[The loop-like growth of the vessels and the embryonic morphogenesis of the human intraorganic circulatory system]. / Petlevidnyi rost sosudov i émbrional'nyi morfogenez vnutriorgannoi sistemy krovoobrashcheniia cheloveka.

Development of the vascular bed during embryogenesis in man occurs through loop-like growth of vessels appearing as multiplication, integration, and morphofunctional transformation of vessel loops. Growth of loops provides for the establishment of transport vessels in organs and tissues, and loop integration leads to the establishment of microcirculation with the appearance of connecting and major capillaries, from which true capillaries and capillary networks are formed. Precapillary arterioles and postcapillary venules can be identified topographically in the capillary networks. Formation of blood microcirculation system is complete when morphofunctional arrangement of integrated and nonintegrated loops takes place with the appearance of arterioles and venule collaterals and arterio-venule anastomoses in the vascular network.

In vivo and in vitro development of visceral adipose tissue in a nonhuman primate (Papio species).

We determined the development of the omental fat depot in a cross-sectional study of 242 baboons from birth to mature adulthood. The triglyceride content of the omentum increased during preweaning (birth to 4 months) and adolescence (2 to 5 years) and was associated with an increase in both fat cell number and size. Between weaning and 2 years of age omentum triglyceride mass decreased as a result of decreasing fat cell size, but fat cell number remained constant. After adolescence and up to 13 years of age, omental triglyceride mass and fat cell volume were stable, but fat cell number increased slightly in female baboons. We determined the in vitro potential of omental stromal vascular (S-V) cells from baboons at different stages of development to differentiate in a serum-free medium. Both the proportion of omental S-V cells that accumulated cytoplasmic lipid droplets and the induction of glycerol phosphate dehydrogenase (GPDH) activity were increased to the greatest degree in the presence of 1-methyl-3-isobutylxanthine, 2.0 nmol/L triiodothyronine (T3), 0.85 mumol/L insulin, and 1.0 mumol/L cortisol. Omental S-V cells from preweaning and adolescent baboons had a greater differentiation rate, GPDH activity, and triglyceride accumulation compared with cells from postweaned infants and mature adults. In summary, most of the growth of the baboon omentum occurs during the preweaning and pubertal periods of life, and omental S-V cells isolated from animals during these periods retain a greater potential to differentiate in vitro.

[Ansiform growth of blood vessels as a fundamental principle of angiogenesis]. / Petlevidnyi rost sosudov kak osnovopolagaiushchii printsip vaskulogeneza.

Succession in formation of blood bed of the greater omentum has been studied in human fetuses (42), in premature children with the body mass of 900-2,500 g (108) and in mature children up to 3 years of age (48). Vasculogenesis in the organ of 12-week-old fetuses and in older ones is demonstrated as an ansiform growth of the vessels. In the vascular loop the afferent geniculum contains differential signs of the arterial, and the different one--the venous part of the blood bed. The top of the loop contains a growth bud and is a zone of growth; it ensures proliferation of the vascular loops and their spreading in the growing tissue mass in the organ. This principle of growth provides a ramified system of arteries and veins, reiterating the course and branching of each other. Against the background of the ansiform growth of the vessels capillary formation begins, at first connective, and then true capillaries are formed. Basing on the data obtained a conception of vasculogenesis in ontogenesis is formulated. Its main stages are--period of ansiform growth of the vessels and period of capillary formation. In the latter should be distinguished appearance of connective capillaries and formation of truely capillary network.

Comparison of growth, neovascularization, and enzymatic function of fetal intestinal grafts in the omentum and renal capsule.

Fetal tissues are less immunogenic and may be a useful donor source for organ transplantation. This report compares the fate of fetal small bowel segments transplanted in the omentum and renal capsule of recipient syngeneic rats. Two-centimeter segments of fetal jejunum and ileum were obtained from 26 donor 19-day gestational age rat fetuses and transplanted into the subrenal capsule (n = 35) and omentum (n = 40) in syngeneic Fisher rats (weight, 150 g) as free grafts. No immunosuppression was used. At 2 weeks posttransplantation, the recipient rats underwent laparotomy and the grafts were evaluated for viability, growth, enzymatic function, and revascularization. Viable grafts were identified in 27 of 35 renal capsule grafts and 34 of 40 omental grafts. The order of magnitude of fetal growth in the omentum for jejunum was 16 +/- 10 versus ileum 23 +/- 9 (NS). However, in the renal capsule, ileal growth (15 +/- 6) was significantly greater than jejunum (8 +/- 5; P less than .01). Growth for both jejunal and ileal segments was greater in the omentum (P less than .02). The lumen of all omental grafts remained patent; however, 26 of 27 renal grafts had cystic dilatations and areas of obstruction. Microfil casts of the specimens showed vascular connections (neovascularization) between the graft and omentum, a normal serosal vascular pattern, and many submucosal capillary-like vessels. Maltase activity was measured in fetal grafts and compared with control pups bred on the same date as the donor animals. The grafts had a higher maltase level 33.4 +/- 34.6 mumol/min/g than controls 8.3 +/- 2.0 (P less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferative activity of macrophages in the greater omentum of the mouse in relation to the early postnatal development of the vascular structures.

