Combined chemotherapy and radiation in the treatment of a large nasal cavity tumor: a case report.
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Aged↗
Biomedical subjects
K Narayanan
Publications and source records attributed to K Narayanan.
Comparative clinical study of the sure-closure device with conventional wound closure techniques.
The Sure-Closure device, designed for wound closure, harnesses the viscoelastic properties of the skin. It has been used in clinical studies in the past. We have evaluated the role of this device in complex wound problems and compared it to closure achieved by conventional wound closure methods such as skin grafts and flaps. A total of 40 patients with multiple wound etiologies were examined. We used the device under local and general anesthesia. In addition, we performed cost analysis on the use of the device and compared this to traditional methods. We found a cost reduction trend associated with the Sure-Closure method (p < .05). All of the 24 patients in whom the device was used to close the wounds had complete primary closure. The device is also easy to use. When used for delayed stretching, as in some of our patients, the compliance rate was high.
Adolescent↗
Evaluation of autogenous tissue breast reconstruction using MRI.
Recent controversy encountered with silicone breast implants has increased the use of autogenous tissue for breast reconstruction following mastectomy. Surveillance of patients who have undergone autogenous tissue reconstruction is important in the evaluation of recurrent or new cancer. Magnetic resonance imaging (MRI) has proven to be a useful technique in the delineation of soft tissues and provides excellent resolution. Recently, MRI has been reported to be a valuable diagnostic imaging modality for the evaluation of augmented breast implant patients with regard to implant rupture detection, silicone granuloma identification, and silicone gel migration delineation. In this study, various autologous tissue donor sites currently available for breast reconstruction were imaged by MRI. The following donor flaps were included: fleur-de-lis, TRAM, gluteal, and tensor fasciae latae. A total of 10 clinical cases were investigated. The anatomic basis of each flap type is illustrated, and various tissue components of flap tissue (skin, fat, and muscle) are demonstrated on MRI scan. Anatomic knowledge of autogenous tissue types and MRI appearance of the flap-breast-chest-wall interface are critical in the surveillance and follow-up of breast cancer patients.
Breast↗
Characterization of the effects of two new arginine/citrulline analogues on constitutive and inducible nitric oxide synthases in rat aorta.
1. New potent inhibitors of nitric oxide synthase (NOS) may be useful in the treatment of septic shock, a disorder characterized by a vascular hyporeactivity to catecholamines caused by an overproduction of nitric oxide (NO-). We examined the effects of L-thiocitrulline (L-TC) and S-methyl-L-thiocitrulline (L-SMTC), novel NOS inhibitors, on the constitutive and inducible NOS in rat aorta and compared those effects with inhibition due to NG-methyl-L-arginine (L-NMA). 2. Phenylephrine evoked similar concentration-contraction curves in the control rings and in the rings treated with these different NOS inhibitors (10 microM), whereas 100 microM of L-NMA, L-TC or L-SMTC increased significantly, and to a similar extent, contractions evoked by phenylephrine in aortic rings with endothelium without significantly affecting the maximal responses. 3. Relaxations evoked by acetylcholine, adenosine triphosphate, or calcium ionophore were significantly inhibited in a dose-dependent manner by L-NMA, L-SMTC, or L-TC (10-100 microM). The potencies of these inhibitors in reducing the relaxations of these vasodilators were not significantly different. 4. In endotoxin-treated preparations with endothelium, the three L-arginine analogues (10 microM) significantly potentiated contractile responses to phenylephrine (pEC50: 6.73 +/- 0.12 and 7.3 +/- 0.12, 7.34 +/- 0.13, or 7.22 +/- 0.14; in the absence and the presence of L-NMA, L-TC, or L-SMTC respectively) and increased maximal contractions from 1.53 +/- 0.15 g to 1.95 +/- 0.13 g, 2.08 +/- 0.12 g, and 2.03 +/- 0.13 g with L-NMA, L-TC, and L-SMTC respectively. A higher concentration of these NOS inhibitors (100 microM)further increased contractions evoked by this alpha1-agonist without further enhancing the maximal contractions; however, contractions evoked by 10 nM phenylephrine were significantly greater in the presence of L-SMTC or L-TC than in the presence of L-NMA (100 microM) (L-NMA: 0.4 +/- 0.11 g; L-TC:0.78 +/- 0.14 g and L-SMTC: 0.82+/-0.17 g). The effects of these inhibitors