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K Patel

Publications and source records attributed to K Patel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Myocardial dysfunction in the septic rat heart: role of nitric oxide.

Previous studies have demonstrated that sepsis, endotoxin, and cytokine administration cause myocardial dysfunction. Nitric oxide has been implicated in this dysfunction, since in isolated cardiac tissues, dysfunction is prevented when nitric oxide synthase (NOS) inhibitors are present. To determine whether nitric oxide produced by the inducible form of the enzyme (iNOS) contributed to Escherichia coli sepsis-induced myocardial dysfunction, the effects of preventing the induction of the enzyme or inhibiting the activity of the enzyme were determined. Rats, made septic by the injection of E. coil into the dorsal subcutaneous space, demonstrated a decreased intrinsic contractile function when hearts were studied the next day. Perfusion of hearts in vitro with the iNOS inhibitor S-methylisothiourea did not reverse the sepsis-induced contractile dysfunction. However, treatment of animals with S-methylisothiourea or dexamethasone, a glucocorticoid that prevents the synthesis of the iNOS, at the time of induction of sepsis resulted in partial but not complete attenuation of myocardial contractile dysfunction induced by sepsis. Thus, nitric oxide contributed to myocardial dysfunction in an intact animal treated with E. coli but was not the sole factor involved.

Animals↗
PubMed1998

Human immunodeficiency virus-associated nephropathy in the Bronx: low prevalence in a predominantly Hispanic population.

Reports of human immunodeficiency virus-associated nephropathy (HIVAN) occurring in Hispanics, females and heterosexuals are scarce. We reviewed 858 charts from our total HIV population to determine the prevalence and epidemiology of HIVAN at our center, and to evaluate the renal and patient survival among individual groups, according to race, sex and HIV risk factor. The prevalence of HIVAN was low (1.9%), relative to other centers (4-13%). Although Hispanics accounted for 56% of the HIV population, only 38% of HIVAN patients were Hispanic. The absolute risk of HIVAN in blacks was 3. 6%, and in Hispanics was 1.3%. The relative risk of blacks vs. Hispanics was 2.8% (p < 0.04). Women and men were represented equally in both the HIVAN and HIV populations. The mean (+/- SE) rate of decline in glomerular filtration rate was 3.7 +/- 0.9 ml/min/month, and patient survival following the onset of HIVAN was 23.6 +/- 4.8 months. We found no difference in renal or patient survival between individual groups. In summary, the risk of HIVAN in Hispanics is similar to that for whites. Male sex is not an independent risk factor. Both renal and patient survival are similar in blacks and Hispanics, and in men compared to women.

AIDS-Associated Nephropathy↗
PubMed1998

Tbx genes and limb identity in chick embryo development.

Tbx-2, Tbx-3, Tbx-4 and Tbx-5 chick genes have been isolated and, like the mouse homologues, are expressed in the limb regions. Tbx-2 and Tbx-3 are expressed in anterior and posterior domains in wings and legs, as well as throughout the flank. Of particular interest, however, are Tbx-5, which is expressed in wing and flank but not leg, and Tbx-4, which is expressed very strongly in leg but not wing. Grafts of leg tissue to wing and wing tissue to leg give rise to toe-like or wing-like digits in wing and leg respectively. Expression of Tbx-4 is stable when leg tissue is grafted to wing, and Tbx-5 expression is stable when wing tissue is grafted to leg. Induction of either extra wings or legs from the flank by applying FGF-2 in different positions alters the expression of Tbx-4 and Tbx-5 in such a way that suggests that the amount of Tbx-4 that is expressed in the limb determines the type that will form. The ectopic limb always displays a limb-like Tbx-3 expression. Thus Tbx-4 and Tbx-5 are strong candidates for encoding 'wingness' and 'legness'.

Amino Acid Sequence↗
PubMed1998

Elevated Amniotic Fluid Interleukin-6 as a Predictor of Neonatal Periventricular Leukomalacia and Intraventricular Hemorrhage.

