Stereotactic body radiotherapy for primary renal cell carcinoma: a systematic review and practice guideline from the International Society of Stereotactic Radiosurgery (ISRS).

Surgery is the standard of care for patients with primary renal cell carcinoma. Stereotactic body radiotherapy (SBRT) is a novel alternative for patients who are medically inoperable, technically high risk, or who decline surgery. Evidence for using SBRT in the primary renal cell carcinoma setting is growing, including several rigorously conducted prospective clinical trials. This systematic review was performed to assess the safety and efficacy of SBRT for primary renal cell carcinoma. Review results then formed the basis for the practice guidelines described, on behalf of the International Stereotactic Radiosurgery Society. 3972 publications were screened and 36 studies (822 patients) were included in the analysis. Median local control rate was 94·1% (range 70·0-100), 5-year progression-free survival was 80·5% (95% CI 72-92), and 5-year overall survival was 77·2% (95% CI 65-89). These practice guidelines addressed four key clinical questions. First, the optimal dose fractionation was 25-26 Gy in one fraction, or 42-48 Gy in three fractions for larger tumours. Second, routine post-treatment biopsy is not recommended as it is not predictive of patient outcome. Third, SBRT for primary renal cell carcinoma in a solitary kidney is safe and effective. Finally, guidelines for post-treatment follow-up are described, which include cross-axial imaging of the abdomen including both kidneys, adrenals, and surveillance of the chest initially every 6 months. This systematic review and practice guideline support the practice of SBRT for primary renal cell carcinoma as a safe and effective standard treatment option. Randomised trials with surgery and invasive ablative therapies are needed to further define best practice.

Advances in microfluidic in vitro systems for neurological disease modeling.

Neurological disorders are the leading cause of disability and the second largest cause of death worldwide. Despite significant research efforts, neurology remains one of the most failure-prone areas of drug development. The complexity of the human brain, boundaries to examining the brain directly in vivo, and the significant evolutionary gap between animal models and humans, all serve to hamper translational success. Recent advances in microfluidic in vitro models have provided new opportunities to study human cells with enhanced physiological relevance. The ability to precisely micro-engineer cell-scale architecture, tailoring form and function, has allowed for detailed dissection of cell biology using microphysiological systems (MPS) of varying complexities from single cell systems to "Organ-on-chip" models. Simplified neuronal networks have allowed for unique insights into neuronal transport and neurogenesis, while more complex 3D heterotypic cellular models such as neurovascular unit mimetics and "Organ-on-chip" systems have enabled new understanding of metabolic coupling and blood-brain barrier transport. These systems are now being developed beyond MPS toward disease specific micro-pathophysiological systems, moving from "Organ-on-chip" to "Disease-on-chip." This review gives an outline of current state of the art in microfluidic technologies for neurological disease research, discussing the challenges and limitations while highlighting the benefits and potential of integrating technologies. We provide examples of where such toolsets have enabled novel insights and how these technologies may empower future investigation into neurological diseases.

Structural and functional conservation of non-lumenized lymphatic endothelial cells in the mammalian leptomeninges.

The vertebrate CNS is surrounded by the meninges, a protective barrier comprised of the outer dura mater and the inner leptomeninges, which includes the arachnoid and pial layers. While the dura mater contains lymphatic vessels, no conventional lymphatics have been found within the brain or leptomeninges. However, non-lumenized cells called Brain/Mural Lymphatic Endothelial Cells or Fluorescent Granule Perithelial cells (muLECs/BLECs/FGPs) that share a developmental program and gene expression with peripheral lymphatic vessels have been described in the meninges of zebrafish. Here we identify a structurally and functionally similar cell type in the mammalian leptomeninges that we name Leptomeningeal Lymphatic Endothelial Cells (LLEC). As in zebrafish, LLECs express multiple lymphatic markers, containing very large, spherical inclusions, and develop independently from the meningeal macrophage lineage. Mouse LLECs also internalize macromolecules from the cerebrospinal fluid, including Amyloid-ß, the toxic driver of Alzheimer's disease progression. Finally, we identify morphologically similar cells co-expressing LLEC markers in human post-mortem leptomeninges. Given that LLECs share molecular, morphological, and functional characteristics with both lymphatics and macrophages, we propose they represent a novel, evolutionary conserved cell type with potential roles in homeostasis and immune organization of the meninges.

Vascular-Derived Vegfa Promotes Cortical Interneuron Migration and Proximity to the Vasculature in the Developing Forebrain.

