Inhaled benzo(a)pyrene impairs long-term potentiation in the F1 generation rat dentate gyrus

The purpose of this study is to provide a point of reference regarding the neurotoxic effects resulting from exposure to environmental contaminants. Benzo(a)pyrene is a member of the polycyclic aromatic hydrocarbon (PAH) family and it is a by-product of combustion processes. Thus, persons living near factories or hazardous waste sites face the danger of exposure through contact with contaminated air, water and soil. In an effort to understand the impact of environmental contaminants, we have investigated the effects of gestational B(a)P aerosol exposure on long-term potentiation (LTP), a cellular correlate of learning and memory in the F1 generation. Briefly, timed-pregnant rats were exposed to B(a)P via nose-only inhalation on gestation days 11-21 for 4 hr per day. Dams were maintained to term and pups were weaned on postnatal day 30. Subsequent electrophysiological studies during postnatal days 60-70 revealed a diminution in LTP across the perforant path-granular cells synapses in the hippocampus of F1 generation animals that were transplacentally exposed to B(a)P aerosol relative to unexposed controls. Additionally, NMDA receptor subunit 1 (NR1) protein was found to be downregulated in the hippocampus of B(a)P exposed F1 generation animals. Taken together, our results suggest that gestational exposure to B(a)P aerosol attenuates the capacity for LTP in the F1 generation.

Maternal and Infant Services: examination of access in a culturally diverse community

OBJECTIVES

The aim of this study was to evaluate access of resident immigrant families from a non-English speaking background to Maternal and Infant Services operated by Community Health Services in south-western Sydney.

METHODS

An ecological study compared the demographic characteristics of mothers with an infant aged less than 12 months in three separate data collections. These were a 3-month Community-based Health Services Census, the 1996 Midwives Data Collection and the ABS 1996 Census of Population and Housing.

RESULTS

Information was collected from 2048 infants and their families who were newly registered with Maternal and Infant Services. Approximately 75% of newborn infants were registered with services. Women who were born in a non-English-speaking country were over-represented in the data. For both overseas and Australian-born women those who left school aged less than 17 years were under-represented compared with analysis of the related data systems.

CONCLUSIONS

The data suggest that migrant women from non-English-speaking backgrounds are accessing Maternal and Infant Services. However, innovative approaches for service delivery are indicated for women who may be considered socially disadvantaged, irrespective of their ethnic or cultural backgrounds.

RabD, a Dictyostelium Rab14-related GTPase, regulates phagocytosis and homotypic phagosome and lysosome fusion

RabD, a Dictyostelium Rab14-related GTPase, localizes in the endo-lysosomal pathway and contractile vacuole system of membranes. Cell lines expressing dominant-negative RabD were defective in endocytosis, endosomal membrane flow and homotypic lysosome fusion. In support of a role for RabD in fusion, cells overexpressing constitutively active RabD(Q67L) accumulated enlarged hydrolase-rich acidic vesicles ringed with GFP-RabD, consistent with RabD directly regulating lysosome fusion. To determine whether RabD also regulated phagocytosis and/or homotypic phagosome fusion (a process stimulated by many intracellular pathogens), cells overexpressing dominant-active (RabD(Q67L)) or dominant-negative (Rab(N121I)) RabD were analyzed microscopically and biochemically. The rate of phagocytosis was increased two-fold in RabD(Q67L)-expressing cells and reduced by 50% in RabD(N121I)-expressing cells compared with control cells. To examine the role of RabD in the formation of multiparticle phagosomes, we performed a series of pulse-chase experiments using fluorescently labeled bacteria and fluorescent latex beads. The rate of fusion of newly formed phagosomes was five times higher in the RabD(Q67L)-expressing cells and reduced by over 50% in RabD(N121I)-expressing cells as compared with control cells. GFP-RabD(Q67L) was found to ring multiparticle spacious phagosomes, which supports a direct role for this protein in regulating fusion. Inhibition of PI 3-kinase activity, which is known to regulate phagosome fusion in the wild-type cells, reduced the rate of phagosome fusion in RabD(Q67L+) cells, indicating that RabD acted upstream of or parallel with PI 3-kinase. We hypothesize that RabD and, possibly, Rab14, a related GTPase that associates with phagosomes in mammalian cells, are important regulators of homotypic phagosome and endo-lysosome fusion.

Do divisions of general practice have a role in and the capacity to tackle health inequalities?

BACKGROUND

General practitioners are concerned with improving the health of the community, and Divisions are an important structure through which this can be achieved. Any focus on health outcomes needs to consider what general practice and Divisions can do to reduce inequalities in health outcomes.

