Evidence Of Attenuation Research Articles

Multivariate multilevel models for repeated measures in the study of smoking effects on the association between plaque and gingival bleeding

Multivariate multilevel modeling was applied to analyze repeated measures data on the influence of heavy smoking on the association between the amount of supragingival plaque and gingival bleeding on probing (BOP) in a steady-state plaque environment. Data acquired in 65 systemically healthy young adults with mild plaque-induced gingivitis were analyzed. 33 heavy smokers consumed at least 20 cigarettes per day while 32 were non-smokers. Periodontal examinations at the outset consisted of periodontal probing depth, clinical attachment level, BOP, plaque index, and presence of calculus at 6 sites of every tooth present. They were repeated 3 times every 8 weeks. A multivariate 4-level variance component model revealed that the odds of BOP was twice as high in smokers. In addition, females had a lower likelihood for BOP but, with increasing bleeding scores during the course of the study, this effect attenuated. Low biserial correlations for BOP at the site level of between 0.11 and 0.2 were found. At the tooth level, correlations were moderate (0.2-0.5), and highest at the subject level (0.8-0.9). Variations at subject and tooth levels were very large at the outset but notably attenuated in the course of the study. Plaque consistently influenced the tendency for BOP with an odds ratio of about 1.7-1.8 for each increase in score in both smokers and non-smokers. The present study did not reveal evidence for attenuation of the plaque/gingival bleeding relationship in heavy smokers.

Attenuation of Petroleum Hydrocarbons by Weathering: A Case Study

Possible alterations in the distribution and composition of total petroleum hydrocarbon (TPH), polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethyl benzene, and xylene isomers (BTEX) in the released oil at Idu-Ekpeye in Niger Delta (Nigeria) were studied within two seasonal variations of two months and six months, with a view to assessing the level of attenuation of these hydrocarbons in impacted soils. Although there were significant contaminations in the kerosene range (n-C10-n-C14) two months after, especially of the n-C12 and n-C13 fractions, the complete disappearance of the n-C8 to n-C23 hydrocarbons, including the acyclic isoprenoids (pristane and phytane), and the reduced amounts of PAHs, and BTEX, six months after, provided substantial evidence of attenuation as indicated in the reduction in total hydrocarbon content (THC) from 61.17 to 42.86%. Soil physicochemical properties such as pH, moisture content, heavy metal, TOC, and TOM, all provided corroborative evidence of hydrocarbon attenuation. The pristane/phytane ratio of the spill samples suggests that the spilled oil was genetically oxic.

C-Reactive Protein and Risk of Cardiovascular Disease in Men and Women From the Framingham Heart Study

Determination of C-reactive protein (CRP) level has been suggested to improve cardiovascular disease (CVD) risk assessment. This study examines the utility of CRP levels to assess CVD risk in a community setting. We performed a prospective observational cohort study on a community population sample. A total of 1949 men and 2497 women without CVD from the Framingham Heart Study underwent CVD risk factor assessment. Initial CVD events during 8 years of follow-up were recorded. There were 283 major CVD and 160 major coronary heart disease incident events. Age-, sex-, and multivariable-adjusted analyses generally used CRP level categories of less than 1, 1 to 3, and greater than 3 mg/L. In age- and sex-adjusted models, the traditional risk factors and elevated CRP levels indicated increased risk. The age- and sex-adjusted relative risk (RR) and 95% confidence interval (CI) of CRP level greater than 3 mg/L for major CVD was elevated (RR, 1.60; 95% CI, 1.19-2.14), with evidence of attenuation (RR, 1.22; 95% CI, 0.90-1.66) in multivariable models. The C statistic, a measure of the discriminatory capability of the prediction models, was 0.74 for prediction of major CVD with age and CRP level. In multivariable models that included traditional risk factors, the C statistic was 0.78, a value that was unchanged with the addition of CRP to the multivariable model. Similar relations were noted for major coronary heart disease events. Elevated CRP level provided no further prognostic information beyond traditional office risk factor assessment to predict future major CVD and major coronary heart disease in this population sample.

