In the absence of other Fc receptors, Fc gamma RIIIA transmits a phagocytic signal that requires the cytoplasmic domain of its gamma subunit.

The transmembrane isoform of Fc gamma RIII, Fc gamma RIIIA, is found on NK cells, cultured monocytes, and tissue macrophages in association with a dimer of an accessory subunit, either gamma or zeta. Functions of individual Fc receptors have been difficult to analyze due to coexpression of the receptors on hematopoietic cells and permanent cell lines expressing Fc receptors. cDNAs for the alpha and gamma subunits of Fc gamma RIIIA were cotransfected into COS-1 cells, which lack endogenous Fc receptors, to evaluate receptor-mediated phagocytosis and changes in [Ca2+]i. Transfectants both bound and phagocytosed IgG-sensitized erythrocytes and, following activation of Fc gamma RIIIA, increased [Ca2+]i. The gamma subunit was essential both for the surface expression of the receptor and for transduction of the phagocytic signal. Truncation of the gamma subunit cytoplasmic domain (amino acids 65-80) eliminated phagocytic function. Phorbol ester inhibited phagocytosis in a concentration-dependent manner, but did not affect IgG-sensitized erythrocytes binding, suggesting that a protein kinase C-dependent pathway inhibits phagocytosis. The data indicate that a tyrosine containing cytoplasmic domain within the gamma subunit is required for phagocytosis by Fc gamma RIIIA.

Concurrent phase I trials of intravenous interleukin 6 in solid tumor patients: reversible dose-limiting neurological toxicity.

Interleukin 6 (IL-6) has antitumor activity comparable to IL-2 in murine models with less toxicity. Because the biological effects of intermittent and continuous infusions may differ, we conducted two concurrent Phase I trials of daily x5, 1-h, and continuous 120-h i.v. infusions to determine the toxicity, biological effects, and maximum tolerated dose of i.v. IL-6. Cohorts of six patients with advanced cancer received escalating doses (1, 3, 10, 30, 100, and 150 microgram/kg/day) of recombinant human IL-6 on days 1-5 and 8-12 of each 28-day course (1-h trial) or on days 1-5 of each 21-day course (120-h trial). Treatment was administered in regular inpatient wards and in outpatient clinics and was withheld in the event of grade 3 toxicity. Sixty-nine patients (1-h trial, n = 40; 120-h trial, n = 29) were enrolled, including 27 with renal cancer and 16 with melanoma. All were ambulatory, and 40 were asymptomatic. Fever (97%), anemia (78%), fatigue (56%), nausea or vomiting (49%), and elevated serum transaminase levels (42%) were the most frequent toxicities. Transient hypotension developed in 23 patients (33%). There were three deaths during the study due to progressive disease and/or infection. There were no objective responses. Dose-related increases in platelet counts and C-reactive protein levels were detected in most patients. Principal dose-limiting toxicities included atrial fibrillation (1 episode in the 1-h trial and 4 episodes in the 120-h trial) and neurological toxicities (3 episodes in the 1-h trial and 4 episodes in the 120-h trial). The neurological toxicities included confusion, slurred speech, blurred vision, proximal leg weakness, paraparesis, and ataxia. These effects were transient and reversed when IL-6 was discontinued. IL-6 can be given by i.v. infusion at biologically active doses with acceptable toxicity. Dose-limiting toxicities consisted mainly of a spectrum of severe but transient neurological toxicities and occasional episodes of atrial fibrillation. The maximum tolerated doses recommended for use with these i.v. schedules in Phase II trials are 100 microgram/kg/day by daily x5 1-h infusion and 30 microgram/kg/day by 120-h infusion. Phase II trials will be performed to determine the antitumor activity of IL-6 and better define its toxicity. Patients in these and other IL-6 studies should be monitored closely for neurological and cardiac effects.

Hormonal regulation of expression of the endogenous and transfected human growth hormone gene.

Expression of the endogenous human GH (hGH) gene in response to glucocorticoids, thyroid hormone, and insulin was studied in cultures of dispersed GH-secreting human pituitary adenomas. Results were compared to those obtained when the hGH gene was transfected into rat pituitary tumor cells (GC). In the human pituitary cells the glucocorticoid dexamethasone [(Dex) 10(-6) M] increased the release of GH and the levels of GH mRNA by 2 to 4-fold (P less than 0.05). T3 (10(-8) M) had no effect on GH mRNA but increased hGH release by 2- to 6-fold (P less than 0.01). Insulin (5 x 10(-9) M) alone had no significant effect on either hGH mRNA or protein, but blunted the effect of Dex. Among 11 of 18 GC cell clones transfected with the hGH gene with detectable hGH mRNA expression, Dex increased hGH mRNA levels in seven and T3 treatment reduced hGH mRNA levels in eight. Conversely, rat GH mRNA levels from the endogenous rat gene were increased by either Dex or T3 in all 18 clones. Insulin alone or in combination with T3 or Dex was found to increase hGH mRNA levels in some cell lines and to decrease hGH mRNA levels in others; these effects were correlated strongly (r = 0.88; P less than 0.001) with the influence of insulin on the endogenous rat GH gene, implying that individual cellular differences can simultaneously affect the insulin responsiveness of both genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin regulation of rat growth hormone gene expression.

