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Biomedical subjects

W Timens

Publications and source records attributed to W Timens.

At least 19 recordsLinked to original sources
PubMed2003

[Fulminant pneumococcal sepsis in two splenectomized patients].

Two 41-year-old women, who had previously been splenectomized, were admitted to the intensive-care unit due to fulminant sepsis. On admission, petechiae and ecchymoses characterised the clinical presentation of both patients. Laboratory tests revealed the presence of renal insufficiency and thrombocytopenia with disseminated intravascular coagulation. Streptococcus pneumoniae with serotypes (24 and 38) not included in the current polyvalent pneumococcal vaccine were found in blood cultures from both patients. One patient died as a result of a refractory septic shock. The other patient, who had never been vaccinated with the polyvalent pneumococcal vaccine, survived the sepsis. The clinical course of a fulminant Streptococcus pneumoniae sepsis in both asplenic patients underlines the importance of vaccination. It is also important to educate the patient about seeking immediate medical help if an infection is suspected on the basis of these symptoms. Vaccination does not provide complete protection.

Acute Kidney Injury↗
PubMed2003

Expression of apoptosis-related proteins and morphological changes in a rat tumor model of human small cell lung cancer prior to and after treatment with radiotherapy, carboplatin, or combined treatment.

PURPOSE: In order to understand the apoptosis pathway in tumor cells, differences in cell morphology and expression of apoptosis-related proteins induced by radiation and/or chemotherapy, were investigated in a rat double tumor model comparing cisplatin-sensitive and -resistant human small cell lung cancer tumors. METHODS: The cisplatin-sensitive human small cell lung cancer cell line (GLC4) and its cisplatin-resistant subline (GLC4-CDDP) were each injected subcutaneously in a different hind limb of the rat. After 15-17 days, radiation (10 Gy), carboplatin (25 mg/kg, intraperitoneal), combined treatment, or no treatment was administered. In combined treatment, carboplatin was administered 24 h before radiation. Tumors were removed and fixed 72 h after carboplatin or 48 h after radiation. Paraffin-embedded slides were stained with hematoxylin/eosin for morphology. Expression of the apoptosis-related proteins p53, p21, Rb, bcl-2, bax, c-myc, Fas and Fas-L was assessed immunohistochemically. RESULTS: In the GLC4 tumor, carboplatin treatment increased tumor cell size, tumor cell size heterogeneity, and number of apoptotic tumor cells. After radiation and combined treatment, these changes were more pronounced and multinuclear giant cells were observed. In GLC4-CDDP tumors, minimal changes were detected after carboplatin. Following radiation slight increases in tumor cell size, tumor cell size heterogeneity and number of apoptotic tumor cells were observed. No multinuclear giant cells were seen. After combined treatment, GLC4-CDDP showed cellular changes comparable to those in GLC4 cells after radiation or combined treatment, but no giant cells were observed. Untreated, both tumors were equally positive for p53, bax, Fas, Fas-L, c-myc and negative for Rb. Contrary to GLC4, untreated GLC4-CDDP tumors showed no p21 and bcl-2 expression. After combined treatment, an increase in number of bcl-2 positive cells was found in GLC4-CDDP tumors. No p21 was induced in GLC4-CDDP by any treatment modality. In GLC4 tumors, p21 was induced by radiation alone. No further changes in protein expression were induced by any treatment in GLC4 tumors. CONCLUSION: Following therapy, morphological changes in cell size and cell size heterogeneity were more pronounced in GLC4 than in GLC4-CDDP tumors. However, morphological changes in GLC4-CCDP tumors after treatment indicate that carboplatin plus radiotherapy may be effective also in cisplatin resistant tumor cells. An increase in p21 in GLC4 after radiation might facilitate apoptosis. The increase in number of Bcl-2 positive cells after combined treatment and the consistently negative p21 status after any treatment in GLC4-CDDP may protect these tumor cells from apoptosis as a part of their resistance mechanism to cisplatin.

