Perceived barriers to receiving HIV services in groups of traditionally underserved individuals: empirical models

Persons living with HIV/AIDS face many issues that make them highly vulnerable to a number of health and social problems. As the demographics of the epidemic have shifted in recent years, many members of traditionally underserved groups have encountered barriers to entering the services system. This article uses data from seven national demonstration projects funded to enroll persons with HIV/AIDS who tend to "fall through the cracks" and help them access needed services. Data on the initial perceptions of the participants about barriers to accessing services were related to 17 indicators of traditionally underserved status including demographic characteristics and behavioral variables using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Through the modeling methods, the groups most likely to experience a large number of barriers to service participation are identified. Having children needing care is particularly predictive of the level of barriers to care.

A guinea pig model of low-dose Mycobacterium bovis aerogenic infection

In order to develop a model of Mycobacterium bovis infection with pathogenetical relevance, a modified version of the Henderson apparatus was used to deliver infectious aerosols directly to the snouts of guinea pigs. Aerosols generated from 10(6), 10(7), 10(8)CFU/ml M. bovis suspensions established disease in every animal, with estimated retained doses of 10, 100, 1000 CFU, respectively. For comparison, other guinea pigs were inoculated with 100 CFU M. bovis intramuscularly (i.m.). Pathology and bacterial colonisation of lungs and spleen varied according to the dose and route of inoculation. Animals inoculated i.m. gave a significant cutaneous tuberculin hypersensitivity reaction earlier after testing than those infected aerogenically. A serological response to M. bovis antigens was detected in all infected animals. Intensity of antigen recognition was dose-dependent and although the range of antigens recognised varied between animals, a 25 kDa antigen present in the cell fraction was serodominant. Thus, a reproducible guinea pig model has been defined that may be suitable for virulence, vaccination, and immunological studies.

Smoking is associated with increased hepatic lipase activity, insulin resistance, dyslipidaemia and early atherosclerosis in Type 2 diabetes

We have studied the relationships between hepatic lipase activity, smoking, dyslipidaemia insulin resistance, and early atherosclerosis in 67 Type 2 diabetic subjects, 47 non-smokers and 20 smokers. Insulin resistance was measured using an insulin modified frequently sampled intravenous glucose tolerance test. Early atherosclerosis was assessed using high-resolution ultrasound to measure carotid intima media thickness (IMT) and an arterial ultrasonic score (AUS). Smokers had higher serum cholesterol and triglyceride, lower HDL and HDL2 cholesterol as well as increased hepatic lipase activity. They were also more insulin resistant than non-smokers. Smokers also had higher patient AUS scores. On multiple regression analysis, hepatic lipase activity emerged as the most significant variable affecting patient AUS. We suggest that smoking accentuates the dyslipidaemia of Type 2 diabetic subjects and this is associated with increased hepatic lipase activity. This may be one mechanism whereby smoking further increases the risk of cardiovascular disease in Type 2 diabetes.

Improving the well-being of elderly patients via community pharmacy-based provision of pharmaceutical care: a multicentre study in seven European countries

OBJECTIVE

This study aimed to measure the outcomes of a harmonised, structured pharmaceutical care programme provided to elderly patients (> or =65 years of age) by community pharmacists in a multicentre international study performed in 7 European countries.

DESIGN AND SETTING

The study was a randomised, controlled, longitudinal, clinical trial with repeated measures performed over an 18-month period. A total of 104 intervention and 86 control pharmacy sites participated in the research and 1290 intervention patients and 1164 control patients were recruited into the study.

MAIN OUTCOME MEASURES AND RESULTS

A general decline in health-related quality of life over time was observed in the pooled data; however, significant improvements were achieved in patients involved in the pharmaceutical care programme in some countries. Intervention patients reported better control of their medical conditions as a result of the study and cost savings associated with pharmaceutical care provision were observed in most countries. The new structured service was well accepted by intervention patients and patient satisfaction with the services improved during the study. The pharmacists involved in providing pharmaceutical care had a positive opinion on the new approach, as did the majority of general practitioners surveyed. The positive effects appear to have been achieved via social and psychosocial aspects of the intervention, such as the increased support provided by community pharmacists, rather than via biomedical mechanisms.

CONCLUSIONS

This study is the first large-scale, multicentre study to investigate the effects of pharmaceutical care provision by community pharmacists to elderly patients. Future research methodology and implementation will be informed by the experience gained from this challenging trial.

