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Biomedical subjects

R Basu

Publications and source records attributed to R Basu.

At least 37 records · Page 2Linked to original sources
PubMed1999

Lipid peroxidation can be reduced in infants on total parenteral nutrition by promoting fat utilisation.

BACKGROUND/PURPOSE: Increased oxygen-derived free radical activity has been reported during total parenteral nutrition (TPN) in infants and has been specifically linked to the fat infusion. The aim of this study was to test the hypothesis that during TPN, oxygen-derived free radical production can be reduced by increasing the utilisation of fat. METHODS: In experiment A (17 patients) the fat infusion was kept constant (3 g/kg/d) and the carbohydrate infusion was changed from 18 g/kg/d on day 1 to 10 g/kg/d on day 2. In experiment B (six patients) the carbohydrate infusion remained constant and the fat infusion was changed from 3 g/kg/d on day 1 to 0 g/kg/d on day 2. Fat utilisation was measured by indirect calorimetry. Plasma malondialdehyde, an index of lipid peroxidation resulting from increased oxygen-derived free radical activity, was measured by a colorimetric assay. RESULTS: In both experiments there was no significant change between the two study phases in oxygen consumption, carbon dioxide production, and resting energy expenditure demonstrating that the patients were metabolically stable. In experiment A there was a significant (P = .0005) increase in fat utilisation and a significant (P = .009) decrease in malondialdehyde (MDA) concentration between the two phases. In experiment B there was also a significant (P = .007) decrease in MDA concentration. The decrease in MDA concentration was similar between the two experiments. CONCLUSIONS: It is not necessary to stop the infusion of fat to reduce free radical production. Promoting fat utilisation by reducing the carbohydrate-fat ratio of the TPN reduces free radical activity to a similar extent as fat exclusion. These findings have important implications for the composition of TPN.

Calorimetry, Indirect↗
PubMed1999

Free radical formation in infants: the effect of critical illness, parenteral nutrition, and enteral feeding.

BACKGROUND/PURPOSE: An increase in free radical activity has been observed in patients suffering from a variety of illnesses and has been correlated with disease severity. Free radical production is increased by the administration of total parenteral nutrition (TPN) and may be linked to its adverse effects. Some of the complications of TPN can be ameliorated by partial enteral feeding. The aim of this study was to investigate free radical activity during critical illness and during the administration of parenteral nutrition. METHODS: Three groups of surgical infants were studied: (1) control infants (n = 8) before minor surgery, (2) stable infants on the ward recovering from a major operation (n = 24), (3) critically ill infants in the neonatal intensive care unit (NICU, n = 28). Fourteen patients in the ward and 17 patients in NICU were receiving parenteral nutrition. Of the 31 patients on TPN, 9 were also receiving minimal enteral feeding (3% to 24% of total calorie intake). Plasma malondialdehyde (MDA), an index of free radical activity, was measured in all 60 infants. The Paediatric Risk of Mortality (PRISM) score was obtained on NICU patients. The cytokines tumor necrosis factor (TNF-alpha) and interleukin 6 (IL-6) were measured in 25 patients. RESULTS: Plasma MDA was significantly higher in (1) the stable patients on the ward compared with control patients (P < .001) and (2) patients in NICU compared with stable patients in the ward (P < .001). Parenteral nutrition was associated with higher levels of plasma MDA both in stable patients in the ward and critically ill infants in NICU. There was no correlation between the PRISM score and MDA. In patients not receiving TPN there is a correlation between MDA and TNF-alpha (r = 0.54, P = .02) and between MDA and IL-6 (r = 0.74, P = .001). The level of free radical activity in patients on TPN is not changed by partial enteral feeding. CONCLUSIONS: Critical illness causes a rise in free radical production. Parenteral nutrition causes a significant elevation in free radical activity in both stable infants in the ward and critically ill infants in NICU. The addition of minimal enteral feeding to parenteral nutrition does not reduce free radical activity. We hypothesize that the parenteral nutrition solution directly initiates free radical production.

Analysis of Variance↗
PubMed1999

Impact of lack of suppression of glucagon on glucose tolerance in humans.

