Computational modeling of dorsal root ganglion stimulation using an Injectrode

Objective.Minimally invasive neuromodulation therapies like the Injectrode, which is composed of a tightly wound polymer-coated Platinum/Iridium microcoil, offer a low-risk approach for administering electrical stimulation to the dorsal root ganglion (DRG). This flexible electrode is aimed to conform to the DRG. The stimulation occurs through a transcutaneous electrical stimulation (TES) patch, which subsequently transmits the stimulation to the Injectrode via a subcutaneous metal collector. However, it is important to note that the effectiveness of stimulation through TES relies on the specific geometrical configurations of the Injectrode-collector-patch system. Hence, there is a need to investigate which design parameters influence the activation of targeted neural structures.Approach.We employed a hybrid computational modeling approach to analyze the impact of Injectrode system design parameters on charge delivery and neural response to stimulation. We constructed multiple finite element method models of DRG stimulation, followed by the implementation of multi-compartment models of DRG neurons. By calculating potential distribution during monopolar stimulation, we simulated neural responses using various parameters based on prior acute experiments. Additionally, we developed a canonical monopolar stimulation and full-scale model of bipolar bilateral L5 DRG stimulation, allowing us to investigate how design parameters like Injectrode size and orientation influenced neural activation thresholds.Main results.Our findings were in accordance with acute experimental measurements and indicate that the minimally invasive Injectrode system predominantly engages large-diameter afferents (Aβ-fibers). These activation thresholds were contingent upon the surface area of the Injectrode. As the charge density decreased due to increasing surface area, there was a corresponding expansion in the stimulation amplitude range before triggering any pain-related mechanoreceptor (Aδ-fibers) activity.Significance.The Injectrode demonstrates potential as a viable technology for minimally invasive stimulation of the DRG. Our findings indicate that utilizing a larger surface area Injectrode enhances the therapeutic margin, effectively distinguishing the desired Aβactivation from the undesired Aδ-fiber activation.

Computational modeling of dorsal root ganglion stimulation using an Injectrode

Objective

Minimally invasive neuromodulation therapies like the Injectrode, which is composed of a tightly wound polymer-coated platinum/iridium microcoil, offer a low-risk approach for administering electrical stimulation to the dorsal root ganglion (DRG). This flexible electrode is aimed to conform to the DRG. The stimulation occurs through a transcutaneous electrical stimulation (TES) patch, which subsequently transmits the stimulation to the Injectrode via a subcutaneous metal collector. However, effectiveness of stimulation relies on the specific geometrical configurations of the Injectrode-collector-patch system. Hence, there is a need to investigate which design parameters influence the activation of targeted neural structures.

Approach

We employed a hybrid computational modeling approach to analyze the impact of the Injectrode system design parameters on charge delivery and the neural response to stimulation. We constructed multiple finite element method models of DRG stimulation and multi-compartment models of DRG neurons. We simulated the neural responses using parameters based on prior acute preclinical experiments. Additionally, we developed multiple human-scale computational models of DRG stimulation to investigate how design parameters like Injectrode size and orientation influenced neural activation thresholds.

Main results

Our findings were in accordance with acute experimental measurements and indicated that the Injectrode system predominantly engages large-diameter afferents (Aβ-fibers). These activation thresholds were contingent upon the surface area of the Injectrode. As the charge density decreased due to increasing surface area, there was a corresponding expansion in the stimulation amplitude range before triggering any pain-related mechanoreceptor (Aδ-fibers) activity.

Significance

The Injectrode demonstrates potential as a viable technology for minimally invasive stimulation of the DRG. Our findings indicate that utilizing a larger surface area Injectrode enhances the therapeutic margin, effectively distinguishing the desired Aβ activation from the undesired Aδ-fiber activation.

