PubMed · 893929
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P Bernardo. 1977. Thyroid hormone preparations.. https://doi.org/10.1016/s0003-0465(16)34457-3
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Thlaspi caerulescens has a remarkable ability to hyperaccumulate Zn from soils containing mostly nonlabile Zn. The present study shows that rhizosphere microbes play an important role in increasing the availability of water-soluble Zn in soil, thus enhancing Zn accumulation by T. caerulescens. The addition of bacteria to surface-sterilized seeds of T. caerulescens sown in autoclaved soil increased the Zn concentration in shoots 2-fold as compared to axenic controls; the total accumulation of Zn was enhanced 4-fold. When the same experiment was conducted with Thlaspi arvense, a nonaccumulator, bacteria had no effect on shoot Zn accumulation although they increased water-soluble Zn concentrations available to both Thlaspi species by 22-67% as compared to the axenic controls. Further evidence that bacteria increase the availability of water-soluble Zn in soil was obtained when liquid media that had supported bacterial growth mobilized 1.3-1.8-fold more Zn from soil as compared to axenic media. Other experiments with agar media showed that bacteria did not facilitate an increase in the rate of soluble Zn transport into the root nor did they enlarge the surface area of the roots of either Thlaspi species. Thus, the bacterially mediated increase in the dissolution of Zn from the nonlabile phase in soil may enhance Zn accumulation in T. caerulescens shoots.
The metal hyperaccumulating plant Thlaspi caerulescens is effective in depleting plant-available metals from the soil. We hypothesized that this reduction of toxic metals in the rhizosphere of T. caerulescens would increase the growth of less metal-tolerant plants with their roots permitted to intermingle and develop coincident rhizospheres. The extent of rhizosphere interaction between T. caerulescens and a coplanted nonaccumulator species, Thlaspi arvense, was controlled using barriers. Two media with elevated concentrations of water-extractable Zn were prepared by enriching one soil with zinc oxide (ZnO) or zinc sulfide (ZnS). The shoot mass of T. arvense was increased by 30% when its roots were permitted to intermingle with those of T. caerulescens in the ZnO treatment. The concomitant 2-3-fold reduction in shoot Zn concentration in T. arvense confirmed that its improved growth was associated with reduced uptake and phytotoxicity of Zn. Thlaspi arvense also showed increased growth and reduced metal uptake when cocropped with T. caerulescens in the ZnS treatment. We conclude that the strong Zn accumulation by T. caerulescens might enhance the establishment and development of surrounding less-tolerant species on soils that are naturally- or anthropogenically-enriched with metals.
The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, interactions, and dosage of nateglinide are reviewed. Nateglinide is an oral hypoglycemic agent approved for use alone or in combination with metformin as an adjunct to diet and exercise for the treatment of type 2 diabetes mellitus. Nateglinide, an amino acid derivative of D-phenylalanine, stimulates the secretion of insulin by binding to the ATP potassium channels in pancreatic beta cells. The result is an increase in beta-cell calcium influx, which leads to rapid, short-lived insulin release. The drug is rapidly and completely absorbed in the small intestine. The estimated bioavailability is 72%. Nateglinide is highly bound to plasma proteins, is metabolized extensively by the liver, and has an elimination half-life of 1.4 hours. Several clinical trials of nateglinide, alone and in combination with other oral hypoglycemic agents, have found the drug to be safe, effective, and well tolerated. The most common adverse effects are nausea, diarrhea, dizziness, and lightheadedness. There is a potential for interactions between nateglinide and medications affected by the cytochrome P-450 isoenzyme system. Dosage regimens ranging from 60 to 240 mg have been evaluated. The maximum effective dosage is 120 mg taken 10 minutes before meals three times a day. Nateglinide is an alternative to second-generation sulfonylureas for the treatment of type 2 diabetes mellitus. Additional comparative trials are needed to fully elucidate nateglinide's role.