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Biomedical subjects

S M Prasad

Publications and source records attributed to S M Prasad.

16 recordsLinked to original sources
PubMed2001

Initial prospective multicenter clinical trial of robotically-assisted coronary artery bypass grafting.

BACKGROUND: This multicenter prospective trial was designed to assess the safety and efficacy of using a robotically-assisted microsurgical system to create endoscopic coronary anastomoses. METHODS: . Thirty-two patients scheduled for elective primary coronary surgery underwent endoscopic anastomosis of the left internal thoracic artery (LITA) to the left anterior descending (LAD) artery. Three thoracic ports (two for instruments and one for a camera) were placed, and a robotic system was used to perform the LITA-LAD graft. Conventional techniques were used to perform the other grafts. Thirty-one patients underwent median sternotomy and 1 patient underwent a limited anterior thoracotomy. RESULTS: . Graft flow was measured in the operating room and averaged 37 +/- 19 mL/min. Mean anastomosis time was 24 +/- 9 minutes. There were three intraoperative revisions (9%). Two were for inadequate flow and one for an inadvertent injury. Each of these grafts was successfully revised by hand. There were no technical failures of the robotic system. Average postoperative length of stay was 5.5 +/- 2.7 days. There were three reoperations for bleeding, but none of these were related to the LAD anastomosis. Two months following the operation, selective angiography revealed a graft patency of 93%. The patients have been followed for 16 +/- 4 months. CONCLUSIONS: This initial prospective multicenter trial documents the feasibility of robotically-assisted coronary bypass grafting. Further trials are warranted to establish the safety and efficacy of this new technology.

Aged↗
PubMed2001

Prospective clinical trial of robotically assisted endoscopic coronary grafting with 1-year follow-up.

OBJECTIVE: To follow up in prospective fashion patients with coronary artery anastomoses completed endoscopically with robotic assistance. The robotic system was evaluated for safety and its effectiveness in completing microsurgical coronary anastomoses. SUMMARY BACKGROUND DATA: Recently there has been an interest in using robotics and computers to enhance the surgeon's ability to perform endoscopic cardiac surgery. This interest has stemmed from the rapid advancement of technology and the desire to make cardiac surgery less invasive. Using traditional endoscopic instruments, it has not been possible to perform coronary surgery. METHODS: Nineteen patients underwent robotically assisted endoscopic coronary artery bypass grafting of the left internal thoracic artery (LITA) to the left anterior descending artery (LAD). Two robotic instruments and one endoscopic camera were placed through three 5-mm ports. A robotic system was used to construct the LITA-LAD anastomosis. All other required grafts were completed by conventional techniques. RESULTS: Seventeen LITA-LAD grafts (89%) had adequate intraoperative flow. The mean LITA-LAD graft flow was 38.5 +/- 5 mL/min. At 8 weeks, LITA-LAD grafts were assessed by angiography and showed 100% patency with thrombolysis in myocardial infarction (TIMI) I flow. At a mean follow-up of 17 +/- 4.2 months, all patients were NYHA class I and there were no adverse cardiac events. CONCLUSIONS: The results from the first prospective clinical trial of robotically assisted endoscopic coronary bypass surgery in the United States showed favorable short-term outcomes with no adverse events. Robotic assistance is an enabling technology allowing the performance of endoscopic coronary anastomoses.

Aged↗
PubMed2000

The role of cardioplegia induction temperature and amino acid enrichment in neonatal myocardial protection.

