The effect of splenectomy on bone marrow haematopoiesis in mice.

Splenectomy was performed in strain H mice. Erythrocyte macrocytosis and an increase in the reticulocyte, leucocyte and thrombocyte count were found in the peripheral blood of splenectomized animals; only the erythrocyte count fell in the first 3 weeks after splenectomy. Changes in the myelogram during the first weeks after splenectomy were characterized by an increase in the proportion of cells of the erythrocytic and lymphocytic series. The stem cell count in the bone marrow (determined after Till and McCulloch) was slightly elevated on the 8th day after splenectomy, but in subsequent weeks was rather lower than the control group values. Whatever the post-splenectomy interval at which bone marrow was taken from splenectomized mice, there was no significant difference in the transplantation effect of bone marrow cells on white and thrombocyte haematopoiesis. Bone marrow transplantation was found have a stimulant effect only on the reticulocyte count and the sooner bone marrow was collected after splenectomy, the more pronounced the effect. Changes in the myelogram and splenogram of irradiated mice to which the bone marrow cells of splenectomized mice had been transplanted were relatively small.     

Changes of bone marrow cell and peripheral blood cell counts in newborn mice

Differential bone marrow cell and peripheral blood cell counts in new-born mice from zero to twenty-one days of age were investigated. In the bone marrow, erythroblasts rapidly increased whereas granulocytic cells decreased with time. The G/E ratio was 6.7 on day zero and 0.5 on day four, and as the G/E ratio of adult mice is normally from 0.8 to 2.4, these values would be the highest and lowest respectively for the whole life span of a mouse. In the peripheral blood, MCV decreased each day, closely matching the changes in the Price-Jones curves. The results of erythrocyte area measurements indicate that the larger the erythrocyte area, the earlier in days of age it disappeared and the shorter its life span.     

A quantitative study on the recovery of rat marrow erythropoietic cells after experimental suppression of erythropoiesis by repeated doses of cyclophosphamide

Rat erythropoiesis was experimentally depressed by repeated doses of cyclophosphamide (CY) or by restriction of food consumption and the diagnostic value of quantitative haematology examinations of rat marrow erythroid morphology was evaluated. A slight depression of rat erythropoiesis (following a dose of 5 mg/kg/day) as well as a higher one (15 mg/kg/day) and the following recovery were determined by a quantitation of marrow erythroid morphology and by peripheral reticulocyte counts, yet a lower validity of peripheral erythrocyte and marrow relative erythroid cell counts was obtained; erythrocyte counts did not change even after a high depletion of marrow erythroid cells. The restriction of food consumption led to a similar depression of rat marrow erythropoiesis as that observed after CY administration. Our data may suggest that the quantitation of marrow erythroid morphology and peripheral reticulocyte counts are desirable in haematological examinations in preclinical safety evaluations performed on rats provided a new drug administered in repeated doses can be cytotoxic.     

Regulation of extracellular volume and interstitial fluid pressure in rat bone marrow

The volume and fluid pressure characteristics of the intact bone marrow is incompletely understood. We used microspheres and lipoproteins for measurements of intravascular volume (IVV) and EDTA for interstitial fluid volume (IFV) within the rat bone marrow. Interstitial fluid pressure (IFP) was determined with micropipettes connected to a servo-controlled counter-pressure system. Both the microspheres and the lipoproteins yielded estimates of IVV of approximately 1 ml/100 g. After a brief reactive hyperemia, IVV increased to 2.5 ml/100 g, whereas IFV decreased with approximately 1.5 ml/100 g, so that total extracellular volume did not change. Baseline bone marrow IFP was 9.7 mmHg. The hyperemia led to a transient twofold increase in IFP, whereas a marked blood loss decreased IFP by almost one-half. These novel data suggest that extracellular volume and IFP within the bone marrow can be measured with tracer methods and the micropuncture technique. The responses of IVV, IFV, and IFP during changes in blood flow to the bone marrow suggest a tight regulation and are thus compatible with those for a low-compliant tissue.     

Population dynamics of "null" and Thy1lo lymphocytes in mouse bone marrow: genesis of cells with natural killer cell lineage characteristics.

