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Biomedical subjects

N Surendran

Publications and source records attributed to N Surendran.

14 recordsLinked to original sources
PubMed2004

Left over bowels: an unique complication in a surviving twin.

Conjoint twins have always been a surgical challenge. The authors report an unusual finding in a surviving epigastric heteropagus twin. A 17 year old boy who underwent laparotomy for acute intestinal obstruction revealed a blind ending but complete duplication of the large bowel and an accessory liver in the falciform ligament, along with a separate gall bladder but with fused bile ducts. The findings suggest that the duplicated bowel loop and the accessory liver were remnants of the incomplete parasite twin, assimilated into the body of the autosite, which remained asymptomatic for 17 years. This case is being reported because of the uniqueness of the finding.

Adolescent↗
PubMed1999

Evidence for overlapping substrate specificity between large neutral amino acid (LNAA) and dipeptide (hPEPT1) transporters for PD 158473, an NMDA antagonist.

PURPOSE: The objective of this research was to investigate the substrate specificity of large neutral amino acid carrier (LNAA) and di/tripeptide (hPEPT1) transporters with respect to PD 158473, an NMDA antagonist. METHODS: Cellular uptake studies were carried out using two types of Chinese Hamster Ovary (CHO). CHO-K1 cells represent the wild type with inherent large neutral amino acid (LNAA) activity. CHO-PEPT1 cells were generated by stable transfection of hPEPT1 gene into CHO cells. Therefore, these cells possess both LNAA activity and di/tripeptide transporter activities as a result of the transfection. Cellular uptake of PD 158473 was quantified using a HPLC method previously developed in our laboratory. RESULTS: The utility of the CHO-PEPT1 cell model was demonstrated by determining the uptake kinetics of Gly-Sar, a prototypical dipeptide transporter substrate. Uptake kinetics of PD 158473 displayed two carrier-mediated transport components in CHO-PEPT1 cells, while in CHO-K1 cells the relationship was consistent with classic one component Michaelis-Menten kinetics. These results confirmed the affinity of PD 158473 for both LNAA and di/tripeptide transporters. Further, results from inhibition experiments using these two cell types indicate that the high affinity-low capacity system was the LNAA carrier and the low affinity-high capacity carrier was the di/tripeptide transporter. CONCLUSIONS: This study demonstrates overlapping substrate specificity between LNAA carrier and di/tripeptide transporter (hPEPT1) for PD 158473, an amino acid analog. Establishing Structure Transport Relationship (STR) for this overlap will aid in a design strategy for increasing oral absorption or targeting specific drugs to selected tissues.

Amino Acid Transport Systems↗
PubMed1998

Automated sample preparation for drugs in plasma using a solid-phase extraction workstation.

An automated solid-phase extraction workstation was used to develop, characterize and validate two separate HPLC methods for quantifying drugs in plasma. Method development was facilitated by workstation functions which allowed wash solvents of varying organic composition to be mixed and tested automatically. The precision estimates for the two methods were within 6.0 and 2.0% RSD across their respective calibration ranges. Accuracies for replicate determinations of quality controls were between -1.2 and +4.8 RE over ng ml-1 calibration ranges, respectively. Optimized recoveries were quantitative and were generally greater than 90% for the four analytes tested, and depended to a great extent, as expected, on the composition of the wash solvent. Sample throughput benchmarks for the two methods ranged from 3 to 10 min per sample, depending on the extent of air drying used. Because of parallel sample processing, 60 samples could be extracted in as little as 17 min.

Blood Chemical Analysis↗
PubMed1997

Development and validation of an ion-pair reversed-phase high-performance liquid chromatographic method for the separation of phosphonodipeptides.

The objective of this research was to develop a rapid, sensitive and reliable method for the separation of phosphonodipeptide prodrugs and parent compounds to facilitate the evaluation of cell permeation using in vitro cell culture models. Separation was accomplished isocratically within 10.0 min using a C18 (150x4.6 mm I.D., 3 microm) reversed-phase column. The mobile phase consisted of 5 mM tetrahexyl ammonium (ion-pair reagent) in 0.02 M phosphate buffer pH 6.5-acetonitrile (48.5:51.5, v/v). The flow-rate was 1.1 ml/min with detection at 221 nm. The standard curves were linear (r2>0.999) over the concentration range 1-100 microM. The method was reliable and reproducible, with the limit of quantitation being 1 microM (25 ng on column).

3T3 Cells↗
PubMed1995

High-performance liquid chromatographic assay for Melanotan-1 ([Nle4-DPhe7]alpha-melanocyte-stimulating hormone) in biological matrices.