> Objective: To investigate the relationship between amniotic fluid interleukin-6 levels and the development of periventricular leukomalacia and intraventricular hemorrhage in the preterm neonate and to compare the value of amniotic fluid interleukin-6 with amniotic fluid culture and histologic chorioamnionitis in the prediction of periventricular leukomalacia and intraventricular hemorrhage. Methods: 119 women, between 20 and 34 weeks gestation, in preterm labor with intact membranes, underwent transabdominal amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria, Ureaplasma urealyticum and Mycoplasma hominis. Amniotic fluid interleukin-6 levels were determined by enzyme-linked immunosorbent assay. The placentas were examined for histopathologic evidence of inflammation. Where the birth weight was <2,000 g, transfontanelle cranial sonography was performed on the 3rd and 7th days of life for diagnosis of periventricular leukomalacia and intraventricular hemorrhage. Student's t test, the Mann-Whitney U test, likelihood ratio chi2, logistic regression, and receiver-operator characteristic curve were used for analysis. Results: 33 women were excluded from the analysis because they delivered at other institutions. The neonates of 33 women did not have sonography because they weighed >2,000 g at birth. Two neonates died before sonography was performed; four neonates who weighed <2,000 g at birth did not have sonography. In the definitive study group of 47 women, those with neonates who developed periventricular leukomalacia and intraventricular hemorrhage (n = 14) had higher median amniotic fluid interleukin-6 levels (42,795 pg/ml versus 8,020 pg/ml; P = 0.009), more positive amniotic fluid cultures (64% vesus 21%; P < 0.003), and a shorter median amniocentesis-to-delivery interval (16 h versus 24 h; P = 0.045) than women (n = 33) who delivered neonates without periventricular leukomalacia or intraventricular hemorrhage. The groups did not differ in gestational age at admission (P = 0.15), birth weight (P = 0.09), or histologic chorioamnionitis (P = 0.37). An amniotic fluid interleukin-6 level >/=20,000 pg/ml had a sensitivity of 71% and a specificity of 70% compared with a sensitivity of 69% and specificity of 79% for amniotic fluid culture, and a sensitivity of 71% and specificity of 42% for histologic chorioamnionitis in the prediction of periventricular leukomalacia and intraventricular hemorrhage. Women with amniotic fluid interleukin-6 levels >/=20,000 pg/ml (n = 20) had more neonates with periventricular leukomalacia or intraventricular hemorrhage than women with amniotic fluid interleukin-6 levels <20,000 pg/ml (n = 27) (50% versus 15%; P = 0.009). They also were of lower birth weight (P = 0.02), had more neonatal morbidity (P = 0.01), had more positive amniotic fluid cultures (P = 0.01), and more histologic chorioamnionitis (P = 0.02). Logistic regression analysis demonstrated that amniotic fluid interleukin-6 was an independent risk factor for the development of periventricular leukomalacia and intraventricular hemorrhage (odds ratio, 5.81; 95% confidence interval, 1.02-33.16; P = 0.05) after controlling for gestational age, birth weight, histologic chorioamnionitis, and amniotic fluid culture (odds ratio, 7.94; 95% confidence interval 1.22-51.77; P = 0.03). Conclusions: In women in preterm labor with intact membranes amniotic fluid interleukin-6 is useful in predicting neonatal periventricular leukomalacia and intraventricular hemorrhage.

Journal Article↗
PubMed1997

Retinoic acid and the cyclin dependent kinase inhibitors synergistically alter proliferation and morphology of U343 astrocytoma cells.

