Development of GnRH cells: Setting the stage for puberty.

Cells containing gonadotropin-releasing hormone (GnRH) are essential not only for reproduction but also for neuromodulatory functions in the adult animal. A variety of studies have hinted at multiple origins for GnRH-containing cells in the developing embryo. We have shown, using zebrafish as a model system, that GnRH cells originate from precursors lying outside the olfactory placode: the region of the anterior pituitary gives rise to hypothalamic GnRH cells and the cranial neural crest gives rise to the GnRH cells of the terminal nerve and midbrain. Cells of both the forming anterior pituitary and cranial neural crest are closely apposed to the precursors of the olfactory epithelium during early development. Disruption of kallmann gene function results in loss of the hypothalamic but not the terminal nerve GnRH cells during early development. The GnRH proteins are expressed early in development and this expression is mirrored by the onset of GnRH receptor (GnRH-R) expression during early development. Thus the signaling of the GnRH neuronal circuitry is set up early in development laying the foundation for the GnRH network that is activated at puberty leading to reproductive function in the mature animal.

Influence of internal scattering on the optical properties of particles and drops in the near infrared.

A geometric optics approximation is used to compute the near-infrared absorption by particles containing internal scatterers, such as bubbles, occlusions, or other refractive-index inhomogeneities. If the probabilities of absorption and scattering are comparable, absorption by a weakly absorbing particle can be increased substantially beyond that in the absence of internal scattering. Although the geometric optics approach limits the range of applicability of the results, the effects are not necessarily restricted to particle dimensions and wavelengths where geometric optics is accurate.

Reflectance and albedo differences between wet and dry surfaces.

It is commonly observed that natural multiple-scattering media such as sand and soils become noticeably darker when wet. The primary reason for this is that changing the medium surrounding the particles from air to water decreases their relative refractive index, hence increases the average degree of forwardness of scattering as determined by the asymmetry parameter (mean cosine of the scattering angle). As a consequence, incident photons have to be scattered more times before reemerging from the medium and are, therefore, exposed to a greater probability of being absorbed. A simple theory incorporating this idea yields results that are in reasonable agreement with the few measurements available in the literature, although there are differences. Our measurements of the reflectance of sand wetted with various liquids are in reasonably good agreement with the simple theory. We suggest that the difference between reflectances of wet and dry surfaces may have implications for remote sensing.

Enzyme-labeled immunosorbent assay for serum ferritin: method evaluation and comparison with two radioassays.

We report our evaluation of a commercially available procedure and reagents for determination of ferritin in serum by enzyme-labeled immunosorbent assay (ELISA). Results by our procedure and the "Fer Iron" (Ramco Labs) procedure shows a degree of association (r) of 0.95 and a regression equation of y = 1.03x - 33. Similarly, our procedure compared to the "Gamma Dab" (Clinical Assays) ferritin procedure shows a degree of association of 0.98 and a regression equation of y = 0.93x - 11. Between-day standard deviations were 6 and 22 micrograms/L (n = 24 and 20) for ferritin concentrations of 20 and 300 micrograms/L, respectively. Ferritin values showed no correlation with total iron concentration, but show a broad inverse relationship with iron-binding capacities. The favorable correlation with existing procedures and the speed of the analysis commend the use of ELISA for measurement of ferritin in serum.

A practical radioimmunoassay of thyroglobulin.

We describe a reliable and convenient double-antibody radioimmunoassay for human thyroglobulin that can be performed within two days. Analytical recoveries were quantitative and immunological equivalence between several sources of human thyroglobulin was demonstrated. Cross reactivity with either thyroxine or triiodothyronine was insignificant. The between-day coefficient of variation in the 5--100 mug/liter range was 10%. The range observed for 68 normal individuals was 2--61 microgram/liter.

Sensitive radioimmunological screening test for antithyroglobulin autoantibodies.