Animals↗
PubMed2003

Effects of multidose combination chemotherapy on the humoral immune system.

Patients receiving multidose combination chemotherapy are at risk for severe, life-threatening infections, caused by among others encapsulated bacteria like Streptococcus pneumoniae. The splenic marginal zone is essential in the initiation of immune responses to S. pneumoniae. We analyzed effects of multidose combination chemotherapy on B-cell subpopulations. Immune response capacity was evaluated by using Pneumovax (PPS) or Tetavax (TT) as antigenic challenge. Three days after finishing therapy, all B-cell subpopulations in bone marrow and spleen were severely reduced, including the mature marginal zone B-cell population. When analyzing the anti-PPS immune response capacity at 3 days after finishing therapy, we found that the IgM antibody levels did not differ significantly from control immunized rats. The IgG antibody levels were significantly lower compared to control immunized rats but still significantly higher compared to unimmunized rats. The depletion of marginal zone B cells by multidose combination chemotherapy most likely contributes to the prolonged period that patients are at risk for developing severe infections after chemotherapy, despite the capacity to generate sufficient antibody levels. It is conceivable that the local (temporary) loss of immunological memory, together with the supposed inability to generate a humoral response in a short time frame, plays an important role in this vulnerability.

Animals↗
PubMed2003

After chemotherapy, functional humoral response capacity is restored before complete restoration of lymphoid compartments.

Chemotherapy has, besides the beneficial effects, several adverse effects. Suppression of the immune system is one of the most important problems. Infections caused by encapsulated bacteria like Streptococcus pneumoniae are responsible for a major part of infectious problems during and after treatment. The splenic marginal zone is essential in the initiation of an immune response to encapsulated bacteria. In this study, we analysed the effects of three different cytostatic agents on humoral immune responses. We found a reduced, but detectable immune response capacity at two days after treatment although the marginal zone B cell population is severely reduced at this time point. Twenty-four days after cessation of treatment, the immune response capacity was largely restored although lymphoid compartments were still not completely restored at that time point. Apparently, the presence of only few marginal zone B cells is sufficient to evoke a rise in antibody titres and although antibody titre increases are low, even small rises are most likely clinically relevant.

Animals↗
PubMed2002

Superhydrophobic modification fails to improve the performance of small diameter expanded polytetrafluoroethylene vascular grafts.

To determine whether superhydrophobic modification of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts improves the performance of these grafts, we assessed neointima formation and platelet deposition in standard and superhydrophobic modified ePTFE grafts. Standard and superhydrophobic vascular grafts were implanted in the carotid arteries of two rabbits and two pigs. Furthermore, standard and superhydrophobic vascular patches were implanted in the carotid arteries of seven pigs. After 4 weeks of implantation all patches were removed and histomorphometric data were analyzed. The early thrombotic effect of superhydrophobic modification was examined by quantifying platelet glycoprotein receptor IIIa deposition onto each type of vascular graft after 15 min of in vitro circulation with human blood. All superhydrophobic and standard ePTFE vascular grafts occluded 15 min to 1 h after implantation in both rabbit and pig carotid arteries. All implanted patches remained patent and were completely covered by endothelium. Superhydrophobic modification of ePTFE vascular grafts did not lead to less neointima formation and resulted in significantly more platelet deposition than did standard ePTFE vascular grafts. Thus, superhydrophobic modification does not improve the performance of small diameter ePTFE vascular grafts.

Animals↗
PubMed2002

Quantification of oral mucositis due to radiotherapy by determining viability and maturation of epithelial cells.

