Deleterious effects of irradiation and bone marrow transplantation therapy in the genetically anemic an/an mouse

The efficacy and outcome of bone marrow transplantation therapy following lethal irradiation were examined in syngeneic mice that had a hereditary macrocytic anemia (an/an) or were genotypically normal (+/+). Successful RBC and WBC replacement, based on blood cell parameters and donor genetic markers, were observed in all combinations of transplant therapy. Nevertheless, the an/an mice died prematurely several months after treatment, whether they received +/+ or an/an marrow cells. In contrast, the +/+ recipients of either +/+ or an/an marrow cells survived for at least 1 year after transplantation. Premature death of the an/an mice was associated with lymphopenia, anemia, kidney lesions, and severe pathogen-free pneumonitis. On the basis of our results, we hypothesize that the premature deaths of an/an mice are caused by a kind of chronic irradiation damage to which an/an mice are especially susceptible.     

Regeneration of the thymus in old male rats treated with a stable analogue of LHRH

It has been shown that the thymus can be regenerated in intact old rats by implanting s.c. a stable analogue of LHRH. Old male rats were given s.c. implants of osmotic pumps containing a solution in citrate buffer of the analogue which was given at a rate of 1 microgram/h for 28 days. Some animals were given pumps containing buffer alone, and another group of rats was orchidectomized. The animals were killed after 28 days and the tissues weighed and taken for histology. Serum testosterone was measured by radioimmunoassay. Sham-treated rats had small fatty thymuses, which were poorly organized with a very narrow band of cortex. Animals treated with the analogue of LHRH and those which had been orchidectomized had relatively large thymuses which were multi-lobed in drug-treated rats, and atrophied accessory sex organs. The testes were grossly atrophied in analogue-treated rats. Histologically, the thymus looked healthy, having a wide, thymocyte-filled cortex and a clearly defined corticomedullary junction. Serum testosterone concentrations were similar in orchidectomized and analogue-treated rats. It is concluded that it is possible to regenerate the thymus in old rats treated with an analogue of LHRH, but the effect is accompanied by chemical castration. It is also clear that the old pituitary gland is susceptible to the desensitizing action of an LHRH analogue.     

Immunologic correlates of spontaneous lymphocyte proliferation in human T-lymphotropic virus infection.

Previously we showed that mononuclear cells from about half of human T-lymphotropic virus (HTLV)-seropositive persons exhibit spontaneous proliferation in vitro. We sought to determine if proliferation was associated with other immunologic changes characteristic of HTLV infection. The parameters assessed were (1) percentages of lymphocytes expressing CD4 and/or CD25 (interleukin-2 receptor), (2) serum levels of soluble CD25, (3) serostatus for other viruses, (4) anti-HTLV antibody levels, and (5) HTLV type determined by polymerase chain reaction or serologic reactivity with type-specific peptides. The proliferation+ HTLV (PROL+) group, proliferation HTLV (PROL-) group, and control group showed similar percentages of CD4+, CD25+, and CD4+CD25+ lymphocytes; serum levels of soluble CD25 were also similar. Antibodies to cytomegalovirus, hepatitis B core, and hepatitis C were present in similar proportions of PROL+ and PROL+ groups. However, a significant association was found between spontaneous proliferation and anti-HTLV antibody levels; sera from 67% of PROL+ persons, but only 18% of PROL- persons, required dilution to yield absorbance values within the linear range of the anti-HTLV antibody assay. In the PROL+ group, persons whose sera required the most dilution had proliferative responses significantly higher than those whose sera required no dilution. The PROL+ and PROL groups were similar with regard to the relative distribution of HTLV-I and HTLV-II infection. These findings indicate that HTLV-related spontaneous lymphocyte proliferation is related to levels of circulating anti-HTLV antibodies, and characterizes both HTLV-I and HTLV-II infection.     

Acceleration patterns of the head and pelvis when walking are associated with risk of falling in community-dwelling older people

BACKGROUND: A large proportion of falls in older people occur when walking, however the mechanisms underlying impaired balance during gait are poorly understood. This study evaluated acceleration patterns of the head and pelvis when walking on a level and an unpredictably irregular surface to determine whether older people at risk of falling demonstrate an impaired ability to stabilize the body under challenging conditions. METHODS: One hundred community-dwelling older people aged between 75 and 93 years were evaluated for their risk of falling using a range of physiological tests previously found to be accurate predictors of falling in prospective studies. Temporo-spatial gait parameters and acceleration patterns at the head and pelvis were then measured in three orthogonal planes while subjects walked on a flat corridor and an unpredictably irregular walkway. Harmonic ratios of head and pelvis accelerations in each plane were calculated to provide an indicator of stability. RESULTS: Subjects with a high risk of falling exhibited reduced temporo-spatial gait parameters and increased step timing variability. Harmonic ratios of acceleration patterns were reduced at the head and pelvis in the vertical and antero-posterior directions. These differences were particularly evident when walking on the irregular surface. CONCLUSION: Older people at risk of falling adopt a more conservative basic walking pattern, but this does not ensure that the movements of the head and pelvis are stable. The irregular pelvis and head accelerations evident in the high risk group suggests that these subjects may have difficulty controlling trunk motion and maintaining a stable visual field when walking, particularly on irregular terrain.     

Expression of specific granule markers on the cell surface of neutrophil cytoplasts

The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation.     

