Identification of an IV-dextrose solution as the source of an outbreak of Klebsiella pneumoniae sepsis in a newborn nursery.
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Cross Infection↗
Biomedical subjects
K Jacobson
Publications and source records attributed to K Jacobson.
Late cytomegalovirus pneumonia in adult allogeneic blood and marrow transplant recipients.
To assess the impact of antiviral prophylaxis during the first 3 months after transplantation on the frequency, timing, and outcome of cytomegalovirus (CMV) pneumonia during the first year, 541 adult allogeneic blood and marrow transplant recipients were evaluated. Thirty-four patients (6.3%) developed 35 episodes of CMV pneumonia at a mean of 188 days after transplantation, with an associated mortality rate of 76%. Twenty-six episodes (74%) occurred late (after day 100). Of the patients with late CMV pneumonia almost all (92%) had chronic graft vs. host disease or had received T cell-depleted transplants. Fourteen late CMV pneumonias (54%) were associated with serious concurrent infections, and 100% of these episodes were fatal. In conclusion, although the frequency of CMV pneumonia in the early posttransplantation period may be substantially reduced by prophylaxis, CMV continues to be a major cause of morbidity and mortality in the late period. Some subsets of patients need more prolonged surveillance and prophylaxis and/or preemptive therapy.
Adolescent↗
FGF is an essential regulator of the fifth cell division in preimplantation mouse embryos.
Fibroblast growth factor (FGF) signaling is required prior to gastrulation in the mouse embryo. To test for the spatial and temporal requirements of FGF signaling, a dominant negative FGF receptor (dnFGFR) was used to make transgenic mouse embryos. In mosaic embryos, cell division ceased at the fifth cell division in all cells that expressed the mutant receptor, but cell death did not increase. After the fifth cell division, the progeny of unaltered cells and cells expressing lacZ continued to accumulate at the same rate, suggesting that the FGF requirement is cell autonomous. In mosaic embryos, lacZ, but not dnFGFR expression was detected in mitotic trophoblasts adjacent to the ICM. Conversely, dnFGFR-expressing extraembryonic ectoderm cells were detected at the abembryonic pole in postmitotic cells. In blastocysts expressing the dnFGFR in all cells, the morphology appeared normal and inner cell masses (ICMs) formed, but resultant embryos had only one-third the number of cells as control embryos. In these blastocysts, cell division had also ceased at the fifth cell division, but cavitation, a concurrent morphogenetic event, initiated and progressed normally. To test for the continuing requirement of FGF, FGFR-3 was overexpressed in all cells and resulted in an increase in cell numbers after the fifth cell cycle. In a model for postimplantation development, addition of FGF-4 to blastocyst outgrowths increased the number of extraembryonic ectoderm cells, suggesting a continuing role for FGF. Thus, FGF signaling induces the cell division of embryonic and extraembryonic cells in the preimplantation mouse embryo starting at the fifth cell division. The signal requirement for FGF is cell autonomous, but is not required to prevent cell death. This provides the first evidence for the necessity of a growth factor before implantation.
Animals↗
Integrin involvement in keratocyte locomotion.
Keratocytes are useful in the study of locomotion because they move rapidly (up to 1 micron/second) while maintaining an almost uniform shape, speed and direction. The smooth gliding motion of the keratocyte requires a precise coordination between adhesion, contractility, and retraction. To ask what role integrins play in keratocyte adhesion and locomotion, either RGD peptides or an anti-beta1 integrin mAb that binds to an ectodomain epitope and inhibits adhesion formation was added to the culture media of moving keratocytes. The response to these reagents depended on three interrelated factors: the dose of RGD/mAb, the apparent adhesion strength of the keratocyte to the substratum and the cell speed. High doses cause keratocytes to quickly and irreversibly round up. At intermediate RGD/mAb doses, keratocytes reestablish adhesion after treatment and briefly resume locomotion until partial detachment recurs. At the lowest doses, disruption of beta1 integrin-mediated adhesion formation destabilizes the lamella, temporarily preventing lamellar extension and forward movement of the cell. With increasing culture time, there is an increase in apparent adhesion and a corresponding marked decrease in locomotory velocity. Under these conditions, high doses of RGD/mAb do not cause keratocytes to detach or even produce detectable lamellar instabilities. We postulate that RGD/mAb competitively inhibits new beta1 integrin mediated adhesion formation that is required to support the rates of lamellar extension necessary for rapid locomotion.
