Showing papers by "University at Buffalo published in 1984"

The extraction of drainage networks from digital elevation data

Abstract: The extraction of drainage networks from digital elevation data is important for quantitative studies in geomorphology and hydrology. A method is presented for extracting drainage networks from gridded elevation data. The method handles artificial pits introduced by data collection systems and extracts only the major drainage paths. Its performance appears to be consistent with the visual interpretation of drainage patterns from elevation contours.

Black-pigmented Bacteroides species, Capnocytophaga species, and Actinobacillus actinomycetemcomitans in human periodontal disease: virulence factors in colonization, survival, and tissue destruction.

Abstract: There have been many advances in the past decade in our knowledge of the microflora associated with periodontal diseases, the potential of specific periodontal bacterial species to destroy periodontal tissues, and the host responses to bacterial infections of the periodontium. It is the purpose of this and an accompanying paper, to present important features of the host-parasite interaction in human periodontal disease. The present communication emphasizes characteristics of periodontopathic bacteria which may enable them initially to colonize the host, to survive in the periodontal pocket, and possibly to invade the gingival tissue despite potentially effective host defense systems, and to destroy the collagenous periodontal ligament, the alveolar bone, and other tissue components surrounding the tooth. It seems reasonable to assume that a bacterial species must possess factors applicable to most if not all of the above aspects of the infectious process of periodontal disease in order to produce periodontitis.

Studying Organizational Cultures Through Rites and Ceremonials

Abstract: Studies of organizational culture often focus on discrete cultural forms and fail to place phenomena studied within an overarching conception of culture. Overlap and confusion in terminology occur across studies. To alleviate these problems, this paper offers distinguishing definitions and advocates studying rites and ceremonials, which consolidate multiple cultural forms. The paper also presents, illustrates, and discusses a typology of rites and ceremonials and examines the implications of cultural studies for research and practice.

Surface properties determine bioadhesive outcomes: Methods and results

Abstract: This investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical-chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic-fibrocytic cells against the initially scrupulously cleaned, high-surface-energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre-adsorbed protein-dominated "conditioning" film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower-surface-energy materials typical of standard dental implants were "walled off" by a cell-poor, nonadhesive capsule with a fibrous interface separated from a thicker "conditioning" film by a lipid-rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.

Scale-dependent fractal dimensions of topographic surfaces: An empirical investigation, with applications in geomorphology and computer mapping

Abstract: Fractional Brownian surfaces have been widely discussed as an appropriate model for the statistical behavior of topographic surfaces. The fractals model proposes that topographic surfaces are statistically self-similar, and that a single parameter, the fractal dimension, applies at all scales. This paper presents the results of empirical examinations of 17 topographic samples. Only one of these samples shows the statistical behavior predicted by the fractals model; however, in 15 of the 17 samples, the surfaces' variograms could be adequately described by ranges of scales having constant fractal dimension, separated by distinct scale breaks. For scale ranges between adjacent breaks, surface behavior should be that predicted by the fractals model; the breaks represent characteristic horizontal scales, at which surface behavior changes substantially. These scale breaks are especially important for cartographic representations and digital elevation models, since they represent scales at which there is a distinct change in the relation between sampling interval and the associated error.

Host responses in periodontal diseases.

Abstract: Great progress has been made in our understanding of the pathogenesis of periodontal disease, the primary role of bacteria as etiologic agents, and the critical modifying role of host responses. It is useful to consider several stages in the pathogenesis of periodontal disease - (a) colonization, (b) invasion, (c) destruction, and (d) healing - and to place into perspective the various host responses as they may affect each of these four stages (Table 5). With respect to colonization, although very little direct evidence is available, it is reasonable to suggest that antibodies, either secretory or serum-derived, acting by virtue of their ability to block attachment, could inhibit colonization by immune reduction of adherence mechanisms. With respect to invasion of the tissue, it appears that phagocytes, particularly the neutrophils, are important, acting in concert with opsonic antibody and complement in ingesting and killing the periodontal microflora before or during the early invasive process. A major advance in our understanding of the pathogenesis of periodontal diseases is the realization that the virulence of periodontopathic bacteria relates to their leukaggressive properties, allowing them to evade neutrophil protective mechanisms. Invasion of the periodontal tissues by bacterial products may be inhibited by the complexing of these products with antibody with the formation of antigen-antibody complexes that are phagocytosed and digested, particularly by scavenger phagocytes such as the macrophage. With respect to the destructive phase of periodontal disease, it is clear that the direct effect of lymphocytes mediated either through direct cytotoxic activity, or through biologically-active destructive lymphokines (such as alpha-lymphotoxin and osteoclast activating factor), can lead to tissue destruction. Macrophages, through the production of monokines, collagenase, and reactive oxygen species, can also lead to tissue destruction. The direct effects of bacterial toxins or enzymes which can lead to tissue destruction can be inhibited by complexing with antitoxic or enzyme-neutralizing antibodies. With respect to healing and fibrosis, very little direct information is available; however, it is possible that the lymphocytes and macrophages affect fibrosis by the production of chemotactic factors for fibroblasts which would be expected to bring them to the area of periodontal inflammation and also by production of fibroblast-activating factors, which then cause the fibroblasts to proliferate and produce collagen which replaces lost collagen or results in fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

IgA anti-endomysium antibody. A new immunological marker of dermatitis herpetiformis and coeliac disease.

