Auxin-induced H+-pump stimulation does not depend on the presence of epidermal cells in corn coleoptiles

Cell-wall acidification and electrical reactions (depolarization and hyperpolarization) are typical auxin responses in maize (Zea mays L.) coleoptiles. In an attempt to test the role of the outer epidermis in these responses, they have been measured and compared in intact and peeled coleoptile fragments. To exclude interactions between parenchymal and epidermal cells, the coleoptile pieces were completely stripped of their outer epidermis. This preparation was monitored by means of a scanning electron microscope. When externally applied indole-3-acetic acid was tested, we found that neither cell-wall acidification nor the electrical membrane responses depended on the presence of intact epidermal cells.Abbreviations IAA Indole-3-acetic acid - MES 2-[N morpholino-ethane-sulfonic acid - TRIS 2-Amino-2-hydroxymethyl-1,3-propanediol We thank Kuki Kaethner for her excellent technical assistance. This work was supported by the Hessische Graduiertenförderung and the Deutsche Forschungsgemeinschaft.     

Epidemiology of congenital heart disease in Louisiana: an association between race and sex and the prevalence of specific cardiac malformations.

We hypothesized that susceptibility to the genetic and environmental factors that disrupt cardiac development is associated with race and sex. To evaluate this hypothesis, we asked whether the prevalence of specific cardiac malformations differs by race and sex. We attempted to include all infants born alive in the State of Louisiana from January 1, 1988, through December 31, 1989, and diagnosed by echocardiography, catheterization and/or autopsy within a year of birth as having one of ten specific cardiac malformations. The prevalence of atrioventricular canal defects (AVCD) per 1,000 live births was significantly higher for black females (.744) compared to black males (.198) and for white females (.414) compared to white males (.116). Complete transposition of the great arteries (TGA) was significantly higher for white males (.559) compared to white females (.122); in contrast, TGA was not significantly different for black males (.198) and black females (.169). Obstructive left heart syndrome (OLHS)--aortic stenosis and/or coarctation of the aorta--was significantly higher for white males (.652) compared to white females (.317); in contrast, OLHS was not significantly different for black males (.264) and black females (.169). Single ventricle (SV) was significantly higher for whites (.202) compared to blacks (.067). We did not find that race and sex were associated with differences in the prevalence of tetralogy of Fallot and hypoplastic left heart syndrome. The numbers of infants with anomalous pulmonary venous return, tricuspid atresia, double outlet right ventricle, or truncus arteriosus were too small to measure an association with race and sex. These results demonstrate that the prevalence of a subset of cardiac malformations differs by race and sex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diel Nitrogen Fixation by Cyanobacterial Surface Blooms in Sanctuary Lake, Pennsylvania

Diel nitrogen fixation studies were conducted with assemblages of cyanobacteria sampled from surface blooms on Sanctuary Lake, Pa. The studies were conducted between July and September of 1982 to 1985 by using the acetylene reduction technique. Assemblages with the lowest cell concentrations (0.9 × 10⁹ to 1.0 × 10⁹ cells per liter) exhibited nitrogen fixation activity throughout the day, with maximum fixation rates occurring in mid to late afternoon; fixation proceeded throughout the night at rates equivalent to 23 to 28% of the afternoon maximum. In studies conducted with the highest cell concentrations (3.7 × 10⁹ to 6.7 × 10⁹ cells per liter), fixation rates reached maximum values in mid to late morning. The rates declined rapidly throughout the midday period and subsequently ceased from late afternoon until sunrise on the following day. The afternoon decline and cessation of fixation exhibited by high cell concentrations correlated with photosynthetically induced low total CO₂ and supersaturating O₂ concentrations. The midday decline could be prevented and partially reversed by experimentally lowering O₂ and increasing total CO₂ concentrations. Under experimental conditions which simultaneously prevented supersaturating O₂ concentrations and maintained high total CO₂ availability, nitrogen fixation continued throughout the solar day, with maximum rates occurring at midday. These observations indicate that temporal changes in photosynthetic activity may affect diel fluctuations in nitrogen fixation.     

The Sabinas syndrome

We have defined a new autosomal recessive disorder in patients stemming from a small community in northern Mexico. Diagnosable at birth, its major symptoms include brittle hair, mental retardation, and nail dysplasia. Structural hair abnormalities are seen by both light and electron microscopy. Hair cystine content is reduced while the copper/zinc ratio in hair is increased.     

