Lineage-tracing hematopoietic stem cell origins in vivo to efficiently make human HLF+ HOXA+ hematopoietic progenitors from pluripotent stem cells

The developmental origin of blood-forming hematopoietic stem cells (HSCs) is a longstanding question. Here, our non-invasive genetic lineage tracing in mouse embryos pinpoints that artery endothelial cells generate HSCs. Arteries are transiently competent to generate HSCs for 2.5 days (∼E8.5-E11) but subsequently cease, delimiting a narrow time frame for HSC formation in vivo. Guided by the arterial origins of blood, we efficiently and rapidly differentiate human pluripotent stem cells (hPSCs) into posterior primitive streak, lateral mesoderm, artery endothelium, hemogenic endothelium, and >90% pure hematopoietic progenitors within 10 days. hPSC-derived hematopoietic progenitors generate T, B, NK, erythroid, and myeloid cells in vitro and, critically, express hallmark HSC transcription factors HLF and HOXA5-HOXA10, which were previously challenging to upregulate. We differentiated hPSCs into highly enriched HLF+ HOXA+ hematopoietic progenitors with near-stoichiometric efficiency by blocking formation of unwanted lineages at each differentiation step. hPSC-derived HLF+ HOXA+ hematopoietic progenitors could avail both basic research and cellular therapies.

UCHL1 is a potential molecular indicator and therapeutic target for neuroendocrine carcinomas

Neuroendocrine carcinomas, such as neuroendocrine prostate cancer and small-cell lung cancer, commonly have a poor prognosis and limited therapeutic options. We report that ubiquitin carboxy-terminal hydrolase L1 (UCHL1), a deubiquitinating enzyme, is elevated in tissues and plasma from patients with neuroendocrine carcinomas. Loss of UCHL1 decreases tumor growth and inhibits metastasis of these malignancies. UCHL1 maintains neuroendocrine differentiation and promotes cancer progression by regulating nucleoporin, POM121, and p53. UCHL1 binds, deubiquitinates, and stabilizes POM121 to regulate POM121-associated nuclear transport of E2F1 and c-MYC. Treatment with the UCHL1 inhibitor LDN-57444 slows tumor growth and metastasis across neuroendocrine carcinomas. The combination of UCHL1 inhibitors with cisplatin, the standard of care used for neuroendocrine carcinomas, significantly delays tumor growth in pre-clinical settings. Our study reveals mechanisms of UCHL1 function in regulating the progression of neuroendocrine carcinomas and identifies UCHL1 as a therapeutic target and potential molecular indicator for diagnosing and monitoring treatment responses in these malignancies.

Third international challenge to model the medium- to long-range transport of radioxenon to four Comprehensive Nuclear-Test-Ban Treaty monitoring stations

In 2015 and 2016, atmospheric transport modeling challenges were conducted in the context of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification, however, with a more limited scope with respect to emission inventories, simulation period and number of relevant samples (i.e., those above the Minimum Detectable Concentration (MDC)) involved. Therefore, a more comprehensive atmospheric transport modeling challenge was organized in 2019. Stack release data of Xe-133 were provided by the Institut National des Radioéléments/IRE (Belgium) and the Canadian Nuclear Laboratories/CNL (Canada) and accounted for in the simulations over a three (mandatory) or six (optional) months period. Best estimate emissions of additional facilities (radiopharmaceutical production and nuclear research facilities, commercial reactors or relevant research reactors) of the Northern Hemisphere were included as well. Model results were compared with observed atmospheric activity concentrations at four International Monitoring System (IMS) stations located in Europe and North America with overall considerable influence of IRE and/or CNL emissions for evaluation of the participants' runs. Participants were prompted to work with controlled and harmonized model set-ups to make runs more comparable, but also to increase diversity. It was found that using the stack emissions of IRE and CNL with daily resolution does not lead to better results than disaggregating annual emissions of these two facilities taken from the literature if an overall score for all stations covering all valid observed samples is considered. A moderate benefit of roughly 10% is visible in statistical scores for samples influenced by IRE and/or CNL to at least 50% and there can be considerable benefit for individual samples. Effects of transport errors, not properly characterized remaining emitters and long IMS sampling times (12-24 h) undoubtedly are in contrast to and reduce the benefit of high-quality IRE and CNL stack data. Complementary best estimates for remaining emitters push the scores up by 18% compared to just considering IRE and CNL emissions alone. Despite the efforts undertaken the full multi-model ensemble built is highly redundant. An ensemble based on a few arbitrary runs is sufficient to model the Xe-133 background at the stations investigated. The effective ensemble size is below five. An optimized ensemble at each station has on average slightly higher skill compared to the full ensemble. However, the improvement (maximum of 20% and minimum of 3% in RMSE) in skill is likely being too small for being exploited for an independent period.

