A glycine-rich RNA-binding protein affects gibberellin biosynthesis in Arabidopsis.

The RNA-binding protein Arabidopsis thaliana glycine-rich RNA-binding protein 7 (AtGRP7) regulates the steady-state abundance of numerous target transcripts in A. thaliana. Here we show that the GA1 and GA2 transcripts encoding the first enzymes of the gibberellin biosynthetic pathway are expressed at reduced levels in transgenic plants ectopically over-expressing AtGRP7 (AtGRP7-ox plants). Furthermore, the levels of the bioactive phytohormone GA4 as well as of several intermediates of the GA biosynthetic pathway are reduced in AtGRP7-ox plants. The transgenic plants show a reduced length of the vegetative stem. The application of exogenous GA largely reverses the phenotype by increasing the number of vegetative internodes. AtGRP7-ox plants flower with fewer leaves than wt plants, suggesting that the floral promotive effect of AtGRP7 bypasses the effect of a reduced GA level in AtGRP7-ox plants. Upon GA treatment, AtGRP7-ox plants flower only slightly earlier than wild type plants. Thus, exogenous GA has only a small additional effect in reducing the number of leaves at the onset of flowering in AtGRP7-ox plants.

Picking out parallels: plant circadian clocks in context.

Molecular models have been described for the circadian clocks of representatives of several different taxa. Much of the work on the plant circadian system has been carried out using the thale cress, Arabidopsis thaliana, as a model. We discuss the roles of genes implicated in the plant circadian system, with special emphasis on Arabidopsis. Plants have an endogenous clock that regulates many aspects of circadian and photoperiodic behaviour. Despite the discovery of components that resemble those involved in the clocks of animals or fungi, no coherent model of the plant clock has yet been proposed. In this review, we aim to provide an overview of studies of the Arabidopsis circadian system. We shall compare these with results from different taxa and discuss them in the context of what is known about clocks in other organisms.

RNA-binding proteins and circadian rhythms in Arabidopsis thaliana.

An Arabidopsis transcript preferentially expressed at the end of the daily light period codes for the RNA-binding protein AtGRP7. A reverse genetic approach in Arabidopsis thaliana has revealed its role in the generation of circadian rhythmicity: AtGRP7 is part of a negative feedback loop through which it influences the oscillations of its own transcript. Biochemical and genetic experiments indicate a mechanism for this autoregulatory circuit: Atgrp7 gene transcription is rhythmically activated by the circadian clock during the day. The AtGPR7 protein accumulates with a certain delay and represses further accumulation of its transcript, presumably at the post-transcriptional level. In this respect, the AtGRP7 feedback loop differs from known circadian oscillators in the fruitfly Drosophila and mammals based on oscillating clock proteins that repress transcription of their own genes with a 24 h rhythm. It is proposed that the AtGRP7 feedback loop may act within an output pathway from the Arabidopsis clock.

Health insurance and female labor supply in Taiwan.

We examine whether the availability of subsidized health insurance to the non-working population in Taiwan affected the labor force participation of married women. Our empirical identification exploits the fact that such insurance was first made available to wives of government employees, before being made universally available in Taiwan in 1995. We find that the availability of insurance for non-workers was associated with a 4 percentage point decline in labor force participation among married women, with larger declines among women from low income households. Countries considering universal health insurance as in Taiwan should anticipate similar declines in labor force participation.

Associate degree graduates and the rapidly aging RN workforce.

This second segment of a four-part series examines the inter-relationship between the growth in associate degree nursing programs and the aging of the RN workforce. A growing proportion of new RNs have entered the workforce via associate degree programs, increasing from 40% in 1977 to 60% in 1996. New graduates, as well as working RNs, are approximately 5 years older in 1996 than 20 years earlier. Findings suggest that the rapid aging of the RN workforce can not be directly attributed to the rise in the number of older-aged graduates of associate degree programs. Rather, the declining propensity of those born after 1960 to enter nursing has resulted in fewer young RNs, and therefore: (1) an aging workforce, and (2) fewer new grads from baccalaureate programs (which have always attracted younger RNs) relative to grads from associate degree programs (which have always attracted older RNs).

Why are shortages of hospital RNs concentrated in specialty care units?