People with type 2 diabetes have defects in both alpha- and beta-cell function. To determine whether lack of suppression of glucagon causes hyperglycemia when insulin secretion is impaired but not when insulin secretion is intact, twenty nondiabetic subjects were studied on two occasions. On both occasions, a "prandial" glucose infusion was given over 5 h while endogenous hormone secretion was inhibited. Insulin was infused so as to mimic either a nondiabetic (n = 10) or diabetic (n = 10) postprandial profile. Glucagon was infused at a rate of 1.25 ng. kg(-1). min(-1), beginning either at time zero to prevent a fall in glucagon (nonsuppressed study day) or at 2 h to create a transient fall in glucagon (suppressed study day). During the "diabetic" insulin profile, lack of glucagon suppression resulted in a marked increase (P < 0.002) in both the peak glucose concentration (11.9 +/- 0.4 vs. 8.9 +/- 0.4 mmol/l) and the area above basal of glucose (927 +/- 77 vs. 546 +/- 112 mmol. l(-1). 6 h) because of impaired (P < 0.001) suppression of glucose production. In contrast, during the "nondiabetic" insulin profile, lack of suppression of glucagon resulted in only a slight increase (P < 0.02) in the peak glucose concentration (9.1 +/- 0.4 vs. 8.4 +/- 0.3 mmol/l) and the area above basal of glucose (654 +/- 146 vs. 488 +/- 118 mmol. l(-1). 6 h). Of interest, when glucagon was suppressed, glucose concentrations differed only minimally during the nondiabetic and diabetic insulin profiles. These data indicate that lack of suppression of glucagon can cause substantial hyperglycemia when insulin availability is limited, therefore implying that inhibitors of glucagon secretion and/or glucagon action are likely to be useful therapeutic agents in such individuals.

Adult↗
PubMed1999

Effect of overnight restoration of euglycemia on glucose effectiveness in type 2 diabetes mellitus.

The ability of glucose to stimulate its own uptake and suppress its own release is impaired in type 2 diabetes. To determine whether glucose effectiveness is improved by short term euglycemia, 10 type 2 diabetic subjects were studied on 2 occasions. Insulin was infused throughout the night to maintain euglycemia (approximately 5 mmol/L), or glucose was permitted to remain at ambient hyperglycemic levels (approximately 10 mmol/L) until the following morning when euglycemia was achieved with a variable insulin infusion. A prandial glucose infusion (containing 35 g glucose) was started at 1000 h, and the variable insulin infusion was replaced by a constant infusion of insulin (0.25 mU/ kg x min), somatostatin (60 ng/kg x min), glucagon (0.65 ng/kg x min), and GH (3 ng/kg x min) to maintain hormone concentrations at constant basal levels. Although nocturnal glucose concentrations were (by design) higher (P<0.01) on the hyperglycemic than on the euglycemic study day (10.1+/-0.2 vs. 5.4+/-0.1 mmol/L), glucose concentrations did not differ either before (4.9+/-0.1 vs. 4.9+/-0.1 mmol/L) or during the prandial glucose infusion (peak, 11.1+/-0.5 vs. 11.3+/-0.5 mmol/L; incremental area, 1390+/-254 vs. 1409+/-196 mmol/L x 6 h). Furthermore, glucose-induced stimulation of glucose disappearance (2068+/-218 vs. 1957+/-244 micromol/kg x 6 h) and suppression of glucose production (-2253+/-378 vs. -2124+/-257 micromol/kg x 6 h) did not differ. Thus, restoration of euglycemia by means of an overnight insulin infusion does not alter glucose effectiveness in people with type 2 diabetes.

Blood Glucose↗
PubMed1998

Failure of nocturnal changes in growth hormone to alter carbohydrate tolerance the following morning.

To determine whether the increases in growth hormone that occur during sleep alter carbohydrate tolerance the following morning, two groups of volunteers were studied on two occasions. In one group saline alone was injected and infused (i.e. no octreotide) on one occasion and on the other octreotide was injected at 23.00 hours to inhibit endogenous growth hormone secretion followed by saline infusion to create a state of relative nocturnal growth hormone deficiency. In the other group the octreotide injection was followed on one occasion by a constant growth hormone infusion designed to maintain growth hormone concentrations at "basal" levels throughout the night whereas on the other it was followed by a constant infusion plus two supplemental growth hormone infusions given at midnight and 02.30 hours to mimic the normal nocturnal rise in growth hormone. The next morning, subjects were fed a radiolabelled mixed meal. The differences in the nocturnal growth hormone concentrations had no effect on the glucose, insulin, C-peptide and glucagon concentrations following breakfast ingestion nor did they alter postprandial rates of glucose production, disappearance or substrate oxidation. Thus, the normal nocturnal rise in growth hormone does not appear to be an important regulator of carbohydrate tolerance the following morning.

