Transactivation of herpes simplex virus type 1 immediate-early gene expression by virion-associated factors is blocked by an inhibitor of cyclin-dependent protein kinases

Initiation of productive infection by human herpes simplex virus type 1 (HSV-1) requires cell cycle-dependent protein kinase (cdk) activity. Treatment of cells with inhibitors of cdks blocks HSV-1 replication and prevents accumulation of viral transcripts, including immediate-early (IE) transcripts (26). Inhibition of IE transcript accumulation suggests that virion proteins, such as VP16, require functional cdks to activate viral transcription. In this report, we show that a cdk inhibitor, Roscovitine, blocks VP16-dependent IE gene expression. In the presence of Roscovitine, the level of virion-induced activation of a transfected reporter gene (the gene encoding chloramphenicol acetyltransferase) linked to the promoter-regulatory region of the ICP0 gene was reduced 40-fold relative to that of untreated samples. Roscovitine had little effect on the interaction of VP16 with VP16-responsive DNA sequences as measured by electrophoretic mobility shift assays. These data indicate that VP16-dependent activation of IE gene expression requires functional cdks and that this requirement is independent of the ability of VP16 to bind to DNA.

Highly Regio- and Stereoselective Intramolecular 1,3-Dipolar Cycloadditions of Norbornadiene-Tethered Nitrile Oxides

[reaction: see text] Intramolecular cycloadditions with high regio- and stereocontrol are important methods for the efficient assembly of complex molecular structures. Efficient routes to the synthesis of norbornadiene-tethered nitrile oxides have been developed, and their intramolecular 1,3-dipolar cycloadditions were studied. The cycloadditions occurred in good yields for a variety of substrates and were found to be highly regio- and stereoselective.

Functional inactivation of p53 by HPV-E6 transformation is associated with a reduced expression of radiation-induced potentially lethal damage

PURPOSE

To examine the effect of functional loss of p53 on radiation sensitivity and potentially lethal damage repair (PLDR).

MATERIALS AND METHODS

Radiation sensitivity and PLDR were examined in an isogenic pair of human tumour cell lines created by HPV-E6 transformation.

RESULTS

Inactivation of p53 by E6 transformation resulted in a cell line that was more resistant to killing by radiation but showed little enhancement in survival (PLDR) when plateau-phase cells were held non-cycling after radiation exposure. Holding p53-normal cells in plateau-phase after radiation exposure not only led to enhanced survival, but also to a reduction in the proportion of cells that blocked in G1 subsequent to release.

CONCLUSIONS

These results suggest that p53 expression influences that component of radiation sensitivity associated with PLDR.

Detection of chromosome aberrations by FISH as a function of cell division cycle (harlequin-FISH)

Chromosome aberrations are a sensitive indicator of genetic change, and the measurement of chromosome aberration frequency in peripheral blood lymphocytes is often used as a biological dosimeter of exposure (1,4). The length of time that cells are maintained in culture before cytogenetic analysis is probably the most important in vitro factor that influences both the frequency and types of aberrations that are seen following exposure to mutagens. Therefore, for accurate cytogenetic measurements of genetic damage, cells must be analyzed in their first mitosis following exposure. As cells progress through subsequent mitotic division cycles, cells with unstable types of aberrations, e.g., dicentrics and acentric fragments, are eliminated (1,3,4). Even the use of synchronized populations of cells does not guarantee that all cells analyzed will be in their first division following treatment. Small variations in growth rate after irradiation can lead to large variations in the proportion of cells that are in their first vs. a subsequent mitosis. For example, 48 h after G0 lymphocytes are stimulated to enter the cell cycle (the standard sampling time for cytogenetic analysis), up to 50% of the cells in mitosis can be in their second division cycle (10). While there are methods available to distinguish cells in different division cycles (see Introduction), they are not easily adapted for use with standard fluorescence in situ hybridization (FISH) procedures. The goal of this study was to develop a simple approach to detect aberrations by FISH whereby cells in different division cycles could be distinguished.

