Difference between magnesium and manganese ions in modification of effect of catecholamine on adenylate cyclase system in Ehrlich ascites tumor cells

Involvement of divalent cations was examined in the activation of catecholamine sensitive adenylate cyclase in Ehrlich ascites tumor cells. In the presence of various concentrations of either Mg2+ or Mn2+, both basal and norepinephrine-stimulated, adenylate cyclase activities were measured. Both activities were gradually increased with the increase in Mg2+ concentration. On the other hand, with Mn2+, both activities were maximum at the low (2.5 mM) concentration, and decreased at the highest concentrations, the decrease being marked in the norepinephrine-stimulated activity. Similar difference between the two divalent cations was also observed in the effect on the binding of the beta-adrenergic ligand to the membrane receptor.

Hemopoiesis in cultures of the bone marrow cells from genetically anemic mice

An attempt was made to reproduce the in vivo situation of the hemopoiesis in genetically anemic mice in vitro. Cultures of the bone marrow cells from W/Wu, Sl/Sld and control (+/+) mice revealed that all of the hemopoietic stem cells in these mice could be maintained in vitro as well. Similar results were also obtained with the spleen cell cultures. Since these anemic mice have near normal levels of committed progenitor cells, and pluripotent stem cells in Sl/Sld mice, and a subnormal level of functional blood cells sufficient for the survival of the mice, there should be a slow and constant hemopoiesis, under normal conditions. Such a slow but steady production of hemopoietic cells appears to be well reproduced in vitro.

Mechanism of hypercholesterolemia in arteriolipidosis-prone rats (ALR)

The cholesterol metabolism of a newly established model for atherogenesis, named arteriolipidosis-prone rats (ALR), selected from spontaneously hypertensive rats (SHR), was investigated in comparison with a substrain of SHR (B) (nonarteriolipidosis-prone rats) and the normotensive control. Wistar-Kyoto (WK) rats. Serum cholesterol of ALR was significantly lower than that of WK. Uptake of labelled serum cholesterol by the isolated liver cells at 37 degrees C was higher in ALR than in WK. The data for SHR (B) fell in between these two. On the other hand, on feeding a cholesterol diet, serum cholesterol increased in the order WK, SHR (B) and ALR, with the highest being ALR. The absorption of cholesterol in ALR was about twice as great as in WK and SHR (B).

Precursor of mast cells fixed in the skin of mice

The presence and origin of mast-cell precursors fixed in the skin tissue of mice were investigated. Giant granules of beige (C57BL/6-bh'/bg', Chediak-Higashi syndrome) mice were used to distinguish different populations of mast cells. Pieces of the skin were grafted from the intact WBB6F1 (WB X C57BL/6)F1-+/+ mice into the back of the WBB6F1-+/+ mice which had been irradiated and injected with bone marrow cells of C57BL/6-bg'/bg'leads to +/+ chimeras). Although the number of mast cells in the skin grafts decreased after the transplantation, the mast-cell precursors circulating in the bloodstream of bg'/bg' leads to +/+ chimeras (bg'/bg' type) did not seem to enter into the skin grafts, because most of mast cells were of +/+ type after the recovery of mast-cell number to pregrafting levels. As a considerable proportion of +/+-type mast cells was labeled with 3H-thymidine, the recovery of mast-cell number in the grafts was attributed to the proliferation and differentiation of +/+-type precursor cells fixed in the skin tissue of the donor. On the other hand, the skin of WBB6F1-W/Wv mice seemed to be depleted of fixed precursors, because most of mast cells were of bg'/bg'-type in skin grafted from WBB6F1-W/Wv mice to bgJ/bgJ leads to +/+ chimeras. Since the fixed precursor cells which proliferate and differentiate into mast cells after skin grafting may be transferred to WBB6F1-W/Wv mice by bone marrow transplantation, such precursor cells seem to have been derived from the bone marrow.