Residual radiation injury exhibited in long-term bone marrow cultures

Residual radiation injury was demonstrated in long-term primary cultures of mouse bone marrow. Control cultures underwent three phases of hematopoietic activity as distinguished by initial establishment, steady high (plateau) production of granulocytes, and gradual decline. Irradiation with 50, 300, or 550 rads, given at the end of the initial phase, did not prevent any culture flasks from entering the plateau phase. However, actual production levels and the time they were maintained varied inversely with the radiation dose so that the accumulated postradiation cell production corresponded to an exponential dose-response relationship at any time after treatment. The accumulated cell productions were found to be similar in all groups when expressed by the number of stem cell doublings necessary to produce them. The findings cannot be explained by reproductive cell death and are consistent with the notion of a limited division capacity in hematopoietic stem cells.     

Local accumulation of membrane-associated calcium according to cell pattern formation inMicrasterias denticulata,visualized by chlorotetracycline fluorescence

Summary Developing cells ofMicrasterias denticulata Bréb. show a characteristic fluorescence of the plasma membrane (or cortical protoplasm) after treatment with chlorotetracycline (CTC), which is known to be an indicator for membrane-bound Ca²⁺. Depending on the stage of development the fluorescing sites of the young half cell are distributed in a specific pattern which corresponds to cell pattern formation. Therefore growth and thus cytomorphogenesis inMicrasterias seem to be mediated by a patterned accumulation of Ca²⁺ at the periphery of the differentiating cell. Participation of Ca²⁺ in a membrane-recognition process responsible for local vesicle incorporation is discussed.     

Patterned distribution of membrane-associated Ca2+ during pore formation inMicrasterias

Summary During the stage of pore formation developing cells ofMicrasterias denticulata show a patterned distribution of fluorescent dots on the plasma membrane after treatment with chlorotetracycline. The center-to-center spacing of these dots corresponds with the distances between the individual cell wall pores ofMicrasterias. Therefore it is supposed that the patterned distribution of pores and their formation which is mediated by special pore vesicles are related to local accumulations of membrane-associated Ca²⁺. Membrane-associated Ca²⁺ seems not only to be functional in tip growth but to be a general mediator for recognition and fusion processes between various vesicles and the plasma membrane.     

Rapid Cellular Regulation of D-Glucose Transport in Cultured Neural Cells

Previous studies have revealed two different kinds of regulation of glucose utilization in cell lines derived from the nervous system (Keller et al., 1981). We found glucose metabolism of C-6 glioma cells to be limited and regulated by membrane transport. In contrast, glucose utilization of C-1300 neuroblastoma (N2A) cells was limited by the known regulatory enzymes of the Embden-Meyerhof pathway. Under the given experimental conditions the "membrane-limited" C-6 glioma cells were characterized by periodically changing glucose transport rates and very low intracellular glucose concentrations, which remained constant in spite of widely differing transport rates. These findings suggest the close functional coupling between transport and phosphorylation required for the regulation of glucose transport by cellular metabolic needs.     

Unusual behaviour of SPO1 DNA with respect to restriction and modification enzymes recognizing the sequence 5''-G-G-C-C

Summary SPO1 DNA contains only 5 cleavage sites for restriction enzymes which recognize and cleave the sequence 5-G-G-C-C (HaeIII or BsuR). Fragments of SPO1 DNA cloned in E. coli to substitute 5-hydroxymethyluracil (HMU) by thymine (T) remain resistant to HaeIII indicating that this unexpectedly small number of cleavages by HaeIII is not correlated with the presence of HMU in the normal phage DNA. It was previously shown that SPO1 is neither subject to B. subtilis R restriction (Trautner et al., 1974) nor modification in vivo (Günthert et al., 1975). We now show that SPO1 DNA can however be restricted and modified in vitro.     

Application of pattern recognition and feature extraction techniques to volatile constituent metabolic profiles obtained by capillary gas chromatography

The applicability of threshold logic units, a form of nonparametric pattern recognition, to the processing of metabolic profile data obtained by high-efficiency glass capillary column gas chromatography has been investigated. The test data included profiles of the volatile constituents of urine from normal individuals and from individuals with diabetes mellitus. A feature extraction algorithm allowed for dimensionality reduction and indicated the constituents most important in the normal versus pathological distinction. With an optimum number of dimensions, a normal versus pathological prediction rate of 93.75% was achieved. Gas chromatography—mass spectrometry was utilized to identify important profile constituents.