The population dynamics of "null" small lymphocytes lacking B and T lineage markers in mouse bone marrow have been examined using a combination of immunolabeling and hydroxyurea (HU) deletion techniques. The binding of the B lineage-associated mAb, 14.8, and anti-Thy1.2 to bone marrow cells has been detected radioautographically. Null cells lacking 14.8 and Thy1.2 determinants (14.8- Thy1-) formed a substantial subset (12-14%) of bone marrow small lymphocytes, representing 0.5 x 10(6) cells per femur (2-3% of nucleated cells). HU treatment revealed an exceptionally rapid turnover of the null small lymphocyte population (T1/2, 7.5 hr) compared with 14.8+ cells (T1/2, 20.5 hr) and Thy1+ cells (T1/2, 53 hr). Small lymphocytes bearing low intensities of Thy1 (Thy1lo) were also rapidly renewed (T1/2, 28 hr) whereas those with high intensities of Thy1 (Thy1hi) were renewed only slowly (T1/2, 123 hr). During ontogeny, null small lymphocytes first appeared in the fetal liver by Day 11 and the fetal spleen by Day 16, but increased rapidly in the bone marrow in early postnatal life. Double immunolabeling techniques demonstrated that 10% of null small lymphocytes in the bone marrow expressed NK1.1 antigen, while larger proportions bound to tumor (YAC.1) cells in vitro and displayed Fc receptors. The NK1.1-bearing fraction of null small lymphocytes in bone marrow was depleted by HU treatment only after an initial delay. NK1.1 was also expressed on subsets of Thy1lo cells and Thy1hi cells. The results have revealed the continuous production in mouse bone marrow of null and Thy1lo small lymphocytes, totaling 1-3 x 10(7) cells/day and 1.2 x 10(6) cells/day, respectively. The findings suggest that the large-scale production of null lymphocytes in mouse bone marrow includes the genesis of NK lineage cells which express NK1.1 and Thy1lo during a period of terminal maturation.     

Reticulocyte changes after experimental anemia and erythropoietin treatment of horses.

Availability of recombinant human erythropoietin (EPO) has facilitated use to enhance red blood cell production, and therefore aerobic performance, in human and equine athletes. Recombinant human EPO promotes growth and differentiation of equine erythroid precursor cells, but in some horses repeat administration induces immune interference with endogenous EPO resulting in fatal anemia. Although blood reticulocyte parameters acquire unique changes in humans treated with EPO, with manual enumeration methods, horses were not considered to release reticulocytes from the bone marrow into circulation, even under severe erythropoietic stress. The goals of this study were to determine whether reticulocytes could be detected and characterized in horses that are anemic or have been treated with EPO using a modern hematology analyzer. Anemia was induced in six horses by removal of 30 ml of blood/kg of body wt over 24 h. After 28 days, the horses were treated twice with 55 U/kg of EPO (Eprex), and after 65 days they were treated thrice with 73 U/kg of EPO. Blood samples were analyzed with the ADVIA120 instrument every 3-5 days and bone marrow samples 7 days after anemia and EPO treatments. Analysis of blood reticulocyte parameters by ANOVA in a randomized complete block design determined that anemia and EPO induced significant (P < or = 0.05) increases in red cell distribution width and reticulocyte mean cell volume. Parameters changed only after EPO treatment were cellular hemoglobin concentration mean, mean cell volume, reticulocyte concentration, proportion of macrocytic reticulocytes, and reticulocyte cellular hemoglobin. These findings indicate that horses under erythropoietic stress and after EPO treatment release reticulocytes with unique characteristics into circulation.     

