Pragmatic observations from a post-COVID-19 cardiac evaluation register: prevalence of cardiological alterations from a basic diagnostic sequence and contribution of the clinical hystory

Introduction

The prevalence of cardiological sequelae in patients recovered from COVID-19 varies in different reports. This may be due to the population diversity studied or to the complementary methods on which the diagnosis was based.

Objective

1) To determine the prevalence of “de novo” cardiological alterations (DN) in the population recovered from COVID-19 using a basic cardiological evaluation sequence. 2) To evaluate the contribution of the clinical history (CH) in the detection of DN.

Methods

Patients (pts) with COVID-19, PCR (+) were included. The pts attended an ambulatory consultation office at least 30 days after discharge from COVID-19. The evaluation was performed in a stepwise manner: first Interview: CH, physical examination (PE), and EKG; second Interview: routine laboratory test, C-reactive protein, echocardiogram and cardiac biomarkers. Other complementary studies (Holter, RMI, CCG) were requested according to previous findings. The diagnosis of DN (by PE, EKG or echocardiogram, alone or with the addition of other methods) was defined as the appearance of cardiological alterations in patients with no pre-existing known heart disease or the progression of a known cardiac disease. The prevalence of DN is described. Sensitivity, specificity and predictive value of CH for DN are reported.

Results

A total of 246 pts were evaluated with the first interview (age: 52±13 years; women: 47.8%; caucasian: 60.6%; overweight: 79%; some pathological history: 71.5%; previous heart disease: 15.4%; hospitalization during the acute phase of COVID: 78.8%; mild Covid: 37%, moderate: 39%, severe: 24%; time between discharge and post-COVID evaluation: 68±42 days). DN were detected in 62 pts: rhythm disturbances: 41 (sinus tachycardia: 23 (18 isolated), sinus bradycardia: 3, supraventricular arrhythmia: 6, ventricular arrhythmia: 14); conduction disturbance: 10, ventricular dysfunction: 20 (12 de novo, 8 progression). Specific diagnoses: myocarditis: 6, coronary artery disease: 5, acute mitral insufficiency: 1. In 16 pts (6.5%) DN had clinical relevance. Six of them (2.4%) required hospitalization. In previously healthy pts with mild COVID, only rhythm disorders were detected in 3 pts. Se, Sp and PV of the CH is shown in Table 1. Eighteen Holter monitoring tests (5 +), 9 MRIs (5 +), 4 CCGs (2 +) were performed.

Conclusions

1) Using a basic cardiac diagnostic sequence, at least 30 days after discharge, a quarter of post-COVID patients had “de novo” cardiological findings. However, a small percentage became clinically relevant. The causal relationship of DN with COVID-19 cannot be unequivocally asserted. Previously healthy patients have low prevalence of cardiac findings detected with a basic diagnostic sequence.

2) The data obtained from the clinical history have a low positive predictive value.

Funding Acknowledgement

Type of funding sources: None.

Epicardial Left Atrial Appendage Exclusion Reduces Blood Pressure in Patients With Atrial Fibrillation and Hypertension

BACKGROUND

Percutaneous left atrial appendage exclusion (LAAE) has evolved as an alternative strategy for stroke prevention in atrial fibrillation (AF). Recent observational data have suggested that epicardial LAAE can have substantial impact on arrhythmia burden and hemodynamic profile.

OBJECTIVES

The authors aimed to study the impact of epicardial versus endocardial LAAE on systemic blood pressure in hypertensive AF patients.

METHODS

This was a prospective, nonrandomized study comparing 247 patients who underwent epicardial LAAE with 124 patients with endocardial exclusion. Clinical outcomes were measured at 3 months and 1 year. Primary outcome was improvement in systolic blood pressure (SBP) between both groups compared with baseline. Secondary outcome included changes in diastolic pressures (DBP), serum electrolytes, and creatinine.

RESULTS

There was no significant difference in baseline SBP between epicardial and endocardial groups. SBP was significantly lower in the epicardial group both at 3 months (122 ± 11.8 mm Hg vs. 129.7 ± 8.2 mm Hg; p < 0.001) and 1 year (123 ± 11.6 mm Hg vs. 132.2 ± 8.8 mm Hg; p < 0.001) compared with the endocardial group. An adjusted multivariate linear mixed effects model demonstrated that epicardial LAAE significantly decreased SBP by 7.4 mm Hg at 3 months and by 8.9 mm Hg at 1 year (p < 0.0001). There was a trend toward lower DBP with epicardial LAAE at 3 months by 1.3 mm Hg (p = 0.2) and at 1 year by 1.8 mm Hg (p = 0.09). There was no significant difference in serum electrolytes and creatinine between both groups.

CONCLUSIONS

In hypertensive AF patients, epicardial LAAE significantly decreases SBP both at 3 and 12 months compared with endocardial exclusion.

Effective orifice area and hemodynamic performance of the transcatheter Edwards Sapien 3 prosthesis: short-term and 1-year follow-up

Aims

The Edwards Sapien 3 heart valve prosthesis (S3) is commonly used for transcatheter aortic valve implantation (TAVI) and is available in three sizes. To date no data has been published on the effective orifice area (EOA) and the hemodynamic performance of the three different S3 sizes. The aim of this study was to measure the size-specific EOA and hemodynamic performance of the S3 in short-term and 1-year follow-up.

Methods and results

One hundred and thirteen consecutive patients treated by TAVI with a S3 prosthesis at the Heart Clinic Zurich between May 2014 and July 2015 were included. Clinical data were extracted from the Swiss TAVI registry. The EOA was calculated using Doppler echocardiography (peri-interventionally and at discharge) and by 3D-biplane transoesophageal echocardiography (peri-interventionally). Mean transvalvular gradients (dPmean) were additionally calculated with Doppler echocardiography at 30 days and 1 year. Results were analysed separately for the 23 mm (n = 42; 37%), 26 mm (n = 46; 41%), and 29 mm (n = 25; 22%) prostheses. At discharge, the EOAs were 1.6 ± 0.2 cm2 (23 mm S3), 2.0 ± 0.2 cm2 (26 mm S3), and 2.7 ± 0.2 cm2 (29 mm S3), p < 0.001. The dPmeans at discharge were 10.9 ± 6.0 mmHg (23 mm S3), 10.4 ± 3.5 mmHg (26 mm S3), and 8.9 ± 2.8 mmHg (29 mm S3), p = 0.235, and did not significantly change over time within any of the S3 sizes.

Conclusions

Post-TAVI, the EOAs of the three different S3 prosthesis sizes differ significantly, the transvalvular gradients, however, are comparable. Mean transvalvular gradients remain stable over time and document good prosthesis function after 1 year.

Surgical epicardial left atrial appendage closure:A true alternative

Left atrial appendage closure was originally described by Madden in 1949 who was the first to perform appendix amputation. This was a very invasive procedure with poor outcome, but preformed for stroke prevention. Much later, it was James Cox whom described the Cox-Maze procedure, which included multiple incisions to create a maze like pathway for the electrical impulse to go undisturbed from the sinus node down to the atrio-ventricular node. Since then cardiac surgeons stopped focusing on the left atrial appendage and went on about seemingly more important things. Only with the advent of catheter based options for stand alone left atrial appendage closure did the interest in the field light up again.

