Insulin regulation of protein biosynthesis in differentiated 3T3 adipocytes. Regulation of glyceraldehyde-3-phosphate dehydrogenase

The effect of insulin on protein biosynthesis was examined in differentiated 3T3-L1 and 3T3-F442A adipocytes. Insulin altered the relative rate of synthesis of specific proteins independent of its ability to hasten conversion of the fibroblast (preadipocyte) phenotype to the adipocyte phenotype. Although more than one pattern of response to insulin was observed, we focused on the induction of a Mr 33,000 protein which was identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Exposure of 3T3 adipocytes to insulin throughout differentiation specifically increased GAPDH activity and protein content by 2- to 3-fold as compared to 3T3 adipocytes differentiated in the absence of insulin. These changes in enzyme activity and content could be accounted for by a 4-fold increase in the relative rate of synthesis of GAPDH and a 9-fold increase in hybridizable mRNA levels. Within 2 h of insulin addition to 3T3 adipocytes differentiated in the absence of hormone, hybridizable GAPDH mRNA levels increased 3-fold, and within 24 h GAPDH mRNA levels increased 8-fold, and [35S] methionine incorporation into GAPDH protein increased 5-fold. The increase in GAPDH mRNA and GAPDH biosynthesis could be demonstrated using physiologic concentrations of insulin (0.24 nM), indicating that these effects are mediated through a specific interaction with the insulin receptor. These studies demonstrate that insulin, as the sole hormonal perturbant, can increase the synthesis of certain 3T3 adipocyte proteins by altering the cellular content of a specific mRNA.     

Dependence of phytoplankton assimilation quotients on light and nitrogen source: implications for oceanic primary productivity

Photosynthetic production of oxygen by phytoplankton assemblagedominated by Peridinium in Lake Kinneret, Israel, generallyexceeds the molar equivalent rate of carbon assimilation. Carbonassimilation occurs only if oxygenic photosynthesis exceedsa light-dependent threshold. Assimilation quotients (mol C molO₂^–1) are a variable function of irradiance, and typicallyonly about one-half of the photoreductant produced during oxygenicphotosynthesis is used for reduction of carbon dioxide. Mostof the residual oxygenic photoreductant probably is used forlight-dependent reduction of nitrate, which competes with carbondioxide for oxygenic photoreductant. Nitrate is an importantsource of nitrogen for this algal assemblage, and light-dependentnitrate reduction probably is much larger than carbon dioxidereduction at lowest irradiances in the euphotic zone. Oxygenproduction also may be much larger than carbon assimilationat low light levels in other environments where oxidized formsof nitrogen are important nitrogenous nutrients for phytoplankton,as in the lower euphotic zone of the sea, where low rates ofcarbon assimilation by phytoplankton have been thought to beinconsistent with the amount of oxygen that accumulates duringsummer.     

Microfluorometric estimates of proteins associated with murine hepatocyte and thymocyte nuclei, residual structures, and nuclear matrix derivatives

Isolated diploid hepatocyte and thymocyte nuclei and their derivatives ("residual structures" and nuclear matrices, as defined by Kaufmann et al. 1981) were evaluated by microfluorometry following reaction with the following fluorochromes: brilliant sulfaflavine (BSF) used at pH 2.8 for the demonstration of total protein; acridine orange (AO) used at pH 9.0 to reveal acidic groups of proteins; and 3-(4-maleimidylphenyl)-7-diethylamino-4-methylcoumarin (CPM) used under conditions required to demonstrate the sum of sulfhydryl (SH) and disulfide (SS) groups of proteins. The results suggested that the proteins reacting with AO and CPM differed from each other and from those revealed by fluorochroming with BSF. In every comparison, hepatocyte nuclei and their derivatives were more fluorescent than the respective populations of thymocyte nuclei and their derivatives. In material fluorochromed with BSF and AO, nuclear matrices were less fluorescent than residual structures, which, in turn, were less fluorescent than intact nuclei. In contrast, nuclear matrices fluorochromed with CPM were less fluorescent than intact nuclei but more fluorescent (paradoxically) than residual structures. The ratios of the total fluorescence values of hepatocyte and thymocyte nuclei fluorochromed with BSF changed significantly during extractions required to produce residual structures and nuclear matrices, while comparable ratios in material fluorochromed with AO or CPM did not change significantly. Comparisons of the ratios of the fluorescence values of intact nuclei and their derivatives in a variety of combinations yielded complex and variable results.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the diphasic nature of vasovagal fainting associated with blood-injury-illness phobia

A detailed psychophysiologic analysis of a vasovagal faint occurring in a "blood-injury-illness" phobic demonstrated that the syncopal episode consisted of a diphasic response. This lends support to the hypothesis that vasovagal fainting in these patients is caused by an overcompensating rebound parasympathetic activation following sympathetic arousal. Treatment and research implications of this finding are discussed.     

Analysis of Cell Types Identifiable In Air-Dried Cell Preparations of Human Testis

Abstract. The mixed cell population of the testicular epithelium has been studied in air-dried cell preparations obtained from a testicular biopsy. Observed cell types are defined, quantified and assigned to cell stages of the spermatogenic cycle. Studies with tritiated thymidine helped to categorize the spermatogonial cell types. Variation in cell size within cell categories, variation in frequency of cells in different categories within individuals, and variation in frequency of cells within categories between individuals were subjected to quantitative analysis.     

Multiple primary cancers in Connecticut, 1935-82

Recently, the National Cancer Institute published a comprehensive monograph on multiple primary cancers in Connecticut and Denmark. This paper summarizes some of the observations made on the Connecticut population. Data compiled by the Connecticut Tumor Registry have extended our knowledge about the patterns of multiple primary cancers, especially among long-term survivors of cancer and among patients with relatively rare tumors about which little information currently exists. When compared with the general Connecticut population, cancer patients had a 31 percent (RR = 1.31) increased risk of developing a second cancer and a 23 percent (RR = 1.23) elevated risk of second cancer at a different site from the first. Common environmental exposures seemed responsible for the excess occurrence of many second cancers, particularly those related to cigarette smoking, alcohol consumption, or both. For example, persons with epithelial cancers of the lung, larynx, esophagus, buccal cavity, and pharynx were particularly prone to develop new cancers in the same or contiguous tissue throughout their lifetimes. Cancers of the colon, uterine corpus, breast, and ovary frequently occurred together, suggesting underlying hormonal or dietary influences. Only patients with prostate cancer were at significantly low risk for second cancer development; this might be an artifact of case finding, since advanced age at initial diagnosis was generally associated with an underascertainment of second cancers. Radiotherapy may have caused rectal and other cancer among patients with cancers of the female genital tract, and leukemia among patients with uterine corpus cancer. Chemotherapy with alkylating agents probably contributed to the excess of acute nonlymphocytic leukemia following multiple myeloma or cancers of the breast and ovary. Genetic susceptibility seemed to explain some tumor complexes, such as the multiple occurrences of cutaneous melanoma and the excess of bone cancer following retinoblastoma. Research into multiple cancer syndromes should enhance our understanding of carcinogenic factors and mechanisms and the development of strategies for cancer prevention and control.     

Transfer of plasmid RP1 into chemolithotrophic Thiobacillus neapolitanus.

RP1, a broad-host-range incompatibility group P1 plasmid specifying multiple drug resistances, has been transferred into the chemolithotrophic bacterium Thiobacillus neapolitanus. The ability of T. neapolitanus to receive, express, and transmit RP1-encoded antibiotic resistances was examined. The data show that this obligate chemolithotroph can accept, replicate, and express heterologous plasmid DNA from a heterotrophic bacterium.