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Michael Long

Publications and source records attributed to Michael Long.

7 recordsLinked to original sources

Prednisolone pharmacokinetics in the presence and absence of ritonavir after oral prednisone administration to healthy volunteers.

Corticosteroid therapy has been associated with bone toxicities (eg, osteonecrosis) and Cushing syndrome in HIV-infected patients; this may be partially attributable to a pharmacokinetic drug interaction between HIV protease inhibitors and corticosteroids. The purpose of this study was to characterize the influence of low-dose ritonavir on prednisolone pharmacokinetics in healthy subjects. Ten HIV-seronegative volunteers were given single oral doses of prednisone, 20 mg, before (baseline) and after receiving ritonavir, 200 mg, twice daily for 4 and 14 days. After each prednisone dose, serial blood samples were collected and prednisolone concentrations were determined; pharmacokinetic parameter values were compared between the groups. Geometric mean ratios (GMRs, 90% confidence interval [CI]) of the prednisolone area under the plasma concentration versus time curve (AUC0-infinity) after 4 and 14 days of ritonavir versus baseline were 1.41 (90% CI: 1.08 to 1.74) and 1.30 (90% CI: 1.09 to 1.49), respectively (P = 0.002 and P = 0.004, respectively). GMRs of prednisolone apparent oral clearance (Cl/F) were 0.71 (09% CI: 0.57 to 0.93) and 0.77 (90% CI: 0.67 to 0.92) after 4 and 14 days of ritonavir versus baseline, respectively (P = 0.0004 and P = 0.0003, respectively). Ritonavir significantly increased the systemic exposure of prednisolone in healthy subjects. Results from this investigation suggest that corticosteroid exposure is likely elevated in HIV-infected patients receiving protease inhibitors.

Adult↗

Minimal contribution of marrow-derived endothelial precursors to tumor vasculature.

During embryogenesis, vascular and hemopoietic cells originate from a common precursor, the hemangioblast. Recent evidence suggests the existence of endothelial precursors in adult bone marrow cells, but it is unclear whether those precursors have a role in tumor neovascularization. In this report, we demonstrate that murine bone marrow contains endothelial progenitors, which arise from a cell with self-renewing capacity, and can integrate into tumor microvasculature, albeit at a very low frequency. A transgenic double-reporter strategy allowed us to demonstrate definitively that tumor bone marrow-derived endothelial cells arise by transdifferentiation of marrow progenitors rather than by cell fusion. Single cell transplants showed that a common precursor contributes to both the hemopoietic and endothelial lineages, thus demonstrating the presence of an adult hemangioblast. Furthermore, we demonstrate that increased vascular endothelial growth factor (VEGF)-A secretion by tumor cells, as well as activation of VEGF receptor-2 in bone marrow cells does not alter the mobilization and incorporation of marrow-derived endothelial progenitors into tumor vasculature. Finally, in human umbilical cord blood cells, we show that endothelial precursors make up only approximately 1 in 10(7) mononuclear cells but are highly enriched in the CD133+ cell population. By ruling out cell fusion, we clearly demonstrate the existence of an adult hemangioblast, but the differentiation of marrow stem cells toward the endothelial lineage is an extremely rare event. Furthermore, we show that VEGF-A stimulation of hemopoietic cells does not significantly alter this process.

AC133 Antigen↗

Phase I and pharmacokinetic study of docetaxel combined with melphalan and carboplatin, with autologous hematopoietic progenitor cell support, in patients with advanced refractory malignancies.

