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K Jacobson

Publications and source records attributed to K Jacobson.

At least 19 recordsLinked to original sources
PubMed2002

Oxidation of orthopaedic UHMWPE.

Retrieved EtO sterilised acetabular cups usually show much less degradation than gamma-ray sterilised cups. Some of our retrieved EtO sterilised cups did, however, reveal unexpected bulk oxidation. It was observed that this oxidation was always accompanied by whitening of the material. This whitening was found to be due to a break-up of the compression moulded material into its original particles. It was noticed that there was no oxidation in all parts, where the break-up and whitening appeared. The oxidation did, however, occur exclusively in the parts where there was a badly consolidated material. Upon examining shelf aged, unsterilised samples, it was found that the degradation was also present here. This shows that the observed phenomenon is not due to the service in vivo and that it must originate from the processing step. Just as for the retrieved samples, the shelf aged cups only showed oxidation in the bulk and not at the surface. It was concluded that the material used for the cups had been badly fused together during the compression moulding and that the machining had created a bad stress situation in the cups leading to a break-up of the particles. The mechanism that initiates the oxidation is not known, but it is believed that the distribution depends on how the internal stresses have acted to break up the structure. In the areas where the particles have been separated, there is probably a higher availability of oxygen than what is normally observed in UHMWPE.

Biocompatible Materials↗
PubMed2002

The joint analysis of personal interview and family history diagnoses: evidence for validity of diagnosis and increased heritability estimates.

BACKGROUND: Psychiatric diagnoses obtained at personal interview are only moderately reliable and depend critically on accurate self-observation. Reports by family members provide additional information but may be biased. It is unclear how best to combine these two sources of diagnostic data. METHODS: Using complete data on lifetime prevalence for six disorders in approximately 1200 male-male twin pairs from a population based registry, we first applied a standard bivariate twin model--which treats self-diagnoses and informant-diagnoses as separate phenotypes--and then examined a 'multiple-rater' model--which assumes that self-report and co-twin-report are fallible indices of one underlying disease liability. Best-fit models were chosen using Akaike's information criterion. RESULTS: Standard bivariate analyses indicated that the same genetic factors accounted for variation in self-reported and co-twin-reported diagnoses. The multiple-rater model produced a substantial decrease in variance attributed to individual-specific environment and a proportional increase in heritability of liability for major depression, generalized anxiety disorder, alcohol dependence and adult antisocial behaviour, but not for drug abuse/dependence or regular tobacco use. The best-fit model consistently included either a 'bias' or a 'correlated error' path. No evidence for family environmental risk factors was found for any disorder. CONCLUSION: The genetic factors that influence self-report psychiatric illness also influence psychiatric illness as described by relatives. For many psychiatric disorders, incorporation of self-report and family history data in a single model may reduce measurement error and increase estimates of heritability. However, account must be taken of the fact that family history reports are systematically biased. While promising, these results are preliminary and require replication.

Adult↗
PubMed2001

Drop attacks in older patients secondary to an otologic cause.

The clinical features and treatment of seven patients with drop attacks attributable to inner ear disease presenting after age 65 are described. A neurologic or cardiovascular cause of drop attacks was initially suspected. Audiovestibular testing documented a unilateral inner ear disorder. The salient clinical features of these cases are discussed. The patients underwent ablative vestibular surgery, and all compensated well and were free of vertigo and falls up to 10 years postoperatively.

Aged↗
PubMed2001

Partitioning of Thy-1, GM1, and cross-linked phospholipid analogs into lipid rafts reconstituted in supported model membrane monolayers.

As shown earlier, raft-like domains resembling those thought to be present in natural cell membranes can be formed in supported planar lipid monolayers. These liquid-ordered domains coexist with a liquid-disordered phase and form in monolayers prepared both from synthetic lipid mixtures and lipid extracts of the brush border membrane of mouse kidney cells. The domains are detergent-resistant and are highly enriched in the glycosphingolipid GM1. In this work, the properties of these raft-like domains are further explored and compared with properties thought to be central to raft function in plasma membranes. First, it is shown that domain formation and disruption critically depends on the cholesterol density and can be controlled reversibly by treating the monolayers with the cholesterol-sequestering reagent methyl-beta-cyclodextrin. Second, the glycosylphosphatidylinositol-anchored cell-surface protein Thy-1 significantly partitions into the raft-like domains. The extent of this partitioning is reduced when the monolayers contain GM1, indicating that different molecules can compete for domain occupation. Third, the partitioning of a saturated phospholipid analog into the raft phase is dramatically increased (15% to 65%) after cross-linking with antibodies, whereas the distribution of a doubly unsaturated phospholipid analog is not significantly affected by cross-linking (approximately 10%). This result demonstrates that cross-linking, a process known to be important for certain cell-signaling processes, can selectively translocate molecules to liquid-ordered domains.