BACKGROUND: Warm cardioplegic induction improves the ischemically "stressed" adult heart. However, it is rarely used in infants, despite the fact that many newborn hearts are stressed by other factors such as hypoxia. The need for amino acids as well as their mechanism of action has also not been studied. METHODS: We first assessed the role of cardioplegic induction temperature in 10 nonhypoxic neonatal piglets undergoing 70 minutes of multidose blood cardioplegic arrest. Five piglets (group 1) received a cold (4 degrees C) induction, and 5 (group 2) a warm (37 degrees C) induction. Twenty-six other piglets underwent ventilator hypoxia (fraction of inspired oxygen, 8% to 10%) for 60 minutes before cardiopulmonary bypass (stress). Six piglets (group 3) then underwent 70 minutes of cardiopulmonary bypass without ischemia (hypoxia controls), and 20 underwent 70 minutes of cardioplegic arrest. Five of these (group 4) received cold cardioplegic induction, and 15 received warm induction; in 5 of these (group 5), the warm cardioplegic solution contained amino acids, in 5 others (group 6), it was unsupplemented, and in the remaining 5 (group 7), nitroglycerin was added to determine the role of vasodilation. Myocardial function was assessed by pressure-volume loops (expressed as a percent of control), and coronary vascular resistance was measured with cardioplegic infusions. RESULTS: In nonhypoxic (normal) piglets, cold (group 1) and warm (group 2) induction completely preserved systolic function (end-systolic elastance, 100% versus 104%) and preload recruitable stroke work (100% versus 102%), with minimal increase in diastolic compliance (162% versus 156%). Hypoxia-reoxygenation alone (group 3) depressed systolic function (end-systolic elastance, 51%+/-2%) and preload recruitable stroke work (54%+/-3%), and raised diastolic stiffness (260%+/-15%). The detrimental effects of reoxygenation persisted (unchanged from reoxygenation alone) with cold induction (group 4) or warm induction without amino acids (groups 6 and 7). In contrast, warm induction with amino acids (group 5) restored systolic function (end-systolic elastance, 105%+/-3%; p < 0.001 versus groups 3, 4, 6, and 7) and preload recruitable stroke work (103%+/-2%; p < 0.001 versus groups 3, 4, 6, and 7), and decreased diastolic stiffness (154%+/-7%; p < 0.001 versus groups 3, 4, 6, and 7). However, there was no difference in myocardial oxygen consumption in hypoxic hearts receiving a warm induction (6.9 versus 6.5 versus 7.3 mL/g per 5 minutes) (groups 5, 6, 7), and coronary vascular resistance was lowest with nitroglycerin (group 7). CONCLUSIONS: Cardioplegic induction can be given either warm or cold in nonhypoxic neonatal hearts. In contrast, only warm induction with amino acids repairs the hypoxic injury, but the primary mechanism of action is not related to increased metabolic activity or vasodilation.

Adenosine↗
PubMed1999

Follow-up study of survivors of severe protein energy manlnutrition.

OBJECTIVE: To evaluate the nutritional profile of survivors of severe protein energy malnutrition on follow-up at 1-3 years and 5-7 years. DESIGN: Prospective and Cross-sectional point prevalence. METHODS: Group I comprised 50 severely malnourished children dischared 5-7 years from nutritional rehabilitation center and Group II comprised 50 children discharged 1-3 years ago. The nutritional status of these 100 children was compared to the nutritional status of 35 siblings who had not suffered from severe malnutrition in their earlier life (Group III). RESULTS: All the malnourished children showed significant improvement in weight for age. More children in Group I had better height for age compared to Group II(p>0.05). Analysis of weight for height showed that study children has better nutritional status than their siblings who had not suffered from significant malnutrition. CONCLUSION: Significant improvement in nutritional status occurs with nutritional rehabilitation. However, improvement in height for age is more difficult to obtain. Interestingly, rehabilitated malnourished children on follow up had better nutritional status as compared to their siblings.

Body Height↗
PubMed1994

Structure and function of the xenobiotic substrate binding site of a glutathione S-transferase as revealed by X-ray crystallographic analysis of product complexes with the diastereomers of 9-(S-glutathionyl)-10-hydroxy-9,10-dihydrophenanthrene.