METHOD

We analysed 2000-2002 strategic and business plans from 78% of Divisions in NSW and Victoria, to see how Divisions were developing capacity to address health inequalities in the community through appropriate needs assessments, allocation of resources and partnership approaches.

RESULTS

Thirty percent of Divisions discussed socioeconomic barriers to people accessing health care within their community. None used equity as a needs priority. Thirty percent specifically committed resources through programs for disadvantaged groups. Thirty-six percent used partnership approaches to improve access, although only 11% used a broad advocacy role.

DISCUSSIONS

Divisions see socioeconomic disadvantage as an important issue, and some are developing significant multilevel strategies to address them, although significant gaps exist in the capacity of Divisions to undertake this work.

Hydro-environmental modelling for bathing water compliance of an estuarine basin

In recent years, considerable investment has been committed to sewerage infrastructure and new sewage treatment plants in the catchment surrounding an estuarine basin along the north-west coast of England. Although this capital investment has resulted in a marked reduction in the input of bacterial loads, relatively high counts of faecal indicator organisms are still being encountered in the coastal receiving waters, and the local bathing waters continue to fail on occasions to comply with the European Community (EC) Bathing Water Directive (1976) mandatory standards. Details are given herein of a comprehensive modelling study aimed at quantifying the impact of various bacterial inputs into the estuary and surrounding coastal waters on the bathing water quality. The model domain includes the coastal area and the entire estuary (namely the Ribble) up to the tidal limits of its tributaries. Faecal coliforms have been used as the main water quality indicator organisms. The numerical model developed for this study combines a depth integrated two-dimensional coastal model and a cross-sectionally integrated one-dimensional river model, and is capable of predicting water surface elevations, velocity fields and faecal coliform concentration distributions across the entire model domain. The hydrodynamic model was calibrated using water level and velocity measurements from three surveys and then validated against measured data from three other surveys. In order to predict the faecal coliform concentration distributions, variable faecal coliform decay rates were used, i.e. different values of decay rates were applied to the coastal and riverine waters, for day- and nighttime, and for wet and dry weather conditions. The maximum and minimum decay rates used were 2.32/day and 0.71/day for the dry and wet weather surveys, respectively. The model was then applied to (i) assess the impact of previous discharge strategies and investigate the effectiveness of future capital investment works and (ii) predict the impact of a range of strategic options, including: the effects of adding UV treatment, constructing storm water storage tanks and incorporating various combined sewer overflow (CSO) discharge scenarios for different weather conditions.

Burkitt's lymphoma: single-centre experience with modified BFM protocol

Burkitt's lymphoma is a rare aggressive lymphoma, which responds poorly to standard chemotherapy regimens used to treat high-grade non-Hodgkin's lymphoma (NHL). The use of intensive chemotherapy protocols using alkylating agents and intensive CNS prophylaxis has dramatically altered prognosis. We have treated eight patients with Burkitt's lymphoma with a modified BFM protocol. The dose of methotrexate was reduced from 5 g/m2 to 1.5 g/m2 with the aim of reducing toxicity. Seven patients received a total of six cycles of chemotherapy each and one patient received five cycles of chemotherapy. Each cycle included high-dose methotrexate, an alkylating agent (ifosphamide or cyclophosphamide) and two triple intrathecal injections of chemotherapy. Two patients with bulky abdominal disease in addition received an autologous stem cell transplant. The regimen was well tolerated with minimal toxicity. At a median follow-up of 16 months (range 10-28), six of the eight patients (75%) were alive and in complete remission. Two patients relapsed, one 24 months post-BFM chemotherapy and the other 1-month post-autologous stem cell transplantation and 2 months post-BFM chemotherapy.

Dictyostelium LvsB mutants model the lysosomal defects associated with Chediak-Higashi syndrome