Generating human artery and vein cells from pluripotent stem cells highlights the arterial tropism of Nipah and Hendra viruses

Stem cell research endeavors to generate specific subtypes of classically defined "cell types." Here, we generate >90% pure human artery or vein endothelial cells from pluripotent stem cells within 3-4 days. We specified artery cells by inhibiting vein-specifying signals and vice versa. These cells modeled viral infection of human vasculature by Nipah and Hendra viruses, which are extraordinarily deadly (∼57%-59% fatality rate) and require biosafety-level-4 containment. Generating pure populations of artery and vein cells highlighted that Nipah and Hendra viruses preferentially infected arteries; arteries expressed higher levels of their viral-entry receptor. Virally infected artery cells fused into syncytia containing up to 23 nuclei, which rapidly died. Despite infecting arteries and occupying ∼6%-17% of their transcriptome, Nipah and Hendra largely eluded innate immune detection, minimally eliciting interferon signaling. We thus efficiently generate artery and vein cells, introduce stem-cell-based toolkits for biosafety-level-4 virology, and explore the arterial tropism and cellular effects of Nipah and Hendra viruses.

Dach1 Extends Artery Networks and Protects Against Cardiac Injury

[Figure: see text].

A functional genomics screen identifying blood cell development genes in Drosophila by undergraduates participating in a course-based research experience

Undergraduate students participating in the UCLA Undergraduate Research Consortium for Functional Genomics (URCFG) have conducted a two-phased screen using RNA interference (RNAi) in combination with fluorescent reporter proteins to identify genes important for hematopoiesis in Drosophila. This screen disrupted the function of approximately 3500 genes and identified 137 candidate genes for which loss of function leads to observable changes in the hematopoietic development. Targeting RNAi to maturing, progenitor, and regulatory cell types identified key subsets that either limit or promote blood cell maturation. Bioinformatic analysis reveals gene enrichment in several previously uncharacterized areas, including RNA processing and export and vesicular trafficking. Lastly, the participation of students in this course-based undergraduate research experience (CURE) correlated with increased learning gains across several areas, as well as increased STEM retention, indicating that authentic, student-driven research in the form of a CURE represents an impactful and enriching pedagogical approach.

Isolation and expression analysis of cadmium-induced genes from Cd/Mn hyperaccumulator Phytolacca americana in response to high Cd exposure

Phytolacca americana is recognised as a hyperaccumulator that accumulates cadmium (Cd) and manganese (Mn). Although most studies have provided abundant physiological evidence, little is known about the molecular mechanisms of Cd accumulation in P. americana. In this study, Cd-induced genes were isolated using suppression subtractive hybridisation (SSH) library construction, and gene expression patterns under Cd stress were quantified using real-time quantitative PCR. The functions of PaGST, PaMT and PaFe-SOD were confirmed in transformant yeast. Reactive oxygen species (ROS) formation and cell death in root tips were detected, and SOD and POD activities in leaf tissue were also analysed. There were about 447 expressed sequence tags (ESTs) identified and confirmed. GO analysis showed those genes were mainly involved in metabolism, cell stress and defence, transcription and translation, signal transduction, transport, energy and ion transport, which formed the basis for a molecular understanding of P. americana Cd tolerance mechanisms. Cd also stimulated ROS formation and modified the antioxidant systems. Taken together, our results indicate that ROS formation and Cd-induced gene expression favour P. americana tolerance by activating the defence system and permitting subsequent adaptation to Cd toxicity.