Identification of selective Lyn inhibitors from the chemical databases through integrated molecular modelling approaches

In the current study, the Asinex and ChEBI databases were virtually screened for the identification of potential Lyn protein inhibitors. Therefore, a multi-steps molecular docking study was carried out using the VSW utility tool embedded in Maestro user interface of the Schrödinger suite. On initial screening, molecules having a higher XP-docking score and binding free energy compared to Staurosporin were considered for further assessment. Based on in silico pharmacokinetic analysis and a common-feature pharmacophore mapping model developed from the Staurosporin, four molecules were proposed as promising Lyn inhibitors. The binding interactions of all proposed Lyn inhibitors revealed strong ligand efficiency in terms of energy score obtained in molecular modelling analyses. Furthermore, the dynamic behaviour of each molecule in association with the Lyn protein-bound state was assessed through an all-atoms molecular dynamics (MD) simulation study. MD simulation analyses were confirmed with notable intermolecular interactions and consistent stability for the Lyn protein-ligand complexes throughout the simulation. High negative binding free energy of identified four compounds calculated through MM-PBSA approach demonstrated a strong binding affinity towards the Lyn protein. Hence, the proposed compounds might be taken forward as potential next-generation Lyn kinase inhibitors for managing numerous Lyn associated diseases or health complications after experimental validation.

Nutrient profile of five freshwater fish species

The nutrient profile of five freshwater fish species viz., Mystus vittatus, Ompok bimaculatus, Channa striata, Wallago attu and Pangasianodon hypophthalmus were studied. The proximate composition data shows that the moisture and fat content differed significantly (P<0.01) among the fish species. The fat content was significantly higher in P. hypophthalmus and M. vittatus. The moisture was significantly higher in C. striata. The potassium content was significantly (p<0.01) higher in C.striata. M.vittatus shows higher content of calcium. The other trace minerals like iron, copper and zinc contents of fish did not differ significantly among the species. The vitamin A content is maximum in O.bimaculatus whereas vitamin D content is higher in Mystus vittatus. The palmitic acid was significantly (p<0.01) higher in M. vittatus. The oleic acid was significantly (p<0.01) higher in C. striata and W. attu. The linoleic acid content was significantly (p<0.05) higher in P. hypophthalmus. One of the important PUFA i.e. DHA was significantly higher in O. bimaculatus and C.striata. The PUFA content was significantly (p<0.05) higher in O.bimaculatus and P.hypophthalmus. Among the amino acids, arginine, histidine, threonine and isoleucine were higher in P.hypophthalmus. C.striata and W. attu contain high amount of Tryptophan. Glutamic acid was high in O.bimaculatus and Aspartic acid was high in C. striata. The energy content was maximum in P. hypophthalmus. The nutrient profile of these fish species revealed that they were rich in all the essential nutrients required by human being. The information on nutrient profile of fish will give a guideline to dieticians, nutritionists, medical practitioners, researchers to advice consumers to take fish in their daily diet as a health food. SAARC J. Agri., 16(2): 25-41 (2018)

Nutrient profile of Indian climbing perch, Anabas testudineus

The proximate composition, fatty acid, amino acid and fat soluble vitamins of Indian climbing perch, Anabas testudineus, locally called “Koi” were assayed in relation to its body weight. The fish samples were collected from different geographical locations and were grouped as small (10-50g) and big (52-150g) sizes. The proximate composition, essential amino acid (EAA) and non-essential amino acid (NEAA) contents in Koi did not differ significantly between the groups. The monounsaturated fatty acid (MUFA) content was significantly (P<0.05) higher in bigger sized Koi. The polyunsaturated fatty acid (PUFA) content was 23.67±0.85 and 13.62±1.02 (%) respectively in the small and big sizes of Koi, while the docosahexaenoic acid (DHA) was significantly higher in small Koi. The vitamin A content was 85.77±0.35 and 93.90 ±1.34 (I.U./100g) respectively in small and big Koi. Vitamin D content was significantly higher in small Koi compared to big one. Vitamin E and K were significantly (P<0.05) higher in big Koi. The results indicated that Anabas testudineus is a good source of protein, fat, vitamins, amino acids and fatty acids.SAARC J. Agri., 15(1): 99-109 (2017)

Spiral formation at the microscale by μ-pyro-electrospinning

Spiral shapes occur frequently in nature as in the case of snail shells or the cochlea - the auditory portion of the inner ear. They also inspire many technological devices that take advantage of this geometry. Here we show that μ-pyro-electrospinning is able to control whipping instabilities in order to form spiralling fibres (down to 300 nm thick) directly on a support with true microscale regularity. The results show that polymer concentration plays a key role in producing reliable and long spirals. We investigate the cell response to these spiral templates that, thanks to their true regularity, would be useful for developing innovative cochlea regeneration scaffolds.

