N-Methyl D-Aspartate Receptor Antagonist Kynurenic Acid Affects Human Cortical Development

Kynurenic acid (KYNA), a neuroactive metabolite of tryptophan degradation, acts as an endogenous N-methyl-D-aspartate receptor (NMDAR) antagonist. Elevated levels of KYNA have been observed in pregnant women after viral infections and are considered to play a role in neurodevelopmental disorders. However, the consequences of KYNA-induced NMDAR blockade in human cortical development still remain elusive. To study the potential impact of KYNA on human neurodevelopment, we used an in vitro system of multipotent cortical progenitors, i.e., radial glia cells (RGCs), enriched from human cerebral cortex at mid-gestation (16-19 gestational weeks). KYNA treatment significantly decreased RGCs proliferation and survival by antagonizing NMDAR. This alteration resulted in a reduced number of cortical progenitors and neurons while number and activation of astrocytes increased. KYNA treatment reduced differentiation of RGCs into GABAergic neurons, while differentiation into glutamatergic neurons was relatively spared. Furthermore, in mixed cortical cultures KYNA triggered an inflammatory response as evidenced by increased levels of the pro-inflammatory cytokine IL-6. In conclusion, elevated levels of KYNA play a significant role in human RGC fate determination by antagonizing NMDARs and by activating an inflammatory response. The altered cell composition observed in cell culture following exposure to elevated KYNA levels suggests a mechanism for impairment of cortical circuitry formation in the fetal brain after viral infection, as seen in neurodevelopmental disorders such as schizophrenia

The Role of N-Methyl D-Aspartate Receptors in the Development of the Human Cerebral Cortex

N-Methyl D-Aspartate receptors (NMDARs), a subtype of glutamate receptors, are important in neural development. The distribution and function of these receptors are well-studied in rodent and adult human brains, but far less is known about NMDARs in the human fetal cerebral cortex. The human cerebral cortex develops from multipotent neural progenitors called the radial glia cells (RGCs) that give rise to intermediate and interneuron progenitors, neurons, and glial cells. In my thesis, I studied the distribution of NMDAR subunits, NR1, NR2A and NR2B, in the human cerebral cortex from 10 to 24 gestational weeks (gw), a period of intense neurogenesis and synaptogenesis. Moreover, I studied the effects of kynurenic acid (KYNA), a neuroactive metabolite of tryptophan degradation that acts as an endogenous NMDAR antagonist. Elevated levels of KYNA have been observed in pregnant women after viral infections and in the cerebrospinal fluid of adult schizophrenic patients. In my thesis work, I used an in vitro system of RGCs enriched from the human cerebral cortex between 16 and 19 gw to study the potential impact of KYNA-induced NMDAR blockade in human corticogenesis. qPCR, in situ hybridization, Western blotting, and double immunolabeling experiments revealed the presence of mRNA and proteins of the NMDAR subunits in cortical progenitors and post-mitotic neurons along the telencephalic wall suggesting possible roles for NMDARs in progenitor proliferation, cell-fate determination, and neuronal differentiation. This was, in fact, observed in the in vitro study where blocking NMDARs either with D-amino phosphovalerate (D-APV) or KYNA significantly decreased survival, proliferation, specification and neuronal differentiation of RGCs, and increased the number of reactive astrocytes, and levels of the pro-inflammatory cytokine IL-6, activating the Jak-STAT signaling pathway. These results suggest a NMDAR-dependent mechanism for impairment of cortical circuitry formation in the human fetal brain

Sphincter-Preserving Therapy with Topical 2% Diltiazem for Chronic Anal Fissure: Our Experience

Background: Chronic anal fissure is a common problem across the world treated largely by surgical methods. Studies have demonstrated the efficacy of topical agents like Glyceryl Trinitrate (GTN) in anal fissure but it has been shown to have side effects like headache and dizziness. There is a need for a pharmacological therapy for fissure which has fewer side effects. Hence, this study was taken up to assess the efficacy and adverse effects of topical 2% Diltiazem (DTZ) gel. Aim & Objectives: To assess the efficacy and side effect of topical treatment with 2% DTZ gel in patient with chronic anal fissure. Material and Methods: Consecutive fifty adult patients with symptomatic chronic anal fissure attending the surgery clinic were enrolled in the study form February 2014- July 2014 and they were treated with regular topical application of 2% DTZ cream. Patients were followed up at regular intervals for symptomatic relief and healing of fissure. Results: In our study postdefecatory pain, bleeding and irritation were significantly reduced after 2week of therapy and a th primary healing rate of 86% (43 out of 50) at 6 week of therapy. The primary side-effects of 2% DTZ gel appeared to be perianal dermatitis and pruritis ani in 14% cases. Conclusion: Topical 2% DTZ gel is an effective agent in the treatment of chronic anal fissure. The need for hospital stay is abolished; psychological and financial burden on the patient is reduced. With a healing rate close to 90%, topical DTZ can be easily advised as the first line of treatment of chronic anal fissure