Long-term results of simplified frozen elephant trunk technique in complicated acute type A aortic dissection: A case–control study

Aim

To describe the long-term experience of a simplified frozen elephant trunk technique (sFETT) used in complicated acute type A aortic dissection (AAAD) treatment.

Methods and results

Between January 2001 and December 2012, 34 patients (mean age 59.9 ± 11.0 years) with complicated AAAD (DeBakey I) underwent an emergency surgery including sFETT. sFETT consisted in gluing the dissected aortic arch wall layers with gelatine-resorcinol adhesive and video-assisted antegrade open arch aortic stent-graft deployment in the arch or proximal descending aorta. In addition to sFETT, the aortic root was addressed with standard techniques. A 30-day mortality was 14.7% (five patients) due to bleeding (1), multiple organ failure (2), and colon ischemia (2). Postoperative morbidity included neurological (2), renal (1) and cardio-pulmonary complications (4), as well as wound infection (1). Mean follow-up was 74.4 ± 45.0 months. Actual survival rates were 73.5% at 1 year, 70.2% at 5 years, and 58.5% at 13 years of follow-up. Six patients died during long-term follow-up from heart failure (1) and unknown reasons (5). Five patients required reoperation for aortic arch (3) or aorto-iliac (2) progression of aneurysm during the mid- and long-term follow-up. The remaining patients showed favorable evolution of the dissected aorta with false lumen occlusion in most cases and stable aortic diameters.

Conclusions

In AAAD patients, sFETT as used in our series is an easy and safe technique to repair the aortic arch. Long-term results after sFETT showed false lumen occlusion and stable aortic diameter in up to 13 years of follow-up.

Cardiac CT and echocardiographic evaluation of peri-device flow after percutaneous left atrial appendage closure using the AMPLATZER cardiac plug device

OBJECTIVES

The aim of the study was to examine frequency, size, and localization of peri-device leaks after percutaneous left atrial appendage (LAA)-closure with the AMPLATZER-Cardiac-Plug (ACP) by using a multimodal imaging approach, i.e. combined cardiac-CT and TEE follow-up.

BACKGROUND

Catheter-based LAA-occlusion using ACP aims to reduce the risk of stroke in patients with atrial fibrillation. Detection of peri-device leaks after ACP implantation by TEE is challenging, the few available data are inconsistent and the frequency of LAA leaks after ACP implantation remains therefore unclear.

METHODS

Cardiac-CT using a multi-phase protocol and a second-generation dual-source-CT-system was performed in 24 patients with non-valvular atrial fibrillation starting 3 months after LAA-closure by ACP. Color Doppler multiplane TEE was used to evaluate peri-device flow.

RESULTS

Cardiac-CT follow-up detected any persistent LAA contrast filling in 62% of patients (n = 15), but leak-sizes were small (1.5 ± 1.4 mm). Peri-device leaks were almost exclusively localized at the posterior portion of the LAA-orifice (>90%). TEE follow-up revealed peri-device flow in 36% of patients (jet-sizes: ≤ 4 mm). ACP-lobe compression (>10%) and perpendicular ACP-lobe orientation to the LAA-neck axis, that was also dependent on LAA anatomy, were substantially more frequent in patients with complete LAA closure.

CONCLUSION

The present study evaluates for the first time peri-device flow after LAA closure by ACP using a combined cardiac-CT and TEE follow-up. Persistent LAA-perfusion was frequently detected, leak-sizes were small and were less frequent when lobe compression was >10% and lobe orientation was perpendicular to the LAA-neck axis, that was also related to the LAA anatomy. The clinical significance of these small leaks after LAA-closure using ACP needs to be further evaluated in future studies.

What Happens to Functional Mitral Regurgitation after Aortic Valve Replacement for Aortic Stenosis?

Background: Patients with aortic stenosis (AS) treated with aortic valve replacement (AVR) may also present with associated functional mitral valve regurgitation (FMR). Whether to also address the mitral valve at the time of AVR remains unclear. This study was designed to determine the influence of MR on survival and its evolution over time.Methods: We retrospectively reviewed 74 patients with FMR who underwent isolated AVR between 1999 and 2006 at our institution. Inclusion criteria were surgery for AVR with severe AS (mean age, 69 years; N = 47; 64% women) and FMR (grade I, 80%; grade II, 19%; grade III, 1%). Echocardiography follow-up data were obtained by mail questionnaires sent to the referring cardiologists of all survivors. All parameters were analyzed with the Kaplan-Meier method and the sign test.Results: The operative mortality rate was 2%, and 9 patients (12%) died during follow-up. The mean (SD) follow-up time was 48 ± 33 months, and follow-up 96% complete. The follow-up demonstrated a decrease of FMR by 2 degrees in 3 patients (4%), and 1 degree in 14 patients (19%); regurgitation remained unchanged in the majority of patients (n = 47; 63%). FMR worsened in 10 patients overall (14%), and new-onset atrial fibrillation was found in 24 patients (33%); however, the statistical analysis failed to demonstrate an impact of worsening FMR on survival.Conclusion: MR in patients with severe AS and FMR at the time of AVR does not appear to worsen significantly over time. Not dealing with the mitral valve at the time of AVR might be warranted for selected patients.

Computed Tomography Angiography is an Excellent Tool for the Diagnosis of Congenital Coronary Artery Anomalies: A Report of 2 Cases

Congenital coronary artery anomalies are sporadically discovered in patients undergoing coronary angiography and in autopsy series. Although most anomalies are clinically insignificant, some may become causes of cardiovascular morbidities and mortality. Diagnosis is commonly made with conventional coronary artery angiography. The current development of modern cardiac computed tomography allows less invasive imaging of the coronary arteries and might provide additional anatomical and morphological information. Herein, we report our experience with computed tomography coronary angiography, describing 2 clinical cases of patients with symptomatic congenital coronary artery anomalies requiring cardiac surgery.

Mitral valve repair with Carpentier-McCarthy-Adams IMR ETlogix annuloplasty ring for ischemic mitral regurgitation: early echocardiographic results from a multi-center study

BACKGROUND

Ischemic mitral regurgitation (IMR) is associated with asymmetric changes in annular and ventricular geometry. Surgical repair with standard symmetric annuloplasty rings results in a high incidence of residual or recurrent mitral regurgitation (MR). The Carpentier-McCarthy-Adams (CMA) IMR ETlogix annuloplasty ring is the first remodeling ring specifically designed to treat asymmetric leaflet tethering and annular dilatation. We used quantitative 2-dimensional echo to examine early results of mitral valve (MV) repair with the CMA IMR ETlogix annuloplasty ring in patients with IMR.

METHODS AND RESULTS

Fifty-nine patients (aged 68+/-12 years) with grade > or = 2+ IMR (graded on a scale of 0 to 4+) underwent MV repair with the CMA IMR ETlogix annuloplasty ring. We assessed the mitral annular diameter (MAD), tethering area (TA), and tenting height (TH) of the MV in 4-chamber, 2-chamber, and long axis views at mid-systole before and 3 to 10 days after surgery. After surgery, 57 of 59 (97%) patients had grade 0 or 1+ MR, whereas 2 patients had 2+ MR. MV repair with the CMA IMR ETlogix ring significantly reduced MAD, TA, and TH (P<0.001, for all 3 echo views), particularly in the long axis and 4-chamber views.

