Localized measurements of water potential reveal large loss of conductance in living tissues of maize leaves.

The water status of the living tissue in leaves between the xylem and stomata (outside xylem zone (OXZ) plays a critical role in plant function and global mass and energy balance but has remained largely inaccessible. We resolve the local water relations of OXZ tissue using a nanogel reporter of water potential (ψ), AquaDust, that enables an in situ, nondestructive measurement of both ψ of xylem and highly localized ψ at the terminus of transpiration in the OXZ. Working in maize (Zea mays L.), these localized measurements reveal gradients in the OXZ that are several folds larger than those based on conventional methods and values of ψ in the mesophyll apoplast well below the macroscopic turgor loss potential. We find a strong loss of hydraulic conductance in both the bundle sheath and the mesophyll with decreasing xylem potential but not with evaporative demand. Our measurements suggest the OXZ plays an active role in regulating the transpiration path, and our methods provide the means to study this phenomenon.

Low leaf hydraulic conductance associated with drought tolerance in soybean.

Lack of water is the most serious environmental constraint on agricultural production. More efficient use of water resources is a key solution for increased plant productivity in water-deficit environments. We examined the hydraulic characteristics of a 'slow wilting' phenotype in soybean (Glycine max Merr.), PI 416937, which has been shown to have relatively constant transpiration rates above a threshold atmospheric vapor pressure deficit (VPD). The VPD response of PI 416937 was confirmed. Three experiments are reported to examine the hypothesis that the VPD response was a result of low hydraulic conductance in leaves as compared to two other soybean genotypes. Results are reported from experiments to measure transpiration response to VPD when xylem water potential was maintained at zero, leaf rehydration response and leaf carbon assimilation response to petiole cutting. Major interspecific differences in leaf hydraulic properties were observed. The observed low leaf hydraulic conductance in PI 416937 is consistent with an increased water use efficiency, and an increased water conservation by limiting transpiration rates under high evaporative conditions but allowing normal gas exchange rates under more moderate evaporative conditions.

Testicular anti-mullerian hormone secretion is stimulated by recombinant human FSH in patients with congenital hypogonadotropic hypogonadism.

Serum anti-Mullerian hormone (AMH), a prepubertal Sertoli cell marker, declines during puberty as an early sign of testicular testosterone (T) production. When T synthesis or action is impaired, serum AMH is abnormally high in the first months after birth and at puberty but normal between these two periods. We postulated that FSH might be responsible for AMH up-regulation in the absence of androgen inhibition. To test this hypothesis, we administered recombinant human (rh) FSH to eight patients aged from 18-31 yr with untreated congenital hypogonadotropic hypogonadism. This situation is ideal to study the effect of FSH on AMH production because it avoids interference by endogenous gonadotropins and T. The patients received daily sc injections of 150 IU rhFSH for 1 month, followed in seven of them by a combined treatment of rhFSH plus human chorionic gonadotropin (hCG; 1500 UI im, twice a week) for 2 months. Gonadotropins, T, AMH, and inhibin B were measured in plasma before treatment every 10 d during rhFSH treatment and every month during combined rhFSH and hCG treatments. All hormones were at prepubertal levels before treatment. Although LH and T did not vary, AMH and inhibin B levels gradually increased after 20 d of FSH administration. However, in contrast to rhFSH alone, the combined rhFSH plus hCG stimulation of the testis dramatically suppresses the secretion of AMH and induced a modest but significant reduction of circulating inhibin B levels. We conclude that FSH stimulates AMH production in the testis when it is at a prepubertal stage. In addition, the decrease of serum AMH during combined rhFSH and hCG testicular stimulation is in agreement with the concept that during pubertal development and in adult life, the suppressive effect of LH-driven testicular androgens outweighs the stimulating effect of FSH on AMH production by Sertoli cells. Finally, the hCG-induced decrease in inhibin B suggests that in humans, as previously demonstrated in monkeys, testicular T is also able to inhibit inhibin B secretion.

Management of Graves' disease during pregnancy: the key role of fetal thyroid gland monitoring.