Absence of increase of histidine decarboxylase activity in mast cell-deficient W/W mouse embryos before parturition

The histidine decarboxylase (L-histidine carboxylase, EC 4.1.1.22) activity of whole W/W mouse embryos, which are devoid of mast cells, remained very low and did not show the rapid increase before birth (17-20 days of gestation) seen in wild-type +/+ embryos. During the same period, the histamine content also remained very low and no mast cells were detected in the W/W embryos, in the contrast to the large increase in both histamine content and number of mast cells in wild-type embryos. These findings imply that the histamine in embryos is largely derived from mast cells. In +/+ mice, histidine decarboxylase activity decreased rapidly soon after birth without concomitant decrease in histamine content or number of mast cells, suggesting that the enzyme activity in mast cells is regulated by some unknown mechanism.

Spleen colony-forming cell as common precursor for tissue mast cells and granulocytes

The haematopoietic stem cells which produce colonies in the spleen of irradiated mice (CFU-S) can differentiate into erythrocytes, granulocytes, megakaryocytes and B lymphocytes. Although mast cell precursors are known to be present in the bone marrow, spleen, fetal liver and peripheral blood of mice, the relationship between the mast cell precursor and CFU-S has remained unclear. We have now made use of mice of two mutant genotypes to determine whether or not the tissue mast cell is a progeny of CFU-S. Giant granules of beige (C57BL/6-bg/bg, Chediak-Higashi syndrome) mice can be used for identification of the origin of both tissue mast cells and granulocytes, and WBB6F1-W/Wv mice are useful recipients because they lack tissue mast cells owing to a defect in mast cell precursors. We injected the cells from a single spleen colony into each WBB6F1-W/Wv mouse and demonstrated directly that the tissue mast cell is a progeny of CFU-S.

Hemodynamic responses to bilateral lesions of the nucleus tractus solitarii in spontaneously hypertensive and normotensive rats

Systemic and regional hemodynamic responses to bilateral lesions of the nucleus tractus solitarii (NTS) were studied in alpha-chloralose-urethane anesthetized American Wistar rats (NR), Wistar-Kyoto rats (WKY), and spontaneously hypertensive rats (SHR) by microsphere methods. After NTS lesions, arterial pressure rose by virtue of increased total peripheral resistance in each strain. Cardiac output was lower in NR and WKY, but not in SHR. In all strains, vasoconstriction was nonuniformly distributed among the systemic vasculatures: hepatosplanchnic, renal, and carcass (i.e. skin, skeletal muscle, bone, fat) vascular resistances were higher, but cerebral and coronary vascular resistance remained unchanged. There were some differences, however, in regional vascular responses to NTS lesions among these strains: carcass vasoconstriction was predominant in NR; it was less evident in SHR; and the WKY responses were intermediate. These results indicate that, although systemic hemodynamic responses were similar in these strains, and the reflex inhibition of central sympathetic outflow is not evidently deteriorated in SHR, the regional hemodynamics (i.e., hepatosplanchnic and renal vasculatures) in the SHR demonstrated greater arteriolar constriction.

Adjuvant chemo-endocrine therapy for androgen-dependent mammary tumor in mice

About 500 male DS mice grafted with androgen-dependent Shionogi carcinoma 115 (SC115) were used. When the tumor diameter reached about 20 mm (approximately 25 days after transplantation), excision of the tumor and/or castration were carried out. The injection of cyclophosphamide (80 mg/kg body weight X 3 at 7-day intervals) was started from the day after excision. In mice with excised tumor, adjuvant chemo-endocrine therapy was the most effective treatment examined; cumulative 120-day mortalities after transplantation of tumors in non-treated, adjuvant endocrine therapy, adjuvant chemotherapy and adjuvant chemo-endocrine therapy groups were 91%, 29%, 21% and 0%, respectively. Castration induced development of clusters of androgen-independent cancer cells in androgen-dependent SC115 tumor. In mice without tumor excision, the chemo-endocrine therapy was again the most effective treatment, though 86% of mice died by the 120th day after tumor transplantation. These findings suggest the usefulness of adjuvant chemo-endocrine therapy for achieving complete remission in hormone-dependent tumors.

