robert hooke showed that animals are made of cells.
who showed that animals are made of cells?
robert hooke
cells, which were once invisible to the naked eye, were first seen in 17th century europe with the invention of the compound microscope. robert hooke was the first person to term the building block of all living organisms as "cells" after looking at cork. the cell theory states that all living things are made up of cells. the theory also states that both plants and animals are composed of cells which was confirmed by plant scientist, matthias schleiden and animal scientist, theodor schwann in 1839. 19 years later, rudolf virchow contributed to the cell theory, arguing that all cells come from the division of preexisting cells. in recent years, there have been many studies which question the cell theory. scientists have struggled to decide whether viruses are alive or not. viruses lack common characteristics of a living cell, such as membranes, cell organelles, and the ability to reproduce by themselves. viruses range from 0.005 to 0.03 micrometers in size whereas bacteria range from 1-5 micrometers. modern day cell biology research looks at different ways to culture and manipulate cells outside of a living body to further research in human anatomy and physiology, to derive treatments and other medications, etc. the techniques by which cells are studied have evolved. advancement in microscopic techniques and technology such as fluorescence microscopy, phase-contrast microscopy, dark field microscopy, confocal microscopy, cytometry, transmission electron microscopy, etc. have allowed scientists to get a better idea of the structure of cells.
cell biology
in 2009, a study showed that only ssea-3+ cells generate induced pluripotent stem (ips) cells in human fibroblasts. in 2011, it was suggested that ips cells are generated only from muse cells. when the technique for generation of ips cells was applied to both muse and non-muse cells, ips cells were successfully generated only from muse cells. in contrast, non-muse cells did not show elevation in sox2 and nanog, master genes of pluripotent stem cells, even after receiving the four yamanaka factors. these results support the elite model of ips cell generation rather than the stochastic model. divergent from their muse cell origin, ips cells showed tumorigenecity. since muse cells are originally pluripotent without tumorigenic activity, what the yamanaka factors newly conferred to muse cells was not 'pluripotency' but tumorigenic activity. these results collectively suggest that only preexisting cells with promising pluripotency can be programmed into ips cells.
muse cell