BACKGROUND: An in-vitro assay has been developed for quantitative assessment of chemotherapy induced oral mucositis. In the present study this method was evaluated for assessment of irradiation mucositis at a cellular level. METHODS: Ten patients participated in this consecutive study. All patients were treated with conventional fractionated curative postoperative radiotherapy. Prior to, and weekly during, the irradiation course, oral washings were obtained to determine viability of epithelial cells by trypan blue dye exclusion. Maturation of epithelial cells was assessed from smears (Papanicolaou staining). The viability data were compared with the WHO-score for mucositis. RESULTS: Epithelial cell viability increased during the first three weeks of radiation (P = 0.04), and was seen earlier than the subjective mucosal changes with the WHO-score. Cell maturity shifted from immature and intermediate to mature (P = 0.03). CONCLUSIONS: The cell viability assay can be considered an objective method for following the development of irradiation mucositis, and seems to be more sensitive during the first three weeks of irradiation than the WHO-scoring method.

Adult↗
PubMed2002

The strength of the OVA-induced airway inflammation in rats is strain dependent.

To examine the influence of genetics on the OVA-induced allergic inflammatory response in lungs we compared rats that are genetically Th2-predisposed (Brown Norway, inbred) or not genetically predisposed (Sprague Dawley, outbred). Rats were sensitized with ovalbumin (OVA) and challenged four weeks later with OVA aerosol. Eighteen hours after challenge, lung tissue was studied for evaluation of numbers of eosinophils, neutrophils, macrophages and mast cells, as well as for expression of P-selectin, E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells. From a separate portion of the pulmonary tissue, leucocytes were isolated to analyse numbers of IFNgamma and IL-4 producing cells (ELISPOT assay) and frequencies of T-cell subsets and B cells. We found increased numbers of eosinophils and neutrophils in the lung, an increased number of IL-4 producing cells in lung cell isolates and increased levels of serum (OVA- specific)-IgE in both rat strains. In addition, expression of E-selectin and ICAM-1 was up regulated in both rat strains whereas expression of VCAM-1 was only up regulated in the BN rat. Although the 'allergic' Th2 response to OVA was detectable in both rat strains, it was more pronounced in the BN rat than in the SD rat. However, the SD rat, which is not predisposed to respond in either a Th2 or Th1-like way, appeared capable of mounting an allergic response to OVA. This suggests that other factors than genetic contribute to allergic disease.

Animals↗
PubMed2002

The dual function of the splenic marginal zone: essential for initiation of anti-TI-2 responses but also vital in the general first-line defense against blood-borne antigens.

The splenic marginal zone (S-MZ) is especially well equipped for rapid humoral responses and is unique in its ability to initiate an immune response to encapsulated bacteria (T-cell independent type 2 (TI-2) antigens). Because of the rapid spreading through the blood, infections with blood-borne bacteria form a major health risk. To cope with blood-borne antigens, a system is needed that can respond rapidly to a great diversity of organisms. Because of a number of unique features, S-MZ B cells can respond rapid and efficient to all sorts of blood-borne antigens. These unique features include a low blood flow microenvironment, low threshold for activation, high expression of complement receptor 2 (CR2, CD21) and multireactivity. Because of the unique high expression of CD21 in a low flow compartment, S-MZ B cells can bind and respond to TI-2 antigens even with relatively low-avid B cell receptors. Although TI-2 antigens are in general poorly opsonized by classic opsonins, a particular characteristic of these antigens is their ability to bind very rapidly to complement fragment C3d without the necessity of previous immunoglobulin binding. TI-2 primed S-MZ B cells, already by first passage through the germinal centre, will meet antigen-C3d complexes bound to follicular dendritic cells, allowing unique immediate isotype switching. This explains that the primary humoral response to TI-2 antigens is unique in its characterization by a rapid increase in IgM concurrent with IgG antibody levels.

Adult↗
PubMed2002

Multidrug resistance related molecules in human and murine lung.

