Depression, social factors, and farmworker health care utilization.

PURPOSE: Farmworkers frequently live in rural areas and experience high rates of depressive symptoms. This study examines the association between elevated depressive symptoms and health care utilization among Latino farmworkers. METHODS: Data were obtained from 2,905 Latino farmworkers interviewed for the National Agricultural Workers Survey. Elevated depressive symptoms were measured using the Center for Epidemiologic Studies Depression short-form. A dichotomous health care utilization variable was constructed from self-reported use of health care services in the United States. A categorical measure of provider type was constructed for those reporting use of health care. RESULTS: Over 50% of farmworkers reported at least 1 health care visit in the United States during the past 2 years; most visits occurred in a private practice. The odds of reporting health care utilization in the United States were 45% higher among farmworkers with elevated depressive symptoms. Type of provider was not associated with depressive symptoms. Women were more likely to seek health care; education and family relationships were associated with health care utilization. CONCLUSIONS: Latino farmworkers who live and work in rural areas seek care from private practices or migrant/Community Health Clinics. Farmworkers with elevated depressive symptoms are more likely to access health care. Rural health care providers need to be prepared to recognize, screen, and treat mental health problems among Latino farmworkers. Outreach focused on protecting farmworker mental health may be useful in reducing health care utilization while improving farmworker quality of life.

Mental health research with Latino farmworkers: a systematic evaluation of the short CES-D.

Mental health research among Latino farmworkers is hampered by the absence of measurement evaluation that ensures farmworkers understand and can consistently and appropriately respond to questions about mental health. Cross-sectional data were obtained from 409 farmworkers via interviewer-administered survey questionnaires. Mental health was operationalized with the short-form Center for Epidemiologic Studies, Depression (CES-D) scale. The structured interviewer-administered survey questionnaires included measures to capture personal and work-related factors that could affect farmworkers' ability to understand and respond to mental health questions probed by the CES-D. Good variability in item response was observed across the 10 short-form CES-D items. There was no evidence of differential response across sub-groups of farmworkers for six of the 10 items. Responses to four of the 10 items differed by educational attainment, country of origin, and language preference. Overall, the internal consistency of the 10 items exceeded standard conventions, and observed differences in depressive symptoms were as expected. Researchers in farmworker mental health must remain attentive to the strength and validity of available measures for migrants, different ethnic groups and different socioeconomic backgrounds. Nevertheless, the overall pattern suggests that the CES-D is a viable tool for advancing farmworker mental health research.

Calcium-mediated inactivation of the MAP kinase pathway in sea urchin eggs at fertilization.

We have evaluated the regulation of a 43-kDa MAP kinase in sea urchin eggs. Both MAP kinase and MEK (MAP kinase kinase) are phosphorylated and active in unfertilized eggs while both are dephosphorylated and inactivated after fertilization, although with distinct kinetics. Reactivation of MEK or the 43-kDa MAP kinase prior to or during the first cell division was not detected. Confocal immunolocalization microscopy revealed that phosphorylated (active) MAP kinase is present primarily in the nucleus of the unfertilized egg, with some of the phosphorylated form in the cytoplasm as well. Incubation of unfertilized eggs in the MEK inhibitor U0126 (0.5 microM) resulted in the inactivation of MEK and MAP kinase within 30 min. Incubation in low concentrations of U0126 (sufficient to inactivate MEK and MAP kinase) after fertilization had no effect on progression through the embryonic cell cycle. Microinjection of active mammalian MAP kinase phosphatase (MKP-3) resulted in inactivation of MAP kinase in unfertilized eggs, as did addition of MKP-3 to lysates of unfertilized eggs. Incubation of unfertilized eggs in the Ca(2+) ionophore A23187 led to inactivation of MEK and MAP kinase with the same kinetics as observed with sperm-induced egg activation. This suggests that calcium may be deactivating MEK and/or activating a MAP kinase-directed phosphatase. A cell-free system was used to evaluate the activation of phosphatase separately from MEK inactivation. Unfertilized egg lysates were treated with U0126 to inactivate MEK and then Ca(2+) was added. This resulted in increased MAP kinase phosphatase activity. Therefore, MAP kinase inactivation at fertilization in sea urchin eggs likely is the result of a combination of MEK inactivation and phosphatase activation that are directly or indirectly responsive to Ca(2+).

Ca2+ signalling during fertilization of echinoderm eggs.

The Ca2+ rise at fertilization of echinoderm eggs is initiated by a process requiring the sequential activation of a Src family kinase, phospholipase C gamma, and the inositol trisphosphate receptor/channel in the endoplasmic reticulum. The consequences of the Ca2+ rise include exocytosis of cortical granules, which establishes a block to polyspermy, and inactivation of MAP kinase, which functions in linking the Ca2+ rise to the reinitiation of the cell cycle.