Detection and analysis of fine particulate matter and microbial aerosol in chicken houses in Shandong Province, China

Bacteria and fungi are primary constituents of airborne microbes in fine particulate matter and harmful to health. To evaluate the environmental quality of different poultry houses in Shandong Province, China, the airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli were collected by the Andersen-6 air microorganism sampler. The fine particulate matter was collected by a ZR-3920 ambient air particulate matter sampler, and bacterial and fungal diversities and relative abundances analyzed using high-throughput sequencing. Results showed that the concentrations of airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli in poultry houses were 0.167 to 4.484 × 104 CFU/m3, 0.236 to 4.735 × 103 CFU/m3, and 0 to 33.0 CFU/m3, respectively. 11.4 to 34.3% of aerobic bacteria and 16.8 to 37.5% of fungi were distributed at levels 5 and 6 (0.6 to 2.1 μm, the particle sizes similar to fine particulate matter) in the Andersen sampler. The concentration of fine particulate matter in the poultry houses was 114 to 230 μg/m3, which was higher than the safety value 10 specified by WHO. In fine particulate matter, the main bacteria at phylum level were Firmicutes, Bacteroidetes, and Proteobacteria, whereas the dominant phylum of fungus was Ascomycota and Basidiomycota. Importantly, the relative abundances of Escherichia and Corynebacterium in the broiler houses were greater than those in layer houses. However, the percentages of Aspergillus and Penicillium were 13.5 and 0.56%, with a relatively high level in the layer houses. Altogether, results revealed that the ambient air quality in the poultry houses sampled had a relatively high abundance of conditional pathogenic bacteria and concentration of fine particulate matter, which could threaten the health of animals and workers in those environments.

Development of 2-Deoxy-2-[(18)F]fluororibose for Positron Emission Tomography Imaging Liver Function in Vivo

Life-threatening acute liver failure can be triggered by a variety of factors, including common drugs such as acetaminophen. Positron emission tomography (PET) is rarely used to monitor liver function, in part because of a lack of specific imaging agents for liver function. Here we report a new PET probe, 2-deoxy-2-[(18)F]fluororibose ([(18)F]-2-DFR), for use in imaging liver function. [(18)F]-2-DFR was synthesized and validated as a competitive substrate for the ribose salvage pathway. [(18)F]-2-DFR was prepared through an efficient late stage radiofluorination. The desired selectivity of fluorination was achieved using an unorthodox protecting group on the precursor, which could withstand harsh SN2 reaction conditions with no side reactions. [(18)F]-2-DFR accumulated preferentially in the liver and was metabolized by the same enzymes as ribose. [(18)F]-2-DFR could distinguish between healthy liver and liver damaged by acetaminophen. [(18)F]-2-DFR is expected to be a useful PET probe for imaging and quantifying liver functions in vivo, with likely significant clinical utility.

Effects of chromium picolinate on the viability of chick embryo fibroblast

Chromium picolinate (CrPic), which is used as a nutritional supplement and to treat type 2 diabetes, has gained much attention because of its cytotoxicity. This study evaluated the effects of CrPic on the viability of the chick embryo fibroblast (CEF) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, morphological detection, and flow cytometry. The results show that lower concentrations of CrPic (8 and 16 μM) did not damage CEF viability ( p > 0.05). However, higher CrPic concentrations (400 and 600 μM) indicated a highly significant effect on the production of intracellular reactive oxygen species, alteration of mitochondrial membrane potential, intracellular calcium ion concentration, and the apoptosis rate ( p < 0.01), contrary to lower CrPic concentrations (8 and 16 μM) and control group. Moreover, apoptotic morphological changes induced by these processes in CEF were confirmed using Hoechst 33258 staining. Cell death induced by higher concentrations of CrPic was caused by an apoptotic and a necrotic mechanism, whereas the main mechanism of oxidative stress-induced mitochondrial dysfunction was apoptotic death.

