T cell developmental defects in 'viable motheaten' mice deficient in SHP-1 protein-tyrosine phosphatase. Developmental defects are corrected in vitro in the presence of normal hematopoietic-origin stromal cells and in vivo by exogenous IL-7

Defects in the gene that encodes SHP-1 protein tyrosine phosphatase result in multiple hematopoietic abnormalities and generalized autoimmunity in viable motheaten (me(v)) mice. These mice also exhibit early thymic involution and abnormalities in T cell development. Here, we describe the use of fetal thymic organ culture (FTOC) and bone marrow adoptive transfer to study the effects of SHP-1 deficiency on thymocyte development. Chimeric FTOC established with normal bone marrow placed onto deoxyguanosine-treated fetal thymic lobes or onto scid fetal thymic lobes generated T cells. Bone marrow from SHP-1-deficient me(v)/ me(v) mice generated decreased numbers of T cells in chimeric FTOC established using deoxyguanosine-treated thymi but generated normal numbers in chimeric FTOC established using scid thymi. However, scid fetal thymi seeded with me(v)/ me(v) bone marrow also exhibited morphological abnormalities and contained elevated numbers of macrophages. Addition of IL-7 to me(v)/ me(v) bone marrow-seeded scid FTOC led to increased cell numbers, particularly of macrophages. Intrathymic injection of IL-7 partially restored the ability of progenitor cells in me(v)/ me(v) bone marrow to populate the thymus of adoptive recipients. We conclude that abnormal T cell development in me(v)/ me(v) mice may in part be due to defects in the ability of bone marrow-derived accessory cells to provide bioavailable IL-7 to developing thymocytes.     

Cytogenetics as an aid in the diagnosis of lymphomas

Multiple classifications of lymphomas are available. Generally, distinctions are made to identify low, intermediate, and high-risk groups. Histopathologic differentiation is at times difficult. The revised European-American lymphoma classification (REAL) uses histology, clusters of differentiation markers, histochemistry, and cytogenetics for definitive identification. This work reviews the karyotypic and FISH (fluorescent in situ hybridization) findings in some common lymphomas. B-Cell lymphomas, which make up approximately 85-90% of lymphomas, are associated with cytogenetic changes of +12, 13q14, 14q32, 2p11, and 22q13. Translocations help to support the diagnosis of follicular cell lymphoma t(14;18),(q32;q21), mantle cell lymphoma t(11;14)(q13;q32), and Burkitt's lymphoma t(2;8),t(8;14) and t(8;22). T-Cell lymphomas may show changes in 14q11,7p or 7q. Many of the lymphomas are characterized by complex karyotypic changes. Specific FISH probes are useful in determining characteristic or identifying marker chromosomes. Cytogenetic and FISH studies aid in the diagnosis, correct classification, and evaluation of therapy for a variety of lymphomas.     

Collared crypts in irradiated small intestine

Crypts of Lieberkuhn are radiosensitive: the technique of crypt counting is an established method of assessing radiation induced changes in the small intestine. However, there has been little work done on the surface contours of the crypts, as they open into the intervillous cleft. The current paper describes the structure of control mouse crypt mouths as unobtrusive openings approximately 5 microns in diameter. After radiation with heavy ion particles, the crypt mouths are substantially larger (up to 10 microns in diameter) with a marked collar which is similar to that sometimes seen in coeliac disease. The shape and incidence of the collared crypts is described for specimens irradiated with neon, silicon and iron ions, with treatment with iron producing the most marked collars: it is suggested that the size and incidence of the collared crypts may be related to the LET of the beam used. It is of interest that the abnormal crypts are not produced after single doses of X-irradiation. The consideration of the structure of the collared crypts may require a redefinition of the terms crypt and villus with priority being given to the position of subepithelial vessels rather than surface shape. Finally, although the collared crypts can not be directly equated with 'tunnel' or 'channel' lesions, it is pointed out that they do represent localised damage with a specific position and shape.     

Continuing education for general practice and the role of the pharmaceutical industry.

A survey of the involvement in and attitudes towards continuing medical education of 101 general practitioners achieved a 95% response rate. Ninety per cent of the 96 doctors worked in practices which held meetings the content of which was organized by representatives of pharmaceutical companies but only 46% worked in practices which organized their own educational meetings. Seventy six per cent attended meetings away from their practice which were organized by drug companies and 75% had attended at some time continuing medical education activities organized by a local postgraduate centre. The promotional aspects of the drug company organized meetings were disliked by a majority of respondents (58%); more of the trainers (62%) and more of those who had entered general practice within the last seven years (71%) disliked this aspect. Nonetheless the educational content of both meetings held in the practice and those held elsewhere was the aspect most liked by over half of the respondents (59% and 53% respectively). Only 16% of all respondents thought that visits by representatives from pharmaceutical companies were educationally valuable and 37% thought that educational events organized by these companies were of value. Surprisingly 60% of those who worked in practices which held meetings organized by drug company representatives thought them to be of little or no educational value. There is clearly a need for practice based continuing medical education but the current level of dependence on drug companies for organizing these meetings must be questioned. Alternative strategies for the provision of independent non-sponsored educational activities should be sought.     