AIMS: Transporter proteins known to mediate multidrug resistance (MDR) in tumour cells--MDR1 P-glycoprotein (P-gp) and multidrug resistance related protein 1 (MRP1)--are thought to be involved in protecting the lungs against inhaled toxic pollutants. Recently, several new transporter family members have been identified--for example, MRP2, MRP3, and breast cancer resistance protein (BCRP). To study the possible contribution of these proteins and the earlier defined MDR1 and MDR3 P-gp molecules, MRP1, and the major vault protein (MVP) to lung functioning, their expression was analysed in normal lung tissue of humans and several animal species. METHODS: Frozen sections of normal lung tissues were examined for the expression of the multidrug resistance associated proteins, using an extended panel of monoclonal antibodies that specifically detect these proteins in immunohistochemical techniques. RESULTS: In line with earlier reports, the expression of MDR1 P-gp and MRP1 was readily detected in the apical and basolateral membranes, respectively, of the epithelial cell layers of the lungs. In addition, prominent cytoplasmic MVP staining was detected in these layers. In contrast, the recently discovered transporters were either undetectable or they were present at very low values in lung tissue. Immunohistochemical staining in tissues from mice, rats, and guinea pigs points to a strong evolutionary conservation for these transporter proteins. CONCLUSIONS: These results show that the "classic" MDR related molecules, MDR1 P-gp, MRP1, and MVP, should be considered the most important transporters in normal lung physiology. It will be of great interest to investigate differences in expression of both classic and newly defined transporters between normal individuals and-for example, patients with various bronchopulmonary pathological conditions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Keratinocyte-derived growth factors play a role in the formation of hypertrophic scars.

In predisposed individuals, wound healing can lead to hypertrophic scar or keloid formation, characterized by an overabundant extracellular matrix. It has recently been shown that hypertrophic scars are accompanied by abnormal keratinocyte differentiation and proliferation, and significantly increased acanthosis, compared with normal scars. This study addressed the question of whether the development of normal and hypertrophic scars is regulated by differences in the growth factor profiles of both the epidermis and the dermis. The presence of interleukin-1alpha (IL-1alpha), IL-1beta, tumour necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) was investigated in biopsies taken from breast reduction scars at 3 and 12 months following surgery. The samples were analysed by immunohistological methods and categorized as scars that remained hypertrophic (HH), became normal (HN) or remained normal after 12 months (NN). The epidermal expression of IL-1alpha was significantly increased in NN scars compared with HN and HH scars 3 and 12 months following operation, whereas the dermal expression showed no difference. PDGF was significantly increased in the dermis of normal scars after 3 months and in both the epidermis and the dermis of hypertrophic scars after 12 months. IL-1beta, TNF-alpha, TGF-beta and bFGF showed no differences. It is hypothesized that impaired production of keratinocyte-derived growth factors, such as IL-1alpha, leads to a decrease in the catabolism of the dermal matrix, whereas augmented epidermal PDGF production leads to increased formation of the dermal matrix in hypertrophic scars. These observations support the possibility that the epidermis is involved in preventing the formation of hypertrophic scars.

Adolescent↗
PubMed2001

Tumor necrosis factor alpha (TNFalpha) in human skin: a comparison of different antibodies for immunohistochemistry.

Conflicting results have been reported regarding the localization and presence of TNFalpha in normal human skin. To study TNFalpha expression, we tested a panel of antibodies directed against human TNFalpha. First, antibodies were tested for immunoreactivity on cytospots of isolated LPS-stimulated peripheral blood mononuclear cells. Second, antibodies were tested to detect recombinant TNFalpha in Western blots. Some antibodies were found to be unable to detect recombinant TNFalpha in the blots. However, most antibodies were able to bind TNFalpha protein, but they did not bind to other irrelevant proteins that were also present in the blots. Finally, antibodies were tested on cryosections of normal human skin. Antibodies that did not react with TNFalpha in the blots were incubated with TNFalpha before the staining procedure to see whether these antibodies specifically bound TNFalpha. We found that, although all the antibodies bound TNFalpha, there were clear differences in staining patterns. This indicates that these antibodies may recognize distinct epitopes or different forms of TNFalpha. The differences found in this study and those reported previously could be the result of differences in the concentration of antibody used, the staining procedure or specificity of the antibody itself. So, for unambiguous interpretation of data, it is important to know the characteristics of the antibodies used.