The purpose of this study was to define the maximal tolerated dose (MTD), extramedullary toxicities, and pharmacokinetics of docetaxel combined with high-dose melphalan and carboplatin with autologous hematopoietic progenitor cell support. Fifty-nine patients with advanced refractory malignancy (32 breast cancer, 10 non-Hodgkin lymphoma, 6 germ cell tumors, 4 Hodgkin disease, 4 ovarian cancer, 2 sarcoma, and 1 unknown primary adenocarcinoma) with a median of 3 prior chemotherapy regimens and a median of 3 organs involved were enrolled. Treatment included docetaxel (150-550 mg/m2 infused over 2 hours on day -6), melphalan (150-165 mg/m2 infused over 15 minutes from day -5 to -3), and carboplatin (1000-1300 mg/m2 as a 72-hour continuous infusion from day -5). Five patients died from direct regimen-related organ toxicity (2 capillary leak syndrome, 2 enterocolitis, and 1 hepatic toxicity), and 1 additional patient died from pulmonary aspergillosis. The docetaxel MTD was defined as 400 mg/m 2 , combined with melphalan (150 mg/m2 ) and carboplatin (1000 mg/m2 ). The MTD cohort was expanded to enroll a total of 26 patients, 1 of whom died from toxic enterocolitis. The remaining 25 patients presented the following extramedullary toxicity profile, which was manageable and largely reversible: stomatitis, myoarthralgias, peripheral neuropathy, gastrointestinal and cutaneous toxicities, and syndrome of inappropriate antidiuretic hormone secretion. Docetaxel exhibited linear pharmacokinetics in the dose range tested (150-550 mg/m2 ). Pharmacodynamic correlations were noted between the docetaxel area under the curve and peripheral neuropathy or stomatitis. The response rate among 38 patients with measurable disease was 95%, with 47% complete responses. At a median follow-up of 26 months (range, 7-72 months), the 3-year event-free survival and overall survival were 26% and 36%, respectively. In conclusion, a 4-fold dose escalation of docetaxel, combined with melphalan and carboplatin, is feasible with autologous hematopoietic progenitor cell support. The notable activity of this regimen in treatment-refractory patients warrants its further evaluation.

Adolescent↗

Cord blood house dust mite allergen in newborns: relationship to maternal blood levels of allergen and allergen specific IgG and IgE.

BACKGROUND: House dust mite allergen has previously been detected in the cord blood of some newborns but not others. The factors that affect the presence and levels in cord blood of this and possibly other allergens are unknown. OBJECTIVE: To test the hypothesis that the levels of maternal allergen and allergen specific IgG affect the presence and levels of newborn allergen. METHODS: Enzyme-linked immunosorbent assays were used to measure the levels of house dust mite allergen Der p 1 and Der p 1 specific IgG and IgE in paired blood samples from 98 mothers and full-term newborns. RESULTS: Der p 1 was detected in 27 mothers and 12 newborns. None of the 71 mothers who lacked Der p 1 had Der p 1-positive newborns. When present, cord blood Der p 1 levels correlated with and were approximately one third of Der p 1 levels in maternal blood. Cord blood Der p 1 levels also tended to correlate with maternal blood levels of Der p 1 specific IgG but showed little, if any, correlation with maternal blood levels of Der p 1 specific IgE. CONCLUSIONS: When detectable, the levels of an allergen in the blood of newborns correlate with the levels of that allergen in the blood of their mothers and tend to be related to maternal levels of allergen specific IgG.

Adolescent↗

Blastic natural killer cell lymphoma/leukemia: a report of seven cases.

Only a few blastic natural killer (NK) cell leukemias and lymphomas have been reported. As such, the clinicopathologic spectrum of this disease is incompletely understood. We report 7 cases of blastic NK cell lymphoma/leukemia. All patients were men, 5 white and 2 Arab American. All cases exhibited blastic morphologic features and were CD3- and CD56+ with germline T-cell receptor genes. Five cases were CD4+ and involved the skin. Both CD4- cases never involved the skin. Other markers of mature NK cells such as CD16, CD57, and TIA-1 were expressed infrequently. Three cases were CD33+. One CD33+ case had a clonal rearrangement of the immunoglobulin heavy chain gene. Skin and lymph nodes were involved most often, with frequent evolution to a leukemic phase. Initial responses to therapy were achieved in most patients, but the tumors invariably recurred.

Adult↗