Estimation of the quasi-static Young's modulus of the eardrum using a pressurization technique

The quasi-static Young's modulus of the eardrum's pars tensa is an important modeling parameter in computer simulations. Recent developments in indentation testing and inverse modeling allow estimation of this parameter with the eardrum in situ. These approaches are challenging because of the curved shape of the pars tensa which requires special care during experimentation to keep the indenter perpendicular to the local surface at the point of contact. Moreover, they involve complicated contact modeling. An alternative computer-based method is presented here in which pressurization is used instead of indentation. The Young's modulus of a thin-shell model of the eardrum with subject-specific geometry is numerically optimized such that simulated pressurized shapes match measured counterparts. The technique was evaluated on six healthy rat eardrums, resulting in a Young's modulus estimate of 22.8±1.5MPa. This is comparable to values estimated using indentation testing. The new pressurization-based approach is simpler to use than the indentation-based method for the two reasons noted above.

Resveratrol protects spinal cord dorsal column from hypoxic injury by activating Nrf-2

Damage from oxidative stress plays a critical role in spinal cord injury. Nuclear factor erythroid 2-related factor (Nrf-2) signaling pathway can be activated by cellular oxidative stress. Resveratrol, a plant-derived polyphenolic compound found in red wine, has antioxidant properties. In the present study, we have examined the neuroprotective effect of resveratrol and the role of Nrf-2 in spinal cord hypoxic injury. The spinal cord was removed from adult male Wistar rats from T2-T10 and the dorsal column was used to induce hypoxic injury in vitro with and without treatment with resveratrol (50μM). Significant changes were found in the compound action potential (CAP) of spinal cord dorsal column, and hematoxyline and eosin (H&E) staining showed that resveratrol significantly improved neuronal injury. The biochemical assays showed significant changes in lipid peroxidase (LPO), reduced glutathione (GSH), superoxide dismutase (SOD), protein carbonyl (PC), mitochondrial ATP content, and mitochondrial Ca(++). Furthermore, using immunohistochemistry and Western blot, we found that after resveratrol treatment during hypoxic injury there was a significant activation of NrF-2 and down regulation of the glial fibrillary acidic protein (GFAP) content. The results show that resveratrol treatment has neuroprotective effects on CAP, Ca(++) loading, and biochemical parameters after hypoxic injury. The neuroprotective effect is likely to be exerted by increased activation of transcription factor Nrf-2 by resveratrol along with its direct antioxidant effect to ameliorate the oxidative damage and preserve mitochondrial function.

Transmastoid semicircular canal occlusion: a safe and highly effective treatment for benign paroxysmal positional vertigo and superior canal dehiscence

OBJECTIVES/HYPOTHESIS

Transmastoid occlusion of the superior semicircular canal in superior semicircular canal dehiscence (SSCD) syndrome and the posterior semicircular canal in intractable benign paroxysmal positional vertigo (BPPV) will produce resolution of preoperative symptoms.

STUDY DESIGN

Retrospective review, quality assurance.

METHODS

Sixteen patients with SSCD and 61 patients (65 ears) with intractable BPPV who underwent canal occlusion were reviewed. All patients underwent occlusion of the affected semicircular canal through a transmastoid approach.

RESULTS

Preoperative symptoms (vestibular, 13 patients; pulsatile tinnitus, 2 patients; or hyperacusis, 1 patient) were greatly improved or completely resolved in 15 of the 16 SSCD patients who underwent transmastoid occlusion of the superior canal. Hearing was preserved in 14 patients and improved in two patients. Vestibular symptoms were resolved in all intractable BPPV patients who underwent transmastoid occlusion of the posterior canal. One patient had a late recurrence of atypical BPPV. Almost all BPPV patients with normal preoperative hearing have an initial transient postoperative hearing loss, which when tested for is usually a mild to moderate mixed loss. Delayed sensorineural hearing loss was noted in three patients; one loss was profound whereas two were mild.

CONCLUSIONS

The transmastoid approach to canal plugging is successful in the treatment of symptoms in both SSCD and intractable BPPV, and is a familiar approach for the otologist. This is a viable alternative to the middle fossa approach for SSCD, thereby avoiding a craniotomy. Transmastoid is the definitive approach for posterior canal occlusion.