This article is the first in a series examining the interplay between the aging of the nurse workforce and other factors driving the growing nursing shortage that are already affecting some specialty areas. Nearly 60% of the current RN workforce is over 40 years of age; and the percentage of RNs under age 30 has fallen by nearly 40% since 1980. The total number of FTE RNs is projected to shrink after 2010, likely resulting in shortages of RNs "when the large baby-boom generation of RNs starts to retire." Because ICUs have historically attracted younger RNs, the rapid decline in the number of RNs in the workforce under age 30 plays a large role in explaining the development of shortages in the ICU. The growing difficulties staffing operating rooms and other peri-operative services is seen as related to the aging work force as more diploma prepared nurses have been attracted to this specialty because they had educational exposure to this area.

Arabidopsis thaliana germin-like proteins: common and specific features point to a variety of functions.

Germin-like proteins (GLPs) are ubiquitous plant proteins encoded by diverse multigene families. It is not known whether they share germin's unusual biochemical properties and oxalate oxidase activity. Using specific antibodies, we have studied three GLPs (AtGER1. AtGER2 and AtGER3) in Arabidopsis thaliana (L.) Heynh. as well as in transgenic tobacco (Nicotiana tabacum L.) plants overexpressing these proteins. Like wheat ( Triticum aestivum L.) germin, these Arabidopsis GLPs are associated with the extracellular matrix (ECM) and they also seem to exist as two glycosylated isoforms. However, none of them is an oxalate oxidase. Although GLPs display several conserved features, each has its specific characteristics. Both AtGER2 and AtGER3 are oligomeric proteins that share germin's resistance to pepsin and to dissociation by heat and SDS. In contrast, AtGER1 seems to exist as a monomer. The GLPs may interact with the ECM in a variety of ways, since each is efficiently extracted by different conditions. In addition, germins and GLPs all bind Cibacron Blue, a dye often but not exclusively used for the purification of enzymes having nucleotide cofactors. In the case of AtGER2, binding to the dye is so tight that it almost allows a one-step purification of this protein. The variety of sequences, expression patterns and biochemical features indicates that GLPs could be a class of receptors localized in the ECM and involved in physiological and developmental processes as well as stress response.

Implications of an aging registered nurse workforce.

CONTEXT: The average age of registered nurses (RNs), the largest group of health care professionals in the United States, increased substantially from 1983 to 1998. No empirically based analysis of the causes and implications of this aging workforce exists. OBJECTIVES: To identify and assess key sources of changes in the age distribution and total supply of RNs and to project the future age distribution and total RN workforce up to the year 2020. DESIGN AND SETTING: Retrospective cohort analysis of employment trends of recent RN cohorts over their lifetimes based on US Bureau of the Census Current Population Surveys between 1973 and 1998. Recent workforce trends were used to forecast long-term age and employment of RNs. PARTICIPANTS: Employed RNs aged 23 to 64 years (N = 60,386). MAIN OUTCOME MEASURES: Annual full-time equivalent employment of RNs in total and by single year of age. RESULTS: The average age of working RNs increased by 4.5 years between 1983 and 1998. The number of full-time equivalent RNs observed in recent cohorts has been approximately 35% lower than that observed at similar ages for cohorts that entered the labor market 20 years earlier. Over the next 2 decades, this trend will lead to a further aging of the RN workforce because the largest cohorts of RNs will be between age 50 and 69 years. Within the next 10 years, the average age of RNs is forecast to be 45.4 years, an increase of 3.5 years over the current age, with more than 40% of the RN workforce expected to be older than 50 years. The total number of full-time equivalent RNs per capita is forecast to peak around the year 2007 and decline steadily thereafter as the largest cohorts of RNs retire. By the year 2020, the RN workforce is forecast to be roughly the same size as it is today, declining nearly 20% below projected RN workforce requirements. CONCLUSIONS: The primary factor that has led to the aging of the RN workforce appears to be the decline in younger women choosing nursing as a career during the last 2 decades. Unless this trend is reversed, the RN workforce will continue to age, and eventually shrink, and will not meet projected long-term workforce requirements. JAMA. 2000.

The Atger3 promoter confers circadian clock-regulated transcription with peak expression at the beginning of the night.

In Arabidopsis thaliana, steady-state abundance of the Atger3 transcript encoding a germin-like cell wall protein follows a circadian rhythm, reaching its highest level at the beginning of the night. As a first step towards dissecting the molecular mechanisms underlying these transcript oscillations, the Atger3 genomic locus was characterised. Transcriptional fusions of 1.8 kb and 967 bp Atger3 promoter fragments to the beta-glucuronidase (GUS) reporter gene mediate high-amplitude circadian oscillations of the GUS transcript in transgenic Arabidopsis. 5' deletion to -490 greatly reduces overall transcript abundance while retaining a basal oscillation. Further deletion to -299 abolishes preferential GUS expression in the evening. Taken together, these data indicate that clock-response elements contributing to high-amplitude Atger3 oscillations largely reside between -299 and -967. Histochemical staining for GUS activity indicates that the Atger3 promoter is active in cotyledons, young leaves, petioles, the inflorescence axis, pedicels, sepals, ovary, style and siliques but not in roots, petals and anthers.