Observation of standing waves of electron-hole sound in a photoexcited semiconductor

Three-dimensional multicomponent plasmas composed of species with very different masses support a new branch of charge-density fluctuations known as acoustic plasmons. Here, we report on an ultrafast optical method to generate and probe coherent states of acoustic plasmons in a slab of GaAs, which relies on strong photoexcitation to create a large population of light electrons and heavy holes. Consistent with the random-phase-approximation theory, the data reveal standing plasma waves confined to these slabs, similar to those of conventional sound but with associated velocities that are significantly larger.

Spontaneous assembly of carbon-based chains in polymer matrixes through surface charge templates

Stable chains of carbon-based nanoparticles were formed directly in polymer matrixes through an electrode-free approach. Spontaneous surface charges were generated pyroelectrically onto functionalized ferroelectric crystals, enabling the formation of electric field gradients that triggered the dipole-dipole interactions responsible for the alignment of the particles, while embedded in the polymer solution. The phenomenon is similar to the dielectrophoretic alignment of carbon nanotubes reported in the literature. However, here the electric fields are generated spontaneously by a simple heat treatment that, simultaneously, aligns the particles and provides the energy necessary for curing the host polymer. The result is a polymer sheet reinforced with well-aligned chains of carbon-based particles, avoiding the invasive implementation of appropriate electrodes and circuits. Because polymers with anisotropic features are of great interest for enhancing the thermal and/or the electrical conductivity, the electrode-free nature of this technique would improve the scaling down and the versatility of those interconnections that find applications in many fields, such as electronics, sensors, and biomedicine. Theoretical simulations of the interactions between the particles and the charge templates were implemented and appear in good agreement with the experimental results. The chain formation was characterized by controlling different parameters, including surface charge configuration, particle concentration, and polymer viscosity, thus demonstrating the reliability of the technique. Moreover, micro-Raman spectroscopy and scanning electron microscopy were used for a thorough inspection of the assembled chains.

Improving fatigue damage resistance of alumina through surface grading

Porcelain-veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesized that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, we fabricated graded structures by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture-resistant alumina crowns.

In vitrothermal therapy of AT-1 Dunning prostate tumours

To advance the utility of prostate thermal therapy, this study investigated the thermal thresholds (temperature-time) for prostate tissue destruction in vitro. The AT-1 Dunning prostate tumour model was chosen for the study. Three hundred micron thick sections were subjected to controlled temperature-time heating, which ranged from low (40 degrees C, 15 min) to high thermal exposures (70 degrees C, 2 min) (n = 6). After subsequent tissue culture at 37 degrees C, the sections were evaluated for tissue injury at 3, 24 and 72 h by two independent methods: histology and dye uptake. A graded increase in injury was identified between the low and high thermal exposures. Maximum histologic injury occurred above 70 degrees C, 1 min with >95% of the tissue area undergoing significant cell injury and coagulative necrosis. The control and 40 degrees C, 15 min sections showed histologic evidence of apoptosis following 24 and 72 h in culture. Similar signs of apoptosis were minimal or absent at higher thermal histories. Vital-dye uptake quantitatively confirmed complete cell death after 70 degrees C, 2 min. Using the dye data, Arrhenius analysis showed an apparent breakpoint at 50 degrees C, with activation energies of 135.8 kcal/mole below and 4.7 kcal/mole above the threshold after 3 h in culture. These results can be used as a conservative benchmark for thermal injury in the cancerous prostate. Further characterization of the response to thermal therapy in an animal model and in human tissues will be important in establishing the efficacy of the procedure