Agricultural injury.

BACKGROUND: Agriculture is one of the most hazardous industries in the US. METHODS: We reviewed MEDLINE and NIOSHTIC to identify English-language studies addressing occupational injury among agricultural populations, focusing on North America. Additional references were identified from the reference lists of identified studies and from contacts with experts in the field. RESULTS: U.S. data indicate up to approximately 780 deaths and 140,000 cases of nonfatal disabling injuries in 1998. Risk of agricultural injuries is approximately 5-10/100 persons per year, but is higher in certain risk groups, such as males and cattle workers. Falls, machinery, and animals are among the most common causes. Unique features of the agricultural workplace and exposed population combine to increase risk and hinder accurate measurement. These features include a wide range of activities, hazards, and dispersed work places in agriculture; a seasonal hired work force that often has brief tenure, poor English skills, and a distrust of officialdom; and a history of exemption regarding occupational health and safety regulations. CONCLUSIONS: Research in agricultural injury should include epidemiologic study of risk factors and evaluation of interventions. Although only limited data are available documenting efficacy of specific preventive approaches, prevention should focus on engineering controls, regulatory approaches, and education.

Evidence that Src-type tyrosine kinase activity is necessary for initiation of calcium release at fertilization in sea urchin eggs.

The initiation of Ca(2+) release from internal stores in the egg is a hallmark of egg activation. In sea urchins, PLCgamma activity is necessary for the production of IP(3), which leads to the initial rise in Ca(2+). To examine the possible function of a tyrosine kinase in activating PLCgamma at fertilization, sea urchin eggs were treated with the specific Src kinase inhibitor PP1 or microinjected with recombinant Src-family SH2-domain proteins, which act as dominant interfering inhibitors of Src-family kinase function. Both modes of inhibiting Src-family kinases resulted in a specific and dose-dependent delay in the onset of Ca(2+) release from the endoplasmic reticulum at fertilization. The rise in cytoplasmic pH at fertilization also was inhibited by microinjection of Src-family SH2-domain proteins. Further, an antibody directed against Src-type kinases recognized a protein of ca. M(r) 57K that was enriched in the membrane fraction of eggs. The kinase activity of this protein was stimulated rapidly and transiently at fertilization, as measured by autophosphorylation and by phosphorylation of an exogenous substrate. Together, these data indicate that a Src-type tyrosine kinase is necessary for the initiation of Ca(2+) release from the egg ER at fertilization and identify a Src-type p57 protein as a candidate in the signaling pathway leading to this Ca(2+) release.

The relationship between calcium, MAP kinase, and DNA synthesis in the sea urchin egg at fertilization.

Fertilization releases the brake on the cell cycle and the egg completes meiosis and enters into S phase of the mitotic cell cycle. The MAP kinase pathway has been implicated in this process, but the precise role of MAP kinase in meiosis and the first mitotic cell cycle remains unknown and may differ according to species. Unlike the eggs of most animals, sea urchin eggs have completed meiosis prior to fertilization and are arrested at the pronuclear stage. Using both phosphorylation-state-specific antibodies and a MAP kinase activity assay, we observe that MAP kinase is phosphorylated and active in unfertilized sea urchin eggs and then dephosphorylated and inactivated by 15 min postinsemination. Further, Ca(2+) was both sufficient and necessary for this MAP kinase inactivation. Treatment of eggs with the Ca(2+) ionophore A23187 caused MAP kinase inactivation and triggered DNA synthesis. When the rise in intracellular Ca(2+) was inhibited by injection of a chelator, BAPTA or EGTA, the activity of MAP kinase remained high. Finally, inhibition of the MAP kinase signaling pathway by the specific MEK inhibitor PD98059 triggered DNA synthesis in unfertilized eggs. Thus, whenever MAP kinase activity is retained, DNA synthesis is inhibited while inactivation of MAP kinase correlates with initiation of DNA synthesis.

Requirement of a Src family kinase for initiating calcium release at fertilization in starfish eggs.