CONCLUSIONS

Surgical repair of IMR with the novel asymmetric CMA IMR ETlogix annuloplasty ring provided excellent early results with effective reduction of MR, MAD, and leaflet tethering. This novel etiology-specific strategy may result in improved outcomes in IMR patients.

Influence of peroxisome proliferator-activated receptor activation by its endogenous ligand 15-deoxy 12,14 prostaglandin J2 on nitric oxide production in term placental tissues from diabetic women

Diabetes induces alterations which condition placental remodelling. The levels of nitric oxide (NO) (a modulator of placental invasiveness, differentiation and proliferation) were higher in term placental explants from diabetic patients when compared to controls. Peroxisome proliferator-activated receptor gamma (PPARgamma) activation by its endogenous ligand 15-deoxy Delta(12,14)prostaglandin J(2) (15dPGJ(2)), is a differentiating factor of adipocytes and other cell types, such as trophoblasts. 15dPGJ(2) is also able to down-regulate NO production in different cell types. Our study evaluated the levels of 15dPGJ(2) and PPARgamma and the influence of PPARgamma activation by 15dPGJ(2) on the production of NO, in term placental tissues from control, pre-gestational and gestational diabetic patients. Our results showed that 15dPGJ(2) was present in human term placenta, and that its levels were diminished in gestational (P<0.05) and pre-gestational (P<0.002) diabetic women when compared to controls. Exogenous 15dPGJ(2) addition (2 x 10(-6) mol/l) down-regulated NO production in placenta from control (P<0.001) and pre-gestational diabetic (P<0.01) patients, but failed to do so in gestational diabetic women, whose placental PPARgamma expression was diminished in comparison to controls (P<0.001). As the exogenous activation of PPARgamma prevented NO overproduction in placenta from pre-gestational diabetic women, it may have the potential to improve fetal outcome in this pathology.

Left ventricular assist device as bridge to heart transplantation--lessons learned with the MicroMed DeBakey axial blood flow pump

OBJECTIVE

The MicroMed DeBakey left ventricular assist device (LVAD) axial blood flow pump was used as bridge to heart transplantation (HTx) in patients with terminal heart failure. The aim was to evaluate this novel mechanical circulatory support system in regard to overall outcome.

METHODS

Prospective study in 15 HTx candidates (mean age 40+/-7 years) with terminal heart failure and maximal medical treatment due to ischemic cardiomyopathy (CMP, n=5), dilated CMP (n=3), restrictive CMP (n=2), unclassified CMP (n=1), metabolic CMP (n=1), valvular CMP (n=1) and congenital CMP (n=2). All patients were implanted with a MicroMed DeBakey LVAD. A rescue procedure was necessary in eight critical patients, while seven underwent elective LVAD implantation. Procedures were performed via median sternotomy, in normotherm femoro-femoral CPB (mean duration 59+/-1 min). Oral Marcoumar (INR 2.0-3.0) and Aspirin (100 mg daily) were started as soon as possible. Patients were discharged into a specialized rehabilitation clinic from which it was possible to release them home after a few weeks.

RESULTS

Successful implantation and discharge from ICU (mean stay 10+/-7 days) was possible in 11 patients. Seven were transplanted (mean support 50.7 days) and one is awaiting HTx (support >310 days) in the comfort of his home (NYHA I). Survival was 100% among the transplanted patients. Of the seven elective implants, five, and of the eight rescue procedures three patients underwent successful HTx. Four patients died early, while three patients died late on pump support due to intracranial hemorrhage (n=2, 73 and 76 days) and chest infection (n=1, 124 days). All survivors were discharged from hospital, with significant decrease in NYHA class (mean 3.8-2.4 (n=11)). Treadmill testing showed increased exercise tolerance, from 35 to 71W (n=4). Plasma BNP values (mean 950-162 ng/l (n=4)) and pulmonary resistance (mean 316-194.5 dyne s/cm(5) (n=3)) decreased significantly during LVAD support.

CONCLUSIONS

The MicroMed DeBakey LVAD is simple to implant; outpatient treatment is safe and efficient. Patients' condition and pulmonary resistances normalize within 6 weeks, making previously considered inoperable patients amenable for HTx. HTx can be performed in low-risk situation, allowing better donor-recipient matching and improving overall outcome.

Combined positron emission tomography and magnetic resonance imaging for the planning of stereotactic brain biopsies in children: experience in 9 cases

Because brain tumors can be histologically heterogeneous, stereotactic brain biopsies (SBB) may lead to inaccurate diagnosis or grading. Positron emission tomography (PET) has been used in pediatric neuro-oncology to help in the understanding and management of brain neoplasms. We combined PET and magnetic resonance (MR) imaging in the planning of SBB in 9 children (5 males and 4 females, aged 2-14 years) with infiltrative, ill-defined brain lesions. Tracers used for PET were (18)F-2-fluoro-2-deoxy-D-glucose in 4 cases, (11)C-methionine in 2 cases and both tracers in 3 cases. Biopsy targets were selected in hypermetabolic areas. PET-guided SBB provided accurate histological diagnosis in all patients and allowed a reduction of the number of trajectories in lesions located in functional areas. It also helped in better understanding and management of complex cases. This preliminary series suggests that combining PET and MR imaging in the planning of SBB in children (1) improves the diagnostic yield of SBB in infiltrative, ill-defined brain lesions, (2) makes it possible to reduce the sampling in high-risk/functional areas and (3) improves the quality of therapeutic management of pediatric brain tumors.

Double-stranded RNA-dependent protein kinase, PKR, down-regulates CDC2/cyclin B1 and induces apoptosis in non-transformed but not in v-mos transformed cells

The interferon (IFN)-induced, double stranded RNA (dsRNA)-activated serine/threonine kinase, PKR, is a potent negative regulator of cell growth when overexpressed in yeast or mammalian cells. Paradoxically, while it can function as a tumor suppressor and inducer of apoptosis, it is overexpressed in a variety of human cancers. To resolve this enigma, we established cell-lines that overexpress PKR in non-transformed and in v-mos transformed CHO cells. Overexpression of PKR suppressed the proliferation of CHO cells by inducing a transient G0/G1 arrest, followed by a delayed G2/M arrest, which attenuated cell cycle progression. These effects were accompanied by early induction of p21/WAF-1 and delayed downregulation of CDC2 and cyclin B1. Induction of proapoptotic activity of the ectopic PKR paralleled the onset of G2/M arrest in CHO cells. However, while transiently inducing p21/WAF-1, PKR did not impose G2/M arrest or apoptosis in v-mos-transformed cells, nor was CDC2 or cyclin B1 down-regulated in those cells. These findings link the proapoptotic activity of PKR to the arrest of cell cycle at the G2/M phase. Consequently, the apoptotic activity of PKR could be counter-acted by an oncogene-like v-mos that overrides the G2/M arrest induced by PKR.

Structural characterization of erythroid and megakaryocytic differentiation in Friend erythroleukemia cells

OBJECTIVE

The aim of this study was to examine the structural characterization of erythroid and megakaryocytic cell differentiation in Friend erythroleukemic cells using spectral imaging and electron microscopy.