In vitroassessment of the efficacy of thermal therapy in human benign prostatic hyperplasia

The successful management of BPH with minimally invasive thermal therapies requires a firm understanding of the temperature-time relationship for tissue destruction. In order to accomplish this objective, the present in vitro study assesses the cellular viability of human BPH tissue subjected to an experimental matrix of different temperature-time combinations. Hyperplastic prostate tissue was obtained from 10 radical prostatectomy specimens resected for adenocarcinoma. A portion of hyperplastic tissue from the lateral lobe of each prostate was sectioned into multiple 1 mm thick tissue strips, placed on a coverslip and thermally treated on a controlled temperature copper block with various temperatures (45-70 degrees C) for various times (1-60 min). After heat treatment, the tissue slices were cultured for 72 h and viability was assessed using two independent assays: histology and dye uptake for stromal tissue and using histology alone for the glandular tissue. The hyperplastic human prostate tissue showed a progressive histological increase in irreversible injury with increasing temperature-time severity. The dye uptake and histology results for stromal viability were similar for all temperature-time combinations. In vitro thermal injury showed 85-90% stromal destruction (raw data) of human BPH for temperature-time combinations of 45 degrees C for 60 min, 50 degrees C for 30 min, 55 degrees C for 5 min, 60 degrees C for 2 min and 70 degrees C for 1 min. Apoptosis was also identified in the control and milder treated tissues with the degree of glandular apoptosis (about 20%) more than that seen in the stromal regions (< 5%). The Arrhenius model of injury was fitted to the data for conditions leading to a 90% drop in viability (normalized to control) obtained for stromal tissue. The activation energies (E) were 40.1 and 38.4 kcal/mole for the dye uptake study and histology, respectively, and the corresponding frequency factors (A) were 1.1 x 10(24) and 7.78 x 10(22)/s. This study presents the first temperature-time versus tissue destruction relation for human BPH tissue. Moreover, it supports the concept that higher temperatures can be used for shorter durations to induce tissue injury comparable with the current clinically recommended lower temperature-longer time treatments (i.e. 45 degrees C for 60 min) for transurethral microwave thermotherapy of the prostate.

Veneer vs. Core Failure in Adhesively Bonded All-ceramic Crown Layers

Joining a brittle veneer to a strong ceramic core with an adhesive offers potential benefits over current fabrication methods for all-ceramic crowns. We tested the hypothesis that such joining can withstand subsurface radial cracking in the veneer, from enhanced flexure in occlusal loading, as well as in the core. Critical conditions to initiate fractures were investigated in model crown-like layer structures consisting of glass veneers epoxy-joined onto alumina or zirconia cores, all bonded to a dentin-like polymer base. The results showed a competition between critical loads for radial crack initiation in the veneers and cores. Core radial cracking was relatively independent of adhesive thickness. Zirconia cores were much less susceptible to fracture than alumina, attributable to a relatively high strength and low modulus. Veneer cracking did depend on adhesive thickness. However, no significant differences in critical loads for veneer cracking were observed for specimens containing alumina or zirconia cores.

Sublethal temperature stress in juvenile Labeo rohita (Ham-Buch.) and Rita rita (Ham.): some physiological changes

Juveniles of fish L. rohita and R. rita subjected to a rapid (5 min) sublethal temperature increase from 28 to 35 degrees C showed significant increase in cortisol and decrease in interrenal ascorbic acid. Hypercholesterolemia, hyperglycemia and hyperlactemia were also evident accompanied by increased blood haemoglobin and haematocrit and stable protein levels. Compensatory responses were initiated within 72 hr in both the fishes. R. rita recovered more quickly indicating it to be more resistant to the heat stress than L. rohita. Hence fishes subjected to sublethal temperature stress should be given a metabolic recovery period of 72 hr prior to further stress being applied.