Vascular endothelial growth factor (Vegfa) is essential for promoting the vascularization of the embryonic murine forebrain. In addition, it directly influences neural development, although its role in the forming forebrain is less well elucidated. It was recently suggested that Vegfa may influence the development of GABAergic interneurons, inhibitory cells with crucial signaling roles in cortical neuronal circuits. However, the mechanism by which it affects interneuron development remains unknown. Here we investigated the developmental processes by which Vegfa may influence cortical interneuron development by analyzing transgenic mice that ubiquitously express the Vegfa120 isoform to perturb its signaling gradient. We found that interneurons reach the dorsal cortex at mid phases of corticogenesis despite an aberrant vascular network. Instead, endothelial ablation of Vegfa alters cortical interneuron numbers, their intracortical distribution and spatial proximity to blood vessels. We show for the first time that vascular-secreted guidance factors promote early-migrating interneurons in the intact forebrain in vivo and identify a novel role for vascular-Vegfa in this process.

Robo1 modulates proliferation and neurogenesis in the developing neocortex.

The elaborate cytoarchitecture of the mammalian neocortex requires the timely production of its constituent pyramidal neurons and interneurons and their disposition in appropriate layers. Numerous chemotropic factors present in the forebrain throughout cortical development play important roles in the orchestration of these events. The Roundabout (Robo) family of receptors and their ligands, the Slit proteins, are expressed in the developing forebrain, and are known to play important roles in the generation and migration of cortical interneurons. However, few studies have investigated their function(s) in the development of pyramidal cells. Here, we observed expression of Robo1 and Slit genes (Slit1, Slit2) in cells lining the telencephalic ventricles, and found significant increases in progenitor cells (basal and apical) at embryonic day (E)12.5 and E14.5 in the developing cortex of Robo1(-/-), Slit1(-/-), and Slit1(-/-)/Slit2(-/-), but not in mice lacking the other Robo or Slit genes. Using layer-specific markers, we found that both early- and late-born pyramidal neuron populations were significantly increased in the cortices of Robo1(-/-) mice at the end of corticogenesis (E18.5). The excess number of cortical pyramidal neurons generated prenatally appears to die in early postnatal life. The observed increase in pyramidal neurons was due to prolonged proliferative activity of their progenitors and not due to changes in cell cycle events. This finding, confirmed by in utero electroporation with Robo1 short hairpin RNA (shRNA) or control constructs into progenitors along the ventricular zone as well as in dissociated cortical cell cultures, points to a novel role for Robo1 in regulating the proliferation and generation of pyramidal neurons.

Estimating The Effects Of COVID-19 On Globalized Markets For Active Pharmaceutical Ingredients.

Global supply chains for active pharmaceutical ingredients (APIs) are highly centralized in certain countries and are susceptible to supply-chain shocks. However, there is no systematic monitoring or global coordination to manage risk and ensure equitable supply continuity during public health emergencies. In this study, we applied quasi-experimental methods on shipment-level customs data to determine how prices and export volume for APIs exported from India were affected by the COVID-19 pandemic. We found that API prices for key essential medicines not used for COVID-19 did not change significantly in the year after the World Health Organization pandemic declaration, but volume decreased by 80 percent. Prices for medicines speculatively repurposed for COVID-19, such as hydroxychloroquine and ivermectin, increased by as much as 250 percent compared with prices for nonrepurposed medicines, but only ivermectin saw a decrease in volume. Systematic monitoring of API markets, investments to promote supply diversification, and legal and political reforms to disincentivize price speculation could support supply-chain resilience and safeguard access to medicines.

Estimated Sustainable Cost-Based Prices for Diabetes Medicines.

