Biosynthesis of Riboflavine in Corynebacterium Species: the Purine Precursor

Corynebacterium species lacks the ability to convert either xanthine or guanine to adenine. This defect and the use of the purine nucleoside antibiotic decoyinine, which blocks the conversion of xanthosine monophosphate --> guanosine monophosphate, permit an experimental design in which the interconversion of purines is largely prevented. Cultures of this organism were grown in the presence of decoyinine and various purine supplements. Data obtained by comparing the radioactivity incorporated from guanine-2-(14)C or xanthine-2-(14)C into bacterial guanine, xanthine, and riboflavine indicate that guanine or a close derivative of guanine is the purine precursor of riboflavine.     

Aspergilosis En Colombia

Resumen Se presentan 15 casos de aspergilosis recolectados en diferentes ciudades del país. Doce fueron casos autopsiados. Los tres restantes se refieren a pacientes en quienes se efectuó una lobectomía pulmonar superior derecha por aspergiloma gigante intracavitario. En los doce primeros existía una enfermedad básica que había alterado seriamente el estado general del paciente; once de ellos habían recibido antibióticos, cinco habían recibido esteroides, y dos, agentes citotóxicos. Se cree que, tanto el estado general del paciente, como la administración de dichas drogas, favorecieron la infección micótica. De los tres casos con aspergiloma intracavitario gigante, se cree que, en uno, la micosis se implantó en una caverna tuberculosa cicatrizada. En los otros dos, la cavidad era un bronquio localmente dilatado y se consideró que no existía una infección tuberculosa.ElAspergillus posee un amplio espectro de patogenicidad. Se le puede observar en lesiones que van desde una localización intrabronquial, acompañada de mínima o nula reacción inflamatoria, hasta casos en los cuales existen lesiones pulmonares necrotizantes con diseminación hematógena a otros órganos (sistema nervioso central, hígado, riñón).     

THE ETIOLOGY OF SCHIZOPHRENIA—A Review

The causes and the nature of the psychiatric disorder labeled schizophrenia remain vexingly obscure. Perhaps as an expression of a still extant body-mind controversy, most of the experiments and statements made toward an elucidation of the problem follow one or the other of two opposing postulations: (a) That its origin is genetico-organic; (b) that it is environmental. In a review of the outstanding “facts” for either argument, it is notable that they presuppose not only a difference in theoretical frameworks, but two radically distinct outlooks. This is reflected in therapy, a field in which organicists and environmentalists stand even further apart; the organicist, relying heavily on electroshock and drugs, hopes to counteract a hypothetical body malfunction, and the environmentalist, through psychotherapy, attempts to make it possible for the patient to disentangle his own conflicting feelings and reaction patterns.Between the two an eclectic position seems hardly tenable. For, in spite of voluminous research and speculation, it has not been possible to build a bridge between the two camps and integrate different outlooks which, at times, have brought psychiatry almost to the point of schism.     

Ultrastuctural and cytochemical study of spermatogenesis in Scrobicularia plana (Mollusca,Bivalvia)

The ultrastructure of the mature spermatozoa and spermatogenesis of the bivalve Scrobicularia plana are described. Support cells extend from the basal lamina to the lumen of the testis and are laterally connected to the germinal epithelium. Germ cells present intercellular bridges and flagella since the spermatogonial stage. While spermatogonia and spermatocytes appear connected to support cells by desmosome-like junctions, elongated spermatids are held at the acrosomal region by support cell finger-like processes. During spermiogenesis, the acrosomal vesicle differentiates from a golgian saccule and then migrates to the nuclear apex. A microtubular manchette arising from centrioles surrounds the acrosomal vesicle, the nucleus, and the mitochondria at the time these three organelles start their elongation, disappearing after that. The mature spermatozoon of S. plana lacks a distinct midpiece because the mitochondria extend from the region of the pericentriolar complex along the nucleus anteriorly for approximately 1.4 μm. The features of this bivalve type of modified spermatozoon are compared with those of other animal groups having similar modifications.     

SDSE: A software package to simulate the evolution of a pair of DNA sequences

An algorithm to simulate DNA sequence evolution under a generalstochastic model, including as particular cases all the previouslyused schemes of nucleotide substitution, is described. The simulationis carried out on finite, variable length, DNA sequences througha strict stochastic process, according to the particular substitutionrates imposed by each scheme. Five FORTRAN programs, runningon an IBM PC and compatibles, carry out all the tasks neededfor the simulation. They are menu driven and interfaced to thesystem through a principal menu. All sequence data files usedand generated by the SDSE package conform to the standard GenBankdatabase format, thus allowing the use of any sequence retrievedfrom this databank, as well as the application of other packagesto analyse, manipulate or retrieve simulated sequences. Received on August 23, 1988; accepted on November 15, 1988