The role of cartilage canals in endochondral and perichondral bone formation: are there similarities between these two processes?

We investigated the development of cartilage canals to clarify their function in the process of bone formation. Cartilage canals are tubes containing vessels that are found in the hyaline cartilage prior to the formation of a secondary ossification centre (SOC). Their exact role is still controversial and it is unclear whether they contribute to endochondral bone formation when an SOC appears. We examined the cartilage canals of the chicken femur in different developmental stages (E20, D2, 5, 7, 8, 10 and 13). To obtain a detailed picture of the cellular and molecular events within and around the canals the femur was investigated by means of three-dimensional reconstruction, light microscopy, electron microscopy, histochemistry and immunohistochemistry [vascular endothelial growth factor (VEGF), type I and II collagen]. An SOC was visible for the first time on the last embryonic day (E20). Cartilage canals were an extension of the vascularized perichondrium and its mesenchymal stem cell layers into the hyaline cartilage. The canals formed a complex network within the epiphysis and some of them penetrated into the SOC were they ended blind. The growth of the canals into the SOC was promoted by VEGF. As the development progressed the SOC increased in size and adjacent canals were incorporated into it. The canals contained chondroclasts, which opened the lacunae of hypertrophic chondrocytes, and this was followed by invasion of mesenchymal cells into the empty lacunae and formation of an osteoid layer. In older stages this layer mineralized and increased in thickness by addition of further cells. Outside the SOC cartilage canals are surrounded by osteoid, which is formed by the process of perichondral bone formation. We conclude that cartilage canals contribute to both perichondral and endochondral bone formation and that osteoblasts have the same origin in both processes.     

Functional histology of the human thymus

Summary The thymus develops from a paired epithelial anlage in the neck. This review considers how ectoderm (vesicula cervicalis) and endoderm (third pharyngeal pouch) contribute to the epithelial stroma of the thymus. Stromal elements of mesodermal origin are capillaries, septae and perivascular spaces and single invading cells. These elements separate the thymus into pseudolobuli. The thymus epithelial space and the perivascular spaces are always separated from each other by a closed, flat epithelial cell layer, with a basal lamina which contributes to the blood-thymus barrier. From the 9th gestational week, prethymic precursor cells from hemopoietic centers, begin to invade the thymus anlage. There they finally mature to committed post-thymic T cells. The thymus microenvironment of postnatal thymus is composed of six different types of epithelial cells and several stromal cells of mesodermal origin. The location of these diverse stationary cells is described, and their functional significance is discussed. Obviously these stromal cell types have a special function in providing the proper environment for T-cell maturation. The function of the thymus includes the maturation and/or selection of antigen specific T-cells. The main issue of intra-thymic T-cell differentiation is the development and expression of T-cell-antigen receptors. The great diversity of these receptors is generated by a rearrangement of the T-cell-receptor-genes in order to furnish the host with a mature T-cell repertoire that is capable of recognizing the world of extrinsic antigens. In a synopsis the manyfold interrelationships between the thymus microenvironment and the developing thymocytes are summarised.Abbreviations BALT Bronchus Associated Lymphoid Tissue - CD Cluster of Differentiation - cCD3 cytoplasmic CD3 - mCD3 membranous CD3 - C.R. Crown Rump - GALT Gut Associated Lymphoid Tissue - HLA Human Leucocyte antigen - HLA-DR Gene product of the MHC-class II (this antigen is a surface molecule of numerous stationary and free cells of the immune system) - IDC Interdigitating Cell - IL1 Interleukin 1 (cytokine derived mainly from makrophages, but also from other cell types) - IL2 and IL4 Interleukin 2 and 4 (cytokines derived mainly from T-cell, but also from other cell types) - IL4R Interleukin 4-Receptor - Mab Monoclonal antibody - MHC Major Histocompatibility Complex - p.c. post conception - TCR T-Cell-Receptor - TNC Thymic Nurse Cell - TdT Terminal deoxynucleotidyl Transferase     