Study of an upper arm exoskeleton for gravity balancing and minimization of transmitted forces

An upper-arm wearable exoskeleton has been designed for the assistance and functional training of humans. One of the goals of this design is to provide passive assistance to a user by gravity balancing, while keeping the transmitted forces to the shoulder joints at a minimum. Consistent with this goal, this paper discusses: analytical gravity balancing design conditions for the structure of the exoskeleton; a possible implementation of these conditions into practical designs; the minimization of transmitted joint forces to the shoulder while satisfying the gravity balancing conditions; the numerical optimization of the system for gravity balancing and minimization of transmitted forces; and the effect of parameter variation on joint moments and joint forces via numerical optimization. An implementation of the design was undertaken using zero-free-length springs. The design idea presented in this paper may be useful in relieving the actuators effort of exoskeletons to support the weight of the arm and therefore the possibility of using small actuators and making the system light and portable or even a stand-alone passive support device can be developed based on these gravity balancing conditions.

Training Toddlers Seated on Mobile Robots to Steer Using Force-Feedback Joystick

The broader goal of our research is to train infants with special needs to safely and purposefully drive a mobile robot to explore the environment. The hypothesis is that these impaired infants will benefit from mobility in their early years and attain childhood milestones, similar to their healthy peers. In this paper, we present an algorithm and training method using a force-feedback joystick with an "assist-as-needed" paradigm for driving training. In this "assist-as-needed" approach, if the child steers the joystick outside a force tunnel centered on the desired direction, the driver experiences a bias force on the hand. We show results with a group study on typically developing toddlers that such a haptic guidance algorithm is superior to training with a conventional joystick. We also provide a case study on two special needs children, under three years old, who learn to make sharp turns during driving, when trained over a five-day period with the force-feedback joystick using the algorithm.

Ischaemic heart disease assessment by cardiovascular magnetic resonance imaging

Ischaemic heart disease (IHD) related mortality has been on the decline, although its prevalence has been on the rise since the late 1970s. One of the contributing factors to this decline has been improved diagnosis and therapeutic management. Every clinician seeks to answer four key questions while evaluating patients with suspected or known IHD: What is the global ventricular function? What is the regional ventricular function? Is the myocardium viable? What is the status of the coronary arteries? In the past decade cardiovascular magnetic resonance (CMR) imaging has emerged as an important clinical technique with the potential of answering all the pertinent questions in a single study. This has led to a significant increase in demand and utilisation of this modality. However, many clinicians are not well versed with this technology, its clinical utility, limitations and future prospects. With the increasing prevalence of IHD, CMR imaging is likely to be used more often in its diagnosis, prognostication and management. The review describes the basic principles and practical aspects of CMR imaging, and then discusses in detail the role of CMR in the diagnosis and management of IHD, its complications, and its utility in patients with acute myocardial infarction.

Measuring the quasi-static Young's modulus of the eardrum using an indentation technique

Accurate estimation of the quasi-static Young's modulus of the eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Young's modulus of the eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Young's modulus of each specimen was then estimated by numerically optimizing the Young's modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model eardrum, the estimated average Young's modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Young's modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.

Integration of patient-specific paranasal sinus computed tomographic data into a virtual surgical environment

BACKGROUND

The advent of both high-resolution computed tomographic (CT) imaging and minimally invasive endoscopic techniques has led to revolutionary advances in sinus surgery. However, the rhinologist is left to make the conceptual jump between static cross-sectional images and the anatomy encountered intraoperatively. A three-dimensional (3D) visuo-haptic representation of the patient's anatomy may allow for enhanced preoperative planning and rehearsal, with the goal of improving outcomes, decreasing complications, and enhancing technical skills.

METHODS

We developed a novel method of automatically constructing 3D visuo-haptic models of patients' anatomy from preoperative CT scans for placement in a virtual surgical environment (VSE). State-of-the-art techniques were used to create a high-fidelity representation of salient bone and soft tissue anatomy and to enable manipulation of the virtual patient in a surgically meaningful manner. A modified haptic interface device drives a virtual endoscope that mimics the surgical configuration.

RESULTS

The creation and manipulation of sinus anatomy from CT data appeared to provide a relevant means of exploring patient-specific anatomy. Unlike more traditional methods of interacting with multiplanar imaging data, our VSE provides the potential for a more intuitive experience that can replicate the views and access expected at surgery. The inclusion of tactile (haptic) feedback provides an additional dimension of realism.

