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Biomedical subjects

L A McLean

Publications and source records attributed to L A McLean.

6 recordsLinked to original sources
PubMed2001

Differential gene expression profiling in human brain tumors.

Gene expression profiling of three human temporal lobe brain tissue samples (normal) and four primary glioblastoma multiforme (GBM) tumors using oligonucleotide microarrays was done. Moreover, confirmation of altered expression was performed by whole cell patch clamp, immunohistochemical staining, and RT-PCR. Our results identified several ion and solute transport-related genes, such as N-methyl-d-aspartate (NMDA) receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-2 receptors, GABA(A) receptor subunits alpha3, beta1, beta2, and beta3, the glutamate transporter, the glutamate/aspartate transporter II, the potassium channel K(V)2.1, hK(V)beta3, and the sodium/proton exchanger 1 (NHE-1), that are all downregulated in the tumors compared with the normal tissues. In contrast, aquaporin-1, possibly aquaporins-3 and -5, and GLUT-3 message appeared upregulated in the tumors. Our results also confirmed previous work showing that osteopontin, nicotinamide N-methyltransferase, murine double minute 2 (MDM2), and epithelin (granulin) are upregulated in GBMs. We also demonstrate for the first time that the cytokine and p53 binding protein, macrophage migration inhibitory factor (MIF), appears upregulated in GBMs. These results indicate that the modulation of ion and solute transport genes and heretofore unsuspected cytokines (i.e., MIF) may have profound implications for brain tumor cell biology and thus may identify potential useful therapeutic targets in GBMs.

Aquaporin 1↗
PubMed2000

Malignant gliomas display altered pH regulation by NHE1 compared with nontransformed astrocytes.

Malignant gliomas exhibit alkaline intracellular pH (pH(i)) and acidic extracellular pH (pH(e)) compared with nontransformed astrocytes, despite increased metabolic H(+) production. The acidic pH(e) limits the availability of HCO(-)(3), thereby reducing both passive and dynamic HCO(-)(3)-dependent buffering. This implies that gliomas are dependent upon dynamic HCO(-)(3)-independent H(+) buffering pathways such as the type 1 Na(+)/H(+) exchanger (NHE1). In this study, four rapidly proliferating gliomas exhibited significantly more alkaline steady-state pH(i) (pH(i) = 7.31-7.48) than normal astrocytes (pH(i) = 6.98), and increased rates of recovery from acidification, under nominally CO(2)/HCO(-)(3)-free conditions. Inhibition of NHE1 in the absence of CO(2)/HCO(-)(3) resulted in pronounced acidification of gliomas, whereas normal astrocytes were unaffected. When suspended in CO(2)/HCO(-)(3) medium astrocyte pH(i) increased, yet glioma pH(i) unexpectedly acidified, suggesting the presence of an HCO(-)(3)-dependent acid loading pathway. Nucleotide sequencing of NHE1 cDNA from the gliomas demonstrated that genetic alterations were not responsible for this altered NHE1 function. The data suggest that NHE1 activity is significantly elevated in gliomas and may provide a useful target for the development of tumor-selective therapies.

Acids↗
PubMed1999

Cloning and expression of the Na+/H+ exchanger from Amphiuma RBCs: resemblance to mammalian NHE1.

The cDNA encoding the Na+/H+ exchanger (NHE) from Amphiuma erythrocytes was cloned, sequenced, and found to be highly homologous to the human NHE1 isoform (hNHE1), with 79% identity and 89% similarity at the amino acid level. Sequence comparisons with other NHEs indicate that the Amphiuma tridactylum NHE isoform 1 (atNHE1) is likely to be a phylogenetic progenitor of mammalian NHE1. The atNHE1 protein, when stably transfected into the NHE-deficient AP-1 cell line (37), demonstrates robust Na+-dependent proton transport that is sensitive to amiloride but not to the potent NHE1 inhibitor HOE-694. Interestingly, chimeric NHE proteins constructed by exchanging the amino and carboxy termini between atNHE1 and hNHE1 exhibited drug sensitivities similar to atNHE1. Based on kinetic, sequence, and functional similarities between atNHE1 and mammalian NHE1, we propose that the Amphiuma exchanger should prove to be a valuable model for studying the control of pH and volume regulation of mammalian NHE1. However, low sensitivity of atNHE1 to the NHE inhibitor HOE-694 in both native Amphiuma red blood cells (RBCs) and in transfected mammalian cells distinguishes this transporter from its mammalian homologue.

Amino Acid Sequence↗
PubMed1979

Screening method for vitamins A and D in fortified skim milk, chocolate milk, and vitamin D liquid concentrates.

Vitamin A was determined in fortified chocolate milk and skim milk; vitamin D was determined in fortified chocolate milk, skim milk, and vitamin D concentrates, using reverse phase high pressure liquid chromatography (HPLC). The sample is saponified, extracted with hexane, and chromatographed in an HPLC system on a 10 micron Vydac TP reverse phase C18 column, using acetonitrile-methanol (9+1) as the mobile phase. For 6 replicates, the recoveries of vitamins A and D, using this procedure, were 99 and 98%, respectively.

Animals↗
PubMedDate not supplied

Improved reverse phase liquid chromatographic determination of vitamins A and D in fortified milk.

A method for determination of vitamins A, D2, and D3 on the same 6 mL sample of fortified milk is described. A special indicator permits selection from the cleanup column of a fraction that contains all vitamin D and is free of cholesterol interference for final measurement by reverse phase liquid chromatography. Conservation of analyst's time and expensive solvents results from the relatively small sample processed. The average recoveries and standard deviations were, respectively, 94.1% and 4.8 for vitamin D2, 91.1% and 5.2 for vitamin D3, and 92.2% and 2.6 for vitamin A in nonfat skim milk; 86.5% and 9.4 for vitamin D2, and 83.7% and 4.9 for vitamin D3 in homogenized whole milk. Detectable minima are about 100 IU vitamin A/qt and 50 IU vitamin D2 or D3/qt.

Aluminum Oxide↗