Bone ingrowth into porous silicon nitride

Achieving solid skeletal attachment is a requirement for the clinical success of orthopedic implants. Porous or roughened surfaces and coatings have been developed and used with mixed success to achieve attachment due to bone ingrowth. Silicon nitride is a high performance ceramic whose strength, imaging properties, and biocompatibility make it a candidate material for orthopedic implants. A porous form of silicon nitride, cancellous-structured ceramic (CSC), has been developed. CSC is a nonresorbable, partially radiolucent porous structure that can be bonded to orthopedic implants made of silicon nitride to facilitate skeletal attachment. The purpose of this study was to quantify the extent and rate of bone ingrowth into CSC in a large animal model. Cylindrical implants were placed bilaterally using staged surgeries in the medial femoral condyle of six sheep. Condyles were retrieved after 3 and 6 months in situ and prepared for examination of bone growth under SEM. Bone grew into CSC to extents and at rates similar to those reported for other titanium porous surfaces in studies involving large animals and postmortem retrievals in humans. Bone ingrowth was observed at depths of penetration greater than 3 mm in some implants after only 12 weeks in situ. Bone ingrowth into CSC is a viable method for achieving skeletal attachment.

Glomerular apoptotic nucleosomes are central target structures for nephritogenic antibodies in human SLE nephritis

Antibodies to double-stranded (dsDNA) are associated with systemic lupus erythematosus (SLE) and directly involved in human lupus nephritis. Information about their glomerular target antigens is inconsistent, and whether availability of target antigens, antibody specificity or avidity are nephritogenic parameters, is not determined. In this study, we analyzed renal tissue from anti-dsDNA antibody-positive lupus patients with nephritis by morphological and immunological assays, including immune electron microscopy (IEM) and colocalization IEM, an EM-based confocal microscopy assay. IEM demonstrated that antibody deposits were confined to electron dense structures (EDS) in glomerular membranes. These autoantibodies colocalized with nucleosome-binding anti-dsDNA/-histone/-transcription factor antibodies. To confirm the colocalization IEM-data, we developed a colocalization terminal deoxynucleotidyl-transferase (TdT) biotin-dUTP nicked end-labeled (TUNEL) IEM assay where extracellular DNA was traced by TdT-mediated introduction of biotinylated nucleotides and autoantibodies by IEM. Results consistently demonstrated that DNA colocalized with autoantibodies in glomerular membrane-associated EDS. The colocalization IEM and colocalization TUNEL IEM assays thus demonstrate that intra-glomerular membrane-associated nucleosomes are targeted by anti-dsDNA autoantibodies in human lupus nephritis. The data provide a new approach to understand basic molecular and immunological processes accounting for antibody-mediated nephritis in human SLE.

Cross shift changes in lung function among bar and restaurant workers before and after implementation of a smoking ban

OBJECTIVE

To study possible cross shift effects of environmental tobacco smoke (ETS) on pulmonary function among bar and restaurant employees before and after the implementation of a smoking ban in Norway.

METHODS

The study included 93 subjects employed in 13 different establishments in Oslo. They were examined at the beginning and end of a workshift both while ETS exposure was present and when smoking was banned. The mean exposure level of nicotine and total dust before the ban was 28 microg/m3 (range 3-65) and 275 microg/m3 (range 81-506), respectively. Following the smoking ban, the mean level of nicotine and total dust was 0.6 mug/m3 and 77 microg/m3, respectively. Assessment of lung function included dynamic lung volumes and flows.

RESULTS

The cross shift reduction in forced vital capacity (FVC) among 69 subjects participating in both examinations changed from 81 ml (SD 136) during exposure to ETS to 52 ml (SD 156) (p = 0.24) following the smoking ban. The reduction in forced expired volume in one second (FEV1) during a workshift, was borderline significantly reduced when comparing the situation before and after the intervention, by 89 ml (SD = 132) compared to 46 ml (SD = 152) (p = 0.09), respectively. The reduction in forced mid-expiratory flow rate (FEF25-75%) changed significantly from 199 ml/s (SD = 372) to 64 ml/s (SD = 307) (p = 0.01). Among 26 non-smokers and 11 asthmatics, the reduction in FEV1 and FEF25-75% was significantly larger during ETS exposure compared to after the smoking ban. There was an association between the dust concentration and decrease in FEF25-75% before the ban among non-smokers (p = 0.048).