Labeling of the internal pool of GP IIb-IIIa in platelets by c7E3 Fab fragments (abciximab): flow and endocytic mechanisms contribute to the transport

Abciximab is a new antiplatelet therapeutic in ischemic cardiovascular disease. The drug, chimeric Fab fragments of a murine monoclonal antibody (MoAb) (c7E3), blocks GP IIb-IIIa function. However, its capacity to reach all receptor pools in platelets is unknown. Electron microscopy and immunogold labeling were used to localize abciximab in platelets of patients receiving the drug for up to 24 hours. Studies on frozen-thin sections showed that c7E3 Fab, in addition to the surface pool, also labeled the surface-connected canalicular system (SCCS) and alpha-granules. Analysis of gold particle distribution showed that intraplatelet labeling was not accumulative and in equilibrium with the surface pool. After short-term incubations of platelets with c7E3 Fab in vitro, gold particles were often seen in lines within thin elements of the SCCS, some of which appeared in contact with alpha-granules. Little labeling was associated with Glanzmann's thrombasthenia platelets, confirming that the channels contained bound and not free c7E3 Fab. Endocytosis of abciximab in clathrin-containing vesicles was visualized by double staining and constitutes an alternative mechanism of transport. The remaining free pool of GP IIb-IIIa was evaluated with the MoAb AP-2; flow cytometry showed it to be about 9% on the surface of nonstimulated platelets but 33% on thrombin-activated platelets. The ability of drugs to block all pools of GP IIb-IIIa and then to be associated with secretion-dependent residual aggregation must be considered when evaluating their efficiency in a clinical context.

Spontaneous play in children with autism: a reappraisal

Much controversy remains regarding the ability of children with autism to engage in spontaneous play. In this study children with autism, Down syndrome and typical development with verbal mental ages of approximately 2 years were assessed for play abilities at three data points. Even in this group of children with autism, who had relatively low verbal mental ages, symbolic play skills were not totally absent. However, it was possible to distinguish their pattern of play behaviors from the other two groups. Consequentially, it is argued that there are unusual features in early spontaneous play in children with autism and these atypical patterns are not restricted to their difficulties in the production of symbolic play. Such differences in early spontaneous play raise interesting questions about the etiology of autism, the direction of future research, and the theoretical models that can account for the condition.

Accuracy of orthognathic evaluation using telemedicine technology

OBJECTIVE

Telemedicine technology has the ability to project highly specialized medical and dental expertise anywhere in the world. This is particularly important to many small, isolated communities that do not have access to medical and dental specialists. Telemedicine also has the potential to reduce unnecessary travel, time away from work, and unneeded hospital admissions. For this technology to be successful, however, clinicians need to have confidence in its capabilities. This study was conducted to determine the accuracy of an orthognathic evaluation using telemedicine.

MATERIALS AND METHODS

Thirteen patients were randomly selected for review by two surgeons each using telemedicine and clinical examinations. Clinically acceptable differences were established, and the results of the two examination methods were compared.

RESULTS

A main effect of the examination method was observed in 7 of the 18 continuous measurements taken. Examination of the absolute value of the within-subject difference between the two examination methods demonstrated that the mean absolute difference was statistically different from zero for 13 of 18 measurements taken.

CONCLUSIONS

These data demonstrate that a relatively accurate orthognathic examination can be performed with this technology. With this in mind, clinicians may feel comfortable using this technology for other clinical applications.

Characterization of a nerve growth factor-inducible cellular activity that enhances herpes simplex virus type 1 gene expression and replication of an ICP0 null mutant in cells of neural lineage

Herpes simplex virus type 1 (HSV-1) ICP0 is required for efficient viral gene expression during lytic infection, especially at low multiplicities. A series of cellular activities that can substitute for ICP0 has been identified, suggesting that when the activity of ICP0 is limiting, these activities can substitute for ICP0 to activate viral gene expression. The cellular activities may be especially important during reactivation of HSV from neuronal latency when viral gene expression is initiated in the absence of prior viral protein synthesis. Consistent with this hypothesis, we have identified an inducible activity in cells of neural lineage (PC12) that can complement the low-multiplicity growth phenotype of an ICP0 null mutant, n212. Pretreatment of PC12 cells with nerve growth factor (NGF) or fibroblast growth factor (FGF) prior to infection produced a 10- to 20-fold increase in the 24-h yield of n212 but only a 2- to 4-fold increase in the yield of wild-type virus relative to mock treatment. Slot blot analysis of nuclear DNA isolated from infected cells treated or mock treated with NGF indicated that NGF treatment does not significantly affect viral entry. The NGF-induced activity in PC12 cells was expressed transiently, with peak complementing activity observed when cells were treated with NGF 12 h prior to infection. Addition of NGF 3 h after infection had little effect on virus yield. The NGF-induced cellular activity was inhibited by pretreatment of PC12 cells with kinase inhibitors that have high specificity for kinases involved in NGF/FGF-dependent signal transduction. RNase protection assays demonstrated that the NGF-inducible PC12 cell activity, like that of ICP0, functions to increase the level of viral mRNA during low-multiplicity infection. These results suggest that activation of viral transcription by ICP0 and transcriptional activation of cellular genes by NGF and FGF utilize common signal transduction pathways in PC12 cells.