Importance: The burden of diabetes is growing worldwide. The costs associated with diabetes put substantial pressure on patients and health budgets, especially in low- and middle-income countries. The prices of diabetes medicines are a key determinant for access, yet little is known about the association between manufacturing costs and current market prices. Objectives: To estimate the cost of manufacturing insulins, sodium-glucose cotransporter 2 inhibitors (SGLT2Is), and glucagonlike peptide 1 agonists (GLP1As), derive sustainable cost-based prices (CBPs), and compare these with current market prices. Design, Setting, and Participants: In this economic evaluation, the cost of manufacturing insulins, SGLT2Is, and GLP1As was modeled. Active pharmaceutical ingredient cost per unit (weighted least-squares regression model using data from a commercial database of trade shipments, data from January 1, 2016, to March 31, 2023) was combined with costs of formulation and other operating expenses, plus a profit margin with an allowance for tax, to estimate CBPs. Cost-based prices were compared with current prices in 13 countries, collected in January 2023 from public databases. Countries were selected to provide representation of different income levels and geographic regions based on the availability of public databases. Main Outcomes and Measures: Estimated CBPs; lowest current market prices (2023 US dollars). Results: In this economic evaluation of manufacturing costs, estimated CBPs for treatment with insulin in a reusable pen device could be as low as $96 (human insulin) or $111 (insulin analogues) per year for a basal-bolus regimen, $61 per year using twice-daily injections of mixed human insulin, and $50 (human insulin) or $72 (insulin analogues) per year for a once-daily basal insulin injection (for type 2 diabetes), including the cost of injection devices and needles. Cost-based prices ranged from $1.30 to $3.45 per month for SGLT2Is (except canagliflozin: $25.00-$46.79) and from $0.75 to $72.49 per month for GLP1As. These CBPs were substantially lower than current prices in the 13 countries surveyed. Conclusions and Relevance: High prices limit access to newer diabetes medicines in many countries. The findings of this study suggest that robust generic and biosimilar competition could reduce prices to more affordable levels and enable expansion of diabetes treatment globally.

Amount of usage and involvement in explosions not associated with increased contamination of prehospital vehicles with multi-drug-resistant organisms.

INTRODUCTION: The role of explosions and patient transport vehicles as sources and vectors of Gram-negative, multidrug-resistant organisms (MDROs) that predominate infections following lengthy evacuations after disasters due to natural hazards and in current war-trauma patients is unknown. HYPOTHESIS/PROBLEM: Damaged or heavily-used vehicles could be sources of the MDROs subsequently linked to nosocomial infections. METHODS: From January through May 2008 in Iraq, inside surfaces of heavily-used, tactical vehicles (Experimental Group) were sampled with sterile, pre-moistened swabs. Swabs, along with positive and negative controls, were shipped to the reference laboratory in Washington, DC, where they underwent culture, identification and susceptibility testing, and pulsed-field gel electrophoresis. Multidrug-resistant organisms were defined according to the standard Centers for Disease Control and Prevention definitions. High risk organisms (HROs) were defined as susceptible E. coli, A. baumannii, P. aeruginosa, Enterobacter spp, or Klebsiella spp. Concurrently, new counterparts (Control Group) were similarly surveyed in a storage lot in Georgia, USA. Groups were compared using the Chi-squared test. RESULTS: One hundred thirty-nine consecutive vehicles including all available ambulances were sampled, yielding 153 swabs. Nineteen were lost or damaged during shipping. Seventy-nine swabs yielded growth of one or more Gram-negative bacteria. The amount and genotype of MDROs in heavily-used vehicles, including those involved in roadside bombings, were compared to control vehicles and to strains isolated from wounds and environmental surfaces at the base hospital. Predominant organisms included P. agglomerans (34%), S. flexneri (8%), E. vulneris (6%), Pseudomonas sp. (6%), and K. pneumonia (6%). No MDROs were isolated. Thirteen vehicles (eight of 94 experimental and five of 45 control) yielded HRO. There was no difference in contamination rates (P = .63). No HROs were isolated from ambulances. No clonal association existed between vehicle and hospital strains. CONCLUSION: Given the implications that this knowledge gap has on military and civilian prehospital reservoirs of infection, further study is warranted to confirm these findings and identify targets for preventive intervention throughout civilian disaster and military casualty evacuation chains.

Development and pilot test of a pregnancy decision making tool for women with physical disabilities.

