent concentration, etc. Hence, to calculate the outcome of an actual industrial process, where conditions are changing, as in heating and cooling during a thermal treatment or when the agent dissipates as in chlorination or hydrogen peroxide application, one has to integrate the momentary effects of the lethal agent. This involves mathematical models based on assumed mortality kinetics, and simulated or measured history, for example, temperature-time or concentration-time relationships at the "coldest" point. It is shown that the survival curve under conditions where the agent intensity increases, decreases, or oscillates can be constructed without assuming any mortality kinetics and without the use of the traditional D and Z values, which require linear approximation, and without thermal death times, which require extrapolation. The actual survival curves can be compiled from the isothermal survival curves provided that growth and damage repair do not occur over the pertinent time scale and that the mortality rate is a function of only the momentary agent intensity and of the organism's or spore's survival fraction (but not of the rate at which this fraction has been reached). The calculation is greatly facilitated if both the "isothermal" survival curves and the time-dependent agent intensity can be expressed algebraically. The differential equation derived from these considerations can be solved numerically to produce the required survival curve under the changing conditions. The concept is demonstrated with simulated survival curves during heating at different rates, heating and cooling cycles, oscillating temperature, and exposure to a dissipating chemical agent. The simulated thermal processes are based on published data of Clostridium botulinum spores, whose semilogarithmic survival curves have upward concavity and on a hypothetical "Listeria-like" organism whose semilogarithmic curves have downward concavity.

Clostridium botulinum↗
PubMed2000

The use of hydroxyapatite bone cement for sinus floor augmentation with simultaneous implant placement in the atrophic maxilla. A report of 10 cases.

BACKGROUND: Dental implant placement associated with sinus floor augmentation in a severely atrophic maxilla can be performed in a 1- or 2-stage surgical procedure, depending on the height of the residual alveolar bone. A minimum of 4 to 5 mm is recommended for a 1-stage procedure. METHODS: This clinical study describes the use of hydroxyapatite (HA) bone cement to stabilize HA-coated cylindrical implants placed simultaneously during sinus augmentation in 100 patients where insufficient bone volume did not allow primary implant stability. A total of 26 HA-coated dental implants were inserted in 100 grafted sinuses of 10 patients. RESULTS: None of the cases presented any difficulty in achieving initial stabilization and parallelism. No clinical complications of the sinuses were evident. Prior to exposure, radiographic evaluation revealed the implants embedded in a densely homogeneous radiopaque mass. At second-stage surgery, there was no clinical evidence of crestal bone loss around the implants. All implants were clinically osseointegrated. All patients received fixed implant-supported prostheses. Mean follow-up was 18 months (range 12 to 24 months). CONCLUSIONS: According to this preliminary study, the hydroxyapatite bone cement appears to hold great promise as a grafting alloplastic material for sinus floor augmentations. Its main advantage is its ability to provide initial stability required for osseointegration and proper implant location and parallelism. Further clinical and histological studies are required before it can be recommended for routine use in sinus lift procedures.

Adult↗
PubMed2000

Estimating the survival of Clostridium botulinum spores during heat treatments.

A recently published study of the inactivation of Clostridium botulinum spores at various temperatures in the range of 101 to 121 degrees C and neutral pH revealed that their semilogarithmic survival curves all had considerable upward concavity. This finding indicated that heat inactivation of the spores under these conditions did not follow a first-order kinetics and that meaningful D values could not be calculated. The individual survival curves could be described by the cumulative form of the Weibull distribution, i.e., by log S = -b(T)t(n(T)), where S is the survival ratio and b(T) and n(T) are temperature-dependent coefficients. The fact that at all temperatures in the above range n(T) was smaller than 1 suggested that as time increases sensitive members of the population parish and survivors with increasing resistance remain. If damage accumulation is not a main factor, and the inactivation is path independent, then survival curves under monotonously increasing temperature can be constructed using a relatively simple model, which can be used to calculate the spores' survival in a limiting case. This is demonstrated with computer-simulated heating curves and the experimental constants of the C. botulinum spores, setting the number of decades reduction to 8, 10, and 12 (the current criterion for commercial sterility).

Clostridium botulinum↗
PubMed2000

Analysis of the fluctuating microbial counts in commercial raw milk--a case study.

