Human autologous rosettes. I. Mechanism of binding of autologous erythrocytes by T cells.

A population of human peripheral blood lymphocytes is able to bind autologous erythrocytes in the presence of autologous serum. Erythrocyte binding is found to be more efficient at 4 °C after preincubation of lymphocytes in autologous serum for 30 min followed by overnight incubation. The overall cellular concentration and erythrocyte/lymphocyte ratio are also crucial in determining the weak erythrocyte binding to autologous lymphocytes. Membrane proteins are involved since the binding structures are sensitive to protease treatment. The 26% RFC obtained with an optimized assay are related to the T-cell lineage.     

Confertdiolide,a novel sesquiterpenoid lactone from Parthenium

Four sesquiterpene lactones were isolated from several populations of Parthenium confertum var. lyratum (Gray) collected in Sierra de Arteaga, southern Coahuila. Three of the compounds, hysterin, tetraneurin E and hymenin were previously isolated from other Parthenium species. The fourth constituent is the new cyclopropanoid sesquiterpene dilactone confertdiolide which represents a new structural type. The photolytic conversion of hymenin into confertdiolide confirmed its structure.     

Use of antibiotics to determine ribosome-messenger RNA interactions necessary for in vivo stability of specific messengers

With the use of inhibitors of individual reactions in protein synthesis, a method has been developed for (a) determining the role of ribosome messenger RNA interactions in specific bacteriophage T4 mRNA stability and (b) localizing the primary site of interaction of messenger ribonuclease (mRNase) on messengers. Antibiotics that freeze ribosomes in or near the initiation site stabilize T4 deoxynucleotide kinase mRNA. In contrast, T4 α-glucosyltransferase mRNA is stable only when the polysome configuration is kept intact. These results indicate the deoxynucleotide kinase mRNA initiation site is most susceptible to mRNase action, whereas the primary site of mRNase action on the α-glucosyltransferase mRNA is distal to the initiation site. Determining the role of ribosome-mRNA interactions in mRNA stability by the use of specific inhibitors of protein synthesis may be applicable to any procaryotic or eucaryotic mRNA that can be translated in vitro.     

Hyposmotic fluid formation in Hydra

A detailed model for hyposmotic fluid formation in Hydra is presented. We propose that enteron fluid formation occurs in two steps: (1) segregation of an isosmotic fluid in large intercellular vacuoles with (2) subsequent reabsorption of solute in the intercellular channels to form the hyposmotic fluid of the enteron. Intercellular spaces in Hydra have been studied by light microscopy and thin-section electron microscopy, as well as by electrophysiological methods. These spaces are of two types: (1) large vacuoles which are located in the cells of both the epidermis and gastrodermis, being more numerous in the epidermis; and (2) lateral intercellular channels which run from the intercellular vacuoles, leading eventually to the enteron. These vacuoles and channels are highly convoluted, forming a complex three-dimensional network. We suggest that this network is involved in the water balance of Hydra.     

Some Nutritional Characteristics of a Naturally Occurring Alga (Microcystis sp.) in a Guatemalan Lake

The nutritional characteristics of an alga (Microcystis sp.) that occurs naturally in a Guatemalan lake were determined. The sun-dried material proved to have a high protein content (55.6%) and to be a possible good source of calcium and phosphorus (1, 169.1 and 633.4 mg/100 mg, respectively). Amino acid analysis showed that total sulfur amino acids were the most deficient ones, giving a protein score of 42 to the material. The in vitro protein digestibility of the material was 69.5%. Biological trials demonstrated that when the material was offered as the only protein source, very low consumption and a high mortality rate were obtained whether or not the diet was supplemented with 0.4% dl-methionine. However, when the material supplied 25% of the total protein of a corn-algae diet, the protein quality of the cereal was significantly improved (P < 0.05).     

The pineal gland of the gerbil,Meriones unguiculatus

Summary By means of morphometric analytical procedures, a diurnal rhythm in the cellular volume of gerbil pinealocytes was determined. This rhythm has been attributed primarily to a change in the cytoplasmic volume of the pinealocytes which is low during the daylight hours and increases to reach a peak during the middle of the dark period. At the ultrastructural level, six cytoplasmic components of the pinealocytes were found to exhibit a rhythm: free cytoplasm, smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER) and ribosomes, secretory vesicles, microtubules, and mitochondria. The presumptive secretory vesicles and the microtubules reached a peak in volume one hour before lights-off. It is suggested that lights-on and lights-off both signal a decrease in size and/or number of the secretory vesicles. The SER and RER/ribosomes reached their peak volume one hour after lights-off which is interpreted as indicating a peak in indoleamine synthesis and protein synthesis, respectively. The volume of free cytoplasm exhibits two peaks; one occurs one hour before lights-off while the second peak occurs in the middle of the dark phase. It is suggested that, although part of the secretory product of the pinealocyte may be present in dense-cored vesicles, other locations could include the free cytoplasm and clear secretory vesicles.Supported by NSF grant #PCM 77-05734     

Cryptococcus neoformans varieties as agents of cryptococcosis in Brazil

The study of the clinical isolates of Cryptococcus neoformans from 83 Brazilian patients with disseminated cryptococcosis showed that 75 were C. neoformans var. neoformans and 8 were var. gattii. Twenty-seven isolates were serotyped; all 19 var. neoformans were serotype A and all 8 var. gattii were serotype B. The correlation of the varieties of C. neoformans with the presence or not of hosts predisposing conditions to the mycosis showed that: (1) cryptococcosis caused by gattii variety occurred in 7 (58.3%) of the 12 nonimmunosuppressed patients, and (2) cryptococcosis caused by neoformans variety occurred in 65 (98.5%) of the 66 AIDS patients and in all 5 patients with other immunosuppressive conditions. The comparison of the distribution of the gattii and neoformans varieties between the nonimmunosup-pressed and immunosuppressed patients showed a significant statistical difference (p < 0.01).