The Use of Membrane Electrical Noise in the Study of Characean Electrophysiology

The technique of examining membrane properties through the useof endogenous electrical noise is applied to the study of Characeanelectrophysiology. The frequency band between 0·1 and1·0 Hz is particularly sensitive to the metabolic stateof the cell. It is concluded that measurements of the powerspectral density function and the low frequency excess noisewill prove a useful adjunct to the normal measurements of restingpotential and membrane resistivity.     

Emergency Resection in Treatment of Diverticular Disease of Colon Complicated by Peritonitis

Of a consecutive series of 25 patients with peritonitis secondary to colonic diverticular disease all, except one with faecal peritonitis, underwent some form of emergency resection.All the three patients with faecal peritonitis died, but the 22 with purulent peritonitis survived. The average duration of the emergency admission of the 22 survivors was 25.4 days, and in nine (41%) of them intestinal continuity had been restored by the end of that admission.Thus some form of emergency resection is the operation of choice in patients with spreading peritonitis due to diverticular disease of the sigmoid colon.     

THE ENDOCRINE BASIS OF PAIR-FORMATION BEHAVIOUR IN THE MALE EIDER SOMATERIA MOLLISSIMA

Pair-formation behaviour among the Eiders began after the annual moult, in late September. There was a small peak of display in October and November and a large one in the following April and May. As a result, the female population became paired in two phases, up to 50% in the autumn and the remainder in the following spring. The seasonal cycle of the abundance of Leydig cells was bimodal, with a peak in October and a large one in April-May. That the peaks represent increased androgen production was supported by the cycles of Leydig cell enzyme activity and lipid content and of penis weight. The monthly means of Leydig cell abundance and of the rate of display were statistically correlated. Experiments with sexually quiescent males in eclipse plumage demonstrated that testosterone was capable of inducing pair-formation behaviour. Relatively advanced stages of spermatogenesis were found in autumn, and were maintained through the winter, complete development occurring in the spring. Seasonal changes in the production of pituitary gonadotropin followed a bimodal pattern with peaks in autumn and in the spring. Field evidence is presented which suggests that Follicle Stimulating Hormone and Luteinizing Hormone were produced at different phases of a circadian rhythm of photosensitivity.     

The interaction of human plasma glycoaminoglycans with plasma lipoproteins.

Modifications of existing methods have allowed for the isolation and purification of various species of plasma glycosaminoglycans on the basis of their sulfate content and molecular size. All of the preparations precipitated human plasma low density lipoproteins (LDL); maximal precipitation occurred with amounts of glycans corresponding to 50 mug of hexuronate and 12 mg of LDL. The interaction of glycans with pyrene-labeled lipoproteins was also studied, measuring variations of the fluorescence emitted by the monomer (M) and excimer (E) species of the bound pyrene. The ratio IE/IM is proportional to c/eta, where c is the microscopic concentration of the pyrene confined to the hydrocarbon region of the lipoprotein and eta is the microviscosity of that region. To 0.12 mg of pyrene-labeled LDL, very low density lipoproteins (VLDL) or high density lipoproteins (HDL) were added increasing amounts of the various glycan preparations. The sulfate-rich species decreased the IE/IM ratio of LDL and HDL but not that of VLDL. This finding suggests that the glycan caused a change in lipoprotein conformation associated with either an increased volume or increased microscopic viscosity of the hydrocarbon region. The modification of LDL conformation could be prevented by proteolytic treatment of the sulfate-rich species or by addition to the system of suitable amounts of sulfate-poor species or of chrondroitin-4-sulfate, but could not be prevented by increased ionic concentration. These results suggest that the two main species of plasma glycans are important in maintaining adequate rheological properties of plasma lipoproteins.     

A Multi-Unit Sampling System and Its Use in the Characterization of Ultradian and Infradian Growth in Tetrahymena*

SYNOPSIS. A multi-unit automatic sampling device for investigation of microbial growth under a wide variety of conditions is described. The kinetics of asynchronous population growth for batch cultures of Tetrahymena pyriformis (W) at several temperatures show that there are 2 distinct growth phases: an exponential ultradian growth phase that is strongly temperature dependent and a non-stationary growth phase, the infradian phase, that shows little or no temperature dependence over the range from 15–27 C.     

Separation and Identification of the Polar Lipids of Chromatium Strain D

The polar lipids of the autotrophically grown, obligately anaerobic, photosynthetic bacterium Chromatium strain D were separated by paper chromatography. Four major phospholipids were identified: lysophosphatidylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. In addition, three glycolipids were observed and characterized, namely, monoglucosyldiglyceride, which is found in other biological systems, and (mannosyl, glucosyl)-diglyceride and (dimannosyl, glucosyl)-diglyceride, which heretofore have not been observed in nature.     

The effect of age on the antigen-presenting mechanism in limiting dilution precursor cell frequency analysis

We have utilized limiting dilution analysis (LDA)2 to compare the intrinsic precursor cytotoxic T lymphocyte (pCTL) frequency for influenza-plus-self in young and old C57BL/6 mice. Under conditions of excess interleukin 2 (IL-2) and antigen presenting cells (APC) derived from spleens of mice matched in age to those being tested, we found more than a twofold difference in pCTL frequency between young and old animals. However, there was no difference in pCTL frequency between the two age groups if antigen was presented to the old responder cells on spleen cells derived from young mice. The apparent decrease in pCTL frequency in old mice by standard LDA may in fact be due to a defect in the antigen processing and/or presentation mechanism of old spleen cells. We conclude that the age-associated defective CTL activity previously reported by us and by others may be due at least in part to a defect in the antigen presentation mechanism of aging mice.