Factors and Outcomes in Primary Care Physician Retention in Rural Areas

Background: This paper examines factors influencing physicians' decisions to practise in rural communities as well as the results of a programme focused on rural recruitment and retention. Methods: Data from two sources were analysed and discussed: 1) telephone interviews with 20 of 33 (61) recently located rural physicians regarding practice and community factors influencing their practice decisions and 2) a database of 107 graduates of a rural medical education programme who have been in practice for at least three years to examine specialty choice and practice location(s); including moves from their original practice sites. Results: Most rural physicians in this study decided to practise in rural areas because of family ties. Eighty per cent of the physicians participating in the interviews mentioned no negative personal or family factors related to their community of practice. Outcome data on graduates from the rural medical education programme are encouraging. Over 70opt for primary care and rural practice. Over 80have remained in their original rural practice location. Conclusion: Keys to success in rural physician retention seem to include identifying and recruiting medical students ofrural origin and focusing on a healthy practice environment. Policy makers need to work with local government; schools and employers to offer programmes that provide information on health careers in rural areas and begin to identify local youth for induction in rural health care

Addressing issues of maldistribution of health care workers.

INTRODUCTION: The maldistribution of health care workers is a near-universal problem, particularly in developing countries. Shortages have become most critical over the past 2 decades with both out-migration of health care workers from developing to developed countries, and intra-country disparities between urban centres and rural regions. A variety of solutions have been proposed and tried, but in recent years the problem has become increasingly serious. PROGRAMME DESCRIPTION: Over the past 15 years, we have conceptualised and implemented a programme directed at the re-supply of rural physicians to our own state, Illinois, which was recently ranked as low as sixth worse in the US with regard to physician manpower shortages in rural areas. More recently, this programme has been expanded to include other health care workers where there are equivalent shortages in health services accessibility, and the entire programme is now designated as the National Center for Rural Health Professions. PROGRAMME EVALUATION: Currently, the physician programme enjoys a 65% to 70% success rate in terms of the return of physicians to rural communities; a success largely due to the unique selection process, training, and the close relationship between students and faculty. Here, we describe this programme in detail, in the hope that elements of this somewhat unique programme may be "exportable".

Host--parasite relationships of Schistosoma japonicum in mammalian hosts.

Control of schistosomiasis caused by Schistosoma japonicum has been severely hindered by the fact that several non-human mammalian species, including domesticated as well as wild animals, serve as zoonotic carriers of this infection. For effective control, it is imperative that the full host spectrum of this infection is understood. Although about 46 species of mammals are known to carry natural infection with S. japonicum, only a few might be of potential threat to human infection. Generally, in an endemic area, transmission of schistosomiasis to human depends largely on the availability and abundance of permissive hosts. Another important factor that needs to be taken into consideration in developing control measures against S. japonicum is potential strain differences. This review collates pertinent host-parasite relationship of S. japonicum in mammals in an endemic area and assesses the epidemiological significance of these findings for human infection.

Short report: study on the efficacy of a new long-acting formulation of N, N-diethyl-m-toluamide (DEET) for the prevention of tick attachment.

The beneficial effects of N, N-diethyl-m-toluamide (DEET) against biting insects of human and animals appear to last <6 hr after a single application to the skin. To prolong the repellent effects of DEET, recently we developed a new long-acting formulation of DEET called LIPODEET. This preparation was retained in the skin for a longer duration of time with minimal systemic absorption. In this study, we have evaluated the protective effect of three compounds (DEET, LIPODEET, and Morpel 220) against attachment of two species of ticks (Amblyomma americanum and Dermacentor variabilis) to rabbit ears. Results show that LIPODEET and Morpel 220 were highly effective in preventing tick attachment to the skin for a longer duration of time (up to 72 hr) than DEET after a single application. Moreover, LIPODEET was found to be acaricidal to both the species of ticks.

Development and evaluation of LIPODEET, a new long-acting formulation of N, N-diethyl-m-toluamide (DEET) for the prevention of schistosomiasis.

N, N-diethyl-m-toluamide (DEET) is a common and fairly safe active ingredient in many insect repellents. Our recent studies showed that when applied to the skin, DEET has a potent anti-parasitic effect against Schistosoma mansoni. However, the beneficial effects of DEET lasted only for a few minutes, presumably due to its rapid absorption through the skin. In this study, we evaluated different carrier formulations that prolong the activity of DEET in the skin. Among the various formulations analyzed, DEET incorporated into liposomes (LIPODEET) appeared to prolong the activity of DEET for more than 48 hr after a single application. Furthermore, LIPODEET was found to be minimally absorbed through the skin and loss due to washing off was limited. These findings thus suggest LIPODEET is a safe and long-acting formulation of DEET that is quite effective against schistosomiasis.