The three-dimensional structures of isoenzyme 3-3 of glutathione (GSH) transferase complexed with (9R,10R)- and (9S,10S)-9-(S-glutathionyl)-10-hydroxy-9,10-dihydrophenanthrene [(9R,10R)-2 and (9S,10S)-2], which are the products of the addition of GSH to phenanthrene 9,10-oxide, have been determined at resolutions of 1.9 and 1.8 A, respectively. The structures indicate that the xenobiotic substrate binding site is a hydrophobic cavity defined by the side chains of Y6, W7, V9, and L12 from domain I (the GSH binding domain) and I111, Y115, F208, and S209 in domain II of the protein. All of these residues are located in variable-sequence regions of the primary structure of class mu isoenzymes. Three of the eight residues (V9, I111, and S209) of isoenzyme 3-3 that are in direct van der Waals contact with the dihydrophenanthrenyl portion of the products are mutated (V9I, I111A, and S209A) in the related isoenzyme 4-4. These three residues are implicated in control of the stereoselectivity of the class mu isoenzymes. The hydroxyl group of Y115 is found to be hydrogen-bonded to the 10-hydroxyl group of (9S,10S)-2, a fact suggesting that this residue could act as an electrophile to stabilize the transition state for the addition of GSH to epoxides. The Y115F mutant isoenzyme 3-3 is about 100-fold less efficient than the native enzyme in catalyzing the addition of GSH to phenanthrene 9,10-oxide and about 50-fold less efficient in the Michael addition of GSH to 4-phenyl-3-buten-2-one. The side chain of Y115 is positioned so as to act as a general-acid catalytic group for two types of reactions that would benefit from electrophilic assistance. The results are consistent with the notion that domain II, which harbors most of the variability in primary structure, plays a crucial role in defining the substrate specificity of class mu isoenzymes.

Animals↗
PubMed1993

Reversible opening of the blood-brain barrier by anti-bacterial antibodies.

The leukocyte adhesion molecule CR3 (CD11b/CD18, Mac-1) promotes leukocyte transmigration into tissues by engaging an unknown cognate ligand on the surface of vascular endothelial cells. Filamentous hemagglutinin (FHA), an adhesin of the bacterium Bordetella pertussis, binds to CR3. We hypothesized that FHA mimics the native ligand for the CR3 integrin on endothelial cells and predicted that anti-FHA antibodies should bind to endothelial cells, interfere with leukocyte recruitment, and induce endothelial permeability. Anti-FHA monoclonal antibodies bound to cerebral microvessels in sections from human brain and upon intravenous injection into rabbits. Antibody binding correlated with the ability to recognize two polypeptides in extracts of human cerebral vessels that were also bound by CD18. In vivo, antibody binding not only interfered with transmigration of leukocytes into cerebrospinal fluid but also induced a dose-dependent reversible increase in blood-brain barrier permeability sufficient to improve delivery of intravenously administered therapeutic agents to brain parenchyma.

Animals↗
PubMed1993

Identification of a carbohydrate recognition domain in filamentous hemagglutinin from Bordetella pertussis.

The adherence of Bordetella pertussis to ciliated cells and macrophages is critical to colonization and infection of the respiratory tract. Adherence to both types of cells involves the recognition of eukaryotic carbohydrates by the bacterial adhesin filamentous hemagglutinin (Fha). The carbohydrate recognition domain (CRD) of Fha is considered an important antigen for subcomponent vaccines to maximize the generation of antiadherence antibodies capable of protecting against colonization. For identification of the CRD of Fha, a bank of eight monoclonal antibodies (MAbs) that mapped to four contiguous regions were tested for their ability to block Fha binding to lactosylceramide or to block bacterial binding to ciliated cells. Only MAb 12.5A9, which maps to amino acid residues 1141 to 1279, blocked both Fha binding to lactosylceramide and bacterial binding to ciliated cells. An 18-kDa polypeptide corresponding to this region was expressed in Escherichia coli. Cell lysates containing this protein bound to lactosylceramide in a manner identical to that of native Fha. Mutant strains of B. pertussis that contained an in-frame deletion of the coding sequence for this region produced a truncated Fha that showed negligible cross-reactivity with MAb 12.5A9. In an adherence assay, these mutant strains failed to bind efficiently to either ciliated cells or macrophages. The numbers of adherent bacteria for these strains were reduced to the number obtained with a nonadherent strain. We conclude that the region defined by residues 1141 to 1279 of Fha constitutes a CRD critical for bacterial adherence and represents a potential candidate for a subcomponent vaccine.

Adhesins, Bacterial↗
PubMed1992

Structure of RG-12561 dichloromethane solvate and a diastereomer.

