WaveGate: a versatile tool for temporal shaping of synchrotron beams.

We present a full performance characterization of a solid state pulse picker for hard x-ray pulses at synchrotrons. The device is called WaveGate. Specifically, we quantify its efficiency (>30 %), timing capabilities (switching times between 100 ns and ms), on-off contrast (>104) and influence on the coherence properties of the incident x-ray beam. In addition, we discuss the implementation of the WaveGate in an optical pump - x-ray probe setup. Even if single pulse selection is performed by external detector gating, the WaveGate drastically increases the efficiency of a measurement. Finally, we introduce advanced timing schemes that can be realized by modulating the time structure of the synchrotron beam.

Impact on blood pressure and intestinal perfusion of dobutamine or dopamine in hypotensive preterm infants.

In a prospective study hemodynamic effects of dobutamine or dopamine (10 micrograms/kg/min) were investigated in 20 preterm infants who had protracted arterial hypotension refractory to volume therapy. Doppler ultrasonography of the superior mesenteric artery (SMA) was applied to verify intestinal perfusion and blood pressure was recorded in parallel. Mean arterial pressure (MAP) raised significantly in both groups (from 31.0 +/- 6.8 to 37.7 +/- 9.8 mm Hg during dobutamine and from 27.7 +/- 3.6 to 36.0 +/- 9.3 mm Hg during dopamine). Mean blood flow velocity increased from 25.8 +/- 13.5 to 31.5 +/- 16 cm/s with dobutamine and from 16.3 +/- 5.0 to 19.0 +/- 6.0 cm/s with dopamine (significant for dobutamine). Vascular resistance of SMA (indicated by resistance index; RI) decreased from 0.81 +/- 0.07 to 0.74 +/- 0.11 for dobutamine and from 0.89 +/- 0.06 to 0.79 +/- 0.07 for dopamine (significant for both groups). These data indicate that in the dose tested here both catecholamines are equally effective in raising MAP and lead to a significant increase of intestinal perfusion. Thus, a negative impact on mesenteric blood supply, predisposing to necrotizing enterocolitis, is not probable.

Bacteremia due to Rochalimaea henselae in a child: practical identification of isolates in the clinical laboratory.

Two closely related species of Rochalimaea, Rochalimaea quintana and Rochalimaea henselae, are nutritionally fastidious but can be cultivated on bacteriologic media from the blood of patients with diverse clinical presentations. We report a case of culture-proven R. henselae bacteremia in a child with persistent fever. Serologic evidence of infection by R. henselae was ascertained by testing sera at two intervals for immunoglobulin G or immunoglobulin M antibodies by enzyme immunoassay and immunoblot. The case isolate and a collection of other strains (R. henselae, R. quintana, and related organisms) were used to test commercial identification systems for their comparative utility in the identification of Rochalimaea spp. on a practical basis. Of six systems designed for testing of either fastidious or anaerobic isolates of bacteria, the MicroScan Rapid Anaerobe Panel was the only system that distinguished R. henselae from R. quintana. Four of five others gave reactions that were unique within their data bases but did not distinguish Rochalimaea isolates at the species level.

Comparative evaluation of selective and nonselective culture techniques for isolation of group A beta-hemolytic streptococci.

A new selective blood agar medium, Strep A Isolation Agar (SI) from Remel (Lenexa, KS), was compared with Becton Dickinson's Streptococcus Selective Agar (SA) (Becton Dickinson Microbiology Systems, Cockeysville, MD) and with a nonselective Columbia Blood Agar (CB) (Difco, Detroit, MI). Throat swabs from patients with acute pharyngitis were cultured with the use of a single swab to inoculate each of the three plates in a specific order, rotating in three-week cycles. Plates were examined (each medium by a different technologist) after 24 and 48 hours of incubation at 35 degrees C in 5% carbon dioxide, and beta-hemolytic streptococci were serogrouped with the use of coagglutination. The positivity rate was significantly greater for SI (25%) and SA (26%) than for CB (18%) (P less than 0.001). The respective rates of Group A streptococcal detection by SI, SA, and CB were 91%, 95%, and 67%, respectively. However, a feature associated with the use of SI or SA, in contrast to CB, was delayed identification of isolates by 24-48 hours because of small colony size, slower growth rate, and inability to serogroup colonies taken directly from primary culture plates. Recovery of non-Group A beta-hemolytic streptococci occurred with CB (12%) greater than SI (8%) greater than SA (6%). SI is superior to a nonselective medium, such as CB, and is equal to SA for recovery of Group A streptococci from throat cultures.

