Photo-Induced Charge State Dynamics of the Neutral and Negatively Charged Silicon Vacancy Centers in Room-Temperature Diamond

The silicon vacancy (SiV) center in diamond is drawing much attention due to its optical and spin properties, attractive for quantum information processing and sensing. Comparatively little is known, however, about the dynamics governing SiV charge state interconversion mainly due to challenges associated with generating, stabilizing, and characterizing all possible charge states, particularly at room temperature. Here, multi-color confocal microscopy and density functional theory are used to examine photo-induced SiV recombination - from neutral, to single-, to double-negatively charged - over a broad spectral window in chemical-vapor-deposition (CVD) diamond under ambient conditions. For the SiV0 to SiV- transition, a linear growth of the photo-recombination rate with laser power at all observed wavelengths is found, a hallmark of single photon dynamics. Laser excitation of SiV- , on the other hand, yields only fractional recombination into SiV2- , a finding that is interpreted in terms of a photo-activated electron tunneling process from proximal nitrogen atoms.

Eosinophilic esophagitis: a 10-year experience in 381 children

BACKGROUND & AIMS

Eosinophilic esophagitis (EoE) is a disorder characterized by a severe, isolated eosinophilic infiltration of the esophagus unresponsive to aggressive acid blockade but responsive to the removal of dietary antigens. We present information relating to our 10-year experience in children diagnosed with EoE.

METHODS

We conducted a retrospective study between January 1, 1994, and January 1, 2004, to evaluate all patients diagnosed with EoE. Clinical symptoms, demographic data, endoscopic findings, and the results of various treatment regimens were collected and evaluated.

RESULTS

A total of 381 patients (66% male, age 9.1 +/- 3.1 years) were diagnosed with EoE: 312 presented with symptoms of gastroesophageal reflux; 69 presented with dysphagia. Endoscopically, 68% of patients had a visually abnormal esophagus; 32% had a normal-appearing esophagus despite a severe histologic esophageal eosinophilia. The average number of esophageal eosinophils (per 400 x high power field) proximally and distally were 23.3 +/- 10.5 and 38.7 +/- 13.3, respectively. Corticosteroids significantly improved clinical symptoms and esophageal histology; however, upon their withdrawal, the symptoms and esophageal eosinophilia recurred. Dietary restriction or complete dietary elimination using an amino acid-based formula significantly improved both the clinical symptoms and esophageal histology in 75 and 172 patients, respectively.

CONCLUSIONS

Medications such as corticosteroids are effective; however, upon withdrawal, EoE recurs. The removal of dietary antigens significantly improved clinical symptoms and esophageal histology in 98% of patients.

Regulation of tight junction resistance in T84 monolayers by elevation in intracellular Ca2+: a protein kinase C effect

Elevation in intracellular Ca2+ acting via protein kinase C (PKC) is shown to regulate tight junction resistance in T84 cells, a human colon cancer line and a model Cl- secretory epithelial cell. The Ca2+ ionophore A23187, which was used to increase the intracellular Ca2+ concentration, caused a decrease in tight junction resistance in a concentration- and time-dependent manner. Dual Na+/mannitol serosal-to-mucosal flux analysis performed across the T84 monolayers treated with 2 microM A23187 revealed that A23187 increased both fluxes and that in the presence of ionophore there was a linear relationship between the Na+ and mannitol fluxes with a slope of 56.4, indicating that the decrease in transepithelial resistance was due to a decrease in tight junction resistance. Whereas there was no effect of 0.1 microM A23187, 1 or 2 microM produced a 55% decrease in baseline resistance in 1 hr and 10 microM decreased resistance more than 80%. The A23187-induced decrease in tight junction resistance was partially reversible by washing 3 times with a Ringer's-HCO3 solution containing 1% BSA. The A23187 effect on resistance was dependent on intracellular Ca2+; loading the T84 cells with the intracellular Ca2+ chelator BAPTA significantly reduced the decrease in tight junction resistance caused by A23187. This intracellular Ca2+ effect was mediated by protein kinase C and not calmodulin. While the protein kinase C antagonist H-7 totally prevented the action of A23187 on tight junction resistance, the Ca2+/calmodulin inhibitor W13 did not have any effect. Sphingosine, another inhibitor of PKC, partially reduced the A23187-induced decline in tight junction resistance. The PKC agonist PMA mimicked the A23187 effect on resistance, although the effect was delayed up to 1 hr after exposure. In addition, however, PMA also caused an earlier increase in resistance, indicating it had an additional effect in addition to mimicking the effect of elevating Ca2+. The effects of a phospholipase inhibitor (mepacrine) and of inhibitors of arachidonic acid metabolism (indomethacin for the cyclooxygenase pathway, NDGA for the lipoxygenase pathway, and SKF 525A for the epoxygenase pathway) on the A23187 action were also examined. None of these agents altered the A23187-induced decrease in resistance. Monolayers exposed to 2 microM A23187 for 1 hr were stained with fluorescein conjugated phalloidin, revealing that neighboring cells did not part one from another and that A23187 did not have a detectable effect on distribution of F-actin in the perijunctional actomyosin ring. The results indicate that elevation in intracellular Ca2+ decreases tight junction resistance in the T84 monolayer, acting through protein kinase C by a mechanism which does not involve visible changes in the perijunctional actomyosin ring.

