PubMed Health⌕ Search

Biomedical subjects

S Bhat

Publications and source records attributed to S Bhat.

At least 73 records · Page 4Linked to original sources
PubMed1987

A clinical comparison of lidocaine and bupivacaine.

The drug of choice for local anesthesia in most emergency departments is lidocaine. However, it wears off shortly after suturing is complete and patients may experience pain after closure of the wound. We conducted a study to determine the degree of anesthesia obtained during and after repair of lacerations using lidocaine 1% versus bupivacaine 0.25%, a long-acting local anesthetic. Lidocaine and bupivacaine were administered in a double-blind, randomized fashion to 104 patients. Each patient was asked to rate his pain on a 0 to 10 scale (0, no pain; 10, severe pain) prior to administration of the anesthetic. They then rated pain on an identical scale at 30 minutes, and one, two, three, four, five, six, 12, 18, and 24 hours after completion of suturing. The mean baseline pain was 2.96 for the lidocaine group and 3.07 for the bupivacaine group. This decreased to less than 1.0 in both groups 30 minutes after infiltration. It remained low for the bupivacaine group for the next five hours, but increased almost to preanesthesia levels by two hours in the lidocaine group. A three-way analysis of variance revealed a significant difference (P less than .001) between the pain response of the two groups. There was no statistical difference (P greater than .05) between the age of the patients, size of laceration, and amount of drug used. The study shows that patients do experience pain after a wound is sutured and the anesthetic has worn off. It also demonstrates that bupivacaine significantly reduces the pain a patient may experience after repair of a wound.

Adult↗
PubMed1986

Renal effects of SK&F 82526 in anesthetized rats.

Dopamine affects renal hemodynamics, renal tubular functions, and the secretion of renin. We have studied the renal effects of SK&F 82526 (an agonist which is selective for the DA1 subclass of dopamine receptors) in anesthetized rats. Infused intravenously at 0.005 mumol/min/kg, this drug increased renal plasma flow and the clearances of PAH and insulin, effects which are consistent with decreased renovascular resistance. Concomitantly, urine flow and K excretion increased, and Na excretion tended to increase. All these effects of SK&F 82526 were antagonized by intravenous metoclopramide (1 mumol/min/kg). Despite its diuretic effect and despite its lack of effect on arterial blood pressure, SK&F 82526 increased arterial plasma renin concentration, suggesting a stimulatory effect on renin secretory rate. Taken together, our results demonstrate that the renal effects of SK&F 82526 mimic those of dopamine.

Animals↗
PubMed1986

Stimulation of oligodendrocytes by extracts from astrocyte-enriched cultures.

A soluble, heat-labile, trypsin-sensitive factor present in extracts of astrocyte-enriched cultures enhances the expression of myelination-associated events in rat brain cultures enriched in oligodendrocytes. Both the number of oligodendrocytes detected by immunofluorescence microscopy and the levels of biochemical activities associated with oligodendrocyte differentiation increased in the cultures in response to the extract in a time- and concentration-dependent fashion. The possible significance of these studies for normal oligodendrocytes function, and thus myelination, is discussed.

Animals↗
PubMed1986

Oligodendrocyte cell adhesion molecules are related to neural cell adhesion molecule (N-CAM).

The glycoproteins responsible for calcium-dependent oligodendrocyte aggregation were purified and characterized. Using detergent extraction, lentil-lectin-Sepharose 4B affinity chromatography, and preparative gel electrophoresis, 3 proteins were purified to apparent homogeneity, with relative Mrs of 120,000, 140,000, and 180,000. The aggregation assay showed that all 3 proteins had the ability to block antibody-mediated inhibition of oligodendrocyte aggregation. The 120,000 protein was the most active of the three. Antisera were raised in rabbits to these 3 individual proteins. Western blot analyses showed that all three antisera recognized 120,000, 140,000, and 180,000 proteins, which indicated that the proteins were related. Western-blot analyses of cultured oligodendrocytes and purified rat myelin showed only the 120,000 protein. Immunoprecipitation of iodinated membrane proteins of cultured oligodendrocytes also indicated the presence of only the 120,000 Mr protein. Deglycosylation of the 120,000 protein by N-glycanase resulted in a 110,000 protein. The immunoblot pattern suggested some similarities between oligodendrocyte adhesion molecules and the neural cell adhesion molecule (N-CAM). Therefore, the 120,000, 140,000, and 180,000 Mr proteins were compared to N-CAM by Western-blot analysis, immunofluorescence staining, and by immunoprecipitation. The results suggest that oligodendrocytes contain a 120,000 membrane glycoprotein that is related to N-CAM.