Myelostimulatory activity of recombinant human interleukin-2 in mice

In a series of studies designed to extend our understanding of interleukin-2 (IL-2) and to study the effect of biologic response modifiers on bone marrow, we observed that administering recombinant human (rH) IL-2 to normal mice resulted in an increase in the frequency of colony-forming units-culture (CFU-C) in bone marrow. In addition, rH IL-2 was able to accelerate host recovery from cyclophosphamide (CTX)- or radiation-induced bone marrow depression and peripheral blood leukopenia. Not only can rH IL-2 accelerate, in a dose-dependent manner, the return of bone marrow, peripheral blood cellularity, and CFU-C frequency to normal levels following cytoreduction by CTX or irradiation, but it also significantly increases CFU-C frequency to greater than normal levels. Furthermore, rH IL-2 can significantly prolong survival of animals receiving a lethal dose of irradiation or CTX. Thus, multiple mechanisms are responsible for the synergistic therapeutic activity associated with rH IL-2 and CTX. rH IL-2 does not act only as an immunomodulatory agent in the presence or absence of suppressor T cells, but also accelerates host recovery from cytoreductive agents, resulting in decreased leukopenia and perhaps resistances to secondary infection. Thus, rH IL-2 plus chemotherapy may increase therapeutic activity against neoplastic disease, not only by adding immune stimulation to the direct antitumor effect of the drug but also by allowing delivery of higher, more effective doses of chemotherapy.     

Subpectoral implantation of a cardioverter defibrillator under local anaesthesia

Objective—To evaluate patient acceptability of submuscular implantation of a cardioverter defibrillator (ICD) under local anaesthesia with conscious sedation.
Design—Retrospective review. Patient acceptability in the second half of the study was routinely assessed within 24 hours.
Setting—Regional cardiac centre.
Patients—45 consecutive patients with either aborted sudden death or haemodynamically unstable ventricular tachycardia were referred for ICD im- plantation.
Interventions—A subpectoral implantation technique was employed. Twelve procedures were performed under general anaesthesia. Thirty three patients were sedated with midazolam and diamorphine, and local anaesthesia was achieved with bupivicaine. Ventricular fibrillation for defibrillation threshold testing was induced by alternating current, T wave shock, or ultrarapid burst pacing. Patients were contacted after the procedure to assess acceptability.
Results—32 patients having implantation under local anaesthesia did not recall the surgical procedure. One patient described an awareness of "pushing" as the generator was positioned in the pocket. Seven patients said that the procedure was painless but recalled a test shock, four describing it as mildly uncomfortable. All 33 patients stated that they would be willing to have a second implant under local anaesthesia. Twelve patients who had the implant performed under general anaesthesia had no recollection of the procedure. Mean (SD) total procedure duration was significantly longer in those who had general anaesthesia (93 (16) v 67 (17) minutes; p = 0.0009).
Conclusions—Subpectoral implantation of ICDs may be performed safely with patient acceptability under local anaesthesia with conscious sedation.

Keywords: cardioverter defibrillator;  subpectoral implantation;  local anaesthesia;  pacing     

Modulation of megakaryocytopoiesis by thrombopoietin: the c-Mpl ligand

We have further characterized the biological activities, mechanism of action, and target cell populations of recombinant human and murine thrombopoietin (rhTPO and rmTPO) in in vitro human and murine model systems. Alone, hTPO or mTPO stimulated the maturation of immature murine megakaryoblasts as measured in a single cell assay. The combination of hTPO or mTPO and interleukin-6 (IL-6) resulted in a further increase in megakaryocyte differentiation in this system. Murine TPO stimulated mouse megakaryocyte progenitor development. Human megakaryocyte progenitor development was potentiated by hTPO alone and further augmented in the presence of the early-acting cytokines (IL-3) or kit ligand/stem cell factor (KL/SCF). To further define the mechanism of action of TPO, neutralization studies were performed with antisera to IL-3, granulocyte-macrophage colony-stimulating factor (GM- CSF), IL-1 beta, and IL-11. No diminution in TPO activity was observed in the presence of these antisera. Moreover, because adhesive interactions are known to modulate hematopoiesis, we studied whether hTPO might alter such interactions between human bone marrow (BM) megakaryocytes and human BM stromal fibroblasts. No changes were observed in either megakaryocyte expression of the surface molecules lymphocyte function-associated antigen-1, very late activation antigen- 4, or intercellular adhesion molecule-1 or the adhesion of megakaryocytes to stromal fibroblasts after treatment with the growth factor. Furthermore, no induction of secretion of the cytokines IL-1 alpha, IL-1 beta, GM-CSF, IL-6, granulocyte-CSF, tumor necrosis factor- alpha, transforming growth factor-beta 1, or transforming growth factor- beta 2 by primary human BM megakaryocytes was noted after treatment of the cells with hTPO. To address whether TPO affects very primitive hematopoietic progenitors, we studied the residual cells from the BMs of mice treated with high doses of 5-fluorouracil. Although no effect of mTPO alone was noted on the viability or replication of such primitive murine progenitor populations, the triple combination of IL-3 + KL/SCF + TPO stimulated growth of megakaryocyte progenitors. These results indicate that TPO is a highly lineage-specific growth factor whose primary biological effects are likely to be direct modulation of the growth and maturation of committed megakaryocyte precursors and immature megakaryoblasts.