Evaluation of thermal therapy in a prostate cancer model using a wet electrode radiofrequency probe

PURPOSE

To determine the temperature-time threshold of local cell death in vivo for thermal therapy in a prostate cancer animal model and to use this value as a benchmark to quantify global tissue injury.

MATERIALS AND METHODS

Two studies were designed in the Dunning AT-1 rat prostate tumor hind limb model. For both studies, a wet electrode radiofrequency (RF) probe was used to deliver 40 W of energy for 18 to 62 seconds after a 30-second infusion of hypertonic saline/Hypaque through the RF antenna. Thermal history measurements were obtained in tumors from at least two Fluoroptic probes placed radially 5 mm from the axis of a RF probe and 10 mm below the surface of the tissue. In study 1, the thermal history required for irreversible cell injury was experimentally determined by comparing the predicted injury accumulation (omega) with cell viability at the fluoroptic probe locations using an in vivo-in vitro assay. The omega value was calculated from the measured thermal histories using an Arrhenius damage model. In study 2, RF energy was applied for 40 seconds in all cases. At 1, 3, and 7 days after thermal therapy, triphenyltetrazolium chloride dye (TTC) and histologic analyses were performed to assess global tissue injury within a 5-mm radius from the axis of the RF probe.

RESULTS

Study 1 showed that cell survival dropped to 0 for 0.42 < omega < 0.7. This result was the basis for selection of 40 seconds of RF thermal therapy in study 2, which yielded omegaave = 0.5 in the tissue 5 mm from the probe axis. Both TTC and histology analysis showed that sham-treated tissue was not irreversibly injured. However, there was an inherent heterogeneity present in the tumor that accounted for as much as 15% necrosis in control or sham-treated tissue. In contrast, at 1, 3, and 7 days after therapy, significantly less enzyme activity was observed by TCC in thermally treated tissue compared with sham-treated tissue (35 v 85%; P < 0.001). Histologic analysis of thermally treated tissues revealed a gradual increase in the percent of coagulative necrosis (47%-70%) with a concomitant decrease in the percentage of shocked cells (53%-28%). At day 7, <3% viability was observed in treated tumors compared with 90% viability in sham-treated tissue.

CONCLUSION

The threshold of cellular injury in vivo corresponded to omega > 0.7 (> or =48 degrees C for 40 seconds). Global tissue injury could be conservatively predicted on the basis of local thermal histories during therapy.

Supraphysiological thermal injury in Dunning AT-1 prostate tumor cells

To investigate the potential application of thermal therapy in the treatment of prostate cancer, the effects of supraphysiological temperatures (40-70 degrees C) for clinically relevant time periods (approximately 15 minutes) were experimentally studied on attached Dunning AT-1 rat prostate cancer cells using multiple assays. The membrane and reproductive machinery were the targets of injury selected for this study. In order to assess membrane injury, the leakage of calcein was measured dynamically, and the uptake of PI was measured postheating (1-3 hours). Clonogenicity was used as a measure of injury to the reproductive machinery 7 days post-injury after comparable thermal insults. Experimental results from all three assays show a broad trend of increasing injury with an increase in temperature and time of insult. Membrane injury, as measured by the fluorescent dye assays, does not correlate with clonogenic survival for many of the thermal histories investigated. In particular, the calcein assay at temperatures of < or = 40 degrees C led to measurable injury accumulation (dye leakage), which was considered sublethal, as shown by significant survival for comparable insult in the clonogenic assay. Additionally, the PI uptake assay used to measure injury post-thermal insult shows that membrane injury continues to accumulate after thermal insult at temperatures > or = 50 degrees C and may not always correlate with clonogenicity at hyperthermic temperatures such as 45 degrees C. Last, although the clonogenic assay yields the most accurate cell survival data, it is difficult to acquire these data at temperatures > or = 50 degrees C because the thermal transients in the experimental setup are significant as compared to the time scale of the experiment. To improve prediction and understanding of thermal injury in this prostate cancer cell line, a first-order rate process model of injury accumulation (the Arrhenius model) was fit to the experimental results. The activation energy (E) obtained using the Arrhenius model for an injury criterion of 30 percent for all three assays revealed that the mechanism of thermal injury measured is likely different for each of the three assays: clonogenics (526.39 kJ/mole), PI (244.8 kJ/mole), and calcein (81.33 kJ/mole). Moreover, the sensitivity of the rate of injury accumulation (d omega/dt) to temperature was highest for the clonogenic assay, lowest for calcein leakage, and intermediate for PI uptake, indicating the strong influence of E value on d omega/dt. Since the clonogenic assay is linked to the ultimate survival of the cell and accounts for all lethal mechanisms of cellular injury, the E and A values obtained from clonogenic study are the best values to apply to predict thermal injury in cells. For higher temperatures (> or = 50 degrees C) indicative of thermal therapies, the results of PI uptake can be used as a conservative estimate of cell death (underprediction). This is useful until better experimental protocols are available to account for thermal transients at high temperature to assess clonogenic ability. These results provide further insights into the mechanisms of thermal injury in single cell systems and may be useful for designing optimal protocols for clinical thermal therapy.