Abstract: The recently described IgA anti-endomysial antibodies (IgA-EmA) are directed against the intermyofibril substance of the smooth muscle, which may correspond either to a reticulin-like structure or a surface component of smooth muscle fibrils. These antibodies occurred in about 80% of sera of thirty-eight patients with dermatitis herpetiformis (DH), in about 70% of twenty-eight patients with coeliac disease and in about 20% of nine patients with other enteropathies. IgG class anti-gliadin antibodies (AGA) also occur in each of these diseases. Both antibodies were detected on monkey oesophagus by immunofluorescence. The IgA-EmA could not be detected in 122 control sera from patients with other gut or skin diseases, including fifteen cases with ulcerative colitis and fifteen cases with linear IgA bullous dermatosis (LABD). The presence and the titre of IgA-EmA and AGA paralleled the severity of the jejunal changes in patients with coeliac disease.

Sources and Outcomes of Stress in Organizational Settings: Toward the Development of a Structural Model

Abstract: An integrated structural model of stress in organizations was developed and tested through path analysis. Results provided qualified support for the causal assumptions underlying the model. Role fr...

Trainsdermal nitroglycerin in angina pectoris

Abstract: The hemodynamic and antianginal efficacy of transdermal nitroglycerin (TGTN) patches were assessed in patients with chronic, stable angina pectoris. In 11 patients, acute dosing with 10,20 and 30 cm 2 of TGTN (designed to deliver 5,10 and 15 mg GTN over 24 hours) improved treadmill walking time 2 and 4 hours after application, but no clinical effects were seen at 24 hours. In a second study in 6 patients with doses of 30, 60 and 90 cm 2 of TGTN treadmill walking time was improved at 2 and 4 hours, but no changes were seen at 24 hours except with the 90-cm 2 preparation. After daily therapy with 30-cm 2 patches of TGTN for 1 to 2 weeks, exercise tolerance was similar to that seen during daily placebo therapy. These results suggest that TGTN patches are of inadequate size to produce 24-hour antianginal protection. During sustained therapy, tolerance develops to the antianginal efficacy of this form of GTN administration.

An Investigation of Sex Differences in Pay Expectations and Their Possible Causes

Abstract: Discrepancies in the pay expectations of male and female management students were investigated, and potential causes of such discrepancies were explored. Females were found to have significantly lo...

A Model for Belief Revision.

Abstract: It is generally recognized that the possibility of detecting contradictions and identifying their sources is an important feature of an intelligent system. Systems that are able to detect contradictions, identify their causes, or readjust their knowledge bases to remove the contradiction, called Belief Revision Systems, Truth Maintenance Systems, or Reason Maintenance Systems, have been studied by several researchers in Artificial Intelligence (AI). In this paper, we present a logic suitable for supporting belief revision systems, discuss the properties that a belief revision system based on this logic will exhibit, and present a particular implementation of our model of a belief revision system. The system we present differs from most of the systems developed so far in three respects: First, it is based on a logic that was developed to support belief revision systems. Second, it uses the rules of inference of the logic to automatically compute the dependencies among propositions rather than having to force the user to do this, as in many existing systems. Third, it was the first belief revision system whose implementation relies on the manipulation of sets of assumptions, not justifications.

On knowing when to quit: Task failure, self‐esteem, advice, and nonproductive persistence

Abstract: Past research has found the performance of persons with high self-esteem to improve after failure, especially on tasks for which persistence correlates positively with performance. However, persistence may be nonproductive in some situations. Experiment 1 used a task for which persistence and performance were uncorrelated; subjects high in self-esteem persisted longer but performed worse than did those with low self-esteem, particularly after prior failure feedback. Experiment 2 tested whether differential sensitivity to advice about the efficacy of persistence mediates nonproductive persistence. High self-esteem subjects who received explicit advice against nonproductive persistence on a puzzle-solving task still tended to persist longer on unsolvable puzzles than did low self-esteem subjects. The implications of high self-esteem subjects' tendency to engage in nonproductive persistence are discussed.