We have characterized the expression and activity of the cell cycle regulatory machinery and the organization of the cytoskeleton of the p16(Ink4a)-deficient astrocytoma cell line, U343 MG-a (U343), following retinoic acid (RA) treatment. RA causes cell cycle arrest at low cell density and significant morphological changes in U343 cells, reflected by reorganization of the intermediate filament, GFAP, and actin. RA-induced cell cycle arrest is also associated with induction of p27Kip1 expression, inhibition of cdk2-associated kinase activity and alteration of the phosphorylation state of the pRB-family proteins. We next determined the effect of inducing expression of the cyclin dependent kinase inhibitors (CKI's), p16(Ink4a), p21Cip1/Waf1 or p27Kip1 on the proliferation and morphology of these malignant astrocytoma cells in the absence and presence of RA. Induction of p16, p21 or p27, using the tetracycline repressor system, potently inhibits proliferation of U343 cells. However, rather than resembling RA-treated cells, CKI-induced U343 cells become flat with abundant cytoplasm and perinuclear vacuolization. CKI-induced morphological alterations are accompanied by a significant reorganization of glial filaments within the cytoplasm. Interestingly, when U343 cells are growth arrested by p16, p21 or p27 induction and treated simultaneously with RA, a dramatic morphological change occurs, cells acquiring multiple long, tapering processes reminiscent of primary astrocytes. This rearrangement is accompanied by reorganization of GFAP, vimentin and actin. Vimentin specifically relocalizes to the tips of the long processes which form. The arrangement of intermediate filaments in these cells is, in fact, indistinguishable from their arrangement in primary human astrocytes. These data demonstrate that when a strong proliferative block, produced by CKI expression, occurs in conjunction with the morphogenic signals generated by RA, these p16-deficient malignant astrocytoma cells are induced to phenotypically resemble normal astrocytes.

Actins↗
PubMed1997

The EphA4 and EphB1 receptor tyrosine kinases and ephrin-B2 ligand regulate targeted migration of branchial neural crest cells.

BACKGROUND: During vertebrate head development, neural crest cells migrate from hindbrain segments to specific branchial arches, where they differentiate into distinct patterns of skeletal structures. The rostrocaudal identity of branchial neural crest cells appears to be specified prior to migration, so it is important that they are targeted to the correct destination. In Xenopus embryos, branchial neural crest cells segregate into four streams that are adjacent during early stages of migration. It is not known what restricts the intermingling of these migrating cell populations and targets them to specific branchial arches. Here, we investigated the role of Eph receptors and ephrins-mediators of cell-contact-dependent interactions that have been implicated in neuronal pathfinding-in this targeted migration. RESULTS: Xenopus EphA4 and EphB1 are expressed in migrating neural crest cells and mesoderm of the third arch, and third plus fourth arches, respectively. The ephrin-B2 ligand, which interacts with these receptors, is expressed in the adjacent second arch neural crest and mesoderm. Using truncated receptors, we show that the inhibition of EphA4/EphB1 function leads to abnormal migration of third arch neural crest cells into second and fourth arch territories. Furthermore, ectopic activation of these receptors by overexpression of ephrin-B2 leads to scattering of third arch neural crest cells into adjacent regions. Similar disruptions occur when the expression of ephrin-B2 or truncated receptors is targeted to the neural crest. CONCLUSIONS: These data indicate that the complementary expression of EphA4/EphB1 receptors and ephrin-B2 is involved in restricting the intermingling of third and second arch neural crest and in targeting third arch neural crest to the correct destination. Together with previous work showing that Eph receptors and ligands mediate neuronal growth cone repulsion, our findings suggest that similar mechanisms are used for neural crest and axon pathfinding.

Animals↗
PubMed1997

Loss of expression of receptor tyrosine kinase family genes PTK7 and SEK in metastatic melanoma.

Protein tyrosine kinases (PTKs) have been implicated in the development of many common human tumours including melanoma. Previously we isolated PTK gene sequences expressed in normal melanocytes. Here we examined expression of 9 of these genes in cell lines derived from defined stages of melanoma progression, by Northern blotting and in some cases immunoblotting. We also tested cells from 2 animal models of particular stages in progression, as well as uncultured biopsies of metastatic melanoma. The expression of 2 receptor kinase family members found in melanocytes, PTK7/CCK-4 and SEK/TYRO1, was decreased or lost in advanced melanomas. PTK7 mRNA was found in only 54% of melanoma cell lines and 20% of melanoma biopsies. Similarly, expression was lost in 2 advanced cell lines selected from an early melanoma line that did express PTK7 mRNA. SEK/TYRO1 expression was observed in 75% and 17% of cell lines from primary and metastastic melanomas, respectively. Conversely, mRNA for the non-receptor kinase PTK6/BRK was not detected in normal melanocytes or primary melanoma lines, but was found in 9% of metastatic melanoma cell lines.

