CHAPTER 2: LITERATURE REVIEW
Every individual biological trait requires an evolutionary and proximate explanation. The proximate explanations representing the “how,” usually employ conventional tools, e.g., molecular biology, biochemistry, and cell biology to examine the anatomy, ontogeny, and physiological traits of a modern-day organism. The evolutionary explanation which represents the “when and why” usually combine fossil record methodology, DNA sequencing, and comparative morphology to explain the phylogenetic history of a particular trait and how that trait provides fitness advantage for adaptation and survival of a species throughout millennia. This research study is concerned with the angiopoietin protein group essential for the development and functioning cardiovascular system. Cardiovascular biology as a discipline employs proximate mechanisms to explain how blood vessels and their endothelial lining develop and function Or how the heart generates force or even how the heart and the blood vessels become dysfunctional during a disease like cancer, heart disease, and sepsis. Little research has been done concerning the evolutionary mechanisms of the cardiovascular systems in living organisms, to explain phenomena such as why some circulatory systems are open while others are closed, or why we have vascular endothelial cell lining in some systems and not in others. Answering these questions is essential in providing insights in design constrains for drugs, and selective pressures inherent of the human physiology and the consequent vulnerability to disease. The prime goal of this review is to explore the origin of the blood vascular system and endothelium in relation to ancient protein families, that is, the angiopoietin protein families, particularly angiopoietin-1 and angiopoietin-2 growth factors which regulate endothelial and vascular function. We hold that examination of the angiopoietin evolution, and bioinformatics analysis of the data generated will help in the development of more effective modulators of angiopoietin action for use as potential new drugs that target the ANG-TIE pathway (currently in clinical development for oncological and ophthalmological applications. Existing evidence indicates that the blood vascular system first appeared in an ancestor of the triploblastic close to 600 million years ago, as a means to adapt to the time-distance constraints of diffusion. The endothelium then evolved in an ancestral vertebrate 540–510 million years ago to maximize flow dynamics and barrier function, and/or to localize immune and coagulation functions.
Angiogenesis refers to the growth of blood vessels and is a prime biological process that controls embryonic development with numerous applications in the study and resolution of fatal human diseases. It is, therefore, a process of neovascular formation from pre-existing blood vessels during embryogenesis, adult tissue homeostasis, and carcinogenesis, (Katoh, 2013, page 763). Angiogenesis proceeds through angiogenic sprouting, proliferation, endothelial cell migration, and vessel destabilization/ stabilization. Angiogenesis research is centered on the vascular endothelial growth factor (VEGF) and the VEGF receptor system, that is, Tie receptors and their angiopoietin (Ang) ligands (second vascular tissue-specific receptor Tyr kinase system). These receptors are vital in the Ang-Tie signaling process that is essential during embryonic vessel assembly, disassembly and maturation of the endothelial lining of the blood vessels (Davis et al., 1996. pp. 1166). It also functions as a key controller of adult vascular homeostasis. All angiopoietins bind with similar likeness to a cell-specific endothelial tyrosine-protein kinase receptor. For example angiopoietin small proteins (cytokines), are responsible for controlling micro-vascular and macro-vascular permeability, through vasoconstriction and vasodilation, which happens by signaling smooth muscle cells surrounding the affected blood vessels, (Saharinen, Eklund,
Chlamydia Trachomatis and Blindness
When one hears “Chlamydia,” they will probably think of the sexually transmitted infection. Even when doing a simple web search on “Chlamydia,” the given results with the most hits will point to the sexually transmitted infection (STI). However, there is so much more than the STI. Chlamydia trachomatis also causes blindness. C. trachomatis is the cause of both the STI and blindness in people (Chlamydia trachomatis L2c (n.d.).
The organism Chlamydia trachomatis is an obligate intracellular parasite. Its Gram status is Gram-negative (Bach, C. (2011, April 29). Its morphology is Bacilli. The taxonomy of C. trachomatis starts with its Kingdom being Bacteria. Its phylum is Chlamydiae. Its class is also Chlamydiae. Its order is Chlamydiales. It belongs to the Chlamydiaceae Family. Its genus is Chlamydia and species is trachomatis. C. trachomatis has no motility and also no flagella. It requires no oxygen. It has a symbiotic relationship with its main host of human beings (Chlamydia trachomatis L2c. (n.d.)).
In 1907, two men by the name of Ludwig Halberstaedeter and Stanislaus von Prowazek observed the organism on the eye surface of an infected orangutan. In China 1957, Feifan Tang first cultured C. trachomatis in the yolk sac of eggs. “Chlamys” is Greek for “cloak draped around the shoulder.” This is used to describe the occurrence of inclusions that are draped around the nucleus of the infected cell. With C. trachomatis being an obligate intracellular parasite, it was thought to be a virus at first. It is unable to replicate outside of the host cell (Fagerberg, K., Smith, L.,