Distinct intracellular lysozyme content in normal granulocytes and monocytes: a quantitative immunoperoxidase and ultrastructural immunogold study.

Using two different immunological methods, we performed a quantitative estimation of lysozyme (LZ) in normal mature granulocytes and monocytes. An immunoperoxidase reaction for LZ in granulocytes and monocytes of 10 healthy donors measured by a scanning microdensitometer as arbitrary units showed a significantly higher LZ content in granulocytes than in monocytes. An ultrastructural immunogold reaction (IGR) for LZ performed on post-embedded thin sections showed a higher number of total gold grains in neutrophilic granulocytes than in monocytes. In monocytic granules we found a high density of gold grains per micron 2, whereas in granulocytic granules lower values were obtained. In granulocytes, LZ was found in both primary myeloperoxidase (MPO)-positive and secondary MPO-negative granules, and in monocytes the granules showed weak MPO reactivity and high LZ content. Granulocytes previously subjected to phagocytosis of bacteria and latex particles showed release of LZ on degranulation inside the phagosome, whereas in monocytes the granules remained outside the phagosome and released LZ without degranulation. Our study demonstrated a significantly higher total LZ content in granulocytes, a higher granular LZ content in monocytes, and release of LZ from intact monocyte granules during phagocytosis.

Measurement of NADPH-ferrihemoprotein reductase content in sections of liver.

We developed a method for measuring the content of NADPH-ferrihemoprotein reductase in sections of liver. First, reductase in sections of rat liver was detected with the indirect immunoperoxidase reaction. Subsequently, specific absorbances were measured in the stained sections by microphotometry. Then, the resulting specific absorbances were converted into the reductase content in the sections using an apparent extinction coefficient obtained from a nitrocellulose binding assay. The average of the reductase content in hepatocytes in periportal, intermediate, and perivenous zones thus measured was consistent with the value in liver homogenates estimated by enzyme-linked immunosorbent assay. Therefore, the present method gave accurate measurement of the reductase content in the sections. Perivenous hepatocytes contained 1.5 times as much reductase (1.15 nmol/g liver, mean for five animals) as that in periportal hepatocytes (0.74 nmol/g liver). The reductase content in hepatocytes in the intermediate zone (0.93 nmol/g liver) was intermediate between values of the periportal and perivenous hepatocytes.

Modulation of alphafetoprotein synthesis in the early postimplantation mouse embryo

The visceral endoderm of mouse egg cylinders on the 7th and 8th days of gestation is divided into the visceral embryonic (VE) endoderm cell population which synthesizes alphafetoprotein (AFP), and the visceral extra-embryonic (VEX) endoderm population which does not synthesize AFP. Embryonic (E) and extra-embryonic (EX) ectoderm and visceral endoderm tissues were enzymically separated, reassociated in different combinations, and cultured in vitro for 48 h. The immunoperoxidase reaction on sections of cultured tissues showed that both VE and VEX endoderm cells synthesize high levels of AFP when cultured in isolation or in association with E ectoderm, but do not synthesize AFP when in close association with EX ectoderm. Both 7th and 8th day VEX endoderm cells synthesize detectable levels of AFP 12 h after isolation, and contain high levels by 24 h. It is concluded that both VE and VEX endoderm cells have the ability to synthesize AFP, but modulation of expression occurs through an inhibitory influence of the EX ectoderm.