Migration of stromal cells supporting mast-cell differentiation into open wound produced in the skin of mice

Mutant mice of Sl/Sld genotype are depleted of tissue mast cells due to a defect of stromal cells which may support the differentiation of mast cells. Number of mast cells did not increase in the skin of Sl/Sld mice grafted on the back of the congenic +/+ mice even 50 weeks after the transplantation. When the wound was produced in the central part of the Sl/Sld skin graft, a considerable number of mast cells appeared within the scar resulting from the wound. The appearance of mast cells in the scar was shown to be due to the differentiation of circulating precursors into mast cells rather than the simple migration of mature mast cells by using giant granules of bgJ/bgJ mice as a marker for newly-formed mast cells. Therefore, the present results seem to suggest that normal stromal cells of the +/+ host origin migrate into the wound produced in the grafted skin of Sl/Sld mice and support the differentiation of circulating precursors into mast cells.

Effect of serial passage in female nude athymic mice on androgen dependency of Shionogi carcinoma 115

When Shionogi carcinoma 115 (SC115, an undifferentiated medullary carcinoma showing a compact cell pattern and containing androgen receptor) was transplanted into male and female DS mice, it grew only in males. In contrast with this strict androgen dependency in DS hosts, SC115 tumors grew in male and female nude athymic (BALB/c-nu/nu) mice. Although most of the tumors developing in female nude mice were composed of spindle-shaped cells and did not contain androgen receptor, about 5% of tumors in female nude mice retained morphological and biochemical characteristics of the original SC115 tumor. Such a tumor was serially transplanted in female nude mice. Although no significant changes were detectable in histological and chromosomal features and in androgen receptor values, the growth speed in female nude mice accelerated and became comparable to the growth speed of the original SC115 tumor in intact male DS mice. However, this subline of SC115 tumor showed a marked androgen dependency when reinoculated into male and female DS mice after 14 passages in female mice nude mice in spite of its relative androgen independency in nude hosts. Therefore, the present results seem to suggest that the immunological status of the hosts may affect the hormone dependency of tumors.

Structure of slow-reacting substance of anaphylaxis (SRS-A)

To elucidate the chemical structure of slow-reacting substance of anaphylaxis from rat (SRS-A rat), SRS-A rat were purified by the method of Orange with modification using DEAE-Sephadex A-25 chromatography. Ultraviolet absorption spectrum of purified SRS-A rat indicated the presence of conjugated triene. Arylsulfatase B degradation products and HCl degradation products were subjected to analysis by a gas chromatography and mass spectrometry and a thin layer chromatography. Products obtained by arylsulfatase b catalysis contained 5,6-dihydroxy-7,9,11,14-eicosatetraenoic acid. HCl degradation products showed the presence of glycine, glutamic acid and cysteic acid. Furthermore, the analysis of anhydrous hydrazine degradation products of SRS-A rat and of HCl hydrolyzed products of dinitrophenylated SRS-A rat revealed the presence of glycine at C-terminal and glutamine acid at N-terminal. The study of the substrate specificity of arylsulfatase B against various materials including SRS-A rat suggested the presence of sulfone in SRS-A rat. The molecular ion peak of SRS-A rat sodium salt was observed at m/e 680 in field desorption mass spectrum of SRS-A rat. On the basis of these data, we identified the structure of SRS-A rat as [gamma]glutamyl-4(5-hydroxy-7,9,11,14-eicosatetraenoic acid-6-yl)-4,4-dioxyocysteinyl] glycine.