Chediak-Higashi syndrome is a genetic disorder caused by mutations in a gene encoding a protein named LYST in humans ("lysosomal trafficking regulator") or Beige in mice. A prominent feature of this disease is the accumulation of enlarged lysosome-related granules in a variety of cells. The genome of Dictyostelium discoideum contains six genes encoding proteins that are related to LYST/Beige in amino acid sequence, and disruption of one of these genes, lvsA (large volume sphere), results in profound defects in cytokinesis. To better understand the function of this family of proteins in membrane trafficking, we have analyzed mutants disrupted in lvsA, lvsB, lvsC, lvsD, lvsE, and lvsF. Of all these, only lvsA and lvsB mutants displayed interesting phenotypes in our assays. lvsA-null cells exhibited defects in phagocytosis and contained abnormal looking contractile vacuole membranes. Loss of LvsB, the Dictyostelium protein most similar to LYST/Beige, resulted in the formation of enlarged vesicles that by multiple criteria appeared to be acidic lysosomes. The rates of endocytosis, phagocytosis, and fluid phase exocytosis were normal in lvsB-null cells. Also, the rates of processing and the efficiency of targeting of lysosomal alpha-mannosidase were normal, although lvsB mutants inefficiently retained alpha-mannosidase, as well as two other lysosomal cysteine proteinases. Finally, results of pulse-chase experiments indicated that an increase in fusion rates accounted for the enlarged lysosomes in lvsB-null cells, suggesting that LvsB acts as a negative regulator of fusion. Our results support the notion that LvsB/LYST/Beige function in a similar manner to regulate lysosome biogenesis.

Gynaecomastia with hypergonadotrophic hypogonadism and Leydig cell insufficiency in recipients of high-dose chemotherapy or chemo-radiotherapy

Late side-effects of stem cell transplantation include hypogonadism with infertility and sexual dysfunction, but gynaecomastia is less well recognised. We report five cases of gynaecomastia with features of hypergonadotrophic hypogonadism (primary testicular failure), who received either a TBI/cyclophosphamide conditioned allograft (n = 3) or a BEAM autograft (n = 2). Patients receiving an allograft had gynaecomastia, Leydig cell insufficiency (LCI) diminished libido and erectile dysfunction. Surgery was required in one case, while in two cases the gynaecomastia resolved spontaneously after 6 months. Two patients also had gynaecomastia and sexual dysfunction, severe hypogonadism, very low testosterone levels and marked hyperprolactinaemia following autoBMT. Both responded well to testosterone replacement therapy (TRT). As a group, all patients had primary testicular failure and all except one, had LCI (compensated or frank). However, there was no correlation between the severity of gynaecomastia and the degree of endocrine dysfunction. This preliminary study is the first to suggest that gynaecomastia, due to primary hypogonadism and LCI, may be a significant complication of myeloablative conditioning therapy. Therefore gynaecomastia in BMT recipients must always be treated as a pathological entity as it may be the external manifestation of a complex endocrine pathology. It is a potentially treatable condition. Although spontaneously reversible, some patients may require TRT or even surgery. We recommend comprehensive endocrine testing in conjunction with a reproductive endocrinologist and prompt intervention to alleviate embarrassment and anxiety in afflicted BMT recipients.

Interferon inhibits dengue virus infection by preventing translation of viral RNA through a PKR-independent mechanism

Previously, we demonstrated that pretreatment of cells with interferon (IFN) alpha + gamma or beta + gamma inhibited dengue virus (DV) replication. In this study, experiments were performed to better define the mechanism by which IFN blocks the accumulation of dengue virus (DV) RNA. Pretreatment of human hepatoma cells with IFN beta + gamma did not significantly alter virus attachment, viral entry, or nucleocapsid penetration into the cytoplasm. The inhibitory effect of IFN was retained even when naked DV RNA was transfected directly into cells, confirming that steps associated with viral entry were not the primary target of IFN action. Biosynthetic labeling experiments revealed that IFN abolished the translation of infectious viral RNA that occurred prior to RNA replication. Subcellular fractionation experiments demonstrated that IFN did not significantly alter the ability of viral RNA to attach to ribosomes. The antiviral effect of IFN appeared independent of the IFN-induced, double-stranded RNA-activated protein kinase (PKR) and RNase L, as genetically deficient PKR- RNase L- cells that were infected by DV retained sensitivity to inhibition by IFN. We conclude that IFN prevents DV infection by inhibiting translation of the infectious viral RNA through a novel, PKR-independent mechanism.

Long-term results of local recurrence after breast conservation treatment for invasive breast cancer

PURPOSE

The outcome for women with a local failure after breast conservation treatment is not well described in the literature. Because local recurrence is a potentially salvageable event, this study was performed to evaluate the outcome of patients with local recurrence after breast conservation surgery and definitive radiation treatment.