Signal transduction leading to calcium release in echinoderm eggs at fertilization requires phospholipase Cgamma-mediated production of inositol trisphosphate (IP(3)), indicating that a tyrosine kinase is a likely upstream regulator. Because previous work has shown a fertilization-dependent association between the Src homology 2 (SH2) domains of phospholipase Cgamma and a Src family kinase, we examined whether a Src family kinase was required for Ca(2+) release at fertilization. To inhibit the function of kinases in this family, we injected starfish eggs with the SH2 domains of Src and Fyn kinases. This inhibited Ca(2+) release in response to fertilization but not in response to injection of IP(3). We further established the specificity of the inhibition by showing that the SH2 domains of several other tyrosine kinases (Abl, Syk, and ZAP-70), and the SH3 domain of Src, were not inhibitory. Also, a point-mutated Src SH2 domain, which has reduced affinity for phosphotyrosine, was a correspondingly less effective inhibitor of fertilization-induced Ca(2+) release. These results indicate that a Src family kinase, by way of its SH2 domain, links sperm-egg interaction to IP(3)-mediated Ca(2+) release at fertilization in starfish eggs.

Evidence that a starfish egg Src family tyrosine kinase associates with PLC-gamma1 SH2 domains at fertilization.

The initiation of calcium release at fertilization in the eggs of most animals relies on the production of IP3, implicating the activation of phospholipase C. Recent work has demonstrated that injection of PLC-gamma SH2 domain fusion proteins into starfish eggs specifically inhibits the initiation of calcium release in response to sperm, indicating that PLC-gamma is necessary for Ca2+ release at fertilization [Carroll et al. (1997) J. Cell Biol. 138, 1303-1311]. Here we investigate how PLC-gamma may be activated, by using the PLC-gamma SH2 domain fusion protein as an affinity matrix to identify interacting proteins. A tyrosine kinase activity and an egg protein of ca. Mr 58 K that is recognized by an antibody directed against Src family tyrosine kinases associate with PLC-gamma SH2 domains in a fertilization-dependent manner. These associations are detected by 15 s postfertilization, consistent with a function in releasing Ca2+. Calcium ionophore treatment of eggs did not cause association of the kinase activity or of the Src family protein with the PLC-gamma SH2 domains. These data identify an egg Src family tyrosine kinase as a potential upstream regulator of PLC-gamma in the activation of starfish eggs.

Identification of PLCgamma-dependent and -independent events during fertilization of sea urchin eggs.

At fertilization, sea urchin eggs undergo a series of activation events, including a Ca2+ action potential, Ca2+ release from the endoplasmic reticulum, an increase in intracellular pH, sperm pronuclear formation, MAP kinase dephosphorylation, and DNA synthesis. To examine which of these events might be initiated by activation of phospholipase Cgamma (PLCgamma), which produces the second messengers inositol trisphosphate (IP3) and diacylglycerol, we used recombinant SH2 domains of PLCgamma as specific inhibitors. Sea urchin eggs were co-injected with a GST fusion protein composed of the two tandem SH2 domains of bovine PLCgamma and (1) Ca2+ green dextran to monitor intracellular free Ca2+, (2) BCECF dextran to monitor intracellular pH, (3) Oregon Green dUTP to monitor DNA synthesis, or (4) fluorescein 70-kDa dextran to monitor nuclear envelope formation. Microinjection of the tandem SH2 domains of PLCgamma produced a concentration-dependent inhibition of Ca2+ release and also inhibited cortical granule exocytosis, cytoplasmic alkalinization, MAP kinase dephosphorylation, DNA synthesis, and cleavage after fertilization. However, the Ca2+ action potential, sperm entry, and sperm pronuclear formation were not prevented by injection of the PLCgammaSH2 domain protein. Microinjection of a control protein, the tandem SH2 domains of the phosphatase SHP2, had no effect on Ca2+ release, cortical granule exocytosis, DNA synthesis, or cleavage. Specificity of the inhibitory action of the PLCgammaSH2 domains was further indicated by the finding that microinjection of PLCgammaSH2 domains that had been point mutated at a critical arginine did not inhibit Ca release at fertilization. Additionally, Ca2+ release in response to microinjection of IP3, cholera toxin, cADP ribose, or cGMP was not inhibited by the PLCgammaSH2 fusion protein. These results indicate that PLCgamma plays a key role in several fertilization events in sea urchin eggs, including Ca2+ release and DNA synthesis, but that the action potential, sperm entry, and male pronuclear formation can occur in the absence of PLCgamma activation or Ca2+ increase.

Inventing the future of physicians and information technology: methods and results of the 1997 Lafayette Parish Medical Society Information Systems and Information Technology Project.

This paper challenges physicians to consider how to best invent a future in which they can personally leverage emerging information and communication technologies to maximize their effectiveness and efficiency as care givers. One Louisiana State Medical Society component medical society has already posed this challenge to its members. The paper describes the 1997 Lafayette Parish Medical Society Physicians' Information Systems and Information Project, conducted on behalf of the society by faculty of the Healthcare Administration MBA Program at the University of Southwestern Louisiana. Specific recommendations for application of health care information technologies by physicians and by health care institutions, based on findings and conclusions of the project, are highlighted.