Circadian clock-regulated expression of an RNA-binding protein in Arabidopsis: characterisation of a minimal promoter element.

The Atgrp7 transcript encodes a clock-regulated, glycine-rich, RNA-binding protein in Arabidopsis thaliana and shows a circadian variation in steady-state abundance. Constitutive overexpression of its product, AtGRP7, in transgenic Arabidopsis plants depresses the oscillations of the endogenous Atgrp7 transcript, indicating that both the transcript and the protein are part of a clock-regulated negative feedback circuit. Here we characterise the upstream region of the Atgrp7 gene in order to begin to dissect the molecular basis of this oscillating autoregulatory feedback loop. Fusion of a 1.5-kb promoter fragment to the beta-glucuronidase (gus) reporter gene leads to circadian oscillations in the level of the gus transcript in transgenic Arabidopsis plants, with highest levels in the evening, indicating that transcription of the Atgrp7 gene is rhythmically activated by the endogenous circadian clock. A 265-bp fragment upstream of the transcription start site is necessary for high-amplitude Atgrp7 cycling. Within this region, a 56-bp clock-responsive element that confers a low-amplitude circadian oscillation (approximately threefold) with peak abundance in the early evening maps between positions -112 and -57. Another element necessary for augmenting the amplitude of the oscillation lies between -178 and -264. Genetic crosses between a line bearing a promoter-gus fusion and plants that overexpress AtGRP7 show that the promoter by itself does not mediate the negative feedback of AtGRP7 on the oscillations of its own transcript.

Roe v Wade and American fertility.

OBJECTIVES: This article examines the effect of abortion legalization on fertility rates in the United States. METHODS: Fertility rates were compared over time between states that varied in the timing of abortion legalization. RESULTS: States legalizing abortion experienced a 4% decline in fertility relative to states where the legal status of abortion was unchanged. The relative reductions in births to teens, women more than 35 years of age, non-White women, and unmarried women were considerably larger. If women did not travel between states to obtain an abortion, the estimated impact of abortion legalization on birth rates would be about 11%. CONCLUSIONS: A complete recriminalization of abortion nationwide could result in 440,000 additional births per year. A reversal of the Roe v Wade decision leaving abortion legal in some states would substantially limit this impact because of the extent of travel between states.

The circadian system of Arabidopsis thaliana: forward and reverse genetic approaches.

It is now widely accepted that autoregulatory circuits involving transcription/translation of clock genes form the molecular basis of the endogenous circadian clock in different organisms. In Arabidopsis thaliana, the RNA-binding protein AtGRP7 (Arabidopsis thaliana glycine-rich protein) has been identified as part of a negative-feedback loop through which AtGRP7 regulates the circadian oscillations of its own transcript. Experimental evidence indicates that this feedback loop also is influenced by another oscillator. Support for this hypothesis comes from the characterization of the clock mutant toc1 (timing of cab expression) and the recent isolation of two candidate clock molecules, LHY (late elongated hypocotyl) and CCA1 (circadian clock associated). TOC1, as well as the LHY and CCA1 oscillatory feedback loops, influence several rhythmic physiological and molecular processes in Arabidopsis, including cyclic Atgrp7 gene expression. We discuss the features of these feedback loops with relation to the organization of the circadian system in Arabidopsis.

AtGRP7, a nuclear RNA-binding protein as a component of a circadian-regulated negative feedback loop in Arabidopsis thaliana.

The endogenous clock that drives circadian rhythms is thought to communicate temporal information within the cell via cycling downstream transcripts. A transcript encoding a glycine-rich RNA-binding protein, Atgrp7, in Arabidopsis thaliana undergoes circadian oscillations with peak levels in the evening. The AtGRP7 protein also cycles with a time delay so that Atgrp7 transcript levels decline when the AtGRP7 protein accumulates to high levels. After AtGRP7 protein concentration has fallen to trough levels, Atgrp7 transcript starts to reaccumulate. Overexpression of AtGRP7 in transgenic Arabidopsis plants severely depresses cycling of the endogenous Atgrp7 transcript. These data establish both transcript and protein as components of a negative feedback circuit capable of generating a stable oscillation. AtGRP7 overexpression also depresses the oscillation of the circadian-regulated transcript encoding the related RNA-binding protein AtGRP8 but does not affect the oscillation of transcripts such as cab or catalase mRNAs. We propose that the AtGRP7 autoregulatory loop represents a "slave" oscillator in Arabidopsis that receives temporal information from a central "master" oscillator, conserves the rhythmicity by negative feedback, and transduces it to the output pathway by regulating a subset of clock-controlled transcripts.

