The methodological rigour of systematic reviews in environmental health.

While systematic reviews (SRs) are often perceived as a "gold standard" for evidence synthesis in environmental health and toxicology, the methodological rigour with which they are currently being conducted is unclear. The objectives of this study are (1) to provide up-to-date information about the methodological rigour of environmental health SRs and (2) to test hypotheses that reference to a pre-published protocol, use of a reporting checklist, or being published in a journal with a higher impact factor, are associated with increased methodological rigour of a SR. A purposive sample of 75 contemporary SRs were assessed for how many of 11 recommended SR practices they implemented. Information including search strategies, study appraisal tools, and certainty assessment methods was extracted to contextualise the results. The included SRs implemented a median average of 6 out of 11 recommended practices. Use of a framework for assessing certainty in the evidence of a SR, reference to a pre-published protocol, and characterisation of research objectives as a complete Population-Exposure-Comparator-Outcome statement were the least common recommended practices. Reviews that referenced a pre-published protocol scored a mean average of 7.77 out of 10 against 5.39 for those that did not. Neither use of a reporting checklist nor journal impact factor was significantly associated with increased methodological rigour of a SR. Our study shows that environmental health SRs omit a range of methodological components that are important for rigour. Improving this situation will require more complex, comprehensive interventions than simple use of reporting standards.

Transcriptional regulation of sertoli cell differentiation by follicle-stimulating hormone at the level of the c-fos and transferrin promoters.

One of the primary endocrine hormones that influence the onset of Sertoli cell differentiation at puberty and help maintain differentiation in the adult testis is FSH. FSH can modulate the majority of Sertoli cell differentiated functions, including stimulation of the iron-binding protein transferrin. Previous studies have shown that FSH alters the levels of cAMP and the immediate early gene c-fos. The current study was designed to investigate the transcriptional regulation of Sertoli cell differentiation by examining the actions of FSH on the promoter of the immediate early gene c-fos and the promoter of the downstream differentiated function gene transferrin. The regulation of c-fos by FSH was investigated with various chloramphenicol acetyltransferase (CAT) constructs containing segments of the c-fos promoter, such as the serum response element (SRE), cAMP response element (CRE), and AP1/phorbol ester/TPA response element (TRE), that were transfected into cultured Sertoli cells. Observations indicate that FSH can stimulate all three response elements, as well as a whole c-fos promoter construct. Interestingly, FSH was found to have a more dramatic effect on the SRE-CAT than a cAMP analog, suggesting a difference in the actions of the two agents. Gel mobility shift assays were performed to confirm the reporter gene results. Nuclear extracts of FSH-stimulated Sertoli cells caused a labeled AP1 oligonucleotide to form a DNA/protein complex (i.e., gel shift), indicating activation of the c-fos gene and binding of the c-fos/jun complex. Nuclear extracts from both FSH- and cAMP-stimulated Sertoli cells promoted similar gel shifts with SRE and CRE oligonucleotides. This observation supports the reporter gene data in indicating that FSH can influence both the SRE and CRE. A gel mobility shift assay was also performed with an oligonucleotide containing the 5'-flanking ETS domain of the SRE (ETS-SRE) that allows the formation of a ternary complex. FSH-stimulated Sertoli cell nuclear extracts were found to promote a unique ETS-SRE gel shift not present in cAMP-stimulated cells. The observations imply that FSH actions on the SRE are in part distinct from the actions of cAMP. Transferrin gene expression was examined to study the downstream regulation of Sertoli cell differentiation. CAT constructs containing deletion mutants of a 3-kb mouse transferrin promoter were used. When transfected into Sertoli cells, the 581-bp transferrin minimal promoter, previously shown to contain a CRE, had a significant response to cAMP and FSH. The 1.6-, 2.6-, and 3-kg transferrin promoter constructs also responded to FSH and cAMP to the same extent as, or to a lesser extent than, the 581-bp minimal promoter. Interestingly, the actions of FSH on the 581-bp minimal transferrin promoter were more dramatic than those of cAMP. The importance of FSH-induced c-fos in the regulation of transferrin expression was demonstrated in the current study when a c-fos antisense oligonucleotide was found to partially inhibit (50%) the ability of FSH to induce the expression of a transferrin promoter (CAT) construct. Therefore, FSH appears to act through multiple transcriptional activation pathways. The first involves cAMP and the CRE at both early-event genes (e.g., c-fos) and downstream genes (e.g., transferrin). It is likely that other pathways involve alternate signal transduction events (e.g., calcium mobilization) and promoter response elements (e.g., SRE). These multiple pathways may act in a compensatory manner to assure the ability of FSH to influence Sertoli cell differentiation and/or in a synergistic manner to amplify FSH actions.