Effects of coping style and BRCA1 and BRCA2 test results on anxiety among women participating in genetic counseling and testing for breast and ovarian cancer risk

Using the monitoring process model (MPM), the authors examined the immediate effects of coping style and test results on the psychological distress of women at increased risk for breast and/or ovarian cancers. Cases selected for analysis were 107 probands and relatives of positive probands participating in genetic counseling and testing for heritable cancer risk. Specifically, the authors explored the relationships among coping style (high and low monitoring), test results (BRCA1 and BRCA2 mutation carrier and noncarrier status), and psychological distress (state anxiety). Consistent with the MPM, higher monitoring was associated with greater psychological distress while anticipating genetic test results. After test results were disclosed, greater distress was associated with testing positive for a mutation. The implications of the findings for breast and ovarian cancer patients are discussed.

Applications of gene replacement technology to Streptomyces clavuligerus strain development for clavulanic acid production

Cephamycin C production was blocked in wild-type cultures of the clavulanic acid-producing organism Streptomyces clavuligerus by targeted disruption of the gene (lat) encoding lysine epsilon-aminotransferase. Specific production of clavulanic acid increased in the lat mutants derived from the wild-type strain by 2- to 2.5-fold. Similar beneficial effects on clavulanic acid production were noted in previous studies when gene disruption was used to block the production of the non-clavulanic acid clavams produced by S. clavuligerus. Therefore, mutations in lat and in cvm1, a gene involved in clavam production, were introduced into a high-titer industrial strain of S. clavuligerus to create a double mutant with defects in production of both cephamycin C and clavams. Production of both cephamycin C and non-clavulanic acid clavams was eliminated in the double mutant, and clavulanic acid titers increased about 10% relative to those of the parental strain. This represents the first report of the successful use of genetic engineering to eliminate undesirable metabolic pathways in an industrial strain used for the production of an antibiotic important in human medicine.

Streptavidin paramagnetic particles provide a choice of three affinity-based capture and magnetic concentration strategies for retroviral vectors

Three strategies have been designed to concentrate infectious retroviral vectors from the supernatants of human- (HT1080) and murine- (NIH 3T3) based packaging cells. Streptavidin-conjugated paramagnetic particles in conjunction with (i) antibodies directed against murine fibronectin, (ii) biotinylated lectins, or (iii) biotin-modified packaging cell-surface proteins allow affinity-mediated magnetic concentration of retroviral vectors. Retroviral titers (assayed by colony formation of human myeloid K562 cells) are increased by 1-4 x 10(3)-fold after volume reductions of only 125-fold. Using these procedures, preparations of 5 x 10(8) cfu/ml are routinely made from relatively low-titer (2-5 x 10(5) cfu/ml) starting material. High-titer (paramagnetic) retroviral vector preparations can be used for magnetic field-dependent retroviral infection in vitro. Magnetic field-dependent localization such as this may enable the in vivo administration of formulations that concentrate retroviral infection to the required target tissues and organs.

Obstetric care. Is there risk of pressure damage after epidural anaesthesia?

Anecdotal evidence suggests that there is an increase in the incidence of pressure damage to women in labour. This appears to be associated with epidural anaesthesia. Epidural anaesthesia used to control pain in childbirth causes loss of sensation and a degree of motor block, which removes the women's reflexes and ability to reposition to prevent pressure damage. The large amount of fluids present during childbirth may also increase the risk of pressure damage, especially in association with shear and friction. A combination of unfamiliarity of pressure ulcer prevention techniques among midwives, and the type of delivery room equipment, that is currently available, may leave young healthy women at risk of developing pressure ulcers.

Parental communication of BRCA1/2 genetic test results to children

The aim of this study was to evaluate the likelihood, correlates, and psychological impact of parental communication to children of parents' BRCA1/2 genetic test results for breast cancer risk. Subjects were 133 adult members of high risk families. Sociodemographic, clinical, and psychological distress variables were assessed during a baseline telephone interview conducted prior to patient education and test result notification. Parental communication of test results to children and parental psychological distress and coping efforts were assessed 1 month post-genetic counseling and receipt of test results. Mothers (versus fathers), and persons with higher levels of baseline general distress, were significantly more likely to communicate their test results to children. Post-counseling coping efforts, both active and avoidant, were positively associated with post-counseling distress levels. However, communication of test results to children did not relate to changes in distress. In conclusion, parents with higher levels of pre-counseling general psychological distress may be more likely to communicate their genetic test results to children; however, this act does not minimize their distress and could possibly generate distress in their youngsters. Research is needed to evaluate the process and content of post-test disclosure episodes and the impact on participant, child, and family functioning.