Microbial counts of raw milk from eight commercial dairy farms recorded over a period of about 2 years were obtained from a processing plant. All the counts formed irregular fluctuating series whose statistical properties were examined. In all eight cases the autocorrelation function indicated that the counts were random and had no underlying periodicity. This suggested that the fluctuations, at least to some extent, reflected the combined effect of numerous factors, some unknown, and that these factors operate randomly and independently. In five out of the eight cases the fluctuating pattern of the record could be described by a probabilistic model based on the assumption that the counts have a lognormal distribution. The validity of the model was confirmed by comparing the calculated frequencies of counts exceeding preselected levels with those actually observed in fresh data. The model enabled ranking the five sources on the basis of anticipated frequencies of excessive counts rather than on the basis of mean performance. Two sequences had clearly identified regions with different statistical characteristics. They were interpreted as a reflection of changes in the sanitary conditions at the corresponding farms. In one case, both the overall magnitudes and the fluctuation amplitude of the counts progressively decreased, a situation for which the described model as formulated was inapplicable.

Animals↗
PubMed2000

Guideline classification to assist modeling, authoring, implementation and retrieval.

The National Guideline Clearinghouse (NGC) and its guideline classification system are significant contributions to the study of clinical practice guidelines (CPGs) and their incorporation into routine clinical care. The NGC classification system is primarily designed to support guideline retrieval. We believe that a guideline classification system should also support identification of features that relate to incorporation of executable CPGs into computer-based applications for sharing and delivering guideline-based advice. We have developed a proposed expansion of the NGC guideline classification for this purpose. The axes of the proposed scheme have implications for designing formal models and structures for representing and authoring CPGs. This scheme also has implications for future research.

Classification↗
PubMed2000

GLIF3: the evolution of a guideline representation format.

The Guideline Interchange Format (GLIF) is a language for structured representation of guidelines. It was developed to facilitate sharing clinical guidelines. GLIF version 2 enabled modeling a guideline as a flowchart of structured steps, representing clinical actions and decisions. However, the attributes of structured constructs were defined as text strings that could not be parsed, and such guidelines could not be used for computer-based execution that requires automatic inference. GLIF3 is a new version of GLIF designed to support computer-based execution. GLIF3 builds upon the framework set by GLIF2 but augments it by introducing several new constructs and extending GLIF2 constructs to allow a more formal definition of decision criteria, action specifications and patient data. GLIF3 enables guideline encoding at three levels: a conceptual flowchart, a computable specification that can be verified for logical consistency and completeness, and an implementable specification that can be incorporated into particular institutional information systems.

Decision Support Techniques↗
PubMed1999

DOAS measurements of tropospheric bromine oxide in mid-latitudes

Episodes of elevated bromine oxide (BrO) concentration are known to occur at high latitudes in the Arctic boundary layer and to lead to catalytic destruction of ozone at those latitudes; these events have not been observed at lower latitudes. With the use of differential optical absorption spectroscopy (DOAS), locally high BrO concentrations were observed at mid-latitudes at the Dead Sea, Israel, during spring 1997. Mixing ratios peaked daily at around 80 parts per trillion around noon and were correlated with low boundary-layer ozone mixing ratios.

Journal Article↗
PubMed1999

Lingual cyst with respiratory epithelium: an entity of debatable histogenesis.

PURPOSE: The purpose of this report was to describe a new case of lingual cyst with respiratory epithelium, to review and analyze the literature regarding lingual cyst of foregut origin and lingual alimentary cyst, and to discuss the suitable terminology for these uncommon cysts. MATERIAL AND METHODS: Data from articles published in the English language between the years 1942 and 1947 were used. RESULTS: The review of the literature showed 53 lingual cysts of which 29 could be grouped into lingual alimentary tract cysts and 24 into lingual cysts of foregut origin. There was an overlap in histologic and clinical features and embryogenesis of both cysts. CONCLUSIONS: Differentiation between both cysts cannot be supported, and until further information is accumulated it is suggested that histologic descriptive terms be used such as lingual cyst with respiratory epithelium, lingual cyst with gastric epithelium, or lingual cyst with respiratory and gastric epithelium.

Child↗
PubMed1999

On modeling the irregular fluctuations in microbial counts.

Daily or other periodic microbial counts in many foods, particularly ground meats, poultry, and raw milk, show an irregular fluctuating pattern. The cause of the fluctuations is the interplay of many random factors that tend to promote or inhibit microbial growth. Therefore, the actual size of a microbial population can vary randomly around a typical level or around a trend determined, for example, by seasonal variations or changing sanitary conditions. Fluctuations around a fixed level can often be modeled as a sequence of independent counts having a lognormal or other parametric distribution. The independence of the counts and the type of distribution can be established by standard statistical tests. Once selected, the distribution function can be used to estimate the probability of encountering a population in any given size range. The model can be modified to describe sequences that include zero counts, which are the result of the organisms' absence, or of the failure of the method to detect them. In the case of fluctuations around a trend, a modified version of the model can be used to estimate the probability of deviations from the trend. A more thorough modification is required in order to account for fluctuating patterns that include outbursts of appreciable duration, like those caused by massive contamination of a water reservoir.