Autoregulatory circuits in myeloma. Tumor cell cytotoxicity mediated by soluble CD16

BACKGROUND

Multiple myeloma remains an incurable malignancy due to marked resistance of the tumor to standard doses of chemotherapy. Treatment approaches, using chemotherapeutic dose escalation and hematopoietic stem cell support have resulted in significant augmentation of tumor mass reduction such that complete remissions are effected in approximately 50% of patients. These remissions are however, often not durable. In the setting of minimal residual disease, therefore, adjunctive immunotherapy may be useful.

METHODS

Peripheral blood mononuclear cells were studied from 28 untreated patients with multiple myeloma (MM). Mononuclear cell CD16 (FcR gamma III) expression was determined by flow cytometry. The effect of lymphocyte-derived soluble CD16, isolated by affinity chromatography, on MM cell growth and differentiation was assessed. MM cell proliferation, viability, immunoglobulin production and gene expression was studied.

RESULTS

Data are presented indicating that cells expressing CD16 are increased in untreated patients with IgG-secreting myeloma. The predominant phenotype of these cells is CD8+ or CD56+. These CD16+ cells can produce a soluble form of the Fc receptor (sFcR, sCD16) that can bind to surface Ig on cultured human IgG-secreting myeloma cells and effect suppression of tumor cell growth and Ig secretion. This effector function is accompanied by concomitant suppression of c-myc as well as IgH and IgL gene transcription. Finally, prolonged exposure to sCD16 causes myeloma tumor cell cytolysis.

CONCLUSIONS

sCD16 and possibly other soluble FcR are candidate molecules for adjunctive immunotherapy of myeloma, once complete responses have been effected by intensive cytotoxic therapy, now possible in up to 50% of newly diagnosed patients.

An introductory orientation to clinical pathology core and on-call responsibilities

An introductory 4-week orientation for clinical pathology is described. There were 76 hours of lectures, 74 hours of conferences, and 68 hours of laboratories for a total of 221 hours. During the orientation, all calls handled by the residents were evaluated as to resolution, patient outcome, and interaction required. Eighty calls were received during the orientation from 57 technologists (71%), 16 physicians (20%), and seven nurses (9%). The calls originated concerning the following: blood banking, 37 (46%); hematology, 21 (27%); chemistry, 14 (18%); microbiology, five (6%); and administration, three (4%). Sixty percent of the calls were consultative and 40% were supervisory. Ninety-nine percent were handled appropriately by the residents. Patient outcome was moderately or significantly affected in 44% of all calls, divided between 67% of all consultative calls and 9% of all supervisory calls. Significant pathologist interaction was required in 49% of all calls, divided between 71% of the consultative calls and 16% of the supervisory calls. Using this integrated, dynamic system of resident instruction, on-call experience, and evaluation, residents quickly gain confidence in handling call, didactic clinical consultation, and patient management. The orientation and on-call system described provides for a relevant and dynamic system for resident education.

Case report: isoimmune inhibition of erythropoiesis following ABO-incompatible bone marrow transplantation

A 26-year-old ABO-O positive patient with aplastic anemia received a bone marrow transplant from his genotypically HLA identical, but ABO-A positive, brother. Engraftment of myeloid and megakaryocytic lineages occurred within 4 weeks but pure red cell aplasia and transfusion dependent anemia persisted for 160 days. The authors postulated that the failure of erythropoiesis was due to a high titer of anti-A isohemagglutinins. They tested this hypothesis with clonal cell cultures and flow cytometric analysis of ABO antigen expression by colony forming cells in vitro. During the period of prolonged red cell aplasia, the patient had normal numbers (85 +/- 12 per 10(6) cells) of circulating donor derived, burst forming units-erythroid (BFU-E). Immunophenotypic analysis of erythroid burst colonies derived from culture of the patient's bone marrow cells showed that 91 +/- 5% of 274 nucleated red cells were A-antigen positive, confirming full donor engraftment. Autologous plasma and complement added on day 1 of culture did not affect the colony growth (82.5 +/- 15 per 10(6) cells). However, when the addition of complement was delayed until day 7 of culture, there was 90% inhibition of BFU-E (7.5 +/- 5 per 10(6) cells) compared to controls (p less than 0.0004). Based on this, the authors propose a model for expression of ABO antigens during erythropoiesis, in which BFU-E do not express ABO antigens but their progeny do. The data support the hypothesis that the mechanism of prolonged pure red cell aplasia after ABO-incompatible bone marrow transplantation is complement mediated immune destruction of erythroid progenitors past the stage of BFU-E in differentiation.