Immunoglobulin E suppression and cytokine modulation in mice orally tolerized to beta-lactoglobulin

This study was designed to confirm the tolerogenic properties of beta-lactoglobulin in a mouse model and to assess specific oral tolerance induction in humoral and cellular compartments. BALB/c mice were fed beta-lactoglobulin (BLG) or whey proteins at different ages and subsequently intraperitoneally challenged 5 days later with both BLG and a non-specific antigen, ovalbumin (OVA). Three weeks later, oral tolerance induction was analysed in CMP-fed, versus saline-fed mice, by measuring specific seric and intestinal antibody responses, delayed-type hypersensitivity (DTH), specific splenocyte proliferation, and cytokine secretion patterns. Three-week-old mice fed high doses of either whey proteins or BLG (respectively 3 mg/g or 5 mg/g of body weight) were found to achieve oral tolerization. At humoral and mucosal levels, anti-BLG immunoglobulin E (IgE) were suppressed in these groups when compared with saline fed mice. With respect to cellular responses, systemic DTH and lymphocyte proliferation to BLG were also inhibited in CMP-fed mice. Weaning time was determined to be the best period for oral tolerance induction. Kinetic analyses showed however, that a minimum of 2 weeks was required for oral tolerance detection. Finally, cytokine profiles indicated a reciprocal decrease of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) versus an increase of IL-10 and transforming growth factor-beta (TGF-beta) secretions in tolerized mice. Taken together, these results clearly showed that oral administration of high doses of cows' milk proteins can induce significant hyposensitization in mice, in a specific inhibition of T helper 1 (Th1) lymphocytes with the participation of suppressor cytokines.     

Comparison of Western blot (immunoblot) based on recombinant-derived p41 with conventional tests for serodiagnosis of human immunodeficiency virus infections.

To evaluate the performance of a serological test for human immunodeficiency virus type 1 (HIV-1) infections based on the use of a recombinant envelope gene-derived protein as the antigen, we caused expression of a 1.4-kilobase fragment of HIV.DNA that codes for the complete gp41 transmembrane protein in an Escherichia coli expression vector and used Western blots (WB; immunoblots) prepared with recombinant material (pEX-41) to detect antibodies to HIV-1. This test detected all 339 sera which were positive by a combination of conventional serodiagnostic assays and produced no false-positive results with 311 negative samples. Also no false-positive results were obtained with 20 sera from systemic lupus erythematosus patients which had high titers of cross-reactive autoantibodies. In six cases, the pEX-41 WB proved to be more sensitive than individual assays applied on their own, and in five cases it was even more sensitive than a combination of conventional assays. We tested 221 sera in both our pEX-41 WB and a commercially available recombinant enzyme immunoassay (EIA [Abbott]). The results were identical in 188 cases. A total of 27 sera containing antibodies to gp41 as demonstrated in the pEX-41 WB, as well as the Abbott recombinant EIA, had no antibodies to the recombinant core antigen as measured in the Abbott EIA. However, 25 of these sera did stain the 24-kilodalton band on a WB with purified virus. Six sera that were positive in all of the conventional confirmatory assays and reacted strongly with the pEX-41 WB did not recognize the surface antigen used in the Abbott recombinant EIA. We conclude that the use of WB prepared with recombinant-derived p41 offers a very sensitive and specific method to detect antibodies to HIV.     

