Non-isotropic noise correlation in PET data reconstructed by FBP but not by OSEM demonstrated using auto-correlation function

Background  

Positron emission tomography (PET) is a powerful imaging technique with the potential of obtaining functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules in a biological system, both in vitro and in vivo. PET images can be used directly or after kinetic modelling to extract quantitative values of a desired physiological, biochemical or pharmacological entity. Because such images are generally noisy, it is essential to understand how noise affects the derived quantitative values. A pre-requisite for this understanding is that the properties of noise such as variance (magnitude) and texture (correlation) are known.     

Quantitative determination of cell surface β-adrenoceptors in different rat skeletal muscles

In the present study, the density of cell surface beta-adrenergic receptors was determined in different skeletal muscles using the hydrophilic ligand [3H]CGP 12177. The density of beta-adrenergic receptors was highest in the slow-twitch soleus muscle (32.8+/-0.9 fmol mg dw(-1)) and lowest in the fast-twitch glycolytic white gastrocnemius (10.4+/-0.5 fmol mg dw(-1)) beta-Adrenoceptor density correlated closely with the percentage of type-I fibres (r=0.979; P<0.0001) and inversely with the percentage of type-IIB fibres (r=696; P<0.03). Incubation with isoprenaline (10 microM) for 30 min decreased the density of beta-adrenergic receptors in the cell surface from 32.9+/-0.8 to 19.3+/-0.7 fmol mg dw(-1) in the soleus and from 16.8+/-1.0 to 12.0+/-0.7 fmol mg dw(-1) in the epitrochlearis. Internalisation appeared rapid (half-time less than 5 min). To study externalisation of beta-adrenergic receptors, soleus strips were incubated 30 min with 10 microM isoprenaline and then transferred to buffer without agonist. The first incubation reduced the density to approximately 50%, the subsequent incubation without agonist increased cell surface receptor density to approximately 80% of the initial density after 1 h. No further increase was observed over the next 2 h, suggesting that some of the receptors had been degraded. Insulin or contractile activity did not influence rate of externalisation.     

Significant association of strictures and internal fistula formation in Crohn’s disease

Intestinal inflammation in Crohn’s disease (CD) may be complicated by the occurrence of strictures and fistulae. The pathogenesis of fistula formation is unknown. We therefore wanted to determine whether mechanical factors might contribute to the development of fistulae. Furthermore, we tried to define the path of internal fistulae through the muscular layer. For this purpose, surgical resection specimens from 42 consecutive patients with CD were prospectively studied. In gross examination the whole bowel was cut into circumferential cross sections 0.3 cm thick. Abnormal areas were histologically examined. Strictures were found in 38 patients (90.5%), and fistulae were observed in 27 (64.3%) patients. In 11 (40.7%) specimens fistulae were found within a stricture, in 15 (55.6%) at the proximal end, and in 1 (3.7%) no stricture was found. In 7 (25.9%) cases with fistulae, herniated mucosa was found within the muscularis propria or the subserosa. In 7 (25.9%) cases a blood vessel was identified near a fistula traversing the muscularis propria. From these findings we conclude that that mechanical factors may contribute to fistula formation. This is further supported by the fact that fistulae appear to traverse the muscular layer along piercing vessels. Received: 21 January 2000 / Accepted: 7 March 2000     

Monoclonal antibodies OKT 11 and OKT 11A have pan-T reactivity and block sheep erythrocyte “receptors”

