Ultrastructure and cell wall composition in cell division cycle mutants of Schizosaccharomyces pombe deficient in septum formation

A number of temperature-sensitive cdc- mutants of Schizosaccharomyces pombe that are affected in septum formation were analyzed with respect to their ultrastructure and the composition of their cell wall polymers. One mutant strain, cdc 16-116, has a cell wall composition similar to the wild type (strain 972 h-). However two other mutants, cdc 4 and cdc 7, show a higher galactomannan content and a lower alpha-glucan content. In all the mutants tested, total glucose incorporation, protein, RNA and DNA synthesis increased similarly to wild type over 3 1/2 h. After 2-3 h of incubation at the non permissive temperature -35 degrees C-, cell numbers remained constant although, increases in optical densities at 600 nm were observed. According to scanning electron microscopy, the mutants had aberrant shapes after 5 h of incubation at 35 degrees C. Transmission electron microscopy showed that cdc 3 is unable to complete septum formation. cdc 4 showed the most varied morphological shapes and aberrant depositions of cell wall material. cdc 8 exhibited a deranged plasma membrane and cell wall regions near of cell poles; an abnormal septum and several nuclei. cdc 7 showed elongated cells with several nuclei and with an apparently normal cell wall completely lacking in septum and septal material. cdc 16 showed more than one septum per cell.

Inclusion of laboratory test results in the surveillance of infectious diseases

We studied certain indicators of the speed with which infectious diseases were notified and epidemiological case records carried out by public health workers for notifications with and without inclusion of laboratory test results. The notification records for brucellosis, dysentery, typhoid fever, viral hepatitis, meningococcal meningitis, and pulmonary tuberculosis in the province of Barcelona between 1982 and 1986 have been reviewed. For each disease notified the time lapse between the onset of symptoms and notification (Delay 1), between notification and implementation of the epidemiological investigation (Delay 2), and the sum of both time lapses (Delay 3) were calculated. In all diseases (with the exception of meningococcal meningitis) when significant differences in delays were noted, the longest were found in those notifications that included laboratory data in the epidemiological investigation. This means that the provision of laboratory data makes the process of notification slower (Delays 1, 2, and 3). Both notification when laboratory results are available and the inclusion of laboratory data in the epidemiological investigation, have a negative influence on the speed of the statutory notification process.

[AIDS: clinical and necropsy correlation. Analysis of 45 patients]

We have reviewed the autopsies performed on 45 AIDS patients who died in our hospital until June 1989, comparing the post-mortem diagnosis with those made while the patient was alive and in his last hospital admission. Bacterial pneumonia, CMV infection and atypical mycobacteria were the diseases most frequently unnoticed. On the contrary, HIV encephalitis and pulmonary mycosis were the disease with the greatest number of non confirmed clinical diagnosis. The routine performance of necropsy studies to AIDS patients permits to know the most prevalent infections in our environment and should improve the diagnostic precision.

[Nosocomial bacteremia caused by Serratia marcescens: analysis of 44 cases]

We have evaluated 44 cases of Serratia marcescens bacteremia (SB). Most took place in surgical services (57%) and the ICU (34%). In one occasion, the cases developed as an epidemic outbreak. SB basically developed in patients with underlying diseases (neoplasia in 32%, heart disease in 16%, chronic bronchitis in 14% and miscellaneous in 20%) in whom some invasive procedure had been carried out (98%). The most common complication was septic shock. In 17 cases the infection was polymicrobial. The most common serogroup was 0:5 (41%). 98% of strains were resistant to cephalothin, 78% to ampicillin and 29% to tobramycin. The mortality rate was 39% and the most common cause of death was septic shock. The factors which adversely influenced prognosis were as follows, in order of decreasing importance: leukocytosis, thrombopenia, associated gram-positive infection, age older than 65 years, "non-typable" serogroup, unknown portal of entry, epidemic case and septic shock.

[Prolonged course fever as presentation form of Crohn's disease]

3 cases of Crohn's disease whose first manifestation was fever preceding intestinal symptoms, 3, 12, and 36 months respectively, the intestinal symptoms, are presented. Apart from fever, one of our cases had multiple extraintestinal symptoms these being of pancreatic, hepatic, mucocutaneous, bone and ocular origin. We insist on the heterogeneous onset of the disease which forced the clinician to maintain this disease on the long list of prolonged febrile illnesses causes.

Environmental sensitivity and heterosis for egg laying in Drosophila melanogaster

Genotype × temperature interactions for egg laying were studied in Drosophila melanogaster using two sets of half diallel crosses: one between inbred lines of the same geographic origin, and the other between established laboratory, newly derived inbred lines from different geographic origins. The sensitivity of most genotypes to changes in temperature was adequately described as a linear regression of mean in temperature. The regression coefficients (linear sensitivities) were heterogeneous between genotypes. Hybrids were more affected by temperature variation than were inbreds. All the heterogeneity of linear sensitivities was accounted for by a linear function of the genotypic means, which strongly suggests that a scale effect is responsible for the differences in sensitivity to temperature. In contrast, no general relationship was found between standard error deviation (sensitivity to small environmental changes) and mean performance between genotypes, although hybrids tended to be less variable than inbreds. This shows that the sensitivity to environmental variation depends not only on the genotype, but also on the nature of the environmental variation. The variability within temperatures may be affected by the general homeostasis of individual genotypes, while the variability between temperatures could be the result of genes directly affecting the trait and their multiplicative interaction with the environment.

