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C E Bozzini

Publications and source records attributed to C E Bozzini.

At least 55 records · Page 3Linked to original sources
PubMed1983

Growth retardation in the early developing rat exposed to continuous hypobaric hypoxia.

Weanling male rats weighing 48.5 +/- 1.4 g were divided into two groups, hypoxic and normoxic. The former was placed into an altitude chamber and maintained at a pressure equivalent to 0.45 atm. (6 100 m) over a period of 23 days. The normoxic group was maintained at sea level conditions. Food intake, body weight, body length and tail length were recorded every day. Body weight gain in hypoxic rats was 35% of that seen in normoxic controls at the end of the experimental period. Body length gain was 55% and tail length gain was 59% of normal at the same time. The amount of food eaten by the hypoxic animals during the entire exposure period was 55% of that consumed by normoxic ones. The average daily caloric intake related to metabolic body weight (appetite quotient) of hypoxic rats was 60% of the normoxic control value. Efficiency of protein utilization was not significantly different between both groups of rats. These results indicate that exposure to hypobaric hypoxia induces growth retardation in the rat, which appears to be the result of a diminution in food intake because of a decreased appetite.

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PubMed1983

Enhanced erythropoiesis induced by hypoxia in hypertransfused, post-hypoxic mice.

The erythropoietic response, measured as RBC-59Fe uptake after 24 h-exposure to hypoxia, were determined in posthypoxic, "acute" and "chronic" hypertransfused, and posthypoxic-hypertransfused mice. Radioiron uptake by erythrocytes was about 25 times greater in post-hypoxic than in both types of hypertransfused mice. Posthypoxic-hypertransfused mice showed an erythropoietic response to hypoxia which was not significantly different from that of posthypoxic mice and about 20 times greater than those of "acute" and "chronic" hypertransfused mice. When hypertransfused mice were exposed to hypoxia before transfusions, a linear increase in 59Fe uptake values in response to hypoxia was observed with exposures between 6 and 30 h. No further increase was observed for exposures of 46 to 216 h. These results suggest a sensitization of the erythropoietin-producing organ(s) by hypoxia.

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PubMed1982

Erythropoietin formation during hypoxia in mice with impaired responsiveness to erythropoietin induced by irradiation or 5-fluorouracil injection.

Plasma erythropoietin levels during continuous exposure to hypobaric hypoxia in mice with marrow aplasia induced by whole body X-irradiation of 5-fluorouracil injection were higher than in control mice similarly exposed. There findings give support to the hypothesis that a relationship exists between erythropoietin production rate and erythroid responsiveness to the hormone.

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PubMed1982

Effect of indomethacin on red cell volume, iron kinetics and red cell survival in mice.

The time-response curve for hematocrit following s.c. injection of 400 microgram of indomethacin (IM) in a single dose into adult female mice showed a maximal depression at 3 days after IM with return to normal values by 11-12 days. The effect was dose-related showing a plateau with doses of IM above 400 microgram. The total circulating red cell volume was 68% of control and the plasma volume 117% of control 3 days after IM injection, recovering thereafter. At the same time, erythroid tissue iron uptake (microgram/h) was 67% higher in IM-treated than in non-injected mice. In mice with suppressed erythropoiesis due to daily i.p. injections of 0.06 microgram/g of actinomycin D, injection of IM induced a marked and rapid loss of cells from the circulation. Macroscopic and microscopic examinations of IM-treated mice at autopsy showed no indication of internal bleeding or other abnormalities. Serum non-conjugated bilirubin concentration was 2.2 times higher in IM-injected mice than in controls 3 days after drug administration. These results indicate that IM injection into mice in the experimental conditions reported here appears to induce a transient hemolytic state which is responsible for the depression of the red cell mass and the subsequent increase in the erythropoietic rate to compensate it. Both the decreased red cell volume and the increased plasma volume are responsible for the depression of the hematocrit value.

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PubMed1982

Ultrastructural changes in somatotropic cells induced by anemic or hypoxic hypoxia.