REP-PCR tracking of the origin and spread of airborne Staphylococcus aureus in and around chicken house

Staphylococcus aureus was used as an indicator to study the origin and spread of microbial aerosol in and around chicken houses. Air samples indoor, upwind (10 and 50 m), and downwind (10, 50, 100, 200, and 400 m) of four chicken houses were collected using Andersen-6 stages sampler. The concentrations of S. aureus were determined for every sample site. Isolation of S. aureus from chicken feces was performed according to the standard method. The genetic relationship among the isolates was determined by profiles of PCR-amplified repetitive extragenic palindromic (REP-PCR) elements. The results showed that the concentrations of S. aureus indoor of four chicken houses were higher than those upwind and downwind sites (P < 0.05 or P < 0.01), but there were no significant concentration differences among downwind sites (P > 0.05). The fingerprints and the phylogenetic tree indicated that a part of the S. aureus (55.6%, 10/18) isolates from indoor air had the same REP-PCR fingerprints as feces isolates. Consequently, most isolates (57.1%, 20/35) from downwind 10, 50, 100, 200, even 400 m had the same REP-PCR fingerprints as those from indoor or feces. These data indicated that some isolates from downwind and indoor originated from the chicken feces. However, those isolates from upwind had low similarity (similarity index 0.6-0.87) to those from indoor or feces. Therefore, the isolates upwind were not from the chicken feces or indoor. These results suggest that microbes in chicken feces can be aerosolized and spread indoor and outdoor, especially to downwind of the chicken houses. It should have an important epidemiological and public health significance.

PRACTICAL IMPLICATIONS

Thus, the use of S. aureus as an indicator to study the origin and spread of airborne pathogens from chicken houses is potentially useful for enhancing public health and understanding the airborne epidemiology of this pathogen. Meanwhile it can provide evidence for studying the spreading model of airborne pathogens.

Clostridium perfringens toxin types from freshwater fishes in one water reservoir of Shandong Province of China, determined by PCR

Four hundred and twenty intestinal content samples (not including intestinal tissues) of freshwater fishes (60 silver carps, 100 carps, 100 crucian carps, 60 catfishes and 100 zaieuws) caught from one water reservoir were examined bacteriologically for the occurrence of C. perfringens. Isolates were examined by polymerase chain reaction (PCR) for genes encoding the four lethal toxins (alpha, beta, epsilon and iota) for classification into toxin types and for genes encoding enterotoxin and the novel beta2 toxin for further subclassification. C. perfringens could be isolated in 75 intestinal contents samples (17.9%) from freshwater fish including: 13 silver carps, 2 carps, 12 crucian carps, 40 zaieuws, and 8 catfishes. In 75 isolates, 58 strains (77.3%) were C. perfringens toxin type C (alpha and beta toxin positive), 13 strains (17.3%) were toxin type A (alpha toxin positive) and 4 strains (5.3%) were toxin type B (alpha, beta and epsilon toxin positive). In addition, the gene encoding for beta2 toxin was found in 47 strains (62.7%) of all the isolates, seven from type A, two from type B, and 38 from type C. The gene encoding for enterotoxin was not found in any isolate. These amplified toxin gene fragment were cloned and sequenced and compared with reference strains, the identity varied from 98.15% to 99.29%. This is the first report of C. perfringens alpha, beta, epsilon, beta2 toxins in freshwater fish and of beta, epsilon toxins in fish in general, and is the first discovery that the beta2 toxin could be detected in strains of type B. The origin of this bacterium and its importance to human food poisoning in freshwater fish is discussed.

Isolation and characterization of Clostridium perfringens from apparently healthy animals of the Shandong province of China

In a pilot study the presence and frequency of Clostridium (C.) perfringens was investigated among apparently healthy farm animals in the Shandong province of China. 748 faecal samples were collected from 9 pig-, 4 sheep-, 7 cattle- and 5 rabbit farms. C. perfringens was isolated from 124 samples (16.6%). The isolates were classified into major toxin types by using PCR analysis detecting the genes encoding these toxins. All isolates were identified as C perfringens toxin type A. There are also some reports from different regions in China linking C. perfringens toxin type A strains to gastrointestinal diseases. Therefore further investigations about the epidemiologic role of C perfringens toxin type A strains in the Shandong region are necessary. Currently, cases of enterotoxemia from this region are investigated for the presence of C perfringens.