Adult↗
PubMed1998

Normal glucose-induced suppression of glucose production but impaired stimulation of glucose disposal in type 2 diabetes: evidence for a concentration-dependent defect in uptake.

The present studies were undertaken to determine whether people with type 2 diabetes are resistant to the effects of glucose as well as insulin. Diabetic and nondiabetic subjects were studied on three occasions. Hormone secretion was inhibited with somatostatin. Insulin concentrations were kept at "basal" levels (referred to as low insulin infusion) from 0 to 180 min then increased to approximately 200 pmol/l from 181 to 360 min (referred to as high insulin infusion). Glucose concentrations were clamped at either approximately 95, approximately 130, or approximately 165 mg/dl on each occasion. In the presence of basal insulin concentrations, a progressive increase in glucose from 95 to 130 to 165 mg/dl was accompanied by a comparable and progressive decrease (P = 0.001 to 0.003 by analysis of variance [ANOVA]) in endogenous glucose production (measured with [6-(3)H]glucose) and total glucose output (measured with [2-(3)H]glucose) and incorporation of 14CO2 into glucose (an index of gluconeogenesis) in both diabetic and nondiabetic subjects, indicating normal hepatic (and perhaps renal) response to glucose. In the nondiabetic subjects, an increase in glucose concentration from 95 to 130 to 165 mg/dl resulted in a progressive increase in glucose disappearance during both the low (19.9 +/- 1.8 to 23.6 +/- 1.8 to 25.4 +/- 1.6 micromol x kg(-1) x min(-1); P = 0.003 by ANOVA) and high (36.4 +/- 3.1 to 47.6 +/- 4.5 to 61.1 +/- 7.0 micromol x kg(-1) x min(-1); P = 0.001 by ANOVA) insulin infusions. In contrast, in the diabetic subjects, whereas an increase in glucose from 95 to 130 mg/dl resulted in an increase in glucose disappearance during both the low (P = 0.001) and high (P = 0.01) dose insulin infusions, a further increase in glucose concentration to 165 mg/dl had no further effect (P = 0.41 and 0.38) on disappearance at either insulin dose (low: 14.2 +/- 0.8 to 18.2 +/- 1.1 to 18.7 +/- 2.4 micromol x kg(-1) x min(-1); high: 21.0 +/- 3.2 to 33.9 +/- 6.4 to 32.5 +/- 8.0 micromol x kg(-1) x min(-1) for 95, 130, and 165 mg/dl, respectively). We conclude that whereas glucose-induced stimulation of its own uptake is abnormal in type 2 diabetes, glucose-induced suppression of endogenous glucose production and output is not. The abnormality in uptake occurs in the presence of both basal and high insulin concentrations and is evident at glucose concentrations above but not below 130 mg/dl, implying a defect in a glucose-responsive step.

Blood Glucose↗
PubMed1997

Local staging of prostate cancer with 0.2 T body coil MRI.

This study was undertaken to evaluate the accuracy of low field strength body coil MRI in the staging of clinically localized prostate cancer. Fifty-three patients with prostate cancer were examined on a 0.2 T body coil system before undergoing radical prostatectomy. Of the 20 cases with unconfined stage T3 disease on histology, 12 were correctly staged, whilst three cases were overstaged by MRI. (Accuracy 79.2%, sensitivity 60%, and specificity 90.9%.) The accuracy, sensitivity and specificity for the detection of capsular penetration were 77.3%, 55% and 90.9%, respectively, whilst those for seminal vesical invasion were 94.3%, 83.3% and 95.7%, respectively. It is concluded that a high level of staging accuracy, comparable to that obtained in some published studies using high field strength endorectal coil MRI, can be obtained using 0.2 T body coil MRI.

Aged↗
PubMed1996

A point mutation causes mistargeting of Golgi GlcNAc-TV in the Lec4A Chinese hamster ovary glycosylation mutant.