(III): [4 alpha,6 beta(E)]-(+-)-6-(2-[2-(4-Fluoro-3-methylphenyl)- 4,4,6,6-tetramethyl-1-cyclohexen-1-yl]ethenyl)-4-hydroxytetrahy dro pyran-2-one (RG-12561) dichloromethane solvate, 2C24H31FO3.CH2-Cl2, Mr = 857.94, triclinic, Pl, a = 11.7413 (5), b = 13.0279 (5), c = 16.2332 (9) A, alpha = 99.456 (4), beta = 94.217 (4), gamma = 101.893 (4) degrees, V = 2381.9 (4) A3, Z = 4 [four molecules of (III)+two molecules of solvent per unit cell], Dx = 1.195 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 16.69 cm-1, F(000) = 912, T = 293 K, final R = 0.053, wR = 0.060 for 4031 reflections with I greater than 3 sigma(I). (IV): [4 beta,6 alpha(E)]-(+-)-6-(2-[2- (4-Fluoro-3-methylphenyl)-4,4,6,6-tetramethyl-1-cyclo-hexen-1-yl]e thenyl)-4- hydroxytetrahydropyran-2-one, C24H31FO3, Mr = 386.51, triclinic, Pl, a = 6.054 (2), b = 12.931 (2), c = 14.838 (3) A, alpha = 67.70 (2), beta = 85.75 (2), gamma = 82.85 (2) degrees, V = 1066.0 (8) A3, Z = 2, Dx = 1.203 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 6.86 cm-1, F(000) = 414, T = 293 K, final R = 0.073, wR = 0.081 for 1588 reflections with I greater than 3 sigma(I). (III) is a potent HMG-CoA reductase inhibitor and has the potential to function as a superior hypocholesterolemic agent; (IV) lacks this activity. (III) and (IV) have different conformations and molecular-model calculations suggest that crystal-packing effects are primarily responsible for the overall conformation of (IV). The principal intermolecular contacts are hydrogen bonds of the type O-H...O = C.

Anticholesteremic Agents↗
PubMed1991

Structure of thialysine hydrochloride.

2-Ammonio-3-[(2-ammonioethyl)thio]propionate chloride, C5H13N2O2S+.Cl-, Mr = 200.7, monoclinic, P2(1), a = 5.1275 (4), b = 7.897 (1), c = 11.208 (1) A, beta = 104.129 (8) degrees, V = 440.1 A3, Z = 2, Dx = 1.519 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 6.12 cm-1, F(000) = 212, T = 295 K, final R = 0.021, wR = 0.027 for 784 reflections with I greater than 3 sigma (I). The two ammonium cations form seven hydrogen bonds: alpha-NH3+ acts as a donor for three carboxylate O atoms and one Cl- ion whereas epsilon-NH3+ is linked to three Cl- ions.

Cysteine↗
PubMed1991

Structure of 3-methyl-1,2,3,4,5,6-hexahydro-1,6-methano-3-benzazocinium hydrogen oxalate.

C13H18N+.C2HO4-, Mr = 277.3, orthorhombic, P2(1)2(1)2(1), a = 5.752 (1), b = 15.502 (2), c = 15.910 (2) A, V = 1418.6 (6) A3, Z = 4, Dx = 1.298 g cm-3, Mo K alpha (lambda = 0.71069 A), mu = 1.01 cm-1, F(000) = 592, T = 295 K. Final R = 0.035, wR = 0.042 for 1003 reflections with I greater than 3 sigma(I). The compound is an ammonium hydrogen oxalate. Both O atoms of the ionized carboxyl group act as acceptors in the formation of two hydrogen bonds: (a) an N--H...O bond linking the cation and anion with N...O and H...O distances of 2.722 (4) and 1.78 (5) A and (b) a strong O--H...O bond linking a chain of oxalate ions along a with O...O and H...O distances of 2.578 (4) and 1.59 (6) A. The relative stereochemistry of the heterocyclic and aromatic rings in the cation is similar to that in morphine.

Analgesics, Opioid↗
PubMed1990

Structure of N',N'-dibenzylbenzohydrazide.