CONCLUSIONS

This first study of cross shift changes before and after the implementation of a smoking ban in restaurants and bars shows a larger cross shift decrease in lung function before compared with after the implementation of the ban.

The genome of the social amoeba Dictyostelium discoideum

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

Advanced glycation end products impair the scavenger function of rat hepatic sinusoidal endothelial cells

AIMS/HYPOTHESIS

We have previously reported that advanced glycation end products are eliminated from the circulation mainly by scavenger receptor-mediated uptake in hepatic sinusoidal endothelial cells. Our experiments showed that the degradation of AGE-modified protein after endocytosis in hepatic sinusoidal endothelial cells occurs slowly compared with that of other scavenger receptor ligands. The aim of this study was to investigate further the mechanism whereby AGE-modified protein affects the important scavenger function of hepatic sinusoidal endothelial cells.

METHODS

Primary cultures of hepatic sinusoidal endothelial cells were pre-incubated with unlabelled ligand, unbound ligand was washed off, and the endocytic capacity was measured by addition of radiolabelled ligand, and immune electron microscopy.

RESULTS

Pre-incubation with unlabelled AGE-modified bovine serum albumin reduced subsequent endocytosis of radiolabelled scavenger receptor ligands AGE-modified bovine serum albumin, formaldehyde-treated serum albumin, oxidized low density lipoprotein and acetylated low density lipoprotein by 50, 56, 32 and 20%, respectively. Non-scavenger receptor-mediated endocytosis was not affected by pre-exposure to AGE-modified protein. Pre-incubation with a number of non-AGE-ligands did not affect subsequent endocytosis via any of the major endocytosis receptors in hepatic sinusoidal endothelial cells. Incubation in fresh medium for 6 h after pre-exposure to AGE-modified protein almost completely restored normal scavenger receptor-mediated endocytic activity. Quantitative immune electron microscopy showed that the amount of a newly described scavenger receptor for AGE-modified protein is reduced after pre-incubation with AGE-modified protein. Subcellular fractionation showed that pre-incubation with AGE-modified protein delays intracellular transport of scavenger receptor ligands.

CONCLUSION/INTERPRETATION

Endocytosis of AGE-modified protein leads to loss of scavenger receptors and delayed intracellular transport in hepatic sinusoidal endothelial cells.

The subcellular distribution of GABARAP and its ability to interact with NSF suggest a role for this protein in the intracellular transport of GABA(A) receptors

GABA(A) receptors the major sites of fast synaptic inhibition in the brain are composed predominately of alpha, beta, and gamma2 subunits. The receptor gamma2 subunit interacts with a 17-kDa microtubule associated protein GABARAP, but the significance of this interaction remains unknown. Here we demonstrate that GABARAP, which immunoprecipitates with GABA(A) receptors, is not found at significant levels within inhibitory synapses, but is enriched within the Golgi apparatus and postsynaptic cisternae. We also demonstrate that GABARAP binds directly to N-ethylmaleimide-sensitive factor (NSF), a protein critical for intracellular membrane trafficking events. NSF and GABARAP complexes could be detected in neurons and these two proteins also colocalize within intracellular membrane compartments. Together our observations suggest that GABARAP may play a role in intracellular GABA(A) receptor transport but not synaptic anchoring, via its ability to interact with NSF. GABARAP may therefore have an important role in the production of GABAergic synapses.

Dilemmas in the provision of own-home respite support for parents of young children with complex health care needs: evidence from an evaluation

Dilemmas in the provision of own-home respite support for parents of young children with complex health care needs: evidence from an evaluation Aims. The aim of this article is to present some of the results of a qualitative evaluation of a United Kingdom (UK) nurse-led, home-based, respite service for the families of children under the age of five with complex health care needs. Background. Advances in neonatal medical and nursing care have contributed to a growth in the number of children who survive low birth weight, birth trauma, and various congenital anomalies. Many of these children are likely to have long-term care needs which will require innovative nursing responses. Of particular importance is the need for parental respite, given the added demands of caring for very ill children at home. Methods. A parent-centred, follow-up evaluation, using in-depth qualitative interviews with parents in 18 families consecutively referred to the Children's Outreach Service between April and December 1997. Findings. This evaluation reveals the sometimes mixed reactions of parents to this innovative service, and the equivocal evidence about its role in contributing to family well-being. We discuss, from the perspective of parents using the service, some of the dilemmas and problems in the provision of home-based respite support to this client group. In particular, we explore the diverse ways in which families talk about their need for respite support and point to the need for flexibility in this kind of service provision if these support needs are to be met. Conclusion. We conclude by discussing the practice implications of our evaluation for those planning similar services.