MATERIALS AND METHODS

Two variants of Friend erythroleukemia cells were treated with hexamethylene bisacetamide (HMBA) to induce differentiation: 1) MEL, which exhibit the normal phenotype and are susceptible to differentiation; and 2) the resistant R1 cells. The cells were analyzed by spectral imaging along with transmission and scanning electron microscopy. The expression of cell cycle regulatory proteins was analyzed by Western blotting.

RESULTS

Spectral imaging of HMBA-treated MEL and R1 cells stained by May-Grünwald-Giemsa and subjected to spectral similarity mapping revealed five morphologic cell types: proerythroblast-like cells, normoblast-like cells, reticulocyte-like cells, megakaryocytes, and apoptotic cells. In MEL cells, both megakaryocytic differentiation characterized by nuclear lobes and erythroid differentiation characterized by accumulation of hemoglobin were detected; R1 cells were not committed to terminal differentiation. HMBA-induced cell cycle arrest at G(1) affected the expression of regulatory proteins in a similar manner in both types of cells. Expression of cyclin-dependent kinase 4 decreased and expression of p21(WAF1) increased. The level of the underphosphorylated form of phosphorylated retinoblastoma protein increased, inducing a decrease in the level of c-myc. In addition, we detected a decrease in the expression of the anti-apoptotic regulator, Bcl-2, and an increased expression of the pro-apoptotic regulator, Bax.

CONCLUSIONS

Spectral imaging provides new insight for the morphologic characterization of erythroid and megakaryocytic cell differentiation as well as apoptosis. Image analysis was well correlated to cell cycle arrest and the expression of regulatory proteins.

The sequence of the human genome

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

FER kinase activation of Stat3 is determined by the N-terminal sequence

p94(fer) and p51(ferT) are two tyrosine kinases that share identical SH2 and kinase domains but differ in their N-terminal regions. To further explore the cellular functions of these two highly related tyrosine kinases, their subcellular distribution profiles and in vivo phosphorylation activity were followed using double immunofluorescence assay. When combined with immunoprecipitation analysis, this assay showed that p94(fer) can lead to the tyrosine phosphorylation and activation of Stat3 but not of Stat1 or Stat2. Native p94(fer) exerted this activity when residing in the cytoplasm. However, modified forms of p94(fer), which are constitutively nuclear, could also lead to the phosphorylation of Stat3. Endogenous Stat3 and p94(fer) co-immunoprecipitated with each other, thus proving the interaction of these two proteins in vivo. Unlike p94(fer), p51(ferT) did not induce the phosphorylation of Stat3 but led to the phosphorylation of other nuclear proteins. Replacing the unique 43-amino acid-long N-terminal tail of p51(ferT) with a parallel segment from the N-terminal tail of p94(fer) did not change the subcellular localization of p51(ferT) but enabled it to activate Stat3. Thus the different N-terminal sequences of p94(fer) and p51(ferT) can affect their ability to induce phosphorylation of Stat3 and most probably direct their different cellular functions.

Expression of a PKR dominant-negative mutant in myogenic cells interferes with the myogenic process

In this study, we explored the possibility that PKR, a dsRNA-activated regulatory protein, is an essential component in the differentiation program of myogenic cells in vitro. For this purpose, we used a retroviral expression vector pMV7, harboring the PKR dominant-negative mutant PKRDelta6 (pMV7-p68Delta6). Murine C2C12 myogenic cells were transfected either with pMV7 or with pMV7-p68Delta6. Neomycin-resistant clones from both types were isolated and expanded and the results obtained with the representative clones C2-NEO (transfected with pMV7) and clone 17 and clone 22 (both transfected with pMV7-p68Delta6) are presented. In clone 17 and 22 cells, regardless of IFN treatment, a similar level of the transfected human p68 PKR mutant was detected. This protein was absent in C2-NEO cells. In parallel, in all types of cells, a low basal level of the endogenous murine p65 PKR protein was observed, which was further induced by IFN. However, PKR enzymatic activity was significantly induced by IFN only in C2-NEO cells, while it was hardly detected in both clones 17 and 22, even after IFN treatment. Furthermore, in contrast to C2-NEO cells, only a slight to moderate increase in enzymatic activity was observed in clone 17 and 22 differentiating cells. Next, cells were grown either in growth medium (GM) or differentiation medium (DM), and the progression of the myogenic program was studied. An inhibition in myotube formation in clone 17 versus C2-NEO cells cultivated in DM was clearly observed. Furthermore, while the growth rate and thymidine incorporation were reduced in C2-NEO cells grown in DM, both clone 17 and 22 cells were less affected under the same conditions. Similarly, a delay in the accumulation of the transcription factors MyoD and myogenin, as well as in creatine kinase activity and accumulation of troponin T, was detected in DM-cultivated clone 17 and clone 22 cells. Moreover, a delay in the induction of p21 (WAF1), in down-regulation of cyclin D1 and c-myc, and in the accumulation of the underphosphorylated form of pRb was also observed in clone 17 cells. We conclude that inhibition of endogenous PKR activity by a PKR dominant-negative mutant interferes with the myogenic program of murine C2C12 myogenic cells.

A decision tree system for finding genes in DNA

MORGAN is an integrated system for finding genes in vertebrate DNA sequences. MORGAN uses a variety of techniques to accomplish this task, the most distinctive of which is a decision tree classifier. The decision tree system is combined with new methods for identifying start codons, donor sites, and acceptor sites, and these are brought together in a frame-sensitive dynamic programming algorithm that finds the optimal segmentation of a DNA sequence into coding and noncoding regions (exons and introns). The optimal segmentation is dependent on a separate scoring function that takes a subsequence and assigns to it a score reflecting the probability that the sequence is an exon. The scoring functions in MORGAN are sets of decision trees that are combined to give a probability estimate. Experimental results on a database of 570 vertebrate DNA sequences show that MORGAN has excellent performance by many different measures. On a separate test set, it achieves an overall accuracy of 95 %, with a correlation coefficient of 0.78, and a sensitivity and specificity for coding bases of 83 % and 79%. In addition, MORGAN identifies 58% of coding exons exactly; i.e., both the beginning and end of the coding regions are predicted correctly. This paper describes the MORGAN system, including its decision tree routines and the algorithms for site recognition, and its performance on a benchmark database of vertebrate DNA.

