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Biomedical subjects

A Patwardhan

Publications and source records attributed to A Patwardhan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Reconstructed human epidermis composed of keratinocytes, melanocytes and Langerhans cells.

In addition to their basic biological interest, models of reconstructed epidermis provide useful tools for in vitro assessment of the toxicology and efficacy of new chemicals and drugs. The fact that the majority of these in vitro models are composed only of keratinocytes has excluded their use in the fields of skin pigmentation and immunology. After the successful introduction of functional melanocytes into the epidermal reconstruct, the integration of Langerhans cells remains an important challenge, particularly since after isolation of Langerhans cells from human epidermis, these cells cannot be subcultured and do not integrate into the reconstructing epidermis. The authors show that cord blood derived and CD34+ progenitors isolated from the peripheral blood give rise to residential Langerhans cells when co-seeded with normal human keratinocytes.

Cell Culture Techniques↗
PubMed1998

HLA-DM is expressed on the cell surface and colocalizes with HLA-DR and invariant chain in human Langerhans cells.

The subcellular distribution patterns of molecules involved in the process of antigen loading [HLA-DR, HLA-DM, and the cytoplasmic and luminal parts of the invariant chain (Ii, CD74)] were investigated in Langerhans cells (LC), both qualitatively and quantitatively. The analysis was performed by immunofluorescence labelling of acetone-fixed vertical cryostat sections from normal human skin specimens and subsequent examination using confocal laser scanning microscopy (CSLM). The intensity-modulated multiple-wavelength scanning (IMS) technique was used to enhance channel separation when scanning dual-labelled specimens. The mean (n = 9) relative epidermal volumes of reactivity were: HLA-DR 8%+/-3%, HLA-DM 6%+/-2%, luminal Ii 6%+/-2%, and cytoplasmic Ii 4%+/-1%. The difference between HLA-DR and the other epitopes was significant at the P<0.001 level. All molecule combinations, except the combination of HLA-DM and luminal Ii (which was not studied), were to various extents colocalized. Experiments performed on unfixed epidermal sheets showed that HLA-DM is present on the cell surface of LC, suggesting that HLA-DM may interact with HLA-DR on the surface to induce peptide loading.

Adult↗
PubMed1998

Flexion and traction effect on C5-C6 foraminal space.

OBJECTIVE: To determine the effects of cervical flexion and traction on foraminal volume and isthmus area at the C5-C6 foraminal space in cadavers. DESIGN: This study evaluated the foraminal space at C5-C6 in cadaver specimens during flexion and traction of the cervical spine. SETTING: An orthopedic biomechanics laboratory and department of radiology of a university medical center. PATIENTS OR OTHER PARTICIPANTS: Nine cadaver cervical spines, C1 through T3, were used in the study. Superficial tissues were dissected, preserving the ligaments. INTERVENTIONS: Proximal and distal portions of the cadaver spines were potted using bone cement. Spines were mounted and imaged with computed tomography in neutral position, 15 degrees of flexion, and maximum flexion with and without 25lbs of axial traction. MAIN OUTCOME MEASURES: The areas and volumes of the foramen were measured and calculated. RESULTS: Flexion alone significantly increased the foraminal volume and isthmus area at C5-C6. Traction resulted in little additional change. CONCLUSIONS: For cervical spines with mild to moderate degenerative changes at C5-C6, cervical flexion with or without traction produces significant increases in foraminal volume and area at the foraminal isthmus.

Cervical Vertebrae↗
PubMed1998

Relation between ventricular fibrillation voltage and probability of defibrillation shocks. Analysis using Hilbert transforms.

