Characterization of transgenic mice with targeted disruption of the catalytic domain of the double-stranded RNA-dependent protein kinase, PKR

The interferon-inducible, double-stranded RNA-dependent protein kinase PKR has been implicated in anti-viral, anti-tumor, and apoptotic responses. Others have attempted to examine the requirement of PKR in these roles by targeted disruption at the amino terminal-encoding region of the Pkr gene. By using a strategy that aims at disruption of the catalytic domain of PKR, we have generated mice that are genetically ablated for functional PKR. Similar to the other mouse model of Pkr disruption, we have observed no consequences of loss of PKR on tumor suppression. Anti-viral response to influenza and vaccinia also appeared to be normal in mice and in cells lacking PKR. Cytokine signaling in the type I interferon pathway is normal but may be compromised in the erythropoietin pathway in erythroid bone marrow precursors. Contrary to the amino-terminal targeted Pkr mouse, tumor necrosis factor alpha-induced apoptosis and the anti-viral apoptosis response to influenza is not impaired in catalytic domain-targeted Pkr-null cells. The observation of intact eukaryotic initiation factor-2alpha phosphorylation in these Pkr-null cells provides proof of rescue by another eukaryotic initiation factor-2alpha kinase(s).

The murine PKR tumor suppressor gene is rearranged in a lymphocytic leukemia

The double-stranded RNA-dependent kinase, PKR, is encoded by an interferon inducible gene and is largely responsible for the anti-viral effects of this cytokine. Recent studies have shown that PKR may also play a role in the regulation of normal cellular growth. Although numerous examples of viral strategies for inactivation of PKR exist, there is no evidence of PKR inactivation in tumors. We demonstrate here that the Tik gene, which encodes a dual-specificity kinase, is the murine homolog of PKR, the dsRNA-dependent kinase, and has undergone a rearrangement of one allele in a murine lymphocytic leukemia cell. We have cloned a cDNA that corresponds to a mutated transcript from the rearranged mPKR gene and show that while the mutated polypeptide retains its ability to dimerize and bind dsRNA, it is catalytically inactive. Although this mutated mPKR lacks apparent dominant-negative function, the net effect of reduced PKR activity in these cells may be significant.

Open versus closed surgical treatment of abscesses: a controlled clinical trial

BACKGROUND

Conventional drainage, curettage and packing of acute superficial abscesses has been challenged and in some centres replaced by curettage and primary closure under antibiotic cover. This technique has not been used widely in Australasia or North America, probably because of the lack of reassurance from local randomized trials.

METHODS

A randomized trial was conducted to compare the primary closure of acute superficial abscesses to conventional packing. Abscesses requiring drainage under a general anaesthetic were considered for the study, excluding extensive, secondary and deep suppurations. In the 'open' group, the abscess was drained, curetted, irrigated, and then packed. Instead of packing, the cavity in the 'closed' group was obliterated using interrupted vertical mattress skin sutures with/without closed suction drainage. Other aspects of management were standardized.

RESULTS

Of the 32 abscesses treated using the closed technique, 25 (78%) healed by primary intention after 1 week (SE(p) = 7.3%; 95% CI = 63.7-92.4%). One of the 29 abscesses (3%) treated using the open technique healed by secondary intention in a similar period of time. The difference was statistically significant (Chi-squared test with Yates' continuity correction = 31.70; P < 0.0001). There was no statistically significant difference in the overall incidence of healing, 1 month after surgery (chi 1(2) = 0.07; P > 0.9). In the closed group, healing was obtained by primary intention, leaving a linear surgical scar in 84% of the cases (SE(p) = 5.7%; 95% CI = 72.8-95.2%). Hospitalization and the need for analgesia and dressing changes were reduced by 40-60%.

CONCLUSIONS

Primary closure of acute superficial abscesses was associated with an improved outcome in terms of duration and quality of healing, postoperative pain, length of hospitalization, nursing care and, by implication, cost, and may be recommended as an alternative treatment that is superior to the orthodox technique.