Coupling between sedimentary dynamics, early diagenetic processes, and biogeochemical cycling in the Amazon–Guianas mobile mud belt: coastal French Guiana

Coastal French Guiana lies within the vast mobile mudbelt that characterizes much of the S. American inner shelf downdrift of the Amazon River. Approximately ∼15–20% of the Amazon sediment outfall moves NW along the Guianas, in part as a series of 20–25 coastal mud waves. Seasonal studies of a representative migrating mudwave located between Kourou and Sinnamary, French Guiana demonstrate that diagenetic properties and biogeochemical cycling are closely coupled to sedimentary dynamics and the refluxing of reduced components between the seabed, coastal facies, and well-oxygenated overlying water. An unsteady two-zone diagenetic regime is typically present in the shallow subtidal and low intertidal regions. A surficial layer, usually ∼0.5–1 m thick, is nonsulfidic, highly reactive, and dominated by Fe, Mn cycling. This suboxic layer unconformably overlies more consolidated sediment in which net SO 4 2− reduction is often observed, and contracts shoreward toward the mangrove fringe as sediments stabilize and become bioturbated. The relatively stable intertidal flats are also sites of significant benthic primary production. Despite suboxic conditions over extensive intervals, anaerobic remineralization rates are high (ΣCO 2∼0.2–0.6 mM day −1), and often show little evidence of attenuation with depth. Integrated ΣCO 2 fluxes are ∼20–235 mmol m −2 day −1 (wet/dry season average ∼120), far exceeding diffusive O 2 fluxes into the bottom. High reactivity (∼0.08 day −1) and low C/N remineralization release ratios (∼5.3) of decomposing material imply fresh substrate of marine origin. Most reduced solid phase Fe is present as nonpyritic authigenic Fe minerals (<20% Fe(II) is in pyrite), and low sedimentary C/S ratios (∼6–8) reflect the generally nonsulfidic conditions. A broad range of tracers (e.g. 234Th ( t 1/2=24 days), 210Pb ( t 1/2=22 years), seasonal Cl − profiles) and nonsteady state diagenetic models of pore water concentrations and oxidant–reductant relationships demonstrate that the upper 0.1–1 m of deposits are reworked and exchanged with overlying water on timescales of <10 days to seasonally. Thus, the seafloor acts as a massive suboxic batch reactor, entraining and processing reactive marine plankton, regenerating Fe, Mn oxides, exchanging metabolites and nutrients with the oxygenated water column, and generating suites of nonsulfidic authigenic minerals. The apparent paradoxical properties of high remineralization rate, low reductant content (C org∼630 μmol g −1), and dominance of suboxic metal cycling are a direct consequence of frequent entrainment of highly reactive organic substrate and simultaneous regeneration of the major Fe oxidants in oxygenated water. The Amazon–Guianas mobile mudbelt is a zone of extraordinarily intense sedimentary and biogeochemical recycling, greatly exceeding stable coastal systems, such as salt marshes, in material exchange with the sea.

Characteristics of supine myocardial perfusion SPECT (MPS) which predict normalization on prone imaging could simplify acquisition and aid image interpretation