Evaluation of N,N-diethyl-m-toluamide (DEET) as a topical agent for preventing skin penetration by cercariae of Schistosoma mansoni.

The effect of skin application of N,N-diethyl-m-toluamide (DEET) on the penetration and migration behavior of cercariae of Schistosoma mansoni was evaluated in vitro and in vivo in a mouse model. These studies showed that DEET at concentrations of 7.5% or higher was 100% effective in immobilizing and killing cercariae of S. mansoni in vitro. Ultrastructural studies on such DEET-exposed cercariae showed transformative and degenerative changes involving both tegument and deeper parenchymal structures. Fatal tissue lesions were evident as early as 5 min postexposure to DEET, and became more extensive with increasing exposure time. Cutaneous application of DEET (as a pure chemical in isopropanol or as a commercial insect repellent preparation) was more than 99% effective in preventing entry of S. mansoni cercariae into the mouse tail skin. Radiolabeling and tracer studies confirmed that 7.5% DEET applied to the skin prior to infection was highly effective in preventing schistosomular migration to the lungs.

ICAM-1 and iNOS expression increased in the skin of mice after vaccination with gamma-irradiated cercariae of Schistosoma mansoni.

Host responses to migrating schistosomula of Schistosoma mansoni were compared in the skin of naive, multiply infected, or vaccinated (with gamma-irradiated cercariae) mice during the first 72 hr after cercarial penetration. Cellular response to the migrating parasite was minimal in the skin of naive mice for up to 72 hr after infection. In sharp contrast, the multiply infected or vaccinated animals exhibited a marked inflammatory response in the skin as early as 8 hr after cutaneous penetration of the challenge cercariae. This early inflammatory response in the skin of sensitized animals was characterized by a significant increase in the number of infiltrating cells, predominantly mononuclear cells and neutrophils. Increased exudation of serum proteins was also present in the skin of sensitized animals in areas of cercarial challenge. A time course of analyses revealed that mononuclear cell numbers increased significantly in the skin of vaccinated animals as early as 60 min after a challenge infection and continued to be present at a significantly higher level up to 72 hr after challenge. Peak neutrophil responses occurred in the skin at 24 hr (in multiply infected animals) and at 48 hr (in vaccinated animals) after a challenge infection. Along with the massive cellular infiltration there was an increased tissue expression of ICAM-1 and mRNA for iNOS in the skin of sensitized animals. Further analysis showed that in sensitized animals increased ICAM-1 expression was predominantly found on endothelial cells lining dermal capillaries, especially in areas around schistosomular migration and on cells that surrounded schistosomula in the dermis. In naive animals, however, a similar infection did not induce any ICAM-1 expression or iNOS production in the skin. Thus, an ICAM-1 mediated early accumulation of mononuclear cells in the skin and local production of nitric oxide may be important for the initial cutaneous inflammatory immune responses to migrating schistosomula of S. mansoni in vaccinated animals. On the contrary, in naive animals a potential parasite-induced suppression of ICAM-1 may play an important role in reducing cellular reaction in the skin and consequently help the parasite evade immune responses in the skin.

Secretion of an anti-inflammatory, immunomodulatory factor by Schistosomulae of Schistosoma mansoni.