Genetic and genetic expression analyses of clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) represents a significant diagnostic and clinical challenge. In search of diagnostically useful or biologically significant genetic abnormalities, we screened 30 CCSKs from the National Wilms Tumor Study Group. Genetic gains and losses were analyzed using comparative genomic hybridization; loss of heterozygosity at 11p15 was studied using microsatellite analysis. Loss of imprinting (LOI) was studied using allele-specific expression or methylation analysis at the ApaI polymorphic site for IGF2, AluI and RsaI sites for H19, and Cfo I site for SNRPN. Comparative genomic hybridization analysis revealed quantitative abnormalities in only 4 of 30 CCSKs. Two showed gain of 1q, one also showed loss of 10q, and the other also showed loss of terminal 4p. The other two cases demonstrated chromosome 19 loss and chromosome 19p gain, respectively. All 22 cases informative for 11p15 showed retention of both alleles. Of 14 CCSKs informative for IGF2, six showed biallelic expression; all three CCSKs informative for H19 exhibited monoallelic expression. The normal imprint pattern was present in all six CCSKs analyzed for SNRPN methylation. These data demonstrate an absence of consistent genetic gains or losses in CCSKs using these methods. The high frequency of LOI for IGF2 in CCSKs (43%) is comparable to that reported in Wilms tumors. The retention of imprinting at the SNRPN and H19 loci confirm that LOI is not a ubiquitous epigenetic change. This suggests that IGF2, a potent growth factor, may play a role in the development or progression of CCSK.     

Unusual uses of liquid perfluorocarbons]

Since the use of low viscosity perfluorocarbon liquids by Chang in 1987, many applications in vitreoretinal surgery have become possible owing to their physical properties (density, viscosity and refraction index). Perfluorocarbon liquids are used exclusively when a vitrectomy is necessary. The main indications are drainage of subretinal fluid by peripheral dehiscence, to facilitate dissection of vitreo retinal proliferation, in retinal detachment by giant tear and in posterior lens dislocation. The authors report three cases illustrating two new indications for perfluorocarbon liquids. Confirming the presence or absence of a peripheral dehiscence in a total retinal detachment if vitrectomy is necessary, subretinal fluid is displaced and escapes via a possible dehiscence. Treatment of vitreretinal incarcerations in a sclerotomic orifice during a vitrectomy is simplified. Easier treatment of this complication is made possible by the injection of perfluorocarbon liquids into the "non-incarcerated" orifice. Despite the more frequent use of perfluorocarbon liquids in vitreoretinal surgery, the possible specific complications which may occur with these products mean that they should be used with caution.     

Primary lumbosacral stability after open posterior and endoscopic anterior fusion with interbody implants: a roentgen stereophotogrammetric analysis

STUDY DESIGN: After posterior stabilization of the spondylolytic lumbosacral level, mobility of the fused vertebrae could be studied before and after an additional anterior endoscopic interbody fusion using roentgen stereophotogrammetric analysis. OBJECTIVE: To determine the in vivo primary lumbosacral stability of additional anterior interbody fusion after transpedicular screw fixation. SUMMARY OF BACKGROUND DATA: In vitro studies indicate a significant decrease in segmental motion after pedicle screw fixation and additional anterior fusion. Roentgen stereophotogrammetric studies demonstrate the adequacy of transpedicular lumbar instrumentation in posterolateral fusions. There are no studies examining the effect of additional anterior interbody fusion after posterior instrumentation in vivo. METHODS: In this study, 15 patients with low-grade spondylolisthesis at L5-S1 underwent a two-stage open posterior and endoscopic anterior lumbar fusion using carbon fiber (Brantigan I/F) cages. At surgery, tantalum markers were implanted into the fifth lumbar (L5) and the first sacral (S1) vertebra. All the patients were examined by roentgen stereophotogrammetric analysis after the first and second surgical procedures. RESULTS: After implantation of the posterior pedicle system only, the mean intervertebral mobility determined by roentgen stereophotogrammetric analysis was 0.23 mm in the transverse (x), 0.54 mm in the vertical (y), and 1.2 mm in the sagittal (z) axes. After additional anterior endoscopic fusion with carbon cages, the remaining translation between the fused segment L5/S1 decreased to 0.17 mm in the x, 0.16 mm in the y, and 0.44 mm in the z axes. CONCLUSION: Anterior endoscopic lumbosacral fusion significantly increases the primary stability of the posterior fusion with a pedicle system in two axes of motion.