Minimization of CD34+ cell enumeration variability using the ProCOUNT standardized methodology.

The dose of cells expressing the surface antigen CD34 (CD34+) has been shown to be a reliable predictor of the time to engraftment following transplantation of PBPC to support high-dose chemotherapy. However, evaluation of rare cells is complicated by a number of factors, including the variability in operator and technical procedures. Recently, Becton Dickinson Immunocytometry Systems introduced a new CD34+ cell analysis system, the ProCOUNT cell enumeration kit, which automates the analysis of CD34+ cells and minimizes the variabilities of this procedure. We have evaluated the ProCOUNT system in comparison to a standard CD34 cell analysis (based on the Milan approach) using leukapheresis products from patients and normal donors mobilized with chemotherapy plus recombinant human G-CSF (rhG-CSF) or with rhG-CSF alone. In addition, we compared these analyses using CD34+ cell-selected mobilized leukapheresis products with purities of 75% or greater. The standard CD34 cell analysis methodology quantitated the frequency of cells identified as CD45+, low side scatter, and CD34+. A high correlation coefficient was obtained between the ProCOUNT methodology and the standard CD34 cell analysis methodology for cells obtained from leukapheresis products mobilized with chemotherapy plus rhG-CSF (r = 0.98), rhG-CSF alone (r = 0.96), and CD34+-selected mobilized leukapheresis products (r = 0.83). A comparison was also made between technicians using both analysis methods. Whereas the correlation coefficient between two technicians using the standard methodology was r = 0.77, the correlation coefficient was much higher when using ProCOUNT (r = 0.99). These data demonstrate that the use of ProCOUNT is associated with less variability between data analyzed by different operators. Also, ProCOUNT is consistent with existing CD34+ cellular analysis methodologies. An additional advantage is the ability to determine the absolute concentration of CD34+ cells, thereby allowing calculation of total CD34+ cell numbers without using WBC counts, which also have inherent errors. The ProCOUNT system provides an automated analysis procedure that minimizes the variables in CD34+ cell analysis and may be useful for standardization of methodology between laboratories.

Short-term inhibition of parathyroid hormone secretion by a calcium-receptor agonist in patients with primary hyperparathyroidism.

BACKGROUND: Surgery is the usual therapy for patients with primary hyperparathyroidism. We investigated the ability of a calcimimetic drug that inhibits parathyroid hormone secretion in vitro to decrease serum parathyroid hormone and calcium concentrations in patients with this disorder. METHODS: We performed a randomized, placebo-controlled study of single oral doses of 4 to 160 mg of the calcium-receptor agonist drug R-568 in 20 postmenopausal women with mild primary hyperparathyroidism. At base line, the mean (+/-SE) serum calcium concentration was 10.7+/-0.2 mg per deciliter (2.67+/-0.05 mmol per liter). Serum parathyroid hormone and calcium were measured repeatedly after each dose, and safety was assessed. RESULTS: Administration of R-568 resulted in a dose-dependent inhibition of parathyroid hormone secretion. The mean serum parathyroid hormone concentration, which was 77+/-11 pg per milliliter (18.8+/-2.7 pmol per liter; normal range, 16 to 65 pg per milliliter [3.9 to 15.9 pmol per liter) at base line, fell by 26+/-8 percent after 20 mg of R-568 (P=0.03), by 42+/-7 percent after 80 mg (P = 0.01), and by 51+/-5 percent after 160 mg (P=0.005). Serum ionized calcium concentrations fell only after the 160-mg dose, with the decrease closely following the decrease in the serum parathyroid hormone concentration. CONCLUSIONS: The calcimimetic drug R-568 reduces serum parathyroid hormone and ionized calcium concentrations in postmenopausal women with primary hyperparathyroidism.

The impact of Filgrastim schedule variation on hematopoietic recovery post-chemotherapy.

BACKGROUND: A phase 2 trial was done to study effects of varying treatment schedule of Filgrastim (r-metHuG-CSF) on hematologic recovery following chemotherapy. PATIENTS AND METHODS: Forty-six patients with extensive small-cell carcinoma of the lung were randomized to receive one of three Filgrastim schedules following cyclophosphamide, doxorubicin, and etoposide (CAE) chemotherapy for up to six cycles of treatment. Chemotherapy was delivered on days 1-3 of each 21-day cycle with Filgrastim initiated at 5 micrograms/kg/day subcutaneously (SC) beginning on day 4, day 6, or day 8 and continuing until post-nadir neutrophil recovery. RESULTS: During the first cycle of chemotherapy, the duration of neutropenia was similar for all three schedules; however, the pattern of absolute neutrophil count (ANC) recovery differed. In subsequent cycles of treatment, an improvement in the severity of neutropenia occurred in patients on the day-4 and day-6 schedules compared with the first cycle of chemotherapy. By contrast, patients on the day-8 schedule continued to experience neutropenia similar to that seen in cycle one. Patients on the day-8 schedule also experienced a greater magnitude of grade IV thrombocytopenia in later cycles of treatment. CONCLUSION: Timing of Filgrastim administration post-chemotherapy has profound effects on hematologic recovery. Delay of Filgrastim until day 8 was associated with suboptimal hematologic recovery compared with administration of Filgrastim on day 4 or day 6. Initiation of Filgrastim on day 4 or day 6 showed a similar pattern of hematologic recovery. Beginning Filgrastim on day 6 is associated with a decrease in the total dose of Filgrastim administered.

Entomological studies at an enzootic Venezuelan equine encephalitis virus focus in Guatemala, 1977-1980.

The ecology of several potential mosquito vectors of Venezuelan equine encephalitis (VEE) alphavirus was studied in an enzootic focus of that virus on the Pacific coast of Guatemala over a four-year period. Four species-Culex taeniopus, Mansonia titillans, Culex nigripalpus and Aedes taeniorhynchus-were most prevalent during the wet season when transmission normally occurs. However, only Cx. taeniopus yielded VEE virus. The bloodfeeding patterns of these species revealed that Ae. taeniorhynchus and Ma. titillans fed almost exclusively on bovine and equine hosts. Conversely, Cx. nigripalpus was highly ornithophilic but occasionally fed on mammals. Cx. taeniopus exhibited a wide host range, utilizing both large and small mammals as well as birds and, rarely, reptiles. The versatility in feeding pattern displayed by this mosquito coupled with its ability to become infected with relatively low levels of enzootic VEE virus suggests that vertebrates other than rodents may serve as amplifying hosts in this habitat. Nepuyo virus was also isolated from Cx. taeniopus, suggesting that this mosquito might be an endemic vector of this rodent-associated bunyavirus. A single isolate of St. Louis encephalitis virus was made from Cx. nigripalpus.

Mesenteronal infection threshold of an epizootic strain of Venezuelan encephalitis virus in Culex (Melanoconion) taeniopus mosquitoes and its implication to the apparent disappearance of this virus strain from an enzootic habitat in Guatemala.

Culex (Melanoconion) taeniopus is a vector of Venezuelan encephalitis (VE) virus at a marsh focus in Guatemala and has low mesenteronal thresholds for infection by and transmission of two enzootic strains of VE virus. In contrast, samples of natural populations and subsequent F2 and F4 generations of these mosquitoes have a high mesenteronal threshold for infection by an epizootic VE strain isolated at the same marsh during the end of the 1969 VE epidemic-equine epizootic. The resistance of Cu. (Mel). taeniopus to mesenteronal infection by this VE strain probably represents a key factor in the apparent disappearance of epizootic VE virus from the marsh focus following the 1969 outbreak.