Involvement of PKR in the regulation of myogenesis

The involvement of the double-stranded RNA-activated protein kinase PKR in the regulation of the myogenic process was investigated. For this purpose, the murine myogenic cell line C2C12 was used. The cells were first cultivated in either growth medium or differentiation medium (DM), and the activation of PKR during differentiation was determined by monitoring its enzymatic activity and by immunoblot analysis. A significant increase in both parameters was detected already at 24 h in DM, whereas in cells grown in growth medium, the increase was evident only after 96 h, when spontaneous differentiation was observed in highly crowded cultures. Consequently, we established the direct effect of PKR activation on the myogenic process. C2C12 cells were transfected with an expression vector harboring a cDNA molecule encoding human PKR fused to the inducible metallothionein promoter. One of the clones (clone 8) expressing high levels of PKR was selected and further analyzed. In the presence of ZnCl2, which activates the promoter, the rate of cell growth of the transfected cells was clearly reduced compared to that of wild-type C2C12 cells transfected with only the neomycin-resistant gene (C2-NEO). In addition, altered morphology with partial fusion was observed. Biochemically, an increase in creatine kinase activity accompanied by an increased rate of expression of the myogenic protein troponin T and the myogenic transcription factors myoD and myogenin was detected in clone 8 cells exposed to ZnCl2. Most importantly, an induction in the level of cyclin-dependent kinase inhibitor p21WAF1 and an increase in the level of the underphosphorylated active form of the tumor suppressor protein pRb concomitant with the down-regulation of cyclin D1 and c-myc were also evident in the transfected clones. These changes were similar to those observed in normal C2C12 cells cultivated in DM. We conclude that PKR is an important regulatory protein participating in the myogenic process.

Chromosome 2 sequence of the human malaria parasite Plasmodium falciparum

Chromosome 2 of Plasmodium falciparum was sequenced; this sequence contains 947,103 base pairs and encodes 210 predicted genes. In comparison with the Saccharomyces cerevisiae genome, chromosome 2 has a lower gene density, introns are more frequent, and proteins are markedly enriched in nonglobular domains. A family of surface proteins, rifins, that may play a role in antigenic variation was identified. The complete sequencing of chromosome 2 has shown that sequencing of the A+T-rich P. falciparum genome is technically feasible.

Complete genome sequence of Treponema pallidum, the syphilis spirochete

The complete genome sequence of Treponema pallidum was determined and shown to be 1,138,006 base pairs containing 1041 predicted coding sequences (open reading frames). Systems for DNA replication, transcription, translation, and repair are intact, but catabolic and biosynthetic activities are minimized. The number of identifiable transporters is small, and no phosphoenolpyruvate:phosphotransferase carbohydrate transporters were found. Potential virulence factors include a family of 12 potential membrane proteins and several putative hemolysins. Comparison of the T. pallidum genome sequence with that of another pathogenic spirochete, Borrelia burgdorferi, the agent of Lyme disease, identified unique and common genes and substantiates the considerable diversity observed among pathogenic spirochetes.

Herpes simplex virus proteins are damaged following photodynamic inactivation with phthalocyanines

The photodynamic inactivation of herpes simplex virus type 1 (HSV-1) by two phthalocyanines (Pcs), the cationic dye HOSi-PcOSi(CH3)2(CH2)3N+(CH3)3I-(Pc5) and the amphiphilic dye aluminum dibenzodisulfophthalocyanine hydroxide (AlN2SB2POH), has been compared with that by the anionic dye, Merocyanine 540 (Mc540). Both Pc derivatives demonstrate a remarkable virucidal activity upon light activation even 3 h after the onset of HSV-1 adsorption, while Mc540 is effective for only 30 min after adsorption. Since fusion and virus penetration are promoted by membrane glycoproteins, we have studied the damage to viral proteins following photodynamic treatment (PDT) of HSV-1 and its relation to inactivation. The effect of AlN2SB2POH PDT is assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Major changes are found in the protein profile of PDT-treated HSV-1. A reduced ability of specific antibodies to react with HSV-1 major envelope proteins is detected by employing the Western blot assay. In particular, we demonstrate the related changes of glycoprotein D (gD), a structural protein of the HSV envelope. Since the envelope proteins participate in viral entry into the host cell, these alterations to viral envelope proteins may impair their ability to participate in early events of viral entry, leading to reduced infectivity of HSV-1. In contrast, no significant changes in the proteins' electrophoretic mobility could be seen after PDT with Mc540 or with Pc5. When HSV-1 purified proteins are subjected to combined electrophoretic and electro osmotic forces on cellulose acetate, there is a shift in their cathode mobility, which may indicate changes in the protein mass and protein net charges following AlN2SB2POH photosensitization. There are only minor changes in the virus proteins, assayed as above, when HSV-1 is treated with Pc5.

Genomic sequence of a Lyme disease spirochaete, Borrelia burgdorferi

The genome of the bacterium Borrelia burgdorferi B31, the aetiologic agent of Lyme disease, contains a linear chromosome of 910,725 base pairs and at least 17 linear and circular plasmids with a combined size of more than 533,000 base pairs. The chromosome contains 853 genes encoding a basic set of proteins for DNA replication, transcription, translation, solute transport and energy metabolism, but, like Mycoplasma genitalium, it contains no genes for cellular biosynthetic reactions. Because B. burgdorferi and M. genitalium are distantly related eubacteria, we suggest that their limited metabolic capacities reflect convergent evolution by gene loss from more metabolically competent progenitors. Of 430 genes on 11 plasmids, most have no known biological function; 39% of plasmid genes are paralogues that form 47 gene families. The biological significance of the multiple plasmid-encoded genes is not clear, although they may be involved in antigenic variation or immune evasion.

Distinct sensitivity of normal and malignant cells to ultrasound in vitro

The effect of ultrasonic irradiation on the viability of human normal (foreskin fibroblast and amniotic fluid epithelial) and tumor (breast carcinoma, melanoma, and lung carcinoma) cells lines was studied. Cells were subjected to ultrasonic irradiation with a frequency of 20 kHz and an intensity of 0.33 W/cm2 for variable periods of time. Several parameters were tested to determine the effects of ultrasonic irradiation on cell viability and cellular function. Normal cells were relatively resistant to ultrasonic irradiation, whereas malignant cells were much more sensitive. Maximum damage occurred 4 min after exposure of the malignant cells to irradiation. Cellular DNA and protein synthesis were significantly affected as a function of time of irradiation and cloning efficiency of malignant cells exposed to irradiation was greatly reduced. To generalize the consistency of the ultrasonic effect, studies on additional normal and malignant human cells of distinct origin are under way to test their sensitivity to ultrasonic irradiation. Thus, the applicability of ultrasonic irradiation as an antitumor agent may be important in the development of a new methodology in the treatment of cancer.

Finding genes in DNA with a Hidden Markov Model

This study describes a new Hidden Markov Model (HMM) system for segmenting uncharacterized genomic DNA sequences into exons, introns, and intergenic regions. Separate HMM modules were designed and trained for specific regions of DNA: exons, introns, intergenic regions, and splice sites. The models were then tied together to form a biologically feasible topology. The integrated HMM was trained further on a set of eukaryotic DNA sequences and tested by using it to segment a separate set of sequences. The resulting HMM system which is called VEIL (Viterbi Exon-Intron Locator), obtains an overall accuracy on test data of 92% of total bases correctly labelled, with a correlation coefficient of 0.73. Using the more stringent test of exact exon prediction, VEIL correctly located both ends of 53% of the coding exons, and 49% of the exons it predicts are exactly correct. These results compare favorably to the best previous results for gene structure prediction and demonstrate the benefits of using HMMs for this problem.