Kinetic characterization of the ATPase cycle of the DnaK molecular chaperone

DnaK, the prototype Hsp70 protein of Escherichia coli, functions as a molecular chaperone in protein folding and protein disassembly reactions through cycles of polypeptide binding and release that are coupled to its intrinsic ATPase activity. To further our understanding of these processes, we sought to obtain a quantitative description of the basic ATPase cycle of DnaK. To this end, we have performed steady-state and pre-steady-state kinetics experiments and have determined rate constants corresponding to individual steps in the DnaK ATPase cycle at 25 degrees C. Hydrolysis of ATP proceeds very slowly with a rate constant (khyd approximately 0.02 min-1) at least 10-fold smaller than the rate constant for any other first-order step in the forward reaction pathway. The ATP hydrolysis step has an activation energy of 26.2 +/- 0.4 kcal/mol and is rate limiting in the steady-state under typical in vitro conditions. ATP binds with unusual strength to DnaK, with a measured KD approximately 1 nM. ADP binds considerably less tightly than ATP and dissociates from DnaK with a koff of approximately 0.4 min-1 (compared with a koff of approximately 0.008 min-1 for ATP). However, in the presence of physiologically relevant concentrations of inorganic phosphate (Pi), the release of ADP from DnaK is greatly slowed, approximately to the rate of ATP hydrolysis. Under these conditions, the ADP-bound form of DnaK, the form that binds substrate polypeptides most tightly, was found to represent a significant fraction of the DnaK population. The slowing of ADP release by exogenous Pi is due to thermodynamic coupling of the binding of the two ligands, which produces a coupling energy of approximately 1.6 kcal/mol. This result implies that product release is not strictly ordered. In the absence of exogenous inorganic phosphate, Pi product, by virtue of its higher koff, is released prior to ADP. However, at physiological concentrations of inorganic phosphate, the alternate product release pathway, whereby ADP dissociates from a ternary DnaK.ADP.Pi complex, becomes more prominent.

An appraisal of the efficacy and cost effectiveness of antenatal screening for hepatitis B

In this review published data are used to determine the benefits and costs of antenatal screening for hepatitis B carriers to prevent the later occurrence of hepatoma and chronic liver disease in their offspring. In Britain, babies born to carrier mothers have a 25% risk of perinatal infection and of becoming carriers themselves (the risk is 82% if their mothers are positive for the e antigen and 10% if negative). The carrier state increases the risk of hepatoma an estimated 86 times and the risk of chronic liver disease 20 times. Life table analysis showed that there is an 11% lifetime risk in carriers in Britain of dying from hepatoma (which results in seven years of life lost on average) and a 7% risk of chronic liver disease (14 years of life lost). Neonatal vaccination reduces the risk of the infant becoming a carrier by about 90%. Perinatal transmission occurs in 38 of every 100,000 neonates in Britain. Antenatal screening of all women and vaccinating babies of carrier mothers would prevent perinatal transmission in 34 of the 38 children (90%), or 255 per year in Britain. Of these 34, 8.4 children would be Chinese in ethnic origin, 4.2 African, 11.5 South Asian (from the Indian subcontinent), 2.0 Caribbean, and 7.3 would be white. Six deaths in the 34 from hepatoma or chronic liver disease caused by hepatitis B would then be prevented. The direct cost in Britain of screening all women, irrespective of ethnicity, at their first pregnancy only, would be 1300 pounds for each year of life saved (undiscounted) or 2500 pounds if screening at every pregnancy. Screening just Chinese, Africans, and South Asians, at first pregnancy only, would cost 330 pounds for each year of life saved but would prevent only 64% of these deaths. Vaccinating the infants of carrier mothers is likely also to prevent horizontal transmission of hepatitis B in early childhood and prevent the carrier state developing in an estimated three extra children for each child protected from vertical transmission. When this is taken into account the number of deaths prevented increases fourfold, reducing the cost for each year of life saved by 75%. Screening all women at first pregnancy only is an acceptably cost effective policy in Britain (1300 pounds for each year of life saved), actually preventing 45 deaths a year from hepatoma and chronic liver disease (or about 180 deaths if those horizontally infected are included), at a total cost of 540,000 pounds a year. It has the advantage of being comprehensive, equitable, and easier to implement than a policy based on screening of high risk ethnic groups.