Cell Adhesion Molecules↗
PubMed1997

Hox9 genes and vertebrate limb specification.

Development of paired appendages at appropriate levels along the primary body axis is a hallmark of the body plan of jawed vertebrates. Hox genes are good candidates for encoding position in lateral plate mesoderm along the body axis and thus for determining where limbs are formed. Local application of fibroblast growth factors (FGFs) to the anterior prospective flank of a chick embryo induces development of an ectopic wing, and FGF applied to posterior flank induces an ectopic leg. If particular combinations of Hox gene expression determine where wings and legs develop, then formation of additional limbs from flank should involve changes in Hox gene expression that reflect the type of limb induced. Here we show that the same population of flank cells can be induced to form either a wing or a leg, and that induction of these ectopic limbs is accompanied by specific changes in expression of three Hox genes in lateral plate mesoderm. This then reproduces, in the flank, expression patterns found at normal limb levels. Hox gene expression is reprogrammed in lateral plate mesoderm, but is unaffected in paraxial mesoderm. Independent regulation of Hox gene expression in lateral plate mesoderm may have been a key step in the evolution of paired appendages.

Animals↗
PubMed1997

Proteasome- and p53-dependent masking of signal transducer and activator of transcription (STAT) factors.

Hepatoma Hep3B cell lines stably expressing a temperature-sensitive p53 species (p53-Val-135) displayed a reduced response to interleukin-6 (IL-6) when cultured at the wild-type (wt) p53 temperature (Wang, L., Rayanade, R., Garcia, D., Patel, K., Pan, H., and Sehgal, P. B. (1995) J. Biol. Chem. 270, 23159-23165). We now report that in such cultures IL-6 caused a rapid (20-30 min) and marked loss of cellular immunostaining for STAT3 and STAT5, but not for STAT1. The loss of STAT3 and STAT5 immunostaining was transient (lasted 120 min) and tyrosine kinase-dependent, and even though the loss was blocked by the proteasome inhibitors MG132 and lactacystin it was not accompanied by changes in cellular levels of STAT3 and STAT5 proteins suggesting that IL-6 triggered a rapid masking but not degradation of these transcription factors. STAT3 and STAT5 masking was accompanied by a reduction in IL-6-induced nuclear DNA-binding activity. The data suggest that p53 may influence Jak-STAT signaling through a novel indirect mechanism involving a wt p53-dependent gene product which upon cytokine addition is activated into a "STAT-masking factor" in a proteasome-dependent step.

Carcinoma, Hepatocellular↗
PubMed1997

Primary acquired sideroblastic anemia, thrombocytosis, and trisomy 8.

Myelodysplastic syndromes are usually associated with pancytopenia. Disorders involving deletion of the long arm of chromosome 5 (5q-syndrome) and, rarely, patients with karyotypic abnormalities involving chromosome 3 associated with abnormal thrombopoiesis may have a normal or even raised platelet count. Other cytogenetic abnormalities in myelodysplasia are invariably associated with cytopenia in one or all cell lineages. We report a patient who initially presented with slight anemia and a raised platelet count. Further investigations suggested a diagnosis of primary acquired sideroblastic anemia. Cytogenetic examination revealed a clone with trisomy 8. We believe this is the first reported case of trisomy 8 with trilineage myelodysplasia and thrombocytosis with primary acquired sideroblastic anemia.

Aged↗
PubMed1997

Stability and compatibility of topotecan hydrochloride for injection with common infusion solutions and containers.