Morphologic characteristics of erythroleukemia (acute myeloid leukemia; FAB-M6): a CALGB study

We have reviewed the clinical, morphologic, immunophenotypic, and cytogenetic features of 52 patients with erythroleukemia (FAB Cooperative Group; AML-M6) studied by the Cancer and Leukemia Group B (CALGB). The purpose of this study was to correlate morphology with the clinical features, immunophenotypes, and karyotypes of neoplastic cells, and with the response to therapy of patients with AML-M6. Thirty-three patients (63%) were male, median age 59 (range 16-81) years, 47 patients (90%) were white, and 42 patients (81%) had a performance status of < 2. Myelodysplastic changes were observed in at least 1 cell lineage in all cases, and in 2 cell lineages in 45 of 52 (86%) cases. Fifty percent or more of cases studied were positive for CD11b, CD13, CD15, CD33, glycophorin-A, and HLA-DR markers. Fourteen of 27 cases (52%) in whom karyotypic analyses were conducted had cytogenetic abnormalities. Five (19%) were simple (< 3 karyotypic abnormalities), while 9 (33%) were complex (> or = 3 abnormalities). We observed either a complete or partial loss of chromosomes 5, 7, or 12p, or the presence of trisomy 8, in 11 of 27 (41%) patients. Cases of AML-M6 were divided into group 1 (14 patients with bone marrow proerythroblasts and basophilic erythroblasts > 25% of all erythroblasts) and group 2 (38 patients with proerythroblasts and basophilic erythroblasts < or = 25% of all erythroblasts). We observed no significant differences between groups 1 and 2 in regard to sex, age, race, performance status, percentage of blood erythroblasts or myeloblasts, percentage of bone marrow erythroblasts, and periodic acid-Schiff (PAS) or myelodysplasia scores. Six of 6 (100%) patients of group 1, and 7 of 21 (33%) patients of group 2, had normal karyotypes (P = .006). Nine of 13 (69%) patients of group 1 and 15 of 33 (45%) patients of group 2 had a complete remission (CR) (P = .2). Eight of 11 (73%) cytogenetically normal patients achieved CR: 5 of 6 (83%) in group 1, and 3 of 5 (60%) in group 2. Five of 12 (42%) cytogenetically abnormal patients achieved CR. No difference in duration of survival (group 1, median = 4.6 months vs. group 2, median = 10.2 months; P = .93) was observed between the 2 groups. We conclude that AML-M6 is typified by multilineage involvement of hematopoietic cells. The morphology of erythroblasts in patients with AML-M6 may correlate with cytogenetic abnormalities and rate of CR.

Dual specificity kinases--a new family of signal transducers

Phosphorylation/dephosphorylation reactions are one of the dynamic mechanisms through which cells modulate protein activity in response to environmental stimuli. The eukaryotic molecules which are responsible for the phosphorylation of serine, threonine and tyrosine residues appear to have co-ordinately evolved from simple prokaryotic enzymes which primarily respond to nutritional cues. In multicellular eukaryotes the complexity of data transfer greatly exceeds that of simple bacteria. The eukaryotic cell needs to exchange information with neighbouring and distant sister cells. Positional, nutritional and hormonal data are transmitted from the extracellular milieu across the plasma membrane and into the cytoplasm. In certain cases the signal must pass into the nucleus or other subcellular organelles where it is decoded and the proper cellular response initiated. All of these events have been shown to have a protein kinase component and it seems likely that in mammalian cells over 1,000 different kinase molecules have evolved to form the requisite signal transducing networks. In this review we describe a previously unappreciated family of protein kinases, the dual specificity or DSK kinases, which play important roles in the regulation of normal cellular growth and differentiation.