The instruction in pelvic floor exercises provided to women during pregnancy or following delivery

OBJECTIVES

to examine the instruction in pelvic floor exercises given to women during pregnancy or following delivery, to assess the quality of any instruction provided, and to consider these in light of the women's views about the service.

DESIGN

a postal questionnaire was sent to a sample of women when they reached 34 weeks of pregnancy and a second at 8 weeks postpartum. A sub-sample of women who reported symptoms of stress incontinence at 8 weeks postpartum were interviewed about the instruction in pelvic floor exercises that they received during their pregnancy, or in the puerperium.

PARTICIPANTS

of the 918 women who were sent the first questionnaire, 717 returned it completed (78%). Five-hundred-and-seventy-two of 894 women (64%) completed the second questionnaire. Forty-two of 179 symptomatic women (23%) took part in an interview.

FINDINGS

55% of women received some form of instruction in pelvic floor exercises by 34 weeks of pregnancy. Eighty-six percent received instruction following birth. The way the information was given varied, ranging from a brief reminder, to exercising in a class with an instructor. The information was provided by a range of health professionals, and no single profession appeared to undertake responsibility for the service. As a result, the views of the service varied. A few women reported that they had received good quality instruction, others were critical of it, and a small number reported that they had received no instruction at all. The widespread practice of leaving a leaflet by the women's beds during their stay in hospital, was criticised by a large proportion of the women.

KEY CONCLUSION

the instruction in pelvic floor exercises by health service professionals was provided on an ad hoc basis. In many instances, the programme of instruction did not meet recommendations made in the literature. It is likely that the success of randomised controlled trials reported in the literature would not be repeated in the 'real world' Implications for practice: there is a need for the service to be reorganised so that all women receive high-quality instruction during pregnancy, with a reminder to exercise following birth. This could help to prevent, or relieve, the symptoms of stress incontinence that frequently occur at these times.

"I got some swords and you're dead!": violent fantasy, antisocial behavior, friendship, and moral sensibility in young children

Relations between an early interest in violent fantasy and children's social understanding, antisocial and emotional behavior, and interactions with friends were investigated in 40 "hard-to-manage" preschoolers and 40 control children matched for gender, age, and school and ethnic background. Children were filmed alone in a room with a friend, and tested on a battery of cognitive tests, including false-belief, executive function, and emotion understanding tasks. Teachers reported on their friendship quality. At age 6 years, the children's understanding of the emotional consequences of antisocial and prosocial actions was studied. The hard-to-manage group showed higher rates of violent fantasy; across both groups combined, violent fantasy was related to poor executive control and language ability, frequent antisocial behavior, displays of anger and refusal to help a friend, poor communication and coordination of play, more conflict with a friend, and less empathic moral sensibility 2 years later. The usefulness of a focus on the content of children's pretend play-in particular, violent fantasy-as a window on children's preoccupations is considered.

Interaction of Escherichia coli hemolysin with biological membranes. A study using cysteine scanning mutagenesis

Escherichia coli hemolysin (HlyA) is a membrane-permeabilizing protein belonging to the family of RTX-toxins. Lytic activity depends on binding of Ca2(+) to the C-terminus of the molecule. The N-terminus of HlyA harbors hydrophobic sequences that are believed to constitute the membrane-inserting domain. In this study, 13 HlyA cysteine-replacement mutants were constructed and labeled with the polarity-sensitive fluorescent probe 6-bromoacetyl-2-dimethylaminonaphthalene (badan). The fluorescence emission of the label was examined in soluble and membrane-bound toxin. Binding effected a major blue shift in the emission of six residues within the N-terminal hydrophobic domain, indicating insertion of this domain into the lipid bilayer. The emission shifts occurred both in the presence and absence of Ca2(+), suggesting that Ca2(+) is not required for the toxin to enter membranes. However, binding of Ca2(+) to HlyA in solution effected conformational changes in both the C-terminal and N-terminal domain that paralleled activation. Our data indicate that binding of Ca2(+) to the toxin in solution effects a conformational change that is relayed to the N-terminal domain, rendering it capable of adopting the structure of a functional pore upon membrane binding.