Calcium release at fertilization in starfish eggs is mediated by phospholipase Cgamma.

Although inositol trisphosphate (IP3) functions in releasing Ca2+ in eggs at fertilization, it is not known how fertilization activates the phospholipase C that produces IP3. To distinguish between a role for PLCgamma, which is activated when its two src homology-2 (SH2) domains bind to an activated tyrosine kinase, and PLCbeta, which is activated by a G protein, we injected starfish eggs with a PLCgamma SH2 domain fusion protein that inhibits activation of PLCgamma. In these eggs, Ca2+ release at fertilization was delayed, or with a high concentration of protein and a low concentration of sperm, completely inhibited. The PLCgammaSH2 protein is a specific inhibitor of PLCgamma in the egg, since it did not inhibit PLCbeta activation of Ca2+ release initiated by the serotonin 2c receptor, or activation of Ca2+ release by IP3 injection. Furthermore, injection of a PLCgamma SH2 domain protein mutated at its phosphotyrosine binding site, or the SH2 domains of another protein (the phosphatase SHP2), did not inhibit Ca2+ release at fertilization. These results indicate that during fertilization of starfish eggs, activation of phospholipase Cgamma by an SH2 domain-mediated process stimulates the production of IP3 that causes intracellular Ca2+ release.

Effects of dietary crude protein, breed, parity, and health status on the fertility of dairy cows.

A study was conducted to determine the impact of dietary CP (13% vs. 20%), parity (first vs. second lactation or later), and breed (Holstein vs. Jersey) on the reproductive efficiency of dairy cows. Sixty-four cows were blocked by parity and breed and assigned to one of two treatments. Cows were removed from treatments on d 100 or 120 depending on pregnancy status. Cows were categorized by health status based on the occurrence of postparturient disorders. Plasma urea N concentrations were influenced by diet (8.6 vs. 21 mg/dl, 13 and 20% CP, respectively), parity, and breed. Reproductive indices were not influenced by diet except that days to first estimated ovulation increased for cows fed the 20% CP diet when health status was added to the model. Days to first observed estrus, first AI service, and cumulative pregnancy rate were affected by health status. Regression analysis for survival showed an interaction of diet and health status for days open. High CP diets tended to increase days open when cows had major health problems; otherwise, a high CP diet decreased days open. The implementation of a strict reproductive management program allowed high reproductive efficiency goals to be achieved regardless of plasma urea N concentrations.

Intravascular infusion of lipid into ewes stimulates production of progesterone and prostaglandin.

Effects of infusion of a lipid emulsion into ewes during mid-to late diestrus on serum concentrations of total cholesterol (TC), progesterone (P4), prostaglandin (PG) F2 alpha metabolite (PGFM), and PGE2, and on ovulation rate were examined. In experiment 1, ewes received infusions of either saline (S, n = 3) or soybean oil emulsion (SB, n = 3) for 5 h on each of Days 9-13 of the estrous cycle. In experiment 2, ewes received infusions of either S (n = 4), SB (n = 5), or olive oil emulsion (OO, n = 5) for 5 h on each of Days 9 through 15 of the estrous cycle. In both experiment 1 and experiment 2, infusion of lipid increased serum concentrations of TC and P4, which declined with time after infusion was terminated (treatment x hour interaction, experiment 1: TC, p < 0.01, P4, p < 0.01; experiment 2: TC, p < 0.01, P4, p < 0.001). Serum PGFM and PGE2 concentrations were greater in lipid-infused ewes than in controls on Days 13 through 15 (treatment x hour interaction; p < 0.03, p < 0.001, respectively). Duration of the estrous cycle was shortened in OO-infused ewes (16.2 +/- 0.4 days) compared with that of SB- and S-infused ewes (17.2 +/- 0.2 and 18.0 +/- 0.0 days, respectively; p < 0.01). Numbers of corpora lutea and follicles, and diameter of follicles > 4 mm did not differ among treatment groups on Day 14 of the succeeding cycle after infusion. These data indicate that lipid infusion stimulated increases in serum concentrations of TC, P4, and prostaglandins and may shorten the estrous cycle.

Proteases stimulate fertilization-like responses in starfish eggs.

