Probing limits on spatial resolution using nonlinear optical effects and nonclassical light.

Using a simple optical setup to detect and characterize transmission gratings in the far field, we demonstrate that going beyond the diffraction limit is not possible using linear interaction of nonclassical illumination with the target grating. We also confirm that nonlinear optical interactions with the target grating, or with the optical medium around it, do allow improvement in resolution.

Inability of encapsulated Klebsiella pneumoniae to assemble functional type 1 fimbriae on their surface.

We screened phase variants of Klebsiella pneumoniae isolates for the expression of capsule and type 1 fimbriae and found that all of the 22 blood isolates were encapsulated and did not express type 1 fimbriae while 10 of 11 urinary tract isolates expressed type 1 fimbriae but were unencapsulated. Phase variants from selected isolates were found to be either unencapsulated and fimbriated or lacked both structures. Variants expressing both structures were not detected. Fimbrial subunits FimH and FimA were localized in the periplasmic space of the parent strain and on the surface of the unencapsulated variants. The results suggest that capsule formation impedes assembly of pre-formed fimbrial subunits on the bacterial surface.

Inhibiting interspecies coaggregation of plaque bacteria with a cranberry juice constituent [published erratam appear in J Am Dent Assoc 1999 Jan;130(1):36 and 1999 Mar;130(3):332].

Dental plaque stability depends on bacterial adhesion to acquired pellicle, and on interspecies adhesion (or coaggregation). A high-molecular-weight cranberry constituent at 0.6 to 2.5 milligrams per milliliter reversed the coaggregation of 49 (58 percent) of 84 coaggregating bacterial pairs tested. It acted preferentially on pairs in which one or both members are gram-negative anaerobes frequently involved in periodontal diseases. Thus, the anticoaggregating cranberry constituent has the potential for altering the subgingival microbiota, resulting in conservative control of gingival and periodontal diseases. However, the high dextrose and fructose content of the commercially available cranberry juice makes it unsuitable for oral hygiene use, and the beneficial effect of the high-molecular-weight constituent requires animal and clinical studies.

Electro-optical switches with plasma electrodes.

A transparent electrode concept using low-pressure ionized gas in the glow discharge regime is proposed for largeaperture electro-optic switch applications. A longitudinal Pockels cell and an electro-optically tuned second-harmonic-generation cell using KDP have successfully demonstrated the concept.

Demonstration of electro-optical switching at the 26 cm x 26 cm aperture using plasma electrodes.

We have constructed and tested a longitudinal Pockels cell with a clear aperture of 26 cm x 26 cm. Transparent plasma electrodes formed in a low-pressure glow discharge were used to apply a uniform electric field to a 1-cm thick KDP crystal. Optical switching times of 50 nsec were achieved with a bare KDP crystal. Significant improvement in switching time resulted from using a glass-plate-KDP-crystal sandwich.

An outbreak (?) caused by Escherichia coli O126:K71:H5 in premature infants.

The strain E. coli O126:K71:H5 was recovered during a 6 week period, from stool samples of 13 premature infants hospitalized in the Premature Infants Nursery Unit. Of a total of 147 tested stool samples, 69 were positive. This strain was also recovered for a long period from the respiratory tract of one of the infants. The strain had a low virulence for the infants. No clear relationship could be demonstrated between clinical status and recovery of the strain. The strain did not possess any of the well defined pathogenic mechanisms, namely enterotoxins LT and ST, and invasiveness. The production of a thermolabile substance toxic for Vero cells was demonstrated. The strain possessed both guinea pig mannose-sensitive and human mannose resistant hemagglutinins. In spite of the production of thermolabile toxic substance for Vero cells and in spite of its contagiousness and intestinal tract colonization capacity, the strain displayed the characteristics of an opportunistic pathogen rather than classic EPEC.

Photodamaged skin. Update on therapeutic management.

With baby boomers aging, the medical community is ushered into a new era of patient care, that of cosmetic maintenance and rejuvenation. The authors critically review pharmacologic treatments for preventing and treating photodamaged skin. Issues concerning sunscreens, tretinoin, silicone tissue augmentation, fat transplantation, collagen replacement therapy, and chemical exfoliation of the skin are addressed.

Infant mouse model of adherence and colonization of intestinal tissues by enterotoxigenic strains of Escherichia coli isolated from humans.