The effects of steel mutation on testicular germ cell differentiation

The effects of artificial cryptorchidism and its surgical reversal on spermatogenesis were examined in germ cell mutant, S1/+ and wild type, +/+, mice. In cryptorchid testes no difference was found between S1/+ and +/+ mice in the number of undifferentiated type A spermatogonia. The activity of type A spermatogonia in mutant mice appeared normal as judged by its mitotic cell number and DNA synthesis. The surgical reversal of cryptorchidism resulted in regenerative differentiation of mature germ cells in both types of mice, but the pattern of cellular differentiation in the mutant testes was completely different from that of the wild type testes. At two steps of cellular differentiation, intermediate or type B spermatogonia and spermatid, the numbers of cells were much smaller in the S1/+ testes than those in the +/+ testes. The steel gene was therefore suggested to exert its effects on the differentiation of type A spermatogonia to intermediate or type B spermatogonia, on meiotic division and/or the survival rate of these cells, but not on the undifferentiated type A spermatogonia or stem cells.

Reference sample microsphere method: cardiac output and blood flows in conscious rat

Validation of the reference sample method (RSM) in the rat was accomplished by: 1) simultaneous measurement of cardiac output (CO) by the RSM and electromagnetic flowmetry method in ether-anesthetized open-chest Wistar rats, and 2) determination of systemic and regional hemodynamic reproducibility in conscious rats following three serial injections of microspheres. The optimal sampling time and sampling rate were determined in several CO states. The results indicate that: 1) 200 or more microspheres contained in the reference sample result in an accurate determination of CO, 2) almost 100% of the microspheres are trapped by tissues with in 20 s of cessation of the microsphere injection, 3) the hemodynamic steady state is affected only under low cardiac output conditions at a high sampling rate (1.211 ml/min), 4) three repeated injections of microspheres in conscious animals do not alter systemic hemodynamis, and 5) the reproducibility of regional blood flow distribution is good in all organs except the liver, stomach, spleen, and skin (third application). These data indicate that the RSM is reliable, providing reasonable accuracy and reproducibility of systemic and regional hemodynamics in the rat.

Coincidental development of forestomach papilloma and prepyloric ulcer in nontreated mutant mice of W/Wv and SI/SId genotypes

A double gene dose of mutant alleles at either the W or Sl locus produces the pleiotropic effects of anemia, sterility, lack of hair pigmentation, and lack of tissue mast cells. Coincidental development of forestomach papilloma and prepyloric ulcer was observed in about 40% of nontreated (WB X C57BL/6) F1-W/Wv mice raised in our laboratory. The stomach lesions of the W/Wv mice could be detected at the 15th day after birth, and such lesions never appeared in the W/+, Wv/+, and +/+ littermates maintained under the same laboratory conditions. Since the stomach lesions were also observed in (WC X C57BL/6) F1-Sl/Sld mice purchased from The Jackson Laboratory, phenotypes common to both W/Wv and Sl/Sld mice seem to play an essential role in the spontaneous development of the forestomach papilloma and prepyloric ulcer.

[Pharmacological properties of trapidil: comparison with other coronary vasodilators (author's transl)]

Effects of trapidil and other coronary vasodilators on retrograde blood flow in acute coronary-ligated dogs, isolated large and small coronary arteries of pig, platelet aggregation, biosynthesis of prostacyclin in isolated aortic rings and hyperlipemia in quails were investigated. Trapidil showed an increase in retrograde blood flow while dipyridamole, nifedipine, diltiazem and dilazep did not. Trapidil and nitroglycerin relaxed large coronary arteries, while dipyridamole, diltiazem, dilazep and adenosine relaxed small arteries. Trapidil, dipyridamole, diltiazem and aspirin protected against the secondary phase of ADP-induced platelet aggregation in guinea-pig platelet rich plasma more effectively than did nifedipine and dilazep. Trapidil and aspirin protected only against rabbit platelet aggregation as induced by arachidonic acid. Moreover, only trapidil protected against platelet aggregation as induced by prostaglandin G2-thromboxane A2 mixture. Trapidil and dipyridamole enhanced the platelet aggregation protection of prostacyclin. Trapidil also facilitated biosynthesis of prostacyclin more markedly than did the other drugs. Trapidil increased serum content of HDL cholesterol and significantly lowered serum content of triglyceride and the ratio of LDL cholesterol to HDL cholesterol in hyperlipemic quails. Dipyridamole, diltiazem, nifedipine and dilazep, however, showed little effect.