Symposium Report on Urothelial Dysfunction: Pathophysiology and Novel Therapies

PURPOSE

The basic premise of this symposium (Workshop 7) at the 2004 International Continence Society meeting in Paris was to elucidate different mechanisms of urothelial cell pathology, explore their impact on bladder function and discuss novel therapeutic interventions.

RESULTS

The topics included 1) urothelial structure and function, 2) the role of adenosine triphosphate in urothelial signaling and cystitis, 3) lamina propria myofibroblasts and purinergic receptors, 4) antiproliferative factor involvement in interstitial cystitis, 5) the urothelium as a reservoir for bacterial infections, 6) radiation cystitis, nitric oxide and gene therapy, and 7) intravesical treatments.

DISCUSSION

It was agreed that the urothelium can no longer be regarded merely as a passive barrier separating urine from the underlying tissues. The epithelial cells of the urothelium form part of an integrated network that also includes afferent and possibly efferent nerves, and suburothelial myofibroblasts. It has a central role in several functions, including bladder wall sensation, local blood flow modulation, pathogen removal and active barrier provision. These functions are achieved through several autocrine and paracrine pathways that involve transmitter release from the urothelium and its ability to integrate incoming signals through its battery of membrane receptors. Several pathological processes were discussed using this knowledge, including the role of small glycoproteins released during interstitial cystitis, the molecular basis of radiation induced urothelial damage, the origin of recurrent urinary tract infections and the mode of action of potential intravesical treatments for overactive bladder.

CONCLUSIONS

Overall it was concluded that the urothelium has a key role in regulating lower urinary tract physiology and pathology.

Sensitivity and specificity of antiproliferative factor, heparin-binding epidermal growth factor-like growth factor, and epidermal growth factor as urine markers for interstitial cystitis

We previously determined that the urine of interstitial cystitis (IC) patients specifically contains a factor (antiproliferative factor [APF]) that inhibits primary bladder epithelial cell proliferation, and that it has significantly decreased levels of heparin-binding epidermal growth factor-like growth factor (HB-EGF) and increased levels of epidermal growth factor (EGF) compared with urine from asymptomatic controls and patients with bacterial cystitis. We sought to confirm the specificity of these findings for IC using a larger patient population, including control patients with a variety of urogenital disorders. Clean catch urine specimens were collected from 219 symptomatic IC patients, 113 asymptomatic controls without bladder disease, and 211 patients with various urogenital diseases including acute bacterial cystitis, vulvovaginitis, chronic nonbacterial prostatitis, overactive bladder, hematuria, stress incontinence, neurogenic bladder, benign prostatic hyperplasia, bladder or pelvic pain without voiding symptoms, bladder cancer, prostate cancer, or miscellaneous diagnoses including anatomic disorders. APF activity was determined by (3)H-thymidine incorporation into primary normal adult human bladder epithelial cells. HB-EGF and EGF levels were determined by enzyme-linked immunosorbent assay. APF activity was present significantly more often in IC than control urine specimens (P <0.005 for IC vs any control group; sensitivity = 94%, specificity = 95%, P <10(-82) for IC vs all controls). HB-EGF levels were also significantly lower and EGF levels significantly higher in IC urine than in specimens from controls (P <10(-84) and P <10(-36), respectively). These findings confirm the utility of APF, HB-EGF, and EGF as markers for IC. Understanding the reasons for altered levels of these markers may lead to understanding the pathogenesis of this disorder.

Fabrication of conventional complete dentures for a left segmental mandibulectomy patient: a clinical report

Without preprosthetic reconstructive surgery, denture fabrication for mandibulectomy patients becomes extremely difficult. Implant-assisted overdentures may improve denture retention and stability, but some patients cannot afford this treatment. For the segmental mandibulectomy patient described in this report, properly fabricated conventional complete dentures provided comfort and sufficient function.