Development of diabetogenic T cells from NOD/Lt marrow is blocked when an allo-H-2 haplotype is expressed on cells of hemopoietic origin, but not on thymic epithelium

Diabetes is a T cell-mediated process in NOD/Lt mice, with a major genetically recessive component of susceptibility linked to homozygous expression of the unique H-2g7 MHC haplotype. Heterozygous expression of the H-2nb1 haplotype derived from the NON/Lt strain confers diabetes resistance both in (NOD x NON)F1 hybrids and in NOD mice congenic for the H-2nb1 haplotype. However, diabetes resistance is abrogated in F1 hybrids by NOD/Lt bone marrow reconstitution. To establish whether the generation of beta cell autoreactive T cells from NOD/Lt bone marrow-derived precursors required at least heterozygous expression of the H-2g7 haplotype on thymic epithelium, adolescent thymectomized (NOD x NON)F1 mice were implanted with neonatal NON/Lt thymus grafts before lethal radiation and reconstitution with NOD/Lt bone marrow. Peripheral T cells maturing through this ectopic thymic implant exclusively expressed the NOD H-2g7 haplotype and were tolerant to H-2nb1 skin grafts. Nevertheless, diabetes developed in 32% of the NON/Lt thymus-grafted chimeras vs 38% of the sham-thymectomized NOD bone marrow chimeras. Thus, homozygous expression of the diabetes-resistant H-2nb1 haplotype on thymic epithelium failed to block development of a diabetogenic T cell repertoire. To examine if expression of H-2nb1 on hemopoietically derived APC could alter the diabetogenic potential of NOD/Lt marrow, diabetes-resistant NOD.NON-H-2nb1 congenic mice were mated with NOD/Lt mice to produce NOD-H-2g7/H-2nb1 heterozygous recipients. These were lethally irradiated and reconstituted with either NOD/Lt marrow alone, NOD.H-2nb1 homozygous congenic marrow alone, or a 1:1 mixture of the two marrow populations. By 25 wk of age, all of the MHC heterozygous recipients of NOD.NON-H-2nb1 marrow remained diabetes-free whereas 75% of the MHC heterozygous recipients of NOD/Lt marrow developed diabetes. A striking decrease in diabetes was observed when T cell precursors derived from NOD/Lt marrow interacted with H-2nb1 gene products on hemopoietically derived APC, inasmuch as only 7% of the MHC heterozygous recipients reconstituted with a 1:1 mixture of NOD/Lt and NOD.NON-H-2nb1 marrow developed diabetes. Peripheral leukocytes in all reconstitution classes expressed the MHC phenotype(s) of the marrow donor(s). Skin grafting confirmed that all reconstitution classes of MHC heterozygous recipients were tolerant to the H-2nb1 haplotype.(ABSTRACT TRUNCATED AT 400 WORDS)     

B lymphocyte production in the bone marrow of mice with X-linked immunodeficiency (xid)

CBA/N mice carry an X-linked recessive immunodeficiency (xid) gene manifested by the absence of a B lymphocyte subpopulation, but the manner in which the xid gene exerts its effect on B lymphocyte development is unknown. The production of B lymphocytes in the bone marrow of CBA/N mice has now been compared with that of normal CBA/J mice by using two in vivo assays: immunofluorescence stathmokinetic studies measured pre-B cell proliferation, whereas radioautographic [3H]thymidine labeling was used to evaluate small lymphocyte turnover. Although the total cellularity of CBA/N mouse bone marrow was greater than normal, the absolute number of marrow small lymphocytes, pre-B cells, and B lymphocytes were all similar to those in CBA/J controls. Furthermore, in the bone marrow of CBA/N mice, the proliferation rate of pre-B cells, calculated from their rate of entry into mitosis, and the turnover rate of small lymphocytes, derived from their rate of [3H]thymidine labeling, were not significantly different from those seen in nondefective mice. The present findings that pre-B cell proliferation and small lymphocyte production proceed at similar rates in the bone marrow of xid and normal mice suggest that the xid gene does not act at the level of primary B cell genesis in the bone marrow. The findings are in accord with the view that the xid gene produces a maturation block or a functional abnormality among B lymphocytes in the peripheral lymphoid tissues rather than the deletion of a sublineage of B lymphocytes in the bone marrow.     