Role of specific response elements of the c-fos promoter and involvement of intermediate transcription factor(s) in the induction of Sertoli cell differentiation (transferrin promoter activation) by the testicular paracrine factor PModS.

A mesenchymal-epithelial cell interaction exists in the testis between the Sertoli cells that form the seminiferous tubule and the mesenchymal-derived peritubular myoid cells that surround the tubule. Analysis of the mesenchymal-epithelial interactions between these cells revealed the local production of a mesenchymal factor, PModS. PModS modulates the differentiated functions of Sertoli cells in vitro, including stimulation of the iron-binding protein transferrin (Tf). Previous results have indicated that PModS-induced Tf gene expression involves the activation of immediate early genes. One of the immediate early genes was identified as c-fos. The importance of c-fos was demonstrated in the current study when a c-fos antisense oligonucleotide was found to inhibit the ability of PModS to induce the expression of a Tf promoter-chloramphenicol acetyltransferase (CAT) construct. The regulation of c-fos by PModS was investigated with various CAT constructs containing segments of the c-fos promoter, such as the serum response element (SRE), sis-inducible element (SIE), cAMP response element (CRE), and phorbol ester/TPA response element (TRE), transfected into cultured Sertoli cells. PModS has no effect on cAMP response element-CAT or TRE-CAT, suggesting that PModS does not act through stimulation of cAMP and protein kinase C pathways. PModS was found to activate the c-fos SRE-CAT construct and the SIE-CAT construct. A construct containing both SIE and SRE was stimulated to the same degree as either element alone. Gel mobility shift assays using nuclear extracts from PModS-stimulated Sertoli cells and a radiolabeled SRE oligonucleotide resulted in retarded mobility of a DNA-protein complex. A gel shift with a SRE oligonucleotide containing an ETS domain resulted in a unique shift only detected in PModS stimulated cells. PModS also promoted a gel shift with the SIE that is adjacent to the SRE on the c-fos promoter. The data imply that PModS can activate the c-fos promoter through the SRE and SIE. PModS caused a labeled activating protein 1 (AP1) oligonucleotide to form a DNA-protein complex, indicating activation of the c-fos gene and binding of the c-fos/jun complex. To study the downstream regulation of Sertoli cell differentiation, Tf gene expression was examined. CAT constructs containing deletion mutants of a 3-kilobase (kb) mouse Tf promoter were used. When transfected into Sertoli cells the 581-base pair Tf minimal promoter had only a slight response to PModS, but was activated by FSH. The 2.6-kb Tf promoter construct responded to PModS.(ABSTRACT TRUNCATED AT 400 WORDS)

Extrahepatic expression of fibrinogen by granulosa cells: potential role in ovulation.

Granulosa cells from ovarian follicles were shown to express and secrete fibrinogen under the control of FSH. Conditioned medium was collected from granulosa cell cultures and found to contain FSH-dependent 50-kilodalton (kDa) and 93- to 95-kDa proteins. N-Terminal microsequence analysis identified these proteins as fibrinogen beta- and gamma-chains, respectively. Proteins migrating at 93 and 95 kDa contain identical gamma-chain sequences at the N-terminal, suggesting differential processing of fibrinogen. These fibrinogen chains were specifically detected with antifibrinogen antibodies in immunoblot and immuno-precipitation analysis. Fibrinogen gamma-chain mRNA was detected in granulosa cells by polymerase chain reaction analysis, confirming fibrinogen gene expression by these cells. Fibrinogen secretion by granulosa cells was measured by a competitive enzyme-linked immunosorbent assay. Granulosa cells treated with FSH (100 ng/ml) secreted 2-3 times more fibrinogen than untreated cells. These data show that fibrinogen, a major product of the liver, is also a secretory product of granulosa cells. This provides a novel extrahepatic site of fibrinogen expression. As hepatic parenchymal cells normally maintain high circulating levels of fibrinogen, the local production of fibrinogen in the ovary is anticipated to have specialized functions. Locally produced fibrinogen may be important in the clotting process following tissue rupture at ovulation. In addition, fibrinogen fragments may be involved in the mechanism of ovulation by increasing the activity of tissue-type plasminogen activator to control the proteolytic activity required for ovulation.