Insulin has been shown previously to inhibit basal and glucocorticoid- or T3-stimulated rat GH (rGH) synthesis, secretion, and mRNA levels in cultured rat pituitary tumor cells (GH3 cells) or pituitaries. The effects of insulin on rGH gene expression in GH3 cells were examined in greater detail in the current studies. Cells were deinduced for 5 days in medium devoid of steroids, T3, and insulin. Cells were then treated for 48 h with insulin (5 X 10(-9) M), dexamethasone (Dex; 10(-6) M), T3 (10(-8) M), insulin plus Dex, or insulin plus T3. When media and hormones were not replaced daily the results were similar to those obtained previously. Insulin decreased both basal and glucocorticoid-stimulated rGH mRNA levels to approximately 70% of control levels, as measured by cytoplasmic dot hybridization. By contrast, when media and hormones were replaced daily, rGH mRNA levels increased by 1.5 to 7-fold in response to insulin in the absence or presence of Dex or T3, measured by both cytoplasmic dot hybridization and RNA (Northern) blotting. Dex increased rGH mRNA levels under both sets of conditions, verifying the specific nature of the insulin influence. Maximum rGH gene expression was achieved after a 48-h exposure to insulin. The observed insulin effects were probably mediated through insulin rather than insulin-like growth factor I or II receptors, since the concentration of insulin employed was near the Kd of the hormone for its receptor measured in the same cells. These results suggest that insulin is capable of regulating rGH gene expression. The action of insulin can be either positive or negative and is influenced by the metabolic state of the cell.

Phase I multicenter trial of interleukin 6 therapy after autologous bone marrow transplantation in advanced breast cancer.

Our purpose was to determine the maximum tolerated dosage of rhIL-6 after high-dose cytotoxic chemotherapy and autologous BMT in patients with advanced breast cancer. Twenty patients (median age 43.5 years) received either CY and thiotepa (n = 3) or CY, thiotepa and carboplatin (n = 17) for 4 days. Unpurged autologous BM was reinfused 72 h later. Daily rhIL-6 therapy began the day of marrow infusion and continued until recovery of neutrophils (> or = 1.5 x 10(9)/l) and platelets (> or = 50 x 10(9)/l) or for a maximum of 28 days at a dosage of 0.3 microgram/kg/day (n = 7), 1 microgram/kg/day (n = 6) or 3 micrograms/kg/day (n = 7). Two of the initial 4 patients given rhIL-6 at 0.3 mu/kg i.v. experienced grade 4 hyperbilirubinemia, so subsequent patients received s.c. rhIL-6. Most toxicities attributable to rhIL-6 were reversible or mild constitutional symptoms, but dose-limiting grade 4 hyperbilirubinemia also occurred in 3 of the 7 patients receiving the 3 micrograms/kg dose. At the 0.3 and 1 microgram/kg/day doses, 8 of 13 patients completed the study vs. only 2 of 7 at the 3 micrograms/kg/day dose. During rhIL-6 treatment, neutrophil recovery (> or = 500 x 10(6)/l) occurred in 12 patients and platelet recovery (> or = 20 x 10(9)/l) occurred in 6 patients, 5 of whom received the 0.3 or 1 microgram/kg/day s.c. dose. The maximal tolerated dose of rhIL-6 after autologous BMT appeared to be 1 microgram/kg/day s.c., a dose appreciably lower than the maximal tolerated dose after conventional cytotoxic therapy.

Integrin-mediated interactions with extracellular matrix proteins for nucleus pulposus cells of the human intervertebral disc.

The extracellular matrix (ECM) of the human intervertebral disc is rich in molecules that interact with cells through integrin-mediated attachments. Porcine nucleus pulposus (NP) cells have been shown to interact with laminin (LM) isoforms LM-111 and LM-511 through select integrins that regulate biosynthesis and cell attachment. Since human NP cells lose many phenotypic characteristics with age, attachment and interaction with the ECM may be altered. Expression of LM-binding integrins was quantified for human NP cells using flow cytometry. The cell-ECM attachment mechanism was determined by quantifying cell attachment to LM-111, LM-511, or type II collagen after functionally blocking specific integrin subunits. Human NP cells express integrins ß1, α3, and α5, with over 70% of cells positive for each subunit. Blocking subunit ß1 inhibited NP cell attachment to all substrates. Blocking subunits α1, α2, α3, and α5 simultaneously, but not individually, inhibits NP cell attachment to laminins. While integrin α6ß1 mediated porcine NP cell attachment to LM-111, we found integrins α3, α5, and ß1 instead contributed to human NP cell attachment. These findings identify integrin subunits that may mediate interactions with the ECM for human NP cells and could be used to promote cell attachment, survival, and biosynthesis in cell-based therapeutics.

Work toward real-time control of a cortical neural prothesis.