Abrogation of hybrid resistance to bone marrow engraftment by graft-vs-host-induced immune deficiency

Lethally irradiated F1 mice, heterozygous at the hematopoietic histocompatibility locus Hh-1, which is linked with H-2Db, reject bone marrow grafts from H-2b parents. This hybrid resistance (HR) is reduced by prior injection of H-2b parental spleen cells. Because injection of parental spleen cells produces a profound suppression of F1 immune functions, we investigated whether parental-induced abrogation of HR was due to graft-vs-host-induced immune deficiency (GVHID). HR was assessed by quantifying engraftment of H-2b bone marrow in F1 mice with the use of splenic [125I]IUdR uptake; GVHID, by the ability of F1 spleen cells to generate cytotoxic T lymphocytes (CTL) in vitro. We observed a correlation in the time course and spleen cell dose dependence between loss of HR and GVHID. Both GVHID and loss of HR were dependent on injection of parental T cells; nude or T-depleted spleen cells were ineffective. The injection of B10 recombinant congenic spleens into (B10 X B10.A)F1 mice, before grafting with B10 marrow, demonstrated that only those disparities in major histocompatibility antigens that generated GVH would result in loss of HR. Thus, spleens from (B10 X B10.A(2R]F1 mice (Class I disparity only) did not induce GVHID or affect HR, whereas (B10 X B10.A(5R))F1 spleens (Class I and II disparity) abrogated CTL generation and HR completely. GVHID produced by a class II only disparity, as in (B10 X B10.A(5R))F1 spleens injected into (B6bm12 X B10.A(5R))F1 mice, was also sufficient to markedly reduce HR to B10 bone marrow. This evidence that GVHID can modulate hematopoietic graft rejection may be relevant to the mechanisms of natural resistance to marrow grafts in man.     

Nitric oxide inhibition decreases bleomycin-detectable iron in spleen,bone marrow cells and heart but not in liver in exercise rats

The possible role of nitric oxide on the exercise-induced changes in bleomycin-detectable iron (BDI) in the liver, spleen, bone marrow cells and heart was investigated. Female Sprague—Dawley rats were randomly assigned to four groups: S1 (Sedentary), S2 (Sedentary + L-NAME [N-nitro-L-arginine methyl ester]), E1 (Exercise) and E2 (Exercise + L-NAME). Animals in the E1 and E2 swam for 2 h/day for 3 months. L-NAME in the drinking water (1 mg/ml) was administrated to rats in the S2 and E2 groups for the same period. At the end of the 3rd month, nitrite and nitrate (NOx), BDI and non-heme iron (NHI) contents in the liver, spleen, bone marrow cells and heart were measured. The ratio of BDI/NHI was calculated. The exercise induced a significant increase in NOx and BDI contents and/or BDI/NHI ratio in the spleen, bone morrow cells and heart. Treatment with L-NAME, an inhibitor of NOS, led to a significant decrease in NOx and an increase in BDI levels and BDI/NHI ratios in these tissues. The correlative analysis showed that there is significantly positive correlation between NOx levels and BDI contents and/or BDI/NHI ratios in the spleen, bone marrow cells and heart. These results suggest that the increased nitric oxide might be one of the reasons leading to the increased BDI levels in these tissues in the exercised rats. In contrast to the above tissues, in the liver, exercise led to a significant decrease rather than increase in BDI levels and BDI/NHI ratios with a significant increase in NOx contents. Treatment with L-NAME led to a significant increase in BDI levels and BDI/NHI ratios and a decrease in NOx contents in the tissue. These findings plus the results reported by others imply that nitric oxide might have an inhibitory effect on BDI in the liver.     

Hyperglycemia does not alter state 3 respiration in cardiac mitochondria from type-I diabetic rats

