Isolated Schwannoma of the Olfactory Groove: A Case Report

Introduction Schwannoma of the olfactory groove is an extremely rare tumor that can share a differential diagnosis with meningioma or neuroblastoma. Objectives The authors present a case of giant schwannoma involving the anterior cranial fossa and ethmoid sinuses. Case Report The patient presented with a 30-month history of left nasal obstruction, anosmia, and sporadic ipsilateral bleeding. Computed tomography of the paranasal sinuses revealed expansive lesion on the left nasal cavity extending to nasopharynx up to ethmoid and sphenoid sinuses bilaterally with intraorbital and parasellar extension to the skull base. Magnetic resonance imaging scan confirmed the expansive tumor without dural penetration. Biopsy revealed no evidence of malignancy and probable neural cell. Bifrontal craniotomy was performed combined with lateral rhinotomy (Weber-Ferguson approach), and the lesion was totally removed. The tumor measured 8.0 4.3 3.7 cm and microscopically appeared as a schwannoma composed of interwoven bundles of elongated cells (Antoni A regions)mixed with less cellular regions (Antoni B). Immunohistochemical study stained intensively for vimentin and S-100. Conclusion Schwannomas of the olfactory groove are extremely rare, and the findings of origin of this tumor is still uncertain but recent studies point most probably to the meningeal branches of trigeminal nerve or anterior ethmoidal nerves. .

Antimalarial drugs disrupt ion homeostasis in malarial parasites

Plasmodium chabaudi malaria parasite organelles are major elements for ion homeostasis and cellular signaling and also target for antimalarial drugs. By using confocal imaging of intraerythrocytic parasites we demonstrated that the dye acridine orange (AO) is accumulated into P. chabaudi subcellular compartments. The AO could be released from the parasite organelles by collapsing the pH gradient with the K+/H+ ionophore nigericin (20 µM), or by inhibiting the H+-pump with bafilomycin (4 µM). Similarly, in isolated parasites loaded with calcium indicator Fluo 3-AM, bafilomycin caused calcium mobilization of the acidic calcium pool that could also be release with nigericin. Interestingly after complete release of the acidic compartments, addition of thapsigargin at 10 µM was still effective in releasing parasite intracellular calcium stores in parasites at trophozoite stage. The addition of antimalarial drugs chloroquine and artemisinin resulted in AO release from acidic compartments and also affected maintenance of calcium in ER store by using different drug concentrations.

Five subtypes of muscarinic receptors are expressed in gastric smooth muscles of guinea pig

Muscarinic receptors play key roles in the control of gastrointestinal smooth muscle activity. However, specific physiological functions of each subtype remain to be determined. In this study, the nonselective cation channel activated by carbachol (ICCh) was examined in circular smooth muscle cells of the guinea pig gastric antrum using patch-clamp technique. 4-DAMP inhibited ICCh dose- dependently with IC50 of 1.1 +/- 0.1 nM (n = 6). GTPgS- induced current, however, was not inhibited by 10 nM 4-DAMP. ICCh was not recorded in pertussis- toxin (PTX)-pretreated smooth muscle cells of gastric antrum. ICCh values in response to 10 mM CCh at a holding potential of 60 mV were -330 32 pA (n=4) and -15 +/- 3 pA (n = 6) in the control and PTX-treated cells, respectively (P<0.01). Sensitivities to nanomolar 4-DAMP and PTX suggest the possible involvement of m4 subtype. Using sequence information obtained from cloned guinea pig muscarinic receptor genes, it is possible to amplify the cDNAs encoding m1-m5 from guinea pig brain tissue. Single cell RT-PCR experiments showed that all five subtypes of muscarinic receptor were present in circular smooth muscle cells of the guinea pig gastric antrum. Together with our previous results showing that Go protein is important for activation of ACh-activated NSC channels, our results suggest that ICCh might be activated by acetylcholine through m4 subtype as well as m2 and m3 subtypes in guinea-pig stomach.

A perspective of smooth muscle contractility through actions of vanadium compounds.

