Cloning of the aspartate-β-semialdehyde dehydrogenase structural gene fromEscherichia coli K12

Transformation ofEscherichia coli strains with the recombinant plasmid, prepared by shot gun cloning with pBR322 and containing the geneasd, the structural gene of aspartate--semialdehyde dehydrogenase, results in an increase in specific activity of 65-fold of the enzyme in crude extracts. Approximately 60 mg of pure enzyme may be obtained from 10 g of transformed cells (wet weight) in a simplified purification procedure. The molecular weight, amino acid composition, and kinetic properties of the enzyme appear to be the same as previously reported, and the first 36 amino acids of the N-terminal sequence have been determined.     

Direct radioimmunoassay of estradiol-17β in defatted bovine milk

A radioimmunoassay was developed for rapid determination of estradiol-17β concentrations in unextracted defatted bovine milk. The assay was dependent on the use of a highly specific anti-estradiol-17β antiserum. Application of a formula to correct for the interference associated with individual milk samples and use of appropriate assay blanks facilitated interpolation on a buffer standard curve. The assay offered a high degree of sensitivity (0.6pg/ml milk) and a precision (within-assay coefficient of variation: 0.196; between-assay CV:0.191) comparable with contemporary extraction methods.     

Effect of Cerebellar Lesions on Monoamine Levels in Various Brain Areas of the Cat

Abstract: Modifications in the content of monoamines after different lesions of the cerebellar cortex were investigated in eight prosencephalic structures of cat's brain. Apart from other minor changes, lesions of the posterior vermis induced significant changes in the thalamus (decrease of DA and increase of 5-HT). Lesions of the cortex of a cerebellar hemisphere, on the other hand, produced an increase of 5-HT in the caudate nucleus and an increase of DA in the hippocampus in addition to a generalized increase of 5-HT in all the prosencephalic structures studied. These findings are discussed in relation to the anatomical connections of the lesioned areas and their expected role in the sleep-wakefulness cycle.     

Development of the ciliature of Tetrahymena thermophila: II. Spatial subdivision prior to cytokinesis

The cell surface of Tetrahymena thermophila is made up of an anterior region in which virtually all basal bodies of ciliary rows are ciliated, and the remainder in which ciliated and unciliated basal bodies are fairly irregularly interspersed. This pattern persists through interfission development until the stage of appearance of the equatorial ring of gaps in the ciliary rows that marks the fission zone. The ciliation pattern then becomes subdivided, in large part through the rapid ciliation of contiguous basal bodies located posterior to the fission zone. We interpret this process as a wave of ciliation of preexisting basal bodies that propagates posteriorly from the site of the fission zone. The location, extent, and timing of the ciliation process are the same in inverted as in normally oriented ciliary rows, in spite of the fact that in inverted rows the visible fission zone gap is tardily formed and the local configuration of ciliature around this gap is abnormal. The putative ciliation wave thus does not depend directly upon the local manifestations of the fission zone. However, in a cell-division-arrest mutant, cdaA1, analyzed under conditions in which formation of fission-zone gaps is permanently prevented in some ciliary rows but not in all, it is found that the ciliation pattern becomes subdivided in those ciliary rows that express fission-zone gaps and fails to become subdivided in neighboring rows that fail to manifest gaps. We interpret this combination of findings to indicate that a signal localized at the cell equator initiates a set of polarized developmental events that simultaneously create and demarcate two cellular fields within what was previously one. We further suggest that the characteristic tandem cell division pattern of ciliates is fundamentally a process of segmentation, which might involve mechanisms of gradient subdivision analogous to those taking place during segmentation of insects and other multicellular organisms.     

Cytochemistry and freeze-fracture of membranes isolated from the electrocyte of Electrophorus electricus (L.)

Summary Membranes were isolated from the main electric organ of Electrophorus electricus and studied by means of cytochemistry and freezefracture. The membrane fractions consisted of vesicles inside-in as determined by localization of anionic sites using colloidal iron and cationized ferritin particles. The anionic sites were not homogeneously distributed on the surface of the vesicle. Freeze-fracture showed the presence of intramembranous particles associated with either protoplasmic (P) or extracellular (E) faces of the membrane. Regions of the membrane without particles were observed. The results are discussed in relation to the existence of association between intramembranous particles and membrane receptors.For all correspondence     

On the fine structure of the electrocyte of Electrophorus electricus L.

Summary The general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiéry's method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.This work has been supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Conselho de Ensino para Graduados da UFRJ and Banco Nacional de Desenvolvimento Econômico, FUNTEC-241     

Microfilament bundles in antheridial nuclei of Achlya ambisexualis E 87

This is the first report of intranuclear microfilaments within gametangial nuclei of oömycetous fungi. Longitudinal sections of four to six microfilaments were frequently observed in meiotic antheridial nuclei of Achlya ambisexualis. Each microfilament measured approximately 7–10 nm in diameter. Spindle tubules (25 nm in diameter) were also observed within some of the nuclei possessing microfilaments.