The estimation of statistical parameters for local alignment score distributions

The distribution of optimal local alignment scores of random sequences plays a vital role in evaluating the statistical significance of sequence alignments. These scores can be well described by an extreme-value distribution. The distribution's parameters depend upon the scoring system employed and the random letter frequencies; in general they cannot be derived analytically, but must be estimated by curve fitting. For obtaining accurate parameter estimates, a form of the recently described 'island' method has several advantages. We describe this method in detail, and use it to investigate the functional dependence of these parameters on finite-length edge effects.

Altered cytokine and nitric oxide secretion in vitro by macrophages from diabetic type II-like db/db mice

Macrophage dysfunction is a likely mechanism underlying common diabetic complications such as increased susceptibility to infection, accelerated atherosclerosis, and disturbed wound healing. There are no available studies on the function of tissue macrophages in diabetes in humans. We have therefore studied peritoneal macrophages from diabetic type 2-like db/db mice. We found that the release of tumor necrosis factor-alpha and interleukin-1beta from lipopolysaccharide plus interferon-gamma-stimulated macrophages and vascular endothelial growth factor from both stimulated and nonstimulated macrophages was significantly reduced in diabetic animals compared with nondiabetic controls. Nitric oxide production from the stimulated db/db macrophages was significantly higher than that in the db/+ cultures, whereas there was no difference in their ability to generate reactive oxygen species. When studied both at light and electron microscopic levels, macrophages in diabetic animals had an altered morphological appearance compared with those of normal controls. We conclude that the function and morphology of the macrophages are disturbed in db/db mice and that this disturbance is related to the mechanisms underlying common inflammatory and degenerative manifestations in diabetes.

Microvascular perturbations in rats receiving the maximum tolerated dose of methotrexate or its major metabolite 7-hydroxymethotrexate

Methotrexate (MTX) is a clinically important cytostatic antifolate. The study describes the acute effects of maximum tolerated doses of MTX or its major metabolite 7-hydroxymethotrexate (7-OH-MTX) on the ultrastructure of rat liver and kidneys. The ultrastructural changes in rats receiving MTX or 7-OH-MTX were, in principle, indistinguishable and their severity and extension increased with time of survival or doses of medication. All lesions were focal, microvascular, or parenchymal. Microvascular changes were more severe in nature when blood cells were present. The endothelial cells were swollen with loss of pinocytotic vesicles, their luminal plasma membrane formed blebs or were disrupted. Partly detached endothelial cells or deendothelialized areas, various types of white blood cells, in particular, neutrophil granulocytes, were observed in the microcirculation. Single platelets or small platelet aggregates were found either in the lumen or adhering to deendothelialized areas of injured endothelial cells. Hepatocytes exhibited steatosis, edema, and manifest single cell necrosis. There were also nuclear changes, marked proliferation of smooth endoplasmatic reticulum, increased amounts of intracellular lipid vacuoles, and a decrease in glycogen particles in hepatocytes. The kidney presented the major changes in the tubules and in the interstitial part. MTX and 7-OH-MTX acute toxicity may primarily be related to microvascular perturbation.

Heparin induces synthesis and secretion of tissue factor pathway inhibitor from endothelial cells in vitro