Ectopic expression of 2-5A synthetase in myeloid cells induces growth arrest and facilitates the appearance of a myeloid differentiation marker

Two variants of the human myeloid leukemia cell line HL-60 were used to study the possible involvement of the IFN-induced protein 2-5A synthetase in cell growth arrest and differentiation. The two variants, HL-205 and HL-525, are equally susceptible to differentiation to the granulocyte lineage by exposure to DMSO, but only HL-205 cells acquire the macrophage phenotype following exposure to phorbol esters. The kinetics of 2-5A synthetase activity was established in both variants exposed to either DMSO or phorbol 12-myristate 13-acetate. With DMSO treatment, 2-5A synthetase activity was markedly induced in both variants, although with slightly different kinetics. With phorbol 12-myristate 13-acetate treatment, 2-5A enzymatic activity increased only in HL-205; no activity was detected up to 96 h after treatment in HL-525. The induction of 2-5A synthetase activity is apparently alpha/beta-IFN dependent, because only antibodies directed against a mixture of alpha- and beta-IFN completely abolished the increase in activity detected during differentiation of HL-205 cells. To directly establish the role of 2-5A synthetase in differentiation, HL-205 cells were transfected with an expression vector harboring the cDNA for the 43-kDa isoform of murine 2-5A synthetase fused to the inducible metallothionein promoter. Two clones, clone 6, which yielded a low level of 2-5A synthetase activity in response to ZnCl2 (which activates the promoter), and clone 7, which was a high responder, were further analyzed and compared with the control clone, neo. Reductions in the rates of cell growth and thymidine incorporation were observed with both clone 6 and clone 7 cells exposed to ZnCl2; clone 7 was more responsive. In addition, the level of c-myc-specific RNA transcript was greatly reduced in ZnCl2 or beta-IFN-treated clone 7 cells, whereas the neo cells responded similarly only after beta-IFN treatment. Treatment of clone-neo cells with beta-IFN resulted in conversion of pRb protein from the phosphorylated to the underphosphorylated form within 24 h; ZnCl2 had no effect, even after 72 h. In contrast, the accumulation of the underphosphorylated form of pRb was observed in clone 7 cells treated either with beta-IFN or ZnCl2. Finally, a significant increase in nitro blue tetrazolium-positive cells, an indication of differentiation, was evident with ZnCl2-treated clone 6 and clone 7 cells; no such increase was observed with clone-neo cells under similar conditions. We conclude that ectopic expression of 2-5A synthetase in HL-205 cells results in cell growth arrest and facilitates the appearance of a myeloid differentiation marker.

Inhibition of malignant cell proliferation by culture media conditioned by cardiac or skeletal muscle

The present work is an attempt to explain the high resistance of muscles to cancer development. We used primary cultures of rat skeletal and cardiac muscle, and examined the effect of the supernatant of these cultures (conditioned medium; CM) on proliferation of cancer cells. The results demonstrated that CM inhibited the proliferation of several types of malignant cells by more than 50%, without a significant inhibition on normal cells. Cell cycle analysis revealed that CM increased the number of cells in S and G2 phases, suggesting a cytostatic effect of CM. For defining the biological properties of the factor(s) which are present in the CM, skeletal muscle cultures were grown in chemically defined medium (serum free medium). The concentrated sample was applied to a Sephadex G-50 column and three fractions were obtained. Only one fraction showed inhibitory activity. Four protein bands were observed in this fraction, as revealed by SDS-PAGE. We suggest that some, or all of these proteins are responsible for inhibition of tumor cell replication.

Inhibition of 2-5A synthetase expression by antisense RNA interferes with interferon-mediated antiviral and antiproliferative effects and induces anchorage-independent cell growth

It has been shown previously that the IFN-induced enzyme 2-5A synthetase is sufficient to induce antiviral and antiproliferative effects in transfected cells expressing the protein. In this study, the possibility that this enzyme is also essential in generating these biological activities was investigated. For this purpose, a plasmid, pMSas-NEO, was constructed. This plasmid carries an active neomycin-resistant gene. In addition, it contains a metallothionein promoter fused to an inverted 180-bp fragment derived from the 5' end of cDNA encoding the 43-kDa isoform of murine 2-5A synthetase. NIH/3T3 mouse fibroblasts were transfected with the plasmid, about 50 neomycin-resistant clones were isolated, and two, clone 11 and clone 22, were chosen for further studies. One clone transfected only with the neomycin-resistant gene, clone Neo, was used as a control. The results show that in the case of clone 11, the combined treatment of IFN and ZnCl2 reduced significantly the level of the IFN-induced 2-5A synthetase activity, the amount of the 40-, 43-, and 71-kDa 2-5A synthetase isoforms and the level of the 1.7-kb specific RNA transcript. An even stronger effect on these parameters was observed with clone 22 cells. No difference in PKR activity was evident under the same conditions with all three clones tested. Most important, the combined treatment of IFN and ZnCl2 reversed the IFN-mediated antiproliferative and antiviral activities, as determined by the kinetics of cell growth, thymidine incorporation, cloning efficiency, and infection with mengovirus. Strikingly, the growth of colonies in soft agar were observed in both clone 11 (small colonies) and clone 22 (large colonies) cells, particularly following treatment with ZnCl2. We conclude that 2-5A synthetase is an essential component in the IFN-induced biological activities and that interference with its function results in anchorage-independent growth of the transfected cells.

Interferon-independent activation of (2′-5′) oligoadenylate synthetase in Friend erythroleukemia cell variants exposed to HMBA

To provide evidence for the implication of interferon (IFN)-induced proteins in the regulation of cell growth during differentiation, the activation of (2′-5′) oligoadenylate synthetase (2-5A synthetase) as well as of PKR, two IFN-induced proteins, during differentiation of Friend erythroleukemia cells, was studied. Two cell variants were used. The first (FL) was completely susceptible to hexamethylene bis-acetamide (HMBA)-treatment and responded in both growth-retardation and hemoglobin synthesis. The second (R1) failed to synthesize hemoglobin in response to HMBA although cell growth was still inhibited. In both cell variants, 2–5A synthetase enzyme activity was induced in a similar fashion, reaching a peak at 26 hours after treatment with HMBA. However, the down regulation of activity thereafter was not identical in both cases. In R1 cells, the reduction was much slower compared to FL cells. A similar pattern was observed with the appearance of the 43 kDa isoform of 2–5A synthetase in immunoblots. An analysis of 2–5A synthetase gene expression revealed the presence of 1.7 kb transcripts which peaked at 16 hours after HMBA-treatment in both cell variants. Again, the down-regulation in expression was slower in R1 than in FL cells. Addition of anti-murin alpha/beta-IFN antibodies did not reduce the level of either 2–5A synthetase expression or enzyme activity in either cell variant. Interestingly, the presence of antibodies also did not affect the pattern of pRb phosphorylation in the cell variants exposed to HMBA. In both cell variants, an increase in the amount of the phosphorylated form (ppRb) was observed in immunoblots after 4 hours. This form was gradually transformed to the underphosphorylated molecule (pRb) with time in culture, even in the presence of antibodies. This further substantiates the notion that IFN-induced regulation of pRb phosphorylation is mediated by IFN-induced proteins. The basal level of either expression or ezymatic activity of PKR detected in untreated FL or R1 cells, was relatively high. Treatment with HMBA did not result in further induction of PKR in either cell variant.