Application of proteases to eggs of the starfish, Asterina miniata, caused several responses like those seen at fertilization. Cortical granule exocytosis and fertilization envelope elevation occurred within about 1 min after exposure to trypsin, chymotrypsin, or pronase; protease inhibitors prevented these responses. Kallikrein caused cortical granule exocytosis and fertilization envelope elevation, but this response required more time (congruent to 30 min). Exocytosis was also seen in response to a recombinant trypsin, but not to a point-mutated trypsin without proteolytic activity. The extent of exocytosis was similar to that seen at fertilization, as measured by the fluorescent dye FM 1-43. In addition to causing exocytosis, application of trypsin, chymotrypsin, or pronase caused an increase in intracellular free calcium, detected by calcium green dextran, and stimulation of DNA synthesis, detected by incorporation of bromodeoxyuridine. Exocytosis also occurred when trypsin or chymotrypsin was applied in artificial sea water in which the free calcium was reduced to a low level (40-70 nM) such that Ca influx would be reduce by > 10,000-fold; this indicated that the proteases did not act by damaging the eggs and causing external calcium to leak into the cytoplasm. These findings show that there is an extracellularly exposed protein that when proteolyzed can induce fertilization-like responses; this protein may be a receptor that transduces a signal from the sperm to initiate egg activation at fertilization.

Surface expression of the pre-beta subunit of fertilin is regulated at a post-translational level in guinea pig spermatids.

During spermiogenesis in the guinea pig, the spermatid plasma membrane becomes sequentially segregated into three domains of distinct composition. We have previously shown that plasma membrane proteins appear on the cell surface in a temporally regulated manner such that proteins localized to the same domain reach the surface membrane at the same time in sperm development. Fertilin is a cell surface protein restricted to the whole head of testicular sperm; like other proteins restricted to this membrane domain, it does not appear on the cell surface until late (steps 11-13) in spermiogenesis. Using confocal microscopy of immunofluorescently labeled testicular sections, we demonstrate that the pre-beta subunit of fertilin is present in pachytene spermatocytes. It is initially observed in long, strand-like structures that likely represent the endoplasmic reticulum; it later appears in a punctate distribution in the cytoplasm of early spermatids prior to its appearance on the surface membrane in late elongating spermatids. Immunoblotting experiments confirm the presence of the fertilin pre-beta subunit in spermatocytes and early spermatids at the same apparent molecular weight as in later stages. These results suggest that the appearance of fertilin pre-beta subunit on the spermatid surface is regulated by a post-translational mechanism.

Effect of supplemental fish meal on the lactation and reproductive performance of dairy cows.

The influence of high protein diets (21% CP, DM basis), containing varied percentages of RUP, on lactation performance and fertility was evaluated. Sixty-two Holstein cows (65% multiparous) were blocked by age and randomly assigned to a 2 x 2 x 2 factorial design from d 12 to 125 postpartum. Factor 1 was 0 or 3.5% fish meal diet, factor 2 was location (Calan door versus free stall), and factor 3 was parity (first versus second or later). The soybean meal diet consisted of alfalfa hay, corn silage, barley, and soybean meal. The fish meal diet contained 3.5% fish meal (ruminant grade menhaden) that replaced a portion of the soybean meal. Cows fed the fish meal diet (40% RUP) had DMI, BW, and body condition similar to those of cows offered the soybean meal diet (34% RUP). Cows receiving the fish meal supplement tended to have higher milk protein production throughout the trial, higher milk production during the first 6 wk, and significantly lower ruminal ammonia concentrations than cows receiving the soybean meal diet. Differences in reproductive performance were not significant except for a diet by housing location interaction for conception rates from first AI.

Evidence for both tyrosine kinase and G-protein-coupled pathways leading to starfish egg activation.

To investigate possible pathways leading to egg activation at fertilization, the ability of exogenously introduced tyrosine kinase and G-protein-coupled receptors to mimic events of fertilization was examined. Oocytes of the starfish Asterina miniata were injected with RNA for a chimeric receptor consisting of the extracellular domain of the beta form of the mouse platelet-derived growth factor (PDGF) receptor and the transmembrane/intracellular domain of the human fibroblast growth factor (FGF) receptor, or with RNA for the rat serotonin 1c receptor. These oocytes were cultured for 1 to 3 days and then matured with 1-methyladenine. In response to PDGF or serotonin, the injected eggs underwent responses like those at fertilization: cortical granule exocytosis, a rise in intracellular free calcium, and DNA synthesis. Some of these artificially activated eggs cleaved, and some of the PDGF-activated eggs were observed to form larvae. A PDGF/FGF receptor with a point mutation which eliminated its ability to interact with phospholipase C-gamma did not cause fertilization-like responses. Thus components of a signaling pathway involving phospholipase C-gamma, characteristic of tyrosine kinase receptors, as well as components of a pathway involving a G-protein and phospholipase C-beta, characteristic of G-protein-coupled receptors, appear to be present in starfish eggs. Either or both could function in egg activation at fertilization.