CONCLUSION

The incorporation of patient-specific clinical CT data into a virtual surgical environment holds the potential to offer the surgeon a novel means to prepare for rhinologic procedures and offer training to residents. An automated pathway for segmentation, reconstruction, and an intuitive interface for manipulation may enable rehearsal of planned procedures.

Clinical profile and prevalence of rotavirus infection in children presented with acute diarrhea at tertiary care referral hospital at northern part of India

A prospective analysis of 90 clinically diagnosed cases with acute diarrhea over a period of one year was carried out to determine the prevalence of rotavirus infection in children between 2 months to 2 years of age. Enzyme Linked Immunosorbent Assay (ELISA) and Polyacrylamide Gel Electrophoresis (PAGE) were used for detection of rotavirus from stool sample. Fourteen (15.6%) of them were found to be positive for group A rotavirus, 9 (23%) cases were between 6 months to 1 year of age. Rotavirus excretion was highest (50%) when all three symptoms (diarrhea, vomiting and fever) occurred in the same child. A planned study for surveillance of rotavirus serotypes is required from this area.

Microwave-assisted synthesis of N-substituted cyclic imides and their evaluation for anticancer and anti-inflammatory activities

A number of N-substituted cyclic imides 3a-e, 5a-e, 7a-d, and 9a-e have been synthesized in very high yields, by condensation of various diacids 2, 4, 6, and 8 with different amines under microwave irradiation. These compounds were screened for anticancer and anti-inflammatory activities, and compounds 3c, 3e, 5c, 9c, and 9d exhibited anticancer activity against colon (COLO 205) cancer better than 5-fluorouracil and mitomycin-C, and compound 9b exhibited anti-inflammatory activity better than standard drug phenyl butazone.

A new heterobifunctional reagent for immobilization of biomolecules on glass surface

Synthesis of a new heterobifunctional reagent, [N-(2-trifluoroethanesulfonatoethyl)-N-(methyl)-triethoxysilylpropyl-3-amine] (NTMTA) is described for the immobilization of a variety of biomolecules on glass surface. Its triethoxysilyl group reacts with glass surface and trifluoroethanesulfonate ester structure reacts selectively with aminoalkyl/mercaptoalkyl function in biomolecules. The immobilization can be achieved by two ways involving two steps. The first route involves the reaction of NTMTA with glass beads followed by attachment of aminoalkyl- or mercaptoalkylated biomolecules. The second one involves the reaction of biomolecules, viz., oligonucleotides, proteins, etc., with NTMTA via their aminoalkyl or mercaptoalkyl functions to form a biomolecule conjugate, which is then reacted with glass beads (unmodified) to complete immobilization process. This has been demonstrated by successful immobilization of 5'-mercaptoalkyl- or aminoalkylated oligonucleotides and some commonly used enzymes on glass beads using NTMTA reagent.

Involvement of genitofemoral nerve with genital lesions in lepromatous leprosy

The case of a male patient diagnosed to have lepromatous leprosy with type 2 reaction on multibacillary multidrug therapy, with unusual, widespread involvement of genitalia in the form of plaque and nodules of leprosy over scrotum and perimeatal region of glans, necrotic lesions of erythema nodosum leprosum over scrotum, neuritis of genital branch of genitofemoral nerve bilaterally, and azoospermia, is reported.

Intrapartum computerized fetal heart rate parameters and metabolic acidosis at birth

OBJECTIVE

To estimate to what extent computerized fetal heart rate (FHR) parameters are affected by labor and to estimate the relationship between FHR parameters and the degree of fetal metabolic acidosis in laboring patients at term.

METHODS

Fifty-one women between 37 and 42 weeks' gestational age were recruited prospectively in the following groups: 1) nonlaboring women, and 2) laboring women requiring fetal scalp electrode for continuous electronic FHR monitoring. Computerized FHR analysis was performed for 1 hour within 6 hours of delivery in the nonlaboring group and continuously throughout labor in the laboring group. Multiple linear regression analysis was used to determine the relationship between individual FHR parameters during the last hour before delivery and the degree of metabolic acidosis at birth.

