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Recently, several reports of lineage-negative (lin(-)) CD34(-) cells with in vivo hematopoietic activity have focused interest on the properties and growth factor response characteristics of these cells. We have now identified a combination of 5 growth factors that are necessary and sufficient to stimulate a marked mitogenic and differentiation response by a subset of human lin(-)CD34(-)CD38(-) cells present in normal adult human marrow and granulocyte colony-stimulating factor (G-CSF)-mobilized blood. Less than 0.1% of the cells in highly purified (including doubly sorted) lin(-)CD34(-)CD38(-) cells from these 2 sources formed colonies directly in semisolid medium or generated such cells after 6 weeks in long-term culture. Nevertheless, approximately 1% of the same lin(-)CD34(-)CD38(-) cells were able to proliferate rapidly in serum-free liquid suspension cultures containing human flt-3 ligand, Steel factor, thrombopoietin, interleukin-3 (IL-3), and hyper-IL-6 to produce a net 28- +/- 8-fold increase in total cells within 10 days. Of the cells present in these 10-day cultures, 5% +/- 2% were CD34(+) and 2.5% +/- 0.9% were erythroid, granulopoietic, megakaryocytopoietic, or multilineage colony-forming cells (CFC) (13 +/- 7 CFC per lin(-)CD34(-)CD38(-) pre-CFC). In contrast to lin(-)CD34(+)CD38(-) cells, this response of lin(-)CD34(-)CD38(-) cells required exposure to all of the 5 growth factors used. Up to 1.7 x 10(5) lin(-)CD34(-) adult marrow cells failed to engraft sublethally irradiated NOD/SCID-beta(2)M(-/-) mice. These studies demonstrate unique properties of a rare subset of lin(-)CD34(-)CD38(-) cells present in both adult human marrow and mobilized blood samples that allow their rapid proliferation and differentiation in vitro within an overall period of 3 to 4 weeks. The rapidity of this response challenges current concepts about the normal duration and coordinated control of these processes in adults.

Objective: To determine the duration of breastfeeding in the Sudbury Region and to identify the reasons why mothers wean before the Canadian Paediatric Society's recommended six month period., Methods: Questionnaires addressing factors that influence the duration of breastfeeding were mailed to 350 breastfeeding mothers at one/two weeks, three months and six months after their postpartum discharge from hospital., Results: Forty percent of mothers breastfed for the recommended six month period. Reported factors positively influencing longer durations of breastfeeding were higher education, higher family income, parity, previous breastfeeding experience, decision to breastfeed before the child was born and late introduction to solids. Reasons for weaning included perceived insufficient milk supply, fatigue, breast problems and return to work. Mothers' top three choices of services were home visits, telephone hot line and television programs., Conclusions: The duration of breastfeeding in the Sudbury Region is lower than the provincial average. Several modifiable factors associated with duration of breastfeeding were identified.

The impact of a policy to introduce a simple health maintenance protocol systematically to all patients belonging to a private practice is reported. Results after 18 months' experience in over 1400 patients indicate that (1) physician compliance was excellent (97% of eligible patients were included, and physician time taken to introduce the protocol at the index visit took less than 4 minutes), and (2) patient acceptance (which varied from procedure to procedure) was good to excellent (minimum acceptance: 77% for sigmoidoscopy; maximum acceptance: 97% for cholesterol screening). For patients seen once, acceptance rates for procedures were generally comparable to prior published performance rates for highly selected patient populations. Integration of a simple health maintenance protocol into routine office care of unselected primary care patients was feasible, effective, and acceptable to patients. Patient refusal was a minor barrier to performance of health maintenance.

Succulent stems of Cissus quadrangularis L. (Vitaceae) contain glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. The CO(2) and water gas exchanges of detached internodes were typical for Crassulacean acid metabolism plants. During three physiological phases, e.g. in the dark, in the early illumination period after stomata closure, and during the late light phase with the stomata wide open, (15)NH(4)Cl was injected into the central pith of stem sections. The kinetics of (15)N labeling in glutamate and glutamine suggested that glutamine synthetase was involved in the initial ammonia fixation. In the presence of methionine sulfoximine, an inhibitor of glutamine synthetase, the incorporation of (15)N derived from (15)NH(4)Cl was almost completely inhibited. Injections of amido-(15)N glutamine demonstrated a potential for (15)N transfer from the amido group of glutamine into glutamate which was suppressed by the glutamate synthase inhibitor, azaserine. The evidence indicates that glutamine synthetase and glutamate synthase could assimilate ammonia and cycle nitrogen during all phases of Crassulacean acid metabolism.

Wild-type Aspergillus nidulans grew equally well on NH4Cl, KNO3 or glutamine as the only nitrogen source. NADP+-dependent glutamate dehydrogenase (EC 1.4.1.4) and glutamine synthetase (GS; EC 6.3.1.2) activities varied with the type and concentration of nitrogen source supplied. Glutamate synthase (GOGAT) activity (EC 1.4.7.1) was detected but it was almost unaffected by the type and concentration of nitrogen source supplied. Ion exchange chromatography showed that the GOGAT activity was due to a distinct enzyme. Azaserine, an inhibitor of the GOGAT reaction, reduced the glutamate pool by 60%, indicating that GOGAT is involved in ammonia assimilation by metabolizing the glutamine formed by GS.

Nitrogen metabolism was examined in senescent flag leaves of 90- to 93-day-old wheat (Triticum aestivum L. cv Yecora 70) plants. CO(2) assimilation and the levels of protein, chlorophyll, and nitrogen in the leaves decreased with age. Glutamine synthetase activity decreased to one-eighth of the level in young flag leaves. Detached leaves were incubated (with the cut base) in (15)N-labeled NH(3), glutamate, or glycine in the light (1.8 millieinstein per square meter per second) at 25 degrees C in an open gas exchange system under normal atmospheric conditions for up to 135 minutes. The (15)N-enrichment of various amino acids derived from these (15)N-substrates were examined. The amido-N of glutamine was the first (15)N-labeled product in leaves incubated with (15)NH(4)Cl whereas serine, closely followed by the amido- and amino-N of glutamine, were the most highly (15)N-labeled products during incubation with [(15)N]glycine. In contrast, aspartate and alanine were the first (15)N-labeled products when [(15)N] glutamate was used. These results indicate that NH(3) was assimilated via glutamine synthetase and glutamate synthase activities and the photorespiratory nitrogen cycle remained functional in these senescent wheat flag leaves. In contrast, an involvement of glutamate dehydrogenase in the assimilation of ammonia could not be detected in these tissues.