The Lec4A and Lec4 Chinese hamster ovary glycosylation mutants lack N-linked glycans with GlcNAcbeta(1,6)Manalpha(1,6) branches that are initiated by the transferase termed GlcNAc-TV. Detergent extracts of Lec4 cells have no detectable GlcNAc-TV activity, but Lec4A extracts have activity equivalent to that of parental Chinese hamster ovary cells. This discrepancy occurs because Lec4A GlcNAc-TV activity co-localizes with membranes of the endoplasmic reticulum (ER) instead of with Golgi membranes (Chaney, W., Sundaram, S., Friedman, N., and Stanley, P. (1989) J. Cell. Biol. 109, 2089-2096). cDNAs from the coding region of the GlcNAc-TV gene have now been isolated from each mutant line. Lec4 GlcNAc-TV cDNA was found to possess two insertions, the first of which shifts the open reading frame and codes for a truncated transferase missing 585 amino acids from the catalytic domain. By contrast, Lec4A GlcNAc-TV cDNA possesses a single point mutation from T to G, which results in a change from Leu to Arg at position 188. When transfected into Lec4 cells, both cDNAs gave the appropriate phenotype; Lec4 cDNA was unable to restore GlcNAc-TV activity, whereas Lec4A cDNA converted Lec4 cells to the Lec4A phenotype, with an active GlcNAc-TV mislocalized to ER membranes. Moreover, Lec4A cDNA cured of its mutation restored a functional, Golgi-localized GlcNAc-TV to Lec4 cells. The results demonstrate that a single change in the 740 amino acids of GlcNAc-TV serves to functionally inactivate the transferase in an intact cell by causing it to localize to the ER instead of the Golgi compartment. The mislocalized transferase retains full enzyme activity, showing that it is well folded and stable and suggesting that the L188R mutation either prevents association with exit complexes from the ER or causes retrograde transport from a Golgi compartment.

Amino Acid Sequence↗
PubMed1996

Calculation of van't Hoff enthalpy associated with aspirin-induced change in liposomal membrane anisotropy.

The lipid disordering effect of aspirin on the liposomal membrane of dipalmitoyl phosphatidyl choline has recently been studied using the fluorescence polarization method. From the anisotropy-temperature curve, we have calculated here the associated change in van't Hoff enthalpy. Since the fluorescence technique requires a very small amount of sample (10(-4) M), this method of enthalpy calculation compares well and is advantageous over the standard calorimetric methods.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Interleukin-3 signals through multiple isoforms of Stat5.

The interleukin (IL)-3 family of cytokines mediates its numerous effects on myeloid growth and maturation by binding a family of related receptors. It has been shown recently that IL-3 induces the activation of two distinct cytoplasmic signal transducing factors (STFs) that are likely to mediate the induction of immediate early genes. In immature myeloid cells, IL-3 activates STF-IL-3a, which comprises two tyrosine-phosphorylated DNA binding proteins of 77 and 80 kDa. In mature myeloid cells, IL-3 and granulocyte-macrophage colony-stimulating factor activate STF-IL-3b, which consists of a 94 and 96 kDa tyrosine-phosphorylated DNA binding protein. Peptide sequence data obtained from the purified 77 and 80 kDa proteins (p77 and p80) indicate that they are closely related but are encoded by distinct genes. Both peptide and nucleotide sequence data demonstrate that these two proteins are the murine homologs of ovine mammary gland factor (MGF)/Stat5. The peptide data also indicate that p77 and p80 are phosphorylated on tyrosine 699, a position analogous to the tyrosine that is phosphorylated in Stat1 and Stat2 in response to interferon. Additionally, antiserum raised against bacterially expressed p77/p80 recognizes the 94 and 96 kDa protein components of STF-IL-3b, suggesting that these may be additional isoforms of Stat5. These studies indicate that the IL-3 family of ligands is able to activate multiple isoforms of the signal transducing protein Stat5.

Amino Acid Sequence↗
PubMed1995

cDNA cloning and tissue distribution of five human EPH-like receptor protein-tyrosine kinases.

