Fractionation of the gene-size macronuclear chromatin fragments of the binucleated eukaryote Oxytricha

Summary The macronuclear chromatin of Oxytrichia nova consists of chromatin fragments which are fully soluble in 0.2 mM EDTA and whose DNA length varies from 500–25 000 bp. The DNA migrates electrophoretically as a series of discrete bands, with specific genes present in only one or a few bands. The chromatin fragments are composed of nucleosomes and migrate electrophoretically in proportion to their DNA length. These results suggest schemes for the fractionation of undigested chromatin in order to enrich for specific genes, facilitating analysis of changes in chromatin structure associated with changes in gene expression.     

Irrigation planning to transform subsistence agriculture: Lessons From El Salvador

Experience with irrigation schemes designed to improve the productivity of subsistence farmers in Latin America seems to parallel the results of the green revolution in Southeast Asia. Although in some cases the impact on the productivity has been significant, in far too many cases the pervasive pattern of inequity has been reinforced. This case study of the Irrigation District of Zapotitan in El Salvador analyses some of the reasons for the unexpected results, with particular reference to the planning process. It essentially illustrates that the transformation of subsistence agriculture through irrigation demands new institutions designed not only to service agricultural production but also to ensure the accrual of benefits on the targeted group.     

Five new filamentous,glucose-fermenting Candida isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Five novel representatives of the yeast genus Candida isolated from advanced stages of wood degradation from fallen trunks of Eucryphia cordifolia Cav., Laurelia sempervirens Weim., Laurelia philippiana Weim., Nothofagus dombeyii (Mirb.) Blume, and Nothofagus obliqua (Mirb.) Blume, in the evergreen rainy Valdivian forest of southern Chile, are described and illustrated. They clearly differ from all accepted Candida species to warrant their establishment as five new species of yeasts: Candida coipomensis sp. nov., Candida ralunensis sp. nov., Candida laureliae sp. nov., Candida osornensis sp. nov., and Candida llanquihuensis sp. nov.     

Seasonal fluctuations of the mineral concentration of alder (Alnus glutinosa (L.) Gaertn.) from the field

Summary The seasonal fluctuation of N, P, K, Ca, Mg, Fe, Mn, Mo, and Co, in leaves, roots and nodules of 40–50 year oldAlnus glutinosa trees growing at four different locations along the banks of the Tormes river, in the province of Salamanca, was studied. Also, the evolution of the soil organic matter under the trees sampled was evaluated. The data obtained for the various nutrient elements in the three plant parts are statistically treated at the significance levels of 99–95 per cent, and some remarks as to the nutritional status of the European alder in respect to the nutrients and its contribution to soil nutrient-cycling are provided. A positive correlation was found between N–P, N–K, N–Mg, and N–Mo, in leaves, and between N–P, N–K, N–Fe, N–Mn, and N–Mo in root nodules. In roots only, no significance at any level was obtained between N and any of the elements analyzed.     

Four new species of Apiotrichum isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Four unusual Apiotrichum, isolated from decayed wood of Eucryphia cordifolia Cav., Nothofagus obliqua (Mirb.) Blume, and Laurelia sempervirens Wein., one of which was also isolated from the intestinal tract of Scaptomyza multispinosa Malloch (Diptera), are described and illustrated. These species differ from all the accepted Apiotrichum species (1–3) to warrant their establishment as four new species: Apiotrichum eucryphiae, Apiotrichum osvaldii, Apiotrichum futronensis and Apiotrichum nothofagi.     

Two new species and one variety of nitrate-utilizing mycelial Candida isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Two unusual species of Candida and one variety of one of them, isolated from decayed wood (palo podrido) (12) in the ultimate stages of degradation, are described and illustrated. They differ sufficiently from all accepted Candida species to warrant their establishment as two new species and one variety: Candida railenensis, Candida bertae, and Candida bertae var. chiloensis.The DNA base composition of these yeasts was not calculated, since our laboratory is not properly equipped for that purpose.     

Application of immunoprecipitation techniques to the diagnosis of cutaneous and extracutaneous forms of sporotrichosis

Sporotrichosis is a mycosis which in our country has been described as only producing cutaneous and subcutaneous infections; in other countries it has been reported as causing pulmonary, bone, joint and meningeal infections.Possibly the systemic form also occurs in Venezuela since, along with the causative agent, all other factors considered as predisposing to systemic infection exist here.Through immunodiffusion (ID) and immunoelectrophoresis (IEP) and using a filamentous form metabolic antigen from Sporothrix schenckii, we were able to demonstrate precipitating antibodies against this fungus both in patients with cutaneous sporotrichosis, diagnosed by culture of the infecting agent, and in patients with pulmonary lesions. The IEP test showed the presence of an anodic arc which we have called the S arc, which could be one of the specific antigens of S. schenckii.