Statistical assessment of violations of water quality standards under Section 303(d) of the clean water act

Section 303(d) of the Clean Water Act requires states to assess the condition of their waters and to implement plans to improve the quality of waters identified as impaired. U.S. Environmental Protection Agency guidelines require a stream segment to be listed as impaired when greater than 10% of the measurements of water quality conditions exceed numeric criteria. This can be termed a "raw score" assessment approach. Water quality measurements are samples taken from a population of water quality conditions. Concentrations of pollutants vary naturally, measurement errors may be made, and occasional violations of a standard may be tolerable. Therefore, it is reasonable to view the assessment process as a statistical decision problem. Assessment of water quality conditions must be cognizant of the possibility of type I (a false declaration of standards violation) and type II (a false declaration of no violation) errors. The raw score approach is shown to have a high type I error rate. Alternatives to the raw score approach are the Binomial test and the Bayesian Binomial approach. These methods use the same information to make decisions but allow for control of the error rates. The two statistical methods differ based on consideration of prior information about violation. Falsely concluding that a water segment is impaired results in unnecessary planning and pollution control implementation costs. On the other hand, falsely concluding that a segment is not impaired may pose a risk to human health or to the services of the aquatic environment. An approach that recognizes type I and type II error in the water quality assessment process is suggested.

Fusagene vectors: a novel strategy for the expression of multiple genes from a single cistron

Transduction of cells with multiple genes, allowing their stable and co-ordinated expression, is difficult with the available methodologies. A method has been developed for expression of multiple gene products, as fusion proteins, from a single cistron. The encoded proteins are post-synthetically cleaved and processed into each of their constituent proteins as individual, biologically active factors. Specifically, linkers encoding cleavage sites for the Golgi expressed endoprotease, furin, have been incorporated between in-frame cDNA sequences encoding different secreted or membrane bound proteins. With this strategy we have developed expression vectors encoding multiple proteins (IL-2 and B7.1, IL-4 and B7.1, IL-4 and IL-2, IL-12 p40 and p35, and IL-12 p40, p35 and IL-2 ). Transduction and analysis of over 100 individual clones, derived from murine and human tumour cell lines, demonstrate the efficient expression and biological activity of each of the encoded proteins. Fusagene vectors enable the co-ordinated expression of multiple gene products from a single, monocistronic, expression cassette.

Functions of the subunits in the FlhD(2)C(2) transcriptional master regulator of bacterial flagellum biogenesis and swarming

In enterobacteria like Salmonella, biogenesis of cell surface flagella needed for motility is dependent upon the master operon flhDC at the apex of the flagellar gene hierarchy. The operon products FlhD and FlhC act together in a FlhD(2)C(2 )heterotetramer to induce flagellar gene transcription, while FlhD also represses cell septation. The flhDC operon is pivotal to differentiation into elongated hyperflagellated swarm cells that undergo multicellular migration, most strikingly in Proteus. We set out to establish the mechanism of action of the FlhD(2)C(2) multimer. In Proteus swarm cell extracts, all the FlhC was assembled into the FlhD(2)C(2 )transcription activator, but FlhD additionally formed approximately equimolar amounts of a FlhD(2) homodimer. Both FlhD and FlhC subunits homodimerised in vivo and in vitro, suggesting that self-interactions stabilise the FlhD(2)C(2 )complex. The FlhC and FlhD subunit proteins were separately expressed and purified, and the FlhD(2)C(2)heterotetramer was reconstituted in vitro. Purified FlhC bound specifically and cooperatively to the promoter region of the flhDC-regulated flhB flagellar gene in the absence of FlhD. Purified FlhD was unable to bind this target DNA, but binding by the FlhD(2)C(2)complex was approximately tenfold greater than the FlhC subunit alone, suggesting that FlhD potentiated the FlhC/DNA interaction. In support of this possibility, pre-incubation of FlhC with FlhD reduced the apparent dissociation constant, K(D), for the FlhC/DNA complex from 100 nM to 13 nM. Furthermore, in competition assays, FlhD substantially increased the specificity of DNA recognition by FlhC, and also stabilised the resultant labile protein/DNA complex, prolonging its half-life from around two minutes to more than 40 minutes. FlhD(2)C(2)is therefore an atypical prokaryotic transcription activator in which interaction of the FlhC subunit with DNA target sequences is enhanced by the coexpressed helper subunit FlhD.