Monoclonal antibodies OKT11 (γ1) and OKT11A (γ2) are described and appear to have similar binding specificities. They bind, in immunofluorescence, with >95% of infant thymocytes, staining both cortical and medullary cells, 65-80% of blood lymphocytes and selectively stain the T cell-dependent paracortical areas of tonsil. A small proportion (9-12%) of bone marrow lymphocytes stain, but this population excludes the terminal transferase-positive cells. Both the γ1 and γ2 antibodies stain the surface membrane Ig-negative lymphocytes in blood and tonsil and are able to block sheep E rosette formation (to normal or leukemic T cells). In contrast, other monoclonal anti-T reagents tested (OKT1, OKT3, OKT4, OKT6, OKT8, OKT9, OKT10) did not block E rosette formation. E rosette formation and OKT11 binding are coincident on T-ALL cell lines and both are trypsin-sensitive. In a series of 145 leukemias and 26 leukemic cell lines investigated, only leukemias with a T cell phenotype including E rosette positivity were reactive with OKT11 and OKT11A. OKT11A binds to a polypeptide of approximately 50000 molecular weight on thymic lymphocytes. This structure may carry the recognition site for sheep erythrocytes. These antibodies provide additional useful markers for T cell analysis and are of potential therapeutic value.     

On the various manifestations of spontaneous autoimmune diabetes in rodent models

Autoimmune (type 1) diabetes mellitus in mouse, rat, and humans shares several features, including T lymphocyte infiltration into pancreatic islets and a dependence on permissive class II major histocompatibility complex (MHC) alleles. We report here on an experimental model involving mice that express influenza hemagglutinin (HA) under the control of the insulin promoter and, at the same time, a transgenic class II MHC-restricted T cell receptor (TcR) specific for an HA peptide. These mice spontaneously develop islet infiltrates resembling those found in NOD mice and most animals become diabetic within 8 weeks of age. Because of the availability of a clonotypic TcR antibody, we can be confident that the Ins-HA transgene does not induce any measurable alterations in the vast majority of T cells with the transgenic TcR in primary and secondary lymphoid organs. Continuous export of large numbers of HA-specific lymphocytes from the thymus was not required for the manifestation of the disease since mice thymectomized at 3 days after birth still developed the disease albeit with smaller infiltrates.     

Inhibition of the development of immediate hypersensitivity by staphylococcal enterotoxin B

We investigated the ability of staphylococcal enterotoxin B (SEB) to modify the immediate hypersensitivity response induced in BALB/c mice following sensitization to ovalbumin (OVA), a response mediated by OVA-reactive Vβ8 T cells. Mice were sensitized by skin painting with OVA every second day over a period of 2 weeks. SEB, a potent activator of Vβ8⁺ T cells, was administered at the same site where OVA was applied (skin of the lower abdomen) following two different protocols. In protocol (A) SEB was injected intradermally 1 day before painting with OVA and on day 7; in protocol B, SEB was injected each time OVA was applied to the skin (eight times). SEB (but not SEA) altered the development of immediate hypersensitivity to OVA, as demonstrated by the reduction in allergen-specific IgE, decreased OVA-specific immediate skin test responsiveness, and prevented the development of increased airways responsiveness after bronchial challenge with OVA. Injections of SEB did not alter the proliferative responses of local draining lymph node cells or spleen mononuclear cells to OVA, indicating that administration of SEB did not inhibit the sensitization to OVA, but shifted the immune response away from an immediate type response (IgE/IgG₁) to IgG_2a, IgG_2b and IgG₃. Although both protocols of SEB treatment did not lead to a major deletion of the Vβ8 T cell population, they did reduce the proliferative response of Vβ8⁺ T cells to OVA. These data indicate that the bacterial toxin SEB is capable of modifying the immediate hypersensitivity response induced by OVA by altering the functional capacity of antigen-reactive Vβ8 T cells.     