Background: Imaging in the prone position is known to differentiate true perfusion defects from abnormalities created by artifacts seen on supine MPS images. If normalization on prone imaging could be predicted, additional prone images could be avoided while maintaining diagnostic accuracy. Methods: Two blinded observers identified 236 coronary vascular areas in 176 patients, 124 men and 52 women, with abnormal or possibly abnormal supine MPS who had prone images after stress performed at UCSF between 9 and 11/03. Nineteen image features based on gender, defect location, intensity, variation at rest MPS (when acquired), evidence of attenuation or motion, cavitary dilation, lung uptake, background activity, counts density and wall motion (WM) were related by multiple logistic regression (LR) and a C4.5 decision tree (DT) analyses to the likelihood of defect normalization on prone imaging. The overall population was divided into test and validation groups. Coronary angiograms within 2 years of MPS were available in 48 patients. Results: Prone images agreed with angiographic findings in 41 of 48 (86%) patients. LR predicted prone image findings in all cases but required input from all 19 factors. In both men and women 10 fold stratified cross validation predicted prone image normalization (p < 0.05) by non-segmental, low intensity, shifting defects, patient motion and low count images, and persistent prone defects by dense, segmental, stress induced defects, cavitary dilation, lung uptake and WM abnormalities. DT analysis simplified the findings and identified image findings and their combination with high predictive accuracies in the validation group, where a dense defect, a low intensity defect with either abnormal WM, or with an abnormal polar map (PM) and segmental defect were predictive of persistence on prone, while a normal PM, or a low intensity defect with either normal WM, or with a normal PM with a non-segmental defect predicted prone normalization with accuracies over 93%. Conclusion: A few critical findings on supine MPS predict the findings on prone images. These findings aid image interpretation and reduce the need for added prone images.

Evidence for attenuation of the colo-rectal reflex in non-constipated irritable bowel syndrome

Evidence for attenuation of the colo-rectal reflex in non-constipated irritable bowel syndrome

Evidence for attenuation of the colo-rectal reflex in non-constipated irritable bowel syndrome

Evidence for attenuation of the colo-rectal reflex in non-constipated irritable bowel syndrome

Physical activity and cause-specific mortality in men: further evidence from the Whitehall study.

Reports of studies relating physical activity to stroke and cancer sub-types indicate inconsistent findings. Some are hampered by low statistical power, owing to a low number of events, and a failure to adjust for potential confounding variables. The purpose of this study was to relate physical activity to 12 mortality endpoints in a prospective cohort study of 11,663 men aged 40-64 years who responded to an enquiry about travel activity during a baseline medical examination conducted between 1967 and 1969. During 25 years of follow-up there were 4672 deaths. Travel activity was inversely related to mortality attributable to all-causes, coronary heart disease, respiratory disease and lung cancer, whereas the association with stroke was positive. There was evidence for attenuation of some of these associations on adjustment for potentially confounding variables. Our simplistic measure of physical activity may, in part, explain the weak associations seen.

The cold pressor test: vascular and myocardial response patterns and their stability.

The purposes of the present study were to compare the cardiovascular response patterns evoked by three versions of the cold pressor test (either forehead stimulation or hand or foot immersion) and to determine the reproducibility of the responses over a 2-week interval. Blood pressure, heart rate, stroke volume, cardiac output, total peripheral resistance, and systolic time intervals were obtained during rest and during the cold pressor test in 42 young men. Across conditions, the pressor response was supported by peripheral resistance increases with concomitant stroke volume decreases. Although the response patterns were generally similar across sites, exceptions were apparent for heart rate. Forehead stimulation was characterized by no significant change in heart rate, whereas limb (hand or foot) immersion was associated with significant heart rate acceleration. The responses elicited by the three cold pressor test conditions were reliable and showed little evidence of attenuation over the test-retest interval.

Evidence for attenuation of hypothalamic gonadotropin-releasing hormone (GnRH) impulse strength with preservation of GnRH pulse frequency in men with chronic renal failure.

