Mapping of the K(+)/Na (+) discrimination locus Kna1 in wheat

In saline environments, bread wheat, Triticum aestivum L. (genomes AABBDD), accumulates less Na(+) and more K(+) in expanding and young leaves than durum wheat, T. turgidum L. (genomes AABB). Higher K(+)/Na(+) ratios in leaves of bread wheat correlate with its higher salt tolerance. Chromosome 4D from bread wheat was shown in previous work to play an important role in the control of this trait and was recombined with chromosome 4B in the absence of the Ph1 locus. A population of plants disomic for 4D/4B recombined chromosomes in the genetic background of T. turgidum was developed to investigate the genetic control of K(+)/Na(+) discrimination by chromosome 4D. Evidence was obtained that the trait is controlled by a single locus, designated Kna1, in the long arm of chromosome 4D. In the present work, K(+)/Na(+) discrimination was determined for additional families with 4D/4B chromosomes. The concentrations of Na(+) and K(+)/Na(+) ratios in the youngest leaf blades clustered in two nonoverlapping classes, and all recombinant families could be unequivocally assigned to Kna1 and kna1 classes. The Kna1 locus scored this way was mapped on a short region in the 4DL arm and was completely linked to Xwg199, Xabc305, Xbcd.402, Xpsr567, and Xpsr375; it was also mapped as a quantitative trait. The results of the QTL analysis, based on the K(+)/Na(+) ratios in the young leaves of greenhousegrown plants and flag leaves of field-grown plants, agreed with the position of Knal determined as a qualitative trait. Several aspects of gene introgression by manipulation of the Ph1 locus are discussed.

Parathyroid hormone mRNA levels are increased by progestins and vary during rat estrous cycle

Estrogen increases parathyroid hormone (PTH) mRNA levels in vivo in ovariectomized rats. We now show that the 19-norprogestin R-5020 given to weanling rats or mature ovariectomized rats led to a twofold increase in thyroparathyroid PTH mRNA levels. This increase in PTH mRNA occurred at 24 and 48 h after progesterone but not at 72 h. There were no changes in serum calcium. In vitro, in primary cultures of bovine parathyroid cells, progesterone increased PTH mRNA levels threefold at 10(-8) M and twofold at 10(-9) M after 24 h. Progesterone receptor (PR) mRNA was demonstrated in rat parathyroid tissue by in situ hybridization and in human parathyroid adenoma by immunohisto-chemistry. Changes in PTH mRNA levels during the rat estrous cycle were also studied. At proestrus and estrus PTH mRNA levels were increased significantly by three- and fourfold compared with diestrus. Our results confirm that the parathyroid gland is a target organ for the ovarian sex steroids estrogen and progesterone and are of physiological relevance as shown by the changes during estrus.

New insights into the regulation of parathyroid hormone synthesis and secretion in chronic renal failure

The main factors which regulate parathyroid hormone (PTH) production are calcium, phosphate, vitamin D and the sex steroids, estrogens and progestagins. Hypocalcaemia leads to increased PTH secretion in seconds and minutes, gene expression in hours and parathyroid cell number in weeks and months. Hypercalcaemia leads to a decrease in PTH secretion by its action on the parathyroid cell calcium receptor and no decrease in PTH mRNA concentrations. There is now convincing evidence that phosphate regulates the parathyroids independent of its effect on serum calcium and 1,25-dihydroxyvitamin D3. (1,25(OH)2D3). In vivo in rats hypophosphataemia markedly decreases PTH mRNA and serum PTH independent of its effect on serum calcium and 1,25(OH)2D3. Clinical studies also indicate that phosphate regulates the parathyroids independent of its effect on serum calcium and 1,25(OH)2D3 1,25(OH)2D3 itself has a marked effect on the parathyroids where it decreases PTH gene transcription by a direct action. Parathyroid cell proliferation is regulated by dietary calcium and phosphate with hypocalcaemia markedly increasing and hypophosphataemia markedly decreasing the number of proliferating cells. The application of basic science findings of how calcium, phosphate and 1,25(OH)2D3 regulate the parathyroids has led to an efficient and safe prescription for the management of the secondary hyperparathyroidism of chronic renal failure which is the maintenance of a normal serum calcium and phosphate and the careful use of bolus doses of 1,25(OH)2D3.

Narrowing of the Hailey-Hailey disease gene region on chromosome 3q and identification of one kindred with a deletion in this region

Hailey-Hailey disease is a cutaneous abnormality transmitted as an autosomal dominant trait in which impaired interkeratinocyte adhesion produces recurrent blisters in characteristic skin sites. We report here a confirmation of the initial mapping of the mutant gene to chromosome 3q in an additional seven kindreds, narrowing of the candidate region to the sequences flanked by D3S1589 and D3S1541, and the finding in one family of a genomic DNA deletion whose centromeric end is located between these two flanking markers.

Photosynthesis, inorganic plant nutrition, solutions, and problems

A brief account is given of the research that D.I. Arnon did before he ventured into the field of photosynthesis, viz. his work on inorganic plant nutrition in the laboratory of D.R. Hoagland. The connection between the two areas is indicated. In his work on plant nutrition Dr Arnon emphasized the role of specific nutrients and, with P.R. Stout, formulated a definition of essentiality that is used to this day. It is now necessary, however, to take into account elements not meeting their criteria of essentiality, as shown by a consideration of the element silicon.