Use of self-administered joint counts in the evaluation of rheumatoid arthritis patients

The validity and reliability of self-administered joint counts are reported in a group of 32 rheumatoid arthritis patients being followed at a university-based practice located in the Southeast region of the United States, serving low to middle income urban and rural patients. Adequate inter-rater reliability among the patients' and the research assistant's joint counts was obtained for upper (r = 0.74), lower (r = 0.96), and upper and lower extremities (r = 0.89). Convergent validity correlations for pain, helplessness, and the Joint Alignment and Motion scale were found to be adequate. We conclude that rheumatoid arthritis patients can reliably assess their joint counts. Self joint counts along with other validated self-reports of health status may be applicable to busy outpatient settings, as well as in clinical research.

Sequential addition of deferoxamine and hemin inhibits glioma tumor-cell growth

The toxicity of deferoxamine, a potent iron chelator may be antagonized by hemin a potential iron source. Using the MTT assay we explored the effects of different concentrations and schedules of deferoxamine and hemin or deferoxamine and iron free tin protoporphyrin (SnPP) in two neuroblastoma (VA-N-BR, SK-N-AS), and two glioblastoma multiforme (VA-MG-SL, and U-373 MG) cell lines. In these cell lines, survival after exposure to 10 mug/ml deferoxamine for three days ranged from 28% to 59%. Incubation with hemin alone, had variable effects on growth depending on the cell line. Concomitant exposure to equimolar concentrations of deferoxamine and hemin resulted in the reversal of deferoxamine induced toxicity. Surprisingly, in the glioblastoma multiforme cell lines sequential exposure to deferoxamine and then hemin resulted in additional toxic effects rather than abrogation of deferoxamine toxicity. Sequential exposure of all cell lines to deferoxamine, hemin, and the chemotherapeutic agent thiotepa resulted in enhanced toxicity over any drug used alone. Exposure of the cells to deferoxamine and SnPP or deferoxamine and FeCl3 did not result in increased toxicity. These results implicate iron as the toxic element but indicate that the iron is only toxic when presented to the cell bound to protoporphyrin, such as found in hemin.

Structural requirements for enhancement of T-cell responsiveness by the lymphocyte-specific tyrosine protein kinase p56lck

To understand the mechanism(s) by which p56lck participates in T-cell receptor (TCR) signalling, we have examined the effects of mutations in known regulatory domains of p56lck on the ability of F505 p56lck to enhance the responsiveness of an antigen-specific murine T-cell hybridoma. A mutation of the amino-terminal site of myristylation (glycine 2), which prevents stable association of p56lck with the plasma membrane, completely abolished the ability of F505 p56lck to enhance TCR-induced tyrosine protein phosphorylation. Alteration of the major site of in vitro autophosphorylation, tyrosine 394, to phenylalanine diminished the enhancement of TCR-induced tyrosine protein phosphorylation by F505 p56lck. Such a finding is consistent with the previous demonstration that this site is required for full activation of p56lck by mutation of tyrosine 505. Strikingly, deletion of the noncatalytic Src homology domain 2, but not of the Src homology domain 3, markedly reduced the improvement of TCR-induced tyrosine protein phosphorylation by F505 Lck. Additional studies revealed that all the mutations tested, including deletion of the Src homology 3 region, abrogated the enhancement of antigen-triggered interleukin-2 production by F505 p56lck, thus implying more stringent requirements for augmentation of antigen responsiveness by F505 Lck. Finally, it was also observed that expression of F505 p56lck greatly increased TCR-induced tyrosine phosphorylation of phospholipase C-gamma 1, raising the possibility that phospholipase C-gamma 1 may be a substrate for p56lck in T lymphocytes. Our results indicate that p56lck regulates T-cell antigen receptor signalling through a complex process requiring multiple distinct structural domains of the protein.