METHODS AND MATERIALS

The study population consisted of 112 patients with ipsilateral breast tumor recurrence. There were 100 isolated local recurrences and 12 local-plus-regional recurrences. There were 93 invasive local recurrences and 19 DCIS (ductal carcinoma in situ) local recurrences. Local recurrences were detected by physical examination alone in 42 patients, mammography alone in 47 patients, and both modalities in 23 patients. All patients were initially treated with breast conservation treatment with or without systemic therapy and subsequently treated at the time of local recurrence with salvage mastectomy with or without systemic therapy. The mean and median follow-up times after local recurrence were 49 and 44 months, respectively.

RESULTS

For the entire group of 112 patients, the overall survival at 10 years after local recurrence was 69%, the cause-specific survival was 71%, and the freedom from distant metastases was 47%. For the 93 patients with an invasive local recurrence, the overall survival at 10 years was 64%, cause-specific survival was 67%, and freedom from distant metastases was 44%. For the 93 patients with an invasive local recurrence, interval from diagnosis to local recurrence (< or =2 years vs. 2.1-5 years vs. >5 years) predicted for overall survival at 5 years (65% vs. 84% vs. 89%; p = 0.03). Method of detection of local recurrence (physical examination vs. mammography vs. both methods) also predicted for 5-year overall survival (73% vs. 91% vs. 93%, respectively; p = 0.04). On multivariable analysis, interval from diagnosis to local recurrence was an independent predictor of overall survival (p = 0.03). Method of detection of local recurrence (physical examination vs. mammography vs. both methods) was borderline in predicting for 5-year cause-specific survival (73% vs. 91% vs. 93%, respectively; p = 0.06). Similarly, interval from diagnosis to local recurrence (< or =2 years vs. 2.1-5 years vs. >5 years) was a borderline predictor of 5-year cause-specific survival (65% vs. 84% vs. 89%; p = 0.08). No factors that predicted for freedom from distant metastases were identified. There were three second locoregional failures on the chest wall. Two of the 19 patients with a DCIS local recurrence have died of metastatic breast cancer. Death was probably not related to their local recurrence, but rather a result of persistent risk from an invasive primary cancer.

CONCLUSIONS

This analysis provides long-term data after salvage treatment for patients who experience local recurrence after breast conservation treatment. The variables of method of detection and interval from diagnosis to local recurrence are identified as having prognostic significance for overall and cause-specific survival. In view of the potential for long-term survival, aggressive attempt at salvage treatment is warranted for the patient with local recurrence after breast conservation treatment. Second local recurrence after salvage mastectomy is an uncommon event. Although DCIS local recurrences may not in themselves cause an increase in the risk of mortality, the risk from the primary invasive cancer persists.

Rab11-like GTPase associates with and regulates the structure and function of the contractile vacuole system in Dictyostelium

Screening of a cDNA library revealed the existence of a Dictyostelium cDNA encoding a protein 80% identical at the amino acid level to mammalian Rab11. Subcellular fractionation and immunofluorescence studies revealed that DdRab11 was exclusively associated with the ATPase proton pump-rich contractile vacuole membrane system, consisting of a reticular network and bladder-like vacuoles. Video microscopy of cells expressing GFP-DdRab11 revealed that this Rab was associated with contractile vacuolar bladders undergoing formation, fusion and expulsion of water. The association of DdRab11 with contractile vacuole membranes was disrupted when cells were exposed to either hypo-osmotic conditions or an inhibitor of the ATPase proton pump. Cells that overexpressed a dominant negative form of DdRab11 were analyzed biochemically and microscopically to measure changes in the structure and function of the contractile vacuole system. Compared with wild-type cells, the dominant negative DdRab11-expressing cells contained a more extensive contractile vacuole network and abnormally enlarged contractile vacuole bladders, most likely the result of defects in membrane trafficking. In addition, the mutant cells enlarged, detached from surfaces and contained large vacuoles when exposed to water, suggesting a functional defect in osmotic regulation. No changes were observed in mutant cells in the rate of fluid phase internalization or release, suggesting the DdRab11-mediated membrane trafficking defects were not general in nature. Surprisingly, the rate of phagocytosis was increased in the dominant negative DdRab11-expressing cells when compared with control cells. Our results are consistent with a role for DdRab11 in regulating membrane traffic to maintain the normal morphology and function of the contractile vacuole.

