2. What causes dementia?

‘What causes dementia?’ looks at the mechanisms underlying dementia. Dr Aloysius Alzheimer identified two key features in the brain. These were a build-up of plaques dominated by the amyloid-beta protein and tangled or misfolded tau proteins. How do we research the causes of dementia? Options include animal studies, human samples including stem cells and organoids, and improved neuroscience technologies such as brain scans and MRIs. Some scientists argue that smaller soluble oligomers are as dangerous as amyloid plaques, some continue to support the amyloid cascade theory, and others look elsewhere for advances and a possible cure. Theories beyond the amyloid hypothesis are receiving more funding, changing the focus of research.

Modern view on hemostasis system: cell theory

For many years, there has been no model capable of explaining the complex processes of interaction between various bloodclotting factors leading to a stop of bleeding. One of the most successful models able to partially reflect the mechanisms of hemostasis for a long time was the cascade theory. The cascade model perfectly explains the processes occurring during coagulation in vitro, but was completely inadequate in attempts to evaluate the processes occurring in vivo. A significant drawback of the cascade model is the impossibility to trace the interaction of cells carrying the tissue factor, platelets and plasma coagulation factors on their surface, since these conditions cannot be imitated. The cell theory, which has replaced the cascade theory, pays attention not only to the interaction of plasma coagulation factors, but also takes into account the role of platelets as important participants of coagulation processes. It is based on a four-stage reaction cascade that includes the following stages: initiation, amplification, propagation, and termination.The cell theory of hemostasis is able to reflect the complex process of interaction of all the links of hemostasis and answer questions related to the problems in patients with disorders of the coagulation system. The cell theory of hemostasis allows to reflect more precisely the processes of hemostasis in vivo and to interpret correctly the results of tests and pathophysiological mechanisms of disorders of the coagulation system. Global tests (thrombin generation assay, thromboelastography, thrombodynamics) used for hemostasis system evaluation are more complimentary with cell theory of hemostasis.

The mechanism of the triple aryne–tetrazine reaction cascade: theory and experiment

This article describes an experimental and computational investigation on the possible aryne reactivity modes in the course of the reaction of two highly energetic molecules, an aryne and a 1,2,4,5-tetrazine.

HEMOSTASIS BERLANDASKAN SEL HIDUP (IN VIVO)

Understanding of hemostasis has developed substantially in the last century from stasis in vitro to in vivo concept. Hemostasis theory develops from classic theory, discovery of coagulation factors leading to cascade/waterfall theory, as well as to in vivo cell based theory which explains the limitations of cascade theory. Phases of cell based hemostasis theory include initiation, amplification, propagation and termination with the role of tissue factor, platelet activation and coagulation factors in thrombin and fibrin synthesis. Common hemostasis tests used nowadays are important in evaluating bleeding risk but this matter still can not explain cell based hemostasis theory comprehensively so we need to find new tests to evaluate in vivo hemostasis.