Animals↗
PubMed1999

Immediate placement of implants in extraction sites of maxillary impacted canines.

BACKGROUND: Treatment of asymptomatic impacted maxillary canines in adults is inevitable when primary canine becomes lost through extraction or exfoliation or when the impacted tooth becomes symptomatic. Treatment alternatives include an orthodontic procedure to bring the unerupted tooth to the dental arch or prosthetic replacement of the missing tooth. The authors describe an alternative treatment that involves immediate placement of implants into extraction sockets of the teeth. CASE DESCRIPTION: A patient with bilateral palatally impacted upper canines chose to have the unerupted teeth removed and replaced with implants and crowns. Two hydroxyapatite cylindrical implants were inserted through the alveolar ridge into the extraction sites. The unfilled areas in the extraction sites, around the dental implants, were packed and covered with demineralized freeze-dried bone allograft in conjunction with a collagen membrane barrier. Six months after implantation, computed tomography revealed complete osseous fill of the extraction defects and no bone loss around the implants. The implants were uncovered, and porcelain-fused-to-metal restorations were fabricated and placed. CLINICAL IMPLICATIONS: This treatment modality avoids the need for conventional preparation of teeth as part of prosthetic reconstruction or prolonged orthodontic treatment aimed at bringing the impacted canine to the dental arch. Combining the implantation with bone augmentation preserved the alveolar bone and shortened the treatment period.

Bone Transplantation↗
PubMed1999

Radiological findings of the post-sinus lift maxillary sinus: a computerized tomography follow-up.

The purpose of this paper is to present radiological findings of a short-term (8 to 10 months) computerized tomography (CT) follow-up study on 1-stage maxillary sinus lift cases. Pre- and postoperative dental CT scans of 21 patients (24 sinuses) after sinus lift procedures were compared. CT scans were used to assess newly formed bone and its interface with the implants, condition of the sinus membrane, evidence of buccal window cortication, and presence of any sinus pathology. Of the 57 implants placed, 28 had bone fully covering the implant on all sides which did not extend above the apical portion; 20 had bone fully covering the implant which did extend above the apex; and 9 exhibited incomplete bone coverage. All implants supported a fixed ceramo-metal prosthesis, and no implant failures were recorded after 3 years of follow-up. There was evidence of cortication of the buccal window in 10 sinuses; in the 14 remaining sinuses, bone consolidation on the buccal aspect was evident, but no evidence of cortication was seen. All sinuses healed without complications or clinical signs of sinusitis. In 11 sinuses, no changes in membrane thickness were noted. Membrane thickness decreased postoperatively in 12 sinuses, and in one, there was evidence of membrane thickening. Bone cortication in the anterior wall window may serve as an indicator for the remodeling status of the entire graft. Postoperative findings showed a significant improvement in overall membrane thickness. No clinical symptoms of sinusitis were evident, indicating that sinus lift procedures can be considered safe and do not predispose the sinus to acute or chronic sinusitis.

Adult↗
PubMed1999

Use of lyodura for bone augmentation of osseous defects around dental implants.

BACKGROUND: Lyodura has been used in periodontology and maxillofacial surgery to overcome different clinical conditions. The use of lyodura to induce new bone formation in humans has not been widely reported. The purpose of this article is to describe the use of lyodura as a resorbable barrier to promote bone formation in osseous defects around dental implants. METHODS: The study group consisted of 22 healthy patients (12 women and 10 men), with a mean age of 32 (range 20 to 45). A total of 44 implants (9 titanium screw-type and 35 hydroxyapatite-coated cylinder implants) were placed. Of these, 27 implants were placed in the maxilla and 17 in the mandible. At 27 extraction sites bony vertical defects were measured on the buccal, lingual, mesial and distal sides of the implant. In the remaining 17 cases, where either immediate or staged implantation was performed, and a dehiscence was present, its vertical length was measured from the alveolar crest. All bony defects were grafted with autogenous bone harvested from the tuberosity. Each site was covered with lyodura. RESULTS: Healing was uneventful; no inflammation, infection, or soft tissue dehiscence was observed. At all extraction sites and in 76% of the dehiscence defects, hard tissue appearing clinically similar to bone completely filled the defect. Of those defects not completely filled, a mean vertical bone increase of 2.5 mm was recorded. A mean vertical bone increase of 2.6 mm was achieved at extraction sites and a mean increase of 2.79 mm was achieved at dehiscence sites. CONCLUSIONS: Lyodura can safely and effectively be used for guided bone regeneration at both extraction sites and for dehiscence defects.