The possible role of nitric oxide on the exercise-induced changes in bleomycin-detectable iron (BDI) in the liver, spleen, bone marrow cells and heart was investigated. Female Sprague-Dawley rats were randomly assigned to four groups: S1 (Sedentary), S2 (Sedentary + L-NAME [N-nitro-L-arginine methyl ester]), E1 (Exercise) and E2 (Exercise + L-NAME). Animals in the E1 and E2 swam for 2 h/day for 3 months. L-NAME in the drinking water (1 mg/ml) was administrated to rats in the S2 and E2 groups for the same period. At the end of the 3rd month, nitrite and nitrate (NOx), BDI and non-heme iron (NHI) contents in the liver, spleen, bone marrow cells and heart were measured. The ratio of BDI/NHI was calculated. The exercise induced a significant increase in NOx and BDI contents and/or BDI/NHI ratio in the spleen, bone morrow cells and heart. Treatment with L-NAME, an inhibitor of NOS, led to a significant decrease in NOx and an increase in BDI levels and BDI/NHI ratios in these tissues. The correlative analysis showed that there is significantly positive correlation between NOx levels and BDI contents and/or BDI/NHI ratios in the spleen, bone marrow cells and heart. These results suggest that the increased nitric oxide might be one of the reasons leading to the increased BDI levels in these tissues in the exercised rats. In contrast to the above tissues, in the liver, exercise led to a significant decrease rather than increase in BDI levels and BDI/NHI ratios with a significant increase in NOx contents. Treatment with L-NAME led to a significant increase in BDI levels and BDI/NHI ratios and a decrease in NOx contents in the tissue. These findings plus the results reported by others imply that nitric oxide might have an inhibitory effect on BDI in the liver.     

First report of a glutamine-rich antifungal peptide with immunomodulatory and antiproliferative activities from family Amaryllidaceae

This represents the first report of purification of a glutamine-rich antifungal peptide from family Amarylliaceace. The peptide, designated as nartazin, was purified from the bulbs of the Chinese daffodil Narcissus tazetta var. chinensis by means of ion-exchange chromatography and affinity chromatography. Its molecular mass was 7.1kDa, as determined by SDS-PAGE and gel filtration. Nartazin stimulated proliferation of mouse splenocytes and bone marrow cells but inhibited proliferation of leukemia L1210 cells. It also inhibited translation in a cell-free rabbit reticulocyte lysate system. The sequence of its first 20 N-terminal residues was characterized by an abundance of glutamine. The peptide possessed antifungal activity on four phytopathogenic fungi. Its activity was retained after incubation with bovine trypsin and chymotrypsin (enzyme: substrate ratio 1:10 w/w) at 37 degrees C for 1h but was attenuated after treatment with proteinase K. The data revealed its pronounced resistance to proteolytic digestion.     

The Role of Bone Marrow Cells in the Phenotypic Changes Associated with Diabetic Nephropathy

The aim of our study was to investigate the role of bone marrow cells in the phenotypic changes that occur in diabetic nephropathy. Bone marrow cells were obtained from either streptozotocin-induced diabetic or untreated control C3H/He mice and transplanted into control C3H/He mice. Eight weeks after bone marrow cell transplantation, renal morphologic changes and clinical parameters of diabetic nephropathy, including the urine albumin/creatinine ratio and glucose tolerance, were measured in vivo. Expression levels of the genes encoding α1 type IV collagen and transforming growth factor-β1 in the kidney were assayed. Our results demonstrated that glucose tolerance was normal in the recipients of bone marrow transplants from both diabetic and control donors. However, compared with recipients of the control bone marrow transplant, the urinary albumin/creatinine ratio, glomerular size, and the mesangial/glomerular area ratio increased 3.3-fold (p < 0.01), 1.23-fold (p < 0.01), and 2.13-fold (p < 0.001), respectively, in the recipients of the diabetic bone marrow transplant. Expression levels of the genes encoding glomerular α1 type IV collagen and transforming growth factor-β1 were also significantly increased (p < 0.01) in the recipients of the diabetic bone marrow transplant. Our data suggest that bone marrow cells from the STZ-induced diabetic mice can confer a diabetic phenotype to recipient control mice without the presence of hyperglycemia.     

Effect of a neutrophilia-inducing tumor on hemopoietic stem cells in mice

The influence of neutrophilic stimulation on hemopoietic stem cells was studied in mice with tumor-induced neutrophilia. Transfusions of marrow cells from normal and neutrophilic tumor-bearing mice into lethally irradiated normal and tumor-bearing mice were performed. The number and the erythroid:granuloid (E:G) ratio of day 7 colonies in the recipient spleens and bones as well as the size of spleen colonies of recipient animals were determined. The E:G ratio of spleen and bone marrow colonies between normal and tumor-bearing mouse recipients and the number of spleen colonies did not differ significantly in either experiment. However, spleen colonies which developed in tumor-bearing irradiated mice were significantly larger than those which developed in normal recipients in both experiments. These studies indicated that while the line of differentiation taken by hemopoietic stem cells was not affected by the neutrophilic influence of the tumor, the tumor-bearing host environment appeared to enhance proliferation of transfused stem cells and/or their descendants. The stimulators of granulocytopoiesis in this model of neutrophilia appear to act on a population of progenitor cells more mature than the stem cells capable of forming 7-day colonies in the spleen and bone marrow of irradiated recipient mice.     