Effect of androgen depletion on postoperative regrowth of androgen-dependent and -independent Shionogi carcinomas in mice

About 350 castrated male DS mice given testosterone propionate (TP, 100 micrograms/mouse/day) were grafted with androgen-dependent SC115 tumor or androgen-independent tumors (NHD with positive receptor; NHF with negative receptor). After 20 or 15 days, most of the developed tumors were excised and the mice were divided into 3 groups. TP injection was continued in one group and TP was stopped immediately or 20 days after the excision in the other groups. The cumulative 120-day mortality after transplantation of SC115 tumor into mice was significantly lower in the immediate androgen removal group (10%, 6/59) than in the androgen-injected group (59%, 51/87) or the delayed androgen removal group (42%, 19/45). The cumulative mortalities in mice with androgen-independent NHD and NHF tumors in the immediate androgen removal groups (97 and 91%, respectively) were similar to those in the androgen-injected groups (90 and 95%, respectively). All non-operated and TP-injected mice grafted with SC115 and androgen-independent tumor died due to the tumors within 50 and within 30 days after the transplantation, respectively. These findings suggest the usefulness of adjuvant endocrine therapy for preventing the recurrence of hormone-dependent tumors.

pH-dependent adhesion of piliated Corynebacterium renale to bovine bladder epithelial cells

The adhesion of Corynebacterium renale 115 to bovine bladder epithelial cells was studied with two clones of the bacteria, piliated (P+) and nonpiliated (P-). The percentage of the cells with attached P+ bacteria was greater than that of the cells with attached P- bacteria, and the number of attached P+ bacteria was higher than that of the P- bacteria. The adhesion of P+ bacteria was found to be pH dependent, which was supported by the following facts: the number of attached bacteria was high at a pH above 7.6 and low at a pH below 6.8; the adhering P+ bacteria were eluted immediately after the pH was decreased from 7.4 to 6.4; and the P+ bacteria unattached at pH 6.4 adhered to the cells immediately after the pH was increased to pH 7.4. The adhesion of P+ bacteria was inhibited by anti-pilus antiserum. The adhesion was not inhibited by amino acids or sugars, including mannose, and was not influenced by Ca2+ and Mg2+. P- bacteria hardly attached to the epithelial cells, irrespective of the pH and other factors.

Effect of oxidized oil on lipogenic enzymes

Male Wistar rats were fed for 4 wk on diets containing 2% oxidized corn oil. Liver tissue was then studied to determine the effect of feeding peroxidized oil on lipogenic enzymes. Although substances which reacted with thiobarbituric acid increased in liver microsomes and mitochondria with increasing peroxide values of the dietary corn oil fed, the activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase in liver were unchanged. However, when rats were fed for 2 wk on diets containing 10% fat, of which 0.5, 5 or 10% was unoxidized corn oil and the remainder was hydrogenated beef tallow filler, the lipogenic enzyme activities and also the liver triglyceride levels were observed to decrease with increasing amounts of dietary corn oil. Therefore, although a synthetic diet containing corn oil was easy to oxidize spontaneously, the reductions of lipogenic enzymes in rats fed the diet would not have been caused by lipid peroxides but by unsaturated fatty acids themselves.