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Resumen En Venezuela, el diagnóstico de la esporotricosis solo se plantea ante lesiones cutáneas y subcutáneas, sin embargo, no deja de llamar la atención que siendo esta micosis la más frecuente en nuestro medio y existiendo concomitantemente en la población todos los factores predisponentes para que el S. schenckii invada órganos internos, estas localizaciones no han sido descritas.La incorporación del antígeno del S. schenckii para detectar anticuerpos circulantes en la ID en nuestros estudios serológicos de rutina, nos permitió observar la presencia de bandas de precipitación contra este antígeno en sueros de pacientes con lesiones pulmonares, igualmente fueron detectados anticuerpos en pacientes con esporotricosis cutáneas diagnosticadas por cultivo.El estudio de la estructura antigénica de este hongo, puso de manifiesto la presencia de un arco de localización anódica, que podría ser producido por uno de los antígenos específicos de este hongo; este arco que denominamos S fue visualizado en todos los casos positivos de esporotricosis cutáneas, al ser estudiados sus sueros en la IEF.Los estudios realizados en sueros de pacientes con lesiones pulmonares pusieron de manifiesto anticuerpos precipitantes en la ID e IEF, con las caractéristicas de evidenciar más de una línea de precipitación en la ID y un arco S más largo en la IEF, pudiendo ser esto originado por mayor producción de anticuerpos circulantes. Se plantea la necesidad de obtener el cultivo del S. schenckii de las posibles lesiones extracutáneas de esta micosis.

     

Inhibition of tumor growth in mice treated with synthetic muramyl dipeptide

Summary Treatment with synthetic MDP inhibited growth of transplantable, chemically induced tumors in syngeneic mice. The tumor-inhibitory effect was dependent on the schedule of MDP administration.Growth of SC transplants of a nonmetastasizing, MC-induced fibrosarcoma, MC11, was inhibited by local treatment with 200 g and 1,000 g MDP given SC 5–7 weeks before challenge. Treatment with lower (10 g and 100 g) doses of MDP and shorter (1–4 weeks) time intervals was not effective. Single doses of MDP (10–1,000 g) 1–3 weeks after challenge had no effect.Growth of IV-inoculated, metastasizing AAT-induced hepatoma A was inhibited by IV injections of 20 g MDP given 1 and 2 days prior to the challenge. Significant increases in the survival of hepatoma-bearing mice were observed only after injections of MDP incorporated in multilamellar liposomes.Abbreviations MDP n-acetylmuramyl-l-alanyl-d-isoglutamine - B10 C57BL/10ScSnPh mice - MC 3-methylcholanthrene - ATT o-amino-azotoluene - PBS phosphate-buffered saline     

Lethality and mutagenicity inHalobacterium mediterranei caused by N-methyl-N′-nitro-N-nitrosoguanidine

Compared withEscherichia coli, Halobacterium mediterranei was highly resistant to the lethal effect of N-methyl-N-nitro-N-nitrosoguanidine (nitrosoguanidine), but it was sensitive to the mutagenic action of this chemical agent. Nitrosoguanidine at 500 g ml^–1 gave a cell survival level between 1% and 10%, and this allowed us to obtain more Josamycin-resistant mutants compared with lower concentrations, which gave higher survival rates but fewer mutants. The efficiency of the mutagenicity obtained with the nitrosoguanidine treatment was examined under a variety of conditions. The optimal conditions for obtaining Josamycinresistant mutants were achieved by exposing, in darkness and without shaking, a suspension of about 10⁸ log-phase cells to 500 g nitrosoguanidine in 1 ml of 50 mM modified saline Tris-maleate buffer at pH 7.5, or in 1 ml of 5 mM modified saline Tris-citrate-maleate for 30 min at 37°C.     

Immunocytochemistry and ultrastructure of the neuropil located ventral to the rat supraoptic nucleus

Summary The neuropil located ventral to the SON was investigated by the use of immunoperoxidase staining for neurophysins, oxytocin and vasopressin, and electron miroscopy. The study was performed in six groups of rats: 1) control; 2) infusion of isotonic saline into the CSF; 3) infusion of hypertonic saline into the CSF; 4) drinking hypertonic saline for 4 days; 5) same as group 4 but injection of colchicine into the CSF on second day of dehydration; 6) salt loading for 3 months. In the control rats the ventral neuropil contained a few immunoreactive processes, the general morphology of which was completely different from that of the neurosecretory axons emerging from the SON at its dorsal aspect. In rats of groups 3 to 6 the ventral processes (VP) became loaded with neurosecretory granules, whereas the perikarya and axons were depleted. Based on their general morphology and reactivity pattern it is suggested that the VP are dendrites. Most of these dendrites were embedded in a glial cushion formed by the processes of a particular type of marginal glia. Some of these dendrites enveloped an arteriole penetrating the optic tract. All VP were rich in synaptic contacts. The possibility that the VP of neurosecretory cells may be functionally related to the subarachnoid CSF and the arteriolar blood flow is discussed.Supported by Grant RS-82-18 from Direccíon de Investigaciones, Universidad Austral de Chile