Animals↗
Expression of fibroblast growth factor receptors in peri-implantation mouse embryos.
FGF receptor (FGFR) function is essential during peri-implantation mouse development. To understand which receptors are functioning, we tested for the expression of all four FGF receptors in peri-implantation blastocysts. By RT-PCR, FGFR-3 and FGFR-4 were detected at high levels, FGFR-2 at lower levels, and FGFR-1 was detected at background levels compared to control tissues. Because FGFR-3 and FGFR-4 were detected at the highest levels, we studied these in detail. Between 3.5 days after fertilization (E3.5) and E6.0, FGFR-4 mRNA was detected ubiquitously in the peri-implantation embryo, restricted to the inner cell mass (ICM) and its derivatives and primitive endoderm by E6.0, and was not detected at E6.5. FGFR-3 mRNA was detected ubiquitously in the peri-implantation embryo with a tendency towards extraembryonic cells. We tested blastocyst outgrowths, a model for implantation, for FGFR-3 and FGFR-4 protein. FGFR-3 protein was detected in all cells early during the outgrowth. Later, FGFR-3 was detected in the extraembryonic endoderm and trophoblast giant cells (TGC), but not in the ICM. FGFR-4 protein was detected in all cells of the implanting embryo, but was restricted to the ICM/primitive endoderm in later stage outgrowths. The distribution of the receptor proteins in the blastocyst outgrowths is similar to the distribution of the mRNA detected by in situ hybridization of sections of embryos. The data suggest roles for FGFR-3 and FGFR-4 in peri-implantation development.
Animals↗
Clinical and radiological features of pulmonary disease caused by rapidly growing mycobacteria in cancer patients.
The role of rapidly growing mycobacteria in the pathogenesis of pulmonary disease is being increasingly recognized; however, the clinical significance of these mycobacteria in patients with underlying malignancy has not been well studied. Over a 6-year period, 37 cancer patients with rapidly growing mycobacteria isolated from respiratory specimens were identified at our center. Mycobacterium chelonae group was isolated in 24 cases and Mycobacterium fortuitum in 13 cases. Of the 24 cases with cultures yielding Mycobacterium chelonae group, eight met the study criteria for infection and were determined to be clinically significant, whereas only one of the Mycobacterium fortuitum isolates was determined to represent infection. An average of two antimicrobial agents were used for treatment, most commonly clarithromycin, ciprofloxacin, and trimethoprim/sulfamethoxazole. Although the isolation of rapidly growing mycobacteria represents colonization in most cases, these bacteria, especially the Mycobacterium chelonae group, may cause pulmonary disease in cancer patients. The clinical and radiological findings are usually non-specific in this population, and patients with respiratory cultures yielding rapidly growing mycobacteria should be assessed carefully to distinguish infection from colonization. Effective therapy can be provided with oral regimens that include at least two antibiotics to which the organism is susceptible.
Adolescent↗
Local measurements of viscoelastic parameters of adherent cell surfaces by magnetic bead microrheometry.
A magnetic bead microrheometer has been designed which allows the generation of forces up to 10(4) pN on 4.5 micron paramagnetic beads. It is applied to measure local viscoelastic properties of the surface of adhering fibroblasts. Creep response and relaxation curves evoked by tangential force pulses of 500-2500 pN (and approximately 1 s duration) on the magnetic beads fixed to the integrin receptors of the cell membrane are recorded by particle tracking. Linear three-phasic creep responses consisting of an elastic deflection, a stress relaxation, and a viscous flow are established. The viscoelastic response curves are analyzed in terms of a series arrangement of a dashpot and a Voigt body, which allows characterization of the viscoelastic behavior of the adhering cell surface in terms of three parameters: an effective elastic constant, a viscosity, and a relaxation time. The displacement field generated by the local tangential forces on the cell surface is visualized by observing the induced motion of assemblies of nonmagnetic colloidal probes fixed to the membrane. It is found that the displacement field decays rapidly with the distance from the magnetic bead. A cutoff radius of Rc approximately 7 micron of the screened elastic field is established. Partial penetration of the shear field into the cytoplasm is established by observing the induced deflection of intracellular compartments. The cell membrane was modeled as a thin elastic plate of shear modulus mu * coupled to a viscoelastic layer, which is fixed to a solid support on the opposite side; the former accounts for the membrane/actin cortex, and the latter for the contribution of the cytoskeleton to the deformation of the cell envelope. It is characterized by the coupling constant chi characterizing the elasticity of the cytoskeleton. The coupling constant chi and the surface shear modulus mu * are obtained from the measured displacements of the magnetic and nonmagnetic beads. By analyzing the experimental data in terms of this model a surface shear modulus of mu * approximately 2 . 10(-3) Pa m to 4 . 10(-3) Pa m is found. By assuming an approximate plate thickness of 0.1 micron one estimates an average bulk shear modulus of mu approximately (2 / 4) . 10(-4) Pa, which is in reasonable agreement with data obtained by atomic force microscopy. The viscosity of the dashpot is related to the apparent viscosity of the cytoplasm, which is obtained by assuming that the top membrane is coupled to the bottom (fixed) membrane by a viscous medium. By application of the theory of diffusion of membrane proteins in supported membranes we find a coefficient of friction of bc approximately 2 . 10(9) Pa s/m corresponding to a cytoplasmic viscosity of 2 . 10(3) Pa s.