RESULTS

The umbilical cord artery base excess and pH did not show any significant correlation with any of the computer-derived FHR parameters studied. Both umbilical cord venous base excess and pH were inversely related to the number of large FHR decelerations (r = -.46, P <.01 and r = -.56, P <.01, respectively). Labor was associated with a 31% increase in both short- and long-term FHR variation in the reassuring FHR tracing group when compared with nonlaboring women. Although this increase in FHR variation was not seen in the nonreassuring FHR tracing group, there was no relationship to the degree of metabolic acidosis at birth.

CONCLUSION

In term pregnant women with reassuring FHR tracing, labor causes an increase in both short- and long-term FHR variation, which was abolished in the presence of nonreassuring FHR tracing. Computer-derived FHR parameters studied during the last hour of labor were not correlated with the degree of metabolic acidosis as measured in the umbilical artery at birth.

Diagnosis and management of benign paroxysmal positional vertigo (BPPV)

There is compelling evidence that free-floating endolymph particles in the posterior semicircular canal underlie most cases of benign paroxysmal positional vertigo (BPPV). Recent pathological findings suggest that these particles are otoconia, probably displaced from the otolithic membrane in the utricle. They typically settle in the dependent posterior canal and render it sensitive to gravity. Well over 90% of patients can be successfully treated with a simple outpatient manoeuvre that moves the particles back into the utricle. We describe the various techniques for this manoeuvre, plus treatments for uncommon variants of BPPV such as that of the lateral canal. For the rare patient whose BPPV is not responsive to these manoeuvres and has severe symptoms, posterior canal occlusion surgery is a safe and highly effective procedure.

Utility of Direct Fluorescent Antibody Test for detection of Chlamydia trachomatis and its detection in male patients with non gonococcal urethritis in New Delhi

The purpose of this study was assessment of prevalence of Chlamydia trachomatis and utility of Direct Fluorescent Antibody (DFA) test for its detection in male patients with non gonococcal urethritis in New Delhi, India. Thirty male patients with symptoms of dysuria showing polymorphs in their gram stained urethral smears with no evidence of Neisseria gonorrhoeae, and negative for Trichomonas vaginalis and Candida albicans by wet mount were subjected to DFA test for detection of C. trachomatis in urethral samples. Microscopic examination of gram stained urethral smears revealed 5-7 polymorphs/HPF in 90% of the patients. Evidence of C. trachomatis with DFA (MicroTrak) was detected in 11 cases (36.67%) when a cut off of 10 elementary bodies was considered essential. It is concluded that C. trachomatis is an important cause of non gonococcal urethritis in male patients in New Delhi and DFA test is a useful diagnostic tool in its detection. Where facilities are not available for its detection antichlamydial therapy should be recommended emperically.

A pilot study on observations on CD4 & CD8 counts in healthy HIV seronegative individuals

BACKGROUND & OBJECTIVES

CD4 T lymphocyte count is used to measure the progression of HIV infection and is recommended as part of the standard care of HIV infected person. Information on reference CD4 counts and CD4:CD8 ratio in healthy individuals is lacking in India. Therefore the present study was undertaken to obtain base-line data on CD4 counts and CD4:CD8 ratio of healthy population from north India and to assess the feasibility of using the values as reference in an extended larger study.

METHODS

In this pilot study 84 HIV negative healthy volunteers (56 males, 28 females) in the age group of 20-59 yr and who were willing to participate in the study were enrolled after proper counseling. Blood specimens were collected from each subject and processed for anti-HIV antibodies for exclusion of HIV. CD4 and CD8 counts of the samples were performed by fluorescence activated cell sorting (FACS).

RESULTS

The mean +/- SD of the absolute numbers of CD4 and CD8 lymphocytes/microliter was 763.6 +/- 226 and 547.5 +/- 190 in males and 797.9 +/- 263 and 567.7 +/- 250 in females. The range of the CD4 and CD8 counts was 365-1328 and 264-991 in males and 415-1257 and 224-1126 in females respectively. The mean +/- SD of the CD4:CD8 ratio was 1.47 +/- 0.42 in males and 1.52 +/- 0.45 in females.

INTERPRETATION & CONCLUSION

The results of this study showed that there is wide variability in CD4 count in our population, as is seen in studies reported from other parts of India. A large multicentric study could define the normal range for CD4 and CD8 counts and CD4:CD8 ratio in the Indian population.

