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In this study cell proliferation in Peyer’s Patches (PP) and the crypts of Lieberkuhn of the follicle-associated ileal epithelium was analyzed during the development of acute lethal graft-versus-host disease (GVHD) in adult rats. In addition, the effect of thymectomy on GVHD-induced lymphoproliferation was determined by analyzing the3H-thymidine labeling index in neonatally thymectomized-control and thymectomized-GVHD rats. A significant increase in the3H-thymidine-labeling index was found in interfollicular (days 2–7), dome (days 5–10), and follicular (days 5–12) regions of PP as well as in associated ileal crypts (days 5–12) of GVHD rats as compared with controls. Thymectomy altered the proliferative response in PP of GVHD rats in that incorporation of3H-thymidine by follicular and interfollicular cells was significantly lower than in sham-thymectomized GVHD controls during the later stages of the disease. The results suggest a possible role for host thymus-dependent cells in stimulation of or participation in cell proliferation within follicular and interfollicular areas of PP.

Lizards, especially iguanids and varanids, frequently develop nutritional osteodystrophy in captivity, but its pathogenesis is incompletely understood. Green iguanas fed an experimental diet low in calcium (0.2%) and adequate in phosphorus (1.1%) developed severe osteoporosis characterized by flattened inactive osteoblasts, marked resorption of endosteal bone by large multinucleated osteoclasts, and pronounced resorption of cortical bone by osteocytic osteolysis. Iguanas fed an experimental diet low in both calcium (0.1%) and phosphorus (0.2%) developed osteoporosis with osteomalacia characterized by large active osteoblasts overlying wide osteoid seams, marked osteoclastic resorption of endosteal bone, and large osteocytic lacunae which had a prominent layer of osteoid. Osteocytes in iguanas fed the low calcium diets were small in relation to the size of their lacuanae and contained abundant microtubules, microfilaments and mitochondria but a paucity of rough endoplasmic reticulum. Mean ash content of tibias from iguanas fed the low calcium diets was lower, particularly in iguanas that developed severe osteomalacia, than in iguanas fed the control diet (2.7% calcium, 1.1% phosphorus). The ultrastructural evidence suggesting active bone formation, osteoclastic resorption, and osteocytic osteolysis seen in control iguanas was consistent with that of a young growing animal. The results of this investigation demonstrated that experimental iguanas fed diets low in calcium developed hypocalcemia and compensatory hyperparathyroidism resulting in progressive osteoporosis due to osteoclastic and osteocytic osteolysis.

The mitogenic effect of serum in defined cells in organ-cultured normal intact membranous rat mesentery was studied. Serum caused a strictly concentration-dependent stimulation of proliferation in mesothelial-cell-like and fibroblast-like cells, whereas the sequence S-G2-mitosis was apparently unaffected by serum. The results support the concept that similar mitogenic mechanisms may operate in cell culture and in situ in an intact tissue.

It has been shown previously that dendritic reticulum cells (DRC) in human secondary lymphoid follicles possess an immunoreactive acid cysteine-proteinase inhibitor (ACPI). In the present study, lymph nodes from 12 patients with AIDS-related persistent generalized lymphadenopathy (PGL) were investigated in order to detect whether or not any alterations occur in ACPI-immunoreactive DRC in this disorder. In the majority of PGL cases, profound alterations were found, the main characteristics of which were erosion, partial or total disruption of lymphoid follicles. However, similar though much less marked alterations were also found in some control cases. It is concluded that this type of follicular damage is a common and characteristic feature in PGL. It is not specific to PGL, however, but represents rather a special type of reaction in lymphatic tissue. The advantage of ACPI immunohistology for demonstrating the DRC pattern is that it can be performed on routinely fixed and paraffin-embedded tissues.

