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Biomedical subjects

S Mehta

Publications and source records attributed to S Mehta.

At least 127 records · Page 7Linked to original sources

Dynamic in vitro and in vivo performance of a permanent total artificial heart.

In vivo characterization studies were performed to compare the dynamic in vivo performance of the Penn State/3M Health Care electric total artificial heart to existing in vitro data. Fully implanted systems were utilized including the artificial heart, controller, backup batteries, compliance chamber, and transcutaneous energy transmission. Catheters were implanted to measure central venous pressure (CVP), left atrial pressure (LAP), right atrial pressure (RAP), pulmonary artery pressure (PAP), and aortic pressure (AoP). Cardiac output (CO) was determined from the implanted controller, and systemic vascular resistance (SVR) was calculated. Steady state data were collected for each animal along with data regarding the transient responses to changes in preload and afterload. Preload was manipulated through volume changes. Afterload changes were accomplished through vasoactive agents. Increased preload caused little change in cardiac output because the pump output was nearly maximum at baseline. LAP, AoP, and SVR increased with increasing RAP. Decreased preload caused a reduction in CO, LAP, and SVR. Afterload increase resulted in a slight decrease in flow and an increase in system power and SVR. Afterload reduction was accompanied by a decrease in preload and a concomitant reduction in flow. Overall, the system response was similar to the response observed in vitro.

Animals↗

Pharmacokinetics of a degradable drug delivery system in bone.

Local delivery of antibiotics via a degradable carrier has the potential for high local antibiotic levels and avoids systemic toxicity. Intravenous access, renal function monitoring, and later surgical removal may not be required when degradable local delivery modalities are used. This study examined the in vivo elution of gentamicin from processed bovine collagen (Type I). Gentamicin impregnated collagen (3 mg/kg) was implanted into the femoral medullary canal of 45 adult white rabbits. The gentamicin was released into the bone and averaged greater than 600 micrograms/ml during the initial 48 hours. Local bone levels fell to 144.40 +/- 229.84 micrograms/ml at 5 days and were subsequently greater than or equal to 10.30 +/- 5.02 micrograms/ml through Day 28. Serum levels reached an average peak of 1.25 +/- 0.29 micrograms/ml 5 hours after implantation and fell below 1.0 microgram/ml at 12 hours after implantation. Serum levels subsequently averaged less than or equal to 0.63 +/- 0.09 microgram/ml through Day 28. Collagen impregnated with gentamicin proved to be an effective degradable carrier of gentamicin in the healthy rabbit; it provided local bone concentrations above the minimum inhibitory concentration of gentamicin and serum concentrations below levels associated with systemic toxicity as long as 28 days after implantation.

Animals↗

A multi-user real time inventorying system for radioactive materials: a networking approach.

A computerized system for radioisotope management and real time inventory coordinated across a large organization is reported. It handles hundreds of individual users and their separate inventory records. Use of highly efficient computer network and database technologies makes it possible to accept, maintain, and furnish all records related to receipt, usage, and disposal of the radioactive materials for the users separately and collectively. The system's central processor is an HP-9000/800 G60 RISC server and users from across the organization use their personal computers to login to this server using the TCP/IP networking protocol, which makes distributed use of the system possible. Radioisotope decay is automatically calculated by the program, so that it can make the up-to-date radioisotope inventory data of an entire institution available immediately. The system is specifically designed to allow use by large numbers of users (about 300) and accommodates high volumes of data input and retrieval without compromising simplicity and accuracy. Overall, it is an example of a true multi-user, on-line, relational database information system that makes the functioning of a radiation safety department efficient.

Computer Communication Networks↗

The ankle brachial index independently predicts walking velocity and walking endurance in peripheral arterial disease.

