Fluorescence banding in four species of Microtidae: an analysis of the evolutive changes of the constitutive heterochromatin

Three different fluorochrome and specific counterstain combination (DAPI/AMD, DA/DAPI and CMA/DA) treatments were applied to the chromosomes of four Microtidae (Rodentia) species. The results complete the data obtained in our previous paper (Burgos, M., Jiménez, R., & Dìaz de la Guardia, R., Genome 30:540–546, 1988) and prove that the changes in the constitutive heterochromatin in the evolution of the karyotypes of these species are not only due to gain or loss of heterochromatin, but are qualitative with respect to their nucleotide composition, repeated base pair organization or DNA-protein complex modification. These variations lead to the differential response to the fluorescence dye combinations used.     

Nitrogen-source-induced activation of neutral trehalase in Schizosaccharomyces pombe and Pachysolen tannophilus: role of cAMP as second messenger

Abstract Resting cells of the fission yeast Schizosaccharomyces pombe , suspended in buffer with glucose, responded to the addition of asparagine by increasing trehalase activity. This response was preceded by a peak in cAMP concentration. The addition of the nitrogen source to resting cells, devoid of the catalytic subunit of cAMP-dependent protein kinase, produced the transient increase in cAMP but did not promote any change in trehalase activity. In the budding yeast Pachysolen iannophilus , the activation of trehalase by nitrogen source was also accompanied by a sharp peak in cAMP. These results suggest that in the two yeasts cAMP acts as a second messenger in the transduction of the nitrogen-source-induced signal causing the activation of trehalase.     

The role of fine needle aspiration biopsy cytology in the evaluation of the clinically solitary thyroid nodule

The imputation that a clinically solitary nodule is a suspicious sign of carcinoma has been the cause of too many surgical procedures as well as the subject of much controversy. This study evaluated the effectiveness of fine needle aspiration (FNA) biopsy cytology in diagnosing the uninodular goiters in 286 patients who presented with clinically solitary nodules. The final diagnoses in these cases included carcinoma (4.7%), adenoma (6.3%), autonomous nodule (11.0%), colloid goiter (45.8%), colloid cyst (17.4%) and chronic thyroiditis (13.4%). The proportion of patients with cancer in this group was the same as in patients with multinodular and diffuse goiters. These findings call attention to (1) the fact that any thyroid disease may appear as a uninodular goiter and (2) the frequency with which lymphocytic thyroiditis was cytologically diagnosed, even in cases with negative antibody titers. The cytologic diagnosis of benign disease has contributed to a reduction in the number of unnecessary surgical procedures; only 24.1% of our patients with uninodular goiters underwent surgery.     

Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae

The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text.     

Waste water treatment using saline cultures of microalgae

Summary Survival of microorganisms (Escherichia coli has been used as an example) is affected by a combination of salinity and high pH induced by the active photosynthesis of marine microalgae (Aphanotece or Dunaliella sp.). This effect can be applied to create a more efficient wastewater treatment process using algal stabilization ponds.     

Comparative study of G- and C-banded chromosomes of five species of Microtidae

G-banded karyotypes were compared in the following species of Microtidae: Microtus nivalis; M. cabrerae; M. arvalis and Arvicola sapidus. Previous observations on A. sapidus and A. terrestris (Díaz de la Guardia & Pretel, Caryologia 32: 183–189, 1979) were also incorporated in this study. The results show that Robertsonian translocations and pericentric inversions are common mechanisms involved in the karyotypic evolution of this group. Interspecific differences in C-banding patterns were also analyzed. Using the karyograph method (Imai et al., Am. Nat. 121: 477–488, 1983), the evolutionary distances of the karyotypes were estimated, and an attempt was made to establish a presumptive phylogenetic tree.     

Large cation-selective pores from rat liver peroxisomal membranes incorporated to planar lipid bilayers

Summary Fusion of a highly purified fraction of rat liver peroxisomal membranes to planar lipid bilayers incorporates large, cation-selective voltage-dependent pores. TheP _K/P _Cl ratio of these pores, estimated in KCl gradients, is close to 4. The pores display several conductance states and spend most of the time open at voltages near 0 mV, closing at more positive and negative voltages. At voltages near 0 mV the most frequent open state has a conductance of 2.4 nS in 0.3m KCl. At voltages more positive and more negative than 10 mV the most frequent open state displays a conductance of 1.2 nS in 0.3m KCl. With these results pore diameters of 3 and 1.5 nm, respectively, can be estimated. We suggest that these pores might account for the unusually high permeability of peroxisomes to low molecular weight solutes. Fusion also incorporates a perfectly anion-selective, two-open states channel with conductances of 50 and 100 pS in 0.1m KCl.     

Sequential homologies between procarboxypeptidases A and B from porcine pancreas

Automated Edman degradation of monomeric procarboxypeptidases A and B from porcine pancreas shows that their N-terminal regions (from residue 1 to 34-37) present a high degree of sequential homology to each other as well as to other related procarboxypeptidases. Conformational predictions based on these sequences confirm their structural homology and indicate the probable existence of two beta-turns, one beta-chain and a long alpha-helix in them. On the other hand, tryptic peptide maps on a reverse-phase column indicate great sequential similarities (if not identity) between monomeric procarboxypeptidase A and the procarboxypeptidase A subunit isolated from its binary complex with proproteinase E.     

Effects of prolactin on progestin secretion by human granulosa cells in culture

Concentrations of human prolactin (hPrl) greater than or equal to 600 ng/ml produced inhibition of progestin production in cultures of granulosa cells pooled from follicles of women stimulated with clomiphene citrate-human chorionic gonadotropin (hCG). However, cells collected from follicles of human menopausal gonadotropin (HMG)-hCG-treated patients did not demonstrate a significant reduction in progestin secretion in response to hPrl. We conclude that high concentrations of hPrl can result in inhibition of steroidogenesis, but the expression of the inhibitory effects of Prl depends upon the hormonal treatments used to stimulate follicular growth.