We used Hilbert transforms to re-evaluate the previously reported correlation between defibrillation shock outcome and absolute ventricular fibrillation voltage (AVFV). Previously in the literature, single values of AVFV acquired just prior to shock delivery were used to show a correlation between AVFV and shock outcome. In subsequent studies, a modified analysis procedure was used to show a correlation between shock outcome and moving average of AVFV. The use of single values of AVFV makes the AVFV sensitive to the local phase of the electrocardiographic (ECG) waveform, whereas moving averages are weighted by previous values of the ECG. The envelope is independent of the phase of the ECG and is not weighted by previous values of ECG as is the moving average. We explored, therefore, whether the AVFV computed from the envelopes of the ECG showed a stronger correlation with shock outcome than single values and moving averages of the AVFV. We estimated envelopes using the Hilbert transform. Orthogonal ECGs (sagittal, X; transverse, Y; and longitudinal, Z) were recorded from 11 dogs during 10 seconds of electrically induced ventricular fibrillation followed by a defibrillation shock with 50% probability of success. We used transvenous (right ventricular apex to subcutaneous patch) leads to deliver defibrillation shocks. Results from 236 successful and 249 unsuccessful trials showed, in contrast with the previously reported correlation, that moving average of AVFV was not higher for successful trials. In the Z direction, unsuccessful trials had higher voltage than successful trials (P < .05). Comparison of envelope voltages between successful and unsuccessful trials did not show any consistent and statistically significant differences. Although there were some methodological differences between ours and the previously reported studies, they are unlikely to have caused the discrepant observations. Our results suggest, therefore, that the absolute voltage of ECG during ventricular fibrillation is not robustly correlated with shock outcome.

Animals↗
PubMed1998

Use of amplitude-modulated breathing for assessment of cardiorespiratory frequency response within subrespiratory frequencies.

We present a new technique which uses amplitude-modulated breathing patterns to obtain estimates of frequency response between respiration and heart rate within subrespiratory frequencies. Frequency response between respiration and heart rate has been previously estimated using broadband respiration and metronomic breathing. However, the estimates obtained using these techniques show low coherence between respiration and heart rate within the subrespiratory frequencies (< 0.12-0.15 Hz). The advantages of amplitude-modulated breathing are: enhancement in the degree of perturbation within subrespiratory frequencies as indicated by relatively higher coherencies between respiration and heart rate (approximately equal to 0.7), and the subjects do not have to breathe at very low breathing frequencies or resort to breath holds. Use of a squared sine wave carrier modulated by sinusoidal functions enabled us to obtain energy distributions at subrespiratory frequencies without using demodulation. Results obtained at eight subrespiratory frequencies from ten subjects show that the new technique is easy to implement and produces relatively higher coherence between respiration and heart rate. The advantage of the new technique in terms of enhancing the level of perturbations within subrespiratory frequencies is particularly important, because it is in this frequency range that the interpretation of variability in heart rate in terms of autonomic origins is incompletely understood and is confounded by respiratory interactions.

Adult↗
PubMed1997

A study of the precision of confocal, ratiometric, Fura-2-based [Ca2+] measurements.

The precision with which quantitative confocal ratiometric Fura-2-based calcium measurements can be performed has been investigated. A standard confocal scanning laser microscope system has been modified so as to enable excitation with the 351 nm and 364 nm lines of the UV argon laser and simultaneous separation of the fluorescence emanating from the two different excitation wavelengths. Experiments have been performed on living cells and mainly on Fura-2 containing calibrated Ca2+ buffer solutions in order to study the variation of the precision with various experimental parameters in a controlled manner. Furthermore, expressions relating the precision of the calcium determination to various measured parameters are derived. These expressions have been used in conjunction with published excitation intensity spectra for Fura-2 in order to verify the experimental results and to analyse the variation of parameters that could not be experimentally tested. The results show that a photon number of the order of 10,000 per pixel, at maximum Ca2+ concentration and 351 nm excitation, is required in order to reduce the relative error at all concentrations to less than 30%. The commercially available laser wavelength combinations, 325 nm/380 nm and 334 nm/380 nm, were found to be the best as concerns the precision of the method.

Animals↗
PubMed1996

One electron reduction of vanadate(V) to oxovanadium(IV) by low-molecular-weight biocomponents like saccharides and ascorbic acid: effect of oxovanadium(IV) complexes on pUC18 DNA and on lipid peroxidation in isolated rat hepatocytes.