OBJECTIVES: Maintaining function among older men and women is an important public health goal as the population lives longer with chronic disease. We report the relationships between lower extremity peripheral arterial disease (PAD), PAD severity, and PAD-related symptoms with walking velocity and endurance among men and women aged 55 and older. DESIGN: A cross-sectional design. SETTING: An academic medical center. PARTICIPANTS: Participants with PAD were men and women aged 55 and older identified from a blood flow laboratory or a general medicine practice (n = 158). Randomly selected controls without PAD were identified from the general medicine practice (n = 70). MEASUREMENTS: PAD was diagnosed and quantified using the ankle brachial index (ABI). Subjects were categorized according to whether they had severe PAD (ABI <0.40), mild to moderate PAD (ABI 0.40 to <0.90), or no PAD (ABI 0.90 to <1.50). Walking endurance was assessed with the 6-minute walk. Usual walking velocity and maximal walking velocity were assessed with "usual" and "maximal" paced 4-meter walks, respectively. RESULTS: Average distances achieved in the 6-minute walk were 1569+/-390 feet for subjects with ABI 0.90-1.50, 1192+/-368 feet for subjects with ABI 0.40 to <0.90, and 942+/-334 feet for subjects with ABI < 0.40 (trend P value < .001). Walking velocities for both the usual and maximal paced 4-meter walks were slowest among subjects with ABI < 0.40 and fastest among subjects with ABI 0.90 to <1.50. Subjects with PAD who had pain at rest had slower walking velocity and poorer walking endurance than other subjects with PAD. In multiple linear regression analyses that included subjects with PAD only, ABI level was an independent predictor of 6-minute walk performance (regression coefficient = 159 ft/0.40 ABI units, P = .011), usual paced 4-meter walk (regression coefficient = .095 meters/sec/0.40 ABI units, P = .031), and maximal paced 4-meter walk (regression coefficient = .120 meters/sec/0.40 ABI units, P = .050) adjusting for age, sex, race, leg symptoms, and comorbid diseases known to affect functioning. Pain at rest was associated independently with the maximally paced 4-meter walk (-0.201 meters/sec, P = .024), but not with the other walks. CONCLUSION: ABI level has a measurable and independent association with walking endurance and both usual and maximal walking velocity. These data suggest that PAD may impair lower extremity function by diminishing function of both Type I ("slow twitch") and Type II ("fast twitch") muscle fibers. Because walking velocity has important prognostic implications for functioning, these data also suggest that ABI may be used to identify patients at increased risk of mobility loss.

Aged↗

Endogenous pulmonary nitric oxide in the regulation of airway microvascular leak.

Endogenous nitric oxide (NO) is an important modulator of airway function, but its role in the regulation of airway microvascular leak (AMVL) remains unclear. Thus we assessed the effects of NO synthase (NOS) inhibition on expired NO (ENO) levels and on AMVL measured by the Evans blue dye technique in guinea pigs. In control unsensitized animals, systemic NG-nitro-L-arginine methyl ester (L-NAME) reduced ENO by 70 +/- 8% (P < 0.01) and reduced AMVL by 92 +/- 1 and 44 +/- 17% (P < 0.05 for both) in the extrapulmonary and intrapulmonary airways, respectively. In animals sensitized and challenged with intratracheal antigen, markedly increased levels of AMVL and ENO were similarly attenuated by L-NAME. In contrast, aminoguanidine, a relatively selective type II NOS inhibitor, reduced ENO in both antigen-sensitized and control unsensitized animals by 39 +/- 3% (P < 0.01) but had no effect on AMVL. These data indicate that endogenous pulmonary NO contributes to both basal and antigen-stimulated levels of AMVL in guinea pigs and that this NO-dependent activity does not appear to be derived from type II NOS.

Animals↗

A calcaneal fracture with extrusion of the posterior facet.

This is a case report of a 19-year-old woman who sustained multiple fractures including a right calcaneal fracture with extrusion of the posterior facet. The medial soft-tissue injury led to a full thickness skin loss. Despite loss of subtalar motion and decreased toe movement, she is satisfied with her result. The importance of the soft-tissue injuries, especially to the skin and tendons, associated with severely displaced calcaneal fracture dislocations is emphasized by this case report.

Adult↗

Characterizing alterations in the pulmonary surfactant system in a rat model of Pseudomonas aeruginosa pneumonia.

Bacterial pneumonia remains a significant cause of patient morbidity and mortality worldwide. Pulmonary surfactant serves to maintain homeostasis in the lung through the maintenance of alveolar stability and the regulation of the alveolar immune response. The purpose of this study was to characterize the lung injury and associated surfactant alterations in a rat model of acute Pseudomonas aeruginosa pneumonia. Pneumonia was induced in male Sprague-Dawley rats via intratracheal injection of 0.2 ml, phosphate-buffered saline (PBS) containing P. aeruginosa (6x10(8) colony-forming units x mL(-1)). Control animals received 0.2 mL sterile PBS. Twenty-four hours after inoculation, the pneumonia group (PN) exhibited clinical signs of pneumonia including deficits in gas exchange, leukopenia and elevated arterial lactate levels. Morphological assessment confirmed the presence of pneumonia with airspaces filled with polymorphonuclear cells. Lung homogenate analysis demonstrated evidence of bacterial colonization of pneumonic lung tissue. Lung compliance was also significantly lower in the PN group. Lung lavage analysis of PN rats revealed the pooled surfactant levels to be lower and the surfactant function reduced compared to control rats. Surfactant composition was also found to be altered in PN rats. These results demonstrate that in Pseudomonas aeruginosa pneumonia, the pulmonary surfactant system is both poorly functioning and reduced in quantity. These alterations may contribute to the lung dysfunction characteristic of this disorder.