Participation of minorities in cancer research: the influence of structural, cultural, and linguistic factors

Overall, participation rates in cancer clinical trials are very low, ranging from 3 to 20% of eligible participants. However, participation rates are especially low among the socially disadvantaged and racial/ethnic minority groups that have been historically underrepresented in clinical research. Structural factors such as study duration, treatment or intervention schedule, cost, time, followup visits, and side effects represent more of a barrier to participation among these groups compared with white, non-Hispanics. Attitudes, beliefs, perceptions, and knowledge regarding clinical research, and cultural characteristics of underrepresented minorities pose additional barriers to participation. This article focuses on the structural, cultural, and linguistic factors that affect participation in clinical cancer research for each major U.S. racial/ethnic group. Low socioeconomic status, speaking a primary language other than English, differences in communication styles, mistrust of research and the medical system, fear, embarrassment, and lack of knowledge about the origin of cancer appear to have a negative impact on clinical cancer research participation rates. Much of the information about these factors comes from studies of cancer screening because little data is available on the factors that prevent and facilitate participation of minorities in clinical cancer trials specifically. Such research is needed, and, given the heterogeneity within and between minority populations, should occur in several different geographic settings and with as many different minority subpopulations as possible.

Chunnel vision. Export and efflux through bacterial channel-tunnels

The Escherichia coli TolC protein is central to toxin export and drug efflux across the inner and outer cell membranes and the intervening periplasmic space. The crystal structure has revealed that TolC assembles into a remarkable alpha-helical trans-periplasmic cylinder (tunnel) embedded in the outer membrane by a contiguous beta-barrel (channel), so providing a large duct open to the outside environment. The channel-tunnel structure is conserved in TolC homologues throughout Gram-negative bacteria, and it is envisaged that they are recruited and opened, through a common mechanism, by substrate-specific inner-membrane complexes.

Detection of endocrine disrupting chemicals in samples of second trimester human amniotic fluid

Man-made chemicals that have been shown to modulate endocrine function in animal models, so-called "endocrine disrupters", are suspected to play a role in the development of male reproductive tract abnormalities and neurobehaviroal deficits in children. However in utero exposure to environmental contaminants has not been documented previously. The present study was performed to test our hypothesis that man-made chemicals can be quantified in human amniotic fluid during the second trimester. Gas chromatographic/mass spectrometric (GC/MS) analysis was performed on amniotic fluid samples (n=53) from women (n=51) undergoing routine amniocentesis with a mean (+/- SEM) age of 36.5 +/- 0.5 years and between 15 and 23 weeks of gestation. Analytes included common PCB congeners, the DDT metabolites p,p'-DDE, and o,p'-DDE as well as the pesticides: hexachlorobenzene (HCB); and the three isomers of hexachlorocyclohexane (alpha,beta and gamma-HCH). The limit of quantitation (LOQ) for PCBs was 0.01 ng/ml and for the other organochlorines contaminants is was 0.1 ng/ml. The contaminants alpha-HCH with a mean (+/- SD) concentration of 0.15 +/- 0.06 (ng/ml) and p,p'-DDE with a mean (+/- SD) concentration of 0.21 +/- 0.18 ng/ml were detected in the amniotic fluid. PCB specific congeners were detected with a much lower frequency and levels were in the range of the LOQ. Overall one in three amniotic fluid samples tested positive for at least one environmental contaminant. Therefore, we conclude that approximately one in three fetuses in the Los Angeles area are exposed to endocrine modulatory environmental contaminants in utero the consequences of which remain unknown at this time.

The effects of social interactive training on early social communicative skills of children with autism

Growing attention has been directed at the relation between early social communicative skills of children with autism and subsequent development of these children's social and communicative functioning. We reviewed 16 empirical studies that investigated the effects of social interactive interventions designed to increase early social communicative skills of young children with autism by increasing their role as initiator of social interactions. To identify factors relating to treatment effectiveness, we analyzed studies in relation to participant characteristics, settings, target behaviors, training methods, and results. To determine durability of treatment, we analyzed generalization effects across persons, settings, stimuli, and time. Increases were found for social and affective behaviors, nonverbal and verbal communication, eye contact, joint attention, and imitative play. Limited generalization or maintenance of target behaviors was reported. Findings are discussed in relation to critical variables that may relate to treatment effectiveness in future research and practice efforts.

Prophylactic surgery decisions and surveillance practices one year following BRCA1/2 testing

BACKGROUND

Although genetic testing for breast cancer risk is clinically available, its impact on health-related behaviors is unknown. This study examined prophylactic surgery and surveillance behavior during the year following BRCA1/2 gene testing.