Penetration and migration of schistosomulae of Schistosoma mansoni through the skin of mice is associated with reduced inflammatory responses especially after a moderate infection. Previous studies to identify the mechanisms by which schistosomulae of S. mansoni suppress inflammatory responses in human skin showed that the excretory/secretory (ES) products of schistosomulae of s. mansoni contain activities that induce production of the antiinflammatory cytokine IL-1ra from human keratinocytes. In the present study we have characterized the ES products of the schistosomulae of S. mansoni to identify the IL-1ra inducing activity. We demonstrate that this anti-inflammatory activity is associated with a protein of molecular mass 16.8 kDa (Sm 16.8). Depletion studies confirm that Sm 16.8 is the major IL-1ra inducing activity in the ES products. A comparison of the proteins in the ES products of schistosomulae of S. mansoni with those of Trichobilharzia ocellata, a bird schistosome that induces an acute inflammation in human skin, shows that Sm 16.8 is absent in the ES products of T. ocellata. Interestingly, ES products of the schistosomulae of T. ocellata were potent inducers of IL-1 alpha from human keratinocytes, whereas ES products from schistosomulae of s. mansoni induce little or no IL-1 alpha secretion from keratinocytes. Functional studies show that Sm 16.8 suppresses antigen induced lymphoproliferative responses in vitro. Addition of Sm 16.8 to spleen or axillary lymph node cell cultures resulted in a significant reduction in antigen induced IL-2 secretion. These studies show that schistosomulae of S. mansoni elaborate an anti-inflammatory, immunomodulatory factor that may help the parasite to evade host immune responses in the skin. Given the capabilities of Sm 16.8 to induce IL-ira and suppress lymphoproliferation, this protein may also have a potential use as a therapeutic agent for inflammatory skin disorders.

Schistosoma mansoni: fatty acid-induced cercarial tail loss does not involve eicosanoid production and chemoreceptors.

Inhibitors of eicosanoid production had no effect on linoleic acid-induced Schistosoma mansoni cercarial tail loss. In addition, linoleic acid-induced cercarial tail loss was not inhibited by silver nitrate, which binds to putative chemoreceptors for fatty acids in cercariae. There was no correlation between molecular structures of fatty acids and their potencies to induce tail loss. Furthermore, transcompounds of fatty acids which cannot be precursors of eicosanoids elicited tail loss as potently as cis-compounds did. The present results suggest that fatty acid-induced cercarial tail loss is not mediated by eicosanoid production and chemoreceptors, which are involved in cercarial penetration behavior stimulated by fatty acids.

Role of calcium ion in Schistosoma mansoni cercarial tail loss induced by unsaturated fatty acids.

Linoleate (C18: 2) and oleate (C18: 1), but not stearate (C18: 0), induced tail removal in cercariae. Linoleate stimulated tail loss more strongly than oleate did. Tail loss induced by linoleate was significantly suppressed by incubating cercariae with ethyleneglycol-bis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA). Preincubation of cercariae with EGTA for 5 min caused further inhibition of the tail loss. Calcium ionophore A23187 (A23187) increased the cercarial tail-loss rate. When A23187 was combined with linoleate at 0.03 mM, an additive effect on tail loss appeared, whereas the ionophore in combination with linoleate at 0.3 mM had no such effect. EGTA almost completely abolished cercarial tail loss induced by linoleate at both 0.03 and 0.3 mM in the presence and absence of A23187. Linoleate at 3 mM provoked cercarial tail loss even in the presence of EGTA, although the effect of oleate at 3 mM disappeared. Under these conditions, the effect of linoleate was synergistically enhanced by the combination with A23187. A similar, but not significant, synergism took place in cercariae stimulated by oleate. These findings suggest that unsaturated fatty acids enhance calcium influx into cercariae, resulting in triggering tail loss, and, furthermore, that the fatty acids have other potentiating effects on cercarial tail loss. Protein kinases play an insignificant role in fatty acid-induced cercarial tail loss, because a protein kinase C inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), and an inhibitor of various protein kinases, staurosporine, had little or no effect on cercarial tail loss induced by linoleate at 3 mM.

Penetration of Schistosoma mansoni cercariae into a living skin equivalent.

We evaluated the use of a living skin equivalent (LSE) as a suitable membrane for Schistosoma mansoni cercarial penetration. LSE is a living artificial skin composed of a dermal layer containing human dermal fibroblasts embedded in a collagen lattice and an epidermal layer consisting of differentiated human keratinocytes. The keratinocytes differentiate into a stratum corneumlike layer, whereas the dermal-epidermal junction forms a layer similar, but not identical to, the basement membrane. We exposed LSE to 50 cercariae for 0, 3, 6, 20, and 30 hr at 37 C, and the percentage of penetration was evaluated by counting cercariae remaining on the LSE surface. No cercarial penetration was observed in the first 15 min of exposure; however, penetration was detected at all other times. Maximum penetration rates were observed at 20 hr (80%). In other experiments LSE was pretreated topically with 0 or 4 micrograms/cm2 linoleic acid, then exposed to between 800 and 1,000 cercariae for 18-20 hr at 37 C. LSE pretreated with linoleate had significantly higher penetration rates than untreated membranes (81% +/- 2.51% vs. 65.9% +/- 6.97%, P = 0.03). Increasing linoleate concentrations from 10 to 40 micrograms/cm2 gradually decreased the ability of cercariae to penetrate the membrane. Some LSE membranes also were processed for light microscopy, and we present photomicrographs showing schistosomulae within the epidermal and dermal layers of the LSE. We conclude that despite the time it takes for cercariae to penetrate LSE, these membranes may allow investigators to examine, in vitro, host-parasite interactions at the level of the skin.