The Subventricular Zone: A Key Player in Human Neocortical Development

One of the main characteristics of the developing brain is that all neurons and the majority of macroglia originate first in the ventricular zone (VZ), next to the lumen of the cerebral ventricles, and later on in a secondary germinal area above the VZ, the subventricular zone (SVZ). The SVZ is a transient compartment mitotically active in humans for several gestational months. It serves as a major source of cortical projection neurons as well as an additional source of glial cells and potentially some interneuron subpopulations. The SVZ is subdivided into the smaller inner (iSVZ) and the expanded outer SVZ (oSVZ). The enlargement of the SVZ and, in particular, the emergence of the oSVZ are evolutionary adaptations that were critical to the expansion and unique cellular composition of the primate cerebral cortex. In this review, we discuss the cell types and organization of the human SVZ during the first half of the 40 weeks of gestation that comprise intrauterine development. We focus on this period as it is when the bulk of neurogenesis in the human cerebral cortex takes place. We consider how the survival and fate of SVZ cells depend on environmental influences, by analyzing the results from in vitro experiments with human cortical progenitor cells. This in vitro model is a powerful tool to better understand human neocortex formation and the etiology of neurodevelopmental disorders, which in turn will facilitate the design of targeted preventive and/or therapeutic strategies

Precision mouse models of Yars/dominant intermediate Charcot-Marie-Tooth disease type C and Sptlc1/hereditary sensory and autonomic neuropathy type 1

Animal models of neurodegenerative diseases such as inherited peripheral neuropathies sometimes accurately recreate the pathophysiology of the human disease, and sometimes accurately recreate the genetic perturbations found in patients. Ideally, models achieve both, but this is not always possible; nonetheless, such models are informative. Here we describe two animal models of inherited peripheral neuropathy: mice with a mutation in tyrosyl tRNA-synthetase, YarsE196K, modeling dominant intermediate Charcot-Marie-Tooth disease type C (diCMTC), and mice with a mutation in serine palmitoyltransferase long chain 1, Sptlc1C133W, modeling hereditary sensory and autonomic neuropathy type 1 (HSAN1). YarsE196K mice develop disease-relevant phenotypes including reduced motor performance and reduced nerve conduction velocities by 4 months of age. Peripheral motor axons are reduced in size, but there is no reduction in axon number and plasma neurofilament light chain levels are not increased. Unlike the dominant human mutations, the YarsE196K mice only show these phenotypes as homozygotes, or as compound heterozygotes with a null allele, and no phenotype is observed in E196K or null heterozygotes. The Sptlc1C133W mice carry a knockin allele and show the anticipated increase in 1-deoxysphingolipids in circulation and in a variety of tissues. They also have mild behavioral defects consistent with HSAN1, but do not show neurophysiological defects or axon loss in peripheral nerves or in the epidermis of the hind paw or tail. Thus, despite the biochemical phenotype, the Sptlc1C133W mice do not show a strong neuropathy phenotype. Surprisingly, these mice were lethal as homozygotes, but the heterozygous genotype studied corresponds to the dominant genetics seen in humans. Thus, YarsE196K homozygous mice have a relevant phenotype, but imprecisely reproduce the human genetics, whereas the Sptlc1C133W mice precisely reproduce the human genetics, but do not recreate the disease phenotype. Despite these shortcomings, both models are informative and will be useful for future research

Surgical site infection rates in six cities of India: findings of the International Nosocomial Infection Control Consortium (INICC)

Surgical site infections are a threat to patient safety. However, in India, data on their rates stratified by surgical procedure are not available. From January 2005 to December 2011, the International Nosocomial Infection Control Consortium (INICC) conducted a cohort prospective surveillance study on surgical site infections in 10 hospitals in 6 Indian cities. CDC National Healthcare Safety Network (CDC-NHSN) methods were applied and surgical procedures were classified into 11 types, according to the ninth edition of the International Classification of Diseases. We documented 1189 surgical site infections, associated with 28 340 surgical procedures (4.2%; 95% CI: 4.0-4.4). Surgical site infections rates were compared with INICC and CDC-NHSN reports, respectively: 4.3% for coronary bypass with chest and donor incision (4.5% vs 2.9%); 8.3% for breast surgery (1.7% vs 2.3%); 6.5% for cardiac surgery (5.6% vs 1.3%); 6.0% for exploratory abdominal surgery (4.1% vs 2.0%), among others. In most types of surgical procedures, surgical site infections rates were higher than those reported by the CDC-NHSN, but similar to INICC. This study is an important advancement towards the knowledge of surgical site infections epidemiology in the participating Indian hospitals that will allow us to introduce targeted interventions