One electron reduction of vanadate(V) to vanadyl(IV) occurs in the presence of biocomponents, such as, saccharide s and L-ascorbic acid under physiological conditions. The vanadyl(IV) complexes thus generated have been demonstrated to introduce nicks in pUC18 DNA in the absence or in the presence of hydrogen peroxide and also exhibit lipid peroxidation in isolated rat hepatocytes. Thus the reducing and complexing abilities of these molecules may help in understanding the in vivo reduction and the resultant toxicity to cells incubated with vanadate(V).

Animals↗
PubMed1996

Biliary sepsis: an ascending infection.

AIM: To study the bacteriology of normal and obstructed biliary tree and determine the mode of biliary infection. METHODS: Fifty seven patients undergoing elective biliary surgery for calculous biliary disease cholecystitis 45, obstructive jaundice 12) were studied. Bile samples collected separately from gall bladder, common bile duct and duodenum at the time of surgery were processed for aerobic and anaerobic cultures and antibiotic assays. To locate endogenous foci of infection, urine, nasal swab and throat swab cultures were done. Isolates from/biliary tract were compared with those from other sites. RESULTS: Thirty eight patients (66.7%) had bactobilia. The prevalence was higher in patients with obstructive jaundice (10/12, 83.3%) than (p = 0.5) in those with non-obstructed biliary tree. Single bacterial infection (31 cases, 81 %) was more common than mixed infection (7 cases, 19%). Colonization of more than one segment of the biliary tree was seen in 30 patients (79%). E coli was the most frequently isolated organism. In 24 cases (63.2%), strains of organisms from the common bile duct and gall bladder were similar to those from the duodenum, and in only 10 cases (23.2%) were similar to those found in the nose, throat and urine. The antibiotic concentrations in the common bile duct after single doses of preoperative antibiotic (gentamicin and cephazolin) were lower in the obstructed biliary tree (1.5 +/- 0.4 milligrams/mL and 2.8 milligrams/mL respectively) than in the non-obstructed system (3.9 +/- 1.7 milligrams and 12.6 milligrams/mL/mL respectively) (p = 0.5 for both antibiotics). CONCLUSION: Ascending infection forms the mode of biliary sepsis in a majority of cases. Prophylactic antibiotics give low levels in the bile in an obstructed biliary tree.

Adult↗
PubMed1996

[Transport and localization of troxerutin in the venous wall].

The vein wall is nourished by diffusion of blood nutrients from the lumen and from the vasa vasorum. It is likely that drugs take the same ways to reach and diffuse through the vessel wall. Thus the uptake of a drug with affinity for the vein wall should give information on its transport to the tissue. This study aimed to explore troxerutin uptake by the long saphenous vein. Troxerutin is a naturally fluorescent flavonoid which has been known to improve subjective signs of patients with chronic venous insufficiency. Nine patients undergoing surgical treatment of varicosis were enrolled in the study. They received for the last 4 days before surgery either 3,500 mg of troxerutin (n = 4) or 1,000 mg twice daily (n = 2). Three patients as controls did not receive any drug. Two samples from thigh and calf long saphenous vein were harvested in each patients and investigated with a confocal laser scanning microscope developed by our institute measuring the fluorescence emitted by troxerutin after excitation by a 458 nm wavelength laser-beam. The intensity of the overall fluorescence was significantly higher in the treated groups (p < 0,001) and slightly higher in the patient who received 3,500 mg of troxerutin than with the lower dosage. The outer wall region provided the highest fluorescence in the treated group while a significant difference was observed in the fluorescence of the medial region between treated and control group. These results showed a marked affinity of troxerutin for the venous wall. The highest uptake in the outer wall region is likely to result from transport through vasa vasorum, owing to the rheologic properties of the drug. The significant medial fluorescence may account for the venous tone improvement with the drug.

Endothelium, Vascular↗
PubMed1995

The affinity of troxerutin for the venous wall measured by laser scanning microscopy.