Future of the nurse labor market according to health executives in high managed-care areas of the United States.

PURPOSE: To understand how the work environment of nurses is changing in states with high enrollment in health maintenance organizations (HMOs), the underlying forces driving change, and how these forces are expected to affect employment and earnings of nurses in the future. Financing and delivery systems that have developed in some states with high enrollment in HMOs are generally regarded as indicative of the future for all the United States. DESIGN: Survey in 1995 of a convenience sample of 62 health executives in 11 states with high enrollment in HMOs. Executives included officials in state governments, state and metropolitan hospital associations, professional and nonprofessional nursing associations, state boards of nursing, community and public health, home health care, nursing homes, other non-acute care associations, and leading HMOs. METHODS: Through structured telephone interviews, executives were asked about changes in nurse employment, earnings, collective bargaining, fringe benefits, nurses' roles, substitution of licensed practical nurses (LPNs) and aides for RNs, patient severity, quality of patient care, and expectations for nurse employment during the remainder of the decade. FINDINGS: Executives perceive a mostly positive and fast-changing nurse labor market but they are concerned about the aging RN work force, possible development of an RN shortage, and linking quality of patient care to the provision of nursing services. They doubt the ability of nurse educators to respond quickly to the need to prepare nurses for rapidly changing employer requirements. CONCLUSIONS: Public and private forces are causing rapid, profound changes in health care delivery and throughout the nurse labor market. These changes are most evident in the shift in employment of nurses from hospitals to home health. Despite anxiety associated with these changes, no evidence of an "employment disaster" exists in the views of health executives.

cDNA sequence, genomic organization and differential expression of three Arabidopsis genes for germin/oxalate oxidase-like proteins.

Wheat germin is a protein expressed during germination which possesses an oxalate oxidase activity. Germin-type oxalate oxidases have been extensively studied in monocotyledons (wheat and barley) where they are thought to have important functions for development, stress response and defence against pathogens. In contrast, almost nothing is known about the germin-like proteins found in dicotyledons, gymnosperms and myxomycetes. In this work, cDNA clones for three genes (ATGER1, ATGER2 and ATGER3) encoding germin-like proteins, initially characterized as expressed sequence tags (ESTs), from Arabidopsis thaliana cDNA libraries were further characterized. In addition, we isolated and sequenced a Brassica napus cDNA which was strongly homologous to the cDNA for ATGER1. Sequence analysis and secondary structure predictions of the proteins encoded by these cDNAs showed that they possess all the characteristic features of members of the germin family and of the germin/seed globulins/sucrose binding protein superfamily. Sequence comparisons and mapping demonstrated the existence of at least two different gene families in the A. thaliana genome encoding a minimum of three genes for germins. These three genes have been mapped in three different location on the Arabidopsis genome. By northern blot hybridizations we found that these genes are differentially regulated. ATGER1 was expressed during germination, like wheat germin, but also in leaves whereas ATGER2 transcripts were exclusively found in developing embryos, like wheat pseudo-germin. ATGER3 mRNAs were found in leaves and flowers and their abundance was shown to vary during the circadian cycle.

Managed care and the nurse workforce.

OBJECTIVES: To identify recent national trends in the employment and earnings of nursing personnel and determine whether managed care is associated with changes in the employment and wage growth of nursing personnel. DESIGN: Retrospective analysis of trends in data on employment and earnings of nursing personnel based on monthly US Bureau of the Census Current Population Surveys between 1983 and 1994, and comparison of trends between states with high and low rates of enrollment in health maintenance organizations (HMOs). POPULATION: Registered nurses (RNs), licensed practical nurses (LPNs), and nurse aides/assistants, orderlies, and attendants (referred to collectively as aides) between the ages of 21 and 64 years. OUTCOME MEASURES: Full- and part-time employment, unemployment, percentage of nursing personnel employed in key sectors of the nurse labor market, and inflation-adjusted hourly wages. RESULTS: From 1983 through 1994, there was strong overall growth in both RN employment (37%) and inflation-adjusted wages (22%). Beginning in the early 1990s, however, RNs experienced stagnant wages and a small but steady shift toward employment in lower-paying nonhospital settings, particularly in home health care. In states with high HMO enrollment, RN and LPN employment has grown more slowly since 1990, and the shift of RN employment out of the hospital was strongest. For aides and LPNs, the shift out of hospital employment occurred years before that of RNs and at a much greater rate. Since 1990 the employment of aides has grown rapidly in nursing homes and in home health care settings, whereas employment of LPNs has shifted primarily into physician offices and nursing homes. Overall, the movement toward nonhospital employment has had a modest negative impact on wages for all nursing personnel. CONCLUSIONS: Managed care is associated with slower employment growth for RNs in hospitals and a shift toward employment in nonhospital settings, but its effect on earnings has been overshadowed by other forces impacting nurse wages.