Acute Disease↗

Oxidative-hepatic injury of isoniazid-rifampicin in young rats subjected to protein and energy malnutrition.

The role of protein and energy malnutrition in the pathogenesis of isoniazid (INH)-rifampicin (RMP) induced hepatic injury was investigated. Status of oxidative/antioxidative profile was the mechanistic approach to enumerate the nature of injury. Weanling rats were fed with ad-libitum quantity of isocaloric diets containing 5% casein based proteins for the production protein and energy malnutrition. INH and RMP (50 mg/kg of each) were injected intraperitonially for a period of two weeks. Analysis of serum transaminases and histopathological observations revealed hepatic injury. Hepatic thiols and blood glutathione were decreased significantly in INH and RMP treated groups. Among antioxidative enzymes, hepatic superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferases (against CDNB and DCNB substrates) showed significant decline of activities in INH and RMP treated groups. The activities of hepatic glutathione reductase, glutathione-S-transferase (against EA substrate) and lipid peroxidation observed significant elevation. A careful comparison of protein and energy restriction revealed a greater degree of oxidative-stress of INH-RMP in protein-restriction.

Animals↗

Regional changes in 5-HT1A but not in 5-HT2A receptors in mouse brain after Semliki Forest virus infection: radioligand binding and autoradiographic studies.

Dysfunction of brain 5-hydroxytryptaminergic systems has been associated with several neurological and psychiatric diseases which may have a viral aetiology. The effect of Semliki Forest virus (SFV) on 5-hydroxytryptamine (5-HT1A and 5-HT2A) receptors in mouse brain has been assessed by membrane homogenate binding and autoradiography. Adult mice were injected with saline or virus and brains removed 2, 6, 14, 22 and 35 days after infection. 5-HT1A and 5-HT2A receptors were characterised by saturation studies using [3H] 8-OH-DPAT and [3H] Ketanserin respectively. SFV infection increased 5-HT1A receptor numbers by up to 80% in the cortex on days 6, 14, and 22 but had no effect on Bmax in the midbrain, pons/medulla and the hypothalamus. SFV infection did not affect 5-HT2A receptor number in any of the brain regions studied and the affinity (Kd) of either ligand for 5-HT1A or 5-HT2A receptors was unaffected. Autoradiographic mapping of 5-HT1A receptors in SFV-infected brain showed substantially higher binding in nucleus accumbens, tenia tecta, septohippocampal nucleus, septum, medial and basolateral amygdaloid nucleus, anterioventral preoptic nucleus, hippocampus, interpeduncular nucleus, frontal, lateral orbital, and entorhinal cortex and claustrum on days 6 and 14. Elevated binding persisted in tenia tecta, frontal, lateral orbital, entorhinal cortex, and hippocampal formation to day 22. Autoradiography of 5-HT2A receptors using [3H] Ketanserin showed no difference in the binding in SFV-infected brains. A decrease in plasma corticosterone levels in SFV-infected mice was observed on post infection days 6 and 22. These results show SFV infection induces a regionally selective upregulation of 5-HT1A but not 5-HT2A receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

Clinical assessment of nutritional status at birth.

OBJECTIVE: Clinical assessment of nutritional status of neonate using CAN score and comparison with other methods of determining intrauterine growth. DESIGN: Cross sectional study. SETTING: Tertiary care hospital. SUBJECTS: 637 consecutive, liveborn singleton neonates with known gestational age and no major congenital malformation. METHODS: Birth weight, length, midarm circumference and head circumference recorded in newborns. Ponderal index and mid arm to head circumference ratio was calculated. Clinical assessment of nutritional status was done on the basis of CAN score and compared with other methods. RESULTS: CAN score < 25 separated 60% of the babies as well nourished and 40% as malnourished. Weight for age and Ponderal Index classified 70-75% of babies as well nourished (AGA) and 25-30% as malnourished. Also MAC/HC classified nearly half the babies as well nourished and half as malnourished. CONCLUSION: CAN score may be a simple clinical index for identifying fetal malnutrition and for prediction of neonatal morbidity associated with it, without the aid of any sophisticated equipments.

Anthropometry↗

Relationship between acculturation and mental health for Asian Indian immigrants in the United States.

