Homeodomain transcription factor NKX2.2 functions in immature cells to control enteroendocrine differentiation and is expressed in gastrointestinal neuroendocrine tumors

The homeodomain transcription factor NKX2.2 is necessary for neuroendocrine (NE) differentiation in the central nervous system and pancreas. NE tumors derived from the gut are defined by their NE phenotype, which is used for diagnosis and contributes to tumorigenicity. We hypothesized that NKX2.2 is important for NE differentiation in normal and neoplastic gut. NKX2.2 and NE marker expression was investigated in the small intestine of embryonic and adult mice using immunofluorescence (IF). To determine the role of NKX2.2 in NE differentiation of the intestine, the phenotype of Nkx2.2 (-/-) mice was examined by IF and real-time (RT)-PCR. NKX2.2 and NE marker expression in human NE tumors of the gut and normal tissues were evaluated by immunohistochemistry and qRT-PCR. NKX2.2 expression was detected in the intervillus/crypt regions of embryonic and adult mouse intestine. Co-expression of Nkx2.2 with neurogenin3 (NEUROG3) and hormones was observed in the adult intestinal crypt compartment, suggesting NKX2.2 functions in NEUROG3-positive endocrine progenitors and newly differentiated endocrine cells. In the intestine of Nkx2.2 (-/-) mice, we found a dramatic reduction in the number of cells producing numerous hormones, such as serotonin, gastrin, cholecystokinin, somatostatin, glucagon-like peptide 1 (GLP-1), and secretin, but an increase in cells producing ghrelin. NKX2.2 was expressed in most (24 of 29) human NE tumors derived from diverse primary sites. We conclude NKX2.2 functions in immature endocrine cells to control NE differentiation in normal intestine and is expressed in most NE tumors of the gut, and is therefore a novel target of diagnosis for patients with gastrointestinal NE tumors.

Tear fluid content of electrochemically active components including water soluble antioxidants

PURPOSE

To describe the content of water-soluble antioxidants in tear fluid.

METHODS

We collected tear fluid from healthy subjects, either into borosilicate glass tubing or by absorption onto Schirmer strips. High pressure liquid chromatography with electrochemical detection provided data on several components in a single assay. The system was sufficiently sensitive to provide reliable values for components present in tear fluid collected at normal (basal) or stimulated rates of secretion.

RESULTS

Tear fluid at basal secretion was found to contain four compounds often considered to function in biology as antioxidants. Ascorbic acid (AA) is found at 665 microM, tyrosine at 45 microM and glutathione (GSH) at 107 microM. Cysteine (48 microM) and uric acid (328 microM) are reported for the first time; the latter is somewhat controversial as a physiologically active antioxidant. One peak on the chromatogram was consistently present but has not been identified. During stimulation of flow by brief inhalation of ammonium hydroxide fumes, the concentration of each compound was lower.

CONCLUSION

This work demonstrates the presence of electro-chemically active components that might function as antioxidants at the anterior surface of the cornea against potential damage from radiation, oxygen toxicity, abrasion and environmental chemicals.

Properties of electrochemically active components in mammalian vitreous humor

Antioxidants are considered to have important roles in protecting the eye against radiation, oxygen toxicity and other threats. Several water-soluble electrochemically-active compounds that might function as antioxidants in vitreous humor of rabbit, rat and bovine eyes were identified and quantitated. In that the rat is a nocturnal animal species and the other two are diurnal, the results allow a tentative evaluation on the comparative physiology of light-dark behavior patterns that influence this ocular fluid. All analyses were performed by HPLC with electrochemical detection. The utility of this approach is that components of vitreous humor can be identified by their retention time and by their characteristic response when the voltages of the two sensing electrodes are progressively brought together. Four compounds regarded as functional antioxidants in the animal kingdom were identified and quantitated. Other antioxidants known to be present in several biological fluids are not present at detectable or significant levels in vitreous humor; metabolites or precursors of these might be present in trace quantities.

An apparatus for ultraviolet B irradiation of small volumes of biological fluid under controlled oxygen tension

BACKGROUND

The design, construction, and calibration of a unique apparatus for ultraviolet (UV) B irradiation of small volumes of biological fluid under temperature-controlled open atmospheric or closed cell conditions of defined Po2 is described.

METHODS

The apparatus consists of a custom designed UV transmissible quartz silica 3 port spectrophotometric cuvette coupled to a deuterium UV B source by UV transmissible fiber optics. Fluid movement, temperature regulation, dosimetry, and miniaturized biosensors for oxygen, pH, and temperature are described along with a preliminary experiment.

RESULTS

The apparatus produces a known photochemical effect using an endogenous aqueous humor UV B photosensitizer-L tryptophan. UV B radiation is contained, thus protecting laboratory personnel. The system provides a continuous spectral UV B dose of 30 mJ/cm2/hr, which is equivalent to approximately 5.5 UV sunlight hours reaching an aliquot of mammalian aqueous humor.

CONCLUSIONS

This biophysical apparatus can be used to investigate antioxidant protective systems in ocular fluid (aqueous/vitreous humors and tears), and is also applicable to evaluating the interaction of radiation with ocular and nonocular tissue cell homogenate.