The uptake and localization of troxerutin, a trihydroxy-ethyl-rutoside, in the venous wall have been studied in patients undergoing long saphenous vein surgery. Troxerutin, an autofluorescent drug, is currently used to relieve oedema and subjective symptoms in patients with chronic venous insufficiency. In order to determine the localization of the troxerutin, a confocal scanning laser microscope has been used to record the fluorescence from vein cross sections. The quantified fluorescence was used as a measure of the local concentration of troxerutin. In order to reduce the effects of local variation, several images have been scanned from each specimen. Then the recorded data have been analysed to see how the fluorescence varies in the radial direction within the venous wall. Results showed that troxerutin was significantly accumulated in both inner and outer parts of the venous wall. Whereas inner wall troxerutin uptake resulted from direct diffusion through the lumen, the outer wall uptake proceeded likely from the vasa vasorum circulation.

Adult↗
PubMed1995

The effect of prosthetic alignment on relative limb loading in persons with trans-tibial amputation: a preliminary report.

The prosthetic sockets of 14 independent persons with unilateral trans-tibial (BK) amputation were mounted on an adjustable alignment pylon. Vertical ground reaction forces were recorded in neutral prosthetic alignment and in 10 degrees of prosthetic socket varus, valgus, flexion, and extension. Stance phase time, peak vertical ground reaction force, and impulse were all found to be increased on the sound limb when compared to the amputated residual limb. Significant differences were found in stance phase time and peak vertical ground reaction force when comparing malaligned with neutrally aligned prosthetic limbs. Significant differences were also seen in impulse between neutrally aligned and malaligned prosthetic limbs. The results suggest that prosthetic malalignment in persons with trans-tibial amputation leads to increased loading of the contralateral limb.

Adult↗
PubMed1994

Optimization of the contact damping and stiffness coefficients to minimize human body vibration.

In this paper, a lumped mass human model is used to minimize the energy absorption at the feet/hip level when the body is subjected to vertical vibration. The contact forces are assumed unknown. By coupling the dynamic response of the body with certain objective criteria, the optimum damping and stiffness coefficients of shoes/chairs are sought. The optimization technique is based on the quasi-Newton and finite-difference gradient method and is used to seek optimum coefficients of the contact forces in the solution of the body's response in the frequency domain. The criteria of acceleration, displacement and internal forces response area swept for a range of 0-15 Hz form the basis of our simulation study. In the seated/standing postures it is found that for each criteria the frequency response shifts the peak of resonance of each body segment response from 4.5/3.67 Hz to 2.5/2.255 Hz. In addition, the total energy reduces drastically when the contact conditions are optimum. The method presented in this paper is useful in modeling the medium of contacts and especially in controlling the effects of human body vibration.

Compliance↗
PubMed1994

Sympathetic activity and blood pressure are tightly coupled at 0.4 Hz in conscious rats.

Interactions of sympathetic nerve activity (SNA) with blood pressure (BP) and heart rate (HR) were assessed in conscious rats while they rested quietly in a cloth sock (n = 7), roamed freely in their home cage (n = 6), and then after anesthesia with pentobarbital (30 mg/kg; n = 7). The power and coherence spectra below 3 Hz were calculated from data collected for 9.56 min. In the conscious rat, SNA spectral power peaked at 0.4 Hz, whereas the majority of spectral power for both BP and HR occurred at frequencies lower than 0.4 Hz. However, there was an inconspicuous peak in the BP power spectra at 0.4 Hz that was not seen in the HR spectra. Coherence between SNA and BP peaked at a frequency of approximately 0.4 Hz, the same frequency at which the SNA spectral peaks occurred. In contrast, at frequencies below 0.4 Hz where maximum BP power occurred, the coherence was considerably lower. Anesthesia with pentobarbital lowered spectral power for BP, SNA, and HR but essentially did not change the coherence between SNA and BP. Interactions between respiration and each of the other variables were weak in the conscious rat. However, prominent respiratory interactions at approximately 1.2 Hz were evident after anesthesia. These data indicate a close coupling between SNA and BP at 0.4 Hz, raising the possibility that the BP spectral power at 0.4 Hz reliably reflects sympathetic activity.

Anesthesia, General↗
PubMed1993

Gait analysis of dysvascular below-knee and contralateral through-knee bilateral amputees: a preliminary report.