Effect of corn oil feeding on lipid peroxidation in rats

Three groups of male rats were maintained on 10% fat diets containing 0.5, 5 or 10% corn oil or olive oil with 80--400 mg DL-alpha-tocopherol per kilogram. After 4 weeks on such regimens, TBA (thiobarbituric acid) values in serum, liver mitochondria and microsomes, and adipose tissue increased with rising amounts of dietary corn oil. TBA values in rats fed the 10% corn oil diet were reduced with the increase of dietary tocopherol but were still higher than the corresponding values of the 10% olive oil and 0.5% corn oil groups. When the liver microsomes were incubated with Fe3+-ADP and NADPH, the relative chemiluminescence emission in the visible region with the peroxidative cleavage of endogenous lipid was higher in the 5 and 10% corn oil groups than in the 0.5% group. On the other hand, when oxidized corn oil was given orally to rats with thoracic lymph fistula, TBA-reacting substances were recovered in thoracic lymph, but iodometric peroxide was undetectable. Therefore, TBA-reacting substances in rats fed the corn oil diets could have originated from the oxidative product of linoleic acid metabolism and also from the diet.

Spontaneous stomach ulcer in genetically mast-cell depleted W/Wv mice

Histamine has been implicated in the pathogenesis of gastroduodenal ulcers. Since mast cells contain a considerable amount of histamine as well as heparin and other biologically active substances, it seems reasonable to speculate that they are involved in this process. In fact, development of gastroduodenal ulcers was reported in dogs with mastocytoma, and an increase in mast-cell number was described in the vicinity of human gastroduodenal ulcers. Y.K. et al. have recently found that the number of mast cells in a unit length of the skin of W/Wv mutant mice is less than 1% of the value for the congeneic +/+ mice and that no mast cells are detected in the intestinal canal of W/Wv mice. Therefore, this mutant mouse was used to investigate the role of mast cells in the induction of gastroduodenal ulcers. As a preliminary experiment, we examined the stomach and duodenum of W/Wv mice without any treatments. Unexpectedly, we found the spontaneous development of perforating stomach ulcers in W/Wv mice, suggesting that mast cells do not necessarily have aggravating effects on the production of stomach ulcers.

Development of androgen-independent spindle cell tumors from androgen-dependent medullary Shionogi carcinoma 115 in androgen-depleted nude mice

When Shionogi carcinoma 115 (SC115, undifferentiated medullary carcinoma showing compact cell pattern and containing androgen receptor) was transplanted into male and female DS mice, it grew only in males. In contrast to this strict androgen dependency in DS hosts, tumors composed of spindle-shaped cells appeared in more than 80% of cases when SC115 tumor was inoculated into female or castrated male nude athymic (BALB/c-nu/nu) recipients. These spindle cell tumors neither contained cytosol androgen receptor nor showed biologically defined androgen dependency. As spindle cell tumors could be serially transplanted in DS mice but not in BALB/c-+/+ mice and as the original SC115 (medullary carcinoma showing a compact cell pattern) tumor and the spindle cell tumor had many identical chromosome abnormalities, these two types of tumors seem to have a common origin in spite of their morphological, biochemical, and biological differences. Since spindle cells could not be detected histologically in SC115 tumors maintained in intact male DS mice, the present results seem to suggest that SC115 cells may change their morphological, biochemical, and biological characteristics within one passage in androgen-depleted nude athymic mice.

Distribution of mast-cell precursors in hematopoeitic and lymphopoietic tissues of mice

Two experimental systems were used to investigate the origin of precursor cells which differentiate into tissue mast cells in vivo. (a) Increase of mast cell number was examined in the skin, stomach, cecum, and mesentery of genetically mast cell-depleted WBB6F1 (WB X C57BL/6)-W/WV mice after the injection of various hematolymphoid cells of congenic +/+ mice. (b) Appearance of mast cells with giant granules was studied in irradiated C57BL/6-+/+ mice after the injection of lymphoid cells of C57BL/6-bgJ/bgJ (beige, Chediak-Higashi syndrome) mice. Concentrations of mast cell precursors in the thymus, lymph node and Peyer's patch were less than 0.1% of the concentration in the bone marrow. Neither treatment of donor bone marrow cells with anti-Thy-1.2 serum and complement nor thymectomy of the recipient mice affects the development of mast cells in the skin, stomach, cecum, and mesentery. Moreover, the number of mast cells increased to normal level when the skin of WBB6F1-W/WV mice was grafted on the back of nude athymic (BALB/c-nu/nu) mice. These results indicate that mast cell precursors are derived from hematopoietic tissues rather than lymphopoetic ones and that the differentiation of the precursor cells does not depend on T lymphocytes or the thymus.