Absorbable Implants↗
PubMed1998

Patterns of metastases to the upper jugular lymph nodes (the "submuscular recess").

BACKGROUND: Cervical lymphadenectomy to remove metastatic disease in level II encompasses lymph nodes associated with the upper third of the internal jugular vein and the adjacent spinal accessory nerve (SAN). Conservative neck dissection (ND) preserves these structures but requires manipulation of the SAN to remove tissue located in the posterosuperior aspect of level II. Limiting the dissection to the nodal group anterior to the SAN may reduce operating time and limit injury to it without compromising the removal of lymph nodes at risk for involvement with cancer. METHODS: Seventy-one patients with squamous cell carcinoma of the head and neck treated with cervical lymphadenectomy at two separate institutions were prospectively evaluated. One hundred two neck dissection specimens were histologically analyzed for number of lymph nodes present and number involved with cancer. At the time of surgery, level II was separated into the supraspinal accessory nerve component (IIa) and the component anterior to the SAN (IIb). Nodal involvement in level II was analyzed according to characteristics of the cancer at the primary site as well as nodal involvement of other levels. RESULTS: Neck dissections were most commonly done for cancer of the oral cavity (n = 33), followed in frequency by the larynx (n = 17), oropharynx (n = 7), skin of face (n = 4), unknown primary (n = 4), and other sites (n = 6). Eighty NDs were selective and 22 were either radical or modified radical NDs. Pathologic staging of the neck specimen was most commonly N0 (n = 61), followed in frequency by N1 (n= 17), N2 (n= 11), and N3 (n= 11). Data were unclear for two specimens. Level IIb contained an average of 6.9 nodes and the IIa component contained an average of 4.2 nodes. Level II contained metastatic disease in 31 of 39 node positive specimens (79%). Level IIa was involved with cancer in four cases, all of which were preoperatively staged N2 or greater. CONCLUSIONS: The additional time required and morbidity associated with dissection of the supraspinal accessory nerve component of level II may not be necessary when performing elective ND. More research with larger numbers of patients, long-term follow-up, and meticulous tissue analysis is needed to permit conclusions as to where to draw the line in determining extent of cervical lymphadenectomy.

Adult↗
PubMed1998

The use of ultrasonography as a diagnostic tool for superficial fascial space infections.

PURPOSE: This study examined the value of ultrasonography as a diagnostic tool in the treatment of superficial acute odontogenic fascial space infections. PATIENTS AND METHODS: The study group consisted of 50 patients in whom both radiographic and sonographic examinations, as well as a needle aspiration, were performed. RESULTS: Purulent fluid was aspirated in 22 of the 50 patients. Six patients diagnosed as suffering from cellulitis had a repeated ultrasonography scan. In four, abscess formation was diagnosed on the third day. CONCLUSIONS: Ultrasonography is an effective diagnostic tool to confirm abscess formation in the superficial fascial spaces and is highly predictable in detecting the stage of infection.

Abscess↗
PubMed1998

Incidence of secretory otitis media following maxillectomy.

OBJECTIVE: The purpose of this investigation was to determine the incidence and characteristics of secretory otitis media after maxillectomy procedures. STUDY DESIGN: Retrospective chart analysis was performed with the cases of 49 patients who underwent maxillectomy for tumor in the Departments of Otolaryngology-Head and Neck Surgery and Oral and Maxillofacial Surgery between the years 1990 and 1996. RESULTS: In 10 patients (20%), secretory otitis media manifested itself from 1 week to 6 months after surgery; 1 patient developed a central perforation with chronic otitis media. Nearly one third of patients who underwent total maxillectomy had secretory otitis media. Six patients (8 ears) required insertion of ventilation tubes. CONCLUSIONS: Patients undergoing total and partial maxillectomies are prone to occurrences of secretory otitis media. Insertion of ventilation tubes easily resolves the problem. Preoperative and routine postoperative patient follow-up should always include otoscopy and audiometry, and tympanometry should be performed when warranted.

Adolescent↗