Historical assessment of nutrition studies using only African-American study subjects: gender, socioeconomic status, and geographic location

While the African-American community has disproportionate rates of morbidity and mortality from chronic diet-related diseases, few studies have examined demographically the spectrum of these outcomes in the population. The purpose of this study is to determine the extent to which published scientific literature has examined African-American samples with sufficient specificity to identify nutrition problems in subsets of the population. Age, gender, socioeconomic status, geographic location, and sample size are used to examine study questions. In addition, the United States Department of Agriculture (USDA) Continuing Survey of Food Intakes for Individuals (CSFII) 1994-1996 is used to illustrate how evaluating nutrient variables by demographic indicators provides insights into the heterogeneity of nutrient intake patterns among African Americans. Relative to the adequacy of scientific investigation into these issues, a review of twenty-nine studies conducted from 1970 to the present demonstrates bias in gender, income, and sample size for African-Americans-only dietary research samples. Relative to identifying dietary patterns that do not meet US dietary guidelines, pervasive patterns that persist across income groups were found, indicating the need for nutrition education programs at all levels. Although there are science based diet information available, it does not seem to have reached the African-American community in numbers sufficient to be reflected in dietary changes as reported by surveys. This research demonstrates the need for detailed studies highlighting these issues, as well as the production of culturally appropriate nutrition education materials and methods that will be effective in reaching this population.

The WASp-like protein Scar regulates macropinocytosis, phagocytosis and endosomal membrane flow in Dictyostelium

Scar, a member of the WASp protein family, was discovered in Dictyostelium discoideum during a genetic screen for second-site mutations that suppressed a developmental defect. Disruption of the scar gene reduced the levels of cellular F-actin by 50%. To investigate the role of Scar in endocytosis, phagocytosis and endocytic membrane trafficking, processes that depend on actin polymerization, we have analyzed a Dictyostelium cell line that is genetically null for Scar. Rates of fluid phase macropinocytosis and phagocytosis are significantly reduced in the scar- cell-line. In addition, exocytosis of fluid phase is delayed in these cells and movement of fluid phase from lysosomes to post-lysosomes is also delayed. Inhibition of actin polymerization with cytochalasin A resulted in similar phenotypes, suggesting that Scar-mediated polymerization of the actin cytoskeleton was important in the regulation of these processes. Supporting this conclusion, fluorescence microscopy revealed that some endo-lysosomes were ringed with F-actin in control cells but no F-actin was detected associated with endo-lysosomes in Scar null cells. Disruption of the two genes encoding the actin monomer sequestering protein profilin in wild-type cells causes defects in the rate of pinocytosis and fluid phase efflux. Consistent with a predicted physical interaction between Scar and profilin, disrupting the scar gene in the profilin null background results in greater decreases in the rate of fluid phase internalization and fluid phase release compared to either mutant alone. Taken together, these data support a model in which Scar and profilin functionally interact to regulate internalization of fluid and particles and later steps in the endosomal pathway, probably through regulation of actin cytoskeleton polymerization.

Clinical, epidemiologic, and virologic features of dengue in the 1998 epidemic in Nicaragua

From July to December 1998, a hospital- and health center-based surveillance system for dengue was established at selected sites in Nicaragua to better define the epidemiology of this disease. Demographic and clinical information as well as clinical laboratory results were obtained, and virus isolation, reverse transcriptase-polymerase chain reaction, and serologic assays were performed. World Health Organization criteria were used to classify disease severity; however, a number of patients presented with signs of shock in the absence of thrombocytopenia or hemoconcentration. Therefore, a new category was designated as "dengue with signs associated with shock" (DSAS). Of 1,027 patients enrolled in the study, 614 (60%) were laboratory-confirmed as positive cases; of these, 268 (44%) were classified as dengue fever (DF); 267 (43%) as DF with hemorrhagic manifestations (DFHem); 40 (7%) as dengue hemorrhagic fever (DHF); 20 (3%) as dengue shock syndrome (DSS); and 17 (3%) as DSAS. Interestingly, secondary infection was not significantly correlated with DHF/DSS, in contrast to previous studies in Southeast Asia. DEN-3 was responsible for the majority of cases, with a minority due to DEN-2; both serotypes contributed to severe disease. As evidenced by the analysis of this epidemic, the epidemiology of dengue can differ according to geographic region and viral serotype.