Antibodies↗
PubMed2001

Local photorelease of caged thymosin beta4 in locomoting keratocytes causes cell turning.

The broad aim of this work was to explore the feasibility of using light-directed perturbation techniques to study cell locomotion. Specifically, a caged form of thymosin beta4 (Tbeta4) was photoactivated in a defined local region of locomoting fish scale keratocytes and the resulting perturbation of locomotion was studied. Purified Tbeta4 was produced in an inactive form by "caging" with ([n-nitroveratryl]oxy)chlorocarbamate. In vitro spectrophotofluorometric assays indicated that caged Tbeta4 did not change the normal actin polymerization kinetics, whereas photoactivated Tbeta4 significantly inhibited actin polymerization. With an a priori knowledge of the cytoplasmic diffusion coefficient of Tbeta4 as measured by fluorescence recovery after photobleaching experiments, the rapid sequestration of actin monomers by uncaged Tbeta4 and the consequent reduction in the diffusional spread of the Tbeta4-actin complex were predicted using Virtual Cell software (developed at the Center for Biomedical Imaging Technology, University of Connecticut Health Center). These simulations demonstrated that locally photoactivating Tbeta4 in keratocytes could potentially elicit a regional locomotory response. Indeed, when caged Tbeta4 was locally photoactivated at the wings of locomoting keratocytes, specific turning about the irradiated region was observed, whereas various controls were negative. Additionally, loading of exogenous Tbeta4 into both keratocytes and fibroblasts caused very rapid disassembly of actin filaments and reduction of cellular contractility. Based on these results, a mechanical model is proposed for the turning behavior of keratocytes in response to photoreleased Tbeta4.

3T3 Cells↗
PubMed2001

Adenovirus infections in adult recipients of blood and marrow transplants.

Adenoviruses are increasingly recognized pathogens that affect blood and marrow transplant (BMT) recipients. Experiences with 2889 adult BMT recipients were reviewed to study the incidence, clinical spectrum, risk factors for dissemination, response to therapy, and outcome of adenovirus infections. Eight-five patients (3%) were diagnosed by means of culture (n=85) or culture and histopathological examination (n=6). Nine patients had asymptomatic viruria, and 76 had symptomatic infections, which included upper respiratory tract infection (n=20), enteritis (n=18), hemorrhagic cystitis (n=10), pneumonia (n=15), and disseminated disease (n=13). The overall mortality rate was 26%. A higher mortality rate was observed among patients with pneumonia (73%) and disseminated disease (61%). Risk factors for dissemination included receipt of an allogeneic transplant, presence of graft-versus-host disease (GVHD), and receipt of concurrent immunosuppressive therapy. Intravenous ribavirin was not associated with an appreciable benefit among 12 patients who received this treatment. In conclusion, adenovirus infections are an important cause of morbidity and mortality in adult BMT recipients, particularly allogeneic transplant recipients with GVHD who are receiving immunosuppressive therapy. The need for an effective, nontoxic antiviral therapy is apparent.

Adenoviridae Infections↗
PubMed2001

Cytomegalovirus pneumonia in adults with leukemia: an emerging problem.

Cytomegalovirus (CMV) pneumonia is reportedly unusual among adults with leukemia who have not undergone transplantation. To assess the frequency of CMV pneumonia and its outcome during the present time, we reviewed the experience of 2136 hospitalized adults with leukemia. Sixty-one patients (2.9%) had CMV pneumonia diagnosed. The frequency doubled from 1.4% in 1992--1994 to 2.8% in 1995--1997 (P<.05). Fifty-four patients (89%) had received treatment with an immunosuppressive chemotherapeutic regimen that contained fludarabine (n=37), high-dose cytoxan (n=17), or both (n=10), and 15 patients (25%) had received granulocyte transfusions that were stimulated with hematopoietic growth factors from unscreened donors. The overall CMV pneumonia--associated mortality rate was 57%. Among autopsied patients who had leukemia, the frequency of CMV pneumonia increased from 0%, 2.3%, and 0% in 1992, 1993, and 1994, respectively, to 4.6%, 6.5%, and 16% in 1995, 1996, and 1997, respectively (P<.05). CMV has emerged as an important cause of life-threatening pneumonia in adults with leukemia who have received potent immunosuppressive therapies and stimulated granulocyte transfusions from unscreened donors.