Implantable devices that interact directly with the human nervous system have been gaining acceptance in the field of medicine since the 1960's. More recently, as is noted by the FDA approval of a deep brain stimulator for movement disorders, interest has shifted toward direct communication with the central nervous system (CNS). Deep brain stimulation (DBS) can have a remarkable effect on the lives of those with certain types of disabilities such as Parkinson's disease, Essential Tremor, and dystonia. To correct for many of the motor impairments not treatable by DBS (e.g. quadriplegia), it would be desirable to extract from the CNS a control signal for movement. A direct interface with motor cortical neurons could provide an optimal signal for restoring movement. In order to accomplish this, a real-time conversion of simultaneously recorded neural activity to an online command for movement is required. A system has been established to isolate the cellular activity of a group of motor neurons and interpret their movement-related information with a minimal delay. The real-time interpretation of cortical activity on a millisecond time scale provides an integral first step in the development of a direct brain-computer interface (BCI).

Diagnostic accuracy of M-mode echocardiography in active infective endocarditis and prognostic implications of ultrasound-detectable vegetations.

Sensitivity, specificity, diagnostic accuracy, and prognostic implications of the M-mode echocardiographic pattern of vegetations were examined prospectively in consecutive patients referred with potential active infective endocarditis (IE). A pattern of definite echo vegetations was present in 37% of 51 patients diagnosed clinically to have active IE. Specificity in 138 patients without IE was 96%. Diagnostic accuracy of a positive test was 76% and that of a negative test was 80%. Five of six false positive studies involved patients with prior IE or valvular thrombosis. If possible echo vegetations were included, sensitivity increased to 47% and specificity decreased to 89%. Echographic vegetations were significantly correlated with congestive heart failure and need for valve replacement and/or death. Seven of eight patients with definite aortic valve vegetations died or required surgery, compared with 1 of 11 patients with mitral or tricuspid vegetations alone. Prognostic importance of echocardiographically documented vegetations appears to depend upon their site within the heart.

Interleukin-6-associated anemia: determination of the underlying mechanism.

Recombinant human interleukin-6 (rhIL-6) is a pluripotent cytokine with proinflammatory, antitumor, and growth factor effects. Clinical investigations of rhIL-6 either alone as immunotherapy or as a colony-stimulating factor in conjunction with chemotherapy have shown a dose-dependent, rapid onset, and largely reversible decrease in venous hematocrit levels. In an effort to determine the mechanism for the rhIL-6-associated anemia, we measured red blood cell volume serially in patients receiving rhIL-6 at either 30 micrograms/kg/day as a 120-hour continuous intravenous infusion (renal cell carcinoma) or 100 micrograms/kg/d intravenously over 1 hour for 5 days (melanoma) as part of two separate phase II trials. Radioisotope dilution assays with 51Cr-labeled autologous red blood cells and hemolysis screens were performed on day 1 before the initiation of therapy and on day 5 shortly before the end of therapy. In the 6 patients studied, the mean decrease in hemoglobin concentration was 1.9 +/- 0.94 g/dL. The mean decrease in the hematocrit level was 6% +/- 2% and the mean increase in total blood volume was 731 +/- 337 mL. These changes were explained by a mean decrease in red blood mass of 106 +/- 109 mL and a mean increase in plasma volume of 743 +/- 289 mL. The decrease in red blood cell mass was largely explained by phlebotomy during the hospitalization, but was not statistically significant (paired t-test, P = .06). All other changes were statistically significant (P < .05). Simple regression analysis indicated that the decrease in hematocrit level and increase in plasma volume were related (y = -1.78 - .0066X; R = -.74). Measurements of lactate dehydrogenase, bilirubin, haptoglobin, and reticulocyte counts and serial stool hemoccults did not indicate hemolysis or blood loss. We conclude that the anemia caused by IL-6 is caused by an increase in plasma volume.

Effect of interface/offset (I/O) adjustment on collection efficiency using the Fenwal CS3000 Plus Blood Cell Separator for peripheral blood progenitor cell collection.

Peripheral blood progenitor cells (PBPC) reside within the mononuclear cell (MNC) component of the blood and can be collected using a number of apheresis devices, including the Fenwal CS3000 Plus Blood Cell Separator. Increased MNC collection efficiency, therefore, may reduce the number of apheresis required to achieve collection goals. In this study, patients were divided into groups by absolute MNC count to determine the effect of interface detector offset (I/O) adjustment on MNC collection efficiency. Apheresis products from 104 procedures collected using a standard I/O setting of 100 were compared with 121 collections for which the I/O setting was adjusted according to the preapheresis MNC count. Adjustment of the I/O setting in this manner had no statistically significant impact on the per kilogram dose of MNC collected. The data did show that MNC collection efficiency was reduced as both the MNC count and I/O setting increased, as the collection efficiency was greatest for patients with the lowest peripheral MNC counts and was inversely correlated with the preapheresis MNC count. Although contamination of the product with platelets was drastically reduced at higher I/O settings, there was a concomitant rise in RBC contamination. We conclude that a standard setting of 100 is preferable to adjustment of the I/O setting as a function of the preapheresis MNC count.