The stability and compatibility of topotecan hydrochloride with common infusion solutions and containers were studied. During this study, the leaching of diethylhexyl phthalate (DEHP), a major plasticizer of some polyvinyl chloride (PVC) materials was also investigated. A formulation of topotecan hydrochloride was added to 50 ml PVC infusion bags, polyolefin infusion bags and 150 ml glass bottles containing either 5% dextrose injection or 0.9% sodium chloride injection at an initial nominal topotecan concentration of 0.05 mg ml-1. Additionally, the topotecan hydrochloride formulation was added to 50 ml PVC infusion bags containing either 5% dextrose injection or 0.9% sodium chloride injection at an initial nominal topotecan concentration of 0.025 mg ml-1. Containers were maintained at 5 degrees C for 7 days or 23-24 degrees C for 24 h. Samples were analyzed using a stability-indicating HPLC method to determine the concentration of topotecan and the presence of any degradates. The samples were also analyzed by separate HPLC methods to detect the presence of DEHP and the hydrolyzed lactone ring form (SKF 105992) of topotecan hydrochloride. In addition, the pH of each sample was measured initially and at the end of the storage time. There was no significant loss of topotecan observed for any of the conditions studied and no significant increase in degradates was observed. The pH remained unchanged for all samples between the start and end of the study. At the concentrations studied, topotecan hydrochloride was stable for up to 24 h at room temperature and for up to 7 days at 5 degrees C, in PVC and polyolefin infusion bags and glass bottles containing either 5% dextrose injection or 0.9% sodium chloride injection. The presence of topotecan hydrochloride did not contribute to leaching of DEHP in the PVC infusion bags.

Antineoplastic Agents↗
PubMed1997

Interferon gamma induces cell cycle arrest and apoptosis in a model of ovarian cancer: enhancement of effect by batimastat.

Locoregional human IFN-gamma may have activity against refractory ovarian cancer. We investigated this further in an ovarian cancer xenograft model. Administered at clinically relevant doses, intraperitoneal IFN-gamma prolonged the survival of mice bearing multiple established peritoneal tumours, with optimal treatment giving a 3-6-fold increase in median survival time. Daily dosing, which was superior to intermittent treatment, decreased DNA synthesis and induced apoptosis in tumour cells with maximal effects after 7-21 days treatment. This was preceded by an increase in p53 protein at 48 h. The effect of IFN-gamma was not enhanced by sequential treatment with carboplatin. However, the matrix metalloprotease inhibitor, batimastat, further increased mouse survival when given after IFN-gamma. Thus IFN-gamma is cytotoxic to ovarian epithelial cells in vivo and intensive locoregional dosing over short periods is effective. Sequential administration of novel agents that perturb the host/tumour relationship may be of benefit.

Animals↗
PubMed1997

Characterization of [3H]-prostaglandin E2 binding to prostaglandin EP4 receptors expressed with Semliki Forest virus.

1. The human prostaglandin EP4 receptor has been expressed by use of the Semliki Forest virus system. 2. In cell membranes [3H]-prostaglandin E2 ([3H]-PGE2) bound to a high affinity site with a Kd of 1.12 +/- 0.3 nM and a Bmax of 3.1 +/- 0.3 pmol mg-1 protein. 3. In competition studies the rank order of potency for prostaglandins was PGE2 = PGE1 > > PGE2 alpha = PGI2. 4. The binding of [3H]-PGE2 to cell membranes was inhibited by approximately 60% by the addition of guanylnucleotides, suggesting that this proportion of the receptors was G-protein coupled. 5. [3H]-PGE2 binding was increased by greater than 200% by the addition of divalent cations, with little change in the IC50 of PGE2. 6. In saturation studies removal of divalent cations and addition of GTP gamma S resulted in a 65% reduction in the Bmax with no change in the Kd. These results are consistent with the ligand labelling two states of the receptor R*, a high affinity state and R*G, a high affinity G protein coupled state.

Binding, Competitive↗
PubMed1997

Cell movements, neuronal organisation and gene expression in hindbrains lacking morphological boundaries.

Rhombomeres are segmental units of the hindbrain that are separated from each other by a specialised zone of boundary cells. Retinoic acid application to a recently segmented hindbrain leads to disappearance of posterior rhombomere boundaries. Boundary loss is preceded by changes in segmental expression of Krox-20 and Cek-8 and followed by alterations in Hox gene expression. The characteristic morphology of boundary cells, their expression of follistatin and the periodic accumulation of axons normally associated with boundaries are all lost. In the absence of boundaries, we detect no change in anteroposterior dispersal of precursor cells and, in most cases, no substantial cell mixing between former rhombomeric units. This is consistent with the idea that lineage restriction can be maintained by processes other than a mechanical barrier composed of boundary cells. Much of the early organisation of the motor nuclei appears normal despite the loss of boundaries and altered Hox expression.