The overall objective of this research was to develop a sensitive, specific, and stability-indicating HPLC assay for the determination of the [Nle4-DPhe7]alpha-melanocyte-stimulating hormone analog known as Melanotan-1 (MT-1) in biological matrices, i.e., cell culture transport media and human plasma. Separation was accomplished isocratically within 8.0 min using a C8 reversed-phase column. The mobile phase consisted of 0.1 M phosphate buffer-acetonitrile (80:20, v/v) with 18 microliters/l triethylamine at pH 2.50. The flow-rate was 1 ml/min with detection at 214 nm. Standard curves (n = 5) were linear over the concentration range 100-1000 ng/ml. The precision, accuracy, intra- and inter-day variations were good with C.V.s typically within 8.7% for concentrations greater than 100 ng/ml. This method was applied to a study of the transport of MT-1 in the Caco-2 cell monolayer model.

Amino Acid Sequence↗
PubMed1995

Mechanisms of acylcarnitine-mediated enhancement of calcium transport in the Caco-2 cell monolayer model.

The overall objective of this study was to determine the mechanisms of acylcarnitine-mediated enhancement of calcium transport across Caco-2 cells. The different mechanisms of enhancement postulated are (a) loosening of tight junctions, thereby promoting paracellular transport; (b) opening of calcium channels, thus increasing calcium entry; and (c) stimulation of the basolateral Ca-ATPase pump, thereby aiding calcium extrusion. Although the existence of calcium channels and the reversal of verapamil-mediated inhibition of calcium uptake by acylcarnitines were demonstrated for the first time in Caco-2 cells, the channels do not appear to be a major contributing factor to the enhancement of calcium transport by acylcarnitines. Calmidazolium, a potent Ca-ATPase pump inhibitor in tissues such as rat intestinal segments, failed to inhibit this pump in Caco-2 cells. Thus, the predominant mechanism of enhancement of calcium transport by acylcarnitines in the Caco-2 model appears to be via promotion of paracellular transport.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Enhancement of calcium transport in the Caco-2 cell monolayer model.

The overall objective of this research was to identify enhancers of calcium transport using an in-vitro Caco-2 cell monolayer model. The enhancers studied were medium-chain triglycerides (MCT) and acylcarnitines (AC). The extent of cell damage associated with the use of these enhancers was determined by monitoring the release of cellular lactate dehydrogenase (LDH). The effect of chain-length and concentration dependence of these agents on enhancement were also determined. The effects of ACs were found to be superior to those of MCTs. However, the ACs elicited a greater release of LDH than the MCTs. The possible mechanisms of enhancer-mediated increase in calcium transport and the potential significance of this study with regard to the prevention of osteoporosis are discussed.

Biological Transport, Active↗
PubMed1994

Neuroblastoma with testicular metastasis. Review of literature and report of a case.

Eventhough neuroblastoma presents with wide spread tumour dissemination, metastasis to testes had rarely been reported. We report a case of Stage IV neuroblastoma who developed metastasis to both testes. He had massive infra-diaphragmatic disease with involvement of left supraclavicular lymph node at presentation. Treatment received by him was not adequate and five months later he developed metastasis to both testes. Hematogenous spread might have been the possibility in this case.

Abdominal Neoplasms↗
PubMed1991

Midline cleft of lower lip with cleft of the mandible and midline dermoid in the neck.

A female infant presented with a midline cleft of the mandible and a midline dermoid in the neck. Midline clefts are rare craniofacial clefts. Midline mandibular clefts can be associated with midline cleft of upper lip and a dermoid of nose. But a midline mandibular cleft with a midline dermoid in the neck has not been reported before.

Cleft Lip↗
PubMed1989

Hepatoblastoma in siblings.

Two infants, a brother and sister, with hepatoblastoma of the right lobe of the liver were treated and are alive and lead normal lives. Only three other familial occurrences of this tumor have so far been documented.

Carcinoma, Hepatocellular↗
PubMed1988

Unusual presentation of patent vitello intestinal duct with round worms emerging from the umbilicus.

Patient vitello intestinal duct (VID) is not an uncommon anomaly in children. It usually presents with fecal discharge from the umbilicus. Round worm infestation is very common in Indian children, but an association of patent VID and ascariasis, presenting as round worms emerging from the umbilicus, is unique and has not been previously reported in the literature. We present such a case in a 2-year-old boy who presented with a history of round worms coming out through the umbilicus. It was provisionally diagnosed to be a case of patent VID, which was proven correct on laparotomy.

Ascariasis↗
PubMed1988

Intestinal complications of round worms in children.

One hundred forty-two patients with surgical complications of Ascaris lumbricoides were treated in our hospital over a period of 5 years. Included were 120 patients with subacute intestinal obstruction that were treated conservatively, and 22 patients with acute intestinal obstruction that required surgical intervention. Four of the 22 patients that were operated on died following various postoperative complications. However, there were no deaths among those presenting with subacute obstruction. In our experience, early recognition of the condition avoided serious complications and morbidity.

Acute Disease↗
PubMed1986

An unusual case of caudal duplication.

A male infant presented with two well-formed lower limbs and pelvis with external male genitalia attached to the thorax at the xiphisternum. The infant also had exomphalos major and talipes equinovarus deformity of the right foot. Surgical correction was done without any difficulty. The case is unusual, and such an abnormality has not been reported before.

Abnormalities, Multiple↗