Activation of gene expression by herpes simplex virus type 1 ICP0 occurs at the level of mRNA synthesis

ICP0 is a nuclear phosphoprotein involved in the activation of herpes simplex virus type 1 (HSV-1) gene expression during lytic infection and reactivation from viral latency. Although available evidence suggests that ICP0 acts at the level of transcription, definitive studies specifically addressing this issue have not been reported. In the present study we measured the ability of ICP0 to activate gene expression (i) from promoters representing the major kinetic classes of viral genes in transient expression assays and (ii) from the same promoters during viral infection at multiplicities of infection ranging from 0.1 to 5.0 PFU/cell. The levels of synthesis and steady-state accumulation of mRNA, mRNA stability, and levels of protein synthesis were compared in cells transfected with a reporter plasmid in the presence and absence of ICP0 and in cells infected with wild-type HSV-1 or an ICP0 null mutant, n212. In transient expression assays and during viral infection at all multiplicities tested, the levels of steady-state mRNA and protein were significantly lower in the absence of ICP0, indicating that ICP0 activates gene expression at the level of mRNA accumulation. In transient expression assays and during infection at low multiplicities (< 1 PFU/cell) in the presence or absence of ICP0, marked increases in the levels of viral mRNAs accompanied by proportional increases in the levels of protein synthesis were observed with increasing multiplicity. At a high multiplicity (5 PFU/cell) in the presence or absence of ICP0, mRNA levels did not increase as a function of multiplicity and changes in the levels of protein were no longer related to changes in the levels of mRNA. Collectively, these tests indicate that transcription of viral genes is rate limiting at low multiplicities and that translation is rate limiting at high multiplicities, independent of ICP0. Consistent with the lower levels of mRNA detected in the absence of ICP0, the rates of transcription initiation measured by nuclear run-on assays were uniformly lower in cells infected with the ICP0 null mutant at all multiplicities tested, implying that ICP0 enhances transcription at or before initiation or both. No evidence was found of posttranscriptional effects of ICP0 (i.e., effects on the stability of mRNA, nuclear-cytoplasmic distribution, polyribosomal mRNA distribution, or rates of protein synthesis). Taken together, these results suggest that ICP0 activates gene expression prior to or at the level of initiation of mRNA synthesis in transient expression assays and during viral infection. Based on these findings; we hypothesize that the exaggerated multiplicity-dependent growth phenotype characteristic of ICP0 null mutants reflects the requirement for ICP0 under conditions where the steady-state level of mRNA is rate limiting, such as during low-multiplicity infection and reactivation from latency.

Imitation of pretend play acts by children with autism and Down syndrome

Although there has recently been considerable research interest in the difficulties that children with autism have engaging in pretend play, little attention has been paid to the ability of these children to imitate pretend play acts. Furthermore, suggestions that children with Down syndrome have relatively advanced abilities in pretend play have not been accompanied by an examination of their capacity to imitate pretend play. Three groups of children: autistic, Down syndrome, and normally developing were studied for their capacity to imitate single pretend acts and a series of pretend acts that formed scripts. While the children with autism were surprisingly better than the other two groups on the single-scheme task, they demonstrated specific difficulties on the multischeme task. Results are discussed in relation to current theories of autism and the notion of imitation.

7E3 F(ab')2, a monoclonal antibody to the platelet GPIIb/IIIa receptor, protects against microangiopathic hemolytic anemia and microvascular thrombotic renal failure in baboons treated with C4b binding protein and a sublethal infusion of Escherichia coli

We have used our previously described baboon model of infusion of both a sublethal dose of Escherichia coli and C4b binding protein to assess the impact of inhibiting platelet function with the F(ab')2 fragment of the monoclonal antibody 7E3, directed against the platelet glycoprotein (GP)IIb/IIIa receptor, on the characteristic microvascular changes. At a dose of 0.25 to 0.35 mg/kg bolus plus an infusion of 0.25 to 0.35 mg/kg over 6 hours, c7E3 F(ab')2 had only a minimal impact on fibrinogen consumption and delayed but did not prevent, the development of thrombocytopenia. Treatment with 7E3 F(ab')2, however, produced significant protection from the development of microangiopathic hemolysis and renal insufficiency. Histologic examination supported these observations, with treated animals having fewer schistocytes on blood smear and less evidence of ischemic renal changes. Treated animals also had more rapid recovery of peripheral white blood counts, suggesting a possible protective effect of treatment on ischemic damage to the bone marrow. These data indicate that potent inhibition of platelet function via GPIIb/IIIa receptor blockade can decrease ischemic organ damage in this animal model that has features similar to those found in diffuse intravascular coagulation, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura.

The relationship between E-cadherin expression, clinical stage and tumour differentiation in oral squamous cell carcinoma

OBJECTIVES

To evaluate the expression of E-cadherin, a calcium-dependent cell adhesion molecule, in a retrospective analysis of paraffin embedded tissue specimens of oral squamous cell carcinoma and relationship with the clinical TNM stage and histochemical differentiation.