Adolescent↗
PubMed2001

CD27 expression in the human splenic marginal zone: the infant marginal zone is populated by naive B cells.

The splenic marginal zone of adult humans contains B cells, of which most express CD27, an antigen only recently identified as a marker for somatically mutated memory B cells. We investigated whether and to which extent the developing marginal zone in infants and children is populated by either memory (CD27+) or naive (CD27-) B cells. Frozen sections of 32 spleens of infants and children ranging in age from 6 days to 15 years and 6 adult spleens were investigated. The expression of CD27 in combination with monoclonal antibodies against CD3, CD21, IgM, IgD and ASM-1 was analyzed by immunohistochemistry. The marginal zone was already present at 4 months after birth but CD21 expression was observed first after 2 years. CD27-positive marginal zone B cells were observed firstly 2 years after birth and increased in number to adult levels at the age of 5 years. We demonstrated that the MZ of infants and young children is populated by naive B cells, which are replaced by memory B cells in a time frame of 2 to 5 years. Before the age of 2 years, although present, memory B cells appear to be unable to colonize the marginal zone. Because of the absence of memory B cells in the marginal zone, the immune system of a child is not capable to initiate a rapid secondary humoral immune response comparable to the adult immune response.

Adolescent↗
PubMed2001

Slow recovery of follicular B cells and marginal zone B cells after chemotherapy: implications for humoral immunity.

Although most chemotherapeutic agents are known to cause primarily reduction or suppression of immune responses, surprisingly little is known about the influence of cytostatic agents on lymphoid tissue compartments such as the splenic marginal zone. The marginal zone plays an important role in the defence against encapsulated bacteria, which are potential candidates for postchemotherapeutic infections. We studied the effect of three different cytostatic agents (cisplatin, methotrexate, and cyclophosphamide) on B cell subpopulations in a rat model. Rats received a single dose of a single cytostatic agent and were sacrificed at different time points after treatment. Bone marrow, blood, mesenteric lymph nodes and spleens were analysed by flow-cytometry and immunohistochemistry. All three cytostatic agents showed severe bone marrow depression. CP and MTX showed only mild reduction of cell populations in the spleen. CyPh showed a severe reduction of recirculating follicular B (RF-B) cells and marginal zone B (MZ-B) cells. At day 24 most populations were already recovered, but RF-B cells and MZ-B cells were still reduced. The reduction of the marginal zone and late recovery may imply that, beside the overall increased infection risk due to neutropenia, patients treated with chemotherapy are at risk for developing infections from encapsulated bacteria for a considerable period of time after treatment, extending beyond the period of bone marrow depression.

Animals↗
PubMed2001

Inflammatory cell distribution in guinea pig airways and its relationship to airway reactivity.

Although airway inflammation and airway hyperreactivity are observed after allergen inhalation both in allergic humans and animals, little is known about the mechanisms by which inflammatory cells can contribute to allergen-induced airway hyperreactivity. To understand how inflammatory cell infiltration can contribute to airway hyperreactivity, the location of these cells within the airways may be crucial Using a guinea pig model of acute allergic asthma, we investigated the inflammatory cell infiltration in different airway compartments at 6 and 24 h (i.e. after the early and the late asthmatic reaction, respectively) after allergen or saline challenge in relation to changes in airway reactivity (AR) to histamine. At 6 h after allergen challenge, a threefold (p < 0.01) increase in the AR to histamine was observed. At 24 h after challenge, the AR to histamine was lower, but still significantly enhanced (1.6-fold, p < 0.05). Adventitial eosinophil and neutrophil numbers in both bronchi and bronchioli were significantly increased at 6 h post-allergen provocation as compared with saline (p < 0.01 for all), while there was a strong tendency to enhanced eosinophils in the bronchial submucosa at this time point (p = 0.08). At 24h after allergen challenge, the eosinophilic and neutrophilic cell infiltration was reduced. CD3+ T lymphocytes were increased in the adventitial compartment of the large airways (p < 0.05) and in the parenchyma (p < 0.05) at 24h post-allergen, while numbers of CD8+ cells did not differ from saline treatment at any time point post-provocation. The results indicate that, after allergen provocation, inflammatory cell numbers in the airways are mainly elevated in the adventitial compartment. The adventitial inflammation could be important for the development of allergen-induced airway hyperreactivity.