Characterization of murine monoclonal antibodies to Escherichia coli J5.

Results show that various inbred strains of mice can be segregated into two distinct groups, based on their capacity to allow a number of nontuberculous mycobacterial infections to grow in target organs following experimental intravenous infection. The first group, which allowed these infections to grow progressively, was thus designated as naturally susceptible to these infections; in contrast, those strains which were able to exert detectable bacteriostasis were designated as naturally resistant. It was then found that segregation of mouse strains based on this distinction also mirrored the capacity of these animals to generate acquired immunity to the mycobacterial infections. For example, Mycobacterium simiae grew progressively in susceptible C57BL/6 mice, subsequently triggering acquired mechanisms of immunity, whereas no evidence for acquired immunity could be found in resistant A/Tru mice infected with this organism. The possibility that acquired immunity could not be expressed in the latter strain as a result of a defect in macrophage activation was excluded. Moreover, it was found that the trait of resistance to these infections could be transferred by bone marrow cells into radiation chimeras, thus indicating that this trait was expressed by the progeny of hemopoietic precursor cells. Subsequent backcross analysis to determine the mode of inheritance of the trait of resistance to these mycobacterial infections revealed data that were consistent with the hypothesis that this resistance is controlled by more than one gene. Statistical analysis of the data by the maximum likelihood method suggested polygenic control, although in some cases the probability values suggested control by a major gene, influenced by modifier genes. These findings suggest that the previous hypothesis that the growth of mycobacterial infections in inbred strains of mice is controlled by a single gene should be reevaluated.     

Laser ablation of discs of agar gel

Discs of agar gel mixed with ink were used to study ablation effects with an argon laser as a light source. Varying amounts of ink were added resulting in a variation of the attenuation coefficient between 0.45 and 6.3 mm-1. For laser beam irradiation horizontally incident on a vertical sample, the average velocity of ablation was found to be approximately constant for thicknesses up to 1.7 mm. When the laser beam was directed vertically on a sample held horizontally, the vaporized debris present in the beam attenuated the incident laser energy to such a degree that the average ablation velocity decreased by a factor of approximately five. Horizontal beam experiments for various attenuation coefficients showed that an attenuation coefficient of about 1.7 mm-1 is optimal for fast penetration of discs thicker than 4 mm. Thus, based upon the optical properties of a given tissue, there may exist an optimum laser wavelength to maximise ablation velocity.     

In vivo histologic and biomechanical characterization of a biodegradable particulate composite bone cement

A biodegradable particulate composite bone cement consisting of a crosslinked gelatin matrix and tricalcium phosphate particles was implanted intraosseously in rabbits for up to 12 weeks. Cured cylindrical implants were inserted in holes drilled in the proximal tibial metaphysis. Sequential fluorochrome labeling and radiographs were done, and specimens were processed for decalcified and nondecalcified histology. At 4 weeks, the cross-sectional diameter of the implant was slightly greater than at implantation. There was considerable dissolution of the matrix and some new bone ingrowth. At 12 weeks, the diameter was reduced to half the original diameter and bone had grown throughout the matrix. In the distal femur, freshly mixed cement was used to stabilize an osteochondral fracture. Mechanical testing of the cement-stabilized fracture revealed a decrease in compressive strength and modulus at 4 weeks followed by an increase to greater than initial values at 12 weeks. Over time, the osteochondral fragment subsided into the underlying cement, but the subsidence did not correlate with mechanical strength. This osteochondral fracture model permits measurement of the overall material properties of a cement simultaneously weakened by resorption and reinforced by ingrowing bone.     

Complete Nucleotide Sequence Analysis of a Western Pacific Dengue-1 Virus Strain

We have determined the complete nucleotide sequence and the deduced amino acid polypeptide sequence of the genome of a dengue-1 (DEN-1) virus strain isolated from a patient on Nauru in the Western Pacific in 1974 (West Pac 74). The complete genome is 10,735 nucleotides in length and contains a single long open reading frame of 10,176 nucleotides encoding a polyprotein of 3392 amino acids. When compared to DEN-1 Singapore S275/90, the nucleotide and amino acid sequence homology are 94% and 97.8%, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.