1,4‐Dihydropyridine Ca2+ channel antagonists and activators: A comparison of binding characteristics with pharmacology

Abstract: This comparison of the binding characteristics and pharmacology of 1,4-dihydropyridines indicates that the high-affinity binding sites studied in cardiac and smooth muscle cells represent a major site of action of these drugs, and that this site is the Ca2+ channel or a closely related protein. Electrophysiological studies suggest that the effects of both Ca2+ channel inhibitors and activators are voltage dependent. The apparent lack of agreement between the equilibrium dissociation constants for [3H]1,4-dihydropyridines and their potency in cardiac muscle may be due to conformational modifications that occur in the 1,4-dihydropyridine binding site as a result of voltage or other changes during membrane isolation. The selective effect of 1,4-dihydropyridines for vascular smooth muscle relative to cardiac muscle may be explained, in part, by differences in membrane potentials and Ca2+ channel regulatory mechanisms and, in part, by differences in receptor structure. 1,4-Dihydropyridine antagonists and activators appear to bind to a common site that is not the same as the binding site for nondihydropyridine Ca2+ channel antagonists.

Extended least squares nonlinear regression: A possible solution to the “choice of weights” problem in analysis of individual pharmacokinetic data

Abstract: It is often difficult to specify weights for weighted least squares nonlinear regression analysis of pharmacokinetic data. Improper choice of weights may lead to inaccurate and/or imprecise estimates of pharmacokinetic parameters. Extended least squares nonlinear regression provides a possible solution to this problem by allowing the incorporation of a general parametric variance model. Weighted least squares and extended least squares analyses of data from a simulated pharmacokinetic experiment were compared. Weighted least squares analysis of the simulated data, using commonly used weighting schemes, yielded estimates of pharmacokinetic parameters that were significantly biased, whereas extended least squares estimates were unbiased. Extended least squares estimates were often significantly more precise than were weighted least squares estimates. It is suggested that extended least squares regression should be further investigated for individual pharmacokinetic data analysis.

Evaluation of a family asthma program

Abstract: This article presents the results of an evaluation of a 12-hour patient education program for children with asthma and their parents. Ninety-two of 147 participants (63%) completed the 1-year follow-up. The effectiveness of the family asthma program (FAP) was measured by a "knowledge of asthma" questionnaire administered before and at the last session; it demonstrated a significant improvement for parents ( p p p p p p p

Natural history of large local reactions from stinging insects

Abstract: In ongoing studies of the natural history of stinging-insect allergy, 133 patients with large local reactions have been evaluated over 8 yr; 79 patients returned for reevaluation. Based on RAST analysis with honeybee and vespid venoms, patients were divided into RAST-positive and RAST-negative groups. Sixty-six patients were RAST-negative with positive venom skin tests in 58%. Seventy-five restings in this group led to no systemic reactions and 74 large local reactions. At follow-up RASTs remained negative, and the incidence of positive skin tests was unchanged. Sixty-seven patients had detectable serum venom-specific IgE covering a wide range in antibody titers, indistinguishable from patients with systemic reactions. Twenty-four of 67 patients received venom immunotherapy (VIT). RAST titers decreased similarly in the VIT and untreated groups. There were 55 restings resulting in 40 recurrent large local reactions occurring in equal incidence in treated and untreated patients. One systemic reaction occurred in an untreated patient. In reviewing 118 patients with sting anaphylaxis, a previous large local reaction occurred in five. These results suggest that after repeat stings, patients with large local reactions tend to have subsequent large local reactions, regardless of the presence of venom-specific IgE or immunotherapy. There is small risk of anaphylaxis. Determination of serum venom-specific IgE by RAST or skin tests does not aid in treatment or in predicting prognosis. Thus skin tests are not necessary in patients who have had large local reactions, and venom immunotherapy is not indicated.

Sources of dentists' stress.

Abstract: A two-page questionnaire on stress in dentistry was completed by dentists participating in the Health Screening Program at the 3982 ADA Annual Session. The ques­tions focused on the dentists' perceived sources of stress. Six items form a pattern for stress: some are unique to dentistry, others relate to today’s fastpaced society.

Synthesis and biodistribution of neutral lipid-soluble Tc-99m complexes that cross the blood-brain barrier.

Abstract: Three Tc-99m-labeled neutral 1,2-dithia-5,8-diazacyclodecane (BAT) chelates that are capable of crossing the blood-brain barrier (BBB) were prepared and evaluated. Biodistribution (i.v.) in rats showed a significant brain uptake (1-3%/whole brain) at 2 min. At 15 min the uptake dropped to about a tenth of the original level, indicating free passage in both directions across the BBB. Gamma camera images of a monkey confirmed the high initial brain uptake. This group of Tc-99m BAT compounds clearly exhibited in vivo stability and the ability to cross the BBB after an i.v. injection. Derivatives containing tertiary amine groups should have prolonged brain retention and might be suitable for SPECT studies of brain perfusion.