Monoclonal light chain--mesangial cell interactions: early signaling events and subsequent pathologic effects

Glomerulopathic monoclonal light chains (G-LC) interact with mesangial cells (MC), resulting in alterations of mesangial homeostasis. Early signaling events control mitogenic activities and cytokine production, which in turn participate in the subsequent pathologic events. Mesangial homeostasis is affected in two very different ways, depending on whether the G-LC is from a patient with light chain deposition disease (LCDD) or light chain-related amyloidosis (AL-Am). In contrast, tubulopathic (T)-LC chains from patients with myeloma cast nephropathy do not significantly interact with MC and result in no alterations in mesangial homeostasis. Therefore, understanding early events in the monoclonal LC-MC interactions is fundamental. MC in culture were exposed to LC obtained and purified from the urine of patients with plasma cell dyscrasias and biopsy-proven renal disease, including LCDD, AL-Am, and myeloma cast nephropathy. Incubation of MC with G-LC, but not T-LC, resulted in cytoskeletal and cell shape changes, activation of platelet-derived growth factor-beta (PDGF-beta) and its corresponding receptor, cytoplasmic to nuclear migration of c-fos and NF-kappa beta signals, and production of monocyte chemoattractant protein-1 (MCP-1), as well as increased expression of Ki-67, a proliferation marker. Although NF-kappa beta activation was directly related to MCP-1 production, c-fos activation regulated proliferative signals and cytoskeletal changes in MC. Amyloidogenic LC were avidly internalized by the MC, whereas LCDD-LC effector targets were located at the MC surface. These cellular events are likely initiated as a result of interactions of the G-LC with yet-uncharacterized MC surface receptors. Dissecting the events taking place when G-LC interact with MC may define potential important targets for selective therapeutic manipulation to ameliorate or prevent the glomerular injury that ensues.

Nested restriction site-specific PCR to detect and type hepatitis C virus (HCV): a rapid method to distinguish HCV subtype 1b from other genotypes

Genotypic differentiation of hepatitis C virus (HCV) has become an integral part of clinical management and epidemiologic studies of hepatitis C infections. Thus, it is extremely important in areas such as the Czech Republic, where current instrumentation and kits for assessing HCV infection are too costly for widespread use. We describe a new and relatively inexpensive method called nested restriction site-specific PCR (RSS-PCR) that generates a "fingerprint" pattern to represent an HCV genotype without the use of restriction endonucleases and that specifically differentiates HCV genotype 1b from the other HCV genotypes. The RSS-PCR method was applied directly to serum samples from patients with hepatitis C from the Czech Republic and from patients with known HCV genotypes from the United States. The method was validated by comparison of the subtype determined by RSS-PCR to the subtype determined from analysis of the 5' noncoding region (NC) or the nonstructural protein gene (NS5b) nucleotide sequence of HCV in these clinical samples. From 75 Czech samples containing HCV RNA, three distinct RSS-PCR patterns were observed; 54 were predicted to contain subtype 1b, 19 were predicted to contain subtype 1a, and 2 were predicted to contain subtype 3a. Among 54 samples predicted to contain HCV genotype 1b, all were confirmed by their 5' NC or NS5b sequences to be subtype 1b. Thus, both the sensitivity and specificity of the RSS-PCR test for the differentiation of HCV subtype 1b from the others were 100%. While the assay described here was designed to specifically differentiate HCV subtype 1b from the other HCV genotypes, the RSS-PCR method can be modified to differentiate any HCV genotype or subtype of interest. Its simplicity and speed may provide new opportunities to study the epidemiology of HCV infections and the relationship between HCV genotypes and clinical outcome by more laboratories throughout the world.

Propagation of synchronous epileptiform events from subiculum backward into area CA1 of rat brain slices

The hippocampal trisynaptic pathway is comprised of superficial entorhinal afferents (part of the perforant path) to dentate granule cells, dentate mossy fiber inputs to CA3 pyramidal neurons, and CA3 cell projections to CA1 pyramidal neurons. This CA1 output is among others to the subiculum, and both CA1 and subiculum project to the entorhinal cortex to close the loop. Smaller circuits involving fewer hippocampal and parahippocampal regions have also been described. We present morphological and electrophysiological evidence from rat brain slices for a projection from subiculum back into area CA1. Axons of neurobiotin-labeled subicular pyramidal neurons were visualized in the apical dendritic region of CA1. Spontaneous activity in isolated subiculum--CA1 slices was produced by bathing slices in reduced magnesium media. Events in CA1 always followed events in proximal subiculum. Disruption of this subiculum--CA1 circuit with a radially oriented knife cut in the apical dendritic region between subiculum and CA1 eliminated afterdischarges in subicular and CA1 events, but did not de-synchronize the two regions. Full transections between CA1 and subiculum were necessary to functionally isolate the two regions. Only subiculum remained spontaneously active. We conclude that a subiculum--CA1 circuit supports afterdischarges in both regions and synchronizes their activity. This circuit may serve to maintain a level of depolarization in subicular and CA1 pyramidal neurons well beyond the duration of excitatory synaptic potentials resulting from activation of the trisynaptic circuitry.