C21H20N2O, Mr = 316.4, monoclinic, P2(1)/c, a = 9.985 (2), b = 17.070 (3), c = 10.119 (2) A, beta = 95.99 (1) degree, V = 1715.3 A3, Z = 4, Dx = 1.225 g cm-3, Mo K alpha (lambda = 0.71069 A), mu = 0.82 cm-1, F(000) = 672, T = 295 K. Final R = 0.043, wR = 0.042 for 1139 reflections with I greater than 3 sigma(I). There is one hydrogen bond in the structure with N-H...O = 2.05 (4) and N...O = 2.923 (5) A.

Benzoates↗
PubMed1989

Structure of (+-)-threo-9,10,16-trihydroxypalmitic acid.

9,10,16-Trihydroxyhexadecanoic acid, C16H32O5, Mr = 304.4, triclinic, P1, a = 4.871 (1), b = 8.801 (1), c = 21.121 (2) alpha = 89.54 (1), beta = 84.88 (2), gamma = 76.35 (2) degrees, V = 876.14 (4) A3, Z = 2, Dx = 1.154 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 0.26 cm-1, F(000) = 336, T = 295 K. Final R = 0.055 for 1556 reflections with I greater than or equal to 3 sigma(I). The 16 C atoms form an all-trans zigzag chain. Each molecule is linked to seven neighboring molecules via eight possible hydrogen bonds with O...O distances varying from 2.591 (6) to 2.673 (3) A. Each carboxyl group is potentially hydrogen-bonded to the carboxyl and C16-OH groups of other molecules with O...O distances of 2.591 (6) and 2.644 (4) A. The conformation around the C9-C10 bond is gauche with an O3-C9-C10-O4 torsion angle of 66.4 (5) degrees.

Chemical Phenomena↗
PubMed1987

Role of the (acyloxy)methyl moiety in eliciting the adrenergic beta-blocking activity of 3-(acyloxy)propanolamines.

Some totally aliphatic 3-(acyloxy)propanolamines were synthesized with the aim of testing whether beta-blocking activity could be obtained from this class of drugs, even in the absence of an aromatic group. The significant and, in most cases, competitive beta-blocking activity shown by the compounds under examination, together with the results of a theoretical study in which their reactivity was compared with that of other adrenergic beta-blocking drugs, seems to confirm a hypothesis previously advanced on the basis of knowledge about the action mechanism of adrenergic beta-blocking drugs and of the results of structural studies. It was also possible to suggest some considerations about the role played by the (acyloxy)methyl portion of 3-(acyloxy)propanolamines in eliciting their adrenergic beta-blocking activity.

Adrenergic beta-Agonists↗
PubMed1985

Antitermination by both the promoter and the leader regions of an Escherichia coli ribosomal RNA operon.

RNA polymerase initiating at Escherichia coli ribosomal RNA promoter-leader regions can efficiently read through factor rho-dependent termination signals. Dissection of the promoter-leader region reveals that the ability to read through termination signals is conferred independently by both promoter and leader regions. Events in the leader also affect the transcription rate of structural genes downstream of the leader. When cells are grown in rich medium, the rrnC leader reduces transcription by a factor of approximately 4 when downstream of the rrnC promoters and by a factor of 2 when downstream of the lac promoter.

Base Sequence↗
PubMed1985

Chloramphenicol-erythromycin resistance mutations in a 23S rRNA gene of Escherichia coli.

Two chloramphenicol resistance mutations were isolated in an Escherichia coli rRNA operon (rrnH) located on a multicopy plasmid. Both mutations also confer resistance to 14-atom lactone ring macrolide antibiotics, but they do not confer resistance to 16-atom lactone ring macrolide antibiotics or other inhibitors of the large ribosomal subunit. Classic genetic and recombinant DNA methods were used to map the two mutations to 154-base-pair regions of the 23S RNA genes. DNA sequencing of these regions revealed that chloramphenicol-erythromycin resistance results from a guanine-to-adenine transition at position 2057 of the 23S RNA genes of both independently isolated mutants. These mutations affect a region of 23S RNA strongly implicated in peptidyl transfer and known to interact with a variety of peptidyl transferase inhibitors.

Base Sequence↗