Plasmodium cynomolgi: the hsp 70 gene.

The hsp 70 gene of Plasmodium cynomolgi was isolated and characterized. As expected the gene is highly similar to that of the hsp 70 gene of Plasmodium falciparum (98% at the protein level, 82% at the nucleotide level). Surprisingly, the hsp 70 gene appears to be present in a single copy in all the P. cynomolgi strains tested, a finding that has implications for the parasite's ability to undergo a heat shock response.     

Relationships among the Mexican races of maize

The present study was designed to advance the classification of the Mexican races of maize as part of the process of revising the Razas de Maíz en México by Wellhausen et al. The interrelationships among the races are examined by numerical taxonomy of morphological characters and the comparison of classifications with previous studies. Forty-nine Mexican races, represented by 148 collections, were grown in several locations and seasons in México from 1982 to 1984; 47 characters were measured directly. For the analysis using numerical taxonomy, characters with the ratio \(r = [\hat \sigma ^2 _r /(\hat \sigma ^2 _{re} + \hat \sigma ^2 _e )] \geqslant 3.0\) were chosen. Classifications of Mexican races indicate general agreement with the relationships found in previous studies which were based on conventional taxonomic methods and numerical taxonomy. In addition, poorly described races and new types may now be assigned to well defined groups.     

Preferential cytoplasmic location of FtsZ, a protein essential for Escherichia coli septation

An ftsZ thermonull mutant has been constructed in which the ftsZ gene has been deleted from the Escherichia coli chromosome while maintaining a wild-type copy of the gene in a thermosensitive plasmid. Under conditions in which the ftsZ⁺ allele is unable to be replicated at the same pace as the chromosome, the cells become non-viable and grow as filaments, indicating that, contrary to other reports, FtsZ performs a function essential for cell survival. Antibodies raised against FtsZ have been used to detect the cellular location of FtsZ and its contents per cell. Fractionation experiments indicate that most of the total FtsZ present in the cell stays in the cytoplasm.     

Biological characterization of Trypanosoma cruzi zymodemes: in vitro differentiation of epimastigotes and infectivity of culture metacyclic trypomastigotes to mice

Thirty-one Trypanosoma cruzi isolates from Chile, Peru, and Bolivia were studied in their capacity to differentiate in vitro from epimastigotes to metacyclic trypomastigotes on TAU-3AAG medium. Zymodeme 1 parasites displayed the best level of differentiation, which ranges from 60 to 90% depending on the isolate. Zymodeme 2 parasites exhibited highly heterogenous differentiation rates. This differentiation method permits the obtention of large amounts of metacyclic trypomastigotes from zymodeme 1 parasites. Metacyclic trypomastigotes obtained in vitro were infective to nude Balb/c hybrid mice. Zymodeme 1 parasites produced high parasitemias in this murine model; in contrast, zymodeme 2 parasites displayed lower parasitemias. Of a total of 27 T. cruzi isolates, 20 proved to be infective to mice, 12 gave enough parasites for further studies, and 8 of these were used for biological characterization. Results are compared with the infective clone Dm28 and Tulahuén strains maintained since 1954 in mice.     

Elimination and reconstitution of the requirement for hormone in promoting temperature-dependent transformation of cytosolic glucocorticoid receptors to the DNA-binding state

Cytosols contain a heat-stable, chelatable, anionic, molybdate-like factor that stabilizes glucocorticoid receptors in a heteromeric complex with hsp90 (refers to the 90-kDa heat shock protein) and inhibits their transformation to the DNA-binding state (Meshinchi, S., Grippo, J.F., Sanchez, E.R., Bresnick, E.H., and Pratt, W.B. (1988) J. Biol. Chem. 263, 16809-16817). In this work, we demonstrate that removal of this factor by passage of L cell cytosol through the metal-chelating resin Chelex-100 makes the glucocorticoid receptor unstable, thus markedly facilitating both its dissociation from hsp90 and its transformation to the DNA-binding state. In normal cytosol, both temperature-mediated dissociation of hsp90 and temperature-mediated receptor transformation are hormone-dependent events. In the Chelex-treated, metal-depleted cytosol, however, temperature-mediated dissociation of hsp90 and receptor transformation occur very rapidly in a manner that is no longer hormone-dependent. When boiled L cell cytosol is added to the metal-depleted receptor system, the hormone dependence of both temperature-mediated dissociation of receptor from hsp90 and receptor transformation to the DNA-binding state is reconstituted. Like boiled cytosol, molybdate stabilizes the receptor complex and inhibits its transformation in metal-depleted cytosol, but it does not reconstitute the hormone dependence of the system. These results support the proposal that an endogenous metal anion interacts with the glucocorticoid receptor to stabilize it in the heteromeric, inactive, non-DNA-binding state in cytosol and that binding of the hormone promotes conversion of the receptor to the DNA-binding state through an effect on this metal anion center.     

Incorporation of free fatty acids into acylthioesters and lipids of developing sunflower seeds

The synthesis of lipids from radioactive fatty acids in developing sunflower seeds has been examined. Lauric, palmitic, stearic and oleic acids were us     

Hypertrophic cardiomyopathy associated with left ventricular aneurysm and normal coronary arteries: Case study indicating genetic tendencies of cardiomyopathy

A 50-year-old man presented with hypertrophic obstructive cardiomyopathy (HOC) associated with a left ventricular aneurysm and normal coronary arteries. His history revealed no evidence of myocardial infarction or atypical angina. Physical examination disclosed HOC but did not suggest the presence of an aneurysm. Although the patient was treated medically, heart failure ensued, and he died suddenly while working his farm. Subsequent investigation of the patient's family revealed that three of his five children were also affected by cardiomyopathy, which was especially pronounced in the eldest, a 22-year-old man. The possible hemodynamic relationship between HOC and left ventricular aneurysm is discussed, along with probable indications. The role of left ventricular aneurysm is also presented in relation to the natural history of the disease.     

Selective enrichment of aromatic amino acid auxotrophs in Hansenula polymorpha.

Aromatic amino acid auxotrophs of the methanol-utilizing yeast Hansenula polymorpha were effectively selected by the use of nystatin and a medium that inhibits the growth of tyrosine auxotrophs. The procedure resulted in a frequency of aromatic auxotrophs of 2% of survivors and an enrichment of 20-fold. The new procedure also takes less time than traditional procedures. Of the auxotrophic mutants isolated, two-thirds required tyrosine and the remainder were tyrosine-phenylalanine double auxotrophs.