Functional Assessment in Rehabilitation Medicine

Abstract: Medical rehabilitation addresses problems in the measurement of human function and health-related quality of life as well as problems in diagnosis and measurement of impairment. This article summarizes basic principles of measurement relevant to medical rehabilitation and presents examples of standards for development of measures and for their application in clinical practice. Measurement and clinical evaluation in medical rehabilitation need to be grounded in principles of validity and reliability. Improved measurement tools will secure the scientific basis of medical rehabilitation and enhance its long-term growth.

Transdermal isosorbide dinitrate in angina pectoris: effect of acute and sustained therapy.

Abstract: Twelve patients with chronic, stable angina pectoris underwent hemodynamic investigations and treadmill exercise testing before and during a 24-hour period after the application of 100 mg of transdermal isosorbide dinitrate (ISDN) and matching placebo. Compared with placebo, there were no changes in systolic blood pressure or heart rate at rest or during exercise; but treadmill walking time to the onset of angina and to the development of moderate angina was significantly prolonged at 2,4 and 8 hours, but not at 24 hours, after drug application. Patients subsequently received these same treatment regimens for 7 to 10 days and underwent repeat exercise testing. During this sustained phase of the investigation, treadmill walking time to the onset of angina and to the development of moderate angina was similar 4, 8 and 24 hours after application of ISDN and placebo. Thus, transdermal ISDN in a dose of 100 mg is effective for 8 hours during acute therapy, but during sustained therapy tolerance developed and no antianginal effects of ISDN persisted.

Bleaching of reef coelenterates in the San Blas Islands, Panama

Abstract: Starting in June 1983, 25 species of hermatypic corals, gorgonians, hydrocorals, anemones and zoanthids in the San Blas Islands, Panama, began showing signs of a loss of colour leading in some cases to a white “bleached” appearance. Histologic examination of six coral species indicated that bleaching was associated with drastic reductions in the density of zooxanthellae and with the atrophy and necrosis of the animal tissue. The severity of the bleaching varied among species and many species were unaffected. The species most extensively affected were: Agaricia spp., which became completely bleached and frequently died; Montastraea annularis which bleached and continued to survive; and Millepora spp. which bleached white but quickly regained their colouration. Shallow reefs dominated by Agaricia spp. suffered the most extensive bleaching. At one site, Pico Feo, 99% of the Agaricia (32% of the living cover) was bleached. On fore reers, which were dominated by Agaricia spp. and M. annularis, the proportion of M. annularis bleached ranged from 18 to 100% and that of Agaricia spp. from 30 to 53%. Transects at Sail Rock and House Reef were surveyed in August 1983 and January 1984. At those sites, 53% of the Agaricia cover died between August and January. The remaining living cover of Agaricia and of all other species exhibited normal colouration in January. Salinity and temperature were monitored every second day at 4 m depth between May 10 and August 28, 1983 at one of the localities. Bleaching was first observed within two weeks of a 2 °C rise in temperature which occurred in late May 1983. Temperatures remained at or above 31.5 °C for the following 3 weeks and were at or above 30 °C for an additional 4 weeks. The bleaching of corals in the San Blas was most likely due to those elevanted temperatures.

Predilection of Lung Cancer for the Upper Lobes: An Epidemiologic Inquiry

Abstract: Data from 24,798 cases of primary neoplasm of the lung registered by the Surveillance, Epidemiology, and End Results Program between 1973 and 1977 were examined for the demographic determinants of lobe of origin. Lung cancer occurred predominantly in the upper lobes in both sexes, in both blacks and whites, and at all ages. This pattern was observed for squamous cell and small cell carcinoma as well as adenocarcinoma. The predominance of lung cancer in the upper lobes was much stronger in the young and somewhat stronger in blacks. These findings are discussed in light of current theories of pulmonary carcinogenesis. Current theories may not explain entirely these observed patterns, and further inquiries into this question, therefore, may be useful.

Development of a patient measure of satisfaction with the dentist: The Dental Visit Satisfaction Scale.

Abstract: Although patient satisfaction has been studied in the traditional medical context, patient satisfaction with the dentist has received only minor attention. This paper reports the development of a 10-item Dental Visit Satisfaction Scale. This scale was designed to assess patient satisfaction with the dentist in the context of a specific visit. It provides three subscales-Information-Communication, Understanding-Acceptance, and Technical Competence-as well as an overall measure of satisfaction. Satisfactory internal consistency was obtained for all scale measures, and one assessment of construct validity is reported. Potential clinical and research applications are discussed.