The pontic-splinted procedure for tooth and denture base additions in denture repair

Various methods for adding teeth to existing dentures have been used clinically. Although a direct, single-tooth addition method saves time, it often is difficult to achieve an esthetic appearance when adding several missing anterior teeth with this technique. Indirectly adding teeth may achieve a better esthetic result, but this method is time-consuming. This article describes the pontic-splinted procedure, an indirect method for replacing several anterior teeth and part of the denture base that can save time and, at the same time, help the clinician achieve acceptable esthetics.

Investigations on airborne microorganisms in animal stables. 2. Report: further characterization of airborne Clostridium perfringens

Toxovars of 97 airborne C. perfringens isolates and 10 C. perfringens isolates from fecal samples of a calf stable were determined by an EIA procedure. Most airborne and fecal isolates belonged to toxovar A (88.7% and 80.0% respectively). Eight point two% of airborne C. perfringens were identified as toxovar C and 3.1% as toxovar D. Toxovar B was not found in the airborne state. Twenty% of fecal C. perfringens belonged to toxovar D. Toxovar B and C was not isolated from fecal samples. In addition, all fecal and air-borne isolates of C. perfringens toxovar D strains were analyzed in SDS-PAGE for their polypeptide pattern. All isolates from both sources exhibited the same polypeptide pattern after electrophoretic analysis in SDS-PAGE. Both results, determination of toxovars as well as polypeptide pattern analysis in SDS-PAGE, suggest that a major source of airborne C. perfringens in animal stables is animal feces.

Mechanical properties of laser-welded cast titanium joints under different conditions

STATEMENT OF THE PROBLEM

Data on optimal conditions for laser welding commercial pure cast titanium used in dental restorations are sparse and not well established.

PURPOSE

The mechanical properties of laser-welded cast commercially pure titanium under different laser welding conditions were evaluated to find the optimal parameters in terms of duration and voltage (energy level).

MATERIAL AND METHODS

Fifty-seven cast pure titanium specimens according to ISO specification 6871 were divided into nine experimental groups and one control group. The sectioned titanium bars were laser-welded under different duration (8, 10, and 12 ms) and energy (290, 300, and 310 V) levels and evaluated for ranges of ultimate tensile strength (374 to 562 MPa), 0.2% yield strength (206 to 338 MPa), and percentage elongation (2.49% to 10.58%).

RESULTS

Under a suitable laser-welding setting parameter the ultimate tensile strength and 0.2% yield strength of experimental groups were weaker than the unsectioned control specimens (control group ultimate tensile strength 540 +/- 11 MPa, 0.2% yield strength 258 +/- 49 MPa) or too brittle (control group percentage elongation 12.41% +/- 1.83%). Two-way ANOVA, nonparametric tests showed that voltage was the only significant factor for all parameters studied (p < 0.01). Optimal conditions were determined with three-dimensional response curves (305 V, 12 ms ultimate tensile strength; 310 V, 10 ms 0.2% yield strength; 300 V, 12 ms percentage elongation).

CONCLUSION

Optimal duration and voltage (energy level) used in laser welding for cast CP grade I titanium bar was superior to or comparable with and produced properties that were superior to or comparable with the unsectioned control specimens.

High-performance liquid chromatographic determination of biogenic amines in fish implicated in food poisoning

A rapid, sensitive and reproducible high-performance liquid chromatographic procedure for the determination of nine biogenic amines in fish by improved benzoylation with benzoyl chloride was developed. The benzoylation of amines with benzoyl chloride at 30 degrees C for 40 min was the optimal condition to eliminate the influence of interfering peaks during analysis. The calibration curve for each amine was linear within the range of 0.02-4 microg. The amine recovery from fish meat was better by extraction with 6% trichloroacetic acid than with 1 M HClO4. The application of this method to detect amines in a fried marlin fillet implicated in a food poisoning incident indicated that a high level (84.1 mg/100 g) of histamine was present in the sample.