OBJECTIVE: Design and pilot test a new decision making tool for women with physical disabilities (impairment of physical function due to chronic conditions) considering pregnancy. DATA SOURCES AND STUDY SETTING: Quantitative surveys and qualitative interviews were collected from participants living in the community. STUDY DESIGN: Clinical guidelines and survey and focus group data about pregnancy informational and decisional needs guided content development. The tool was pilot tested in a 12-week trial with participants with physical disabilities considering or actively planning a pregnancy. Feasibility outcomes were acceptability, implementation, and demand (collected at end of the trial); preliminary efficacy focused on decisional conflict and readiness (baseline, 6 weeks, and end of trial). DATA COLLECTION: Survey data were collected using an online form. One-on-one interviews were conducted to learn more about experience using the tool. PRINCIPAL FINDINGS: Thirty eight participants with mild, moderate, or severe physical disabilities participated. Feasibility outcomes indicated that the tool provided participants with information, guiding questions, and helped them to consider multiple aspects of the decision about pregnancy. Most participants responded positively to the new decision making tool, finding it easy to use and the information balanced. Feedback highlighted opportunity for improvement, such as more specific information, peer stories, and the limitations of a paper format. There was significant linear effect of time, with increased decisional certainty and readiness, values clarity, and decisional support (partial η2 [90% CI] = 0.310 [0.08, 0.46], 0.435 [0.19, 0.60], 0.134 [0, 0.29], 0.178 [0.01, 0.35], respectively). Decisional certainty and readiness had high observed power (96.7% and 99.3%, respectively) with lower observed power for clarity and support (60.6% and 75.1%, respectively). CONCLUSIONS: The new tool shows promise for supporting women with physical disabilities in navigating pregnancy decision making. Future development of complementary strategies to support health care providers will help improve shared decision making and patient-centered care.

Refined exercise testing can aid DNA-based diagnosis in muscle channelopathies.

OBJECTIVE: To improve the accuracy of genotype prediction and guide genetic testing in patients with muscle channelopathies we applied and refined specialized electrophysiological exercise test parameters. METHODS: We studied 56 genetically confirmed patients and 65 controls using needle electromyography, the long exercise test, and short exercise tests at room temperature, after cooling, and rewarming. RESULTS: Concordant amplitude-and-area decrements were more reliable than amplitude-only measurements when interpreting patterns of change during the short exercise tests. Concordant amplitude-and-area pattern I and pattern II decrements of >20% were 100% specific for paramyotonia congenita and myotonia congenita, respectively. When decrements at room temperature and after cooling were <20%, a repeat short exercise test after rewarming was useful in patients with myotonia congenita. Area measurements and rewarming distinguished true temperature sensitivity from amplitude reduction due to cold-induced slowing of muscle fiber conduction. In patients with negative short exercise tests, symptomatic eye closure myotonia predicted sodium channel myotonia over myotonia congenita. Distinctive "tornado-shaped" neuromyotonia-like discharges may be seen in patients with paramyotonia congenita. In the long exercise test, area decrements from pre-exercise baseline were more sensitive than amplitude decrements-from-maximum-compound muscle action potential (CMAP) in patients with Andersen-Tawil syndrome. Possible ethnic differences in the normative data of the long exercise test argue for the use of appropriate ethnically-matched controls. INTERPRETATION: Concordant CMAP amplitude-and-area decrements of >20% allow more reliable interpretation of the short exercise tests and aid accurate DNA-based diagnosis. In patients with negative exercise tests, specific clinical features are helpful in differentiating sodium from chloride channel myotonia. A modified algorithm is suggested.

A comparison of the pain perceived during intravenous catheter insertion after injection with various local anesthetics.

This study compared 4 local anesthetics, 1% lidocaine, 1% lidocaine with sodium bicarbonate, 2% chloroprocaine, and 0.5% bupivacaine, in a double-blinded manner for pain on intradermal injection and pain during subsequent intravenous (IV) cannulation with an 18-gauge catheter. The subjects rated their pain, using 100-mm visual analog scales, related to the local injection itself and again after the IV catheter was inserted. No statistical differences were noted in pain scores after the injection of the local anesthetic (P = . 134) or on insertion of the IV catheter itself (P = .394). However, there was a low correlation between the pain perceived during the injection of local anesthetic and insertion of the IV catheter (r = 0.483; P = .001). We found that there were no differences in pain produced by 1% lidocaine, 1% lidocaine with sodium bicarbonate, 2% chloroprocaine, and 0.5% bupivacaine during intradermal injection. There were also no differences in pain produced by an 18-gauge IV catheter being inserted after administration of any of these local anesthetics. Thus, any of these 4 local anesthetics may be used, and the choice may be based on other factors such as price and convenience.

A naturopathic treatment approach for mild and moderate COVID-19: A retrospective chart review.