To investigate the nature of putative disturbances in pulsatile gonadotropin (LH) secretion in men with chronic renal failure, we undertook blood sampling at 10-min intervals for 24 h in 9 hemodialysis-dependent uremic men and 16 community- and age-matched controls. Serum LH concentrations were measured in a 2-site immunoradiometric assay, which does not cross-react with free alpha or LH beta-subunit and correlates well with an in vitro Leydig cell bioassay. Deconvolution analysis was applied to calculate the number, amplitude, mass, and duration of spontaneous LH release episodes and simultaneously estimate the half-life of endogenous LH in each subject. We observed that: 1) the estimated half-life of immunoradiometric LH removal from plasma averaged 103 +/- 11 min in normal and 207 +/- 29 min in uremic men (P < 0.01); 2) the number of LH secretory bursts was slightly higher in uremic than healthy men (e.g. 20 +/- 2.2 vs. 15 +/- 1.0 secretory bursts/24 h, respectively; P = 0.05); 3) the mass of LH secreted per burst was approximately 50% lower in chronic renal failure than in health, namely 1.4 +/- 0.18 vs. 2.8 +/- 0.42 IU/L (P < 0.01); 4) the decrease in the mass of LH secreted per burst was not due to a decline in LH secretory burst amplitude, but rather an attenuation of LH secretory burst duration (4.8 +/- 0.35 min in uremic vs. 11 +/- 1.3 min in normal men; P < 0.001); 5) the mean 24-h serum immunoradiometric LH concentration was significantly higher in uremia at 5.7 +/- 0.68 vs. 3.6 +/- 0.41 IU/L in controls (P = 0.017); and 6) serum estradiol concentrations were increased in uremia, but total and free testosterone concentrations did not differ significantly between the two subject groups. In response to synthetic GnRH (10 micrograms, administered iv after the 24-h basal sampling period), the mean mass of immunoradiometric LH released within each calculated LH secretory burst was similar in uremic (n = 8) and normal (n = 21) individuals. We conclude that uremia is accompanied by a specific defect in the pulsatile mode of LH secretion, which is marked by an abbreviation of LH secretory burst duration and a consequent fall in the mass of LH secreted per spontaneous release episode. There is no overall decline in LH secretory pulse frequency or gonadotroph responsiveness to a submaximally effective dose of exogenous GnRH. Such findings are consistent with diminished hypothalamic GnRH impulse strength.(ABSTRACT TRUNCATED AT 400 WORDS)

Studies in monkeys of attenuated hepatitis A variants.

Three HAV variants, H2M20(35 degrees C), H2M20(35 degrees C) and H2M20K5(32 degrees C), were developed by passage in different tissue culture cells and at different temperatures. Virulence for monkeys was assessed by inoculating each of the variants into four monkeys. Weekly bleeding through 16 weeks post-inoculation was assayed for anti-HAV titers and SGPT as well as LDH5 activities. And in some monkeys liver biopsies were also studied. Seroconversion was induced in all of the inoculated monkeys. The anti-HAV titers tested at 16 weeks post-inoculation were: 40-640 with H2M20(35 degrees C), 40-160 with H2M20(32 degrees C) and 20-40 with H2M20K5(32 degrees C). These variants showed different levels of virulence/attenuation for monkeys. Variant H2M20(35 degrees C) showed no evidence of attenuation, variant H2M20(32 degrees C) retained slight virulence and variant H2M20K5(32 degrees C) showed no evidence of virulence for monkeys. Criteria are proposed for assay of HAV virulence tested in monkeys.

Mortality and lung histopathology after inhalation lung injury. The effect of corticosteroids.

An animal model was used to study the effects of early administration of intramuscular corticosteroids on mortality and lung histopathology induced by a component of smoke. Thirty-six rabbits (mean weight, 2.7 kg) were exposed to acrolein vapor for 15 min; 30 min later the animals were divided into 3 treatment groups. One group received saline placebo intramuscularly at 12-h intervals, a second group was treated intramuscularly with 100 mg methylprednisolone at 12-h intervals, and a third group was treated with a single 100-mg dose of methylprednisolone followed by doses of saline at 12-h intervals. The animals were studied for a 72-h period. There was a significantly lower mortality in the 2 steroid-treated groups than in the nontreated group. A scoring system was developed for evaluating observed histologic changes in the lung. No correlation was seen between survival and histologic score or between score and treatment. High scores for particular histologic features did not explain mortality nor did they predominate in untreated animals; "vascular congestion" was found to be greater in the steroid-treated group. The beneficial effects of steroids in reducing mortality after inhalation of a common smoke constituent was not associated with any evidence of attenuation of lung damage.