BACKGROUND: Fetuses from mothers with Graves' disease may experience hypothyroidism or hyperthyroidism due to transplacental transfer of antithyroid drugs (ATD) or anti-TSH receptor antibodies, respectively. Little is known about the fetal consequences. Early diagnosis is essential to successful management. We investigated a new approach to the fetal diagnosis of thyroid dysfunction and validated the usefulness of fetal thyroid ultrasonograms. METHODS: Seventy-two mothers with past or present Graves' disease and their fetuses were monitored monthly from 22 wk gestation. Fetal thyroid size and Doppler signals, and fetal bone maturation were determined on ultrasonograms, and thyroid function was evaluated at birth. Thyroid function and ATD dosage were monitored in the mothers. RESULTS: The 31 fetuses whose mothers were anti-TSH receptor antibody negative and took no ATDs during late pregnancy had normal test results. Of the 41 other fetuses, 30 had normal test results at 32 wk, 29 were euthyroid at birth, and one had moderate hypothyroidism on cord blood tests. In the remaining 11 fetuses, goiter was visualized by ultrasonography at 32 wk, and fetal thyroid dysfunction was diagnosed and treated; there was one death, in a late referral, and 10 good outcomes with normal or slightly altered thyroid function at birth. The sensitivity and specificity of fetal thyroid ultrasound at 32 wk for the diagnosis of clinically relevant fetal thyroid dysfunction were 92 and 100%, respectively. CONCLUSION: In pregnant women with past or current Graves' disease, ultrasonography of the fetal thyroid gland by an experienced ultrasonographer is an excellent diagnostic tool. This tool in conjunction with close teamwork among internists, endocrinologists, obstetricians, echographists, and pediatricians can ensure normal fetal thyroid function.

Modeling the hydrodynamics of Phloem sieve plates.

Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.

Thyroid function during pregnancy in women with past Graves' disease.

Graves' disease and thyroid dysfunction during pregnancy can lead to maternal and fetal complications. No information is available on thyroid function in women with a past history of Graves' disease. We compared free T3, free T4 and TSH in a group of pregnant women with a history of resolved Graves' disease requiring no current treatment (n= 34) and in a group of pregnant controls (n= 102). We found no significant differences in the levels of these hormones between the two groups. Women with a past history of Graves' disease and no current treatment display a normal thyroid function and adaptation during pregnancy.

Improvement in bone mineral density and body composition in survivors of childhood acute lymphoblastic leukemia: a 1-year prospective study.

OBJECTIVES: Abnormalities in bone mineral density (BMD), body composition, and bone metabolism have been reported in children who were treated for acute lymphoblastic leukemia (ALL) during and after completion of therapy. However, these studies are cross-sectional, and no longitudinal data are available in a large group of patients after completion of therapy. In the present study, 1-year longitudinal changes in BMD, body composition, and bone metabolism were evaluated in children with ALL during the first 3 years after completion of therapy without cranial irradiation. METHODS: BMD of total body (TB; g/cm(2)), areal and apparent volumetric lumbar spine (L2-L4), lean body mass, and percentage of body fat were measured by dual-energy x-ray absorptiometry in 37 children (median age: 7.9 years; range: 4.7-20.6 years) who were treated for ALL at a median age of 3.3 years (range: 1.1-16.6 years), after a median time of 2.2 years after the completion of treatment, and after a 1-year follow-up period. Two control subjects (n = 74) who were matched for gender, age, and pubertal stage were also longitudinally investigated for body composition for 1 year. Usual serum biochemical markers of calcium metabolism and bone turnover were measured in patients during the study period. RESULTS: A slight decrease in TB BMD was found after a median time of 2.2 years after the completion of therapy for ALL in childhood. Patients showed a significantly lower median TB BMD when evaluated <1.5 years as compared with those at >or=1.5 years since completion of therapy. At the time of first evaluation, the percentage of body fat mass was significantly higher and patients were physically less active than their matched control subjects. Although, as expected, during the 1 year of follow-up both groups showed an annual increment in their BMD measurements, a significantly higher increase in TB BMD was observed in patients in comparison with control subjects. During this same period, the increase in the percentage of body fat mass was slightly lower in ALL patients as compared with control subjects. At the end of the follow-up year, BMD, body-composition parameters, and physical activity of ALL patients were similar to those observed in matched control subjects. Serum biochemical markers of bone turnover were normal at both evaluations. CONCLUSIONS: A significant increase in TB BMD and a tendency to a lesser increase in percentage of body fat mass were observed during the study period in ALL patients as compared with chronological age-, gender-, and pubertal stage-matched control subjects. These findings suggest a positive effect of long-term completion therapy and increase in physical activity on BMD, body composition, and bone metabolism in patients who have been treated for ALL.