Cell-cell interactions and the regulation of testis function.

Regulatory interactions have been shown to occur between all the testicular cell types considered. The paracrine factors mediating these interactions generally influence either cellular growth or differentiation. The regulation of cellular growth is essential in the developing testis and is required for the maintenance of spermatogenesis in the adult testis. The rapid rate of germinal cell proliferation and the continuous but slowed growth of the peritubular cells and Leydig cells requires the presence of specific growth factors in the adult. Therefore, cell-cell interactions have evolved that involve growth factors such as IGF, TGF-alpha, TGF-beta and NGF. Other growth factors such as FGF or less characterized components like the seminiferous growth factor (SGF) also may be involved in the paracrine regulation of testis cell growth. An alternate cellular parameter to cell growth to consider is the regulation of cellular function and differentiation. A number of endocrine agents and locally produced paracrine factors have been shown to control and maintain testis cell function and differentiation. Cell-cell interactions mediated by factors such as androgens, POMC peptides, and PModS are all primarily directed at the regulation of cellular differentiation. Therefore, the agents which mediate cell-cell interactions in the testis can generally be categorized into factors that regulate cell growth or those which influence cellular differentiation. The specific cell-cell interactions identified will likely be the first of a large number of cellular interactions yet to be investigated. Although a number of potentially important cell-cell interactions have been identified, future research will require the elucidation of the in vivo physiological significance of these interactions. The existence of different cell types and potential cell-cell interactions in a tissue implies that the actions of an endocrine agent on a tissue will not simply involve a single hormone and single cell. The endocrine regulation of testis function will have effects on cell-cell interactions and be affected by local cell-cell interactions. The ability of LH to influence Leydig cell androgen production promotes a cascade of interactions mediated through several cell types to maintain the process of spermatogenesis. FSH actions on Sertoli cells also promote cell-cell interactions that influence germinal cell development, peritubular myoid cell differentiation and Leydig cell function. Therefore, elucidation of the endocrine regulation of testis function requires an understanding of the local cell-cell interactions in the testis.

Processing of cues for stop consonant voicing by young hearing-impaired listeners.

To assess whether young hearing-impaired listeners are as sensitive as normal-hearing children to the cues for stop consonant voicing, we presented stimuli from along VOT continua to young normal-hearing listeners and to listeners with mild, moderate, severe, and profound hearing impairments. The response measures were the location of the phonetic boundaries, the change in boundaries with changes in place of articulation, and response variability. The listeners with normal hearing sensitivity and those with mild and moderate hearing impairments did not differ in performance on any response measure. The listeners with severe impairments did not show the expected change in VOT boundary with changes in place of articulation. Moreover, stimulus uncertainty (i.e., the number of possible choices in the response set) affected their response variability. One listener with profound impairment was able to process the cues for voicing in a normal fashion under conditions of minimum stimulus uncertainty. We infer from these results that the cochlear damage which underlies mild and moderate hearing impairment does not significantly alter the auditory representation of VOT. However, the cochlear damage underlying severe impairment, possibly interacting with high signal presentation levels, does alter the auditory representation of VOT.

Identification and discrimination of a synthesized voicing contrast by normal and sensorineural hearing-impaired children.

The identification and discrimination of a stop-consonant voicing contrast (/da/--/ta/) was assessed in children and adolescents who had moderate, severe, and profound sensorineural hearing losses. The location of the perceptual boundary between /da/ and /ta/ did not differ between normal listeners and listeners with moderate losses. Of the ten listeners with severe losses, five evidenced normal boundaries, three evidenced longer-than-normal boundaries, and two could not identify the stimuli at all. Of the three listeners with profound hearing losses, one could identify normally, and two could not identify at all. For the most part, discrimination data mirrored identification data. However, in some instances listeners were able to discriminate between stimuli they could not differentially identify. These subjects appeared to have the auditory capacity to resolve differences in voice-onset-time but could not use this capacity to make phonetic identification.

Relieving parental anxiety a booklet for parents of an infant in NICU.

The transfer of a sick newborn infant to a Newborn Intensive Care Unit evokes an acute emotional crisis for the parents. In order to help the family master this crisis, the authors have developed a parent booklet entitled, "A Sign of Hope." This pamphlet introduces the parents to Newborn Intensive Care even before the transfer of the baby to the regional hospital. By merely changing a few words, telephone numbers, and maps, this brochure can be adapted for use at most Level II or III Newborn Special Care Units.