A community sample of Indian immigrants in the United States (N = 195) completed a survey to assess the relationship between acculturation and mental health. The relationship among several social and demographic variables, three aspects of acculturation (perception of acceptance, cultural orientation, and language usage), and three aspects of mental health (psychological distress, acculturative stress, and satisfaction) were examined. Multiple regression analyses were used to identify statistical predictors of a composite index of mental health. Results indicated that acceptance and cultural orientation play crucial roles in mental health, independent of various social and demographic variables. Feeling accepted by the host society and being involved with Americans and U.S. culture were related to better mental health.

Acculturation↗

Biomechanical evaluation of posterior and anterior lumbar interbody fusion techniques.

This study determined the biomechanical differences between anterior and posterior lumbar interbody fusion (ALIF and PLIF). Ten cadaveric spines were tested. Five specimens had ALIF and five had PLIF at L4-L5. Stabilization was performed with pedicle screws and rods (Cotrel-Dubboset, Sofamor-Danek, Memphis, TN, U.S.A.). Angular motion was measured in flexion, extension, bending, and torsion on the intact, instrumented, and "fused" specimens. Instrumentation alone caused a significant decrease in segmental motion in all loading modes (p < 0.01). After the simulated fusion procedures, all specimens were most stable in flexion, and significantly less stable in extension (p = 0.04). Comparing directly, ALIF was significant more stable in left torsion (p = 0.03) with trends in left bending (p = 0.08) and right torsion (p = 0.07). Thus, from a purely biomechanical perspective, ALIF appears to be slightly superior to PLIF.

Adult↗

Influence of gender on in-hospital clinical and angiographic outcomes and on one-year follow-up in the New Approaches to Coronary Intervention (NACI) registry.

Higher complication rates and lower success rates for treatment of women compared with men have been reported in prior studies of coronary angioplasty and in most early reports of outcome with new coronary interventional devices. In multivariate analysis this has been attributed largely to older age and other unfavorable clinical characteristics. These results are reflected in the current guidelines for coronary angioplasty. Women in prior studies have also had different distributions of vessel and lesion characteristics, but the influence of these differences on the outcome of new-device interventions have not been adequately evaluated. This article evaluates the influence of gender on clinical and angiographic characteristics, interventional procedure and complications, angiographic success, and clinical outcomes at hospital discharge and 1-year follow-up, as observed in the New Approaches to Coronary Intervention (NACI) registry. The NACI registry methodology has been reported in detail elsewhere in this supplement. This study focuses on the 90% of patients-975 women and 1,880 men-who had planned procedures with a single new device and also had angiographic core laboratory readings. Women compared with men were older, had more recent onset of coronary ischemic pain that was more severe and unstable, and had more frequent histories of other adverse clinical conditions. The distributions of several but not all angiographic characteristics before intervention were considered more favorable to angioplasty outcome in women. Differences were observed in device use and procedure staging. Angiographically determined average gain in lumen diameter after new-device intervention, with or without balloon angioplasty, was significantly less in women (1.38 mm) than in men (1.53 mm; p < 0.001); this 0.15 mm difference is consistent with the 0.16-mm smaller reference vessel lumen diameter of women. However, final percent diameter stenoses and TIMI flow and lesion compliance characteristics were similar. Among procedural complications, only treatment for hypotension, blood transfusion, and vascular repair occurred more often in women. More women than men were clinically unstable (2.1% vs 1.1%) or went directly to emergent coronary artery bypass graft surgery (CABG; 1.2% vs 0.6%) on leaving the interventional laboratory. However, in-hospital death (1.4% vs 1.1%), Q-wave myocardial infarction (MI) (0.9% vs 1.1%), and emergent CABG (1.5% vs 1.0%, for women and men, respectively) were not significantly different. Nonemergent CABG was more frequent in women (1.8% vs 0.9%; p < 0.05) and length of hospital stay after device intervention was longer (4.4 days vs 3.8 days in men; p < 0.01). In both univariate and multivariate analyses gender did not emerge as a significant variable in relation to the combined endpoint, death, Q-wave MI, or emergent CABG at hospital discharge. At 1-year follow-up more women than men reported improvement in angina (70% vs 62%) and fewer women than men had had repeat revascularization (32% vs 36%). Similar proportions were alive and free of angina, Q-wave MI and repeat revascularization (46% of women vs 45% of men). Although several procedure-related complications were more frequent in women than men after coronary interventions with new devices, no important disadvantages were observed for women in the rates of major clinical events at hospital discharge and at 1-year clinical follow-up. Additional studies are needed to evaluate the complex interplay of clinical, vessel, and lesion characteristics on success and complications of specific interventional techniques and to determine whether gender, per se, is a risk factor and whether gender specific interventional strategies may be beneficial.