Somatotropic cells from three months old male mice, made hypoxic by either bleeding or exposure to 0.5 atm. barometric pressure in a decompression chamber, showed important ultrastructural changes when compared with normoxic controls, during the 36 hours that follow initiation of hypoxia. These changes were found to be similar for both types of hypoxic animals. An equivalent number of dark cells, cells with a swollen rough endoplasmic reticulum (RER), extremely granulated and degranulated, were successively--and in this order--seen along the experiment. Most of the observed differences between experimental and control animals appears as a magnification of the normal circadian rhythms. The degranulation rate, which probably reflects growth hormone (GH) secretion rate, was found to be about three times greater in hypoxic than in control mice. These findings indicate that a decrease in the red cell mass or its consequence (hypoxia), induce important ultrastructural variations in somatotropic (STH) cells, which may or not be specific.

Anemia↗
PubMed1981

Foetal haemopoiesis during the hepatic period. I. Relation between in vitro liver organogenesis and erythropoietic function.

Cultures of the hepatic bud, under different experimental conditions, show a direct relation between foetal age at the time of dissection and the further organogenesis of the explant. In cultures of the septum transversum plus hepatic bud--with or without splanchnic mesenchyme--obtained from embryos of four to 25 somites, the capacity for endodermic cells to differentiate into hepatocytes appears only in a small number of samples; whereas, in the hepatic bud from older embryos (26 to 40 somites), this differentiation occurs in all cases. The amount of time cultures were allowed to grow was important for hepatic organogenesis, as measured by cord-like organization of hepatocytes plus their storage capacity of glycogen. The possibility of the explants showing complete haemopoiesis was also a condition of foetal age at the time of explant. Haemopoiesis was not found in cultures from embryos of less than 25 somites. On the other hand, development of haemopoiesis did not show a direct relation to days of culture, since the peak of this activity was observed towards the third day in vitro. Most explants showed a generalized haemopoiesis (both interstitial and vascular) with a decay towards the sixth day. Endodermal cells of the hepatic bud were capable of both proliferation and differentiation into hepatocytes, even in those mesenchymes considered inadequate such as limb mesenchyme. In the latter case we were unable to find haemopoiesis at any time. The septum transversum, when cultured alone, did not contain haemopoietic cells.

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PubMed1981

Influence of growth rate on the ability of hypertransfusion induced plethora to suppress erythropoiesis in the growing rat.

To induce different rates of growth male rats 23 days of age were places on diets containing no protein or 20% casein for 10 days. They were then divided into three subgroups which were placed on diets containing 5%, 10% or 20% casein until the end of the experimental period (day 17). Adult rats were used as controls. Rats were hypertransfused on days 8 and 9 and RBC-59Fe uptake determined on day 17. Body weight was directly correlated with the casein content of the diet in the growing rats. RBC-radioiron incorporation was also influenced by the protein content of the diet in the young rats in spite of the fact that hematocrits were over 60% in all the animals. On the contrary, 59Fe uptake by erythrocytes was not related to diet composition in the adult rats. When radioiron incorporation values were plotted against growth rate it became evident that a close direct correlation exists between erythropoiesis and growth rate in transfused-polycythemic rats, indicating that the degree of suppression of red cell production provoked by hypertransfusion-induced plethora is dependent on the rate of growth of the animal, keeping with it an inverse relationship.

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PubMed1981

Inhibition by dexamethasone of erythropoietin-induced amplification of the erythropoietin-responsive cell compartment.

Erythropoietin-responsive cells (ERC) were reduced to very low levels in post-hypoxic polycythemic mice by intraperitoneal injection of 60 mg/kg-mouse of busulfan. Repeated injections of 5 units erythropoietin (Ep), 1, 2, and 3 days after busulfan repopulated the ERC compartment. Therefore, injection of a small test dose of Ep on day 5 induced a considerable wave of erythropoiesis. When busulfan-treated polycythemic mice received 5 mg of dexamethasone together with Ep injections they responded to the test dose of Ep with very minor increases in iron incorporation, which would indicate that a very small increase in the ERC population induced by Ep took place. These results suggest that the inhibitory action of dexamethasone on erythropoiesis is exerted not only by inhibiting the Ep-induced differentiation of ERC into proerythroblasts, but also by inhibiting the effect of the hormone on the amplification of the ERC compartment.

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PubMed1980

Mechanism underlying the inhibitory effect of dexamethasone on in vivo erythropoiesis.