Bei männlichen Sprague-Dawley Ratten wurde in drei verschiedenen Altersstufen (juvenile 2–4 Wochen alte, eben ausgewachsene 2–4 Monate alte und senile 2–2,5 Jahre alte Tiere) autoradiographisch der Proliferationsumfang der Nebennierenrinde (Zona glomerulosa, Zona fasciculata, Zona reticularis) untersucht. Dabei wurde den Tieren kontinuierlich 0,5–20 Tage lang3H-Thymidin über die Schwanzvene infundiert. Nach 13tägiger Dauerinfusion findet sich bei juvenilen Ratten der höchste Markierungsindex in der Zona glomerulosa (etwa 90%); der Index in der Fasciculata ist weniger hoch (etwa 70%) und in der Reticularis am niedrigsten (etwa 10%). Für die eben ausgewachsenen Ratten wurden nach 20tägiger Infusion von3H-Thymidin folgende Werte ermittelt: Zona glomerulosa ca. 45%, Zona fasciculata 14%, Zona reticularis ca. 9%; für die senilen Ratten (20tägige Dauerinfusion): Zona glomerulosa 12%, Zona fasciculata 24%, Zona reticularis etwa 11%. Die Ergebniskurven zeigen im Bereich der kurzen Infusionszeiten in allen drei Altersstufen Schwankungen, die möglicherweise Ausdruck der infusionsbedingten Stress-Situation sind. Bei länger-dauernder Infusion vermindern sich diese Schwankungen als Zeichen der Adaptation der Tiere an die Versuchsbedingungen.

A series of 217 trephine bone marrow biopsies from adult patients and specimens from 16 fetuses and 5 infants were examined for the presence of stromal myoid cells (MCs) using a monoclonal antibody recognizing α-smooth muscle actin. In the normal adult bone marrow, stromal cells did not contain α-smooth muscle actin, whereas during fetal life, many α-smooth muscle actin-containing MCs were connected with vascular sinusoids in the primitive bone marrow. This cell type reappeared in various characteristic distribution patterns in adult bone marrow during different neoplastic and non-neoplastic conditions including metastatic carcinoma, Hodgkin’s disease, multiple myeloma, hairy cell leukemia, acute myeloid leukemia (FAB M4, 5, 7) and chronic myeloproliferative diseases. In general, the appearance of MCs was associated with a slight to pronounced increase in the deposition of reticulin and collagen fibers. We propose that bone marrow MCs represent a distinct subpopulation of fiber-associated or adventitial reticular cells undergoing cytoskeletal remodeling in response to various stimuli.

In mice poisoned by α-amanitin nuclear changes typical of this toxin were observed in β-cells of pancreatic islets. The lesions became progressively more severe and at 48 h after toxin injection some cells were necrotic. The damage to these cells could have implications in the changes in glycogen metabolism which occur after α-aminitin poisoning.

The ultrastructural changes of human leukemic cell nuclei have been investigated. Particular attention is paid to the alteration of the nuclear envelope and its constituents, i.e., the pores and the Zonula Nucleum Limitans which appear constantly involved in these pathologic processes. An alteration of the relationships between the components of the nuclear envelope and the chromatin itself may be responsible for the appearance of the most nuclear changes.

Flocculent densities in the matrix of mitochondria have become quite important in cell pathology since, when prominent, they indicate irreversible cell injury. The morphology and chemical nature of these flocculent densities have been studied in kidney after various periods of autolysis in vitro in whole tissue samples and in isolated mitochondria. After 30 to 60 min of ischemia, flocculent densities were seen only occasionally and they were most prominent in samples subjected to mechanical damage during isolation. However, in 2- and 4-h samples numerous densities were seen. The size of the densities increased with time, being about 1,400 Å in diameter at 4 h. Densities were also seen in mitochondria isolated in medium containing EDTA. They were seen only in the mitochondrial matrix, and could occasionally be found in condensed mitochondria. Small densities were generally round but larger ones varied in shape and often appeared as aggregates of smaller densities. Digestion of the densities from water-soluble glycol methacrylate embedded samples was successful with pronase, but neither acid nor lipid solvents were effective. Calcium or inorganic phosphate content of isolated mitochondria did not show an increase parallel to the occurrence of flocculent densities. The results suggest that the densities consist predominantly of protein and are probably formed through denaturation of proteins of the mitochondrial matrix and/or of the inner membrane.