Distribution of actin in migrating leukocytes in vivo

Summary Blood cells proliferate extravascularly in the bone marrow and enter the circulation by migrating through endothelial cells of venous blood sinuses. This migration, or diapedesis, was suspected to involve actin. To test for the presence and distribution of actin, sections of rat bone marrow were examined by indirect immunocytochemistry. Affinity purified rabbit antichicken gizzard actin antibody, and goat-antirabbit IgG-FITC, or goat antirabbit IgG colloidal gold probes were used. The migrating cell contacts the endothelial cell and forms a podosome (a cortical bleb). Immunocytochemistry shows this region to contain actin. As diapedesis proceeds the podosome deforms, then breaches the endothelial cell. At this time the anterior portion of the leukocyte shows heavy labeling for actin. When the migratory cell traverses approximately half of its length through the endothelial cell, actin appears prominent in the caudal region of the cell. The immunocytochemical data suggest that actin is nonrandomly distributed in leukocytes undergoing diapedesis and may be a component of the force-generating mechanism responsible for this transcellular migratory event.Supported in part by grants from the American Cancer Society, Illinois Division, Inc. (83-4), and NIH (GM 28397)     

Studies on bone marrow histogenesis: Morphometric and autoradiographic studies of regenerating marrow stroma in extramedullary autoimplants and after evacuation of marrow cavity

Summary The marrow cavity of the rat tibia was mechanically evacuated and autoimplanted to the subcutaneous tissue. The regenerative process which restored the integrity of marrow stroma and hemopoiesis, was morphometrically evaluated in whole mount of tibia. Following evacuation, the clot filled the cavity. The granulation tissue then appeared and expanded, penetrating and replacing the clot. The fibroblasts of the granulation tissue differentiated into osteoblasts forming osteoid bone. Within its interstices, the primordial marrow consisting of loose connective tissue and vascular sinuses appeared and hemopoiesis resumed. Expansion of hemopoiesis resulted in the resorption of bone and within three weeks the tibial cavity was restored to the pre-evacuation state.Autoradiography indicated that the labeling index was initially high in fibroblasts and osteoblasts but was subsequently reduced while it increased in osteocytes, cells of Haversian canals, stromal and hemopoietic cells of marrow. The finding is in disagreement with the view that the regenerative process originates from the Haversian canal. When the label was introduced on day 4 post-operatively, it subsequently appeared in osteocytes, cells of Haversian canal, stromal elements of the marrow, but not in the hemopoietic cells. This indicates complete dissociation of marrow stroma and hemopoietic stem cell.Supported by NASA Contract NSG 9061. Mehdi Tavassoli is the recipient of a CRD Award AM-70551     

A comparison of two methods for the microscopic determination of age at death.

The precision and accuracy of the Kerley and Ahlqvist-Damsten microscopic methods of age determination are compared. Both methods were applied to the same sample of 40 femoral thin sections of documented age at death. The results indicate that (1) both methods can be used with equal precision, as suggested by comparable observer errors; and (2) the Kerley method produces overall more accurate age estimates. The low previously published standard error of the Ahlqvist-Damsten method (6.71 years) apparently results from the uneven age distribution and small size (20) of their sample.     

Bone Marrow Depletion as a Coincidental Finding to Hypothermia in Macaca mulatta

Three of 16 juvenile rhesus monkeys (Macaca mulatta) and 1 rhesus of 79 adult rhesus and cynomolgus monkeys (Macaca fascicularis) were found comatose in a state of profound hypothermia after a heating failure occurred in the room in which they were housed. One juvenile monkey died shortly thereafter. The three other monkeys were revived with gradual warming and supportive therapy but later experienced separate acute clinical crises manifesting shock and died at 19, 31, and 51 days after the initial episode. Histopathologic findings of severe bone marrow depletion were observed in each of the three monkeys that died after the initial episode.     

Effects of dynamic impacts on human bones

Flat bones of human skeleton were subjected to dynamic indentation with ball indenters. The impacted surface was studied under high magnification and also by using the technique of multiple beam interferometry. The impulse caused the pile up of material at a little distance from the edge of the indent. The diameter of indent is found to increase as fourth root of the energy of impact. Bone structure also has the tendency to minimize the damage caused by external forces. There was about 90% recovery in deformation in the depth of indents due to internal stresses created inside the bone by the impact.     

Osteometry and autoradiography of the long bones of sleletons of women exposed to internal radiation at 13–19 years of age

Lengths of long bones of skeletons were examined in 25 women first exposed to large skeletal doses of radiation (alpha particles from radium) at the age of 13–19 years. Meanlengths did not differ significantly between two subgroups based on age at first exposure toradiation (i.e., 13–16 vs. 17–19 years). Autoradiographs of femora of some women who ingested radium at 13–15 years of age showed evidence for bone growth when blood levels of radium were low (i.e., after ingestion of radium). These findings indicate no detectable effect of large skeletal doses of radiation on growth in adolescent and post-adolescent periods.     

A left/right comparison of sequential bone loss from the metacarpals of postmenopausal women

The rate of decrease of mean metacarpal cortical width was assessed by sequential radiographic morphometry for each hand separately in a series of 46 right-handed postmenopausal women observed for 222 patient-years. For the left hand, the mean rate was 0.0331 ± 0.0053 mm/year and for the right, 0.0310 ± 0.0060 mm/year. The difference between the hands in the rate of decrease was not significant. It is concluded that the higher work load of the dominant hand has no effect on the rate of bone loss from the metacarpals of postmenopausal women.