TFPI is a potent inhibitor of the extrinsic coagulation system constitutively synthesized by endothelial cells. A major portion of intravascular TFPI is stored associated with endothelial cells. and administration of unfractionated heparin (UFH) in vivo causes a prompt mobilization of TFPI into the circulation. The present study was conducted to investigate how UFH affected the synthesis, secretion and anticoagulant potency of TFPI in endothelial cells in vitro. A spontaneously transformed immortal endothelial cell line was used (ECV304). Stimulation of ECV304 cells with UFH caused a prompt dose-dependent (0-5 IU UFH/ml) release of TFPI to the medium accompanied by no change of TFPI at the surface membrane assessed by immunocytochemical methods. Northern blot analysis revealed two mRNA transcripts for TFPI with a molecular size of 1.4 kb and 4.4 kb, respectively. Stimulation of ECV304 cells for 24 hrs with various concentrations of UFH caused a dose-dependent increase of TFPI in the medium (6.2-29.6 ng/10(6) cells within the concentration range 0-10 IU/ml). A similar dose-dependent increase in the expression of both TFPI mRNA species was observed. Long-term incubation of ECV304 cells with 5.0 IU/ml UFH caused a 5-10 fold increase in the TFPI concentration accumulated in the medium over 48 hrs. The increased TFPI mRNA expression induced by UFH appeared already after 10 min, peaked after 2-4 hrs, remained augmented throughout the entire period of UFH exposure, and preceded the synthesis-dependent increase in TFPI release by 2-4 hrs. The procoagulant activity of the cells was downregulated by 36% and the contribution of TFPI to the anticoagulant potency of ECV304 cells was moderately increased after 24 hrs heparin stimulation. It is suggested that these mechanisms are of major importance for the anticoagulant function of heparins.

Rapid assessment of extremal statistics for gapped local alignment

The statistical significance of gapped local alignments is characterized by analyzing the extremal statistics of the scores obtained from the alignment of random amino acid sequences. By identifying a complete set of linked clusters, "islands," we devise a method which accurately predicts the extremal score statistics by using only one to a few pairwise alignments. The success of our method relies crucially on the link between the statistics of island scores and extremal score statistics. This link is motivated by heuristic arguments, and firmly established by extensive numerical simulations for a variety of scoring parameter settings and sequence lengths. Our approach is several orders of magnitude faster than the widely used shuffling method, since island counting is trivially incorporated into the basic Smith-Waterman alignment algorithm with minimal computational cost, and all islands are counted in a single alignment. The availability of a rapid and accurate significance estimation method gives one the flexibility to fine tune scoring parameters to detect weakly homologous sequences and obtain optimal alignment fidelity.

Subunit-specific association of protein kinase C and the receptor for activated C kinase with GABA type A receptors

GABA receptors (GABA(A)) are the major sites of fast synaptic inhibition in the brain and can be assembled from five subunit classes: alpha, beta, gamma, delta, and epsilon. Receptor function can be regulated by direct phosphorylation of beta and gamma2 subunits, but how kinases are targeted to GABA(A) receptors is unknown. Here we show that protein kinase C-betaII (PKC-betaII) is capable of directly binding to the intracellular domain of the receptor beta1 and beta3 subunits, but not to those of the alpha1 or gamma2 subunits. Moreover, associating PKC-betaII is capable of specifically phosphorylating serine 409 in beta1 subunit and serines 408/409 within the beta3 subunit, key residues for modulating GABA(A) receptor function. The receptor for activated C kinase (RACK-1) was found also to bind to the beta1 subunit intracellular domain, but PKC binding appeared to be independent of this protein. Using immunoprecipitation, the association of PKC isoforms and RACK-1 with neuronal GABA(A) receptors was seen. Furthermore, PKC isoforms associating with neuronal receptors were capable of phosphorylating the receptor beta3 subunit. Together, these observations suggest GABA(A) receptors are intimately associated with PKC isoforms via a direct interaction with receptor beta subunits. This interaction may serve to localize PKC activity to GABA(A) receptors in neurons allowing the rapid regulation of receptor activity by cell-signaling pathways that modify PKC activity.

Biochemical analysis of mouse FKBP60, a novel member of the FKPB family

We have identified mouse and human FKBP60, a new member of the FKBP gene family. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contains a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/trans isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 cells suggests that FKBP60 is segregated to the endoplasmic reticulum. Northern blot analysis shows that FKBP60 is predominantly expressed in heart, skeletal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate effectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca2+ in vitro, presumably by its C-terminal EF-hand Ca2+ binding motif, and is phosphorylated in vivo. hFKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridization (FISH).