Effects of residence in fishes upon the pathogenicity ofsalmonellaserotypes for laboratory white mice

Abstract Increasing evidence indicates that freshwater fishes may be naturally and experimentally infected with Salmonella and may harbor the pathogen for more than 100 days. The effects upon the pathogenicity of various serotypes for white mice following residence in freshwater fishes was evaluated. Virulence patterns of serotypes cultured from fish were compared with the same serotypes cultured from man and lower animals. LD50 and ID50 values for the respective isolates were ascertained following intraperitoneal injection of mice. With the exception of 1 strain of S. typhimurium, var. Copenhagen (a smooth (S) phase culture, which rapidly mutated to the rough (R) state) there was no evidence of attenuation or loss of virulence of the sero‐types. Results of the study indicate that residence or colonization in poikilotherms has no marked effect on pathogenicity for homoeio‐thermic hosts.

Temperature-sensitive mutants of type I Streptococcus pneumoniae: preparation, characterization, and evidence for attenuation and immunogenicity.

Thirteen temperature-sensitive (ts) mutants of type I Streptococcus pneumoniae were selected after exposure of virulent wild-type (ts+) organisms to nitrosoguanidine. Each mutant resembled the ts+ parent in properties of alpha-hemolysis, bile solubility, optochin sensitivity, antibiotic sensitivity, and serotype. Unlike the ts+ parent, however, each ts mutant was restricted in its capacity to form colonies on blood agar at 38 C. With the exception of two mutants, there was a correlation between the degree of temperature-sensitivity of a mutant and its genetic stability. When inoculated intraperitoneally into mice, 11 of 13 mutants were attenuated and induced homologous resistance. Three mutants (ts 1, ts 3, and ts 4) were also studied in hamsters and were found to be attenuated and immunogenic after intraperitoneal injection. Study of the behavior of mutants ts 1, ts 3, and ts 4 in the blood of hamsters suggested that attenuation may be related, in part, to decreased growth and survival of ts organisms at body temperature. Mutants ts 1 and ts 4 were completely attenuated for hamsters when administered intranasally and induced significant resistance to subsequent challenge with wild-type organisms by the same route. Local administration of ts mutants of type 1 S. pneumoniae to hamsters may provide a model for evaluating the potential of live vaccines in the prevention of disease due to bacterial respiratory tract pathogens.

The angular scattering of superthermal K by I2

Abstract The small angle scattering of 100 eV potassium atoms from a thermal cross beam of iodine molecules has been measured. There is considerable structure, which is interpreted as coming from the Coulomb potential. Some contribution from the upper diabatic state is also probably needed and there is evidence of attenuation of the elastic scattering beyond ≈0.9°.

The Bagshot Beds of Bagshot Heath (a Rejoinder)

The Author maintains that the northerly attenuation of the Lower Sands and of the ‘green-earth series’ between the two principal brick-clays of the district is an established fact. He insists on the value of the Wellington College well-section as a vertical datumline, on account of its proximity to the northern outcrop (which is not the case with the Goldsworthy section), and criticizes the arguments recently put forward in favour of an alternative and very doubtful sectional reading. But it does not stand alone, for the well-section at the Bagshot Orphan Asylum gives practically the same sequence, and affords strong evidence of the thinning northward of the above-named deposits. (Other instances cited by the Author in ‘Recent Contributions’ &amp;c., corroborate the reading he has adopted.) The Goldsworthy section itself lends strong corroborative evidence as to the value of the College well-section. The evidence of attenuation in the direction of Bracknell the Author reserves for the present. In his paper published in the February number of the Society's Journal for the current year, Mr. Monckton ignores the determinative value of stratigraphical alignment of the clays claimed as the basal clays of the Middle group with clays of the same character seen cropping out from below the ‘green-earth series’ at no great distance. This evidence of stratigraphical alignment must be allowed due weight when set against evidence derived from such lithological characters as the presence of pipe-clay, mica, and false-bedding. The Author considers that the argument as to the fossil evidence is over-stated