The rudimental omentum in newborn mice presents itself as a thin, poorly vascularized membrane covering the stomach. Imprints and whole mounted preparations of the omental membrane of mice from seven different inbred strains, aged 1-10 days, were made and sequential morphological changes were described. It was found that omentum of suckling mice contains numerous foci or colonies of mononuclear phagocytes (omental macrophages). These cells reveal a high proliferative activity when examined 1 hr after exposure of tritiated thymidine. The labeling index in the population of omental macrophages is variable, ranging in individual mice from less than 5% to 25%. This wide variation is a nonrandom phenomenon. It was found in all seven strains of mice and depends mainly on the age of the mouse. Two possible interpretations are as follows: Some interrelation exists between the intensity of the proliferative activity of omental macrophages and the development of vascular and lymphoid structures that are characteristic for the omentum of adult mice. Omental macrophages originate from local precursors that are not dependent on the bone marrow.

Ontogeny of lymphatic structures in the pig omentum.

The development of lymphoid populations in the omentum majus during the prenatal and postnatal life of the pig was studied. T lymphocytes, monocytes and mast cells were first found on the 40th day of gestation. B lymphocytes appeared on the 72nd day of gestation when the first macrophage aggregates were formed. Macrophages appeared to be the prerequisite for the formation of dense lymphatic areas (DLA's). At later stages T cells were observed only in the omentum of germfree pigs. DLA's of conventional pig omentum are filled exclusively with B cells.

[Histogenesis of the omental milk spot of the mouse (author's transl)].

The mouse omental milk spots can be classified into two types, type I and II. The type I spots are seen in the margin of the fatty tissue along the omental vessels, and the type II spots are scattered on the omental peritoneum. In this study, histogenesis of the two types of milk spots was examined with the light and electron microscope. 1. Milk spots are not yet observed at birth, but macrophages are already intermingled with mesenchymal cells along the omental vessels and within the omental peritoneum. 2. Fat cells first appear along the omental vessels at 1 to 2 days of age and they then form fatty tissue at 3 to 5 days. Mononuclear cells such as lymphocytes, lymphoid cells and macrophages are scattered within the fatty tissue. At 6 to 10 days capillary network is developed along the margin of the fatty tissue, and lymphocytes, lymphoid cells and macrophages are accumulated along capillaries. Thus type I milk spots are formed. Lymphocytes and lymphoid cells are frequently seen also within the capillary lumens. They are sometimes seen crossing the capillary walls. Macrophages in the deeper zone of milk spots are generally small, but macrophages in the superficial zone are large and well differentiated in appearance. 3. The proportions of constituent cells in type I milk spots were examined at various ages. In spots in early life, macrophages, lymphoid cells and lymphocytes are relatively few, occupying 7 to 8% in proportion, respectively. Then lymphocytes increase in number with age, and they are more than 50% after 1 month of age. Lymphoid cells remain almost unchanged in proportion, being 7 to 11%. Macrophages constitute 2 to 3% after 1 month. 4. Type II milk spots appear later than type I spots, and they are first seen at 12 days of age, especially on the dorsal layer of the omentum. They then increase in number with age. 5. Functional significance of the milk spots was discussed in relation to their histogenesis.

The mast cell: II. Distribution and maturaiton in the peritoneal cavity of the young rat.

In rats aged 1/2 to 60 days, the development of the mesentery and omentum involves a substantial modification of the inital lymphatic supply of these membranes and the postnatal development of 'milk spots' of the omentum. In both membranes, mast cells are scarce at birth but progressively increase in number and maturation with increasing age of the rat. In the paravascular zones of the mesentery, mast cells are particularly associated with lymphatic vessels, rather than with blood vessels. Mast cells are also scarce at birth in the free peritoneal fluid, but increase progressively in number with increasing age of the rat. The initial population consists of about 90% stage 1 cells and 10% stage 2. Progressive maturation results in successive waves of stage 2 cells during the 2nd week, of stage 3 cells during the 2nd and 3rd weeks, and of stage 4 cells during the 3rd and 4th weeks. These and other results are interpreted to indicate that mast cells in free peritoneal fluid probably arise from free precursor cells rather than by migration from the peritoneal membranes.