Four elderly peripheral vascular insufficiency below-knee amputees, average age 58, underwent contralateral through-knee amputation for gangrene. All four became household ambulators with end-weight bearing designed prosthetic sockets and four-bar linkage knees. Gait analysis was performed with two AMTI (Newton, Mass) Biomechanics Force Platforms and a Watsmart Motion Monitoring System (Waterloo, Ontario). All four were observed to apparently "lock" the four-bar linkage prosthetic knee into extension during midstance and double limb support phases of gait. All subjectively felt that their through-knee limb was their more stable limb. Weight-bearing occurred during 63% of the gait cycle on the below-knee limb, 54% on the through-knee limb, and 17% in double limb support. Walking propulsion, as measured by forefoot impulse, was similar in the two limbs. The first peak of vertical force, corresponding to the elevation of the center of body weight as it passes over the weight-bearing limb, averaged 98% of body weight on the through-knee limb and only 93% on the below-knee limb. The second peak, corresponding to the kinetic energy of the falling trunk and muscle function providing linear acceleration of the center of body weight during propulsion, averaged 96% of body weight on the through-knee limb, and only 73% on the below-knee limb. Progression of the center of pressure, a qualitative measure of limb stability, was more orderly in the through-knee limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Dynamic response of the occipito-atlanto-axial (C0-C1-C2) complex in right axial rotation.

The torque-angular deformation in right axial rotation until failure of the ligamentous occipito-atlanto-axial complex subjected to variable loading rate (dynamic) axial torque was characterized using a biaxial MTS system. A special fixture and gear box that permitted right axial rotation of the specimen until failure without imposing any additional constraints were used to obtain the data. The specimens were divided into three groups and tested until failure at three different dynamic loading rates: 50, 100, and 400 degrees/s. A previous study by the authors provided data for quasi-static (4 degrees/s) loading conditions. The torque versus rotation curves can be divided into two straight regions and two transition zones. The plots clearly indicated that at loading rates higher than 4 degrees/s, the specimens became stiffer in the region of steadily increasing resistance prior to failure. The increase in stiffness was maximum at 100 degrees/s. The stiffness decreased somewhat at 400 degrees/s in comparison with 100 degrees/s, but this decrease was not significant. The resulting torque-right axial rotation curves were also examined to estimate the magnitude of maximum resistance (torque) and the corresponding angular rotation value. The average maximum resistance torque increased from 13.6 Nm at 4 degrees/s to 27.8 Nm at 100 degrees/s. The corresponding right angular rotation data (65-78 degrees), however, did not show any significant variation with loading rate. Posttest dissection of the specimens indicated that the type of injury observed was related to the rate of axial loading imposed on a specimen during testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

A purification strategy for inositol 1,4,5-trisphosphate 3-kinase from rat liver based upon heparin interaction chromatography.

Rat liver inositol 1,4,5-trisphosphate [Ins (1,4,5)P3] 3-kinase was purified in high yield by a three-step procedure reliant upon chromatography on heparin and calmodulin agarose. Purified enzyme was stable in the presence of the detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate (CHAPS) (0.1-0.5%) and the sulphydryl reducing reagent dithiothreitol (DTT). The purified enzyme was activated 2-3-fold by Ca2+ (1 microM) in the presence of calmodulin. Pyrophosphate and heparin were identified as inhibitors of the enzyme.

Animals↗
PubMed1991

Loading of the contralateral foot in peripheral vascular insufficiency below-knee amputees.

Seven ambulatory peripheral vascular insufficiency below-the-knee amputees underwent gait analysis to determine the local pressures on seven prominent plantar regions in their remaining limb. Patients occupied significantly less stance phase time on their remaining limbs. Peak, mean, and total pressures measured at each of the seven prominent areas was decreased as compared with laboratory age and sex matched controls. The results of this study suggest that the risk of contralateral limb amputation surgery is related to systemic peripheral vascular insufficiency or local factors, and not increased loading of the remaining contralateral "limb-at-risk."

Aged↗