Animals↗
PubMed1985

Rat oligodendrocytes have cell adhesion molecules.

The aggregation of isolated oligodendrocytes appears to be mediated by cell adhesion molecules. The cell adhesion molecules are inactivated by trypsin. Regeneration of the adhesion molecules is prevented by inhibitors of either protein synthesis or glycosylation. An immunological assay is described to quantitate the molecules involved in oligodendrocyte adhesion based on the following criteria: (a) treatment of oligodendrocytes with rabbit immunoglobulins against oligodendrocyte-conditioned medium prevented their aggregation; and (b) incubation of these immunoglobulins with oligodendrocyte-conditioned medium neutralized their ability to inhibit aggregation.

Animals↗
PubMed1985

Comparison of intraosseous, central, and peripheral routes of sodium bicarbonate administration during CPR in pigs.

Obtaining venous access continues to be one of the most difficult problems faced by a physician caring for the pediatric patient in cardiac arrest. Our study examined the use of the intraosseous route (through the bone) to obtain venous access for sodium bicarbonate administration in a cardiac arrest model. Ventricular fibrillation was induced in 23 domestic swine. Cardiopulmonary resuscitation was performed for five minutes and sodium bicarbonate (1 mEq/kg) was administered through a peripheral IV line (n = 6), a central IV line (n = 5), or intraosseously (n = 6). Controls (n = 6) did not receive bicarbonate. Blood pH was sampled every two minutes for 30 minutes from the right ventricle, left ventricle, and femoral artery. An analysis of variance revealed that the central and intraosseous routes were significantly different (P less than .05) from the peripheral group, and that all three groups were significantly different (P less than .05) from the control. Pathology studies revealed only minor damage to bone when sodium bicarbonate was administered intraosseously. These data demonstrate that the intraosseous route is a rapid and effective alternative for venous access in a cardiac arrest model.

Animals↗
PubMed1985

Subcellular distribution and developmental expression of cholesterol ester hydrolases in fetal rat brain cultures.

Cholesterol ester hydrolase activities previously have been identified in brain and linked to the production of myelin, which has very low levels of esterified cholesterol. We have studied two cholesterol ester hydrolase activities (termed the pH 6.0 and pH 7.2 activities) in cultures derived from 19- to 21-day-old dissociated fetal rat brains and in developing rat brain. In vivo the levels of both the pH 6.0 and pH 7.2 activities began to increase by about 10 postnatal days, reached maximal levels at 20 days (20 and 1.5 nmol/h/mg protein, respectively), and thereafter remained nearly constant (pH 6.0) or decreased somewhat before becoming constant (pH 7.2). In contrast, in the cultures the pH 6.0 cholesterol ester hydrolase activity was low until 21 days in culture (DIC; 20 nmol/h/mg protein), increased to a peak activity at 31 DIC (60 nmol/h/mg protein), remained high for 24 days, and finally decreased (18 nmol/h/mg protein at 63 DIC); the pH 7.2 cholesterol ester hydrolase activity was very low until 20 DIC, increased to a peak activity at 31 days (3 nmol/h/mg protein), and thereafter decreased to a lower level (2 nmol/h/mg protein) that was maintained for about 24 days before decreasing (0.7 nmol/h/mg protein at 63 DIC). Therefore, the time courses of appearance of both cholesterol ester hydrolase activities were delayed by 10-14 days relative to that seen in vivo, and the specific activities observed in the cultures were transiently two- to three-fold higher than in rat brain, but then declined to levels characteristic of whole brain homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The isolation and long-term culture of oligodendrocytes from newborn mouse brain.