Adult↗
PubMed2001

Activation of A(3)adenosine receptor protects against doxorubicin-induced cardiotoxicity.

Adenosine exerts a marked protective effect on the heart during cardiac ischemia. This protection is mediated by binding to the A(1)and A(3)subtypes of adenosine receptor (A(1)R and A(3)R, respectively). The objective of the present study was to investigate whether activation of A(1)and A(3)adenosine receptors may reduce doxorubicin-induced damage to cardiomyocytes in culture. Cultured cardiomyocytes from newborn rats were treated with 0.5--5 microm doxorubicin (DOX) for 18 h and then incubated in drug-free medium for an additional 24 h. This treatment resulted in cell damage and lactate dehydrogenase release, even after low (0.5 microm) doses of the drug, and increased in a concentration-dependent manner. Activation of A(3)-subtype but not A(1)-subtype receptors attenuated doxorubicin-cardiotoxicity after drug treatment for 18 h followed by 24 h incubation in drug-free medium. Modulation of intracellular calcium mediated by activation of A(3)R, but not by A(1)R, in cultured myocytes suggested an important pathophysiological significance of this subtype of adenosine receptors. Protection by A(3)R agonist Cl-IB-MECA (2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide) following DOX treatment is evident in: (1) decreases in intracellular calcium overloading and abnormalities in Ca(2+)transients; (2) reduction of free-radical generation and lipid peroxidation; (3) attenuation of mitochondrial damage by protection of the terminal link (COX-complex) of respiratory chain; (4) attenuation of the decrease in ATP production and irreversible cardiomyocyte damage. Cardioprotection caused by Cl-IB-MECA was antagonized considerably by the selective A(3)adenosine receptor antagonist MRS1523.

Adenosine↗
PubMed2001

Lipid rafts reconstituted in model membranes.

One key tenet of the raft hypothesis is that the formation of glycosphingolipid- and cholesterol-rich lipid domains can be driven solely by characteristic lipid-lipid interactions, suggesting that rafts ought to form in model membranes composed of appropriate lipids. In fact, domains with raft-like properties were found to coexist with fluid lipid regions in both planar supported lipid layers and in giant unilamellar vesicles (GUVs) formed from 1) equimolar mixtures of phospholipid-cholesterol-sphingomyelin or 2) natural lipids extracted from brush border membranes that are rich in sphingomyelin and cholesterol. Employing headgroup-labeled fluorescent phospholipid analogs in planar supported lipid layers, domains typically several microns in diameter were observed by fluorescence microscopy at room temperature (24 degrees C) whereas non-raft mixtures (PC-cholesterol) appeared homogeneous. Both raft and non-raft domains were fluid-like, although diffusion was slower in raft domains, and the probe could exchange between the two phases. Consistent with the raft hypothesis, GM1, a glycosphingolipid (GSL), was highly enriched in the more ordered domains and resistant to detergent extraction, which disrupted the GSL-depleted phase. To exclude the possibility that the domain structure was an artifact caused by the lipid layer support, GUVs were formed from the synthetic and natural lipid mixtures, in which the probe, LAURDAN, was incorporated. The emission spectrum of LAURDAN was examined by two-photon fluorescence microscopy, which allowed identification of regions with high or low order of lipid acyl chain alignment. In GUVs formed from the raft lipid mixture or from brush border membrane lipids an array of more ordered and less ordered domains that were in register in both monolayers could reversibly be formed and disrupted upon cooling and heating. Overall, the notion that in biomembranes selected lipids could laterally aggregate to form more ordered, detergent-resistant lipid rafts into which glycosphingolipids partition is strongly supported by this study.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

A chemical analysis of the clogging process of polymeric biliary endoprostheses.