[Airborne microorganisms in animal stables. 1. Anaerobic airborne bacteria in a calf stable with special regard to Clostridium perfringens]

The total number of airborne anaerobic bacteria with special regard to Clostridium perfringens (C. perfringens) as well as the total number of airborne aerobic bacteria was estimated indoor and outdoor of a calf stable. 65 indoor samples and 63 outdoor samples were collected by using a 6 stage Andersen sampler. The total number of airborne anaerobic bacteria of the indoor samples ranged from 3,216 to 24,222 CFU/m3 (Colony Forming Units) with a part of 4 to 1179 CFU/m3 of C. perfringens. 734 to 1588 CFU/m3 of airborne anaerobic bacteria were found in the outdoor samples. The number of C. perfringens CFU varied between 2 and 15 CFU/m3. The total number of airborne aerobic bacteria indoor ranged from 9,166 to 53,932 CFU/m3, outdoor from 2,443 to 21,205 CFU/m3. Furthermore the results suggested that C. perfringens is suitable for indicating the bacterial contamination of air by faeces of animals.

Compliance and complications of clean intermittent catheterization in the spinal cord injured patient

The optimal management of the neuropathic bladder secondary to spinal cord injury remains unsettled. Some have advocated the use of chronic indwelling catheters in tetraplegic patients supposedly due to comparable complication rates with non-indwelling catheter management. We assessed the urological complication and compliance rates in a group of spinal cord injured patients followed over a mean of 5.9 years. Complication rates from clean intermittent catheterization were comparable if not better than the rates previously reported for clean intermittent catheterization and significantly better than chronically catheterized patients. The compliance rate in our series was 71% as determined by the number of patients remaining on clean intermittent catheterization at their last urological follow-up. We conclude that the use of clean intermittent catheterization can provide optimal management of the lower urinary tract in spinal cord injured patients.

Infection of human bone marrow stromal cells by hepatitis B virus: implications for viral persistence and the suppression of hematopoiesis

Suspension cultures of bone marrow cells (BMC) were challenged with hepatitis B virus (HBV) to study interactions between the virus and the nonadherent and adherent BMC populations. Virus-challenged BMC developed an adherent stromal layer that differed in cellular composition from that of mock-infected cultures, showing a threefold increase in cells of the monocyte-macrophage lineage with an accompanying decrease in cells of the granulocytic lineage. Both viral envelope hepatitis B surface and core antigen expression was detected in adherent and nonadherent cell populations up to 10 days after virus challenge, which decreased thereafter. HBV DNA was still detectable in adherent cells 3 weeks after virus challenge, as shown by polymerase chain reaction analysis. These data indicate that HBV can infect not only bone marrow colony-forming cells but also the stromal cell populations involved with the regulation of hematopoiesis in vivo. Such virus-cell interactions could contribute to the immune dysfunction and bone marrow failure occasionally reported for patients with HBV infection as well as acting as an important site for HBV latency and persistence.

Decreased permeation of cephalosporins through the outer membrane of Escherichia coli grown in salicylates

Escherichia coli K-12 cells grown in 1 to 5 mM sodium salicylate (SAL) or acetylsalicylate show increased phenotypic resistance to various antibiotics (J. L. Rosner, Proc. Natl. Acad. Sci. USA 82:8771-8774, 1985), including cephalosporins (this study). To determine whether these effects are caused by a decreased uptake of the antibiotics, the permeation of several cephalosporins through the outer membrane was measured. For E. coli K-12 grown in LB broth containing 5 mM SAL or acetylsalicylate, permeation of the outer membrane by the five cephalosporins tested decreased three- to fivefold compared with that in cells not grown in salicylates. Permeation of the outer membrane by cephaloridine decreased within 15 min of the addition of SAL to cells grown in broth and reached a minimum in 1 to 2 h. When cells were transferred from broth with SAL to broth without SAL, their permeability to cephaloridine increased slowly for the first 45 min and more rapidly over the next 1.5 h; the permeability then attained normal levels by 3 h. The permeability changes that occurred after media shifts, either to or from SAL, were prevented by concentrations of chloramphenicol that inhibited protein synthesis. These effects of SAL on outer membrane permeability are fully consistent with their effects on antibiotic resistance and with the report (T. Sawai, S. Hirano, and A. Yamaguchi, FEMS Microbiol. Lett. 40:233-237, 1987) that the outer membranes of SAL-treated cells are deficient in certain porins. Permeation of cephaloridine through the outer membrane also decreased when a virulent strain of E. coli K1 was grown in the presence of as little as 1 to 2 mM SAL. This raises the concern that high levels of salicylates in patients night interfere with cephalosporin or other antibiotic therapies.