Schistosoma mansoni and Trichobilharzia ocellata: comparison of secreted cercarial eicosanoids.

Schistosoma mansoni cercarial transformation and early stages of penetration can be correlated to specific eicosanoid products. Cercarial eicosanoids are suggested to play immunoregulatory roles during penetration. We examined production of cercarial eicosanoids by S. mansoni compared with that of the duck parasite Trichobilharzia ocellata after incubation with linoleate. Secretions were separated by reversed-phase high pressure liquid chromatography and also quantified by radioimmunoassay. The 2 parasites, differing in their immune evasion, synthesized the same types of prostaglandins, leukotrienes, and hydroxy-eicosatetranoic acids in similar quantities. Eicosanoid fractions of both species also showed a similar inhibition of superoxide production by human neutrophils. The coincidence of eicosanoid production suggests a function of eicosanoids in processes that are similar in both species.

Cytokine and eicosanoid regulation by Schistosoma mansoniduring LSE penetration.

Cercarial penetration, in low to moderate numbers, does not cause a normal skin inflammatory response; therefore, the authors sought to determine whether cercariae can down-regulate keratinocyte activation and thus the secretion of pro-inflammatory cytokines and eicosanoids. Human living skin equivalent (LSE, Organogenesis) consisting of dermal, epidermal and stratum corneum-like layers was used as the skin substrate. The surface of the LSE membrane was exposed to 100 ng IFNgamma or ~850 cercariae for 18 h. Incubation media and tissue was then assayed for IL-1alpha, IL-6, IL-8, TNFalpha, 5-HETE, 12-HETE, PGF(2), LTB(4), and LTC(4) via RIA and Western Blots. TNFalpha was not detected. Secreted IL-1alpha levels were (mean +/- S.E.M. (n)): Control, 1.03 ng +/- 0.15 (11); IFNgamma 1.90 ng +/- 0.48 (5); cercariae, 1.79 ng +/- 0.22 (22). In spite of this increase, cercariae down-regulated IL-8 (cercariae 11.13 +/- 1.70 ng vs. IFNgamma = 16.47 +/- 0.29 ng, p = 0.04) and LTB(4) (cercariae = 98.86 +/- 19.65 pg/0.1 ml vs. IFNgamma = 193.42 +/- 44.21 pg/0.1 ml p = 0.02). No changes were seen in IL-6, 12-HETE, 5-HETE, and PGE(2) levels. It is concluded that cercarial penetration causes a release of IL-1alpha consistent with skin trauma; however, schistosomulae may regulate the production of chemotactic (neutrophils, macrophages, T-cells, etc.) and activation factors such as IL-8 and LTB(4).

Influence of a menhaden oil diet on cercarial penetration of Schistosoma mansoni.

The ability of a menhaden oil (MO) diet to influence cercarial penetration into mouse tail skin was evaluated. Male CD-1 mice 4-6 wk old (15.2 g average weight) were fed a 0, 10%, or 20% MO-supplemented diet for 2 wk. After this time mice were infected with either 65 +/- 3 or 145 +/- 3 [35S]methionine/cysteine-labeled cercariae for 1 hr by tail immersion. Twenty-four hours and 7 days later groups of mice were killed and their tail skin removed and autoradiographed. At 24 hr postinfection, mice fed a 20% MO diet had significantly higher cercarial penetration than controls and 10% MO diets (56% +/- 5.2 vs. 44% +/- 2.9, P = 0.02, 1-tailed t-test). After 7 days mice fed a 20% MO diet retained more radioactive foci than controls or 10% MO diets (21% +/- 2.0 vs. 15% +/- 1.3, P = 0.01, 1-tailed t-test).

Schistosoma mansoni: the role of calcium in the stimulation of cercarial proteinase release.