Smooth muscle contraction has a characteristic step-response with successive additions of stimulating compounds, and instant reversal on withdrawing the stimulus, indicative of an equilibrium situation wherein continuous, rapid reactions are occurring. Vanadium compounds, ortho- and meta-vanadates, decavanadate and peroxovanadate, were found to contract a variety of smooth muscles. Their actions were analyzed with respect to activation of receptors, increase in the intracellular calcium concentration, and increase in calmodulin-dependent myosin light chain phosphorylation leading to contraction. A new perspective of smooth muscle contractility has emerged from the studies with vanadium compounds suggesting control mechanisms involving phosphorylation for contraction and redox for relaxation.

Noncompetitive inhibitors of the acetylcholine receptor help paint a picture of its ion channel

This review describes and analyzes the evidence from studies using noncompetitive inhibitors of the nicotinic acetylcholine receptor that the receptor's ion channel is formed by the second transmembrane segment of all five receptor subunits. Inconsistencies in this generally accepted model are also presented and discussed

Ca2+-Agonistic effects of diazepam, A benzodiazepine 1-4 derivative, on isolated mouse and guinea pig left atria

1.) En solución usual de Krebs, el diazepam (1.75X10-4M) aumentó la duración del potencial de acción en una forma revesible y produjo un efecto inotrópico positivo en músculo auricular del ratón (4). 2.) Estudios adicionales sobre la acción del diazepam en la actividad mecánica y eléctrica del músculo auricular izquierdo del ratón y del cobayo, en preparaciones estimuladas electricamente, mostraron que el diazepam induce un aumento en la duración del potencial de acción medida en el 20% de la repolarización, una disminución en la velocidad de despolarización de la espiga, y modifica la velocidad de conducción del potencial de acción. 3.) El diazepam dió lugar en preparaciones con actividad espontánea, a efectos cronotrópico e inotrópico positivos, y a efecto inotrópico positivo en preparaciones estimuladas eléctricamente. 4.) El cambio en la duración del potencial de acción inducido por el diazepam en las preparaciones del ratón, fue mayor que en las preparaciones de cobayo, ca.X3. 5.) Estos hallazgos apoyan que la acción del diazepam puede deberse a un aumento en la corriente entrante de calcio y a una disminución en la corriente entrante de sodio

Effects of Vanadate on Cellular Ca2+ Movements in Guinea Pig Papillary Muscles

The effects of vanadate on cellular Ca2+ movements across the sarcolemma of cardiac muscle cells were investigated by measuring the intracellular and extracellular Ca2+ activities of guinea pig papillary muscle with Ca2+-selective electrodes. During the rest period following a steady-state of 2 contractions per second the extracellular Ca2+ concentration was increased over the basal level within a minute. During the rest period Ca2+ was transported across the sarcolemma into the extracellular space. Vanadate decreased the change in extracellular Ca2+ concentration during the rest period implying that the Ca2+ efflux across the sarcolemma was decreased by vanadate. Vanadate increased intracellular Ca2+ activities significantly (from 1.9 X 10(-7) M to 10(-6)M) resulting in an increase in resting tension. These results suggest that vanadate decreases Ca2+ efflux from the cells into the extracellular space by blocking Ca2+ transport across the sarcolemma, possibly blocking the Na+-Ca2+ exchange transport.

Effects of Dantrolene on the Interaction of Calcium and Erythrocyte Membrane

Dantrolene sodium in vitro inhibited the ATP-dependent efflux of calcium from human Fed cells, the Ca++-ATPase activity of red blood cell membrane fragments (RBCMF) and passive calcium binding to RBCMF. These effects were obtained With concentrations of dantrolene sodium between 2.5 and 20 uM. However the passive influx of Ca++ was measured at 37 degrees C in cells pretreated to abolish Ca++ pumping and was not influenced by dantrolene sodium. From these results, it was concluded that dantrolene sodium inhibits an active Ca++ extrusion across the red cell membrane by inhibiting Ca++-ATPase activity which is intimately involved with the Ca++ transport mechanism in the red cell membrane.