Miniplate fixation for repair of mandibular and maxillary fractures in 15 dogs and 3 cats.

Maxillofacial miniplates and screws were used for skeletal fixation in 15 dogs and 3 cats that sustained a variety of mandibular and maxillary fractures. These implants were used as neutralization or buttress fixation in 11 caudal (junction of the ramus with the mandibular body) and 2 rostral mandibular fractures, 4 maxillary fractures, and 2 zygomatic arch fractures. All but one of the fractures healed with appropriate occlusion and excellent function. In one case of a rostral mandibular fracture, soft tissue dehiscence occurred accompanied by a loss of the fixation and subsequent distraction of the bone fragments; reasonable function was obtained by performing a rostral mandibulectomy. Plate contouring and application of the miniplates along the appropriate biomechanical lines of stress was easily performed and permitted the biomechanical principles of tension band fixation to be applied in most cases. Miniplate fixation, either used alone or in combination with other fracture fixation techniques, achieved sufficiently rigid skeletal fixation to provide uncomplicated healing and good to excellent functional and cosmetic results in 14 dogs and 3 cats.

Early postoperative ultrasonographic evaluation of incisional sites in dogs: 15 cases (1990-1992).

Ultrasonography of the surgical sites of 15 dogs was performed 3 to 8 days after they underwent major orthopedic surgical procedures. Eight dogs were suspected of having incision-site complications on the basis of localized signs of pain, heat, or swelling and clinical signs of pyrexia, lethargy, or anorexia. Seven dogs had apparently normal healing of the incision. Ultrasonography was used to assess and compare the character of fluid accumulation, to detect fluid accumulation associated with evidence of distal enhancement, and to evaluate gas accumulation and disruption of muscle fibers. Ultrasonography of the 8 dogs with complications of the incision site revealed fluid accumulation (8 dogs), distal enhancement associated with fluid accumulations (2), disruption of muscle fibers (1), and gas accumulation (1). Ultrasonography of the 7 dogs with apparently normal healing of the incisions revealed fluid accumulations (2 dogs), fluid between fascial planes (4), disruption of muscle fibers (1), and gas accumulation (1). Aspirates of fluid were obtained from 7 dogs with suspected incision-site infection. Analysis of results of cytologic evaluation or bacterial culturing confirmed infection in 6 dogs and indicated that 1 dog had a sterile hematoma. Ultrasonography is a sensitive technique for the detection and localization of fluid accumulations; however, the detection of fluid accumulations was not limited to dogs with incision-site complications. Fluid accumulations can be evaluated by use of ultrasound-guided needle aspiration, which has few associated negative side-effects. During the early postoperative period, results for fluid evaluation of samples obtained by use of accurately placed aspiration needles can be used to serve as a guide for further treatment.

Surgical stapling of large intestines.

Surgical stapling instruments can be used to perform end-to-end anastomoses in the colon and rectum. A new method of colonic anastomosis is described for cats with acquired forms of megacolon. Alternative approaches for performing colonic anastomoses are described in humans and in large dogs which can be used for colonic resections of focal nature as well as for subtotal colectomy. Advantages and disadvantages of surgical stapling instruments in the large intestine are reviewed.

Subtotal colectomy with surgical stapling instruments via a trans-cecal approach for treatment of acquired megacolon in cats.

Surgical stapling equipment was used to perform an end-to-end colonic anastomosis in 15 cats for the treatment of acquired megacolon. An end-to-end stapling device was passed to the anastomotic site by a trans-cecal approach. Subsequent closure of the cecal incision was accomplished with a thoracoabdominal stapling device. Two cats had hemorrhagic episodes immediately after surgery that required blood transfusions. All 15 cats have had good to excellent health after subtotal colectomy and colocolostomy performed using this stapling technique. Results of this study have demonstrated that "single surgical field" placement of the end-to-end stapling device has the primary advantage of simplicity and a lower chance of contamination compared with (dual field) rectal passage of similar devices. Closure of the cecal access incision is easily performed without reducing the diameter of the large intestinal lumen. The stapling technique provided an efficient and consistent method for anastomosis of the large bowel in cats.