METHODS

Participants were female members (n = 216) of hereditary breast-ovarian cancer families (84 mutation carriers, 83 noncarriers and 49 test decliners). In this prospective observational study, utilization of prophylactic surgery and surveillance behavior were assessed 1-year following BRCA1/2 testing.

RESULTS

Only 3% of the unaffected carriers obtained prophylactic mastectomy during the 1-year follow-up period. Among the remaining females, carriers had significantly higher rates of mammography (68%) than noncarriers (44%); (OR = 7.1; C.I. = 1.36-37.1; P = 0.02). However, the adherence rate in carriers was unchanged from baseline, suggesting that this difference is attributable to a reduction in screening among noncarriers. Women ages 25-39 years were significantly less likely to obtain mammograms than those aged 40 years and older. Cancer-related distress had a positive but nonsignificant (P < 0.07) association with adherence in bivariate but not multivariate analysis. With regard to ovarian risk, only 13% of carriers obtained prophylactic oophorectomy; of the remaining female carriers, only 21% reported a CA125 and 15% reported a transvaginal ultrasound.

CONCLUSION

The vast majority of BRCA1/2 carriers may not opt for prophylactic surgery, and many do not adhere to surveillance recommendations. Greater attention to risk communication and medical decision-making is warranted.

Change in perceived barriers and facilitators to treatment among women with HIV/AIDS as a function of psychosocial service utilization

Using a repeated assessment of 185 women with HIV in three national service demonstration projects that focus on reducing barriers to care, self-reported barriers to obtaining services decreased significantly over time. At the earliest time asked, participants scored an average of 5.23 on a measure of barriers to obtaining care. At the most recent time asked, they scored an average of 4.05 on the barrier measure. In a subsample of 122 women with HIV, it was found that self-reported facilitators to obtaining services increased significantly over time. At the first time asked, participants scored an average of 8.40 on a measure of facilitators to receiving services. At the most recent time asked, they scored an average of 8.98 on the facilitator measure. Results are discussed in terms of implications for designing services to minimize barriers and maximize facilitators to care for people living with HIV/AIDS.

Crystal structure of the bacterial membrane protein TolC central to multidrug efflux and protein export

Diverse molecules, from small antibacterial drugs to large protein toxins, are exported directly across both cell membranes of gram-negative bacteria. This export is brought about by the reversible interaction of substrate-specific inner-membrane proteins with an outer-membrane protein of the TolC family, thus bypassing the intervening periplasm. Here we report the 2.1-A crystal structure of TolC from Escherichia coli, revealing a distinctive and previously unknown fold. Three TolC protomers assemble to form a continuous, solvent-accessible conduit--a 'channel-tunnel' over 140 A long that spans both the outer membrane and periplasmic space. The periplasmic or proximal end of the tunnel is sealed by sets of coiled helices. We suggest these could be untwisted by an allosteric mechanism, mediated by protein-protein interactions, to open the tunnel. The structure provides an explanation of how the cell cytosol is connected to the external environment during export, and suggests a general mechanism for the action of bacterial efflux pumps.

Critical windows of exposure for children's health: the reproductive system in animals and humans

Drugs and environmental chemicals can adversely affect the reproductive system. Currently, available data indicate that the consequences of exposure depend on the nature of the chemical, its target, and the timing of exposure relative to critical windows in development of the reproductive system. The reproductive system is designed to produce gametes in far greater excess than would seem to be necessary for the survival of species. Ten to hundreds of millions of spermatozoa are generated daily by most adult male mammals, yet very few of these germ cells succeed in transmitting their genetic material to the next generation. Although the number of oocytes produced in mammalian females is more limited, and their production occurs only during fetal life, most ovaries contain several orders of magnitude more oocytes than ever will be fertilized. Toxicant exposures may affect critical events in the development of the reproductive system, ranging from early primordial germ cell determination to gonadal differentiation, gametogenesis, external genitalia, or signaling events regulating sexual behavior. Although there are differences between the human reproductive system and that of the usual animal models, such models have been extremely useful in assessing risks for key human reproductive and developmental processes. The objectives for future studies should include the elucidation of the specific cellular and molecular targets of known toxicants; the design of a systematic approach to the identification of reproductive toxicants; and the development of sensitive, specific, and predictive animal models, minimally invasive surrogate markers, or in vitro tests to assess reproductive system function during embryonic, postnatal, and adult life.