The test described here was designed as a screening test to be used in conjunction with the radioimmunoassay for human thyroglobulin. Anti-thyroglobulin autoantibodies, when present even in low concentrations, interfere with thyroglobulin determination. A 30-min incubation allows binding of 125I-thyroglobulin to endogenous anti-thyroglobulin autoantibodies. A subsequent 2-h incubation with goat anti-human gamma-globulin causes precipitation of such complexes. The immunoprecipitable radioactivity reflects the binding capacity of the sample for 125I-labeled thyroglobulin. Samples that are devoid of autoantibodies, and are therefore suitable for valid thyroglobulin determinations, bind less than 6% of the radiolabeled thyroglobulin. The sensitivity of this radioimmunoassay exceeds that of the tanned-erythrocyte hemagglutination test.

Purification of alpha1-fetoprotein.

Previously published methods for purifying alpha1-fetoprotein are inadequate because they either do not yield a completely pure product or they cause some denaturation. We present a method that does not have these serious disadvantages, and with which alpha1-fetoprotein was purified by sequential use of concanvalin A affinity-chromatography, preparative gel-electrophoresis, and immunoabsorption with anti-albumin antibody covalently coupled to Sepharose 4B. The purity of the product was monitored by discontinuous polyacrylamide-gel electrophoresis and counterimmunoelectrophoresis, both of which must be used to ascertain what proteins are present at each step of the purification.

Immunofluorescence method for detecting anti-myocardial antibodies, and its use in diagnosing heart disease.

Demonstration of autoimmune antibodies to myocardial tissue enables one to detect and assess cardiac disease long after abnormalities in serum enzyme activities are no longer measurable. We describe and indirect immunofluorescence procedure in which cryostat sections of rat heart (ventricle) and Evan's Blue counterstaining are used to detect anti-myocardial antibodies. Sena from patients with myocardial infarct or some other cardiac diseases reveal a distinct fluorescent staining of the sarcolemmal membrane. In contrast, sera from patients with systemic lupus erythematosis demonstrate nuclear plus diffuse staining and sera from myasthenia gravis patients show a characteristic striated staining pattern. The role of anti-myocardial antibodies in cardiac disease is discussed briefly.

Radioimmunoassay for triiodothyronine: use of polyethylene glycol to precipitate immune complexes.

1. A rapid radioimmunoassay (RIA) for determining serum triiodothyronine (T3) concentration has been developed. The reaction of T3 with its antibody was performed at 37 degrees C for 3 hours; precipitation of antibody bound T3 by 15% polyethylene glycol (PEG) was done at ice-bath temperatures. 2. The effects of pH on the interaction of T3 with its antibody and on the precipitation of antibody gamman globulin by PEG are discussed. 3. PEG precipitates and supernatants were characterized by immunoelectrophoresis and polyacrylamide gel electrophoresis. 4. The RIA has a between run precision of 9.3% at a mean T3 concentration of 179 ng/dl. The recovery of 50 or 100 ng/dl T3 was 95-102% and the normal range estimate was 66-215 ng/dl (N equal to 49).

Statistical evaluation of method-comparison data.

Comparison of two methods for determining a substance is a common procedure in clinical chemistry. Almost without exception, normal theory statistics are used with the tacit assumption that the data under test show gaussian distributions. Experience has led us to question this assumption for populations of differences between values obtained by two methods applied to common samples and for populations of paired values for each method as used in correlation analysis. Data are presented from our laboratory to illustrate these points, as well as an examination of data from relevant papers that appeared in this journal from 1968 through 1973. These examples indicate that incorrect interpretation of results because of insufficient attention to non-gaussian distribution is a real and present danger. We present a systematic approach to the statistical aspect of comparing methods that enables one to avoid this problem.

Information content in remote sensing.

The relation between eigenvalues of the kernel covariance matrix in inversion problems and the number of pieces of information that can be extracted is discussed. It is shown that an example given by Wang and Goulard, which was claimed to show that the eigenvalue analysis underestimated the information content, was incorrectly calculated.