Animals↗
PubMed2001

Pneumococcal conjugate vaccines overcome splenic dependency of antibody response to pneumococcal polysaccharides.

Protection against infections with Streptococcus pneumoniae depends on the presence of antibodies against capsular polysaccharides that facilitate phagocytosis. Asplenic patients are at increased risk for pneumococcal infections, since both phagocytosis and the initiation of the antibody response to polysaccharides take place in the spleen. Therefore, vaccination with pneumococcal polysaccharide vaccines is recommended prior to splenectomy, which, as in the case of trauma, is not always feasible. We show that in rats, vaccination with a pneumococcal conjugate vaccine can induce good antibody responses even after splenectomy, particularly after a second dose. The spleen remains necessary for a fast, primary response to (blood-borne) polysaccharides, even when they are presented in a conjugated form. Coadministration of a conjugate vaccine with additional nonconjugated polysaccharides of other serotypes did not improve the response to the nonconjugated polysaccharides. We conclude that pneumococcal conjugate vaccines can be of value in protecting asplenic or hyposplenic patients against pneumococcal infections.

Animals↗
PubMed2000

Increased vascular expression of iNOS at day but not at night in asthmatic subjects with increased nocturnal airway obstruction.

Nitric oxide production by endothelial cells may have important consequences for the development of airway inflammation as well as for airway obstruction. The present study investigated whether the expression of vascular inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) in human bronchi differs between asthmatic and healthy subjects, and whether it shows a circadian rhythm, especially in subjects with increased nocturnal airway obstruction. Bronchial biopsy samples were taken at 16:00 and 04:00 h from 13 healthy and 25 asthmatic subjects, 18-45 yrs. Biopsy samples were snap-frozen and double-immunostained for iNOS and eNOS in combination with a common vascular antigen (CD31). The degree of immunopositivity was expressed as a percentage of CD31-positive vessels encountered in complete biopsy sections. Asthmatic subjects showed greater iNOS expression than healthy controls: 23+/-15 versus 7+/-17% (mean+/-SD) at 16:00 h (p<0.001) and 19+/-15 versus 8+/-11% at 04:00 h (p<0.05). Asthmatic subjects with a fall in forced expiratory volume in one second of >10% of the predicted value between 16:00 and 04:00 h showed greater iNOS expression at 16:00 than at 04:00 h: 32+/-16 versus 20+/-13% (p<0.05). eNOS expression did not differ between healthy controls and asthmatic patients, nor did it differ between 16:00 and 04:00 h. It is suggested that asthmatic subjects with increased nocturnal airway obstruction demonstrate increased activation of inducible nitric oxide synthase during the day. The resulting nitric oxide production might protect against airway obstruction during the day. However, at night, nitric oxide production is probably insufficient to counterbalance the bronchoconstricting forces.

Adolescent↗
PubMed2000

Visual symptoms after lung transplantation: a case of progressive multifocal leukoencephalopathy.

After solid organ transplantation, signs and symptoms of the central nervous system may present a diagnostic challenge. A 43-year-old patient developed a decrease in vision 15 months after bilateral lung transplantation. The initial diagnosis was a left posterior cataract, but left eye cataract extraction did not improve his vision. Seizures led to investigation of a broader differential diagnosis (cyclosporine intoxication, post-transplant lymphoproliferative disorder, infectious disease, chronic lymphatic leukemia). The clinical diagnosis of progressive multifocal leukoencephalopathy (PML) was confirmed by demonstration of JC virus in the cerebrospinal fluid and by autopsy findings. Modulation of the immunosuppressive regimen was unsuccessful. This case illustrates that decreased vision in immunocompromised patients may be the first manifestation of PML.

Adult↗