The ability of enterotoxigenic Escherichia coli H10407, which possesses colonization factor antigen I, to colonize the intestinal mucosa of infant mice was considerably better than that of its colonization factor antigen I-negative derivative H10407-P. The latter strain previously was shown to lack cell adhering ability in vitro and to have a diminished capacity to infect human volunteers as compared with the parent strain. D-Mannose blocked both colonization by an enterotoxigenic E. coli isolate (801) possessing both mannose-resistant and mannose-sensitive adhesins and the in vitro adherence of the strain to intestinal segments of infant mice. A derivative of another enterotoxigenic E. coli strain (lacking both mannose-sensitive and mannose-resistant adhesins obtained by in vivo passage showed a significant increase in colonizing ability in comparison with the parent strain. We conclude that the infant mouse model of infection of intestinal mucosa complemented by in vitro adherence assays with excised intestinal tissue is suitable for the study of the bacterial properties responsible for the various stages of intestinal colonization by human enterotoxigenic E. coli.

Sh. dysenteriae serotypes2,4,8-immunochemistry and phage receptor activity.

Among three analyzed serotypes of Shigella dysenteriae, namely, the serotypes 2,4 and 8, the serotype 2 proved to be a strong immunogen in rabbits, inducing anti-polysaccharide antibodies as well as antiprotein antibodies in all the animals. In contrast, the serotypes 4 and 8 were weak immunogens and among the rabbits some have synthesized only anti-proteins while others had antibodies against the somatic conjugate. Aside from the somatic antigens, large amounts of proteins were isolated from all the strains; however, the numerous determinants of these proteins were proven with the help of a serum to proteins from Sh. sonnei. The polysaccharides were specific for the serotype. The sensitivity of Sh. dysenteriae strains to phage P1 and the phage receptor actigity of different bacterial extracts were examined. By using the phage receptor neutralization test, it was possible to demonstrate that the receptor substance is a common component present in the lipopolysaccharide. The nature of neutralization has been discussed.

Antigenic, antibiotic and phage receptor activity of proteins from Sh. boydii 15.

The analyzed strain of Sh. boydii 15 induced antibodies against the somatic antigen conjugate, as in most Shigella. Except for the proteinic carrier of the somatic antigen, only a few of the homologous proteinic determinants induced corresponding antibodies; these were illustrated with the help of a serum to proteins from Sh. sonnei. The proteins of Sh. boydii 15 displayed a wide range of antibiotic activity against Shigella, E. coli and Salmonella. Another aspect concerning the biological activities of the proteins isolated from Sh. boydii 15 was its temperate phage receptor activity. This activity was found as well in the free proteins as in the proteinic moiety of the somatic antigen.

Receptors for T2, T4 and T6 phages in Sh. dysenteriae 7 and other serotypes of Sh. dysenteriae.

The sensitivity of four strains of Sh. dysenteriae and of nine strains representing other serotypes of Sh. dynsenteriae to phages T2, T4 and T6 was examined. Different extracts, prepared from sensitive strains were tested for their capacity of phage inactivation. We found that the receptor substance for phage T2 is localized differently in various strains: In Sh. dysenteriae 7, it was found in bacterial extracts obtained by water/phenol at 68 degrees C and in extracts obtained by trichloracetic acid; in Sh. dysenteriae 2 and Sh. dysenteriae 6, it was found in extracts obtained by heating in water at 65 degrees C. None of the tested extracts of strains Sh. dysenteriae 1, Sh. dysenteriae 4 and Sh. dysenteriae 9, sensitive to phage T2 and T6 and T6, revealed receptro activity for these phages. Most of the extracts, which showed receptor activity for phage T2, appeared to be weak or completely inactive for phage T6. Several strains appeared to be sensitive to phage T4 and the receptor active substance was found in the bacterial extracts obtained by water/phenol at 68 degrees C. The sensitivity of Sh. dysenteriae smooth strains to "rough specific" T4 phage is discussed.

Electro-optic harmonic conversion switch for large-aperture multipass laser systems.

We have demonstrated electro-optically tuned second-harmonic generation using Type I KDP inside a plasma-electrode discharge cell. An axial voltage of +/-52 kV is required to switch a 1.064-microm beam by conversion to 0.53/microm, in agreement with theory. Electro-optically tuned harmonic generation may be combined with a recently developed transparent plasma electrode to produce a large-aperture switch for multipass laser systems.