Using differential adhesion we successfully isolated relatively pure populations of mouse oligodendrocytes which can be maintained in vitro for more than two months. The highest percentage of galactocerebroside (GalC)-positive oligodendrocytes was 95% at 3 days after isolation. Thereafter, proliferation of astrocytes and fibroblasts occurred more quickly than did oligodendrocyte precursor division. GalC-positive oligodendrocytes rarely incorporate [3H]thymidine so that the use of a mitotic inhibitor (5 X 10(-6)M AraC) reduced the number of non-oligodendrocytes so as to maintain the purity of oligodendrocytes at more than 75% for 14 days in culture. This system will be of use for immunological and virological studies which require viable cultured mouse oligodendrocytes.

Animals↗
PubMed1981

Noncoordinate regulation of myelinogenic parameters in primary cultures of dissociated fetal rat brain.

The developmental regulation of sulfogalactosylceramide (sulfatide) synthesis, 2', 3'-cyclic nucleotide-3'-phosphohydrolase activity (CNP), and myelin basic protein (MBP) accumulation, three markers characteristic of myelinogenesis, were observed in dispersed cultures of fetal rat brain in spite of the absence of the formation of compact, multilamellar myelin. Sulfatide synthetic rate and CNP activity began to increase by 8 days in vitro (DIV) (approximately comparable to days post-natal) and reached their maxima by 20 DIV. MBP began to accumulate after 14 DEV and reached a maximum by 38 DIV. Thus, the temporal regulation of the onset of expression of these parameters, which is coordinate in vivo, has been dissociated into two sequential periods in vitro. Similarly, the regulatory mechanisms controlling the subsequent decline of the net expression of these three parameters were dissociated. Whereas, the increase in the net CNP activity ceased on schedule, the decline of sulfatide synthetic rate was delayed 20 days, and the accumulation of MBP underwent a net loss. These data suggest that there are multiple parallel but separate mechanisms of temporal regulation controlling myelinogenic gene expression, and that, among them, those factors that control MBP accumulation are more sensitive to disruption by the rigors of dissociated culture.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1981

Requirement for nonoligodendrocyte cell signals for enhanced myelinogenic gene expression in long-term cultures of purified rat oligodendrocytes.

Comparisons have been made of myelinogenic activities in fetal rat brain mixed primary cultures and cultures of isolated oligodendrocytes of comparable age. The specific activities of the sulfatide synthesis, 2',3'-cyclic-nucleotide 3'-phosphohydrolase (2',3'-cyclic-nucleotide 3'-phosphodiesterase, EC 3.1.4.37), and accumulation of myelin basic protein, when expressed per mg of protein, were as high (or generally higher) in isolated oligodendrocyte cultures as in comparable mixed primary cultures at 29 days. However, when these data were analyzed per oligodendrocyte, it became apparent that the isolated oligodendrocytes were substantially less active than their mixed culture counterparts. The results suggest the necessity of nonologodendrocyte positive signals for the optimal expression by oligodendrocytes of myelin-related differentiated functions. The isolation method involves the selection of oligodendrocytes by shaking them from primary cultures of rat brain, followed by the lysis of other contaminating cells in a balanced salt solution at pH 7.2. More than 99% of the isolated cells are viable, at least initially divide, and can be cultured for at least 60 days. The oligodendrocytes selected in this way were characterized by: (i) morphology, (ii) immunofluorescence labeling by antibodies to myelin basic protein and galactosylceramide, and (iii) biochemical analyses for myelin basic protein, activity of 2',3'-cyclic-nucleotide 3'-phosphohydrolase, and sulfogalactosylceramide synthesis.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMedDate not supplied

Effect of re-using nickel-chromium alloy on its ultimate tensile strength, yield strength and modulus of elasticity.

In order to bring down the cost of the castings used in fixed partial denture prosthesis, a study was conducted by reusing the nickel chromium alloy without adding any new material. We studied the effect on the ultimate tensile strength, yield strength and modulus of elasticity after reusing the nickel-chromium alloys. Results showed degenerative changes in the properties evaluated after recasting. These changes were statistically significant, suggesting that it can not be reused.

