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Biomedical subjects

B Venkatesh

Publications and source records attributed to B Venkatesh.

At least 73 records · Page 4Linked to original sources
PubMed1996

A systematic survey of the intergenic region between the murine oxytocin- and vasopressin-encoding genes.

The genomic region between the oxytocin (OT) and vasopressin (VP) genes in the two strains of mice was independently sequenced by our two groups. In this report, we present our collated sequence data and analyses. The mouse intergenic region (MUIGR) was aligned to that of the rat, which has been reported to contain 6.4-kb long interspersed nuclear element (LINE). The MUIGR sequences in the two mice strains did not contain any LINE sequences. This suggests that the approximately 3.5-kb sequence that is conserved between the rat and mouse intergenic regions is likely to be involved in the regulation of OT and VP expression. We also observed several conserved putative transcription factor recognition sequences. Analysis of the MUIGR revealed the lack of any significant ORFs, but the presence of several repetitive elements.

Animals↗
PubMed1996

Isolation, characterization and evolution of nine pufferfish (Fugu rubripes) actin genes.

The Japanese pufferfish Fugu rubripes (Fugu) has a small genome of about 400 Mb. Nine different actin genes have been isolated and sequenced from a genomic library constructed from this teleost. The six muscle-type actin genes include two alpha-skeletal actins, three alpha-cardiac actins and an alpha-anomalous (testis type) actin, and the three cytoplasmic actins include two beta-cytoplasmic actins and a beta-cytoplasmic (vascular type) actin. The two skeletal muscle actin genes have identical genomic organization, but differ by five amino acid residues. The three cardiac actin genes code for the same protein but differ in their nucleotide sequences and genomic organization. beta-Cytoplasmic actin1 differs by three amino acids from beta-cytoplasmic actin2. The alpha-anomalous (testis type) and beta-cytoplasmic (vascular type) actins are novel vertebrate actins. The amino acid sequence of alpha-anomalous (testis type) actin is the most divergent of all the known vertebrate actins and transcripts of this gene are abundant in the testis. The beta-cytoplasmic (vascular type) actin gene has eight introns, similar to mammalian smooth muscle actins, and is expressed in vascular tissues such as the gills, kidney and skin. Several known regulatory elements are found in the 5' flanking sequences and the first intron of various Fugu actin genes. The intron patterns of the various Fugu actins seem to be the result of loss of certain introns from a common ancestral gene.

Actins↗
PubMed1996

Surface active peptide-mediated porphyrin aggregation.

Surface active pentapeptide [2(HCOO-). Lys-Ala-Ala-Lys(Z)-Tyr-OCH3] has been synthesized and its micelle formation investigated using conductometric, pH metric, and UV spectroscopic techniques. The double head double tail peptide molecules are shown to interact with water soluble meso-tetrakis (4-sulfonatophenyl)-porphyrin [TPPS]H2 to form characteristic H-type aggregate at low concentrations, as evidenced by UV-Vis and fluorescence spectroscopic techniques. Spectroscopic analysis reveals that the aggregate contains 1:2 porphyrin-peptide combination. The equilibrium constant for the formation of peptide-porphyrin complex has been obtained by using absorption spectral data. The present studies provide new insight into the peptide-porphyrin interaction.

Amino Acid Sequence↗
PubMed1996

Intestinal permeability, gastric intramucosal pH, and systemic endotoxemia in patients undergoing cardiopulmonary bypass.

OBJECTIVE: To examine the relationship between gastric intramucosal pH, intestinal permeability, endotoxemia, and oxygen delivery in patients undergoing cardiopulmonary bypass (CPB). DESIGN: Prospective, observational study. SETTING: Tertiary care center. PATIENTS: Fifty patients undergoing elective cardiac surgery and 10 patients awaiting elective cardiac surgery. INTERVENTIONS: Patients received chromium 51-labeled ethylenediaminetetraacetic acid (51Cr-EDTA) as a marker of intestinal permeability; insertion of a nasogastric tonometer to measure intramucosal pH (pHi); insertion of a pulmonary artery catheter to measure systemic oxygen delivery and consumption variables; arterial blood sampling for plasma endotoxin by the Limulus amebocyte lysate assay; and blood and urine sampling for measurement of 51Cr-EDTA. MAIN OUTCOME MEASURES: Systemic oxygen delivery, duration of gastric mucosal acidosis, absorption of 51Cr-EDTA, appearance of systemic endotoxemia, renal dysfunction, and duration of hospital stay. RESULTS: Median (range) 24-hour urinary recovery of 51Cr-EDTA in patients was 10.6% (2.1% to 40.2%) while that in controls was 1.2% (0.7% to 2.0%, P<.001). Intestinal permeability increased during CPB. The median (range) for the lowest pHi after bypass was 6.98 (6.74 to 7.17). The pHi did not decline until CPB was discontinued and the heart took over the load of the circulation. Endotoxin was detectable (>0.2 endotoxin unit per milliliter) in the plasma of 21 patients (42%) during the study, most of whom were endotoxemic by the end of CPB. There was no evident relationship between the degree of gut permeability, endotoxemia, gut ischemia, or systemic oxygen dynamics. CONCLUSIONS: Cardiopulmonary bypass is associated with increases in gut permeability, which precede gut mucosal ischemia. In cardiac surgical patients, a low pHi is not necessarily indicative of an adverse clinical outcome. Endotoxemia as measured by the Limulus amebocyte lysate assay is common. The increased intestinal absorption of 51Cr-EDTA and gastric mucosal acidosis occur as independent phenomena and are not related in severity or time of onset.