Role of RyRs and IP3 receptors after traumatic injury to spinal cord white matter

Calcium influx and elevation of intracellular free calcium (Ca2+i), with subsequent activation of degenerative enzymes is hypothesized to cause cell injury and death after trauma. We examined the effects of traumatic compressive injury on (Ca2+)i dynamics in spinal cord white matter. We conducted electrophysiological studies with ryanodine and inositol (1,4,5)-triphosphate (IP3) receptor agonists and antagonists in an in vitro model of spinal cord injury (SCI). A 25-30-mm length of dorsal column was isolated from the spinal cord of adult rats, pinned in an in vitro recording chamber (37 degrees C) and injured with a modified clip (2-g closing force) for 15 sec. The functional integrity of the dorsal column was monitored electrophysiologically by quantitatively measuring the compound action potential (CAP) with glass microelectrodes. The CAP decreased to 55.2+/-6.8% of control (p < 0.05) after spinal cord injury (SCI). Chelation of Ca2+i with BAPTA-AM (a high-affinity calcium chelator) promoted significantly greater recovery of CAP amplitude (83.2+/-4.2% of control; p < 0.05) after injury. Infusion of caffeine (1 and 10 mM) exacerbated CAP amplitude decline (45.1+/-5.9% of control; p < 0.05; 44.6+/-3.1% of control; p < 0.05) postinjury. Blockade of Ca2+i release through ryanodine-sensitive receptors (RyRs) with dantrolene (10 microM) and ryanodine (50 microM), conferred significant (p < 0.05) improvement in CAP amplitude after injury. On the other hand, blockade of Ca2+i with inositol (1,4,5)-triphosphate receptor (IP3Rs) blocker 2APB (10 microM) also conferred significant improvement in CAP amplitude after injury (82.9+/-7.9%; p < 0.05). In conclusion, the injurious effects of Ca2+i in traumatic central nervous system (CNS) white matter injury appear to be mediated both by RyRs and through IP3Rs calcium-induced calcium release receptors (CICRs).

Human experience with canal plugging

Canal occlusion/plugging is a very effective technique with a low risk to hearing. The series of posterior semicircular canal occlusions described in this review now becomes the largest in the literature to date. It continues to support this procedure as the treatment of choice for intractable benign paroxysmal positional vertigo (BPPV). All 44 operated ears were relieved of BPPV, with one patient having an atypical late recurrence. Of the 40 ears with normal preoperative hearing, one had a delayed (3-month) sudden and permanent profound loss, while one other had a mild (20 dB) loss. Six patients had protracted courses of imbalance and motion sensitivity. Canal plugging has led to several new and innovative developments including the partial labyrinthectomy for difficult-to-access skull base lesions and superior semicircular canal plugging for dehiscence. These new procedures and their development are reviewed in this paper.

Effects of methylprednisolone and MK-801 on functional recovery after experimental chronic spinal cord injury

STUDY DESIGN

An experimental study was conducted to evaluate the effects of methylprednisolone and MK-801 after the compressive injury of spinal cord in rats.

OBJECTIVES

To investigate the effect of methylprednisolone and non-competitive NMDA antagonist MK-801 in long-term functional outcome after spinal cord injury (SCI).

METHODS

A randomized group A of Sprague-Dawley rats were treated with MK-801 (1.0 mg/kg, n=10; Group A) after a compression injury. A group of methylprednisolone (MP)-treated (30 mg/kg, n=10; Group B) and non-treated animals (n=9; Group C) were included for comparison. The functional motor outcome such as inclined plane (IP), toe spreading reflex (TSR), and modified Tarlov scale (TS) were measured in each animal at regular time points up to 8 weeks post-treatment. Histologically the injury site was scored in four groups and immunohistochemically Wallerian Degeneration (WD), astrocytosis and expression of beta-amyloid protein was identified.

RESULTS

In examining the IP data, no significant difference was recognized between the group means (P-value>0.5). For the TSR, there were no differences in the group responses. For the TS, the differences were not statistically significant. Only group B showed significance in cavitation scores compared to group A (P>0.0094), WD was significantly different than group C (P>0.03), astrocytosis was significantly higher than group A (P>0.001) and modest presence of beta-amyloid protein.

CONCLUSION

Our data indicate that one time bolus administration of MK-801 lacks any significant effect on axonal function in chronically injured rats. Daily bolus administration of MP at 30 mg/kg also did not ensure a better functional outcome. Immunohistochemically we have been able to show significant differences in WD, astrocytosis and small insignificant changes in beta-amyloid protein.