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Biomedical subjects

C S Nicholson-Guthrie

Publications and source records attributed to C S Nicholson-Guthrie.

8 recordsLinked to original sources
PubMed2001

Urine GABA levels in ovarian cancer patients: elevated GABA in malignancy.

The association of malignancy with elevated diamine oxidase (DAO), an enzyme producing gamma-aminobutyric acid (GABA) is well documented. In ovarian cancer, increased DAO occurs in the malignant tissues and plasma. Since higher DAO levels cause GABA accumulation, elevated GABA may occur in ovarian cancer and be reflected in urine. We tested this hypothesis and found that half the ovarian cancer patients had a clearly elevated urine GABA, a result that is in agreement with previous reports on DAO and malignancy. The published findings on DAO, GABA and malignancy suggest that elevated GABA is associated with cancer. This proposal could lead to a GABA urine monitor or new directions in cancer treatment or research.

Adult↗
PubMed2000

A bacterial high-affinity GABA binding protein: isolation and characterization.

A gamma-aminobutyric acid (GABA) binding protein (GBP) was isolated from a bacterial mutant which has high-affinity GABA binding characteristics comparable with the GABA(A) brain receptor in mammals. The GBP was partially purified and characterized and was shown to be a periplasmic protein of approximately 42,000 molecular weight. To determine the molecular weight, a bacterial GABA binding assay was used with SDS-PAGE. This procedure did not require large amounts or complete purification of protein and may be useful as a simple method in estimating the molecular weight of other bacterial binding proteins.

Animals↗
PubMed1995

Bacterial assay for quantitative measurement of nanomolar concentrations of a metabolite.

A mutant of Pseudomonas fluorescens was used to develop a radioligand, competitive binding assay to quantitatively measure gamma-aminobutyric acid. The highly reliable and reproducible assay was sensitive (nM detection), rapid, and easy to perform. Nonspecific activity and scatter were insignificant. Radiolabel was irreversibly fixed by the cells in an energy-dependent reaction. The finding that a bacterium was effective in quantitatively detecting nanomolar amounts of a metabolite suggests that other bacteria or their mutants might be used in competitive binding assays to detect and quantify amino acids or other substances occurring in trace amounts.

Animals↗
PubMed1995

Determination of gamma-aminobutyric acid levels in human cerebrospinal fluid using Pseudomonas.

The principle objective was to demonstrate the efficacy of a bacterial, radioligand, competitive binding method in determining gamma-aminobutyric acid (GABA) levels in human cerebrospinal fluid (CSF). In a double blind study, CSF GABA concentrations were measured by the bacterial method using a mutant of Pseudomonas fluorescens and by a standard radioligand competitive binding assay using rat brain membranes. Linear regression analysis demonstrated a highly significant correlation (r = 0.84; P < 0.001) between the two methods. In an ancillary study, a similar correlation (r = 0.90; P < 0.001) was found between the bacterial method and HPLC, another standard procedure in determining CSF GABA levels. Furthermore, the mean CSF GABA measurements found with the bacterial method were in agreement with those reported in the literature using the brain membrane method or HPLC. The bacterial method was highly reproducible and reliable with a detection to 5 nM GABA. It was specific for GABA and was not affected by other naturally occurring compounds which are found in higher concentrations in CSF than GABA or which were suspected to interfere with the neurotransmitter in a binding assay. The bacterial radioligand method was shown to be an accurate, sensitive, and rapid assay for CSF GABA.

Adult↗
PubMed1989

gamma-Aminobutyric acid uptake by a bacterial system with neurotransmitter binding characteristics.

gamma-Aminobutyric acid (GABA), an amino acid, has been found in every class of living organisms. In higher organisms, GABA is a neurotransmitter and binds with high affinity and specificity to GABA receptors on neurons in a sodium-independent reaction that is saturable. The role of GABA in organisms lacking nervous tissue is not known. This report describes, in a strain of Pseudomonas fluorescens, a GABA uptake system with binding characteristics like those of the GABA (type A) brain receptor. The binding was saturable and specific for GABA, was sodium-independent, was of high affinity (Km = 65 nM), and was inhibited competitively by muscimol, a potent GABA analogue. The bacterial GABA system included a homogeneous binding site, and no cooperative interaction was found between sites. To our knowledge, such a system for GABA, or other neurotransmitters, in a bacterium has not been reported.

Binding, Competitive↗
PubMed1987

Accumulation of protoporphyrin-IX by the chlorophyll-less y-y mutant of Chlamydomonas reinhardtii.

A pigment accumulating in a Mendelian mutant (y-y) of Chlamydomonas reinhardtii, which has essentially no chlorophyll and lacks inner chloroplast membranes in the light and dark, was isolated and characterized. It was identified as protoporphyrin-IX (PROTO) by spectral analysis using two different methods of extraction and fractionation. The amount of PROTO was estimated to be 10(7) molecules per cell. Since PROTO was the only intermediate of chlorophyll biosynthesis that accumulated, we conclude the y-y lesion in the pathway is after PROTO.

Chlamydomonas↗