Response of a liver tissue slab to a hyperosmotic sucrose boundary condition: microscale cellular and vascular level effects

Transport of a non-permeating CPA in liver tissue was studied by experimental and theoretical techniques. The system consisted of a 20 mm x 15 mm x 500 microns (thick) slab of liver tissue which was exposed to culture media and hyperosmotic sucrose (0.3 or 0.6 M) at the boundary. The volumetric changes of cell and vascular spaces within the tissue slab at 125 microns from one of the symmetric boundaries was studied by slam freezing followed by freeze substitution microscopy. The experimental data was then theoretically investigated using two models; one based on an effective diffusion coefficient for sucrose, and another which incorporated the convective flux of water out of the cells (and the tissue) while sucrose diffuses in. We estimate the effective diffusion of sucrose as 16-33% of the actual diffusivity of sucrose in bulk water. The role of convection of water out of the tissue is against the flow of sucrose and appears to be important in reducing the effective diffusivity of the sucrose. The role of vascular compliance, porosity and tortuosity are also discussed with respect to our results.

Aminosidine plus sodium stibogluconate for the treatment of Indian kala-azar: a randomized dose-finding clinical trial

This randomized, open sequential design trial was set up to assess the efficacy, tolerability and toxicity of 20 d courses of combined intramuscular aminosidine and sodium stibogluconate at various dosages in patients with newly-diagnosed kala-azar in Bihar, India. Three successive studies of 96 patients each were originally planned with aminosidine administered at 12, 6 and 3 mg/kg/d, respectively. For each aminosidine dosage, patients were randomly assigned to receive sodium stibogluconate at 20, 10 or 5 mg/kg/d of antimony. Ninety-six patients were enrolled and assigned aminosidine 12 mg/kg/d as scheduled. In the subsequent study with aminosidine at 6 mg/kg/d, the trial was interrupted after 40 patients had entered owing to inadequacy of the treatment. With aminosidine 12 mg/kg/d the success rates with sodium stibogluconate at 20, 10 and 5 mg/kg/d were 88%, 71% and 72%, respectively and did not differ significantly. With aminosidine 6 mg/kg/d, 69%, 50% and 46% of patients were cured with the same sodium stibogluconate doses, respectively; again, there was no significant difference between the subgroups. The overall success rate with aminosidine at 12 mg/kg/d (76%) was significantly higher than that with 6 mg/kg/d (55%) (odds ratio = 2.69; 95% confidence interval, 1.11-6.4). Patients improved clinically and the treatments were equally well tolerated. The combination of aminosidine 12 mg/kg/d and sodium stibogluconate 20 mg/kg/d for 20 d appears to be an effective and safe replacement in Bihar for sodium stibogluconate alone for > or = 40 d.