3T3 Cells↗
Design and use of substrata to measure traction forces exerted by cultured cells.
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Algorithms↗
Electronic cameras for low-light microscopy.
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Electronics↗
A descriptive study of breast cancer worry.
Women with (n = 65) and without (n = 70) a family history of breast cancer reported on their thoughts and concern about the disease. Measures were taken across a 1-month interval and at a 1-year follow-up. Reported screening behaviors were also measured at baseline and the 1-year follow-up. Worry dissipated over time, suggesting that worry levels are affected by the measurement context. However, women with a family history of the disease maintained greater worry than those without such a history, suggesting that they may be chronically worried about the disease. Thinking and worrying about breast cancer were both modestly and positively related to the frequency of screening behaviors, suggesting that some kinds of worry can motivate self-protective behavior.
Adaptation, Psychological↗
Maturation of cell-substratum focal adhesions induced by depolymerization of microtubules is mediated by increased cortical tension.
Dynamics of alterations of focal adhesions (FA) induced by a microtubule-depolymerizing drug, colcemid, was examined in several types of fibroblastic cells. Evolution of individual FA in cultured cells was monitored by interference-reflection microscopy (IRM); at the end of the monitoring period (3 hours) the cells were fixed and immunofluorescence microscopy of the same FA was performed with an antibody against vinculin. Control and colcemid-treated cells remained non-motile and did not show lamellipodial activity at the edges. During the incubation, formation of new FA or disappearance of pre-existing FA did not occur in either colcemid-treated or control cultures. However, FA in colcemid-treated cells significantly increased in size in the course of a 3 hour incubation. The growth of FA was centripetal and sometimes was accompanied by the fusion of several adjacent FA. Immunofluorescence examination showed that colcemid-induced growth of FA was accompanied by accumulation of several proteins specific for these structures including vinculin, talin, paxillin and pp125FAK kinase. Immunoblotting with anti-vinculin antibody showed that incubation with colcemid considerably increased the amount of vinculin associated with the ventral membranes due to its partial redistribution from a soluble pool into the growing adhesions. A substantial increase in tyrosine phosphorylation of pp125FAK was also observed in colcemid-treated cells. In cells plated on elastic silicone rubber films, colcemid induced formation of wrinkles in the films and these wrinkles relaxed after treatment with cytochalasin D. These results confirm that microtubule depolymerization increases traction transmitted to the substratum by the actin cortex and shows that an increase in cortical tension accompanies maturation of FA. Taken together, these data show that short-term incubation with colcemid does not affect the formation of initial FA. In contrast, microtubule depolymerization considerably stimulates the maturation FA, manifested by their centripetal growth. Maturation is proposed to be mediated by increased cortical tension, which is caused by microtubule depolymerization.
Animals↗
Measurement of traction forces in cells locomoting along a substratum. Video supplement.
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Animals↗
Juvenile rheumatoid arthritis in a Canadian First Nations (aboriginal) population: onset subtypes and HLA associations.