Hypercalcemia associated with rodenticide poisoning in three cats.

Hypercalcemia (12.0 to 18.3 mg/dl) was detected in 3 cats that had eaten a rodenticide that contained cholecalciferol. Clinical signs included lethargy, anorexia, vomiting, and polydipsia. Treatment with furosemide and fluids administered IV resulted in normalization of the serum calcium concentration and in remission of the clinical signs in 2 cats. One cat with a serum calcium concentration of 18.3 mg/dl did not have clinical signs, was not treated, and was reportedly normal 9 months after initial examination. We attributed the uniformly favorable outcome of exposure to the rodenticide in these cats to the small quantity of the toxin ingested.

Defective erythroid progenitor differentiation system in congenital hypoplastic (Diamond-Blackfan) anemia.

To explore the etiology of congenital hypoplastic or Diamond-Blackfan anemia (DBA) we investigated in vitro erythropoiesis in nine patients. Of the nine, seven were clinically responsive to prednisone. Four were infants evaluated at the time of diagnosis. Six were never or were only minimally transfused. Those for whom prednisone had been prescribed had discontinued the drug a minimum of five months prior to study. The bone marrows of these nine patients were compared with those of hematologically normal individuals and with those of four patients with transient erythroblastopenia of childhood (TEC) whose erythroid aplasia was as severe as that of the patients with DBA. Using the plasma clot semisolid culture technique to enumerate erythroid progenitors and to evaluate the growth characteristics of the colonies to which they give rise, we concluded that at the onset of DBA: (a) erythroid progenitor frequency does not correlate with the degree of anemia and erythroblastopenia; (b) erythroid progenitor differentiation may in some cases be abnormally insensitive to crude preparations of erythropoietin; and (c) progenitor erythropoietin insensitivity in vitro does not necessarily indicate prednisone insensitivity in vivo. Thus, DBA does not appear to be solely the result of deficient formation of erythroid progenitors but is, in addition, a disorder that is due to defective progenitor differentiation in vivo.

Lethal graft-versus-host disease: modification with allogeneic cultured donor cells.

The use of the bone marrow culture technique was studied as a means to prepare donor marrow for bone marrow transplantation to avoid lethal graft-versus-host disease (GVHD). Preliminary experiments demonstrated the rapid loss of theta-positive cells in such cultures, so that theta-positive cells were not detected after 6 days. Initial experiments in C3H/HeJ (H-2k, Hbbd) recipients prepared with 900 rad demonstrated improved survival when 3-day cultured C57BL/6 (H-2b, Hbbs) donor cells were used in place of hind limb marrow for transplantation. However, hemoglobin typing of recipient animals revealed only short-term donor engraftment, with competitive repopulation of recipient marrow occurring. Subsequent experiments were done in 1,200-rad prepared recipients, with long-term donor engraftment demonstrated. The majority of 1,200-rad prepared animals receiving cultured allogeneic cells died of GVHD, but animals receiving 28-day cultured cells had an improved 90-day survival and a delay in GVHD development over animals receiving hind limb marrow or marrow from shorter times in culture. In addition, animals receiving anti-theta-treated, 3-day nonadherent cells had an improved survival (44%) over animals receiving anti-theta-treated hind limb marrow (20%). These experiments demonstrate modest benefit for the use of cultured cells in bone marrow transplantation across major H-2 histocompatibility complex differences.

Evidence for genetic restriction in the suppression of erythropoiesis by a unique subset of T lymphocytes in man.