DESIGN

Paraffin embedded tissue sections of normal oral mucosa (n = 6), oral squamous cell carcinoma (SCC, n = 18) and metastatic lymph nodes (n = 2) were immunostained by a three-stage streptoavidin-biotin immunoperoxidase method using monoclonal antibody. The TNM staging and histochemical grading were done according to the standard criteria.

RESULTS

Normal oral epithelium showed a strongly positive pericellular distribution of E-cadherin in basal, parabasal and spinous layers and no staining was observed in the parakeratinized and cornified layers. In well differentiated SCCs, the centrally located cells in tumour islands showed no staining, but peripheral basally located tumour cells showed positive staining. Poorly differentiated SCCs were devoid of staining. In moderately differentiated SCCs, the staining pattern was found to be one of the following three types: (1) a pattern similar to that of well differentiated SCC; (2) central cells of tumour aggregates were reactive but peripheral cells showed weak to negative reaction; and (3) all cells showed a negative reaction, resembling the poorly differentiated SCC. Fischer exact test showed a statistically significant correlation with loss of E-cadherin and grades of tumour differentiation as well as an advancing T and N stage.

CONCLUSION

The loss of E-cadherin may correlate with advancing T and N stages of the tumour and a poor tumour cell differentiation in oral squamous cell carcinomas.

Toxoplasmic myocarditis and polymyositis in patients with acute acquired toxoplasmosis diagnosed during life

The presence of both toxoplasmic myocarditis and myositis in the same individual has been reported only at autopsy. We report the first case of biopsy-proven toxoplasmic myocarditis and polymyositis simultaneously occurring in the same individual that was diagnosed during life. Results of her toxoplasmic serology were consistent with acute toxoplasmosis. She subsequently developed visual symptoms consistent with toxoplasmic chorioretinitis. She had a positive clinical response to therapeutic agents specific against Toxoplasma gondii. Her toxoplasmic serological profile established the diagnosis of acute toxoplasmosis. A toxoplasmic serological profile should be obtained for patients with myocarditis and/or polymyositis of unclear etiology. Endomyocardial or skeletal muscle tissue biopsies may establish the definitive diagnosis of toxoplasmic myocarditis or polymyositis, respectively. Examination of blood by polymerase chain reaction analysis before antitoxoplasmic treatment and early in the course of primary infection with T. gondii may prove useful.

Selective elimination of human lymphoid cells with unstable chromosome aberrations by p53-dependent apoptosis

Alterations in p53 expression are associated with genomic instability, presumably because loss of p53 leads to an inability to eliminate damaged and therefore potentially unstable cells by apoptosis or by induced cell cycle block. We tested this hypothesis by examining the influence of apoptosis on X-ray-induced chromosome aberration frequency in two isogenic human B-lymphoblastoid cell lines; TK6, which is sensitive to the induction of apoptosis, and WI-L2-NS, a p53 mutant resistant to apoptosis induction. While TK6 was more sensitive than WI-L2-NS cells to the cytotoxic effects of X-rays, it showed fewer induced chromosome aberrations. Inhibition of apoptosis in TK6 cells with phorbol 12-myristate 13-acetate (PMA) resulted in X-ray-induced aberration frequencies similar in magnitude to WI-L2-NS. The results support the hypothesis that apoptosis acts to selectively remove damaged cells. The reduction in aberration frequency associated with apoptosis was seen primarily for unstable types of aberrations; acentric chromosome fragments and dicentric chromosomes. There was no effect on the induced frequency of balanced translocations, the stable counterpart to dicentrics. The failure to remove cells with unstable types of aberrations is consistent with the genomic instability that accompanies loss of p53 activity.

Site-directed mutations affecting the spectroscopic characteristics and midpoint potential of the primary donor in photosystem I

Photosystem I is a member of the iron-sulfur center or type I reaction centers. The primary electron donor in photosystem I is a chlorophyll a dimer termed P700. The biophysical properties of P700 are well understood, but the protein environment that gives it such unique properties is unknown. We have characterized site-directed mutants of the photosystem I reaction center protein PsaB and identified an amino acid, His-656, that interacts closely with one of the P700 chlorophylls. Mutation of His-656 to Asn or Ser increases the oxidation midpoint potential of P700/P700+. by 40 mV. The P700/P700+. optical difference spectra show the appearance of a new bleaching band at 667 nm. Electron nuclear double resonance spectroscopy indicates a significant increase in the hyperfine coupling corresponding to methyl protons at position 12 of the spin carrying chlorophyll a of P700+. The implication of these results to current structural models of the photosystem I reaction center is discussed.