MICROBODIES IN EXPERIMENTALLY ALTERED CELLS

A rapid and sustained increase in the number of microbodies in liver and kidney cells can be induced in male rats by ethyl chlorophenoxyisobutyrate (CPIB), a hypolipidemic drug. This phenomenon permits investigation of several aspects of microbody behavior in experimental conditions. Reversal experiments demonstrate that liver cells revert to normal between 2 and 3 weeks after withdrawal of CPIB and that one of the mechanisms for removal of excess microbodies is their incorporation into structures indistinguishable from lysosomes. In a state of rapid cell division, such as that present during liver regeneration, microbody proliferation apparently occupies a high biological priority. In necrotic or degenerating cells microbody structure remains relatively normal. The increase in microbodies induced by CPIB is inhibited by chloramphenicol. No increase in microbodies occurred in female rats or in chickens, guinea pigs, or rabbits at the dosage used (0.25% in diet). No changes in microbodies were seen in monkey liver. Catalase activity was generally parallel to the numerical response in microbodies. Additional observations suggest that the microbody response to CPIB is not related to hepatomegaly induced by this agent but may be related to the hypolipidemic effect of CPIB, though hypolipidemia per se is not a specific or sufficient cause of microbody proliferation.     

Inhibition of Host Protein Synthesis in Type 5 Adenovirus-infected Cells

The effect of type 5 adenovirus infection on the synthesis of host-cell proteins by suspension cultures of KB cells was investigated. Although total protein synthesis continued at a constant rate for approximately 36 hr, net synthesis of five host enzymes (lactic dehydrogenase, acid phosphatase, deoxyribonuclease, fumarase, and phosphoglucose isomerase) was found to stop 16 to 20 hr after infection. The synthesis of alkaline phosphatase stopped 9 to 12 hr after infection. The inhibition of host protein synthesis occurred shortly after the synthesis of viral antigens had begun, accounting for the continued synthesis of total protein. An investigation of the relationship between synthesis of viral antigens and inhibition of host protein synthesis yielded results which suggest that the two processes are in some way coupled.     

Physiological Studies on Pea Tendrils. III. ATPase Activity and Contractility Associated with Coiling

Extracts of the tendrils of Pisum sativum, Var. Alaska, exhibit adenosine triphosphatase activity which is inversely proportional to the amount the tendrils have coiled. The specific viscosity of the extract decreases when ATP is added. This evidence indicates a possible role of a contractile adenosine triphosphatase in coiling.     

SENSORY DEPRIVATION ON AN EYE SERVICE—Its Significance and Management

In a detailed investigation of 174 patients who wore patches over both eyes after ocular operations, some 35 per cent were observed to have one or more symptoms of mental aberrations. In a smaller group who had repair of retinal detachment and therefore had to wear eye patches for a much longer time, the incidence of mental symptoms was 100 per cent. A common symptom called “noncompliance” was found which has hitherto been regarded simply as lack of cooperation by the patient.The incidence of postoperative complications was considerably higher in patients who had symptoms of mental disturbance than in those who did not.In these circumstances it would appear worth while to prepare the patient mentally for operation, to give him assurances beforehand, and to take measures to reduce his “isolation” while he has to wear patches.     

Electron Microscopic Observations on the Three-Dimensional Morphology of Apatite Crystallites of Human Dentine and Bone'

In sections of human dentine (carious and sound) and bone examined with the electron microscope, apatite crystallites were seen to present long thin profiles somewhat suggestive of a cylindrical shape, broad profiles indicative of a plate-like shape, and profiles intermediate between these two extremes. With a special stereoscopic specimen holder allowing the specimen to be tilted through an angle of 30° it was possible to record images of two profiles of the same crystallite from different angles and thus gain information concerning the 3-dimensional morphology of crystallites showing a thin profile. In all fields so examined, the thin-profile crystallites that were properly oriented with respect to the axis of tilt exhibited a different width dimension in each of the two micrographs. From this it is concluded that the thin profiles actually represented edge views of plate-like crystallites.     

The Effect of Polarized Light on the Growth of a Transparent Cell : A theoretical analysis

It is shown that light lost by reflection before entering a clear and homogeneous sphere or infinite cylinder is precisely compensated by light retained within these bodies by internal reflection; compensation means that the total rate of light absorption by infinitely dilute photoreceptors as integrated through the whole of these bodies or even through any concentric or coaxial shell making them up is independent of surface reflection. In the Phycomyces sporangiophore this theorem precludes a reflection explanation of R, the polarization dependence of the light growth response. An alternative explanation based upon anisotropic absorption by the receptors is explored and found tenable. Formulae are derived for R in any transparent cylindrical cell as a function of the constants of anisotropic absorption by the photoreceptors taken as a group (C_H' and C_L'), of the radial position of the receptors, and of the refractive indices of the cell (n) and of the medium (N). It is inferred that the photoreceptors in the Phycomyces sporangiophore are most absorbent for light vibrating in the direction of a hoop around a barrel. Orientation of the receptors by linkage to the cell wall is then shown to be a plausible explanation of the inferred anisotropy. On the basis of anisotropic reception, it is predicted that R should be constant for any N > n, and it is shown how C_H', C,_L' and the radial position of the receptors may all be obtained from a careful determination of R as a function of N.     

ELECTROKINETIC PHENOMENA : XIII. A COMPARISON OF THE ISOELECTRIC POINTS OF DISSOLVED AND CRYSTALLINE AMINO ACIDS

1. Although the isoelectric points of dissolved cystine, tyrosine, and aspartic acid molecules lie at widely differing pH values, the isoelectric points of the surfaces of these substances in the crystalline state are all near pH 2.3. This was found to be true in solutions of hydrochloric acid and in acetate buffers of approximately constant ionic strength. 2. When suspended in gelatin, tyrosine and cystine crystals adsorb the protein and attain a surface identical in behavior with gelatin-coated quartz or collodion particles. 3. Aluminum ions at low concentrations reduce the electric mobilities of tyrosine crystals to zero in a manner analogous to their effect on other surfaces. 4. Alkyl benzene droplets also have their electric mobility reduced to zero at low pH values but, unlike the amino acids, a change in sign was never noticed. 5. The mobility of tyrosine crystals is independent of crystal length between 2–100µ. Below this size the mobilities are decreased. 6. These results are discussed in connection with the concept of the general definition of the isoelectric point and the behavior of certain insoluble proteins such as wool and silk fibroin.