Differential Solute Regulation in Leaf Blades of Various Ages in Salt-Sensitive Wheat and a Salt-Tolerant Wheat x Lophopyrum elongatum (Host) A. Love Amphiploid

Leaf blades of different ages from a salt-tolerant wheat x Lophopyrum elongatum (Host) A. Love (syn. Agropyron elongatum Host) amphiploid and its salt-sensitive wheat parent (Triticum aestivum L.cv Chinese Spring) were compared for their ionic relations, organic solute accumulation, and sap osmotic potential ([pi]sap). The plants were grown for 18 d in nonsaline (1.25 mM Na+) and salinized (200 mM NaCl) nutrient solutions. The response of leaf blades to NaCl salinity depended greatly on their age or position on the main stem. Na and proline levels were highest in the oldest leaf blade and progressively lower in younger ones. Glycine betaine and asparagine levels were highest in the youngest blade. The [pi]sap was similar for corresponding leaf blades of both genotypes, but contributions of various solutes to the difference in [pi]sap between blades from control and 200 mM NaCl treatments differed greatly. The NaCl-induced decline in [pi]sap of the youngest leaf blade of Chinese Spring was predominately due to the accumulation of Na and to a lesser extent asparagine; in the amphiploid, it was due to a combination of glycine betaine, K, Na, and asparagine. Proline contributed little in the youngest blade of either genotype. In the older blades Na was the major solute contributing to the decline in [pi]sap. Thus, the maintenance of low Na and high K levels and the accumulation of glycine betaine in the young leaf tissues contributed to the NaCl tolerance of the amphiploid. No such role was evident for proline.

Oestrogens and calcium regulatory hormones: potential implications for bone

Postmenopausal oestrogen deficiency is associated with the development of osteoporosis. Oestrogen therapy prevents further bone loss but does not have an anabolic effect. The only treatment with an anabolic effect on bone is intermittent parathyroid hormone treatment. Oestrogens have a direct action on the parathyroid to increase parathyroid hormone gene expression and parathyroid hormone secretion. They exert this effect at doses that are too low to cause the uterotrophic effect of oestradiol. Osteoporotic patients have a decreased parathyroid hormone secretory response to changes in serum calcium, supporting the experimental data that oestrogens have a direct effect on the parathyroid. The value of parathyroid hormone treatment is limited by the need for parenteral therapy. The ability of oestrogens to increase parathyroid hormone secretion suggests that the intermittent administration of oestrogen analogues, at doses that exert no effects on breast tissue and the uterus, would be the optimal treatment for osteoporosis.

New aspects in the control of parathyroid hormone secretion

Ca2+ binds to a parathyroid cell Ca2+ receptor, which is G protein-coupled and activates inositol triphosphate production. Mutations in the Ca(2+)-sensing receptor gene cause familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. Chronic hypocalcemia increases parathyroid hormone messenger RNA levels and parathyroid cell hyperplasia. Parathyroid cells in vitro are heterologous in their response to Ca2+. The concept of a higher Ca2+ set-point in secondary hyperparathyroidism is controversial. Calcitriol is more effective than the less hypercalcemia analogues in decreasing parathyroid hormone messenger RNA and immunoreactive parathyroid hormone levels, and its kinetics are well established. Phosphate and estrogens regulate the parathyroid independently of 1,25 dihydroxyvitamin D3 and Ca2+. The physiology of the effects of endothelin and insulin-like growth factors on the parathyroid need to be established. Important advances are being made in understanding the regulation of parathyroid hormone synthesis and secretion, which are relevant to both normal physiology and the pathogenesis and treatment of diseases such as the secondary hyperparathyroidism of renal failure and osteoporosis.

Recalling basal cell carcinoma patients. A regional survey

BACKGROUND

Patients with a basal cell carcinoma (BCC) are at increased risk for developing further BCCs, and long-term follow-up has been recommended to detect new cancers at an earlier, more easily treatable stage. The majority of BCCs are treated by dermatologists in their offices; we do not know to what extent they perform long-term follow up on their patients.

OBJECTIVE

To determine how practicing dermatologists follow up their BCC patients.

METHODS

A mailed questionnaire survey of 166 practicing members of a regional dermatologic society (the San Francisco Dermatological Society), to which 142 (85%) replied.

RESULTS

Two thirds of the respondents recalled BCC patients for screening examinations; of these, 58% followed up non-responders. Recall efforts were hampered by inefficient, unwieldy, and time-consuming techniques.

CONCLUSION

Practicing dermatologists are motivated to recall BCC patients for examination, but guidelines and techniques for effective and efficient computerized recalling of skin cancer patients are needed. It is suggested that the American Academy of Dermatology set up a task force to develop guidelines and criteria for effective recall software.

The anomaly of silicon in plant biology

Silicon is the second most abundant element in soils, the mineral substrate for most of the world's plant life. The soil water, or the "soil solution," contains silicon, mainly as silicic acid, H4SiO4, at 0.1-0.6 mM--concentrations on the order of those of potassium, calcium, and other major plant nutrients, and well in excess of those of phosphate. Silicon is readily absorbed so that terrestrial plants contain it in appreciable concentrations, ranging from a fraction of 1% of the dry matter to several percent, and in some plants to 10% or even higher. In spite of this prominence of silicon as a mineral constituent of plants, it is not counted among the elements defined as "essential," or nutrients, for any terrestrial higher plants except members of the Equisitaceae. For that reason it is not included in the formulation of any of the commonly used nutrient solutions. The plant physiologist's solution-cultured plants are thus anomalous, containing only what silicon is derived as a contaminant of their environment. Ample evidence is presented that silicon, when readily available to plants, plays a large role in their growth, mineral nutrition, mechanical strength, and resistance to fungal diseases, herbivory, and adverse chemical conditions of the medium. Plants grown in conventional nutrient solutions are thus to an extent experimental artifacts. Omission of silicon from solution cultures may lead to distorted results in experiments on inorganic plant nutrition, growth and development, and responses to environmental stress.