OBJECTIVE: To determine onset subtypes and HLA associations of juvenile rheumatoid arthritis (JRA) in a First Nations (aboriginal) population; to determine whether population frequencies of HLA antigens may explain the distribution of subtypes of JRA in this population. METHODS: All patients were children from Manitoba and Northwestern Ontario seen in a single pediatric rheumatology clinic between 1975 and 1996. Patients were identified from a clinic registry. Controls were adults of Algonkian Cree and Ojibway heritage. Class I and II major histocompatibility (HLA) typing was performed for First Nations patients and controls. RESULTS: There were a total of 74 First Nations patients with JRA. The relative frequency of rheumatoid factor (RF) positive polyarticular JRA was higher and that of pauciarticular JRA was lower in First Nations compared with Caucasian patients (42 versus 3% and 22 versus 58%, respectively; p = 0.00000). HLA-DRB1*04 (63%), 08 (43%), and 1402 (25%) were the most common DRB1 antigens among controls. The main subtypes of DRB1*04 were 0404 (33% of controls) and 0407 (23%). HLA typing was performed for 39 First Nations patients; 27 were Cree or Ojibway, 4 were from other tribes, and 8 were part First Nations. Among Cree and Ojibway, 59% of controls and 63% of patients with RF positive polyarticular JRA (n = 16) had HLA-DRB1 antigens bearing the rheumatoid arthritis (RA) shared epitope (OR 1.16, 95% CI: 0.38, 3.48). The OR for polyarticular RF positive JRA in those with DRB1*0802 and 0901 were 0.15, 95% CI: 0.02; and 1.24 and 5.83, 95% CI: 1.58, 28.38, respectively. CONCLUSION: There was a high frequency of the RA shared epitope represented by both HLA-DRB1*0404 and 1402 in this Algonkian population. This high frequency may explain the high frequency of RF positive polyarticular JRA. DRB1*0802 may be protective, whereas DRB1*0901 may increase the risk for this subtype of JRA.
Adult↗
HLA associations of seropositive rheumatoid arthritis in a Cree and Ojibway population.
OBJECTIVE: To determine the HLA associations of seropositive rheumatoid arthritis (RA) in a Cree and Ojibway population; to determine whether specific alleles distinguish juvenile or adult onset. METHODS: HLA-A, B, C, and DRB1 alleles were analyzed in 23 Ojibway and Cree patients with RA seen in a single tertiary care center. Comparisons were made with published results of controls and with results of 18 patients with rheumatoid factor (RF) positive polyarticular juvenile rheumatoid arthritis (JRA) from the same population. RESULTS: Comparisons among patients with RA, patients with RF positive polyarticular JRA, and controls showed increased frequencies of the RA shared epitope in patients with RA and of DRB1*0901 in patients with seropositive polyarticular JRA, while the frequency of DRB1*08 alleles was decreased in patients with RF positive polyarticular JRA. CONCLUSION: In this population, DRB1*0901 may promote while DRB1*08 alleles may protect against a juvenile onset of RA specifically. In contrast, the RA shared epitope may have a greater effect on the risk of adult onset seropositive RA. Due to the small patient numbers, these results require confirmation.
Adult↗
Transient confinement of a glycosylphosphatidylinositol-anchored protein in the plasma membrane.
Glycosylphosphatidylinositol (GPI)-anchored proteins participate in many cell surface functions; however, the molecular associations of these lipid-linked proteins within the plasma membrane are not well understood. Recent biochemical analyses of detergent insoluble membrane fractions have suggested that GPI-anchored proteins may be associated with glycosphingolipid (GSL)-enriched domains that also contain cholesterol and signaling molecules such as Src family kinases and, in some cases, caveolae. The movements of two components of the putative GSL-enriched domains, Thy-1, a GPI-anchored protein, and GM1, a GSL, were followed with single particle tracking on C3H 10T1/2 cell surfaces and categorized into four modes of lateral transport, fast diffusion, slow anomalous diffusion, diffusion confined to 325-370 nm diameter regions, and a fraction of molecules that was essentially stationary on the 6.6 s time scale. Longer observations (60 s) showed that Thy-1 and GM1 are transiently confined for 7-9 s to regions averaging 260-330 nm in diameter. Approximately 35-37% of both Thy-1 and GM1 undergo confined diffusion, whereas only 16% of fluorescein phosphatidylethanolamine, a phospholipid analog which is not expected to be found in the GSL domains, experience confined diffusion to regions averaging approximately 230 nm in diameter. Further, when glycosphingolipid expression was reduced approximately 40% with the glucosylceramide synthase inhibitor, d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, the percentage of trajectories exhibiting confinement and the size of the confining domain for Thy-1 were reduced approximately 1.5-fold. In contrast, extraction of cells with Triton X-100 leaves the fraction of molecules confined and the domain sizes of Thy-1 and GM1 unchanged. Our results are consistent with the preferential association of GPI-anchored proteins with glycosphingolipid-enriched domains and suggest that the confining domains may be the in vivo equivalent of the detergent insoluble membrane fractions.