A comparison of the full and short versions of the Arthritis Impact Measurement Scales

This study examined the validity and reliability of full and short versions of the Arthritis Impact Measurement Scales (AIMS). One hundred fifty-five patients with Rheumatoid Arthritis followed at a University Hospital Rheumatology Clinic completed the full AIMS at baseline, 6 months, 12 months, and 18 months. After reducing the 45-item AIMS to 22, alpha reliabilities and test-retest correlations showed that, with the exception of test-retest correlations for mobility at 6 months and for pain at 12 and 18 months, the full and short scales were comparably reliable. Convergent validity correlations with theoretically related scales were also comparable. However, some of the short scales did not detect the same differences over time that the full scales did. Specifically, the short mobility, pain, anxiety, and depression scales were not as sensitive to change as the full scales. Except for these four scales, the short version appears to be a viable alternative for use by health professionals and researchers.

[Notes on the phantom. Supplements to Freud's metapsychology]

The author discusses secrets--phantoms--that are unconsciously passed on within a family from one generation to the next. They are experienced as foreign bodies and are not physically processed. A special technique is needed to decode them in the analytic process.

Disease and psychosocial factors related to physical functioning in rheumatoid arthritis

One hundred and fifty-five patients with rheumatoid arthritis (RA) were randomly selected from a tertiary care outpatient rheumatology clinic. Disease, treatment, psychosocial and demographic data were collected to test a biopsychosocial model of Physical Functioning as determined by the Arthritis Impact Measurement Scales (AIMS). Cross-sectional and longitudinal hierarchical and stepwise regression analysis were performed to identify variables associated with Physical Functioning. The results of the hierarchical regression revealed that only the disease and psychosocial sets of variables were significant. Stepwise regression revealed that Disease Severity (disease set) and Arthritis Helplessness (psychosocial set) accounted for 37% (longitudinal) to 60% (cross-sectional 12 months---greater than 12 months) of Physical Functioning variance. Our results suggest a role for the inclusion of psychosocial factors in studies of the development of physical disability in patients with RA.

Tyrosine phosphorylation of GAP and GAP-associated proteins in lymphoid and fibroblast cells expressing lck

The Ras GTPase activating protein (GAP) is a strong candidate for the protein that links protein-tyrosine kinases to the Ras mitogenic pathway. GAP and two associated proteins, p62 and p190, were shown to be phosphorylated on tyrosine in the LSTRA thymoma cell line, in which the p56lck tyrosine kinase is overexpressed as a result of retroviral promoter insertion. In NIH3T3 fibroblasts expressing specific oncogenic and transformation-defective variants of p56lck, we found that the tyrosine phosphorylation of GAP complexes required both enzymatic activation and myristylation of p56lck, and correlated with lck transforming activity. The interaction between p62 and p190 from lck-transformed fibroblasts and GAP could be reconstituted in vitro using bacterial TrpE fusion proteins containing GAP Src homology 2 (SH2) domains. In vitro complex formation was insensitive to the prior denaturation of SH2 ligands, suggesting that SH2-binding sites are formed by linear peptide sequences. These results suggest that the tyrosine phosphorylation of GAP, and its interactions with SH2-binding proteins, may be involved in fibroblast transformation by activated lck, and may participate in signal transduction and cellular transformation in lymphoid cells.

The lymphocyte-specific tyrosine protein kinase p56lck

The CD4 and CD8 T cell surface antigens are physically associated with the tyrosine protein kinase p56lck. Accumulating data indicate that p56lck transduces intracellular tyrosine protein phosphorylation signals upon engagement of CD4 and CD8 by major histocompatibility complex (MHC) determinants expressed on antigen-presenting cells (APCs). Recent studies show that these p56lck-related phosphorylation events enhance T cell receptor (TCR)-mediated functions and are critical for the proposed co-receptor roles of CD4 and CD8. p56lck is also capable of enhancing antigen receptor responsiveness in the absence of CD4 or CD8 expression, suggesting that it can directly contribute to the TCR-induced tyrosine phosphorylation signal.

