TEMPORARY ABOLITION OF PHOTOTROPISM IN LIMAX AFTER FEEDING

When fed upon cooked potato the slug Limax maximus becomes for a day or more indifferent to light—its natural negative phototropism is suppressed. This effect is not produced by raw potato or other diets; it can be duplicated by injection of sugar solutions into the stomach or into the body fluids, and seems to be due to sugar absorbed during the digestion of the cooked starch. The fact is of interest particularly for the suggestion which it affords as to the explanation of fluctuations in conduct.     

SCINTIGRAMS OF THE THYROID GLAND—The Diagnosis of Morphologic Abnormalities with I131

Functioning thyroid tissue containing sufficient radioiodine can be visualized by scanning the gland with a directional scintillation counter.⁴ This visual representation of the gland is called a “scintigram.” Scintigrams have been invaluable in the detection and study of both “toxic” and non-functioning nodules, diffuse enlargement in hyperthyroidism and the subsequent reduction in gland size after treatment, carcinoma, and aberrant thyroid tissue.     

The relationship between cell volume,ploidy, and functional activity in differentiating hepatocytes

Liver cells were isolated by collagenase perfusion from rats of 1 day, and 1, 3, 5, and 12 weeks of age, fractionated by velocity sedimentation at 1g (STAPUT), and the major cell types were identified in terms of specific functions. Alphafetoprotein and albumin were used as markers of differentiating hepatocytes and these functional activities were evaluated in a quantitative manner using a radio-immunoassay. The capacity of this cell type to store³⁵S-BSP, an indicator of bile formation, was also evaluated. Sinusoidal cells and hematopoietic cells were identified on the basis of their ability to take up^99mTC-colloid sulfur and to incorporate⁵⁹Fe, respectively. The fractionation procedure allowed a good separation of sinusoidal cells from hepatocytes at all postnatal ages and also of erythroid cells still present during the first week after birth. With increasing age, alphafetoprotein-producing hepatocytes exhibited changes in sedimentation velocities that parallelled those of albumin-producers. In turn, the latter hepatocyte subpopulation underwent gradual shifts in modal peak velocities similar to those of bile-forming hepatocytes. The fractionated hepatocytes obtained at different ages were further analyzed in terms of cell volume and nuclear ploidy using a Coulter counter system. This quantitative analysis obtained at the cellular level demonstrated that during the age-related differentiation of hepatocytes, which occurs during the postnatal period and results in the gradual appearance of cells of higher ploidy levels, the extent of albumin production and bile formation can be correlated with the hepatocyte volume.     

A New Framework to Accurately Quantify Soil Bacterial Community Diversity from DGGE

Denaturing gradient gel electrophoresis (DGGE) has been and remains extensively used to assess and monitor the effects of various treatments on soil bacterial communities. Considering only abundant phylotypes, the diversity estimates produced by this technique have been proven to be uncorrelated to true community diversity. The aim of this paper was to develop a framework to estimate a community’s true diversity from DGGE. Developed using in silico DGGE profiles generated from published pyrosequencing datasets, this framework elongates the rank-abundance distributions (RADs) drawn by band quantification using the peak-to-signal ratio (PSR) parameter, which was proven to be related to bacterial richness. The ability to compare DGGE-based diversity estimates to the true diversity of communities led to a unique opportunity to identify potential pitfalls when analyzing DGGE gels with commercial analysis software programs and gain insight into the process of DNA band clustering in the profiles. Bacterial diversity was compared through richness, Shannon, and Simpson’s 1/D indices. Intermediate results demonstrated that, even though commercial gel analysis software programs were unable to produce consistent results throughout all samples, a newly developed Matlab-based framework unraveled the dominance profiles of communities from band quantification. Elongating these partial RADs using the PSRs extracted from the DGGE profiles chiefly made it possible to accurately estimate the true diversity of communities. For all the samples analyzed, the estimated Shannon and Simpson’s 1/D were accurate at ±10 %. Richness estimations were less accurate, ranging from ?11 to 31 % of the expected values. The framework showed great potential to study the structure and diversity of soil bacterial communities.