Animals↗
PubMed1997

Chick noggin is expressed in the organizer and neural plate during axial development, but offers no evidence of involvement in primary axis formation.

We have cloned and examined the early developmental expression of the chick homolog of noggin, a gene originally isolated in Xenopus that can dorsalize gastrular mesoderm and induce anterior neural tissue from gastrular ectoderm when expressed experimentally. Chick noggin is expressed at relatively low levels, but at sites equivalent to those seen in amphibian development, namely Hensen's node and the endo- and mesodermal head process. There is also diffuse expression in the early CNS, centered on the ventral midline, and later hindbrain-associated expression. Since the earlier of these expression sites are consistent with endogenous organizer functions suggested by the properties of the protein in Xenopus experiments, we have used recombinant mammalian Noggin protein secreted by CHO cells in tests for developmental disturbance on the early gastrula-staged chick blastoderm. Comparable tests sensitively detect effects, on chick, of various other secreted proteins that simulate or replicate early developmental signals in Xenopus. We have been unable to observe such effects with a range of Noggin concentrations including those that dramatically dorsalize Xenopus ventral marginal zones. To illustrate effects observed in such tests with secreted proteins active on early stages, we show results with the known Xenopus ventralizer Bone Morphogenetic Protein 4 (BMP-4).

Amino Acid Sequence↗
PubMed1997

Artemether in moderate to severe malaria: a multicenter trial in India.

154 patients suffering from acute attack of moderate to severe malaria caused by Plasmodium falciparum were treated with 480 mg artemether, administered intramuscularly (i.m.) in six equally divided doses at 12 hour intervals. Results showed a rapid parasite clearance. Mean parasite clearance time (PCT) was found to be 23.65 +/- 1.57 hours. Mean fever clearance time (FCT) was 35.28 +/- 1.7 hours. Adverse drug events (ADE) were mild and self-limiting. Recrudescence rate (RR) among the patients followed up was 4.55%. We conclude that artemether is a safe and effective anti-malarial agent for the treatment of moderate and severe cases of P. falciparum malaria.

Acute Disease↗
PubMed1996

Cloning and early dorsal axial expression of Flik, a chick follistatin-related gene: evidence for involvement in dorsalization/neural induction.

We have cloned and sequenced a chick gene, Flik (follistatin-like) that appears to be the homolog of the mammalian TSC36. The ORF encodes a secreted protein of approx 38 kDa, containing a single cysteine-rich domain that shows a strong relationship with the second of the four from which Follistatin is constructed. The remainder of the Flik protein shows no strong family affinities. We describe here the normal expression pattern of the gene during primitive streak and neurula stages. We also give revised data for early neurectodermal expression of chick follistatin (Connolly et al., 1995, Developmental Genetics 17(1), 65-77) and follow the new ectopic expression of both genes during the induction of a second neural axis, after grafting of Hensen's node into a peripheral position in a host blastoderm. Both genes mark the organizer (node and/or mesodermal head process) and early neural plate, and could thus be involved in intercellular signaling during mesodermal dorsalization and neural induction. Flik expression appears earlier than that of follistatin however, and unlike that of follistatin, it is maintained strongly in the dorsal midline with intensity smoothly declining into presumptive lateral regions. We show that both genes are upregulated in host tissue in the neighborhood of node grafts, but whereas follistatin is transcribed after 8-10 hr in host epiblast that has formed new neural plate, Flik is expressed within 4 hr in this region, sometimes detectable before the first structural changes (columnarization) of neuralization. Thus, although ectodermal Flik expression is later confined within neural plate, and mesodermal expression concentrated in dorsal axial tissue, its early distribution is consistent with the idea that the encoded protein may first be involved in generating a graded system that positions the boundaries of both neural and dorsal axial mesodermal territories. The results are discussed in relation to this hypothesis and to other recent findings regarding control of vertebrate dorsoventral patterning.

Amino Acid Sequence↗