Interruption of myogenesis by transforming growth factor beta 1 or EGTA inhibits expression and activity of the myogenic-associated (2'-5') oligoadenylate synthetase and PKR

Interferon-induced proteins have been previously implicated in the regulation of cell growth. In an attempt to provide evidence for the involvement of these proteins in differentiation, the effect of transforming growth factor beta 1 (TGF-beta) and EGTA on the expression and activity of (2'-5') oligoadenylate synthetase (2-5A synthetase) and double-stranded RNA activated protein kinase (PKR) during myogenesis of rat primary skeletal muscle cultures or the myogenic cell line L8 was studied. Both TGF-beta and EGTA inhibited the fusion of myoblasts and reduced significantly the level of the muscle-specific proteins, acetylcholine receptors, and creatine kinase activity in rat primary muscle cultures. Likewise, TGF-beta exhibited a similar inhibitory effect on the fusion of L8 cells and the level of creatine kinase activity in these cells. The kinetics of 2-5A synthetase activity in both types of cells during differentiation was then established. In both types, a transient increase in activity was observed followed by a decrease thereafter. However, while the peak activity in primary muscle cultures appeared after 24 h in culture, it was observed only on the third day in L8 cells grown in differentiation medium (DM). Treatment of primary cultures with either TGF-beta or EGTA reduced the amount of 1.7-kb 2-5A synthetase-specific RNA transcripts and decreased significantly the level of 2-5A synthetase activity compared to that in untreated cultures. Western blot analysis of 2-5A synthetase proteins in untreated primary muscle cultures showed that the major species synthesized in these cells was the 43-kDa isoform of the enzyme. However, the 71-kDa isoform was clearly visible after 72 h in culture. Both TGF-beta and EGTA abrogated the appearance of all forms of 2-5A synthetase. Similarly, in L8 cells grown in DM, TGF-beta down-regulated the expression of 2-5A synthetase and reduced the level of enzymatic activity. Western blot analysis revealed the presence of the 71-kDa isoform as the major species of 2-5A synthetase in L8 cells; however, the 43-kDa isoform was also visible on the third day in DM. TGF-beta treatment resulted in a reduced amount of 2-5A synthetase proteins. The kinetics of PKR activity in L8 cells grown in DM was similar to that observed with 2-5A synthetase. Furthermore, TGF-beta strongly reduced the level of PKR activity in differentiating L8 cells.

Tyrosine phosphorylation of measles virus nucleocapsid protein in persistently infected neuroblastoma cells

Subacute sclerosing panencephalitis is a slowly progressing fatal human disease of the central nervous system which is a delayed sequel of measles virus (MV) infection. A typical pathological feature of this disease is the presence of viral ribonucleocapsid structures in the form of inclusion bodies and the absence of infectious virus or budding viral particles. The mechanisms governing the establishment and maintenance of a persistent MV infection in brain cells are still largely unknown. To understand the mechanisms underlying MV persistence in neuronal cells, a tissue culture model was studied. Clone NS20Y/MS of the murine neuroblastoma C1300 persistently infected with the wild-type Edmonston strain of MV secretes relatively high levels of alpha/beta interferon (IFN). As shown previously, treatment of the persistently infected cultures with anti-IFN serum converted the persistent state into a productive infection indicated by the appearance of multinucleated giant cells. In this study, we have investigated whether alpha/beta IFN produced by NS20Y/MS cells activates cellular protein tyrosine kinases which will induce tyrosine phosphorylating activity specific to virus-infected cells. We present data to show augmented protein tyrosine kinase activity in the persistently infected cells. We demonstrate that the MV N protein is phosphorylated on tyrosine in addition to serine and threonine in the persistent state but not in NS20Y cells acutely infected with MV.

Locating protein coding regions in human DNA using a decision tree algorithm

Genes in eukaryotic DNA cover hundreds or thousands of base pairs, while the regions of those genes that code for proteins may occupy only a small percentage of the sequence. Identifying the coding regions is of vital importance in understanding these genes. Many recent research efforts have studied computational methods for distinguishing between coding and noncoding regions, and several promising results have been reported. We describe here a new approach, using a machine learning system that builds decision trees from the data. This approach combines several coding measures to produce classifiers with consistently higher accuracies than previous methods, on DNA sequences ranging from 54 to 162 base pairs in length. The algorithm is very efficient, and it can easily be adapted to different sequence lengths. Our conclusion is that decision trees are a highly effective tool for identifying protein coding regions.

A System for Induction of Oblique Decision Trees

This article describes a new system for induction ofoblique decision trees. This system, OC1, combines deterministic hill-climbing with two forms of randomization to find a goodoblique split (in the form of a hyperplane) at each node of a decisiontree. Oblique decision tree methods are tuned especially for domains in which the attributes are numeric, although they can be adapted to symbolic or mixed symbolic/numeric attributes. We presentextensive empirical studies, using both real and artificial data, thatanalyze OC1's ability to construct oblique trees that are smaller and more accurate than their axis-parallel counterparts. We also examinethe benefits of randomization for the construction of oblique decisiontrees.

Hemoglobin is a late event in the differentiation of Friend erythroleukemic cells in-vitro. I. The role of interferon-induced proteins

Here we report that the interferon (IFN)-induced proteins, 2'-5'-oligoadenylate synthetase (OAS) and IFN-induced protein kinase (PKI), appearance and activity precede that of hemoglobin (Hb) in the differentiation process of Friend erythroleukemic cells (FLC). Since our results are correlative, we assume that OAS and PKI are activated, and act at an early stage in the differentiation process, enabling the late onset of Hb synthesis. It is, thus, suggested that red blood cells harboring specific differentiating genes may be used as more efficient carriers of oxygen-binding molecules.

Photodynamic inactivation of herpes viruses with phthalocyanine derivatives

The antiviral photosensitization capacity of 11 different phthalocyanine (Pc) derivatives was examined using herpes simplex virus-1, herpes simplex virus-2 and varicella zoster virus in the search for the most potent sensitizers for viral decontamination of blood. The kinetics of viral photoinactivation were resolved during the stages of viral adsorption and penetration into the host cells. The capacity of Pc in the photodynamic inactivation of viruses was compared with that of merocyanine 540 (MC540), another widely studied photosensitizer. Sensitivity to photoinactivation decreased progressively with time after addition of viruses to their host cells. The viruses were most sensitive to photodynamic inactivation up to 30 min from the initiation of adsorption. Cell-associated viruses, 45-60 min after the onset of adsorption, are highly resistant to photodynamic treatment by most photosensitizers, with the exception of amphiphilic Pc derivatives. Thus the mixed sulfonated Pc-naphthalocyanine derivatives AlNSB3P and AlN2SB2P demonstrated a remarkable decontamination activity even 60 min after the onset of adsorption. Ultrastructural examination of these photosensitized viruses demonstrated damage to the viral envelope which prevented viral adsorption and/or penetration. The non-enveloped adenovirus was found to be resistant to all the dyes tested.