OBJECTIVES: The coronavirus disease 2019 (COVID-19) pandemic has led to significant morbidity and mortality. Although COVID-19 vaccination is available, therapeutic options are still needed. The goal of the present manuscript is to report on a treatment strategy used in a naturopathic medical practice for mild and moderate COVID-19. DESIGN: A retrospective chart review was conducted of 30 consecutive patients diagnosed with mild and moderate COVID-19 who were provided multi-nutrient, herbal, and probiotic treatment in a rural, out-patient, naturopathic primary care setting. MAIN OUTCOMES MEASURES: The primary outcome was treatment safety; secondary outcomes included changes in symptoms, progression to severe COVID-19, incidence of long COVID, and recovery time. RESULTS: No side effects or adverse events were reported from treatment and all patients experienced resolution of symptoms presumed to be associated with COVID-19 infection. One patient who had been ill for 28 days prior to presentation was hospitalized. Five patients had an illness duration of more than one month. Time to treatment was correlated with duration of illness post-treatment (r = 0.63, p < 0.001) and more symptoms at presentation was correlated with a longer duration of illness (r = 0.52, p < 0.01). CONCLUSIONS: In this retrospective chart review, a multi-nutrient, herbal, and probiotic therapeutic approach for mild and moderate COVID-19 appeared to be well-tolerated. Delay in seeking treatment after symptom onset, as well as more symptoms at presentation, were correlated with a longer duration of illness. This treatment strategy may have clinical benefit, warranting prospective clinical trials with confirmed COVID-19 cases.

Development of a new pregnancy informational and decisional needs survey for women with physical disabilities.

BACKGROUND: While the literature on pregnancy and disability is growing, generating important knowledge of barriers to care and health risks, there is limited literature on pregnancy decision-making and informational needs. Such knowledge is critical for the development of interventions to mitigate the challenges women with disabilities and health care providers face in making this important decision. OBJECTIVE: /Hypothesis: Develop a survey of pregnancy decisional and informational needs of women with physical disabilities. METHODS: We developed a conceptual framework that guided item writing, defined the characteristics of the target population, engaged stakeholders with disabilities to collaborate with investigators, and tested the interpretability and relevance of items, and preferred mode of responding (online vs. telephone). A total of 123 women participated in cognitive interviews (N = 13), mode testing (N = 10), or survey data collection (N = 114). RESULTS: Instructions, three screening questions, and 156 items were tested in one round of 17 cognitive interviews; 25 items were deleted, 94 were revised, and 37 items were retained without changes. The final version of the survey included six sub-sections: the experience of making a decision; information about pregnancy and disability; things affecting a decision; knowing what is important; support for making a decision; and working with health care providers. CONCLUSIONS: The overall performance of the survey supported its content validity and utility as a useful way to gather information about the pregnancy decision-making experience and informational needs of women with physical disabilities.

In vitro activity of the aminoglycoside antibiotic arbekacin against Acinetobacter baumannii-calcoaceticus isolated from war-wounded patients at Walter Reed Army Medical Center.

We determined the in vitro MIC of arbekacin against 200 Acinetobacter isolates recovered from wounded soldiers. The median MIC was 2 microg/ml (range, 0.5 to > 64 microg/ml). A total of 97.5% of the isolates had arbekacin MICs of < 8 microg/ml and 86.5% had MICs of < or = 4 microg/ml. There was no association between the arbekacin MIC and susceptibility to 16 other antibiotics or the specimen source (P = 0.7239). Synergy testing suggested an enhanced effect of arbekacin-carbapenem combinations.

The role of Robo3 in the development of cortical interneurons.

A number of studies in recent years have shown that members of the Roundabout (Robo) receptor family, Robo1 and Robo2, play significant roles in the formation of axonal tracks in the developing forebrain and in the migration and morphological differentiation of cortical interneurons. Here, we investigated the expression and function of Robo3 in the developing cortex. We found that this receptor is strongly expressed in the preplate layer and cortical hem of the early cortex where it colocalizes with markers of Cajal-Retzius cells and interneurons. Analysis of Robo3 mutant mice at early (embryonic day [E] 13.5) and late (E18.5) stages of corticogenesis revealed no significant change in the number of interneurons, but a change in their morphology at E13.5. However, preliminary analysis on a small number of mice that lacked all 3 Robo receptors indicated a marked reduction in the number of cortical interneurons, but only a limited effect on their morphology. These observations and the results of other recent studies suggest a complex interplay between the 3 Robo receptors in regulating the number, migration and morphological differentiation of cortical interneurons.

Respiratory causes of infant mortality: progress and challenges.

