Crystal structure of neutral protease from Bacillus cereus refined at 3.0 A resolution and comparison with the homologous but more thermostable enzyme thermolysin

Neutral protease from Bacillus cereus exhibits a 73% amino acid sequence homology to thermolysin, for which an accurate crystal structure exists. The B. cereus enzyme is, however, markedly less thermostable. The neutral protease was crystallized and diffraction data to 3.0 A resolution were recorded by oscillation photography. The crystal structure was solved by molecular replacement methods using thermolysin as a trial molecule. The solution was improved by rigid-body refinement and model rebuilding into electron density omit-maps. The atomic co-ordinates were refined to R = 21.7% at 3.0 A resolution. Comparison of the resultant model with the thermolysin structure shows that the two enzymes are very similar with a root-mean-square deviation between equivalent C alpha-atoms of 0.88 A. The gamma-turn found in thermolysin is transformed into a beta-turn in the neutral protease by the insertion of a glycine residue. There appear to be no contributions to the enhanced thermostability of thermolysin from additional salt bridges, whereas contributions in the form of extra hydrogen bonding interactions could be important. Other factors that may affect thermostability include the two glycine to alanine exchanges and perturbations in the environment of the double calcium site.

Effect of fluoride containing dentifrice, mouthrinsing, and varnish on approximal dental caries in a 3-year clinical trial

The purpose of this study was to evaluate the separate effect of fluoride dentifrice, fluoride mouthrinsing and fluoride varnish on approximal dental caries. All 252 13-14-yr-old children at an elementary school were selected at random and divided among four groups for a 3-yr longitudinal study. Group 1 received a fluoride dentifrice for home care and a fluoride mouthrinse once a week. Group 2 received a fluoride dentifrice for home care and a placebo mouthrinse once a week. Group 3 received a fluoride dentifrice for home care and a fluoride varnish once every 3 months. Group 4 received a placebo dentifrice for home care and a fluoride rinse once a week. Fluoride rinsing did not give any additional effect compared with placebo-rinsing when a fluoride dentifrice was used for home care. Fluoride varnish gave a significant caries reduction compared with fluoride rinsing.

A 30-month longitudinal study of the effects of some oral hygiene measures on Streptococcus mutans and approximal dental caries

The effects of some oral hygiene measures on Streptococcus mutants and approximal dental caries were evaluated. One hundred and eighty-seven 13-year-old individuals with high levels of salivary S. mutans (greater than 10(6)/mL) were selected. They were randomly distributed into three groups. Group I initially received professional mechanical tooth-cleaning, tongue-scraping, chlorhexidine treatment, and oral hygiene instructions concentrated on the approximal surfaces most colonized by S. mutans. The treatment was given four times with intervals of two days, followed by one single treatment every six months throughout the experimental period. The initial treatment period for group II, also consisting of four visits, included the same oral hygiene instructions as for group I. The instructions were repeated every six months. Group III was maintained in the preventive program provided by the local Dental Health Office, based on mechanical plaque control and topical use of fluorides and chlorhexidine at individualized intervals. Group I showed a significant immediate reduction of S. mutans in saliva as well as an approximal tooth surfaces. After six months, there were no differences among the three groups regarding these variables. Compared with baseline, there was a significant reduction of S. mutans in all groups. There was no significant difference in caries progression among the three groups. However, the selected "high-risk" individuals in group I developed 0.25 new manifest caries lesions approximally/year, compared with 0.27 for all children of the same age group in the area. Seventeen individuals had approximal surfaces with consistently high or consistently low S. mutans levels. Forty-six percent of the surfaces with high values developed new or progressive caries, compared with 2% of the surfaces with low values.

A double-blind, multicenter immunotherapy trial in children, using a purified and standardized Cladosporium herbarum preparation. II. In vitro results

This double-blind immunotherapy trial in children, using a purified and standardized Cladosporium herbarum allergen preparation, has shown that children with mould asthma and/or rhinoconjunctivitis, responded to immunotherapy with a decrease in specific IgE and a significant increase in specific IgG. There was a marked increase in the ratio specific IgG/specific IgE as a result of active treatment. IgE-CRIE radiostaining patterns showed no pronounced changes after 10 months' active treatment and no "new sensitivities" could be detected in the studied patients. IgG-CRIE radiostaining, primarily directed towards the important allergens, was significantly increased in the active group and particularly towards Ag-12 (partially identical to a previously described major allergen in Cladosporium herbarum, Ag-54). Children treated with histamine placebo showed no change in antibody patterns during 10 months of treatment.

Crossed immunoelectrophoresis and crossed radioimmunoelectrophoresis analysis of "yellow jacket-common wasp" (Vespula spp.)