Endothelial injury and trapping of blood cells in human myocardium following coronary bypass surgery

To investigate the focal myocytic and microvascular injury that develops during the first hour of reperfusion after hypothermic cardioplegic cardiac arrest, and to compare the influence of gentle versus more abrupt reperfusion, serial atrial biopsies were obtained from 14 patients undergoing uneventful coronary bypass surgery. The biopsies were taken before cardioplegia, at the start of reperfusion, and after 20 and 60 min of reperfusion. Transmission electron micrographs of biopsies examined by stereological techniques revealed endothelial injury. Following 20 min reperfusion there was accumulation of both red blood cells (p = 0.03) and polymorphonuclear leucocytes (p = 0.0004) were found. There was also intravascular accumulation of platelets (p = 0.008) and extravasation of red blood cells (p = 0.02), which increased throughout the observation period. If reperfusion was started with a gradual rise in temperature and pressure, the numbers of platelets in the microvessels were lower than following ordinary, abrupt reperfusion (p = 0.06). It is concluded that reperfusion injury is associated with microcirculatory disturbances with trapping of blood cells, changes which may be favourably modified by a gentle reperfusion technique.

Optimizing Smith-Waterman alignments

Mutual correlation between segments of DNA or protein sequences can be detected by Smith-Waterman local alignments. We present a statistical analysis of alignment of such sequences, based on a recent scaling theory. A new fidelity measure is introduced and shown to capture the significance of the local alignment, i.e., the extent to which the correlated subsequences are correctly identified. It is demonstrated how the fidelity may be optimized in the space of penalty parameters using only the alignment score data of a single sequence pair.

Transport of residual endocytosed products into terminal lysosomes occurs slowly in rat liver endothelial cells

Receptor-mediated endocytosis of circulating collagen is a major physiological scavenger function of the liver endothelial cell and an important catabolic event in the complete turnover of this abundant connective tissue protein. In the present study, transport of collagen through the endocytic pathway was investigated in cultured liver endothelial cells. Collagen conjugated to fluorescein isothiocyanate, to allow detection of the ligand by fluorescence and immunoelectron microscopy, was found sequentially in three different organelles that compose the basic degradative endocytic pathway of eukaryotic cells: early endosomes, late endosomes, and terminal lysosomes. Early endosomes were identified as vesicles positive for early endosome antigen 1 (EEA1). Late endosomes were distinguished as structures positive for the late endosomal/lysosomal marker rat lysosomal membrane glycoprotein 120, but negative for EEA1 and lysosomally targeted BSA-gold. Lysosomes were defined by their content of BSA-gold, injected 24 hours before isolation of cells. Coated pits and coated vesicles mediated an extremely rapid internalization. Shortly after internalization and during the first 20 minutes, ligand was found in early endosomes. From 20 minutes on, ligand started to appear in late endosomes (23%), and by 2 hours the transfer was largely complete (82.5%). Only 2.5% of ligand was transferred to the lysosomes after 2 hours, and this number slowly increased to 21% and 53% after 6 and 16 hours, respectively. We conclude that 1) EEA1 is a useful marker for tracing early events of endocytosis in liver endothelial cells; 2) in contrast to the rapid internalization, transit of internalized ligand through early sorting endosomes generally takes from 20 minutes to 2 hours; and 3) exit from the late endosomes is very slow, requiring several hours.

Adoptive immunotherapy of feline leukemia virus infection using autologous lymph node lymphocytes

Adoptive immunotherapy using autologous cells expanded ex vivo from lymph nodes was examined in cats infected with the retrovirus feline leukemia virus (FeLV). Cells were obtained from popliteal lymph nodes from 18 FeLV-antigen-positive cats without complications; a mean of 6.2 x 10(7) cells were obtained. Lymph node cells were cultured with 600 IU/ml interleukin-2 (IL-2) for 7 days. Cells expanded 0.8- to 11-fold (mean, 2.7; median, 2.4); were 80% +/- 8.0% CD3+, 29% +/- 8.1% CD4+, and 41% +/- 7.0% CD8+, and exhibited cytolytic activity against FeLV-transformed FL74 cells. Sixteen cats received a single intravenous infusion of 0.13 to 3.9 x 10(8) cells. Cell infusion was well tolerated; fever developed approximately 1 hour postinfusion. Clinical activity, antiviral activity, or both was observed in 10 cats. Nine cats had clinical responses with improvement in weight, activity, appearance, or a combination of these that began 2 to 4 weeks after cell infusion and that lasted for up to 13 or more months. FeLV antigen became undetectable in 4 cats. These results indicate that adoptive immunotherapy using autologous lymph node cells, activated and expanded ex vivo in short-term cultures with low concentrations of IL-2, can modulate the course of a retroviral infection.

