Immersion staining of coarse fish in the Thames

Thirty-one vital dyes were screened for marking bleak, roach and gudgeon by total body immersion in aqueous solutions of the dye. Only six dyes stained without killing, and of these Nile blue, neutral red and Bismarck brown were used successfully in the field. This approach to estimation of population size was abandoned because (1) the toxicity of the dyes varied at different times of year, (2) the numbers needed for release were impractically high and (3) fingerlings showed extremely high mortality on handling.     

Preliminary X-ray study of p-cresol methylhydroxylase (flavocytochrome c) from Pseudomonas putida N.C.I.B. 9869

Single crystals of p-cresol methylhydroxylase, a flavocytochrome c from Pseudomonas putida, have been prepared. The crystals are orthorhombic, space group P212121 with unit cell parameters; a = 140.3 A, b = 130.6 A and c = 74.1 A. They contain a single non-symmetric dimer per asymmetric unit and diffract to at least 2.5 A resolution.     

Crystallographic study of the complex between sulfite and bakers' yeast flavocytochrome b2

The complex between Saccharomyces cerevisiae flavocytochrome b2 and the sulfite anion has been analyzed by x-ray diffraction. A map of the difference in electron density between the complex and the native protein has been computed. One positive peak of electron density is visible at the active site of each of the two subunits in the asymmetric unit, very close to the N-5 of the flavin. The molecular fragment SO3(2-) can account for the shape of this difference in electron density. A third peak is visible in the subunit containing pyruvate, the reaction product. It is a peak of negative electron density localized at the position where the pyruvate usually is in the native form. These results are interpreted on the basis of the mechanism defined in solution for the reaction between flavins and sulfite.     

Analysis of antigens from membrane and soluble fractions of Entamoeba histolytica

Axenic cultures of Entamoeba histolytica strains HK-9, HM-1, and Rahman were fractionated to provide plasma membranes, internal, vesiculated membranes, and a soluble cytosol. Each particulate fraction was solubilized and all fractions were analyzed by techniques designed to demonstrate molecular complexity and serologic reactivity. The cytosol contained more antigenic moieties than either membrane fraction; however, the antigens associated with the membranes had very high reactivity and lower nonspecific activity than the cytosol.     

Gastric Lymphosarcoma and Pseudolymphoma: Reappraisal of 12 Cases of Gastric Lymphosarcoma

Lymphoma localized to one organ is known to have a good prognosis. After a study of 131 cases of lymphosarcoma of the stomach Smith and Helwig³ reported that 42 were in reality a benign lymphoproliferative disorder which has been termed pseudolymphoma of the stomach. Of our series of 12 cases, six are now thought to be pseudolymphoma. Jacobs⁷ has enumerated the differentiating criteria. We have found a polymorphic cellular infiltrate, in nodular or diffuse pattern, associated with a fibrotic reaction located in the submucosa, muscularis or serosa, to be the most helpful criterion. The “good prognosis” associated with gastric lymphoma may be due partly to the difficulty in differentiating these two conditions and to the inclusion of cases of pseudolymphoma in any large series of these lymphomas.     

A new in vitro system for studying cell response to mechanical stimulation : Different effects of cyclic stretching and agitation on smooth muscle cell biosynthesis

An experimental model has been devised to permit morphologic and metabolic characterization of cells subjected to a range of cyclic mechanical stimuli similar to those which may prevail in blood vessel walls. A unique feature is the use of purified elastin membranes prepared from bovine aortas as extensible substrates for cell growth. Cells attached firmly to such membranes which could then be subjected to continuous stretching and relaxation or displacement without stretching by a motor coupled to a movable supporting frame. Various combinations of frequencies, amplitudes and rates of deformation have been used over extended periods with minimal fatigue or disruption of the elastin substrate. The effects of cyclic stretching on [¹⁴C]proline incorporation into protein and collagen and [³H]thymidine incorporation into DNA by rabbit aortic smooth muscle cells were distinct from those attributable to agitation without stretching, indicating that cells responded differently to these modes of stimulation. Increases in rate of protein or DNA synthesis induced by stretching were just as marked after 48 h of stimulation as they were at the outset of an experimental period. Since the system permits observations of cell response to independently variable components of pulsatile stress over extended periods and under a variety of culture conditions, it may be expected to provide new data concerning the interaction of mechanical with hormonal and genetic factors in the elaboration of connective tissue components.     

Tamoxifen fails to block estradiol accumulation, yet is weakly accumulated by the juvenile zebra finch anterior hypothalamus: an autoradiographic study.

In experiment 1, we used autoradiographic procedures to examine whether tamoxifen could displace 3H-estradiol labeling in the anterior hypothalamus and the caudal nucleus of the ventral hyperstriatum (HVc) of ovariectomized 20-day-old female zebra finches. There was no significant reduction in labeling of cells by 3H-estradiol in birds preinjected with unlabeled tamoxifen. In experiment 2, we found that injections of 3H-tamoxifen caused-weak labeling of cells in the anterior hypothalamus of 20-day-old male and female zebra finches. These results are compatible with the idea that tamoxifen does not block the action of estradiol in the brain of zebra finches, and suggest that the effects of early tamoxifen treatment on the morphology of the song system may reflect central actions of tamoxifen.