Effect of GABA analogues on various components of maximum electroshock-induced seizures in mice

Out of fourteen compounds reported here only four [N-valproyl GABA (V.GABA), N-phthaloyl GABA (P.GABA), gamma-phthalimido N-amyl butyramide (PGA) and gamma-phthalimido N-phenyl butyramide (PGP)] gave significant protection to all the four components of maximal electroshock-induced seizures (MES) in mice. It appeared that substitution of either amino or carboxylic or both groups of gamma-aminobutyric acid (GABA) with bulkier groups like aliphatic or aromatic carbons usually produced effective anticonvulsant GABA derivatives. V.GABA and P.GABA were the most effective anticonvulsant GABA derivatives in protecting all the components of MES-induced seizures. They were 2.3 and 1.5 times potent than sodium valproate in molar ratio, but P.GABA has low therapeutic index when compared to V.GABA. The observed anticonvulsant activity may be due to enhanced GABA concentration in the CNS. Probably, the active compound (V.GABA) crossed the blood brain barrier and hydrolysed to GABA and valproic acid to bring about its anticonvulsant action.

Treatment of visceral leishmaniasis (kala-azar) with aminosidine (= paromomycin)-antimonial combinations, a pilot study in Bihar, India

A 20 d drug regimen of aminosidine (= paromomycin) at 12 mg/kg/d in combination with sodium stibogluconate at 20 mg/kg/d proved efficacious and well-tolerated in patients with visceral leishmaniasis in the State of Bihar, India. Eighteen of 22 evaluable patients achieved an ultimate cure. The remaining 4 patients, although not cleared of parasites, had their parasite grade reduced and also improved clinically. This confirms prior findings in Kenyan patients with kala-azar, and indicates that this regimen is a valid alternative to antimonial compounds alone in the State of Bihar, where cases of kala-azar not responding to antimonial drugs and intolerant of pentamidine are increasingly recorded.

Antinociceptive action of GABA-mimetic agent--N-phthaloyl GABA

N-phthaloyl GABA (P-GABA), a nonselective GABA-ergic drug, showed positive analgesic response in four different models in mice, viz-tail immersion, tail clip, hot plate and writhing-induced by acetic acid. Antinociceptive ED50 (ip in mice) of P-GABA was lowest in tail immersion method (ED50 = 24.27, mg/kg). Though pethidine (10 mg/kg, ip) significantly potentiated the antinociceptive action of P-GABA (20 mg/kg, ip), pretreatment of naloxone (5 mg/kg, im) did not influence the same. Pretreatment with atropine (10 mg/kg, im), picrotoxin (0.08 mg/kg) and 3-mercaptopropionic acid (2 mg/kg) reduced the antinociceptive action of P-GABA significantly. But pretreatment with bicuculline (0.4 mg/kg), a specific GABA antagonist, did not reduce the antinociceptive action of P-GABA.

Antiulcer activity of N-phthaloyl GABA--a new GABA mimetic agent

N-phthaloyl GABA (P. GABA) inhibited gastric ulceration induced by 3 hr restraint stress at 4 degrees C (CRS) in albino rats. Antiulcer activity of P. GABA was compared with sodium valproate and cimetidine. P. GABA, sodium valproate and cimetidine showed a dose dependent reduction of gastric ulceration. Pretreatment with GABA antagonists-bicuculline methiodide (0.5 mg/kg, im) or 3 mercaptopropionic acid (2 mg/kg, im) reversed the antiulcerogenic activity of both the drugs (P. GABA and sodium valproate). GABA antagonists as such did not induce gastric ulceration in normal rats.

Synthesis and anticonvulsant activity of N-phthaloyl GABA--a new GABA derivative

A new gamma-aminobutyric acid derivative, N-phthaloyl GABA (P-GABA), was synthesised and its anticonvulsant activity was tested and compared with sodium valproate for efficacy against experimentally induced convulsions in mice. At a dose of 80 mg/kg, P-GABA rendered more protection than sodium valproate. ED50 of P-GABA and sodium valproate against bicuculline-induced convulsion was 96 and 301 mg/kg respectively in mice.