on NO- synthesis induced by endotoxin were significantly reversed by addition of L-arginine (1 mM) but not by L-citrulline (1 mM). InLPS-treated rings with endothelium, all three NOS inhibitors (100 microM) shifted the concentration contraction curves evoked by phenylephrine significantly to the left (pEC5o: 7.19 +/- 0.03 and 7.79 +/- 0.08,8.01 +/- 0.07, or 8.02 +_ 0.07, in the absence and the presence of L-NMA, L-TC, or L-SMTC, respectively)and increased significantly maximal contractions from 2.05 +/- 0.05 g to 2.38 +/- 0.14 g, 2.5 +/- 0.12 g, and 2.4 +_ 0.21 g with L-NMA, L-TC, and L-SMTC, respectively. L-TC and L-SMTC were significantly more potent than L-NMA in potentiating contractions evoked by 10 nM and 30 nM phenylephrine.5. L-TC and L-SMTC produced dose-dependent increases in tone in LPS-treated aortic rings with and without endothelium. In LPS-treated rings with endothelium, L-NMA induced contractions but in preparations without endothelium low concentrations of L-NMA induced small contractions while high concentrations of this inhibitor evoked relaxations. In both preparations L-TC and L-SMTC were significantly more potent than L-NMA in increasing vascular tone.6. These results suggest that L-SMTC, L-TC and L-NMA were equipotent on basal and agonist stimulated NO- synthesis produced by the constitutive isoform of NOS, whereas the two new L-arginine analogues were more potent than L-NMA in inhibiting the production of NO- induced by endotoxin in rat aorta.
Acetylcholine↗
L-thiocitrulline. A stereospecific, heme-binding inhibitor of nitric-oxide synthases.
Nitric-oxide synthase (NOS) catalyzes the oxidation of L-arginine to citrulline and nitric oxide (NO). The enzyme is inhibited by a variety of N omega-monosubstituted L-arginine analogs, and some of these compounds are useful in reversing pathologies associated with the overproduction of NO (e.g. the hypotension of septic shock). We report here that L-thiocitrulline (gamma-thioureido-L-norvaline) is a potent, stereospecific inhibitor of the constitutive brain and endothelial isoforms of NOS as well as the isoform induced in vascular smooth muscle cells by lipopolysaccharide and interferon-gamma. Steady state kinetic studies show L-thiocitrulline inhibition is competitive with L-arginine (Ki approximately 4-20% of KArgm), indicating that initial binding is as a substrate/product analog. In contrast to L-arginine and N omega-methyl-L-arginine, the prototypic NOS inhibitor, L-thiocitrulline binding elicits a "Type II" difference spectrum, indicating a high spin to low spin transition of the iron in the heme cofactor. This finding suggests that L-thiocitrulline is contributing the sixth ligand to heme iron, probably through the thioureido sulfur. Such interaction with heme iron neither stimulates nor inhibits the direct flavin-mediated cytochrome c reduction activity of the enzyme, but it does inhibit heme-dependent superoxide formation. In vivo, L-thiocitrulline is a potent pressor agent in both normal and endotoxemic rats, the latter finding suggesting utility in treating the hypotension of septic shock.
Amino Acid Oxidoreductases↗
Synthesis of L-thiocitrulline, L-homothiocitrulline, and S-methyl-L-thiocitrulline: a new class of potent nitric oxide synthase inhibitors.
Nitric oxide synthase catalyzes the NADPH- and O2-dependent conversion of L-arginine to L-citrulline and nitric oxide. L-Thiocitrulline, L-homothiocitrulline, and S-methyl-L-thiocitrulline, novel citrulline analogs, have been synthesized and are shown to be potent inhibitors of both the constitutive brain and the inducible smooth muscle isoforms of nitric oxide synthase. Although many N omega-monosubstituted arginine derivatives inhibit nitric oxide synthase, inhibitory citrulline derivatives have not previously been reported. S-Methyl-L-thiocitrulline is significantly more potent than N omega-methyl-L-arginine, the prototypic nitric oxide synthase inhibitor.
Amino Acid Oxidoreductases↗
Cryopreserved microvascular conduits: current applications and future prospects.
Modern cryopreservation techniques have resulted in the clinical use of cryopreserved allograft heart valves and large diameter veins. In addition to these large vascular tissues, there is a need for small-diameter vascular allografts. We review our studies of cryopreserved rat microvenous allografts (1 mm diameter) in both the arterial and venous systems. The clinical utilization of cryopreserved allografts in reconstructive microsurgery and the potential problems associated with the use of allogeneic tissues will be addressed. Further applications for vascular cryopreservation in reconstructive surgery include small-diameter arteries, vascularized tissue flaps, and limbs.