Animals↗
The mechanism of altered neural function in a rat model of acute colitis.
BACKGROUND & AIMS: Distal colitis induced in rats by trinitrobenzene sulfonic acid (TNBS) causes a suppression of [3H]noradrenaline release from the myenteric plexus, of inflamed distal colon, as well as in noninflamed regions of colon and ileum. The aim of this study was to explore the mechanisms underlying these neural changes in TNBS colitis. METHODS: Colitis was induced by intrarectal administration of TNBS, and the animals were killed on day 5. Inflammation was assessed by measuring myeloperoxidase (MPO) activity, and noradrenaline release was measured as 3H release from rats myenteric plexus preparations preloaded with [3H]noradrenaline. These end points were examined: (1) after administration of the locally active steroid budesonide; (2) in congenitally athymic rats; and (3) in rats treated with the interleukin 1 receptor antagonist (IL-1ra) to interleukin 1 beta. RESULTS: In colitis, both topical budesonide and systemic IL-1ra treatments attenuated the suppression of KCl-evoked 3H release from longitudinal muscle myenteric plexus in both inflamed and noninflamed segments. However, neither of these treatments altered MPO activity. A similar suppression of [3H]noradrenaline release was observed in athymic rats after TNBS, although there was a substantially greater increase in MPO activity compared with euthymic rats with colitis. CONCLUSIONS: TNBS-induced colitis alters myenteric nerve function at inflamed and noninflamed sites via a steroid-sensitive and interleukin 1-mediated process that does not require T lymphocytes.
Acute Disease↗
Single-particle tracking: applications to membrane dynamics.
Measurements of trajectories of individual proteins or lipids in the plasma membrane of cells show a variety of types of motion. Brownian motion is observed, but many of the particles undergo non-Brownian motion, including directed motion, confined motion, and anomalous diffusion. The variety of motion leads to significant effects on the kinetics of reactions among membrane-bound species and requires a revision of existing views of membrane structure and dynamics.
Diffusion↗
The composition and dynamics of cell-substratum adhesions in locomoting fish keratocytes.
Close contacts are the predominant type of cell-substratum adhesion in rapidly moving cells yet little is known about their composition and dynamics. To address these issues we have attempted to identify the molecular components of close contacts formed in rapidly moving fish epithelial keratocytes. In addition we have utilized the simple shape of keratocytes to explore the relationship between close contact formation and rapid locomotion. Beta1 integrin and talin molecules were found to be localized within a narrow rim of very close contact along the leading edge. These molecules together with vinculin were also found within small foci distributed evenly throughout the lamella, corresponding to regions of variable close contact. Alpha-actinin was found in foci within older, more posteriorly located regions of the lamella and along stress fibers. In addition to close contacts, small focal adhesion-like structures which stained positively for all antibodies tested were found at the tips of stress fibers within retracting cell margins. Interference reflection and total internal reflection microscopy of moving keratocytes showed cell-substratum contacts to be organized into distinct patterns that appear to move forwards, in concert with the leading edge. A feature common to all cells is a rim of very close contact at the leading edge. This region is specialized for the formation of new cell-substratum adhesions and is the site where patterns of close contact are generated. We have found that cell locomotion is most rapid when a uniform contact pattern is present but cell speed is progressively reduced as the contact pattern becomes more irregular. Furthermore, the local rate of lamellar extension is most rapid when underlain by regions of intermediate closeness to the substratum, but is reduced or ceases if the underlying contact is either very close or more distant, respectively. Our results suggest that close contacts and focal adhesions are related structures formed from a common hierarchy of molecular interactions. In addition the relationship between close contact formation and lamellar extension indicates a direct coupling between these two processes at the leading edge. Furthermore, we can explain the dynamic behaviour of close contacts in terms of the relative rates of trapping and release of component molecules that is initiated at the leading edge. We suggest that regulation of the molecular dynamics involved in leading edge specialization determines both the pattern of cell-substratum contacts and the net rate of actin filament assembly.
Animals↗