Insertion of polymeric biliary endoprostheses is widely used as a method of palliation of malignant strictures of the biliary tree. Despite the success of this technique, clogging of the stent in a few months is still an existing problem. The aim of the present study has been to investigate the causes of the obstruction, considering both the stent material and the composition of the obstructing deposit. 16 ready-to-implant and 33 occluded retrieved prostheses were analysed by ATR-FTIR spectroscopy. The clogging sludge was recovered and studied by FTIR spectroscopy and pyrolysis derivatisation/gas chromatography/mass spectrometry (Py/GC/MS). The results of the analyses showed that the deposit was mainly formed by proteins, bilirubin, calcium palmitate and bilirubinate, cholesterol and its fatty acids salts. It was found that approximately 50% of the examined ready-to-implant samples were made of ethylene-vinylacetate copolymer (EVA) instead of polyethylene (PE), as was stated in the producer declaration. Moreover, 94% of the retrieved samples were found to be made of EVA indicating that this material is less suitable than PE for this application. All retrieved PE and EVA stents showed a protein-like black layer strongly absorbed on the surface.

Biliary Tract↗
PubMed2001

EGF-stimulated lamellipod extension in adenocarcinoma cells.

The extension of lamellipodia has been triggered by the application of epidermal growth factor (EGF). We have used an atomic force microscope (AFM) to investigate this lamellipodial extension. During extension we could detect an increase in height from about 500 nm for the stable lamellipodium to typical values of 600-800 nm for the extending lamellipodium. The AFM was also used to determine the mechanical properties of the lamellipodium where we found a decrease of the elastic modulus by a factor of 1.4 at the same location within the same cell. Both findings are consistent with the cortical expansion hypothesis, suggesting that severing of actin filaments, leading to a swelling of the cytoskeleton, generates the protrusive force during lamellipodial extension.

Adenocarcinoma↗
PubMed2001

Infectious diarrhea in children.

Infectious diarrhea in children remains an important cause of morbidity in North America with rotavirus, nontyphoidal salmonella, Campylobacter and Giardia being the predominant pathogens in children younger than 5 years. Knowledge of the epidemiology of the diarrheal illness in a community together with the clinical information are necessary when determining the extent of investigation. Oral rehydration remains the mainstay of therapy and antibiotics are reserved for specific clinical situations and infections.

Adolescent↗
PubMed2001

Direct, high-resolution measurement of furrow stiffening during division of adherent cells.

It is unclear whether cell division is driven by cortical relaxation outside the equatorial region or cortical contractility within the developing furrow alone. To approach this question, a technique is required that can monitor spatially-resolved changes in cortical stiffness with good time resolution. We employed atomic force microscopy (AFM), in force-mapping mode, to track dynamic changes in the stiffness of the cortex of adherent cultured cells along a single scan-line during M phase, from metaphase to cytokinesis. Video microscopy, which we used to correlate the AFM data with mitotic events identified by light microscopy, indicated that the AFM force-mapping technique does not perturb dividing cells. Here we show that cortical stiffening occurs over the equatorial region about 160 seconds before any furrow appears, and that this stiffening markedly increases as the furrow starts. By contrast, polar relaxation of cells does not seem to be an obligatory event for cell division to occur.

Animals↗
PubMed2001

Cytomegalovirus pneumonia in adult autologous blood and marrow transplant recipients.

CMV pneumonia is a major cause of morbidity and mortality among allogeneic BMT recipients. To assess the frequency, timing, risk factors and response to therapy of CMV pneumonia among autologous BMT recipients, we reviewed our experience with 795 patients. Sixteen (2%) patients were diagnosed with CMV pneumonia. The frequency was higher among patients who were seropositive than those who were seronegative (3.3% vs 0%, P = 0.008). Among seropositive patients, the frequency was higher among patients with hematological malignancies than patients with solid tumors (5.0 % vs 1.0%, P = 0.019). Eleven cases occurred <30 days, and five cases occurred >100 days post transplant. The overall CMV pneumonia-related mortality rate was 31%. Seven (78%) of nine patients treated with ganciclovir and IVIG prior to respiratory failure survived; neither of two patients treated after respiratory failure survived. Four of five (80%) untreated patients survived. In conclusion, CMV is a not infrequent cause of pneumonia among autologous BMT recipients. Risk factors include CMV seropositivity and an underlying hematological malignancy. A favorable response hinges on the prompt initiation of therapy. The survival of 25% of the patients without antiviral therapy suggests that the isolation of CMV from a BAL specimen occasionally reflects oropharyngeal contamination or that CMV pneumonia may sometimes be self-limited in more immunocompetent autologous BMT recipients.

