The significance of extracellular production and winter photosynthesis to estimates of primary production in a woodland stream community

Both winter photosynthesis and the release of extracellular DOC are commonly ignored in stream production studies. We examined these contributions in a second-order stream under a completely closed deciduous canopy. We estimate that in Sandy Run approximately 26% of the annual autochthonous particulate carbon is produced between December and March. Measured winter rates of photosynthesis were not significantly different than summertime rates. Contrary to implicit assumptions often made about stream primary productivity, winter production was as important as summer production. Highest rates of carbon assimilation, however, were measured in the spring and fall, and were significantly correlated with standing crops of stream algae as measured by chlorophyll concentration. The recovery of released DOC from stream algae indicated that this contribution was equivalent to 5% of the particulate contribution. Rates of DOC production were significantly correlated with rates of particulate production. We estimate that had winter photosynthesis and extracellular DOC production been ignored in Sandy Run, annual productivity would have been underestimated by about a third. This revised version was published online in July 2006 with corrections to the Cover Date.     

Acute leukemia in adults: assessment of remission induction with combination chemotherapy by clinical and cell-culture criteria.

Remission induction was assessed by clinical and cell-culture criteria for 65 patients with acute myelogenous leukemia (AML), 11 patients with chronic myelogenous leukemia (CML) in blast crisis and 19 patients with acute lymphoblastic leukemia (ALL). Cyclophosphamide, cytosine arabinoside and vincristine (CAV) therapy resulted in complete remission in 23 of 50 previously untreated patients with AML and in 3 of the 11 patients with CML. Fourteen patients with ALL responded to vincristine-prednisone induction therapy and two to induction therapy with CAV. The median duration of survival of the responding patients was 2.2 years, compared with 4 months for the patients who did not respond to treatment. Granulopoietic colony formation, assessed by assay of colony-forming units dependent on colony-stimulating activity in culture (CFU-C), was abnormal in 37 of 42 bone marrow aspirates from patients with AML before treatement. CFU-C concentration increased when leukocyte-conditioned medium (LCM) was added to the cultures; 13 cultures had normal or elevated CFU-C concentration with LCM. Marrow cells of patients with ALL or CML in blast crisis demonstrated a similar pattern. Serial studies of marrow CFU-C concentration of 31 patients with AML demonstrated a change to a normal pattern with successful remission induction. Results of this study suggest that administration of purified LCM to leukemic patients might increase granulocyte production from potential but unstimulated granulopoietic precursors. This therapy would lessen the probability of death from infection during remission induction.     

Attitudes and practices of primary care physicians in the management of elevated serum cholesterol levels.

We conducted a telephone survey of 102 randomly selected Ottawa family physicians to determine their attitudes and practices regarding the treatment of hypercholesterolemia. Of the 102, 56% routinely measured serum cholesterol levels in all their patients over the age of 30 years, and 24% did so for patients in more restricted age ranges. The level at which they started dietary therapy averaged 6.95 mmol/L (270 mg/dl); for 25% it was less than 6.22 mmol/L (240 mg/dl). The level at which they started drug therapy averaged 8.9 mmol/L (345 mg/dl); for only 15% was it 7.23 mmol/L (280 mg/dl) or less. Two-thirds were unable to give numerical values to the serum cholesterol levels at which they started diet therapy, and 38% used the upper limits of laboratory normal values as an indication to start therapy. Our findings contrast markedly with results reported for US family physicians, who treat hypercholesterolemia much more aggressively. The variability in practices must be addressed if public campaigns to lower serum cholesterol levels are to be undertaken.     

Plasma cell myeloma: response of melphalan-resistant patients to high-dose intermittent cyclophosphamide

High-dose intermittent cyclophosphamide was used in the treatment of 19 patients with plasma cell myeloma who had demonstrated resistance to melphalan. Good objective improvement was found in six patients and partial responses in five. Patients have survived from three to more than 36 months (estimated median 21 months) after starting cyclophosphamide, and 11 are still alive. The important implications of the lack of cross-resistance between these two alkylating agents are discussed in terms of the mechanisms of cellular resistance to alkylating agents.