Inhibition of mouse parenchymal cells proliferation by mosquito larvae extract.

As it is known, some cell populations of mosquito Aedes aegypti larvae do not proliferate. This fact suggests the existence of some mitosis inhibiting factor. We have assayed the effect of mosquito larvae crude extract on 85 C3HS young male mice (25 +/- 1 days old) and the effect of the dialyzed fraction of the same extract on 47 partially hepatectomized C3HS adult male mice. The injection was performed at 16:00 hour (before the raising of the DNAS curve) and the controls were made at 08:00/16, 12:00/20 and 16:00/24 (Time of Day/Time Post Injection). Colchicine arrested metaphases of nephrocytes, hepatocytes, sialocytes (submaxillary glands) and enterocytes were controlled. The mitotic rate was significantly inhibited in hepatocytes, sialocytes and enterocytes in young growing mice, and in hepatocytes in partially hepatectomized adult mice. We conclude that TGF-beta, actually found in insects, or alternatively some other known or unknown factor, could be responsible for the results observed in the present experiments.

Action of plasma and liver extract from adult mice on the mitotic activity of young mouse liver.

Inbred C3HS male mice, standardized for periodicity analysis were used. A hundred and seventy 25 +/- 2 days old mice were injected at 16:00 hs with saline, plasma or liver extract from 27 mice 90 days old. Controls were made at 08/16, 12/20, 16/24, 08/40, 12/44, 16/48, 08/64, 12/68 and 16/72 (time of day/time post-injection). The mitotic activity of the hepatocytes and litoral cells were determined. The injection of small doses of extract and plasma inhibits the mitotic activity of hepatocytes during the first and second following days. A compensatory wave appears in the third day. The extract inhibits the mitotic activity of litoral cells in the first day of control only, whereas the plasma inhibits this variable in the second and third day.

Action of plasma and liver extract from adult mice on the mitotic activity of young mouse liver.

Inbred C3HS male mice, standardized for periodicity analysis were used. A hundred and seventy 25 +/- 2 days old mice were injected at 16:00 hs with saline, plasma or liver extract from 27 mice 90 days old. Controls were made at 08/16, 12/20, 16/24, 08/40, 12/44, 16/48, 08/64, 12/68 and 16/72 (time of day/time post-injection). The mitotic activity of the hepatocytes and litoral cells were determined. The injection of small doses of extract and plasma inhibits the mitotic activity of hepatocytes during the first and second following days. A compensatory wave appears in the third day. The extract inhibits the mitotic activity of litoral cells in the first day of control only, whereas the plasma inhibits this variable in the second and third day.

Variations in DNA synthesis and mitotic indices in hepatocytes and sinusoid litoral cells of adult intact male mouse along a circadian time span.

Variations of DNA synthesis (DNAS) and mitotic indices along a circadian time span are described in the hepatocyte and sinusoid litoral cell populations of adult intact male mouse liver. Standardized (light from 0600 to 1800) mice were killed in groups of six to nine animals, every 2-4 hr along a circadian time span. Hepatocytes show significant peaks in the synthesis of DNA and the mitotic activity at 0200 and 1400, respectively. These results correspond to those previously described by us in young immature liver, regenerating liver and hepatomas. The phase differences between these peaks and the differences between their absolute values are discussed. Also considered are the practical consequences of our findings for experimental design. The curve of DNA synthesis of sinusoid litoral cells show a peak at 0200. The mitotic index show a bimodal waveform with peaks at 0800 and 2000. The existence of four different cell populations composing the so called sinusoid litoral cells and also the migration into and out of the liver of some macrophages considered as litoral (Kupffer) cells in our counts, makes interpretation of the curves somewhat complicated and deserves further analysis.

The circadian optimal time for hepatectomy in the study of liver regeneration.

Standardized (light from 0600 to 1800) C3HS mice, hepatectomized at different circadian stages, were killed at 1400 (the peak time of mitotic activity in intact mice). The higher values of mitotic index were those of mice operated at 1400, 48 hr before. The curve of mitotic activity of the regenerating liver of mice operated at 1400 and that of mice operated at 0200 (an opposite time in the circadian stage) are, both, grossly in phase with the curves of mitotic index in young and adult mice liver. The amplitude of the first peak of mitotic activity in mice operated at 0200 was dramatically lower than that of animals operated at 1400. The same applies to hepatocytes as well as to the sinusoid litoral population of cells. It is concluded that 1400 hr, as contrast to 0200 hr, is an optimal time for hepatectomy if one wants to obtain the highest mitotic index first peak during regeneration in a normal phase position (the position of the mitotic index peak in the liver of normal young and adult mice).