A newly recognized fastidious gram-negative pathogen as a cause of fever and bacteremia.

BACKGROUND: We identified a motile, curved, gram-negative bacillus as the cause of persistent fever and bacteremia in two patients with symptomatic human immunodeficiency virus infection. The same organism was subsequently recovered from a bone marrow-transplant recipient with septicemia and from two immunocompetent persons with week-long febrile illnesses. All the patients recovered after antimicrobial therapy. METHODS AND RESULTS: Primary cultures of blood processed by centrifugation after blood-cell lysis yielded adherent, white, iridescent, morphologically heterogeneous colonies in 5 to 15 days. Subcultures grew in four days on chocolate, charcoal-yeast extract, or blood agar. The organisms stained weakly with safranin and were not acid-fast. Fluorescent-antibody tests for legionella and francisella were negative. Biochemical reactivity was minimal and difficult to ascertain. Agar-dilution testing revealed in vitro susceptibility to most antimicrobial agents tested. The cellular fatty acid composition of the isolates was similar, resembling that of Rochalimaea quintana or brucella species, but not Helicobacter pylori or species of campylobacter or legionella. As resolved by gel electrophoresis, cell-membrane preparations of all isolates contained similar proteins, with patterns that differed from that of R. quintana. Patterns of digestion of DNA from all isolates by EcoRV restriction endonuclease were virtually identical and also differed from that of R. quintana. On immunodiffusion, serum from one convalescent patient produced a line of identity with sonicates of all five isolates. CONCLUSIONS: This pathogen may have been unidentified until now because of its slow growth, broad susceptibility to antimicrobial agents, and possible requirement of blood-cell lysis for recovery in culture. It should be sought as a cause of unexplained fever, especially in persons with defective cell-mediated immunity.

Comparison of sedimentation and flotation techniques for identification of Cryptosporidium sp. oocysts in a large outbreak of human diarrhea.

Cryptosporidiosis, previously seen mostly among immunocompromised patients, is now recognized among immunocompetent patients. During a large outbreak of cryptosporidiosis in two day-care centers, we compared two procedures for the demonstration of the organism in preserved stool specimens. Of 703 stool specimens tested by both techniques, Sheather sucrose flotation (SSF) identified 127 (18.1%) as positive for Cryptosporidium sp. oocysts. Ritchie Formalin-ethyl acetate sedimentation (F/EA) plus a modified cold Kinyoun acid-fast stain (MCK) of the sediment identified 129 (18.4%) as positive for Cryptosporidium sp. oocysts. The degree of agreement between the two tests was statistically highly significant (P less than 0.0001). A total of 161 (22.9%) were positive by one technique or the other; 95 (13.5%) were positive by both techniques. A total of 32 specimens were positive by SSF but negative by F/EA plus MCK, and 34 specimens were positive by F/EA plus MCK but negative by SSF. The discrepancies between the two techniques occurred in stool specimens that contained rare to a few oocysts. Other parasitic forms were found by both techniques. F/EA plus trichrome staining recovered 126 (17.9%) specimens with Giardia lamblia, whereas SSF recovered only 42 (6.0%) specimens with G. lamblia. No association (chi 2 = 0.02, P = 0.89) was observed between the presence of G. lamblia and Cryptosporidium sp. in these stool specimens. We concluded that F/EA plus MCK of the sediment was as effective in the concentration and identification of Cryptosporidium sp. oocysts as SSF. F/EA plus MCK may be advantageous as a single concentration method for general parasitology when Cryptosporidium sp. is also being sought.