Aged↗

Excimer laser coronary angioplasty: the New Approaches to Coronary Intervention (NACI) experience.

In the New Approaches to Coronary Intervention (NACI) registry, 887 patients were electively treated with excimer laser coronary angioplasty (ELCA) for coronary artery disease. The Advanced Interventional System (AIS) system was used in 487 cases; the Spectranetics system, in 400. The mean age was 63.4 years. Most patients had unstable angina (60.3%); 43.7% had a prior myocardial infarction; and 18.6% were high risk or inoperable patients. Mean ejection fraction was 55.4%. A total of 1,000 lesions were treated in the 887 patients. Of the 1,000 lesions treated with ELCA in the 887 patients, 36% were in the right coronary artery; 33%, left anterior descending; 13%, circumflex; 3%, left main; and 16.6%, vein graft. By angiographic core laboratory analysis available for 752 (85%) patients with 839 lesions, lesions were 12.76 mm long. The minimum lumen diameter increased to 1.29 mm after the laser and finally to 1.95 mm after adjunctive percutaneous transluminal coronary angioplasty (PTCA) (which was performed in 93% of all lesions), with a final residual stenosis of 32.1% and Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow in 95%. Dissections of grades B, C, or D were seen after 22.0% of initial laser attempts, and postlaser perforations were noted in 2.6%. Additional such dissections accumulated after adjunctive PTCA but the perforation rate remained low. Procedural success was achieved in 84% of patients, but 1.2% died, 0.7% experienced Q-wave myocardial infarction (MI), and 2.7% required emergency bypass surgery. Multiple logistic regression analysis could not identify any independent predictors of these in-hospital complications. One-year mortality was 5.7% and the cumulative incidence of Q-wave MI was 1.5%. Coronary artery bypass graft (CABG) surgery was performed in 15.0% of patients whereas 25.5% required repeat percutaneous intervention with a target lesion revascularization rate of 31%. Independent predictors of death, Q-wave MI, or target lesion revascularization (which, combined, occurred in 35.6% of patients) were the absence of prior MI, ELCA in the circumflex, perforation after the procedure, and small (<2 mm) final minimal lumen diameter. Considering the large number of patients with high-risk lesions, laser angioplasty was performed with excellent procedural success rates and a reasonable incidence of major complications.

Aged↗

Different effects of omeprazole and Sch 28080 on canine cerebrospinal fluid production.

We investigated the effects of omeprazole and Sch 28080, a more specific and a more potent inhibitor of K+,H+-ATPase than omeprazole, in canine cerebrospinal fluid (CSF) production. CSF production was measured by ventriculocisternal perfusion (VCP) technique in three groups (n = 10 in each group) of anesthetized, paralyzed and mechanically ventilated dogs. Group I served as control, Sch 28080 (10(-4) mol/l of synthetic CSF) was added to VCP in group II, and omeprazole (10(-5) mol/l of synthetic CSF) was added to VCP in group III, after baseline control CSF production had been determined at 15, 30, 45, and 60 min. Comparing the three groups, the mean baseline values for CSF production did not differ significantly. However, the percent decreases in CSF production in the omeprazole treated group were 26 +/- 17 and 24 +/- 13 at 210 and 225 min, which were significantly more than the respective values in the control group. Percent decrease in CSF production in Sch 28080 was not significantly different from that in the control group. We conclude that in the canine model, physiological doses of omeprazole decrease CSF production by about 26%. However, the effect is independent of the K+,H+-ATPase activity, since Sch 28080 which is more potent than omeprazole did not significantly affect CSF production.

Acid-Base Equilibrium↗

Acetylcholine, outer hair cell electromotility, and the cochlear amplifier.

The dominant efferent innervation of the cochlea terminates on outer hair cells (OHCs), with acetylcholine (ACh) being its principal neurotransmitter. OHCs respond with a somatic shape change to alterations in their membrane potential, and this electromotile response is believed to provide mechanical feedback to the basilar membrane. We examine the effects of ACh on electromotile responses in isolated OHCs and attempt to deduce the mechanism of ACh action. Axial electromotile amplitude and cell compliance increase in the presence of the ligand. This response occurs with a significantly greater latency than membrane current and potential changes attributable to ACh and is contemporaneous with Ca2+ release from intracellular stores. It is likely that increased axial compliance largely accounts for the increase in motility. The mechanical responses are probably related to a recently demonstrated slow efferent effect. The implications of the present findings related to commonly assumed efferent behavior in vivo are considered.

Acetylcholine↗