Acidosis↗
PubMed1996

Continuous intra-arterial blood gas monitoring.

OBJECTIVE: To review the technology, clinical trials and current status of continuous blood gas monitoring in intensive care. DESIGN: The review describes the history, technology, various clinical trials on continuous blood gas monitoring and discusses the various factors which might affect their performance characteristics and outlines their potential role in intensive care and during anaesthesia. CONCLUSIONS: Over the past 10 years a number of continuous intra-arterial blood gas monitoring systems have been developed. The performance characteristics of these systems are comparable. Their levels of accuracy as measured in bench tonometry are not consistently achieved in clinical trials. The potential usefulness of these monitors in various clinical situations has been described in case studies. Controlled studies demonstrating an improvement in outcome with the use of these monitors have not been published.

Cost-Benefit Analysis↗
PubMed1996

Small is beautiful: comparative genomics with the pufferfish (Fugu rubripes).

As the Human Genome Project advances, it is clear that the emphasis will switch from accumulation of data to their interpretation. Comparative genomics provides a powerful way in which to analyse sequence data. Indeed, there is already a long list of 'model' organisms, which allow comparative analyses in a variety of ways. The very small vertebrate genome of the pufferfish provides a simple and economical way of comparing sequence data from mammals and fish, representing a large evolutionary divergence and so permitting the identification of essential elements that are still present in both species. These elements include genes and the associated machinery that controls their expression; elements that, in many cases, have survived the test of time.

Animals↗
PubMed1996

Conserved linkage between the puffer fish (Fugu rubripes) and human genes for platelet-derived growth factor receptor and macrophage colony-stimulating factor receptor.

We have cloned and sequenced the teleost homologs of the human genes encoding platelet-derived growth factor receptor-beta (PDGFR beta) and macrophage colony-stimulating factor 1 receptor (CSFIR) from the puffer fish Fugu rubripes. The Fugu PDGFR beta and CSFIR genes each consist of 21 coding exons similar to the human CSFI gene, but are considerably smaller than their human counterparts because of the smaller introns. Furthermore, the two Fugu genes are linked tandemly in a head-to-tail array similar to their human homologs with 2.2 kb of intergenic sequence. Amino acid sequences of the Fugu and human PDGFR beta and CSFIR genes show an overall homology of 45% and 39%, respectively, with the kinase domains showing a much higher degree of conservation. Dot-matrix analysis revealed several short stretches of conserved sequences in the 3' untranslated regions of the PDGFR beta genes and the adjacent promoter regions of the CSFIR genes. These conserved sequences may have a role in the regulation of expression of either or both of these closely linked genes.

Amino Acid Sequence↗
PubMed1996

Continuous measurement of arterial blood gas status during total hip replacement: a prospective study.

The arterial blood gas chemistry was measured continuously in ten patients during primary cemented total hip replacement in order to define more precisely the patterns of changes in blood gases during various stages of the operation. All ten patients demonstrated significant drops in PaO2 after femoral cement implantation and nine of the ten after acetabular cement implantation. The mean drop in PaO2 following acetabular cement expressed as mean +/- SD was 18 +/- 8 mmHg (16 +/- 6%) (P < 0.05) and femoral cement application was 25 +/- 11 mmHg (23 +/- 9%) (P < 0.05). For changes in PaO2 there were corresponding drops in SpO2 in all patients with the femoral cement and in eight patients with the acetabular cement. The mean drop in SpO2 following the application of acetabular and femoral cements respectively were 1.7 +/- 1.5% and 3 +/- 2.45%. No changes in blood PaO2 were observed during dislocation of the hip joint or reaming of acetabulum and femur. In vitro studies revealed no effect of the liquid monomer or the cured cement on the performance of the Clark electrode of the sensor. We suggest that significant drops in PaO2 occur with both acetabular and femoral cement implantation and that the derangements in blood PaO2 last longer than detected by pulse oximetry following cement implantation.

Adult↗
PubMed1995

Misleading information from pulse oximetry and the usefulness of continuous blood gas monitoring in a post cardiac surgery patient.

We report a case where misleading readings form a pulse oximeter were compared with the results obtained from a continuous multiparameter blood gas sensor (Paratrend 7 - Biomedical Sensors UK). The continuous mode of recording was useful in determining the right clinical course for the patient and serves to show how pulse oximetry may demonstrate misleading results in low flow states.