Mechanismus der photopolymerisation des styrols, 4. Zur rolle der photo-(4π + 2π)-addukte als kettenüberträger und zur kinetik der photopolymerisation in gegenwart überlagerter,thermischer prozesse

The photopolymerization of styrene was investigated at 25°C, by following the variations in the rate of polymerization and the degree of polymerization with the light intensity, J_M, at different wavelengths of the exciting light (λ_e = 313 nm, λ_e = 335 nm). The corresponding data were analyzed in terms of the formalism between the rate R_P and the viscosity average degree of polymerization P _η. The kinetic evaluation shows that at least at small fractions of the absorbed light and at short duration of the irradiation the stabilization of the growing chain radicals will occur predominantly by bimolecular termination processes and not by chain transfer. This must be attributed to the fact that among the four theoretically possible isomeric photo-(4π + 2π)-intermediates (I) 1-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1a and 1b ) and 2-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1 ′ a and 1 ′ b ) the photostationary concentration [ 1a ]_∞ of the most reactive chain transfer agent 1a is—as a result of its very small quantum yield of formation ( φ_1a ? φ_1b + φ_1′a + φ_1′b )—extremely low and contributes only a few percent to the total photo-steady-state concentration of I. At higher temperatures (T > 25°C) and at small fractions of the absorbed light J_M/J_o (λ_e = 335 nm), the rate of photopolymerization R_P is controlled by the contributions of two independent routes of initiation: (1) the rate R, which accounts for the photo-free radical formation of the photo-intermediates I, and 2 the rate R, which is derived from the photoinduced free radical generation of the thermally produced Diels-Alder adducts 1a and 1b . As a further aspect of this analysis the results give strong evidence that the endo adduct 1a , when electronically excited, enters into a very efficient radical forming process, contrary to the other isomers 1b , 1 ′ b , and 1 ′ a , which seem to be mainly deactivated by their individual retro-Diels-Alder decompositions and will not enter into free radical formation to any noticeable extent: φ_S ^1a ? (φ_S ^1b + φ_S ^{1 ′ b} + φ_S ^{1 ′ a} ) An explanation of the very different stereodynamic behaviour is given.     

Terminal rearrangements in the genome of adenovirus type 12 mutants adapted to growth in two human tumor cell lines

After serial passage of adenovirus type 12 in cells of the human melanoma line Nki4 virus mutants with enhanced growth potential have been isolated which carry additional sequences of regularly increasing size at the right end of the genome. DNA sequence analysis was performed'to characterize these genomic alterations as well as those of the previously described Ad12 $\text{C}\text{4}\text{1}$ mutants adapted to growth in the human carcinoma cell line $\text{C}\text{4}\text{1}$ (I. Kruczek, E. Schwarz, and H. zur Hausen (1981)Int. J. Cancer27, 139–143). Duplication of the inverted terminal repetition (ITR) emerged as the common feature of the right terminal alterations of all the mutant genomes analyzed. The sequences present between the ITR repeats were of either right-end or left-end origin, the latter suggesting that left-end sequences comprising the ITR and parts of the adjacent unique sequences have been transferred to the right end of the genome. The different sizes of the additional sequences in Ad12 Nki-4 DNA could be explained by varying degrees of amplification of a basic additional sequence of 342 base pairs.     

Detection of methicillin-resistant Staphylococcus aureus and simultaneous confirmation by automated nucleic acid extraction and real-time PCR

A molecular assay for the simultaneous detection of a Staphylococcus aureus-specific gene and the mecA gene, responsible for the resistance to methicillin in staphylococci, was evaluated. The assay included an automated DNA extraction protocol conducted with a MagNA Pure instrument and real-time PCR conducted with a LightCycler instrument. The performance and robustness of the assay were evaluated for a suspension of methicillin-resistant S. aureus (MRSA) strain with a turbidity equivalent to a McFarland standard of 0.5, which was found to be the ideal working concentration. The specificity of the new molecular assay was tested with a panel of 30 gram-negative and gram-positive bacterial strains other than MRSA. No cross-reactivity was observed. In a clinical study, 109 isolates of MRSA were investigated. All clinical MRSA isolates gave positive results for the S. aureus-specific genomic target, and all but one were positive for the mecA gene. In conclusion, the new molecular assay was found to be quick, robust, and laborsaving, and it proved to be suitable for a routine molecular diagnostic laboratory.