Animals↗
Closure of large postradiation vesicovaginal fistula with rectus abdominis myofascial flap.
We report the case of a patient who developed a large radiation-induced vesicovaginal fistula. She also had a paucity of the omentum due to previous laparotomy and adhesions. We were able to treat this patient successfully with a pedicled myofascial rectus abdominis flap.
Female↗
In vivo anatomic study of cutaneous perforators in free flaps using magnetic resonance imaging.
Adequate knowledge of perforator location preoperatively will enable the surgeon to achieve optimal flap design and flap survival. Most previous attempts have relied on the use of Doppler ultrasound and earlier anatomic knowledge. With ultrasound, there may at times be signals from overlapping blood vessels. Magnetic resonance imaging (MRI) is sensitive to flowing blood and, on an MRI scan, dark-flow void characterization is used to identify perforators. This study was undertaken to evaluate the anatomic location and the number of perforators in the flap zone, based on inherent blood flow, and to determine information about the dominant perforators for free-flap design, using MRI. The CSMEMP technique allowed the characterization of flow void signals, which appeared in the image as dark spots. This technique also enabled differentiation of the surrounding tissue, with a high degree of accuracy. The relationship of the perforators aided in an "ideal" flap design. No necrosis was noted in any of these cases. It appears from this study that MRI can be a useful imaging modality, to assess the location and number of perforators in musculocutaneous flaps.
Adult↗
The use of cryopreserved venous allografts in microvascular surgery without immunosuppression: an experimental study.
Excellent patency rates are currently established in the use of autogenous veins as interposition vein grafts in microsurgical practice. Allografts may be a viable alternative source of vein grafts. Recent advances in cryobiology have enabled the controlled freezing of tissues with preservation of vital cellular elements. Although several reports have shown the successful use of cryopreserved large-vessel allografts, few have addressed cryopreservation of microvessels (1 to 2 mm in diameter). In this study, the authors have successfully cryopreserved femoral veins in a rat model and transplanted them as interposition vein grafts into arterial defects across major histocompatibility barriers (ACI to Lewis). Short-term patencies (21 days) were determined, and histologic and scanning electron microscopic analysis were performed. Patency of 100 percent was achieved in both fresh control veins and in cryopreserved veins at 21 days.
Animals↗
Definitive diagnosis of breast implant rupture using magnetic resonance imaging.
Breast implant rupture is an important complication of augmented and reconstructed breasts. Although several techniques such as mammography, xeromammography, ultrasound, thermography, and computed tomographic (CT) scanning have been proven to be useful to detect implant rupture, they have several disadvantages and lack specificity. In the current study, we have established magnetic resonance imaging (MRI) as a definitive, reliable, and reproducible technique to diagnose both intracapsular and extracapsular ruptures. The study was conducted in 100 symptomatic patients. Our imaging parameters were able to identify ruptures in implants with silicone shells. All the ruptures showed the presence of wavy lines, free-floating silicone shell within the gel ("free-floating loose-thread sign" or "linguine sign"). We had a 3.75 percent incidence of false-positive and false-negative results. The sensitivity for detection of silicone implant rupture was 76 percent, with a specificity of 97 percent. In addition, we also were able to identify the artifacts that may interfere with the definitive diagnosis of implant rupture.
Adult↗
The permeability of tissue expanders to bacteria: an experimental study.
Infection is an occasional but serious complication of tissue expansion. Bacteria in many cases are found both inside and outside the expander. The mechanism of how they spread inside and out is not fully understood. In the current study, we have assessed both the expander membranes (n = 28) and the port (n = 42) in terms of leakage and transmission of Staphylococcus aureus in normal expansion (100 percent) and overexpansion (400 percent) in an in vitro model. Our results indicate that the membrane was impermeable to S. aureus, whereas the bacteria were able to migrate freely through the puncture sites in the ports.
Cell Membrane Permeability↗
Molecular yardsticks. Rigid probes to define the spatial dimensions of the benzodiazepine receptor binding site.