More hassle, more alone: adolescents with diabetes and the role of formal and informal support

Informal support is a vital part of diabetes care, for adolescents in particular. However, we have a poor appreciation of how adolescents characterize informal support relationships, and how they change over time. This article is based on qualitative, in-depth interviews and focus groups with 21 adolescents (14-19 years old) in Leicestershire. We studied the content and substance of relationships between adolescents with diabetes and their families and friends, how they change and develop over time, and how they interact with formal support from health professionals. We identify a key problem--progressive independence from family life and progressive withdrawal of formal health service input leaves some older adolescents feeling isolated, with possible implications for likely maintenance of contact with routine services.

Association of tissue factor pathway inhibitor with human umbilical vein endothelial cells

Tissue factor pathway inhibitor (TFPI) is a serine protease inhibitor of the extrinsic coagulation system, synthesized in endothelial cells, which has recently been shown to play an important role in the regulation of activated coagulation factors at the endothelial cell surface. In the present study we investigated the subcellular localization and metabolism of TFPI in human umbilical vein endothelial cells (HUVEC). Immunocytochemical labeling of HUVEC with anti-TFPI showed specific labeling associated with the cell surface and with many intracellular organelles including the Golgi complex. Further characterization of these organelles was performed by colocalizing the anti-TFPI with 3-(2, 4-dinitroanilino)'-amino-N-methyldipropylamine (DAMP; to demonstrate low pH), mannose phosphate receptor (endosomes), and LAMP 1 (late endocytic compartments). TFPI also colocalized with antibodies to the human transferrin receptor, a marker for early endocytic, recycling compartment. Endogenous TFPI colocalized with biotin in intracellular vesicles during endocytosis after biotinylation of the cell surface, which indicated that TFPI was being co-internalized with the surface biotin. The binding of exogenously added 125I-TFPI increased linearly to HUVEC over the concentration range of 0 to 32 nmol/L without saturation, the binding was not affected by up to a thousand-fold molar excess of unlabeled TFPI, and heparin inhibited the binding dose dependently. An intact C-terminal domain was important for the interaction between TFPI and the cell surface of HUVEC, because less than 10% of a C-terminal truncated form of TFPI (TFPI1-161) was bound after addition of equimolar concentrations of full-length TFPI. Exogenously added 125I-TFPI was not degraded in HUVEC during 4 hours at 37 degrees C. The presence of TFPI in endocytic and recycling compartments support the hypothesis that endogenous, membrane-anchored TFPI could be internalized for subsequent recycling back to the cell surface.

Cytotoxic effect of cytokines on murine colon carcinoma cells involves TNF-mediated apoptosis

We have studied the cytotoxic effect of TNF-alpha on C-26 murine colon carcinoma cells in vitro. Treatment with TNF-alpha alone did not result in any demonstrable cytotoxicity. However, when combined with IFN-gamma, the cytotoxic effect of TNF-alpha was enhanced in a dose-dependent manner. An agonistic TNF-R1 specific antibody and recombinant human TNF-alpha both exerted a cytotoxic effect when combined with IFN-gamma, suggesting that the cytotoxicity was mediated through the TNF-R1. The cytotoxicity was associated with production of nitric oxide without any direct involvement in the cytotoxic effect. At the ultrastructural level, treated cells displayed a typical apoptotic morphology which was not accompanied by internucleosomal cleavage of DNA as shown by conventional electrophoresis.

In situ localization of Streptococcus pyogenes during acute tonsillitis: an immunocytochemical study with gold markers

Epithelial cells were harvested from the surface of the palatine tonsils of seven patients with current acute tonsillitis, proven culture-positive for Streptococcus pyogenes. The epithelial cells harboured attached bacteria, which expressed positive affinity to gold-labelled antiserum to S. pyogenes. The gold particles adhered selectively to the bacterial capsules. The microorganisms were held in place by projections protruding from the epithelial cells, which were in close contact with the pili of the bacteria. In some areas, positive immunogold-labelled bacteria intermingled with bacteria lacking such labelling. None of the culture-negative controls harboured epithelial cells with positive immunogold-labelled bacteria. Orally administered phenoxymethylpenicillin caused a significant reduction in both culture-positive S. pyogenes and bacteria displaying positive coating with specific gold-labelled antiserum to S. pyogenes.