Reticulocyte and micronucleated reticulocyte responses to gamma irradiation: dose-response and time-course profiles measured by flow cytometry

A flow cytometric, anti-CD71-based method was used to measure peripheral blood reticulocyte and micronucleated reticulocyte frequencies in response to (137)Cs total body irradiation (TBI). In three independent experiments, groups of five female C57BL/6N mice were irradiated at graded doses up to 3 Gy, and peripheral blood specimens were collected at 43 h post-irradiation. Whereas the frequency of reticulocytes declined over the range of doses studied, micronucleated reticulocyte incidence was observed to increase in a dose-dependent manner up to 1 Gy. At doses greater than approximately 1 Gy, micronucleated reticulocyte frequencies declined with increasing exposure. These responses were highly reproducible, with significant effects on reticulocyte and micronucleated reticulocyte frequencies observed for the lowest dose studied (0.125 Gy). A time-course experiment was performed to test whether radiation-induced cell cycle delay may explain saturation of the micronucleated reticulocyte endpoint at doses >1 Gy. For this experiment, groups of four female C57BL/6N mice were exposed to 1, 1.5, or 2 Gy TBI, and blood collection occurred at 12h intervals from 43 to 115 h post-exposure. Reduced reticulocyte frequencies were observed for each dose studied, and the recovery of reticulocytes was increasingly delayed with higher radiation doses. Maximal micronucleated reticulocyte frequencies were observed at 43 or 55 h, with progressively lower values at later time points. At no time did micronucleated reticulocyte frequencies induced by 1.5 or 2 Gy significantly exceed that observed for 1 Gy at 43 h. These time-course data suggest that radiation-induced cell cycle delay cannot account for the micronucleated reticulocyte downturn phenomenon observed at doses greater than 1 Gy. An alternate hypothesis is discussed whereby apoptotic elimination of severely damaged bone marrow erythroid precursors plays a dominant role in saturating the radiation-induced micronucleated reticulocyte response observed for C57BL/6N mice.     

The relationship of bone marrow type and microvasculature to the microdistribution and local dosimetry of plutonium in the adult skeleton

Most plutonium-induced bone tumors in beagles arise in trabecular bone sites surrounded by hematopoietic tissue. The microvasculature and the relative incorporation of 241Pu (a low energy beta emitter) on trabecular bone surfaces from red and fatty marrow sites were studied in the adult beagle. The vascular volume, as determined by India ink perfusion, was about 16% in the red marrow and about 2% in the fatty marrow. The red marrow has large vascular sinusoids with a discontinuous endothelial lining whereas fatty marrow has a closed capillary bed. Plutonium concentrations on bone surfaces of red marrow sites are about 0.43 pCi/cm2/nCi/kg of injected dosage, a factor of eight greater than at fatty marrow sites (0.053 pCi/cm2/nCi/kg). The differences in the bone marrow microvasculature between red and fatty marrow help to explain differences in plutonium incorporation and local bone physiology in these skeletal sites. These observations may relate to the nonuniform distribution of plutonium-induced osteosarcomas observed in adult, long-lived mammals.     