Clonal nature of mast-cell clusters formed in W/Wv mice after bone marrow transplantation

We have recently found that the number of mast cells in the skin of adult W/Wv mice is less than 1% of that observed in congeneic +/+ mice, and that no mast cells are detected in other tissues of W/Wv mice. After the transplantation of bone marrow cells from congeneic +/+ mice, the number of mast cells in the skin, stomach, caecum and mesentery of the W/Wv mice increased to levels similar to those of the +/+ mice. Study of the mast-cell number in the W/Wv mice at various times after transplantation suggested to use that mast cells might develop in groups, particularly in the skin and mesentery. In this report, we have attempted to elucidate the possible clonal origin of such mast-cell clusters from a single precursor cell, using giant granules of beige (C57BL/6-bgJ/bgJ, Chediak-Higashi syndrome) mice as a marker to identify the origin of the mast cells (Fig. 1). We found that when WB-W/+xC57BL/6-Wv (WBB6F1)-W/Wv mice were injected with a mixture of bone marrow cells from beige C57BL/6 mice and normal C57BL/6 mice, more than 95% of mast-cell clusters consisted of either beige-type cells alone or normal-type cells alone. We conclude, therefore, that the cluster of mast cells originated from a single precursor cell.

Presence of mast cell precursors in peripheral blood of mice demonstrated by parabiosis

The presence of mast cell precursors in peripheral blood was examined. The beige C57BL/6 (bgj/bgj, Chediak-Higashi syndrome) mouse was parabiosed with the normal C57BL/6 mouse. Mast cells containing giant granules and originating in the beige partner appeared in the normal parabiont. A comparable proportion of normal-mouse-type mast cells developed in the beige parabiont as well. In spite of the low radiosensitivity of mature mast cells, irradiation of the normal parabiont reduced the proportion of normal-mouse-type mast cells appearing in the beige partner. It was concluded, therefore, that the precursors of mast cells can migrate through the bloodstream.

Local development of mast cells from bone marrow-derived precursors in the skin of mice

A mechanism to control development of mast cells was investigated in mice. Although mast cells in the skin of normal C57BL/6 mice were still of host type 290 days after irradiation and injection of bone marrow cells from beige (Chediak-Higashi syndrome, C57BL/6 bgJ/bgJ) mice, donor-type mast cells with giant granules appeared after painting of methylcholanthrene on the dorsal skin. Since donor-type mast cells appeared only at the painted portion of the skin, with an increase in the labeling index of such donor-type mast cells with 3H-thymidine, proliferation and differentiation of bone marrow-derived precursors of mast cells seem to be controlled locally. Although the morphologic feature of marrow-derived precursors was not identified, the finding that all fibroblasts cultured from the methylcholanthrene-treated skin were of host type may exclude the possibility that fibroblasts are the precursors of mast cells.

Hematologic changes during spleen colony development in nonirradiated mice

The mechanism of spleen colony formation in nonirradiated mice was investigated. When the spleen cells of C57BL mice immunized against CBA-T6T6 mice were injected into the nonirradiated BT6F1 (C57BL X CBA-T6T6) hybrid mice, the number of hematopoietic stem cells (CFU-S of C57BL mouse origin that settled in the spleen of the BT6F1 mice continued to decrease in the first 9 days and then started to increase, with a doubling time of about 36 hr. Colonies were detected on the surface of the spleen 16-22 days after the cell injection. The slower appearance of spleen colonies in nonirradiated mice (compared with 6-10 days in the irridiated animals) appears to be due to retarded start of differentiation and to the prolonged doubling time of CFU-S in non-irradiated mice.