Bias↗
PubMed1995

Evaluation of the Paratrend 7 intravascular blood gas monitor during cardiac surgery: comparison with the C4000 in-line blood gas monitor during cardiopulmonary bypass.

OBJECTIVE: To evaluate the performance of the Paratrend 7 intravascular blood gas monitor (Biomedical Sensors, High Wycombe, UK, Ltd) during cardiac surgery and compare it with that of an in-line blood gas monitor placed in the arterial limb of an extracorporeal circuit during cardiopulmonary bypass. DESIGN: A prospective study. Consecutive patient enrolment. SETTING: In the cardiac surgical intensive care units at a tertiary referral center. INTERVENTION: Insertion of the Paratrend 7 intravascular sensor through the radial arterial catheter after induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Simultaneous measurements of pH, PCO2, and PO2 were made from the sensor and the blood gas analyzer, and the bias and precision were calculated on all the measured parameters. The bias and precision of the intravascular sensor during bypass for pH, PCO2, and PO2 were 0.01 and 0.06 pH units, 0.5 and 2.5 mmHg (2% and 8%), and 3 and 45 torr (0.5% and 14%), respectively. The bias and precision for the prebypass and the postbypass phases were comparable. The bias and precision of the extracorporeal monitor for pH, PCO2, and PO2 were 0.04 and 0.1 pH units, -0.3 and 4 mmHg (-1% and 15%) and 8 and 48 mmHg (4 and 18%), respectively. There were no instances of any complications attributable to the intravascular sensor. CONCLUSIONS: The intravascular sensor used in this study functioned well during cardiopulmonary bypass and the postbypass phase. The performance of the intravascular sensor was better than the in-line blood gas monitor during cardiopulmonary bypass.

Adult↗
PubMed1995

Structure and organization of the isotocin and vasotocin genes from teleosts.

Oxytocin and vasopressin are structurally related mammalian neurohypophysial hormones with distinct physiological activities. Homologues of these two hormones are found in all vertebrate groups except the primitive cyclostomes in which only a vasopressin-like hormone has been reported so far. Genes encoding the mammalian oxytocin and vasopressin hormone precursors exhibit a similar genomic organisation, and are closely linked (3.5 kb to 12 kb apart) in a tail-to-tail manner suggesting a common evolutionary origin. However, no linkage among genes of the vasopressin/oxytocin family has been demonstrated in any of the lower vertebrates. The Japanese pufferfish, Fugu rubripes, has been shown to have a very compact genome of about 400 Mb with very few repetitive sequences. We used this model vertebrate genome to analyse the genomic organisation of vasotocin and isotocin genes, the teleost homologues of vasopressin and oxytocin. We have cloned and mapped the vasotocin/isotocin locus in Fugu and obtained complete nucleotide sequences of the vasotocin and isotocin genes. The coding sequences of the Fugu vasotocin and isotocin genes are interrupted by two introns at identical positions, similar to their homologues in higher vertebrates. The deduced amino acid sequences as well as the coding sequences of the two genes show high homology in the neurophysin region. Furthermore, the two genes are linked in a tandem manner with an intergenic region of about 20 kb. Random sequencing has shown that there are at least two known vertebrate genes in the intergenic region. Genomic organisation of the Fugu vasotocin/isotocin locus suggests that the teleost vasotocin and isotocin genes have evolved from a common ancestor through tandem duplication and that this locus seems to have undergone a localised reorganisation during vertebrate evolution.

Amino Acid Sequence↗
PubMed1994

Measuring carbon dioxide tension in saline and alternative solutions: quantification of bias and precision in two blood gas analyzers.

OBJECTIVE: To quantify the precision and bias for two standard blood gas analyzers when measuring PCO2 in five different test solutions (blood, normal saline, human albumin solution, succinylated gelatin 4%, and Hartmann's solution). DESIGN: A comparative laboratory study of two blood gas analyzers measuring known PCO2 in test solutions prepared with a thin film tonometer. MEASUREMENTS: The PCO2 was determined simultaneously in both blood gas analyzers. The precision and bias for both machines were calculated from the measured PCO2. RESULTS: Analyzer 1 showed a negative bias of between 66.4% and 39.2% when measuring PCO2 in saline. Under the same conditions, analyzer 2 showed a negative bias of between 17.7% and 17.9% for PCO2 in the mid- and high ranges of PCO2, but a positive bias in the low range. Both machines measured PCO2 with satisfactory bias and precision in blood. The use of succinylated gelatin 4% as a test solution improved the bias and precision of both machines. CONCLUSIONS: Because of the large bias and precision, neither of these machines is suitable for measuring PCO2 in saline solution. The use of succinylated gelatin 4% as a test solution improves the bias and precision of both machines and we favor this solution for nasogastric tonometry. Even with succinylated gelatin 4%, there is a large negative bias with analyzer 1 and our preference is to use analyzer 2. We recommend that other workers review critically the performance of blood gas electrode systems when measuring PCO2 in saline solution. Because of varying performance of "standard" machines, we also recommend that each institution determine its own reference range for intramucosal pH.

Blood Gas Analysis↗