Crossed immunoelectrophoresis (CIE) pattern of Yellow jacket vespid venom showing 25 immunoprecipitates was used in crossed radioimmunoelectrophoresis (CRIE) analysis with sera from 35 subjects allergic to vespid venom. Phospholipase A and B, hyaluronidase, acid and alkaline phosphatases and a lytic active component were demonstrated in immunoprecipitates using zymography and direct haemolysis of sheep erythrocytes. CRIE analysis proved the allergenicity of these proteins. In addition, another antigen (Ag 17) with no detectable enzymatic or lytic activity was identified as an important allergen. This allergen is most likely identical to the previously described Antigen 5 in vespid venoms. By using CIE/CRIE the presence and complexity of multiple forms of the allergenic protein components were well demonstrated.

Changes in the organization of actin and myosin in non-muscle cells induced by N-ethylmaleimide

There is evidence from in vitro studies that the SH reagent N-ethylmaleimide (NEM) causes the formation of ATP-resistant rigor-complexes between actin and myosin, and NEM-modified heavy meromyosin has been used by Cande et al. to study the contractile process during cytokinesis. It is reported here that treatment of tissue-cultured cells with NEM causes an immediate cessation of all motile activities and a simultaneous stabilization of the ultrastructure of the cell visualized on lysis with detergent-containing buffers. After NEM treatment a 5- to 10-fold increase in the amount of myosin was found associated with the detergent-resistant cell residues. As suggested by immunoelectron microscopy, using antibodies to non-muscle myosin together with gold-labelled protein A, increasing amounts of myosin filaments became associated with the microfilament assemblies of the cell with time of NEM treatment. In addition to this there was a slow, progressive reorganization of the cortical wave of microfilaments. The structures interpreted as myosin filaments were visualized at relatively high resolution. The immunoelectron microscopy finally also indicated the presence of a non-filamentous form of myosin in agreement with the results of others.

The organization of microfilaments in spreading platelets: a comparison with fibroblasts and glial cells

Platelets respond to stimulatory agents in general by the formation of long spikelike surface projections built up of tightly bundled microfilaments. During contact stimulation this is followed by a second phase when thin membrane lamellae grow out between the projections. This behaviour resembles that seen for instance in fibroblasts and glial cells, sending out microspikes and lamellipodia as a step in their advancement over solid substrata. Conditions, designed earlier for the preservation and visualization of the fragile organization of microfilaments and microtubules in the peripheral, highly motile parts (leading lamellae) of such cells (Höglund et al. (1980) J. Musc. Res. Cell Motility, 1:127-146), were used here to produce high-resolution images of the ultrastructural organization of platelets spreading on a solid substratum. This revealed an unexpected arrangement of actin filaments running parallel to the advancing edge, and small tufts of microfilaments on the outside of this edge-bundle. Cytochalasin D caused a regression of the spikelike projections as well as of both types of structures in the advancing platelet lamella and led to the appearance of a dense filamentous mat in juxtaposition to the plasma membrane. Analysis of the actin pools using the DNAase inhibition assay showed that the dramatic reorganizations of actin seen during the two phases of contact stimulation was reflected in a shift in the G/F-actin ratio only during the early phase.

Clinical effects of preventive regimens for young people in their early and middle teens in relation to previous experience with dental prevention

The clinical effects of different preventive regimens provided for young people in their early and middle teens were studied during a 2-year period. The regimens studied during the 1st year of the trial were professional tooth-cleaning plus fluoride mouth-rinsing every 3rd week versus fluoride varnish treatment every 6 months. During the 2nd year, the preventive measures were given in accordance with the estimated needs of each individual. The results were related to the individuals' previous experience with dental prevention to determine whether this had a significant influence. The results showed that fairly good or excellent effects on the individuals' oral hygiene and gingival status were readily achieved and maintained with a professional tooth-cleaning plus fluoride mouth-rinsing regimen. The study failed to demonstrate any superior caries-preventive effect of the fluoride varnish treatments. Subsequent individualized prevention produced similar average end results in all groups. Differences in the results in accordance with the individuals' previous experience with dental prevention indicate a superior and prolonged influence on dental health of professional tooth-cleaning plus fluoride mouth-rinsing in comparison with a fluoride-based program alone.

Use of capillary isotachophoresis to measure the degree of chemical substitution of dog serum albumin

Analytical capillary isotachophoresis may provide a means for the rapid determination of the degree of substitution of proteins. Dog albumin conjugates with trinitrophenyl (TNP), fluorescein isothiocyanate (FITC) or monomethoxy polyethylene glycol (mPEG) have been studied as models for protein modification. An increase in the degree of covalent substitution of dog albumin with TNP, FITC or mPEG could be monitored rapidly using the UV signal or the conductivity signal as a measure of the increased protein zone width. These findings are encouraging with regard to the possible use of capillary isotachophoresis for screening the extent of protein modification.

