1,721,147 research outputs found
Ultrastructural aspects of platelets in atherosclerosis and related diseases
No full textCirculating platelets in experimental models of atherosclerosis, as well in condtions linked to atherogenesis in humans, are activated, as shown by our ultrastructural studies, demonstrating for the first time their morphological/morphometrical features.
Prostacyclin and 8-chlorocarbochromen (but not acetylsalicylic acid) are able to inhibit in vitro and in vivo (8-chlorocarbochromen) the process
Platelets in the platelet-vessel wall interaction
No full textUltrastructural and biochemical aspects of reversible and non-reversible platelet-vessel wall interaction are presented. Special attention is directed towards the role of release products of platelets, the plasmatic coagulation factors and the prostaglandin system. An up-to-date view of the role of platelet-vessel wall interaction in atherogenesis is discussed
On the involvement of platelets in atherogenesis: some ultrastructural features
No full textUltrastructural morphometry reveals plasma-membrane changes, aspect of platelet activation, in hypercholesterolemic rabbi
Circulating platelets plasma membrane of normocholesterolemic and hypercholesterolemic rabbits tested with aspirin: a freeze-etching study of the platelet plasma-membrane "protuberances"
No full textPlatelets plasma-membrane show some ultrastructural formations, quite different from pseudopodies and from "particles", termed by us "protuberances". Statistic tests/showed the average value of "protuberances" strongly increased in hypercholesterolemic (HC) rabbits compared with the one of normocholesterolemic (NC) rabbit platelets. After i.v. administration of aspirin, the number of the "protuberances" of circulating platelets of the normocholesterolemic and hypercholesterolemic rabbits didn't show a significant difference in comparison with the no ASA treated NC and HC rabbits. "Protuberances" don't seem to be correlated with the secretion of substances of the aggregation pathway. © 1980 The Italian Pharmacological Society
Impact of Concave/Convergent vs Parallel/ Divergent Implant Transmucosal Profiles on Hard and Soft Peri-implant Tissues: A Systematic Review with Meta-Analyses
No full textPurpose: To systematically review the literature comparing marginal bone loss (MBL) and pink esthetic scores of implants with convergent or concave transmucosal profiles vs divergent or parallel profiles. Materials and Methods: A PICO question was defined, and an electronic search was carried out in the MEDLINE/PubMed and Cochrane Oral Health Group databases. Studies documenting type of transmucosal profile (either tissue-level profiles or abutments) and soft and/or hard tissue outcomes of implants were considered eligible. Studies were selected on the basis of the inclusion criteria and quality assessments. A meta-analysis with subgroup analyses was performed. Results: Five papers fulfilled the inclusion criteria, and four were eligible for meta-analysis. Significantly less MBL was found in concave/convergent groups, with a mean difference of 0.772 (95% confidence interval [CI]: 0.450 to 1.095; P < .001). In the subgroup analyses for platform-switching and platform-matching connections, a significant effect in favor of concave/convergent was detected, with a standardized difference in means of 1.135 (95% CI: 0.688 to 1.583, P < .001) when platform switching was considered. No significant effects were found for platform-matching connections. Conclusion: Within the limitations of this review, it is suggested that concave/convergent implant transmucosal profiles result in less MBL. No statistically significant results were obtained for soft tissue-related outcomes or for the platform-matching connection subgroup
Ultrastructural computerized morphometry of platelets in chronic myelogenous leukemia making use of ultra-thin sections and freeze-fracture procedure. A preliminary approach
No full textBiochemical and morphological data have shown that the circulating platelets are deeply altered in patients with chronic myelogenous leukemia. In this report we describe the results of ultrastructural morphometry performed by means of a computerized device of the platelet shape (ultra-thin sectioned platelets) and of the platelet plasma-membrane (freeze-fractured platelets). Platelets appeared deeply modified: reduced mean platelet area and perimeter, increased surface density of the openings of the surface connected canalicular system, abnormal features of the platelet cytoplasm and some aspects of platelets joined together even if with heterogeneity in these findings did appear from patient to patient
World Health Organization (WHO) and the World Heart Federation (WHF) Pathobiological Determinants of Atherosclerosis in Youth (PBDAY) Study. Lipid and raised lesion distribution in the right coronary artery of young people
No full textBACKGROUND AND AIM: As part of the WHO-WHF PBDAY Study, we examined the proximal segment of the right coronary artery (RCA) (n = 469) of 5-34 yr-old otherwise healthy trauma victims from 15 countries to establish the topographical relation of atherosclerotic lesions to age, sex and geographical location.
METHODS AND RESULTS: Topography and extent of lesions were analyzed by image processing and probability-of-occurrence maps of lipid lesions (mostly fatty streaks) and raised lesions on the intimal surface of the RCA were produced. Extension of lesions varied considerably between the groups and between individuals in the same group. The prevalence of lipid lesions was 68% (319/469) compared with 100% in the aorta. The prevalence of raised lesions was 22% (102/469) compared with 7% and 26% in the thoracic and abdominal aorta. Females had more lipid lesions, whereas raised lesions prevailed in males. Lipid lesion extent increased with age in both sexes.
CONCLUSIONS: High probability-of-occurrence areas for lipid and raised lesions prevailed in the proximal 5 cm of the intimal surface of the RCA (myocardial side) and were greatly overlapping. Regression analysis between lipid and raised lesion extent in the thoracic or abdominal aorta and the RCA showed no correlations between the lipid lesion extent, whereas significant correlations were found between the raised lesion extent in the RCA and the thoracic aorta only, showing that the two types of lesion behave differently in different anatomical locations
Effects of prostacyclin on ultrastructural features of human platelets in vitro
No full textExamining platelets plasma-membrane by freeze-etching (FE)-technique irregularly place among the "particles", some larger formations, called by us "protuberances" can be seen. These protuberances may represent the stomata of the open canalicular system (OCS) and the morphological aspect of an exocytotic process. Addition of prostacyclin to platelet rich plasma (PRP) leads to a decrease of the average value of protuberances which is statistically significant in comparison to control platelets
Ribozymes: Analytical Solution of the One-Substrate, Two-Intermediate Reversible Scheme for Enzyme Reactions
No full textAbstract The paper presents a kinetic analysis of a reversible enzymatic reaction S! P
involving two intermediate compounds under the condition [E]0≫[S]0+[P]0. For the case of
mono-exponential behavior, we derive an equation for kobs as a function of [E]0, which
emphasizes the pitfalls of oversimplifying kinetic schemes (such as the Michaelis-Menten
model) for ribozyme studies. This novel apparent rate constant, which has been arrived at
through mechanistic considerations, is analyzed, and the characteristic parameters obtained.
The equation, which seems to fit experimental data better than conventional approximations,
is used to analyze a single turnover study on an ADC1 ribozyme drawn from hepatitis
delta virus RNA. The microscopic kinetic constants for such enzyme are evaluated and its
mono-exponential behavior verified.
Key words: ribozyme kinetics . Michaelis-Menten . low catalytic enzyme . kinetic analysis .
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Ultrastructural Features of Human Platelets Treated in Vitro with Aggregative and Antiaggregative Prostaglandins. A Freeze-Etching Study
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