The cytoskeletal architecture of interdigitated microvilli in the photoreceptors of some nocturnal spiders

Summary The photoreceptor microvilli of some nocturnal spiders (Isopeda andOlios in theSparassidae, andClubiona in theClubionidae) are wide (80–140 nm), and microvilli from adjacent receptors are interdigitated. Because microvillar diameters are relatively large in relation to the thicknesses of thin sections, it is possible to examine cytoskeletal structures closely associated with the microvillar plasmalemmae directly.Retinae were treated with a specific inhibitor of cysteine proteases before primary fixation for electron microscopy in a Ca²⁺-chelating medium. Cytoskeletal components were stabilized with tannic acid. A variety of microvillar profiles was obtained, consistent with an assumption that they represent imperfect preservation of anin vivo plasmalemmal undercoat, inferred to consist of longitudinally-disposed microfilaments, presumptively bonded to the microvillar plasmalemma. The microvillar lumen is inferred to be empty of cytoskeletal components in life.This model is discussed in terms of 1. the cytoskeletal organisation of microvilli of the primitive photoreceptors of a leech (Blest et al. 1983), where the arrangement of microfilaments resembles that in the vertebrate intestinal brush-border; 2. the large complement of membrane-associated oligomeric actin in rhabdoms of crayfish, where identifiable microfilaments cannot be resolved within microvilli by transmission electron microscopy (de Couet et al. 1984), and a single visualizable axial filament of uncertain composition is linked to the plasmalemma by side-arms.     

Secretory IgA and secretory component in women affected by recidivant vaginal candidiasis

Local immunity was evaluated in 47 patients affected by recidivant vaginal candidiasis and 33 control women. IgG, IgA, IgM and secretory component (SC) were determined by single radial immunodiffusion in samples of cervicovaginal secretion. IgG in dosable levels was detected in 17/47 samples (36.2%) and IgA in 15/47 patients (31.9%) whereas in the controls, the incidence was 31/33 (93.9%) for IgG and 24/33 (72.7%) for IgA. The difference was significative (P< 0.001) for both immunoglobulins. Significant differences were not obtained for IgM. The SC was detected in 4/47 cervicovaginal secretions of patients affected by candidiasis (8.5%) whereas in the control samples the incidence was 21/33 (63.6%) (P<0.001). In only 2/15 patients with dosable levels of IgA (13%) the secretory nature of this immunoglobulin could be shown by its reaction with anti-SC serum. In the control group, secretory IgA was detected in 19/24 cases (79%) (P< 0.001). Serum immunoglobulins levels were normal. The lack of secretory IgA and SC in the secretion could be related to the adherence capacity of the Candida albicans to epithelial cells.     

Occurrence of oscillations in ATP synthesis and hydrolysis in chromatophores of Rhodospirillum rubrum

The conditions under which an oscillatory behaviour is observed during net hydrolysis or synthesis of ATP in chromatophores of Rhodospirillum rubrum FR1 are described. In the case of ATPase the oscillations are observed at low temperature (ca. 11°C) in the dark after an initial transient behaviour. These oscillations are attenuated or disappear by the addition of an uncoupler.Oscillations are also observed during ATP synthesis. At 3°C the oscillations appear spontaneously if photophosphorylation is measured during a sufficiently long time. At 30°C the mere intercalation of a dark period also at 30°C is sufficient to trigger the oscillations in the following light period.Abbreviations Bchl Bacteriochlorophyll - FCCP carbonyl cyanide p-trifluoromethoxyphenyl hydrazone - PMS phenazine methosulfate - TMPD, N,N,N,N tetramethyl-1,4-phenylenediamine Dedicated to Prof. Dr. Gerhart Drews as a homage for his permanent example as hard worker and careful scientist and also for his remarkable human quality     

Immunoelectrophoretic approach to the metabolic regulation of glutamine synthetase in Rhodopseudomonas capsulata E1F1: role of glutamine

Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn²⁺-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS glutamine synthetase - MOPS 2-(N-morpholine) propane sulfonate - MSX l-methionine-d,l-sulfoximine     

Comparative study of selective media for enumeration of Pseudomonas aeruginosa from water by membrane filtration