Chromium Alloys↗
PubMedDate not supplied

Stress variations in recast Ni-Cr alloy--a finite element analysis.

A finite element analysis was carried out to analyse the stress variations in a mandibular posterior fixed partial denture (FPD), made of recast nickel-chromium alloy. A two dimensional finite element model was developed and then analysed with STAAD III/ISDS program with an occlusal load of 1 kg applied to the casting surface. The analysis revealed that the connectors experienced maximum stresses and the generated stress values decreased within the fixed partial denture made of recast Ni-Cr alloy. It seemed unlikely that FPD inspite of being made of recast alloy might fail before the other tissue components show signs of degeneration thus establishing the potential for recycling the Ni-Cr alloy in actual dental practice.

Bite Force↗
PubMedDate not supplied

In vitro evaluation of ceramometal bond strength in anterior metal ceramic crowns with and without palatal coverage of porcelain.

This in vitro study compared the load necessary to cause porcelain bond failure on porcelain covering the labial and palatal surfaces compared with porcelain covering only labial surface in metal ceramic crowns of maxillary anterior teeth. 30 metal ceramic crowns for maxillary central incisor tooth were fabricated in two groups (Groups A and Group B) (15 samples in each group). In group A, palatal ceramo-metal junction was placed at cervical 1/5th of palatal surface. In Group B the palatal ceramo-metal junction was placed at palato incisal line angle and these crowns were subjected to load using Instron testing machine. Mean failure load for group A is statistically highly significant than Group B. (P value = 0.0025). But both these values are higher than the reported mean maximal incising forces.

Bite Force↗
PubMedDate not supplied

Comparative evaluation of tensile bond strength of denture base resins to surface pretreated cobalt chromium base metal alloys--an in vitro study.

This study was undertaken to evaluate the tensile bond strength of acrylic resins to surface pretreated Cobalt-chromium base metal alloy. A total of 60 tensile bar specimens were prepared. One half of the bar was cast in cobalt-chromium alloy and the other half made of denture base resins attached to the alloy following surface pretreatment. Two denture base resins and five surface pre-treatments were used which included sandblasting, acid etching, use of metal adhesive primers and the combination of the above mentioned modes. Gradual axial loads were applied on the tensile bar specimen mounted on a Hounsfield tensometer till bond failure was evident. Statistical evaluation was done using Mann-Whitney U test. The study results indicate that the bond strength in those specimens wherein a combination of sandblasting, acid etching and priming was done as surface pretreatment, showed the maximum values as compared to the other groups.

Acid Etching, Dental↗
PubMedDate not supplied

Evaluation of the polished surface characteristic of cobalt-chrome castings subsequent to various finishing and polishing techniques.

Finishing and Polishing constitutes an essential requisite after the fabrication of removable partial dentures. Improper finishing and polishing of cast framework will adversely affect the quality of functional units of partial dentures due to reduced dimensions. In this study the polished surface characteristic and loss of weight of the casting were evaluated and compared following different finishing and polishing techniques. A total number of thirty test specimens were cast and each surface finishing and polishing technique was carried out with a high speed polishing motor and an electropolishing unit under standardised conditions. Surface roughness was evaluated by means of a surface roughness analyzing instrument, Perthometer. The loss of weight due to the metal lost was observed on a sensitive electronic balance. The results of polishing technique employed with G3 group revealed better surface characteristic. It may be understood that sandblasting causes initial roughness and the sequence of coarse cylindrical abrasive, Black hard rubber polisher (coarse grit-Dentauram), Grey hard rubber polisher (Med-grit-Dentauram), Green hard rubber polisher (Fine-grit-Dentauram), Grey flexible rubber polisher (Fine grit-Renfert), felt buff with pumice slurry and felt buff with green polishing compound (Degussa) produced improved surface in this case. The loss of weight due to metal lost show concern with technique groups G4, G5, G6. It can be avoided by judicious sandblasting and application of proper grit of abrasive agents.

Analysis of Variance↗