Size regulation of double and half embryos in the mice musculus

Genetic chimeras made by aggregating early mouse embryos have many uses in developmental biology and have also provided insights into embryonic growth regulation. There is an indication that the embryo can regulate for an increase in size because although aggregation chimeras are twice as big as normal embryos when made, they are born of normal size. Upward regula..... tion of size reduced embryos is also possible. Half embryos made by the isolation or destruction of one of the blastomeres of a 2-cell embryo are also born of normal size. Little is known about the timing or the mechanism of this size regulation. In this study, the timing of size regulation in double and half embryos was clearly established by comparison of cell numbers derived from serial reconstruction of light microscope sections of control and experimental embryos. It was shown that size regulation in double embryos occurred around 6dl6h and in half embryos by 7dOh. Size regulation occurred in all tissues at the same time indicating a single control mechanism for the entire embryo. More detailed examination of the growth of double embryos revealed that size regulation occurred by alteration in cell cycle length~ No excessive cell death was found in double embryos compared to the controls and continuous labelling with [3H] thymidine showed no large non-dividing cell population in double embryos. However, a comparison of the mitotic index of double and control embryos after colcemid treatment, revealed a large difference between the two around 5dl6h to 6d16h. During this period, control embryos underwent a proliferative burst not shown by the double embryos. The mechanism for cell cycle control is not clear; it may be intrinsic to the embryo or determined by the uterine environment. Evidence was found suggesting that differentiation in the postimplantation embryo was cell number dependent. The timing of differentiative events was examined in half, double and control embryos. Proamnion formation, which occurs prior to size regulation, occurs at the same cell number but at different times in the three groups of embryos. However mesoderm which appears after size regulation was seen at the same time in all grollps of embryos.

Captain Lewis Warrington and others : memorial of Lewis Warrington, Captain in the U.S. Navy, (in behalf of himself and the officers and crew of the U.S. sloop-of-war Peacock); praying that the one half of the proceeds of the Epervier and goods which went into the officers and crew of said vessel, it having been decreed to them by the United States court as captors. April 26, 1848.--

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Portrait of Young Woman by I. H. Lewis, Photographer [n.d.]

An unidentified young Black woman is featured in this cabinet card portrait by photographer I. H. (Isaac) Lewis, of Toronto. The photographer's name and address is stamped in gold lettering on the lower front of the card. The address is given as 106 1/2 Queen St. W., Toronto. This cabinet card was in the possession of Iris Sloman Bell, of St. Catharines, Ontario. The Bell - Sloman family relatives include former Black slaves from the United States who settled in Canada.Isaac H. Lewis was a photographer in Toronto from 1886 - 1900. Source: Phillips, Glen C. The Ontario photographers list (1851-1900). Sarnia: Iron Gate Publishing Co., 1990.

Cabinet Card Portrait Photographed by I. H. Lewis, of Toronto [n.d.]

A cabinet card portrait of an unidentified woman by I. H. Lewis, a photographer

Wrestling Card - Strangler Lewis

The wrestler's name is Strangler Lewis and the number stamped on the reverse of the card is 471.

Indenture Land Sold by Thomas Clark to Lewis Clement, 1817

Indenture regarding land sold by Thomas Clark of Stamford Township to Lewis Clement of Niagara Township. The land includes 50 acres in the northern half of Lot 58 in Niagara Township - instrument no. 5356, January 17, 1817.

Indenture between Arthur Lambert and Lewis Lambert

Indenture between Arthur Lambert or his attorneys or executors to Lewis Lambert of the County of Lincoln for 60 acres of land in the Township of Niagara in Lots no. 154-156, Jan. 1, 1829.

Indenture between Samuel D. Woodruff and Lewis Better

Indenture regarding articles of agreement between Samuel D. Woodruff of St. Catharines and Lewis Better of the Township of Gainsborough for lot no. 3 in the township of Gainsborough, Apr. 23, 1896.