We have isolated cDNA clones from a human fetal brain library that encode five members of the EPH sub-family of receptor protein tyrosine kinases (PTKs). Comparison of the DNA sequences of these receptors to the Genbank database reveals that two of our clones correspond to the previously identified HEK and ERK receptors, two are apparently human homologues of the mouse receptors Sek and Bsk and one is novel. With these additions, the number of known human EPH sub-family members is nine and the total in all vertebrate species is 13 making it the largest known sub-family of PTKs. Analysis of the expression pattern of EPH sub-family mRNAs reveals that some are expressed in a wide variety of adult tissues while others are quite restricted. Consistent with the amplification of these sequences from a fetal brain cDNA library, all five members which we have isolated are expressed in the brain. We have named these receptors HEK4, HEK5, HEK7, HEK8 and HEK11, following the nomenclature of Wicks et al. (1992) and the numbering convention set forth by Sajjadi et al. (1991). Analysis of these new EPH sub-family members will increase our understanding of the biology of this receptor family and their isolation will provide reagents for the identification of ligands for this large family of orphan receptors.

Amino Acid Sequence↗
PubMed1995

Cloning and characterization of the human megakaryocyte growth and development factor (MGDF) gene.

The megakaryocyte growth and development factor (MGDF) is a cytokine that regulates megakaryocyte development and is a ligand for the MPL receptor. In this study, we describe the genomic structure of the human MGDF gene. The MGDF gene was found to consist of seven exons and six introns spanning 8 kilobases. The protein is encoded by exons 3 through 7. The human MGDF gene has been mapped to chromosome 3q26.3. In addition to the previously described full-length cDNA, two cDNA variants were isolated from human fetal liver. Comparison of these two cDNA sequences with the genomic sequence indicates that they arise by differential splicing.

Amino Acid Sequence↗
PubMed1994

Lissencephaly-1 is one of the most conserved proteins between mouse and human: a single amino-acid difference in 410 residues.

The nucleotide (nt) sequence of the LIS-1 cDNA encoding the murine lissencephaly-1 (LIS-1) protein has been determined. The deduced protein shows a very high degree (99.8%) of homology with human LIS-1, having a single conservative amino acid (aa) change out of 410 aa and is identical to a subunit of bovine platelet-activating factor (PAF) acetylhydrolase.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1994

Cloning and characterization of the human neutrophil-activating peptide (ENA-78) gene.

The neutrophil-activating peptide (ENA-78) is an inflammatory chemokine which is produced concomitantly with interleukin-8 (IL-8) in response to stimulation with either interleukin-1 (IL-1 beta) or tumor necrosis factor-alpha (TNF-alpha). We have identified a full-length ENA-78 cDNA and isolated its genomic clone. The gene was found to consist of four exons and three introns and its structure resembles the IL-8 gene. The human ENA-78 gene was mapped to chromosome 4q13-q21, the same locus as several other inflammatory cytokine genes. The transcription initiation site was mapped to a position 96 base pairs (bp) upstream from the translation initiation site. A fusion gene containing 125 bp upstream of exon 1 linked to a luciferase reporter gene was expressed in the human embryonic 293 cell line. The expression of the reporter gene was induced by TNF-alpha, IL-1 beta, or phorbol 12-myristate 13-acetate. The 125-bp promoter region contained the cis-regulatory elements for enhancer binding protein-like factor (C/EBP) and the nuclear factor (NF-kappa B). Transfection of 293 cells with deletion mutants demonstrated that the NF-kappa B element, but not the C/EBP site, is sufficient for expression and induction by either TNF-alpha or IL-1 beta. In contrast, the IL-8 gene requires both elements. This report demonstrates that ENA-78 and IL-8 genes shared great similarity in genomic structure and chromosome location. However, these two genes may be regulated by distinct mechanisms.

Amino Acid Sequence↗
PubMed1994

Isolation and characterization of the human interleukin-9 receptor gene.

To better understand the regulation of interleukin-9 (IL-9) receptor expression, we have isolated the genomic clone of the human IL-9 receptor based on its sequence homology with a human IL-9 receptor cDNA isolated from the human megakaryocyte cell line UT-7. The entire genomic structure has been determined. The human IL-9 receptor gene consists of 10 exons spread over approximately 13.7 kb of DNA. The nucleotide sequence of the coding region from the genomic DNA is identical to our cDNA clone. Several blocks of transcriptional control sequence have been identified at the 5' noncoding region of the IL-9 receptor gene that may play an important role in the regulation of the IL-9 receptor gene. A fusion gene containing 659 bp of human IL-9 receptor 5' noncoding region linked to the firefly luciferase gene directed expression of luciferase activity in human embryonic kidney 293 cell line, but not in the mouse fibroblast cell line NIH3T3 cells.

Amino Acid Sequence↗