Biomedical subjects

Y Y Tam

Publications and source records attributed to Y Y Tam.

4 recordsLinked to original sources

PubMed2000

Characterization of auxin conjugates in Arabidopsis. Low steady-state levels of indole-3-acetyl-aspartate, indole-3-acetyl-glutamate, and indole-3-acetyl-glucose.

Amide-linked indole-3-acetic acid (IAA) conjugates constitute approximately 90% of the IAA pool in the dicot Arabidopsis, whereas ester-linked conjugates and free IAA account for approximately 10% and 1%, respectively when whole seedlings are measured. We show here that IAA-aspartate Asp, IAA-glutamate (Glu), and IAA-glucose (Glc) are present at low levels in Arabidopsis. Nine-day-old wild-type Arabidopsis seedlings yielded 17.4 +/- 4.6 ng g(-1) fresh weight IAA-Asp and 3.5 +/- 1.6 ng g(-1) fresh weight IAA-Glu, and IAA-Glc was present at 7 to 17 ng g(-1) fresh weight in 12-d-old wild-type seedlings. Total IAA content in 9-d-old Arabidopsis seedlings was 1, 200 +/- 178 ng g(-1) fresh weight, so these three IAA conjugates together made up only 3% of the conjugate pool throughout the whole plant. We detected less than wild-type levels of IAA-Asp and IAA-Glu (7.8 +/- 0.4 ng g(-1) fresh weight and 1.8 +/- 0.3 ng g(-1) fresh weight, respectively) in an Arabidopsis mutant that accumulates conjugated IAA. Our results are consistent with IAA-Asp, IAA-Glu, and IAA-Glc being either minor, transient, or specifically localized IAA metabolites under normal growth conditions and bring into question the physiological relevance of IAA-Asp accumulation in response to high concentrations of exogenous IAA.

Arabidopsis↗

PubMed1998

Determination of indole-3-pyruvic acid levels in Arabidopsis thaliana by gas chromatography-selected ion monitoring-mass spectrometry.

A rapid and simple method is described for the determination of indole-3-pyruvic acid (IPA) levels in Arabidopsis thaliana by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS). The method includes derivatization of IPA with hydroxylamine in the crude extract, followed by ethyl acetate partitioning, solid-phase extraction with C18 resin, reversed-phase high-performance liquid chromatography (HPLC), and GC-SIM-MS. Three derivatizing reagents were tested; these were pentafluorobenzylhydroxylamine, pentafluorophenylhydrazine, and hydroxylamine. Hydroxylamine proved to be the most useful, as the IPA-oxime was easiest to purify from plant extracts and was the most stable. IPA was quantified in Arabidopsis seedlings ranging in age from 5 to 12 days; levels varied from 4 to 13 ng/g, peaking at 7-9 days.

Arabidopsis↗

PubMed1986

Studies on shrew (Suncus murinus) epidermal growth factor.

The shrew SMG contains a very high level of EGF. By heterologous radioreceptor assay, the EGF content was determined to be about 300 pmol/mg wet weight in the male. The content is sex dependent; in the female gland, it is only 4% of the male gland level. EGF level and EGF receptor content in other tissues showed a reciprocal distribution pattern with the parotid gland containing the second highest level of EGF and the liver containing the largest amount of EGF receptor. Shrew EGF is heat stable. It could induce early eyelid opening and incisor eruption in neonatal rat pups at a very low dose level. There is apparently no high molecular weight form of EGF in shrew tissues and body fluids. However, gel chromatography revealed that the foetus contained multiple forms of EGF. The contribution of a high EGF level to the active life in adult shrews and the exceptionally high growth rate in shrew pups are discussed.

Animals↗

PubMed1985

Isolation of the epidermal growth factor from the shrew submaxillary gland.

The epidermal growth factor (EGF) from the submaxillary glands of the Chinese Shrew (Suncus murinus) is purified to apparent homogeneity by using a sequence of four chromatographic steps, viz. gel filtration on Sephacryl S-200, affinity chromatography on immobilized Ni, hydrophobic interaction on phenyl-Sepharose CL-4B and reverse-phase HPLC. An 800-fold increase in specific activity and an overall recovery of 46% were achieved. The most effective step in its purification is the successful use of immobilized metal ion affinity chromatography (IMAC). This method was very selective, reproducible and requires a minimum of sample pre-treatment prior to chromatography.

Animals↗