Collapse of K+ and ionic balance during photodynamic inactivation of leukemic cells, erythrocytes and Staphylococcus aureus

1. The immediate and fast ionic fluxes in Friend erythroleukemic cells (FELC), erythrocytes and Staphylococcus aureus during short intervals of porphyrin mediated photosensitization were determined uniquely by X-ray microanalysis (XRMA) combined with electron microscopy. 2. Photodynamic inactivation of FELC was mediated by either endogenous protoporphyrin induced by 5-amino levulinic acid (5-ALA), or Photofrin-II. We describe the predominant phenomena of > 85% K-loss within 2-10 min of photoactivation. However the accompanied Na inflow and the collapse of the cellular balance of elemental-composition were inconsistent and acted as a function of cell damage. 3. Erythrocytes treated with hematoporphyrin (HP) lost most of their intracellular K yet instantly gained Na. Nevertheless the K/Na molar ratio of the control erythrocytes was nearly 12/1 while after photosensitization and K loss it changed to 1/1. 4. The S. aureus bacteria photosensitized with HP showed entire K-loss as well as marked Na efflux which increased with irradiation time; this was accompanied by the decline of other cell elements. 5. The prevailing K loss in FELC, erythrocytes and bacteria during the first minutes of photosensitization is deduced to be an immediate primary consequence of the photodynamic effect, while other ionic changes are joined in order with the development of cellular damage.

Infection with Moloney murine sarcoma virus inhibits myogenesis and alters the myogenic-associated (2'-5')oligoadenylate synthetase expression and activity

Infection of rat skeletal muscle cultures on the first or second day in vitro with Moloney murine sarcoma virus (MSV) led to the arrest of myotube formation and to inhibition of both the synthesis of the muscle-specific proteins acetylcholine receptors and creatine kinase and the expression of the myosin light chain-2. Mos-specific RNA transcripts were readily detected at 1 day after infection indicating that viral genes were expressed in infected cells. In parallel, the expression of the cell growth-associated gene--c-myc--in uninfected muscle cultures was drastically reduced with time, while in MSV-infected myoblasts, the amount of c-myc-specific RNA transcripts gradually increased with time after infection. Under these conditions we could demonstrate that the interferon-induced gene (2'-5')oligoadenylate synthetase (2-5A synthetase) was transiently activated in uninfected muscle culture reaching a peak activity on the third day. Infection of myoblasts with murine leukemia virus did not alter the pattern of 2-5 synthetase activity observed in uninfected cells. However, infection with MSV on the second day led to a slight reduction in activity followed by a significant increase on the sixth and seventh day. Similarly, 2-5A synthetase gene expression was down-regulated with time in culture in uninfected myoblasts while re-expressed between the fourth and seventh days in MSV-infected cultures.

The response of normal and malignant cells to ultrasound in vitro

The effect of ultrasonic irradiation on the viability of normal and tumor cell cultures derived from human and mouse origins was investigated. The cells were irradiated with a frequency of 2 MHz and intensity of 0.33 W/cm2, up to 4 min and immediately tested for cell viability using four different parameters: vital staining for the determination of the rate of cell growth; [3H]-thymidine and [3H]-leucine incorporation as an indication of the rate of DNA and protein synthesis respectively; and cloning efficiency as a measurement of the cell ability to multiply. Two human normal cell lines used in our studies, FS11 foreskin fibroblasts and Wish cells, were relatively resistant to ultrasonic irradiation effect although the growth rate of the latter was somewhat affected, particularly after 2 or 4 min of irradiation. However, cells derived from either malignant melanoma or breast carcinoma were highly sensitive to irradiation as demonstrated by a reduction of 96% and 65%, respectively, in cloning efficiency even after irradiation for 1 min. A third tumor cell line derived from lung carcinoma was more resistant. Two normal clones derived from NIH/3T3 mouse fibroblasts were used. These clones revealed some degree of sensitivity, particularly after 4 min of irradiation. However, their murine-sarcoma-virus transformed counterparts were found to be even more sensitive at identical times of ultrasonic irradiation, although the differences are not as striking as demonstrated with cells from human origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Predicting protein secondary structure with a nearest-neighbor algorithm

We have developed a new method for protein secondary structure prediction that achieves accuracies as high as 71.0%, the highest value yet reported. The main component of our method is a nearest-neighbor algorithm that uses a more sophisticated treatment of the feature space than standard nearest-neighbor methods. It calculates distance tables that allow it to produce real-valued distances between amino acid residues, and attaches weights to the instances to further modify the the structure of feature space. The algorithm, which is closely related to the memory-based reasoning method of Zhang et al., is simple and easy to train, and has also been applied with excellent results to the problem of identifying DNA promoter sequences.

Persistent measles virus infection enhances major histocompatibility complex class I expression and immunogenicity of murine neuroblastoma cells

The effect of persistent measles virus infection on the expression of major histocompatibility complex (MHC) class I antigens was studied. Mouse neuroblastoma cells C1300, clone NS20Y, were persistently infected with the Edmonston strain of measles virus. The persistently infected cell line, NS20Y/MS, expressed augmented levels of both H-2Kk and H-2Dd MHC class I glycoproteins. Activation of two interferon(IFN)-induced enzymes, known to be part of the IFN system: (2'-5')oligoadenylate synthetase and double-stranded-RNA-activated protein kinase, was detected. Measles-virus-infected cells elicited cytotoxic T lymphocytes that recognized and lysed virus-infected and uninfected neuroblastoma cells in an H-2-restricted fashion. Furthermore, immunization of mice with persistently infected cells conferred resistance to tumor growth after challenge with the highly malignant NS20Y cells. The rationale for using measles virus for immunotherapy is that most patients develop lifelong immunity after recovery or vaccination from this infection. Patients developing cancer are likely to have memory cells. A secondary response induced by measles-virus-infected cells may therefore induce an efficient immune response against non-infected tumour cells.

Biological effects of photoactivated-HPD and cholesteryl hemisuccinate on erythroid differentiation

In order to establish the ability of porphyrins to distinguish between differentiated and undifferentiated cells of the erythropoietic pathway, the cytotoxic effects of hematoporphyrin derivative (HPD) on Friend erythroleukemic cells (FLC) were derivative (HPD) on Friend erythroleukemic cells (FLC) were studied. Since cholesterol affects the fluidity of cell membranes, the inhibitory effect of cholesteryl hemisuccinate (CHS) on HPD was similarly tested. FLC were induced with either dimethyl sulfoxide (DMSO), hemin, or both. The cells responded to DMSO-treatment by the synthesis of a large amount of hemoglobin and a decrease in both the cell volume and rate of cell-growth. Hemin, on the other hand, did not drive FLC to synthesize hemoglobin and reduced only moderately the growth rate compared to untreated cultures. The combined effect of DMSO and hemin led to a profound inhibition of the growth rate, but did not increase the synthesis of hemoglobin compared to the level observed in cells treated with DMSO only. The binding property of HPD to FLC was also determined. DMSO-treatment significantly reduced the amount of HPD-binding, and combined treatment with DMSO and hemin resulted in even a lower level of HPD-binding. On the other hand, induced as well as non-induced cells showed the same sensitivity to photoactivated HPD when both DNA and protein synthesis were examined. Pretreatment of both differentiated and undifferentiated cells with CHS reduced the cytotoxicity of photoactivated HPD to the same level. We conclude that the decreased binding of HPD to differentiated cells is a result of a reduction in their cell volume. Thus, the differentiation process per se does not protect cells against the photodynamic effect of HPD. Moreover, CHS may act as a scavenger or first acceptor of singlet oxygen blocking the photodynamic effect.