X-ray diffraction analysis of matrix porin, an integral membrane protein from Escherichia coli outer membranes

An integral membrane protein forming channels across Escherichia coli outer membranes, porin, has been crystallized using a polyethylene glycol or salt-generated two-phase system. Monodispersity and homogeneity of protein-detergent complexes were found to be prerequisites for reproducible formation of crystals amenable to X-ray structural analysis. By varying pH, detergent and buffer type, large crystals of three different habits can be obtained, two of which are discussed in this paper. The tetragonal form (space group P4(2); unit cell dimensions, a = b = 155 A, c = 172 A) is suitable for X-ray analysis. Low temperature induces a change of the space group to P4(2)22, with a single trimer in the asymmetric unit. This crystal form diffracts to a resolution beyond 2.9 A. The hexagonal crystal form (space group P6(3)22; unit cell dimensions, a = b = 93 A, c = 220 A) is limited in resolution to 4.5 A, but reveals a packing arrangement very similar to that in two-dimensional membrane-like crystalline arrays.

Ultrastructural observations on endothelial cell vesicles after horseradish peroxidase microinjection into blood and dextran perfused microvessels of rat mesentery

Horseradish peroxidase (HRP) was injected for 5 sec into the arteriole that supplies the mesocecum in rats. This microperfusion was followed by fixation (with arrest of blood flow in 203 sec) either immediately or after an interval of 10 sec, 20 sec, 60 sec, or 120 sec and a diaminobenzidine cytochemical processing of the tissue was performed. The distribution of HRP was determined in the electron microscope. After immediate fixation HRP labelled 93% of luminal endothelial vesicles, 45% of cytoplasmic, closed vesicles and 4% of the abluminal ones but from 10 sec later virtually no labelling was seen. This finding seems best explained by a vesicular organization where most vesicles communicate with the extracellular space, directly or via other vesicles. However, a few observations of isolated labelled abluminal vesicles, even opposite endothelial cell nuclei already after 5 sec HRP exposure, indicate that classical vesicular transport in quanta also occurs. The same microvasculature was observed after 2 min artificial perfusion with 3% dextran 70 in Tyrode solution with or without 0.2% albumin followed by 5 sec HRP and fixation. In the absence of albumin HRP labelled vacuole-like vesicles and deep-penetrating clusters of vesicles in the endothelium. Moreover, isolated large vesicles and probably also vesicular conglomerates formed transendothelial channels. It is suggested that vesicular conformational changes might contribute to the permeability increasing effect of protein-free perfusion.

Crossed Immunoelectrophoresis analysis of bee venom. Enzymatic identification of antigens

Bee venom obtained by electrical stimulation has been analysed by crossed immunoelectrophoresis against high-titer rabbit antibodies. The antigenic analysis of bee venom revealed that the extract contained 17 antigens, which were detected in the crossed immunoelectrophoresis pattern after staining with Coomassie Brilliant Blue. The crossed immunoelectrophoresis pattern indicated heterogeneity in several of the antigens, as most of the precipitates (exhibiting enzyme and hemolytic activities) represented multiple forms of phospholipase A, hyaluronidase, acid phosphatase and melittin.

Use of isotachophoresis for identification of pollen allergens

A sensitive and practical method is described for identification of individual pollen allergens. Isotachophoretic patterns of allergen extracts suggest that it is possible to differentiate between various pollen allergens. Owing to the high sensitivity and short analysis time of isotachophoresis, new ways are made available for the analysis of allergen extracts and allergen raw materials.

On the ultrastructural organization of the microfilament system and the possible role of profilactin

This paper summarizes results of studies on human glia cells concerning the ultrastructural relationships in the microfilament system and the possible role of the profilactin complex. It presents electron micrographs of the leading lamella of cells grown on solid substratum, visualizing the organization of the microfilament system in this highly motile part of the cell at high resolution and at what appears to be a high level of preservation. These results are linked to observations made in our laboratory of the biochemical basis for the dramatic rearrangements occurring in platelets in response to thrombin stimulation. Taken together these results lead to a relatively detailed model for the mechanism of cell motility.

Visualization of the peripheral weave of microfilaments in glia cells

A peripheral weave of microfilaments is visualized in human glia cells. In this weave small numbers of microfilaments converge to structures in the cell edge. Similar assemblies of microfilaments seem to be attached to structures on the surface of microspikes. Together with filaments splaying from the paracrystalline arrangement in microspikes, these units make up the peripheral weave. The filaments of the weave come in close contact with each other and with filaments of internal actin fibres.

Use of an enzyme thermistor in continuous measurements and enzyme reactor control

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We decribe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containing immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.