Kinetic properties of derepressible acid phosphatase from the yeast from of Yarrowia lipolytica

(1) An acid phosphatase from depressed cells of the yeast form of Yarrowia lipolytica has been characterized kinetically by studies on specificity, inhibition, rate equation forms and modelling of the enzyme mechanisms. (2) The study on specificity revealed that the acid phosphatase is a rather unspecific phosphohydrolase that has similar activity on several different phosphate esters. A very weak transphosphorylating activity was also detected. (3) Among the reversible inhibitors, phosphate and vanadate were outstanding, whereas EDTA behaved as an activator. (4) v vs. [S] studies with o-carboxyphenyl phosphate as substrate show that the acid phosphatase of Y. lipolytica exhibits non-Michaelian behaviour, a minimum degree of 2:2 being detected for the rate equation in [S]. (5) The inhibition by phosphate and vanadate seems to have the same pattern of partial inhibition with a certain non-competitive nature, 1:1 being the minimum degree of the rate equation detected in (I).

[The spectrum of lymphadenopathy in HIV-positive patients. Prospective analysis of 45 cases]

In the prospective analysis of 45 patients (intravenous drug addicts and homosexuals) with lymphadenopathy and positive HIV virus titers, including serology, immunological and histological lymph node studies, we examined the etiology and diagnostic results of the methods used. We found 19 cases with lymphoid follicular hyperplasia, 9 with lymph node tuberculosis, 7 with lymphoid depletion, 2 non-Hodgkin's lymphoma and one case with Hodgkin's disease. Routine serology did not provide more information concerning the lymphadenopathy and the immunological study showed a relationship, however not lineal, between the immunosuppression and the stage of HIV infection, while the histologic diagnosis did not, except in the cases with lymphoid depletion and non-Hodgkin's disease. In the asymptomatic patients (10 cases) biopsy results did not change the given treatment as well as the prognosis, thus, it could be eliminated in a routine study. Biopsy on occasions implied therapeutic management (lymph node tuberculosis) or a change in prognosis (lymphoma or lymphoid depletion) in symptomatic patients (35), therefore, it seems to de justified. Fine needle aspiration of the lymph nodes was harmless and safe and was shown to have good sensitivity (79%), thus, it can be recommended as a first elective diagnostic method for lymph node histology.

Analysis of lethals in selected lines of Drosophila melanogaster

Five lines of Drosophila melanogaster that reached an extreme phenotype after long-term selection for increased dorsocentral bristle number, were analysed for the presence of lethals. Seven chromosome II and three chromosome III lethal types were detected in four of the lines, at frequencies ranging from between 6% and 36%. No lethal had any demonstrable effect over the selected trait. In one line, where almost every chromosome II was a lethal carrier, it was shown that the main lethal (at a frequency of 36%) was associated with the transmission ratio distortion in males. The processes which could lead to the accumulation of this lethal and others linked in disequilibrium to it is discussed. Some results suggest similar mechanisms for the accumulation of lethals in the other lines. These findings show that causes other than the direct effect of artificial selection must be taken into account when trying to explain the accumulation of lethals in selected lines.

Dielectrophoretic behavior of yeast cells: effect of growth sources and cell wall and a comparison with fungal spores

Saccharomyces cerevisiae showed different dielectrophoretic behavior depending on the source of carbon for growth. Growth on fermentable carbon sources produced a dielectrophoretic response that decreased according to the amount of sugar present in the culture medium. Growth on nonfermentable carbon sources produced a constant dielectrophoretic yield, independent of the amount and source of carbon present in the medium. The dielectrophoretic yield, however, was independent of the nitrogen source. The yield spectrum for S. cerevisiae protoplasts was similar to that for the cells, although a decrease in the absolute value was observed. This decrease could be explained by the reduction in cell size and by assuming that the cell wall contributes a negative net charge to the yield. Fungal spores responded to the nonuniform electric field in the same range of frequencies as assayed for yeast cells.

Dielectrophoretic properties of yeast cells dividing by budding and by transversal fission

The dielectrophoretic behaviour of yeast cells dividing by budding or by transversal fission was analyzed. The results obtained show that the dielectrophoretic yield is a linear function of alternating voltage, cell concentration and the square root of the time of collection in all the species assayed. Dependence of the rate of collection on the frequency of the voltage applied (between 0.2 and 5 MHz) was also found. This behaviour is similar in the three microorganisms studied. The scale factor correlating the frequency spectrum for Saccharomyces cerevisiae and Saccharomycopsis lipolytica is proportional to cell size. However, these results can not be extended to Schizosaccharomyces pombe. A relationship between the dielectrophoretic yield and the age of the culture and the consumption of glucose has been established for the three yeast strains. Dielectrophoresis also permits the differentiation between viable and non-viable cells.