Cadmium bioavailability

Cadmium slowly accumulates in the liver and kidney and has a long biological half-life, estimated to be 2-3 decades in the kidney. If the kidney cadmium concentration reaches a critically high level, proximal tubular damage results, which can be followed by severe bone mineral loss. There are only a few measurements of cadmium bioavailability in foods; however, the data are indicative of lower utilization from foods than from inorganic salts. In animal tissues cadmium is bound primarily to a heat-resistant small protein with a high cysteine content (metallothionein), whereas little is known about the form in which cadmium occurs in the edible parts of plants. Low intakes of many nutrients exacerbate the effects of cadmium and supplemental intakes are protective. Newborn and young animals absorb much higher quantities of cadmium than adults. There is some evidence in animals that females may be more adversely affected than males. Itai-itai disease, a painful disease with kidney damage and bone demineralization, occurred in elderly Japanese women who had borne several children and who were exposed to cadmium via food and drinking water. Inasmuch as cadmium in the U.S. food supply affords an estimated safety factor of only 4- to 15-fold, it is important to establish factors that affect the bioavailability of cadmium from foods.     

Sources of sucrose translocated from illuminated sugar beet source leaves

A search for source leaf sucrose pools that differed in their relation to export was carried out in photosynthesizing leaves of Beta vulgaris L. The time course of depletion of [¹⁴C]sucrose in a leaf in unlabeled CO₂ following steady state labeling provided evidence for two distinct sucrose pools. After the start of the light period, leaf blade sucrose remained constant although it exchanged between the two pools. Newly synthesized sucrose destined for export passed through one pool more rapidly than through the other. All of the leaf blade sucrose appeared to exchange with export sucrose. Modeling and regression analysis of [¹⁴C]sucrose data provided a means for estimating the size of the two pools. From 20 to 40% of the sucrose was calculated to be present in the pool that provided the less direct path to export; this was likely vacuolar sucrose. The remainder of the sucrose in the blade was probably in the cytoplasm and veins. Added amounts of leaf blade sucrose, produced in response to elevated CO₂, appeared to be stored mainly in the vacuolar compartment.     

Role of basidiospores as inocula of mycorrhizal fungi of birch

Summary Fruitbodies of sheathing mycorrhizal fungi collected under birch (Betula pendula andB. pubescens) were suspended over pots of soil and the resulting spore-supplemented soils were planted with sedlings ofB. pendula. Inocybe lacera, I. lanuginella, Hebeloma sacchariolens andH. leucosarx formed mycorrhizas readily.Lactarius pubescens andLeccinum roseofracta did not form mycorrhizas from basidiospore inocula, even after prolonged periods of seedling growth.Paxillus involutus gave equivocal results, perhaps because the soil was unsuitable for this species. Storage of the basidiospore-supplemented soils for 6 months in outdoor conditions or in a growth room at 18°C did not materially alter the results.The results are discussed in relation to the concept of mycorrhizal succession.     

Measurement of nucleoside kinases in crude tissue extracts

The measurements of deoxyadenosine kinase, adenosine kinase, and deoxycytidine kinase were examined in human placental cytosol to achieve a valid and reliable assay linear with time and protein. Our studies confirm the need to inhibit deaminase enzymes, since deoxyadenosine and deoxycytidine undergo extensive deamination and phosphorolysis. The use of a uniformly labeled nucleoside substrate introduced an artifact because the chromatographic behavior of the deoxyribose-1-phosphate, formed during the assay, was difficult to distinguish from the deoxynucleoside phosphate product. Accurate product identification was also essential. Finally, the substitution of GTP in place of ATP as the phosphate donor, the addition of a sulfhydryl reducing agent and a monovalent cation need to be considered when an assay is optimized. The use of these methods have lead to valid assays in placental cytosol that are linear with time and protein. Consideration of these important principles are necessary when establishing a valid and reliable nucleoside kinase assay in a crude tissue preparation.     

Resistance to Osborne's Cyst Nematode in Selected Nicotiana Species

Resistance to an undescribed species of Heterodera, Osborne''s cyst nematode, was compared in Nicotiana glutinosa, N. paniculata, N. plumbaginifolia and N. Iongiflora. These species were differentially resistant in greenhouse tests as shown by nematode development, the reaction of the invaded roots, and the expression of resistance in interspecific hybrids.     

Attractant-Directed Motility in Escherichia coli: Requirement for a Fluid Lipid Phase

Attractant-directed motility (chemotaxis) in Escherichia coli has an absolute requirement for a fluid membrane. No such requirement was detected for motility per se.     

DNA values in somatic tissues of Dermestes (Dermestidae: Coleoptera)

The distribution of DNA values in some somatic tissues of seven Dermestes species has been investigated. In all cases the DNA values are distributed as members of a doubling series. Distributions are found to be similar between species and sexes for the same tissue but different between tissues in the same species. Species DNA values derived from somatic tissues agree with DNA values previously determined for spermatids. These data are discussed in relation to the range of species DNA values (2.7 x) and the process of differentiation.