Circadian oscillations of a transcript encoding a germin-like protein that is associated with cell walls in young leaves of the long-day plant Sinapis alba L.

As part of an attempt to analyze rhythmic phenomena in the long-day plant Sinapis alba L. at the molecular level, we have searched for mRNAs whose concentration varies as a function of time of day. Differential screening of a cDNA library established from mRNAs expressed at the end of the daily light phase with probes representing transcripts expressed predominantly in the morning or evening has identified one major transcript. The cDNA, Saglp, encodes a predicted 22-kD protein with an N-terminal signal sequence. The protein shows homology to germin, a protein expressed in wheat embryos after onset of germination. The Saglp mRNA level undergoes circadian oscillations in light/dark cycles with maxima between 8 and 12 PM (zeitgeber time [zt]12-zt16) and minima around 8 PM (zt0). In plants grown from seed in constant light, transcript levels are constitutive. In constant light regular temperature shifts function as an alternative "zeitgeber" to initiate Saglp transcript oscillations. At the cellular level, Saglp transcripts are expressed in the epidermis and spongy parenchyma of young leaves, and in distinct regions of the epidermis and the cortex in stems and petioles. Strong signals are observed in these tissues around zt12, whereas little expression is found around zt20, suggesting that the underlying oscillatory mechanism(s) operate(s) synchronously in different plant organs. The SaGLP steady-state protein concentration remains constant over light/dark cycles. Immunogold labeling shows that the SaGLP protein is associated with primary cell walls.

A light- and temperature-entrained circadian clock controls expression of transcripts encoding nuclear proteins with homology to RNA-binding proteins in meristematic tissue.

To investigate physiological processes generated by endogenous circadian rhythms on the molecular level, we have identified clock-controlled genes in the long-day plant Sinapis alba L. A cDNA library was differentially screened using cDNA probes representing transcripts expressed at either the middle of the light period or the middle of the dark period. Two closely related groups of transcripts, Sagrp1 and Sagrp2, controlled by a circadian rhythm have been isolated. RNA blot analysis verified that transcript levels oscillate in plants grown in light/dark cycles with maxima between 'Zeitgeber' time (zt)8 and zt12 (8-12 h after onset of illumination) and minima around zt20. Steady-state mRNA levels continue to oscillate in plants shifted from light/dark cycles to constant light. No synchronous mRNA oscillations are found in plants grown from seed in constant light at constant temperature, suggesting that the clock has to be entrained initially. In contrast, when plants grown in constant light are exposed to rhythmic temperature shifts oscillations of steady-state Sagrp mRNA levels are induced, indicating that temperature acts as an alternative external stimulus (zeitgeber) other than light to entrain the oscillator. In situ hybridization reveals that both transcript groups are expressed predominantly in meristematic and growing tissue. Strong expression is observed in the leaf primordia of the shoot apex, the procambial strands, cambium and in all cell layers of young leaves around zt12. In contrast, little or no signal is found on tissue sections isolated at zt20. This indicates that the oscillator(s) regulating Sagrp transcript fluctuations operate(s) synchronously in different organs. For both transcript groups cDNAs were isolated corresponding to unspliced pre-mRNAs or to transcripts generated by the use of a second 5' splice site. The cDNAs corresponding to the fully spliced transcripts contain open reading frames for polypeptides of 16 kDa, each containing a putative N-terminal RNA recognition motif and a C-terminal region rich in glycine. The predicted proteins show strong homology to an ABA-inducible glycine-rich protein from maize embryos and to the mammalian RNA-binding protein A1 of the heterogeneous nuclear ribonucleoprotein complex involved in pre-mRNA splicing. The SaGRP protein fluctuates with a very low amplitude over light/dark cycles. Immunogold labeling demonstrates the presence of the SaGRP protein within the nucleus of the investigated meristematic cells of young leaves.