We investigated the role of calcium mobilization in the induction of proteinase release from cercarial preacetabular glands. Proteinase release was measured by the ability of cercariae to break down a 3H-labeled proline extracellular fibroblast matrix and calcium influx was measured using 45Ca2+. The role of calcium in the activation of cercarial proteinase was examined by investigating the effects of calcium addition and removal on linoleate-induced matrix degradation, the ability of various calcium modulators (Verapamil, fendiline, nifedipine, SK-525A, BAY K-8644, Ryanodine, and SK-7171A) to stimulate or inhibit linoleate-induced proteinase release, the ability of calcium modulators directly to induce cercarial proteinase release, and the ability of various stimulants of proteinase release to induce calcium influx or efflux from cercariae. The results of these studies indicate that proteinase release is dependent on external calcium concentration, voltage-operated channels are either nonexistent in cercariae or have a minimal role in overall calcium influx, and that activation of Ca2+ influx can be caused by both free fatty acids and calcium modulators by a hypothesized receptor-operated channel. Although calcium uptake is important in cercarial proteinase release, it is not the only factor involved. Calcium uptake alone does not guarantee that proteinase will be secreted. On the other hand, if Ca2+ influx does not occur, proteinase will not be secreted.

Brain synaptosomal Ca2+ uptake: comparison of Sprague-Dawley, Wistar-Kyoto and spontaneously hypertensive rats.

1. K(+)-stimulated 45Ca2+ uptake by synaptosomes was measured with respect to the strain differences between Sprague-Dawley (SD), Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). 2. 45Ca2+ uptake by synaptosomes isolated from cerebral cortex of SD, WKY and SHR was measured at 15, 30, 60, 120 and 240 sec time periods. 3. The sequence of both the magnitude and rate of resting and depolarization-dependent 45Ca2+ uptake was SHR greater than WKY greater than SD. 4. The fastest rates of resting and depolarization-dependent 45Ca2+ uptake occurred in each rat during the first 15 sec and uptake rates dropped off quickly in both resting and depolarization states. 5. At 15 sec, there were significant differences between SHR and WKY, while there were no significant differences between WKY and SD. 6. The results suggest that an important alteration in Ca2+ channel characteristics may occur in SHR brain synaptosomes.

Radiolabeling of Necator americanus third stage larvae with 75Se-methionine.

Third stage larvae of Necator americanus were radiolabeled with 75Se-methionine by two methods. Larvae labeled in aqueous cultures contained 188 and 25 cpm per sheathed and ex-sheathed larva, respectively. Larvae labeled in coproculture incorporated 25 and 18 cpm per sheathed and ex-sheathed larva, respectively. All of the label was decayed in 5 days from larvae labeled in aqueous cultures, whereas appreciable amounts of radioactivity were still detectable at day 7 of chase period in coproculture labeled larvae.

Schistosoma mansoni: experimental chemoprophylaxis in mice using oral anti-penetration agents.

The ability to prevent schistosomiasis by using an oral chemoprophylactic agent, which acts by preventing cercarial penetration, has been unexplored. We initially examined the effect of praziquantel (PZQ) as such an agent and found that it was moderately effective in blocking cercarial penetration, but that this effect was dependent on the vehicle used to administer the drug. ICR mice were given a total of 200 mg/kg PZQ per os over an 8-hr period in a divided dose of 50 mg/kg/2 hr. At time periods ranging from 0 to 92 hr after the last dose, mice were exposed to approximately 75 75Se-labeled cercariae via the tail. Twenty-four hours later, mice were sacrificed, their tails were removed and subjected to autoradiography, and the percentage of penetration was calculated. Cremophor El, 50% PEG 200, 50% propylene glycol, vegetable oil, and cod liver oil were used as PZQ vehicles. When Cremophor El (ethoxylated castor oil) was used to administer PZQ, a 93% reduction in cercarial penetration was seen at 0 hr and a 98%+ reduction rate was seen from 4 to 24 hr postexposure. However, Cremophor El alone had an essentially equivalent effect on cercarial penetration from 8 to 92 hr after administration. These unexpected results led us to investigate both castor oil and ricinoleic acid (castor oil is 87% ricinoleate as triglyceride) as oral anti-penetration agents. Mice were given the lipids orally by gavage for 7 days. On Day 8, each group of 12 mice was exposed to approximately 75 75Se-radiolabeled cercariae. Castor oil gave protection rate ranging from 90 to almost 100% at an optimal concentration of 0.3 ml/day x 3 or 7 days (approximately 9.8 g/kg/day). These observations suggest that chemoprophylaxis may be possible by dietary supplementation with lipids having anti-penetration activity or by molecules that resemble these lipids.