Enhancement of T-cell responsiveness by the lymphocyte-specific tyrosine protein kinase p56lck

Lymphocyte-specific tyrosine protein kinase p56lck is physically associated with CD4 and CD8 T-cell surface molecules, suggesting that it may transduce CD4/CD8-triggered tyrosine phosphorylation signals during antigen stimulation. Indeed, antibody-mediated aggregation of CD4 (to mimic interaction with its ligand, major histocompatibility complex (MHC) class II molecules), rapidly elevates the kinase activity of p56lck and is associated with marked changes in tyrosine protein phosphorylation. Genetic analyses suggest that the interaction of CD4/CD8 with p56lck results in a positive signal during antigen-induced T-cell activation. To evaluate directly the role of p56lck in T-cell activation, we introduced a constitutively activated form of Lck protein (tyrosine 505 to phenylalanine 505 mutant); in a CD4-negative, MHC-class II restricted mouse T-cell hybridoma. We report here that, as for transfection of CD4, expression of the Lck mutant enhanced T-lymphocyte responsiveness. This finding provides direct evidence that p56lck can positively regulate T-cell functions and that it mediates at least some of the effects of CD4 and CD8 on T-cell activation.

Activation of p56lck through mutation of a regulatory carboxy-terminal tyrosine residue requires intact sites of autophosphorylation and myristylation

Mutation of the major site of in vivo tyrosine phosphorylation of p56lck (tyrosine 505) to a phenylalanine constitutively enhances the p56lck-associated tyrosine-specific protein kinase activity. The mutant polypeptide is extensively phosphorylated in vivo at the site of in vitro Lck autophosphorylation (tyrosine 394) and is capable of oncogenic transformation of rodent fibroblasts. These observations have suggested that phosphorylation at Tyr-505 down regulates the tyrosine protein kinase activity of p56lck. Herein we have attempted to examine whether other posttranslational modifications may be involved in regulation of the enzymatic function of p56lck. The results indicated that activation of p56lck by mutation of Tyr-505 was prevented by a tyrosine-to-phenylalanine substitution at position 394. Furthermore, activation of p56lck by mutation of the carboxy-terminal tyrosine residue was rendered less efficient by substituting an alanine residue for the amino-terminal glycine. This second mutation prevented p56lck myristylation and stable membrane association and was associated with decreased in vivo phosphorylation at Tyr-394. Taken together, these findings imply that lack of phosphorylation at Tyr-505 may be insufficient for enhancement of the p56lck-associated tyrosine protein kinase activity. Our data suggest that activation of p56lck may be dependent on phosphorylation at Tyr-394 and that this process may be facilitated by myristylation, membrane association, or both.

A comprehensive approach to teaching management in a degree-completion dental hygiene program

Changes in society have dictated changes in the future of the dental hygiene profession and in the curriculum used to prepare students. Dental hygiene students should be prepared to assume a variety of new roles in the oral health and health care fields, including administrator/manager, researcher, educator, clinician, patient advocate, and change agent. The role of the administrator/manager had been identified as an important one for dental hygienists. In order to develop the skills necessary to obtain a position in management or administration, dental hygiene students should have educational preparation in these areas. This paper describes the development of an enhanced business curriculum in a degree-completion program. The curriculum provides a basic foundation for the development of effective management skills and includes courses in business, human resources management, and marketing, along with elective course offerings and an externship program. An integrated approach to management is employed, with emphasis on application to oral health and health care delivery systems.

Prolonged apnoea with severe arterial hypoxaemia resulting from complex partial seizures

Multi-channel tape-recordings of the EEG, breathing movements, arterial pulsed oxygen saturation and ECG were performed on a four-year-old child with a history of cyanotic episodes. These had started at nine months of age, resulted in cardiopulmonary resuscitation on unnumerable occasions, and were refractory to anti-epileptic medication. During each episode seizure activity appeared first, followed within a few seconds by sinus tachycardia, prolonged absence of inspiratory efforts and severe arterial hypoxaemia. As the seizure activity ended, breathing movements restarted and there was a gradual improvement in oxygenation.