Prolipoprotein modification and processing in Escherichia coli. A unique secondary structure in prolipoprotein signal sequence for the recognition by glyceryl transferase

An Escherichia coli mutant (lpp-14-1), with an alteration of glycine to aspartic acid at the 14th amino acid residue of the prolipoprotein signal sequence, has previously been shown to contain unmodified and unprocessed prolipoprotein in its cell envelope. Both the wild-type and the lpp-14-1 alleles of the lpp gene have been cloned onto a phage lambda vector. Two pseudorevertant alleles of lpp-14-1 (14R21 and 6a) have been isolated, cloned and sequenced. Amino acid sequences, deduced from the DNA sequences of the two revertant lipoprotein alleles, and biochemical characterization of the revertant lipoproteins, show that a conversion of the aspartic acid (residue 14) to asparagine completely restores the modification and processing of the 14R21 revertant prolipoprotein, while a change of the threonine-16 to isoleucine-16 partially enhances the modification and processing of the 6a prolipoprotein, which retains the aspartate-14 substitution. Secondary structure analysis of the revertant prolipoprotein signal sequences according to the Chou and Fasman rules revealed that the specific coil region in residues 14 and 15, and the beta-sheet structure in residues 16-18 of signal sequence may be important for prolipoprotein modification. These results suggest essential roles of both a unique secondary structure and hydrophobicity in residues 14-18 of prolipoprotein signal sequence for the proper recognition by the glyceryl transferase.

Colicin A receptor: role of two Escherichia coli outer membrane proteins (OmpF protein and btuB gene product) and lipopolysaccharide

ompF cells were completely resistant to colicin A, whereas btuB cells were partially resistant. The OmpF protein, in the presence of added lipopolysaccharide, inactivated colicin A. This inactivation was enhanced by added btuB gene product, btuB gene product with lipopolysaccharide did not inactivate colicin A. These data, together with the observation that vitamin B12 protected btuB+ cells from the killing effect of colicin A, suggest that the colicin A receptor in Escherichia coli K-12 is composed of the OmpF protein, the btuB gene product, and lipopolysaccharide.

Isolation and characterization of isogenic E. coli strains with alterations in the level of one or more major outer membrane proteins

Nearly isogenic Escherichia coli strains which carry mutations leading to altered levels of major outer membrane proteins have been prepared and genetically characterized.

Detection and incidence of specific species of spoilage bacteria on fish. II. Relative incidence of Pseudomonas putrefaciens and fluorescent pseudomonads on haddock fillets

Pseudomonas putrefaciens has been found to constitute one of the major species of spoilage bacteria on haddock fillets. The initial population of this organism on fillets of high bacterial quality is uniformly below 4% and most frequently no greater than 1%. During refrigerated storage, the organism increases at a more rapid rate than the total psychrophilic population, comprising 50 to 90% of the total population when the total count exceeds 10(6)/g of tissue. Fluorescent pseudomonads were shown to constitute a second group of predominant pseudomonads constituting up to 19.3% of the total population after 8 days of refrigerated storage. Of a total of 45 fluorescent pseudomonads isolated from haddock fillets, 14 (31.1%) were found to be potent fish spoilers. The use of a soft-agar-gelatin plating technique showed a parallel increase of proteolytic organisms with total count indicating that proteolytic organisms other than P. putrefaciens and fluorescent pseudomonads increase at a slower rate than these two groups.