Effect of pre-exposure to beta rays of tritium on some biochemical parameters measured in organs of rats subsequently irradiated with fast neutrons

The experiment examined biological responses produced by combined sequential exposure to low-level tritium contamination, followed by challenging irradiation with fast neutrons. Modifications of endogenous antioxidant potential of different organs in rats were discussed in relation to tissue radiosensitivity. Rats pre-contaminated to 7 cGy and 35 cGy have been additionally irradiated to 1 Gy with fast neutrons. Lipid peroxide level was determined in liver, kidney, small intestine, spleen, bone marrow, and plasma. Reduced glutathione (GSH) level and glucose-6-phosphate dehydrogenase (G6PDH) activity were determined in erythrocytes. An in vitro thymidine uptake assay was performed in isolated bone marrow cells. The lipid peroxide level decreased significantly only in liver and kidney from rats pre-exposed to 35 cGy. For small intestine and spleen, tissues of comparatively higher radiosensitivity, no induced radioprotection was observed, as reflected in the homeostasis of the lipid peroxides. The same behavior was observed in bone marrow, the most radiosensitive tissue studied. However, the bone marrow thymidine-incorporation assay revealed a possible adaptive-type reaction in rats pre-exposed to 35 cGy. We conclude that for radiosensitive tissues pre-exposure to chronic low doses of low linear energy transfer (LET) irradiation has no protective effect on their antioxidant status, whereas a protective effect is observed in radioresistent tissues.     

Angiotensin II type 1 receptors and the intestinal microvascular dysfunction induced by ischemia and reperfusion

The acute phase of intestinal ischemia-reperfusion (I/R) injury is mediated by leukocytes and is characterized by oxidative stress and blood cell recruitment. Upregulation of angiotensin II type 1 receptors (AT1-R) has been implicated in the pathogenesis of conditions associated with oxidative stress. The AT1-R-antagonist Losartan (Los) attenuates leukocyte recruitment following I/R. However, the role of AT1-R in intestinal I/R injury and the associated platelet-leukocyte interactions remains unclear. The objective of this study was to define the contribution of AT1-R to I/R-induced blood cell recruitment in intestinal venules. Leukocyte and platelet adhesion were quantified by intravital microscopy in the small bowel of C57Bl/6 [wild-type (WT)] mice exposed to sham operation or 45 min of ischemia and 4 h of reperfusion. A separate WT group received Los for 7 days before gut I/R (WT-I/R + Los). AT1-R bone marrow chimeras that express AT1-R on the vessel wall but not blood cells also underwent I/R. Platelet and leukocyte adhesion as well as AT1-R expression in the gut microvasculature were significantly elevated after I/R. All of these responses were attenuated in the WT-I/R + Los group, compared with untreated I/R mice. A comparable abrogation of I/R-induced blood cell adhesion was noted in AT1-R bone marrow chimeras. I/R-induced platelet adhesion was unaltered in mice overexpressing Cu,Zn-SOD or mice deficient in NAD(P)H oxidase. These data suggest that although gut I/R upregulates endothelial expression of AT1-R, engagement of these angiotensin II receptors on blood cells is more important in eliciting the prothrombogenic and proinflammatory state observed in postischemic gut venules, through a superoxide-independent pathway.     

The effect of haemorrhage on the cell populations of the thymus and bone marrow in wild starlings (Sturnus vulgaris)

Summary Following the withdrawal of blood from the brachial vein of adult wild starlings (Sturnus vulgaris) changes in the cell populations within the bone marrow and thymus were observed over an eight day period. The packed cell volume, haemoglobin content and reticulocyte count of the peripheral blood was determined before and after haemorrhage.The maximum effect of the haemorrhage was observed in the bone marrow after four days when the population of small lymphocytes, and basophilic erythroid precursors were reduced to less than 1%. At the same time the percentage of another line of erythroid cells increased to 68%. This second erythroid lineage was the major erythroid line in the thymus, and again maximum representation occurred at 4 days post haemorrhage. After this the thymus became predominantly lymphoid and started to increase in size.The two erythroid lines are described and their status with regard to avian thrombocytes is also discussed.The peripheral blood had not attained the pre-haemorrhagic values for reticulocyte counts by eight days although the packed cell volumes and haemoglobin contents were similar.I would like to thank Dr. Peter Ward of the Institute of Terrestrial Ecology for help in obtaining the starlings. Thanks are also due to the staff of the Anatomy Department of St. Thomas's Hospital Medical School, and in particular Mr. Watson. This and other work on the thymus is possible due to the support of the Research (Endowments) Committee of St. Thomas's Hospital