Evaluation of a lysis direct plating method for pediatric blood cultures.

The Isolator 1.5 Microbial tube (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.) is a commercially available blood culture system for use in pediatrics. The methodology is based on blood lysis followed by direct plating of the sample on culture media to detect bacteria and fungi. Comparative recovery rates of pathogens from blood collected in this and a conventional broth system were similar. The Isolator detected 104 of 120 clinically significant isolates, whereas 106 of 120 isolates were detected by the broth system. The major advantage of the Isolator methodology was early detection of septicemia. Initial detection of gram-negative bacteria occurred an average of 14.2 h earlier by the Isolator system than by the conventional broth method. The Isolator also permitted quantitation of bacteremia and fungemia. Probable contaminants were recovered from 10.0% of the cultures processed by the Isolator, but steps which could be taken to minimize this problem were identified. The Isolator is a useful method for pediatric blood cultures.

Evaluation of the Phadebact CSF test for detection of the four most common causes of bacterial meningitis.

A five-center collaborative study was undertaken to determine the suitability of the Phadebact CSF test kit and the Phadebact group B Streptococcus reagent for routine use by clinical laboratories to detect antigens of common organisms causing bacterial meningitis. The kits employ staphylococcal protein A coagglutination to detect the antigens of Haemophilus influenzae types a, b, c, d, e, and f, Neisseria meningitidis groups A, B, C, Y, and W135, Streptococcus pneumoniae (83 serotypes), and group B Streptococcus. A total of 2,817 individual tests were performed on 577 cerebrospinal fluid specimens. The percent positive specimens detected by coagglutination was as follows: overall, 84%; H. influenzae, 97%; group B Streptococcus, 75%; S. pneumoniae, 71%; and N. meningitidis, 58%. Eighty-five of the specimens were also tested by counterimmunoelectrophoresis. Coagglutination was more sensitive than counterimmunoelectrophoresis because it detected 74% of the positive specimens, whereas counterimmunoelectrophoresis detected only 65%. No false-positive results were obtained with coagglutination. The Phadebact CSF test kit is recommended for routine use in screening cerebrospinal fluid samples for antigens of the common organisms causing bacterial meningitis along with the Gram stain and culture for delayed confirmation of the rapid results.

Polarity in mechanoreceptor cells of trigger hairs of Dionaea muscipula Ellis.

Both the apical and the basal cell poles of the sensory cells in trigger hairs of Dionaea muscipula are structured identically. A complex of concentrically arranged endoplasmic reticulum cisternae occupies each of the poles. One to four vacuoles are enclosed within the central cisterna and contain polyphenols (deposits of "tannin"). Structural polarity, whether symmetric or asymmetric, as well as the occurrence of abundant endoplasmic reticulum and numerous mitochondria are characteristics of the perception cells of most animals and plants.

Evaluation of Bactogen and Phadebact for detection of Haemophilus influenzae type b antigen in cerebrospinal fluid.

Latex agglutination and coagglutination tests are commercially available as Bactogen and the Phadebact Haemophilus Test, respectively. We evaluated both for the detection of Haemophilus influenzae type b in cerebrospinal fluids. Both tests were positive in all of 51 culture-positive cases of meningitis caused by H. influenzae. Both were more sensitive than counterimmunoelectrophoresis. Antigen was also detected by Bactogen in seven of seven additional cerebrospinal fluid specimens (compared with four of seven by Phadebact) after 1 to 15 days of antimicrobial therapy. The cerebrospinal fluid of infants with meningitis owing to other common causative agents did not react with Bactogen or Phadebact. However, the cerebrospinal fluid of one patient with overwhelming infection owing to Proteus mirabilis reacted positively with Bactogen. Cost analysis revealed that Phadebact was less expensive to perform than Bactogen.