In the present study, mPA-D and mPA-E agar, modifications of mPA-C agar that reduce background fecal streptococci that interfere with the differentiation and enumeration of the Pseudomonas aeruginosa colonies grown in other mPA media, are proposed for use in analyzing natural water samples. In addition, the efficiencies of several culture media for the recovery of P. aeruginosa in water after membrane filtration and multiple-tube techniques are compared. The degree of selectivity, precision, efficiency, and sensitivity achieved with the proposed media exceeded that achieved by current methods. Furthermore, they yielded equal rates of accuracy and specificity. Incubation at 36 degrees C resulted in an improved recovery of stressed P. aeruginosa. In conclusion, we propose the use of mPA-D and mPA-E agar, both incubated at 36 degrees C for 24 to 48 h, for analyzing river water and seawater, respectively.     

Regulatory interaction of photosynthetic nitrate utilization and carbon dioxide fixation in the cyanobacterium Anacystis nidulans

The rate of photosynthetic nitrate utilization in Anacystis nidulans is strongly influenced by the availability of carbon dioxide. This dependence can be relieved by inhibiting the metabolism of the ammonium derived from nitrate reduction. Nitrate uptake seems to be modulated through a sensitive regulatory system integrating the photosynthetic metabolism of carbon and nitrogen, with CO₂ fixation products antagonizing the inhibitory effect of ammonium derivatives.     

A comparison of the dose-response behavior of canine airways and parenchyma

We compared the histamine responsiveness of canine airways and parenchymal tissues in six anesthetized paralyzed open-chest mongrel dogs, partitioning total lung resistance (RL) into airway resistance (Raw) and tissue viscance (Vti). Pressure was measured during tidal breathing (frequency was 0.3 Hz) at the trachea and in three alveolar regions by use of alveolar capsules. Measurements were taken before and after the delivery of increasing concentrations of aerosolized histamine (0.1-30 mg/ml). We found that Vti accounted for 78 +/- 8% of RL under base-line conditions; this proportion remained relatively constant throughout the histamine concentration-response curve. There was a significant correlation between percent change in Vti and percent change in Raw at all levels of histamine-induced constriction (P less than 0.001). Moreover, the sensitivity of the tissues and airways (defined as the concentration of histamine required to double resistance) was remarkably similar. We conclude that, at this frequency of ventilation, Vti accounts for the major portion of RL both under base-line conditions and after histamine-induced constriction. Although increases in RL cannot be attributed solely to events occurring in the airways, the close correlation between changes in Raw and Vti and the similar sensitivities of the two support the use of indexes reflecting changes in airway caliber as an indicator of overall lung histamine responsiveness.     

Bacterial endotoxin and tumor necrosis factor stimulate prostaglandin production by human decidua

The purpose of these studies was to determine the effect of bacterial endotoxin and tumor necrosis factor (TNF) on prostaglandin (PG) secretion by human decidua. Decidual explants were established from women undergoing elective cesarean sections before the onset of labor. Escherichia Coli endotoxin and purified human recombinant TNF (rh TNF) were incubated with decidual explants. PGF2 alpha and PGE2 biosynthesis was measured by radioimmunoassay. A significant increase in the release of all PGs into the media occurred in response to LPS and TNF. In the setting of an extraamniotic infection, bacterial and host secretory products (TNF) could trigger the onset of labor, activating the decidua to produce PGs.     

Effects of pollen donors on seed formation inEspeletia schultzii (Compositae) populations at different altitudes

The influence of different pollen donors on seed formation was investigated in three populations ofEspeletia schultzii that differ in environmental conditions and life history characteristics. Self pollen and pollen from different donors (< 15m apart) within each population was used in a diallel design in order to test the genetic base of seed set variation. Three measures of seed formation were used: (1) achene number; (2) proportion of filled achenes (fruits) that distinguishes between achenes with seeds and empty achenes; (3) proportion of aborted seeds that distinguishes between viable and aborted seeds. Self-pollinations resulted in empty achenes. Achene number did not vary between the different pollen donors. A bimodal pattern of filled achenes was found in two populations in two consecutive years. On the other hand, a unimodal pattern was found in crosses between more distant donors (> 30m). These patterns seems to be the results of a sporophytic incompatibility system. Seed abortion was highest at the higher elevations and seems to be correlated with elevation rather than with any genetic effect.