The time-response curve for RBC-59Fe uptake following i.p. injection of 5 mg of dexamethasone into normal, non-polycythemic mice, shows a maximal depression (50% of normal) at 3 days after dexamethasone with return to almost normal values by 5 days. The effect is dose-related showing a plateau with doses of dexamethasone above 3 mg. The shape of the time-response curve indicates that the more mature cells in the erythron are not affected by dexamethasone and that the major effect of the steroid must be on earlier erythroid cells. Intravenous injection of dexamethasone 33 and 48 h after i.v. injection of erythropoietin in post-hypoxic polycythemic mice has no effect on the response to erythropoietin, suggesting that the early and late erythroblasts develop normally into erythrocytes. Injection of dexamethasone 13 h after erythropoietin is also ineffective, suggesting that the final steps of differentiation from erythropoietin responsive cells (ERC) to proerythroblasts are not affected. On the contrary, injection of dexamethasone 1 h after erythropoietin reduces by 60% the effective erythropoiesis, which can be attributed to a decrease in differentiation of ERC into proerythroblasts. These results indicate that the inhibitory action of dexamethasone on erythropoiesis is exerted on cells of the erythroid line before the stage of proerythroblast is reached.

Animals↗
PubMed1980

Foetal haemopoiesis during the hepatic period. III. Erythroid cell kinetics.

Serial sections of haemopoietic liver from 12 to 17 days old mice embryos were studied. The percentual values of cycling erythroid cells, located at vascular level, show a continuous decay through the entire hepatic phase of erythropoiesis. Since the 15th day onwards no differences were found in the cellular blood composition between the general circulation and the vascular channels of the central area of the growing lobes. Nevertheless, other more peripheric areas of the liver have a slowed decrease of circulating young cells, when compared with the former. On the contrary, in the marginal zones, interstitial proerythroblasts increase their percentual values towards the 13th day, coinciding with the moment on which they predominate all over other more mature demes. This increment is not explainable by self renewal only, since their mitotic indexes undergo a decay, which is unexpected in a growing population. Interstitial non erythroid cells seem not to play a role in the increment of proerythroblasts in the proliferating areas.

Animals↗
PubMed1979

Mechanism of the decreased erythropoiesis in the water deprived rat.

Radioiron uptake by erythrocytes, metabolic rate, erythropoietin formation during hypoxia and erythroid responsiveness to exogenous erythropoietin were determined in both starved and water deprived rats. The feed intake showed a marked and progressive reduction during water deprivation. The metabolic rates of rats deprived of either food of water declined progressively showing a 40% reduction 5d after water deprivation or starvation began. At this time, the 24 h red blood cells 59Fe incorporation was 85% lower in both starved and dehydrated rats than in normal rats. Plasma erythropoietin levels in response to hypoxia were approximately 50% decreased in both starved and dehydrated rats. Both polycythaemic starved and polycythaemic water deprived rats injected with human urinary erythropoietin showed a 75% decrease in 59Fe incorporation into erythrocytes when compared to control rats. It is suggested that depression of erythropoiesis during water deprivation in the rat depends on a reduced sensitivity to erythropoietin, possibly associated with decreased production of the hormone. Since water deprived rats drastically reduce feed intake it is suggested that secondary starvation is the principal cause of the decreased erythropoiesis induced in the rat by water deprivation.

Animals↗
PubMed1979

Foetal haemopoiesis during the hepatic period. II. Topographic histology.

Serial sections of mouse foetal liver, during the 9th and 16th days of gestation, were studied. The erythropoietic process starts in the central area of the growing hepatic lobes, and subsequently spreads towards the periphery. Each lobe passes successfully through an undifferentiated, proliferating and differentiating period, but does not proliferate and differentiate in a homogeneously synchronized way, since the onset of both histogenesis and erythropoiesis is delayed at the periphery, when compared with the central area. As a consequence, in sections it is possible to find three different zones, namely: marginal, which is the most undifferentiated; intermediate (transitional); and a central area, which is the most mature, since it is the first site where erythropoiesis arises. These zones are distinguishable not only by their cell distribution, but also by the biological behaviour of their elements, specially in the transitional areas between undifferentiated and proliferating zones. The hepatic lobes do not start their organogenesis at the same time; but those of them in which histogenesis is delayed, repeat courses of development similar to those previously organized. The first interstitial erythropoiesis appears in the central area, after the development of an organized network of sinuses, and in close relation to vascular channels. Dynamic images of immature blood cells, between interstitial and vascular spaces, suggesting passage through the endothelium, are often seen. These steps are followed, in a concentric form and spreading towards the periphery, by each hepatic lobe.

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