The suppression of erythropoiesis by lymphocytes from patients with a T cell lymphoproliferative syndrome and pure erythrocyte aplasia has been previously demonstrated. To study the nature of the suppressor cell and possible genetic restriction of this suppression, we investigated a patient with severe anemia, splenomegaly, lymphocytosis, and erythroid aplasia. A 3-mo course of low-dose daily oral cyclophosphamide achieved a complete remission for over 12 mo. The surface phenotype of his lymphocytes was analyzed by means of antibodies to lineage, differentiation, and activation-specific surface antigens. The cells expressed mature T cell antigens T3, T8, and T11, while lacking T1. Immature T cell, B cell, and the monocyte-specific antigen Mo2 were absent, while Mo1, a monocyte-associated antigen not normally expressed on T cells, was present. T10 and Ia expressed as activation antigens were also present. The cells, cryopreserved at diagnosis, were thawed and co-cultured in plasma clot with patient remission marrow samples at T cell/bone marrow ratios of 1:1 and 2:1. There was nearly 90% suppression of erythroid colony-forming unit expression and 60% suppression of erythroid burst-forming unit expression at 2:1 T cell to bone marrow ratios and somewhat less suppression at 1:1. Granulocyte/macrophage progenitor expression was unaffected. Erythroid progenitor differentiation in the marrows of two HLA identical siblings was similarly suppressed. The cells were co-cultured with the marrows of nine nonrelated donors to investigate the potential genetic restriction of this suppression. Colony suppression equal to that observed in the marrow of the patient and his siblings was found in studies of two partially HLA identical individuals. No suppression was detected in marrow co-cultures of two entirely HLA dissimilar individuals. These results show that suppression of erythropoiesis by a unique subset of T8, Mo1, Ia-positive lymphocytes isolated from a patient with lymphocytosis and erythrocyte aplasia is genetically restricted.

Synthesis of hemoglobin F in adult simian erythroid progenitor-derived colonies.

The simian hematopoietic system is known to respond to anemic stress with the production of erythrocytes containing large amounts of fetal hemoglobin. To determine the regulatory mechanism responsible for hemoglobin F (HbF) production in stress erythropoiesis, adult simian bone marrow cells were cultured in plasma clots in the presence or absence of erythropoietin and burst-promoting activities, and the HbF content of progenitor-derived colonies was determined by radioimmunoligand assay. Three classes of erythroid progenitors were detected: BFU-E, CFU-E, and a very mature cohort of dense highly erythropoietin-responsive cells (HERC). These classes varied in inverse proportion to their maturity with respect to their potential for HbF accumulation in the colonies to which they give rise. Both erythropoietin and burst-promoting activity stimulated HbF production, particularly in colonies derived from immature progenitors. For example, under conditions of high erythropoietin stimulation, BFU-E colonies contained 13.7-37.7% HbF, CFU-E colonies contained 2.8-13.5% HbF, and HERC colonies 0-1% HbF. These results suggest that under nonstress conditions simian erythrocytes are derived almost entirely from HERC progenitors and proerythroblasts in which gamma chain synthesis is suppressed. During stress erythropoiesis, augmented HbF accumulation could be explained by the rapid entrance into the marrow of proerythroblasts directly derived from immature progenitors. Gamma chain production in these proerythroblasts is additionally regulated by the changes in environmental erythropoietin and burst-promoting activities.

Effect of acyclovir and interferon on human hematopoietic progenitor cells.

Continuous in vitro exposure of human bone marrow cells to acyclovir (approximately 200 microM) or human leukocyte interferon (approximately 250 U/ml) caused 50% inhibition of granulocyte colony-forming cell differentiation. Colonies expressed in the presence of either agent were reduced both in size and number. Erythroid progenitors were more resistant than granulocyte progenitors to the antiproliferative effects of acyclovir. Progenitor cells of patients recovering from cytotoxic chemotherapy were no more sensitive to the effects of acyclovir or interferon than were cells obtained from patients before chemotherapy.

Response of three classes of human erythroid progenitors to the absence of erythropoietin in vitro as a measure of progenitor maturity.