Adult↗
PubMed2001

Respiratory syncytial virus infections in autologous blood and marrow transplant recipients with breast cancer: combination therapy with aerosolized ribavirin and parenteral immunoglobulins.

Scant data are available concerning the impact and response to therapy of respiratory syncytial virus (RSV) infections in patients undergoing autologous blood and marrow transplantation (BMT) for breast cancer. During eight winter seasons from 1992-1993 to 1999-2000, nine (4%) of 249 such patients were hospitalized with RSV infections. Six patients, including all five patients who were early post transplant in the pre-engraftment period, developed pneumonia and were treated with a combination of aerosolized ribavirin and IVIG. Among five patients with pneumonia in whom therapy was initiated prior to respiratory failure, one (20%) died. The sixth patient, in whom therapy was initiated after respiratory failure developed, also died. In total, two (1%) patients, both of whom were in the pre-engraftment period, died of progressive pneumonia. In conclusion, RSV is a significant cause of life-threatening pneumonia in autologous BMT recipients with breast cancer during the early post-transplant period, and accounted for a substantial portion of the overall transplant-related mortality, which in recent years has been minimal.

Aerosols↗
PubMed2001

Development of interstitial cells of Cajal in a full-term infant without an enteric nervous system.

The relationship between the development of the enteric nervous system and interstitial cells of Cajal (ICC) in the human small intestine was investigated in a full-term infant who presented with intestinal pseudo-obstruction. Immunohistochemistry revealed absence of enteric nerves and ganglia but abundant c-Kit immunoreactivity associated with Auerbach's plexus (ICC-AP). However, c-Kit immunoreactivity associated with the deep muscular plexus (ICC-DMP) and intermuscular ICC was absent. Electron microscopy showed ICC-AP with a normal ultrastructure; ICC-DMP were seen but were severely injured, suggesting degeneration. In vitro recording of intestinal muscle showed slow wave activity as well as response to cholinergic stimulation. Fluoroscopic examination of the small bowel showed a variety of motor patterns, including rhythmic, propagating contractions. In conclusion, total absence of enteric nerves was associated with absence of normal ICC-DMP. However, a normal musculature, including a network of ICC-AP, allowed for generation of rhythmic, propagating contractile activity, suggesting the presence of functional motor activity.

Biological Clocks↗
PubMed2001

Gastric acid secretory response in Helicobacter pylori-positive patients with duodenal ulcer disease.

BACKGROUND: Patients with duodenal ulcer (DU) have an increased parietal cell mass and sensitivity to secretagogues, with increased acid output. AIM: To determine the effect of Helicobacter pylori eradication on parietal cell sensitivity and gastric acid secretion. SUBJECTS AND METHODS: Twenty-five H pylori-positive DU patients and 18 H pylori-negative healthy volunteers were studied. Serum H pylori immunoglobulin G, basal acid output and acid secretory response to graded doses of pentagastrin were determined before and after treatment, at six months and at one year. Subjects were randomly assigned to ranitidine or sucralfate treatment for six weeks, and all DU patients received bismuth subsalicylate, metronidazole and tetracycline for the first two weeks. RESULTS: H pylori was eradicated in 66% of patients receiving sucralfate and 92% receiving ranitidine. Compared with healthy volunteers, DU patients demonstrated a 2.7-fold greater basal acid output, a 1.3-fold greater peak acid output, significantly higher acid output for each dose of pentagastrin and a 1.38-fold increase in the area under the pentagastrin dose acid response curve. Cure of H pylori, irrespective of ulcer healing regimen, resulted in a gradual decrease in acid secretory capacity with basal acid output, peak acid output and area under the pentagastrin dose acid response curve returning to healthy volunteer levels by one year. No demonstrable differences were observed in parietal cell sensitivity in all subjects before or after treatment. These data suggest that disturbances in acid secretion in H pylori-positive DU patients are not due to an increased parietal cell sensitivity to pentagastrin but rather due to an increased parietal cell mass with increased capacity to secrete acid, which gradually resolves following cure.

Adult↗