A marked reduction in infant mortality due to respiratory distress syndrome (RDS) has been reported in previous studies; however, deaths due to RDS are still more common in black infants than white infants. Because advances in respiratory care may have impacted non-RDS respiratory causes of infant mortality as well, the objective of this study was to determine if specific and total non-RDS respiratory causes of infant mortality have changed over time, and if health disparities exist. We analyzed and compared infant deaths due to RDS and other respiratory diseases from 1980 to 2005 in the United States and evaluated outcomes by race and gender. Infant mortality due to non-RDS causes declined more than twofold over this time frame, but not as dramatically as the fivefold decline in RDS deaths. Black compared with white infants had twice the mortality rate due to non-RDS respiratory causes. The most common non-RDS respiratory cause of infant mortality was due to congenital malformations of the respiratory tract, which did not change dramatically over the 25 years studied.

Price of a hepatitis C cure: Cost of production and current prices for direct-acting antivirals in 50 countries.

OBJECTIVES: Seven years after the introduction of direct-acting antivirals (DAAs) for the treatment of hepatitis C, high prices remain a barrier for treatment programs worldwide. This study seeks to describe current prices for originator DAAs in 50 countries and evaluate the relationship between prices and GDP per capita. METHODS: Data on prices of sofosbuvir, daclatasvir, sofosbuvir/ledipasvir, sofosbuvir/velpatasvir, and glecaprevir/pibrentasvir were collected from national databases for 50 countries. Cost-based generic prices were estimated using an established algorithm, which accounts for costs of the active pharmaceutical ingredient (API), excipients, conversion costs of API to finished pharmaceutical product, taxes assuming manufacture in India, and a 10% profit margin. Correlation between current market prices and GDP per capita was assessed by Spearman rank-order correlation. RESULTS: Median originator prices per standard course were US$40,502 for sofosbuvir, US$26,928 for daclatasvir, US$46,812 for sofosbuvir/ledipasvir, US$34,381 for sofosbuvir/velpatasvir, and US$30,710 for glecaprevir/pibrentasvir (G/P). The estimated cost-based generic prices for a 12-week course were US$28 for sofosbuvir, US$31 for ledipasvir, US$58 for velpatasvir, US$4 for daclatasvir. For fixed-dose combinations, estimated cost-based prices were US$58 for sofosbuvir/ledipasvir, US$85 for sofosbuvir/velpatasvir, and US$31 for sofosbuvir/daclatasvir (API cost data were insufficient to calculate an estimate for G/P). Cumulative originator sales of WHO-recommended DAAs reached US$82 billion by the end of 2019. Across the 50 countries, there was no correlation between GDP per capita and DAA price, nor between estimated viraemic population and DAA price. Sub-analyses within World Bank income groups found a significant negative correlation between price and GDP per capita for all DAAs within the high-income countries group. CONCLUSIONS: Prices of DAAs vary widely across countries. The lack of correlation between DAA price and GDP per capita and viraemic population suggests that prices for DAAs are not adjusted based on country income level or potential patient population. Among high-income countries, DAA prices fall as income levels rise, possibly due to greater negotiating power of wealthier countries. DAA prices in most countries remain many times higher than estimated cost-based generic prices.

The role of Slit-Robo signaling in the generation, migration and morphological differentiation of cortical interneurons.

Cortical interneurons in rodents are generated in the ventral telencephalon and migrate tangentially into the cortex. This process requires the coordinated action of many intrinsic and extrinsic factors. Here we show that Robo1 and Robo2 receptor proteins are dynamically expressed throughout the period of corticogenesis and colocalize with interneuronal markers, suggesting that they play a role in the migration of these cells. Analysis of Robo mutants showed a marked increase in the number of interneurons in the cortices of Robo1(-/-), but not Robo2(-/-), animals throughout the period of corticogenesis and in adulthood; this excess number of interneurons was observed in all layers of the developing cortex. Using BrdU incorporation in dissociated cell cultures and phosphohistone-3 labeling in vivo, we demonstrated that the increased number of interneurons in Robo1(-/-) mice is, at least in part, due to increased proliferation. Interestingly, a similar increase in proliferation was observed in Slit1(-/-)/Slit2(-/-) mutant mice, suggesting that cell division is influenced by Slit-Robo signaling mechanisms. Morphometric analysis of migrating interneurons in Robo1(-/-), Robo2(-/-) and Slit1(-/-)/Slit2(-/-), but not in Slit1(-/-) mice, showed a differential increase in neuronal process length and branching suggesting that Slit-Robo signaling also plays an important role in the morphological differentiation of these neurons.