The effect of erythropoietin (Ep) deprivation (epoprival state) on plasma clot cultures of human bone marrow and peripheral blood erythroid progenitors was examined. In normal individuals, there was a marked reduction of CFUE derived colony expression if Ep was withheld from the culture for even one day. Peripheral blood BFUE retained substantial function during the epoprival state for up to 2 to 5 days while bone marrow-derived BFUE had intermediate sensitivity. Thus the capacity of erythroid progenitors to withstand incubation in semi-solid media in the absence of Ep is a characteristic of immature, rather than mature, erythroid progenitors.

Absence of common ALL antigen on normal bipotent myeloid, erythroid, and granulocyte progenitors.

The presence of the common acute lymphoblastic leukemia antigen (CALLA) on leukemic cells from the great majority of patients with non-T cell acute lymphoblastic leukemia and chronic myelogenous leukemia in blast crisis suggests that CALLA could be differentiation antigen expressed by normal lymphoid and myeloid stem cells. Treatment with a murine monoclonal anti-CALLA antibody and complement lysed CALLA-positive leukemic cells quantitatively, whereas similar treatment of nucleated cells from peripheral blood and bone marrow failed to affect the expression, in semisolid culture, of CFU-G/E, BFU-E, CFU-E, or CFU-C. These data suggest that CALLA is not a normal differentiation antigen of the myeloid bipotent cell or its committed progenitors.

Control of the simian fetal hemoglobin switch at the progenitor cell level.

This investigation was designed to define the cellular level at which the gamma to beta globin switch is established in the developing simian fetus in order to determine whether the switch is controlled by environmental influences within differentiating erythroid precursors or predetermined by the genetic program of erythroid progenitors. Samples of marrow and liver were obtained from rhesus fetuses throughout the switch period, and marrow was obtained from adult rhesus monkeys. Globin chain synthesis was then measured in differentiated erythroblasts and in erythroid progenitor-derived colonies grown in semisolid media. The relative rates of synthesis of gamma and beta chains were determined by the uptake of [(3)H]leucine into the respective chains separated by Triton gel electrophoresis and in some cases by urea carboxymethyl cellulose chromatography. Four periods of the switch were defined during fetal development. In the preswitch period both erythroblasts and progenitor-derived colonies produced <5% beta globin. In the early switch erythroblasts produced 5-15% beta globin, while progenitor-derived colonies produced 10-35% beta globin. In mid-switch erythroblasts synthesized 50% beta globin, whereas progenitor-derived colonies produced only 15-35% beta. At the completion of the switch erythroblasts produced 100% beta globin, while progenitor-derived colonies produced as little as 40% beta chains. We conclude that the program of globin synthesis that characterizes the fetal switch is established at the level of erythroid progenitors. Fetal erythroid burst-forming units (BFU-E) dominate the marrow prior to the switch. The early switch period is heralded by the appearances of adult erythroid burst-forming units programmed to express increasing beta chain synthesis in colonies. By mid-switch a second class of adult erythroid progenitors capable of giving rise to fetal and adult hemoglobin synthesis in in vitro colonies becomes apparent. These shifting populations of erythroid progenitors with unique globin synthesis programs give rise to the erythroblasts that create the sigmoid pattern of the fetal to adult hemoglobin switch in the developing simian fetus.

Mature bone marrow erythroid burst-forming units do not require T cells for induction of erythropoietin-dependent differentiation.

Cell-cell interactions between mature T cells and peripheral blood null cells induce erythropoietin-stimulated differentiation of peripheral blood-derived erythroid progenitors. By the use of complement-fixing cytolytic murine hybridoma and antibody uniquely reactive with mature T lymphocytes, this dependence of immature peripheral blood erythroid burst-forming unit (BFU-E) differentiation upon mature T cells or a T cell conditioned medium is confirmed. By using the same antibody, it is demonstrated that the differentiation of mature bone marrow BFU-E does not require either mature T cells or lymphocyte mitogenic factor. These findings do not preclude the presence in the bone marrow of other cells, perhaps even immature T cells, that influence erythropoietin-dependent erythroid differentiation of mature marrow BFU-E.