A series of rigid planar azadiindoles (8a, 8b, and 8d), benzannelated pyridodiindoles (11a, 11b, and 11d), and indolopyridoimidazoles (11c, 20, and 24) were synthesized from 4-oxo-1,2,3,4-tetrahydro-beta-carboline 5 via the Fischer indole cyclization with the appropriate arylhydrazines. These analogues were employed as probes ("molecular yardsticks") to define the spatial dimensions of the lipophilic regions of the benzodiazepine receptor (BzR) binding cleft. Benzannelated indoles 11a-d and indolopyridoimidazoles 20 and 24 were important in establishing an area of negative interaction (S1, see Figure 6, part b) in the binding cleft common to the interactions of both inverse agonists and agonists. Data from this chemical and computer-assisted analysis of the pharmacophore (see Figure 6) indicates that inverse agonists and agonists bind to the same binding region, but the pharmacophoric descriptors required for the two activities are different, in keeping with previous studies with these planar ligands. However, the hydrogen bond donating site H1 and the lipophilic region L1 in the receptor binding site are common interactions experienced by both series of ligands. The low affinities of both indolo[3,2-c]carbazole (3a) and indolo[3,2-b]isoquinoline (3b) for the BzR are consonant with the requirements of a hydrogen bond acceptor interaction at donor site H1 and a hydrogen bond donor interaction at acceptor site A2 for potent inverse agonist activity in the beta-carboline series. The hydrochloride salts of 1-aza- 8a (IC50 10.6 nM), 2-aza- 8b (IC50 51.5 nM), and 4-azadiindole 8d (IC50 11.2 nM) were found to be much more soluble in water than the corresponding salt of the parent diindole 2. Moreover, aza analogues 8a and 8b were shown to be partial inverse agonists with proconvulsant potencies comparable to that of the parent diindole 2.
Animals↗
Lower extremity reconstruction using a long-cryopreserved venous allograft for free flap venous outflow.
Vein grafts are used frequently in microvascular surgery, but an adequate supply of autogenous veins is not always available. The search for an ideal substitute for autogenous vein continues. We present a case of lower extremity reconstruction made difficult by lack of suitable autogenous vein for venous outflow from a rectus abdominus free flap. A 36 cm cryopreserved allograft saphenous vein was used on an emergency basis for this problem.
Aged↗
Experimental endoscopic subcutaneous surgery.
Endoscopic techniques have found increasing applications in general surgery. In this article, an attempt has been made to utilize endoscopy via a subcutaneous approach in an experimental pig model for dissection of fat, muscle, and fascia.
Adipose Tissue↗
The use of high-frequency ultrasound for the dissection of small-diameter blood vessels and nerves.
The Cavitron ultrasonic surgical aspirator has been successfully used in general surgery and neurosurgery. We have explored its use in the dissection of small-diameter blood vessels and nerves (1-2 mm) in a rat model. Our results seem to indicate that this technique may be useful in isolating blood vessels surrounded by fatty tissue without damage to the vessel itself. In this study, however, high-frequency ultrasound did cause significant damage to peripheral nerves.
Animals↗
Experimental tracheal replacement using a revascularized jejunal autograft with an implantable Dacron mesh tube.
Defects comprising more than 50% of the trachea cannot be reliably reconstructed by any current technique or prosthesis. A composite tracheal replacement implant consisting of a Dacron-urethane mesh tube and revascularized jejunal autograft was applied to this problem. This composite implant was used to replace 7 to 10 cm of trachea in eight dogs. The implant was sewn to the outside (serosal surface) of the jejunum to provide permanent structural support to the autograft, and an intraluminal silicone tube was placed inside the jejunal segment and left for 4 weeks following reconstruction. Six of eight animals survived the predetermined time periods and were killed painlessly in groups of two animals at 1, 2, and 6 months after removal of the intraluminal silicone tube. Postoperative intubation, ventilation, or tracheostomy was not necessary. Excessive secretions were not seen in any of the animals, and a fair to good performance status was maintained until death in all but one animal. Histologic examination revealed slight thinning of the jejunal mucosa, with no change in the jejunal muscularis. These data suggest that with further refinement this composite implant may be a viable reconstructive option in humans.
Animals↗
Evaluation of facial fat distribution using magnetic resonance imaging.
Magnetic resonance imaging (MRI) provides noninvasive images of facial and neck fat for a variety of conditions. It accurately maps the soft tissues pre- and postoperatively, enabling surgeons to precisely and objectively assess results of soft tissue facial contouring and fat transplantation. The risks of MRI are few. It has the potential to provide aesthetic surgeons with a more "scientific" means of comparing various techniques of fat contouring.
Adipose Tissue↗