Visualization of the ribosome-lamella complex in plastic-embedded biopsy specimens as an aid to diagnosis of hairy-cell leukemia

Hairy-cell leukemia is a lymphoid leukemia of B-cell lineage, the cells of which are characteristically tartrate resistant acid phosphatase positive on blood and bone marrow smears. However, because hairy-cell leukemia is frequently associated with abundant marrow stroma, dry marrow taps, and peripheral pancytopenia, the diagnosis may rest on the appearance of the bone marrow biopsy specimen alone. The ribosome-lamella complex has been associated with hairy-cell leukemia, and can be visualized by light microscopy using l-micron sections of plastic-embedded bone marrow specimens stained with toluidine blue. We describe the findings in a case in which bone marrow and liver biopsy specimens were positive for hairy cells containing ribosome-lamella complex, which were visualized with both electron microscopy and light microscopy. Reliable light microscopic identification of ribosome-lamella complex may provide an easy and inexpensive method of aiding in the diagnosis of hairy-cell leukemia when aspirate material is not available for tartrate-resistant acid phosphatase stain.

Galactose as a gratuitous inducer of GAL gene expression in yeasts growing on glucose

The promoters of the highly expressed and stringently regulated GAL genes of Saccharomyces cerevisiae, are useful for expressing proteins in this organism. However, two problems complicate their use. First, because growth on glucose causes prolonged repression of GAL expression, cells are most rapidly induced after growth on nonfermentable carbon sources, conditions which usually support poor growth. Second, because the inducer of the GAL genes (galactose) also serves as a carbon source, the level of inducer is continually diminishing during growth of a Gal+ strain, which may lead to reduced GAL expression. To solve the first problem, we have employed strains that carry the reg1-501 mutation, which eliminates glucose repression of GAL expression. This gene has been shown to be located on the right arm of chromosome IV, distal but tightly linked to the TRP1 gene. We demonstrate that expression from GAL promoters is efficiently and rapidly induced in these reg1 strains by the addition of galactose to a culture growing in glucose medium. Levels of galactose as low as 0.02% can be used to obtain a 1500-fold induction of gene expression from GAL promoters in this strain. To surmount the second problem, we have used a gal1 mutant, deficient in the enzyme that catalyzes the first step of galactose utilization. We show that high levels of expression from GAL promoters are achieved rapidly in these mutants, for which galactose is a gratuitous inducer.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of mouse dihydrofolate reductase gene confers methotrexate resistance in transgenic petunia plants

Transgenic petunia plants containing an altered (Leu22----Arg22) mouse dihydrofolate reductase gene fused to the cauliflower mosiac virus 35S (CaMV 35S) promoter and nopaline synthase (nos) polyadenylation site were obtained by transforming petunia leaf disks with an Agrobacterium tumefaciens strain carrying the chimeric gene. Transformants were directly selected for and rooted on medium containing 1 microM methotrexate (MTX). The chimeric gene was present in the regenerated plants at one to three copies and produced the expected 950-nucleotide-long transcript based on Southern and Northern hybridization analyses, respectively. Leaf pieces from the regenerated transgenic plants were able to form callus when cultured on medium containing 1 microM MTX and were able to incorporate 32P into high-molecular-weight DNA in the presence of greater than 100 microM MTX, thus demonstrating that the chimeric mouse dhfr gene was fully functional and useful as a selectable marker in plant transformation experiments. To date, this is the first report of successful expression of a vertebrate gene in transformed plant cells.

Automatic control in anesthesia: a comparison in performance between the anesthetist and the machine

This report is divided into two parts. First, we developed two new servo control systems by modifying an existing one. The original system was designed to control inspired halothane concentration using mean arterial pressure; the two new systems were designed to control inspired halothane concentration using end-tidal concentration or to control mean arterial pressure using the automated infusion of nitroprusside. Second, we compared the performance of experienced physician and nurse anesthetists (nine, six, and six experiments, respectively). The experiments incorporated a standardized testing sequence of two changes in desired blood pressure (set point) and two pharmacologically induced disturbances in blood pressure (perturbations). The scoring was designed to examine how fast blood pressure changed (90% response time), how far past the set point it went (overshoot), how long it took to eliminate most of the fluctuations in blood pressure (settling time), and the degree of fluctuation of blood pressure after settling (stability). Given three systems to be tested, there were (3 X 14) 42 possible mean scores for the machine and 42 for the anesthetists. The machine scored better than the anesthetists in 38 out of 42 of the mean scores; the differences were statistically significant in 19 out of 42 scores. The wide scatter in performances of the anesthetists prevented the achievement of significance in nine cases with large differences between means. Thus when the scores from the three systems were combined to achieve a larger n value, the machine outperformed the anesthetist in 12 out of 14 scores.(ABSTRACT TRUNCATED AT 250 WORDS)